Synthesis, Characterization and Application of Hydrazide...

78

Synthesis, Characterization and Application of

Hydrazide Modified Amino Resins

RASHID SALEEM

REGISTRATION NO. 0093-PhD-CHEM-2010

SESSION 2010-2013

DEPARTMENT OF CHEMISTRY

GOVERNMENT COLLEGE UNIVERSITY,

79

LAHORE

Synthesis, Characterization and Application of

Hydrazide Modified Amino Resins

Submitted to Government College University Lahore

In partial fulfillment of the requirements

For the award of degree of

DOCTOR OF PHILOSOPHY

IN

CHEMISTRY

BY

RASHID SALEEM

REGISTRATION NO. 0093-PhD-CHEM-2010

SESSION 2010-2013

DEPARTMENT OF CHEMISTRY

80

GOVERNMENT COLLEGE UNIVERSITY,

LAHORE

RESEARCH COMPLETION CERTIFICATE

Certified that the research work contained in this thesis entitled “Synthesis, Characterization

and Application of Hydrazide Modified Amino Resins” has been carried out and completed

by Mr. Rashid Saleem, Registration No.0093-PhD-CHEM-2010 under my supervision during

his PhD (CHEMISTRY) in the laboratories of the Department of Chemistry, Government

College University, Lahore.

Dated: ____________

Supervisor Co-supervisor

__________________ __________________

Dr. Fahim Ashraf Qureshi Dr. Ahmad Adnan

General Manager Professor

ORIC, COMSATS Department of Chemistry

Institute of Information Technology,

Islamabad, Pakistan

Former Assistant Professor

Department of Chemistry

GC University Lahore

Submitted through

_______________________

Prof. Dr. Ahmad Adnan

Chairperson

Department of Chemistry

G. C. University, Lahore

G. C. University, Lahore ______________

81

Controller of Examination

Government College University, Lahore

D E C L A R A T I O N

I, Rashid Saleem, Registration No. 0093-PhD-CHEM-2010, student of Ph.D in the subject of

Chemistry session 2010-2013, hereby declared that the matter printed in the thesis entitled

“Synthesis, Characterization and Application of Hydrazide Modified Amino Resins” is

my own work and has not been printed, published and submitted as research work, thesis or

publication in any form in any University, Research Institution etc. in Pakistan or abroad.

__________________

Signature of Deponent

Dated: ________________

A C K N O W L E D G E M E N T

All praises for the most merciful, omnipotent, omnipresent and omniscient Almighty

ALLAH, Who enabled me with the blessing of His Prophet Hazrat Muhammad (P.B.U.H),

Whose teachings inspired me to wider my thoughts and deliberate the things deeply and to

complete this dissertation.

I am obliged to pay my heart rendering thanks and gratitude to my respected Supervisor

Dr. Fahim Ashraf Qureshi, General Manager, ORIC, COMSAT of Technology, Islamabad,

Pakistan and Dr. Ahmad Adnan, Chairperson, Department of Chemistry, GC University, Lahore,

82

whose unremitting concentration, determination, hardworking, enthusiastic, highly courteous

behavior, scholastic guidance, dedicated attitude, continuous help, congruent encouragement,

valuable suggestions, inexhaustible inspiration and kindness in planning and execution of the

present research projects and completion of the dissertation.

I also feel great pleasure in expressing my heartiest obligation and thanks to all respected

teachers of the Chemistry Department, G.C. University Lahore for their continuous sport and

encouragement during the whole session.

I am very much thankful to Mr. Abrar Ahmad, Chief Executive officer of SRC PVT Ltd

Lahore Pakistan, Mr. Muhammad Faheem, Chief Operation Officer SRC PVT Ltd Lahore

Pakistan, for providing their company resources for my research work.

I would like to express my sincere appreciation and thanks to all my colleagues and friends

especially Mr. Ghullam Hussain, Mr. Naveed Ashraf, Mr. Abdul Rauf, Dr. Muhammad Riaz, Dr.

Muhammad Hanif, Mr. Muhammad Idrees, Ms. Samia Saddiqu, Mr. Umair, Mr. Hafiz Abdul

Basit, Mr. Sajjad Ahmad and all my fellows for their support, encouragement and help to pursue

this work. I am thankful to all non-teaching staff of the Department who helped me in the

completion of my research work.

I would like to express my heartiest gratitude to my brother, sisters and caring wife along

with my daughters and sons for their prayers, encouragements, and invaluable co-operation; never

could I return their love and sacrifices. I owe them most of my life and my love for them will

always be closed to my heart.

In the end, my special regards to my Beloved Father (Mr. Muhammad Saleem) and prayers for

my Mother, whose non-lasting prayers are the beacon of life and without Them I am nothing in

this world. I have no words to acknowledge their moral support, continuous encouragement and

sincere prayers that boosted me to accomplish my goal during my studies. I am fortunate enough

to have wonderful parents to share and feel what I have never courage to express to others or to

face alone.

83

RASHID SALEEM

84

DEDICATION

This piece of work is dedicated with Allah’s blessings by virtue of Whom I have

been able to complete my thesis, to my father who sacrificed his well being for my

prosperity, and most precious for me in this world, my mother who always guided

me on right path, whose prayers are always a source of light in every dark moment

of my life. May God bless them with good health and long life!

Ameen

85

List of Publications

Rashid Saleem, Ahmad Adnan, Muhammad Riaz, Muhammad Hanif and Fahim Ashraf

Qureshi: Study of Retanning Behavior of Sulfonated Succinic Dihydrazide Formaldehyde

Condensates Under Different Reactant Conditions, Asian Journal of Chemistry; Vol. 25,

No. 17 (2013), 9829-9834

Impact Factor 0.266

Rashid Saleem, Ahmad Adnan and Fahim Ashraf Qureshi: Study of viscosity behavior

and retanning properties of sulfonated glutaric dihydrazide formaldehyde condensate

under different reactant ratios, Russian Journal of Applied Chemistry, 2013, Vol. 86, No.

11, pp. 1798−1804. © Pleiades Publishing, Ltd., 2013.

Impact Factor 0.24

Rashid Saleem, Ahmad Adnan, Muhammad Hanif, Muhammad Saleem, Ki-Hwan Lee and

Fahim Ashraf Qureshi: Synthesis and application of sulfonated adipic dihdyrazide

formaldehyde based resins under different molar ratios as effective leather retanning

agents, Iranian Polymer Journal January 2014, Volume 23, Issue 1, pp 69-78

Impact Factor 1.469

Rashid Saleem, Ahmad Adnan, Fahim Ashraf Qureshi and Muhammad Riaz: Study of

viscosity behavior and Retanning Properties of Isophthalic Dihydrazide Based Amino

Resins under Different Reactant Conditions, Society of Leather technologists and Chemists

Vol. 97, September – October 2013, page 211-219.

Impact Factor 0.65

Rashid Saleem, Ahmad Adnan and Fahim Ashraf Qureshi: Synthesis and Application of

ECO Friendly Amino Resins for Retanning of Leather under Different Conditions,

Society of Leather technologists and Chemists, vol. 99, January – February 2015, pages

8-15.

Impact Factor 0.65

Rashid Saleem, Ahmad Adnan and Fahim Ashraf Qureshi: Synthesis and Application of

Formaldehyde Free Melamine Glutaraldehyde Amino Resin As An Effective Retanning

Agent, Indian Journal of Chemical Technology, Accepted for publication

86

Impact Factor 0.58

7

CONTENTS

CHAPTER 1

INTRODUCTION 1

1.1 History 1

1.2 Raw materials 2

1.2.1 Melamine 3

1.2.2 Urea 3

1.2.3 Formaldehyde 3

1.2.4 Other materials 4

1.3 Chemistry of resin formation 4

1.4 Application of amino resins 8

1.4.1 Laminating resins 8

1.4.2 Molding compounds 8

1.4.3 Coatings 8

1.4.4 Textile finishes 10

1.4.4.1 Ethylene urea resins 10

1.4.4.2 Propylene urea resins 11

1.4.4.3 Triazone 11

1.4.4.4 Urone resins 11

87

1.4.4.5 Glyoxal resins 12

1.4.4.6 Melamine formaldehyde resins 12

1.4.4.7 Miscellaneous resins 13

1.4.5 Tire cord 13

1.4.6 Amino resins in paper industry 14

1.5 Regulatory concerns 16

1.6 Tanning chemistry 17

1.6.1 Pretanning, tanning and retanning agents 17

1.6.1.1 Mineral tanning agents 17

1.6.1.2 Vegetable tanning 18

1.6.1.3 Syntan 19

1.6.1.4 Aldehydes 21

1.6.1.5 Polymers and resins 21

1.6.2 Tanning mechanism 21

CHAPTER 2

LITERATURE REVIEW 24

2.1 Low/free formaldehyde amino resins 24

2.2 Stability of amino resins 26

2.3 Structure elucidation 27

2.4 Application of amino resins 29 CHAPTER 3

EXPERIMENTAL WORK 34

88

3.1 Chemicals used in the study 35

3.2 Synthesis of sulfonated succinic dihdyrazide formaldehyde condensates 35

3.2.1 Mechanism for the synthesis of succinic dihydrazide formaldehyde condensate 37

3.2.1.1 Methylolation of succinic dihydrazide 37

3.2.1.2 Sulfonation of dimethylol succinic dihydrazide 37

3.2.1.3 Acidic pH condensation 38

3.2.1.4 Basic pH condensation 39

3.3 Synthesis of sulfonated glutaric dihydrazide formaldehyde resin 40

3.3.1 Mechanism for the synthesis of glutaric dihydrazide formaldehyde condensate 41

3.3.1.1 Methylolation 41

3.3.1.2 Sulfonation 42

3.3.1.3 Condensation of monomers 43

3.4 Synthesis of sulfonated adipic dihydrazide formaldehyde resin 44

3.4.1 Mechanism for the synthesis of adipic dihydrazide formaldehyde condensate 45




3.5 Synthesis of sulfonated isophthalic dihydrazide formaldehyde resin 47

3.5.1 Mechanism for the synthesis of isophthalic dihydrazide formaldehyde condensate 48


89



3.6 Synthesis of sulfonated terephthalic dihydrazide formaldehyde condensates 51

3.6.1 Mechanism for the synthesis of isophthalic dihydrazide formaldehyde condensate 52




3.7 Synthesis of sulfonated melamine glyoxylated resin 55

3.7.1 Mechanism for the synthesis of melamine glyoxylated resin 56

3.7.1.1 Glyoxylation 56


3.7.1.3 Condensation 58

3.8 Preparation of sulfonated melamine glutaraldehyde based resin 59

3.8.1 Mechanism for the synthesis of melamine glutaraldehyde resin 60



3.8.1.3 Condensation 62

3.9 Physical characterization of resins 63

3.9.1 Estimation of solid content 63

3.9.2 Viscosity determination 63

90

3.9.3 Sepcific gravity 64

3.9.4 Determination of color and pH of liquid resins 64

3.9.5 Determination of solubility and acid sensitivity 64

3.9.6 Free formaldehyde in the synthetic resin 64

3.10 Chemical characterization of resins 65

3.10.1 Fourier transform infra-red spectroscopy (FT-IR) 65

3.10.2 Nuclear magnetic resonance (NMR) spectroscopy 65

3.11 Viscosity average molecular weight 65

3.12 Application of resins as retanning agents 67

3.13 Mechanical properties of retanned leather 68

3.13.1 Conditioning of leather before testing 68

3.13.2 Determination of tensile strength 68

3.13.3 Determination of percentage elongation at break 71

3.13.4 Determination of tear strength 71

3.13.5 Determination of grain strength 72

3.13.6 Organoleptic properties 72

3.13.7 Free formaldehyde analysis in leather 73

3.13.8 Scanning electron microscopic analysis 77

3.13.9 Thermal analysis 77

CHAPTER 4

91

RESULTS AND DISCUSSION 78

4.1 Physical properties of novel hydrazide modified amino resins and formaldehyde

78 free amino resins

4.2 Chemical characterization of novel amino resins and formaldehyde free amino

84 resins

4.2.1 Chemical characterization of SDH series 84

4.2.2 Chemical characterization of GDH series 88

4.2.3 Chemical characterization of ADH series 91

4.2.4 Chemical characterization of ISPDH series 94

4.2.5 Chemical characterization of TPDH series 97

4.2.6 Chemical characterization of MGO resin series 100

4.2.7 Chemical characterization of MGT resin series 104

4.3 Molecular weight of resins 107

4.3.1 Molecular weight of SDH Series 107

4.3.2 Molecular weight of GDH Series 112

4.3.3 Molecular weight of ADH Series 118

4.3.4 Molecular weight of ISPDH Series 124

4.3.5 Molecular weight of TPDH Series 129

4.3.6 Molecular weight of MGO Series 134

4.3.7 Molecular weight of MGT Series 140

4.4 Evaluation of retanning performance 146

92

4.4.1 Retanning performance of succinic dihdyrazide formaldehyde condensates 146

4.4.2 Retanning performance of glutaric dihdyrazide formaldehyde condensates 149

4.4.3 Retanning performance of adipic dihdyrazide formaldehyde condensates 151

4.4.4 Retanning performance of isophthalic dihdyrazide formaldehyde condensates 154

4.4.5 Retanning performance of terephthalic dihdyrazide formaldehyde condensates 158

4.4.6 Retanning performance of melamine glyoxylated condensates 162

4.4.7 Retanning performance of melamine glutaraldehyde condensates 166

4.5 Organoletpic properties 168

4.5.1 Organoleptic properties of SDH Series 169

4.5.2 Organoleptic properties of GDH Series 170

4.5.3 Organoleptic properties of ADH Series 171

4.5.4 Organoleptic properties of ISPDH Series 172

4.5.5 Organoleptic properties of TPDH Series 173

4.5.6 Organoleptic properties of MGO Series 175

4.5.7 Organoleptic properties of MGT Series 176

4.6 Comparative thermal analysis 178

4.6.1 Comparative thermal analysis of optimized resins 178

4.6.2 Study of curing behavior of optimized resins 179

4.6.3 Comparative thermal analysis of control leather and optimized experimental leather 180

4.7 Scanning electron microscopy 182

CONCLUSION

184

CHAPTER 5

REFERENCES 187

ANNEXES 199

Table # List of Tables Page

#

Table 1.1 Urea formaldehyde (U/F) - reaction rate constants 6

Table 1.2 Composition for regular MF3 & high efficiency (HE) colloid resins 15

93

Table 1.3 A comparison of general pickle and basification pHs for chromium and zirconium

tanning processes

18

Table 1.4 Tanning agents and characteristic shrinkage temperature ranges 22

Table 1.5 The four tannage zones based on shrinkage temperature 23

Table 3.1 List of chemicals 35

Table 3.2 Experimental data of succinic dihydrazide formaldehyde condensates 36

Table 3.3 Experimental data of glutaric dihydrazide formaldehyde condensates 41

Table 3.4 Experimental data of adipic dihydrazide formaldehyde condensates 44

Table 3.5 Experimental data of isophthalic dihydrazide formaldehyde condensates 47

Table 3.6 Experimental data of terephthalic dihydrazide formaldehyde condensates 51

Table 3.7 Experimental data of melamine glyoxylated condensates 55

Table 3.8 Experimental data of melamine glutaraldehyde condensates 59

Table 3.9 Post-tanning recipe for processing wet blue 67

Table 3.10 standard atmosphere and tolerances 68

Table 3.11 Dimensions of test specimens 69

Table 4.1 Physical characteristics of succinc dihydrazide formaldehyde condensates 78

Table 4.2 Physical characteristics of glutaric dihydrazide formaldehyde condensates 79

Table 4.3 Physical characteristics of adipic dihydrazide formaldehyde condensates 80

Table 4.4 Physical characteristics of isophthalic dihydrazide formaldehyde condensates 81

Table 4.5 Physical characteristics of terephthalic dihydrazide formaldehyde condensates 82

Table 4.6 Physical characteristics of melamine glyoxylated condensates 83

Table 4.7 Physical characteristics of melamine glutaraldehdye condensates 84

Table 4.8 Dependence of the flow time, relative viscosity, specific viscosity, ∆ = ŋsp lnŋr

and ∆/c2 on the concentration of the sample SDH # 02

108

Table 4.9 Dependence of the concentration of sample (SDH # 03, SDH # 04, SDH # 06, SDH

# 07, SDH # 08, SDH # 11, SDH # 12, SDH # 15 and SDH # 16) on ∆/c2

109

Table 4.10 Dependence of molecular weight of SDH samples on monomers ratios 110

94

Table 4.11 Dependence of the flow time, relative viscosity, specific viscosity, ∆ = ŋsp lnŋr

and ∆/c2 on the concentration of the sample GDH # 01

113

Table 4.12 Dependence of the concentration of sample (GDH # 02, GDH # 03, GDH # 04,

GDH # 05, GDH # 08, GDH # 09, GDH # 10, GDH # 13, GDH # 14,

GDH # 15) on ∆/c2

114

Table 4.13 Viscosity and molecular weight of resins of GDH Series 115

Table 4.14 Dependence of the flow time, relative viscosity, specific viscosity, ∆ = ŋsp – lnŋr

and ∆/c2 on the concentration of the sample ADH # 01

119

Table 4.15 Dependence of the concentration of sample (ADH # 02, ADH # 03, ADH #

04, ADH # 05, ADH # 06, ADH # 07, ADH # 08, ADH # 09, ADH # 10,

ADH # 11, ADH # 12, ADH # 13, ADH # 14, ADH # 15) on ∆/c2

120

Table 4.16 Viscosity and molecular weight of resins of ADH Series with different mole ratios

of monomers

122


and ∆/c2 on the concentration of the sample ISPDH # 04

125

Table 4.18 Dependence of the concentration of sample (ISPDH # 05, ISPDH # 06,

ISPDH # 07, ISPDH # 13, ISPDH # 14, ISPDH # 22, ISPDH # 23, ISPDH #

24, ISPDH # 32, ISPDH # 33, ISPDH # 34) on ∆/c2

126

Table 4.19 Viscosity and molecular weight of resins of ISPDH Series with different mole

ratios of monomers

127

Table 4.20 Dependence of the flow time, relative viscosity, specific viscosity, ∆ = ŋsp - 130

lnŋr and ∆/c2 on the concentration of the sample TPDH

# 04

Table 4.21 Dependence of the concentration of sample (TPDH # 05, TPDH # 06, TPDH

# 14, TPDH # 22, TPDH # 23, TPDH # 24, TPDH # 33 and TPDH # 34) on

∆/c2

131

Table 4.22 Viscosity and molecular weight of resins of TPDH series with different mole ratios

of monomers

132

95


and ∆/c2 on the concentration of the sample MGO Resin # 03

135

Table 4.24 Dependence of the concentration of sample (MGO Resin # 04, MGO Resin #

05, MGO Resin # 06, MGO Resin # 09, MGO Resin # 10, MGO Resin # 11,

MGO Resin # 12, MGO Resin # 13, MGO Resin # 14, MGO Resin # 15,




MGO Resin # 28, MGO Resin # 29, MGO Resin # 30) on ∆/c2

136

Table 4.25 Viscosity and molecular weight of resins of TPDH series with different mole ratios

of monomers

138


and ∆/c2 on the concentration of the sample MGT Resin # 03

140

Table 4.27 Dependence of the concentration of sample (MGT Resin # 04, MGT Resin #

05, MGT Resin # 06, MGT Resin # 09, MGT Resin # 10, MGT Resin # 11,

MGT Resin # 12, MGT Resin # 15, MGT Resin # 16, MGT Resin # 17, MGT

Resin # 18, MGT Resin # 20, MGT Resin # 21, MGT Resin # 22, MGT Resin #

23 and MGT Resin # 24) on ∆/c2

142

Table 4.28 Viscosity and molecular weight of resins of MGT Series with different mole ratios

of monomers

144

Table 4.29 Effect of synthesized SDH resins on mechanical properties of leather 147

Table 4.30 Effect of synthesized GDH resins on mechanical properties of leather 149

Table 4.31 Effect of synthesized ADH resins on mechanical properties of leather 152

Table 4.32 Effect of synthesized ISPDH resins on mechanical properties of leather 155

Table 4.33 Effect of synthesized TPDH resins on mechanical properties of leather 159

Table 4.34 Effect of synthesized MGO resins on mechanical properties of leather 163

Table 4.35 Effect of synthesized MGT resins on mechanical properties of leather 166

Table 4.36 Organoleptic properties of control and experimental retanned leathers 169

96







Table 4.43 Curing parameters for optimized resins at heating rate of 10oC/min 180

Figure # LIST OF FIGURES

Page

#

Figure 1.1 Effect of pH on (A) addition reaction of formaldehyde and urea (1:1) 6

Figure 4.1 Dependence of ∆/c2 on the concentration of the sample SDH # 02. 108

Figure 4.2 Dependence of ∆/c2 on the concentration of the samples SDH # 02, SDH #

03, SDH # 04, SDH # 06, SDH # 07, SDH # 08, SDH # 11, SDH # 12, SDH # 15

and SDH # 16.

109

Figure 4.3 Molecular weight of SDH resin samples 110

Figure 4.4 Molecular weight of SDH resin samples versus viscosity (cps) 111

Figure 4.5 Viscosity variation with various S/SDH and F/SDH mole ratio 112

Figure 4.6 Dependence of ∆/c2 on the concentration of the sample GDH # 01. 113

Figure 4.7 Dependence of ∆/c2 on the concentration of the samples GDH # 02, GDH #

03, GDH # 04, GDH # 05, GDH # 08, GDH # 09, GDH # 10, GDH # 13, GDH

# 14, GDH # 15.

114

Figure 4.8 Molecular weight of GDH resin samples 116

Figure 4.9 Molecular weight of SDH resin samples versus viscosity (cps) 117

Figure 4.10 Viscosity variation with S/GDH and F/GDH mole ratio. 118

Figure 4.11 Dependence of ∆/c2 on the concentration of the sample GDH # 01. 119

Figure 4.12 Dependence of ∆/c2 on the concentration of the samples ADH #01, ADH #

97

02, ADH # 03, ADH # 04, ADH # 05, ADH # 06, ADH # 07, ADH # 08, ADH

# 09, ADH # 10, ADH # 11, ADH # 12, ADH # 13, ADH # 14, ADH # 15.

121

Figure 4.13 Molecular weight of resins of ADH series 123

Figure 4.14 Correlation of viscosity average molecular weight with viscosity (cps) 123

Figure 4.15 Viscosity variation of ADH resins with varying S/ADH and F/ADH mole ratio. 124

Figure 4.16 Dependence of ∆/c2 on the concentration of the sample ISPDH # 04. 125

Figure 4.17 Dependence of ∆/c2 on the concentration of the samples ISPDH # 04, ISPDH

# 05, ISPDH # 06, ISPDH # 07, ISPDH # 13, ISPDH # 14, ISPDH # 22,

ISPDH # 23, ISPDH # 24, ISPDH # 32, ISPDH # 33, ISPDH # 34

126

Figure 4.18 Molecular weight of resins of ISPDH series 128


Figure 4.20 Viscosity variation of ISPDH resins with varying S/ISPDH and F/ISPDH mole

ratio. 129

Figure 4.21 Dependence of ∆/c2 on the concentration of the sample TPDH # 04. 130

Figure 4.22 Dependence of ∆/c2 on the concentration of the samples TPDH # 04, TPDH #

05, TPDH # 06, TPDH # 14, TPDH # 22, TPDH # 23, TPDH # 24, TPDH # 33

and TPDH # 34

131

Figure 4.23 Molecular weight of resins of TPDH series 132


Figure 4.25 Viscosity variation of TPDH resins with varying S/TPDH and F/TPDH mole ratio. 134

Figure 4.26 Dependence of ∆/c2 on the concentration of the sample MGO Resin # 03. 135

Figure 4.27 Dependence of ∆/c2 on the concentration of the samples MGO Resin # 03,



MGO Resin # 14, MGO Resin # 15, MGO Resin # 16, MGO Resin # 17, MGO

Resin # 18, MGO Resin # 19, MGO Resin # 20, MGO Resin # 21,

137

98

MGO Resin # 22, MGO Resin # 23, MGO Resin # 24, MGO Resin # 25, MGO

Resin # 26, MGO Resin # 27, MGO Resin # 28, MGO Resin # 29, MGO Resin

# 30

Figure 4.28 Molecular weight of resins of MGO series 139


Figure 4.30 Dependence of ∆/c2 on the concentration of the sample MGT Resin # 03. 141

Figure 4.31 Dependence of ∆/c2 on the concentration of the samples MGT Resin # 03,

MGT Resin # 04, MGT Resin # 05, MGT Resin # 06, MGT Resin # 09, MGT

Resin # 10, MGT Resin # 11, MGT Resin # 12, MGT Resin # 15, MGT Resin

# 16, MGT Resin # 17, MGT Resin # 18, MGT Resin # 20, MGT Resin # 21,

MGT Resin # 22, MGT Resin # 23 and MGT Resin # 24

143

Figure 4.32 Molecular weight of resins of MGT series 145


Figure 4.34 Physical assessment of leather; (a) Effect of SDH resins on tensile strength of

leather fibers parallel to backbone; (b) Effect of SDH resins on tear strength of

leather fibers parallel to backbone; (c) Effect of SDH resins on %

Elongation of leather parallel to backbone;(d) Effect of SDH resins on Tensile

strength of leather fibers perpendicular to backbone;(e) Effect of SDH resins on

Tear strength of leather fibers perpendicular to backbone;(f) Effect of SDH

resins on % Elongation of leather perpendicular to backbone.

148

Figure 4.35 Physical assessment of leather; (a) Effect of GDH resins on tensile strength of

leather fibers parallel to backbone; (b) Effect of GDH resins on tensile strength

of leather fibers perpendicular to backbone; (c) Effect of GDH resins

on tear strength of leather fibers parallel to backbone; (d) Effect of GDH resins

on tear strength of leather fibers perpendicular to backbone; (e) Effect of GDH

resins on % elongation of leather parallel to backbone; (f) Effect of GDH resins

on % elongation perpendicular to backbone; (g) Effect of GDH resins on grain

cracking

151

99

Figure 4.36 Physical characteristics of re-tanned leather, (a) Effect of polymer on tensile

strength perpendicular to backbone; (b) Effect of polymer on % Elongation

perpendicular to backbone; (c) Effect of polymer on tensile strength parallel

to backbone; (d) Effect of polymer on % Elongation parallel to backbone; (e)

Effect of polymer on tear strength parallel to backbone; (f) Effect of ADH

polymers on tear strength perpendicular to backbone; (g) Effect of ADH

polymers on distension at grain cracking of the leather

153

Figure 4.37 Physical characteristics of re-tanned leather, (a) Effect of ISPDH resins on

tear strength of the leather fibers parallel to backbone; (b) Effect of ISPDH

resins on tear strength of the leather fibers perpendicular to backbone; (c)

Effect of ISPDH resins on distension at ball burst; (d) Effect of ISPDH

resins on tensile strength of the leather fibers parallel to backbone; (e) Effect of

ISPDH resins on % Elongation of the leather fibers parallel to backbone;

(f) Effect of ISPDH resins on tensile strength of the leather fibers

perpendicular to backbone; (g) Effect of ISPDH resins on % Elongation of the

leather fibers perpendicular to backbone

157

Figure 4.38 Physical characteristics of re-tanned leather; (a) Effect of TPDH resins on

tensile strength of leather fibers parallel to backbone; (b) Effect of TPDH resins

on % Elongation of leather fibers parallel to backbone; (c) Effect of

TPDH resins on tear strength of leather fibers parallel to backbone;

(d) Effect of TPDH resins on tensile strength of leather fibers perpendicular to

backbone; (e) Effect of TPDH resins on % Elongation of leather fibers

perpendicular to backbone; (f) Effect of TPDH resins on tear strength of leather

fibers perpendicular to backbone

161

Figure 4.39 Physical characteristics of re-tanned leather; (a) Effect of MGO Resins on

tensile strength of leather fibers perpendicular to backbone; (b) Effect of MGO

Resins on % Elongation of leather fibers perpendicular to backbone;

(c) Effect of MGO Resins on tensile strength of leather fibers parallel to

100

backbone; (d) Effect of MGO Resins on % Elongation of leather fibers parallel

to backbone; (e) Effect of MGO Resins on tear strength of leather fibers

perpendicular to backbone; (f) Effect of MGO Resins on tear strength

of leather fibers parallel to backbone; (g) Effect of MGO Resins on Distension

at burst of the leather fibers

165

Figure 4.40 Physical characteristics of re-tanned leather; (a) Effect of MGT Resins on tensile 168

Figure 4.41 Comparison of organoleptic properties of SDH resin series 170

Figure 4.42 Comparison of organoleptic properties of GDH resin series 171

Figure 4.43 Comparison of organoleptic properties of ADH resin series 172

Figure 4.44 Comparison of organoleptic properties of ISPDH resin series 173

Figure 4.45 Comparison of organoleptic properties of TPDH resin series 174

Figure 4.46 Comparison of organoleptic properties of MGO resin series 176

Figure 4.47 Comparison of organoleptic properties of MGT GT resin series 177

Figure 4.48 Comparative thermal analysis of optimized resins 178

Figure 4.49 Comparative DSC analysis of optimized resins 179

Figure 4.50 Comparative thermal analysis of leather retanned with optimized resins 180

Figure 4.51 Scanning electron micrographs of fiber structure cross section (X500) and grain

structure (X50) 183

Figure 4.52 FTIR spectrum of optimized SDH Resin # 03 199

Figure 4.53 Figure 4.53: H 1 NMR spectrum of optimized SDH resin # 03 200

Figure 4.54 FTIR spectrum of optimized GDH resin # 09 201

Figure 4.55 H 1 NMR spectrum of optimized GDH resin # 09 202

Figure 4.56 FTIR spectrum of optimized ADH resin # 02 203

Figure 4.57 H 1 NMR spectrum of optimized ADH resin # 02 204

Figure 4.58 FTIR spectrum of optimized ISPDH resin # 06 205

Figure 4.59 H 1 NMR spectrum of optimized ISPDH resin # 06 206

Figure 4.60 FTIR spectrum of optimized TPDH resin # 05 207

Figure 4.61 H 1 NMR spectrum of optimized TPDH resin # 05 208

Figure 4.62 FTIR spectrum of optimized MGO resin # 24 209

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Figure 4.63 H 1 NMR spectrum of optimized MGO resin # 24 210

Figure 4.64 FTIR spectrum of optimized MGT resin # 12 211

Figure 4.65 H 1 NMR spectrum of optimized MGT resin # 12 212

CHAPTER-1

INTRODUCTION Amino resins are thermally setting resins which are formed by reacting an aldehyde with

an amino functional group containing compound. Urea formaldehyde (UF) resins account for

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about eighty percent of the amino resins, melamine formaldehyde (MF) resins accounts for the

remaining. Other amino and aldehyde compounds are used to a minor extent.

First commercially important amino resin appeared in 1930. The most important

attractions of amino resins are water miscibility before setting that allows for their simple

application. Due to being colorless, unlimited colorability with pigments and dyes can be achieved.

In addition to excellent resistance to solvents in cured state, abrasion resistance, outstanding

hardness and good resistance to heat. However, release of formalin during curing is the limitation

of amino resins. Repeated exposure of dry and wet conditions produce cracks in the surface of the

finished product.

Amino resins are also used as functional additives for modifying the final properties of the

materials. Dacron Polyester made racing sailboat have also been treated with amino resin for

strengthening purpose [9]. Amino resins are used to improve wet strength of processed paper.

Amino resins based molding compounds are used for bottle, jar caps, buttons and molded

dinnerware.

1.1Historical background In 1908, chemistry of the amino resins has been explored [10], but a molding compound,

first commercial product, was patented in 1925 in England [11]. It was formulated from equimolar

ratio of thiourea and urea. American Cyanamid Company got the patent rights along with Beetle

trademark.

In the near beginning of 1920s, experimentation was worked out with urea formaldehyde

resins in Austria [12, 13] and Germany [14] that lead to discovery that urea formaldehyde

condensates can be molded into beautiful transparent sheet which was proposed as organic glass

[13,14].

Melamine based resins had similar properties with urea formaldehyde resins but with

superior qualities. A patent was issued in 1936 [15] by a German company Henkel. Melamine

based resins supplanted rapidly urea based condensates and were being used in bond formulations,

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lamination, molding, as well as paper and textile finishings. Aminoplasts and other thermosetting

plastics are processed in an injection molding equipment[16].

1.2Basic raw materials Amino resins are formed by condensing formaldehyde with urea1 or melamine2.

Although formaldehyde can condense with other different amides and amines to form

valuable products. For example, Benzoguanamine3 is used to produce amino resins for coating

purpose because it imparts good resistance against surfactants, an advantage for washing machines

coatings. Dihydroxyethylene urea4based amino resins possess wash and wear properties for

clothing. Glycoluril5 resins provide flexibility to coatings.

1.2.1Melamine

It is a crystalline white solid, with melting point 350oC along with vaporization having

slight solubility in water. The commercially available recrystallized grade is pure upto

99%.Melamine was commercially produced first from dicyandiamide while now it is produced by

urea, a cheaper and cost effective raw material [17–20].

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1.2.2 Urea

It is an important raw material for amino resins because urea formaldehyde (UF) resin is

the bulk selling amino resin, and urea is also the raw material for melamine, the compound used

in the next largest bulk selling type of the amino resin.

1.2.3Formaldehyde

Formaldehyde is very reactive, pungent, colorless gas. Formaldehyde is handled either as

aqueous or alcoholic solution or in solid polymeric form, paraformaldehyde [21]. Solutions form

of Formaldehyde in methanol, isobutyl alcohol and n-butanol is marketed with trade name

“Formcel”, which are frequently utilized for producing alcoholic modified melamine and urea

resins for treating textile coatings.

The stabilized form can be placed at normal conditions without forming precipitates of

solid paraformaldehyde polymer because it constitutes methanol contents (5-10%). The

uninhibited form of formaldehyde must be maintained to store at a temperature of minimum at

32◦C to avoid the settling of paraformaldehyde polymer. Formalin solutions stabilized by urea are

also used for stabilization [22], and different other stabilizers like hexamine and ethanol amines

have been introduced [23, 24].

Paraformaldehyde is available commercially as a white powder or in flake form with purity

level up to 91-95%.Paraformaldehyde is an unstable polymer that produces formaldehyde easily

in solution. The chains depolymerize under alkaline media from ends, whereas in acidic media the

chains are arbitrarily broken [25].

1.2.4Other materials

Acetoguanamine and benzoguanamine can be used as a substitute for melamine to obtain

high solubility in the organic solvents and for excellent chemical resistance. Toluene sulfonamide

and aniline also react with formaldehyde to produce thermosetting resins. Acrylamide is an

interesting monomer; vinyl group is reactive in catalyzed free radical addition polymerizations,

while amino group is reactive in condensation with formalin. For example, acrylamide forms

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Nmethylolacrylamide by reacting readily with formaldehyde, which reacts with isobutyl alcohol

to give corresponding product as in reaction no. 1.

This product is easily miscible in many organic solvents & is co-polymerizable with

different vinyl monomers producing reactive groups on main polymer backbone [26].

1.3Basic chemistry of resin synthesis The first step is the nucleophilic addition reaction of formaldehyde with amino compound

to generate hydroxymethylated group, known as hydroxymethylation or methylolation as in

reaction no. 2.

Condensation reaction is a second step of joining together of the monomers with

elimination of water molecule to produce an oligomer, a polymeric chain, or a wide network. This

is called resinification or simply curing and has been demonstrated in the following reaction no.3.

Success in making and utilizing amino resins on large scale depends on the precise and

efficient control of two basic chemical reactions. For this reason, the chemical reactions have been

studied much more [27-38].

Making and utilizing thermosetting resins on large scale depends on precise and efficient

control of methylolation and resinification. For that reason, the chemical processes have been

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studied in detail [27-38]. In the first step, the addition of formalin to amino functional compound

is progressed either in the presence of bases or acids, although, this reaction takes place over wide

pH range. In the second step, amino groups join by methylene bridges and are catalyzed by the

acids only. Their reaction kinetics has been observed in a wide pH range [36], presented in Figure

1.1.

Figure 1.1: Effect of pH on (i) reaction of formaldehyde and urea (1:1) (ii) reaction of

methylolurea with hydrogen of second neighboring urea molecule. Temperature= 35oC In table

1.1, Rate constants of these reactions at 35◦C have been shown.

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Table 1.1: Urea formaldehyde - Reaction rate

constants

Under alkaline or neutral conditions, the methylol compounds are relatively stable

produced by these reactions, undergo further condensation, to produce polymeric compounds in

acidic media.

Formaldehyde and amino functional compound are combined and they develop a stable

resinous material that can be used as an adhesive material or as a molding compound through

addition of fillers. The acidic material is added in the second step to speed up the reaction by

heating to cure the amino resin into a solid cross-linked mass. In this process, the methylolated

group is portonated (reaction no.4) and a water molecule is eliminated producing the carbonium

ion as an intermediate (reaction no.5).The intermediate forms a methylene link by reacting with

another amino group as in reaction no. 6 and 7.

.

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Some other reactions are also involved for the production of amino plastics. Two

methylolated groups may be combined to form a bridge of dimethylene ether while liberating a

water molecule as in reaction no. 8.

Such formed bridge of dimethylene ether is unstable as compared to the bridge of diamino

methylene and may be rearranged to make a methylene link by liberation of a formaldehyde

molecule (reaction no. 9).

The hydroxymethyl compounds with lower molecular weight formed from melamine and

urea are miscible in water and appropriate for molding compounds, adhesive manufacturing, and

some kinds of resins used for textile treatment. The alkyl group substitution to hydrogen of the

methylol group renders the resin solubility character in organic solvents and increase stability.

Acids can also be used to catalyze these reactions and to minimize the side self-

condensation reactions; process is usually carried out with excess alcohol. After completion of

reaction, acid catalyst is neutralized and excess alcohol is stripped or may be left as solvent for the

synthesized resin. A very typical example, in which urea and formalin are mixed and passed

through a multiple stage unit. pH and temperature are monitored at every stage to obtain suitable

degree of polymerization. The final product is adjusted 60-65% solids by continuous evaporation

[39].

1.4Application of amino resins 1.4.1Laminating resins

Melamine based laminating resins used for saturating the printed and overlay paper of

decorative laminate contain equimolar ratio of formalin to melamine. The crystallization of

methylolated melamines is inhibited by completing the reaction upto the stages, where one fourth

of the resin has been shifted into low molecular weight condensate.

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1.4.2Molding compounds

Amino resin used for molding compound is made by two moles of formaldehyde, one mole

of the melamine react in slightly alkaline media with temperature at 60oC. The reaction is

continued till polymeric compounds have been developed to prevent the crystallization of

methylolated melamine on cooling. When proper reaction of the resin has been approached, amino

resin is shifted to a dough mixer and mixed with pulp of alpha cellulose. The mixing ratio is one

part of the alpha cellulose and three parts of amino resin solids. The wet spongy mass formed is

spread on the trays where alpha cellulose is mixed with it in a temperature controlled oven to form

hard popcorn like brittle intermediate. This brittle material may be pulverized to coarse powder,

and is sent for storage. Molding materials are formed by combining cellulose and melamine based

resin intermediate with a reactive catalyst, colorants, stabilizer and molding lubricants in a grinding

ball mill [40].

1.4.3Coatings

As the cured resins are too brittle to be used in surface coatings for wood substrate or metal,

they are used in blending with different film forming resins (polyesters, alkyds, epoxies, acrylics)

for a range of desirable characteristics. The coating formulations have ability to cure at high

temperatures, which makes them suited for industrial coatings. The content of amino resin in these

formulations typically ranges from 10-50% on the basis of total binder solids. During curing, resins

react with nucleophilic sites (carboxyl, hydroxyl and amide) on the other film developers in the

composition but also have tendency to self-condense to some extent. Highly alkylated resins have

very low tendency to condense by self. [41, 42] and therefore are effective crosslinking agents.

However, they need addition of acid catalyst strong enough to obtain desirable curing even at

baking temperatures of 120oC- 177oC.

Butylated urea formaldehyde amino resin to be used in fast curing formulations for baking

enamels are synthesized beginning with 1 mole of urea, 1.50 mole of butanol and 2.12 mole of

paraformaldehyde. Alkaline pH is adjusted by Triethanolamine and mixture is heated to reflux till

paraformaldehyde is dissolved. pH is adjusted to 4 with phthallic anhydride and water is

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azeotropically distilled out until temperature of batch reaches 117oC; cooling is applied and desired

solid content of the formulation is achieved by dilution [43].

Highly methylated amino resin based on melamine formaldehyde with poor cross-linking

and no self-condensation behavior might be synthesized as follows [44]. Formaldehyde in methyl

alcohol is loaded to reaction vessel and pH is stabilized to9.0-9.5 by using 0.1N sodium hydroxide

solution. Melamine is charged to give mole ratio of the melamine to formaldehyde 1:6.5 and

mixture is refluxed for about 1.5 hour. The reaction is then cooled to 35oC, excess methanol is

charged to bring the molar ratio of methyl alcohol per melamine mole up to 11.With temperature

batch at 35oC, pH is adjusted to 1 with enough sulfuric acid. After keeping reaction at 35oC with

pH 1 for one hour, neutralization is carried out with 0.5N sodium hydroxide solution and stripped

off extra methanol to get a syrupy product with 60% concentration of melamine resin, which is

filtered for clarification. Such type of highly methylated resin may be used in solvent type or water

based coatings [45].

1.4.4Textile finishes

Amino resins which are used for finishing of textile are methylolated forms of melamine

or urea. These resins are generally in oligomeric forms and may contain some polymeric forms.

Physical properties of cellulosic fibers are changed after treating with amino resins. Amino resins

don’t react with synthesized fibers such as polyester and nylon but condense by self on the surface.

As a result, stiffness and resiliency properties of fibers are changed. Partially polymerized forms

of resins with molecular weight that are not permeating amorphous portion of the cellulose also

have tendency to increase the resiliency or stiffness of cellulosic fibers.

1.4.4.1 Ethylene urea resins

During 1950s and 1960s, mostly widely used types of resins were based on dimethylol

ethylene urea, which were generally known as ethylene urea resins. Urea, formaldehyde and

ethylenediamine are used to prepare ethylene urea resin. 2-Imidazolidinone8was first synthesized

by reacting excess ethylenediamine and urea at 116oC in an aqueous medium (reaction no. 10)

[46].

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A fractionating column is used to remove ammonia byproduct and recycle

ethylenediamine. The product was in molten form (mp 133◦C), which was fed into ice cooled water

to make solution which was methylolated with formalin (37%) to form dimethylol ethyleneurea9

(reaction no. 11).

The above is generally 50% resinous solution, has good shelf life with stability to

polymerization and hydrolysis

1.4.4.2 Propylene urea resins

Likeethyleneurea8 product, dimethylol propyleneurea10 is the base for propylene urea based

formaldehyde resin. Urea, formaldehyde and 1.3-diaminopropane are used to prepare resin

(reaction no. 12).

1.4.4.3 Triazone

It is common name for compounds that are dimethylol derivatives of the tetrahydro-5-

alkyl-striazone11. Urea, primary aliphatic amine and formaldehyde are used to make the

compound. Varieties of amines can be used to make six member rings [47]. Monoethanolamine

(hydroxylethylamine) is used to overcome odor. Methylol urea’s with straight chains have no

adverse effects on finished fabric. Triazones are generally produced (reaction no. 13) with less

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stoichiometric amount of the amine as compared to formalin. This produces not only economical

resin but with improved efficiency [48].

1.4.4.4 Uron resins

The term uron resin in the textile industry generally refers to the mixture of relatively less amount

of melamine formaldehyde resin, which is N,N- bis(methoxymethyl)uron12 plus 15% to 25% urea

formaldehyde resins in methylated form, a byproduct.N,N-bis(methoxymethyl)uron which was

first isolated (reaction no. 14) and reported in 1936 [49]. Four moles of formaldehyde and one

mole of urea react together at 60oC in highly alkaline conditions to make tetramethylol urea13 [50].

Under reduced pressure, water is removed to increase concentration, excess amount of methanol

is added and reaction is progressed under acidic media at room temperature to close ring structure

and methylation of hydroxymethyl functional groups. Precipitated salts are removed by filtration,

and excess methanol is recovered to concentrate the product. 70-80% pure product is combined

with methylated form of melamine formaldehyde resin to minimize tear strength losses of fabric

in the presence of chlorine, and further diluted upto 55-70% solids with water. As greater amount

of formalin is released from the fabric after treatment with uron resins, there use is discouraged.

1.4.4.5 Glyoxal resins

Glyoxal based resins have dominated since late 1960 in textile finish market for using as

wash, wear, durable press, and wrinkle recovery agents. These are 1,3- bis(hydroxymethyl)-4,

5dihydroxy -2-imidazolidinone, which is commonly known as dimethylol dihydroxyethylene

urea(DMEDHEU)14. Various methods for synthesis of glyoxal resins have been reported in

literature [51]. Commercially, DMDHEU can be synthesized cheaply with good purity through

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one vessel process (reaction no. 15) [52]. Equimolar urea and glyoxal as 40% strength solution

and two moles of formalin are loaded in the reaction vessel. Solution pH is maintained at7.5 -9.0

and mixture is heated to 65- 70oC. This reaction is almost stoichiometric; and thus there is no need

of excess reagent.

1.4.4.6 Melamine formaldehyde resins

These are most versatile textile finishing resins. They give wash and wear characteristics

to cellulosic materials and increase wash durability of the flame retardant finishes. Butanol

etherified melamine formaldehyde resins are used in the surface coatings, and printing ink

formulations for textile.

Melamine formaldehyde resin used in textile typically is dimethylether of trimethylol

melamine, which is prepared by reacting one mole of melamine and three moles of formaldehyde

at temperature of 95oC (reaction no. 16). As water interferes with methylation, methylation is

performed in methanol with powder paraformaldehyde and adjusting pH to 3.5 with continuous

heating. After completion of alkylation, acidic pH is readjusted upto 8.5-10 and extra methanol is

recovered under vacuum. The final resulting syrup has 85%solid contents.

1.4.4.7 Miscellaneous resins

Methylol carbamates are much less important as compared to urea and melamine

formaldehyde. They are synthesized from urea and alcohol [53-56] (reaction no. 17), so they are

derivatives of urea.

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1.4.5Tire cord

Amino resins are also utilized for improving adhesion of the rubber in tires to reinforce

cord. Textile cord is coated normally with the vinylpyridine styrene- butadiene latex dip solution

of rubber also having resorcinol formaldehyde resin. This dip coating is cured before using. The

coated dip increase adhesion of the textile cord to the rubber. Further improvements in adhesion

are achieved by adding hexa (methoxymethyl)melamine and resorcinol to rubber compound, that

have a contact with the textile cord. Resorcinol and Hexa (methoxymethyl)melamine (HMMM)

resin crosslink during vulcanization of rubber and are cured to form cross-linked polymer in rubber

matrix, giving strength and reinforcement to the rubber to increase its adhesion to textile cord.

Steel cord coated with brass is widely used for reinforcement in tires. Bead wire and steel belts are

general applications. Resorcinol and HMMM resins are utilized in the rubber compound having

contact with the steel cord for reinforcing the rubber and increase adhesion of steel cord to rubber.

Melamine resins usage of this type is described in patent literature [57].

1.4.6Amino resins in paper industry

The paper sheet integrity depends on hydrogen bonding formed between the fine cellulosic

structures during press and drying processes. The hydrogen bonds formed between hydroxyl

groups of the neighboring fibers are very strong when the paper is dry, but on wetting, the bonds

are severely weakened. Bonding between the hydroxyls of cellulosic fiber and water molecules is

as energetic process in the bonding between two cellulosic hydroxyls. As a result, untreated paper

loses its tear strength mostly when it is in wet form or exposed to humid conditions. Tear and

tensile strength, bursting and stiffness of the paper are also lost, when in contact with water or in

humid conditions.

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Over the years, many chemicals have been used to overcome this wet strength weakness.

If water could be prevented from penetrating the sites of the bonding by coating or sizing the sheet,

then wet strength may be obtained. Molecules of water are so little and so hydrophilic and coating

and sizing affords temporary protection only. Formaldehyde, polyethylenimine, glyoxal and

recently derivatized starch [58] and slightly cationic polyacrylamide based resins [59] have been

in use to give temporary wet strength to paper.

Formaldehyde and glyoxal are used on the formed paper, but other chemicals are reactive

to fiber and may be used as additives for wet end. Locust bean gum/borax and carboxymethyl

cellulose/calcium chloride are examples of double component systems, separately applied on paper

that have limited use before the use and emergence of amino resins. There are three major types

of wet strength resins which are in use today in paper making: polyamide/polyamine based resins

cross-linked by epichlorohydrin [60-65] that are used for neutral to slightly alkaline papers,

polyacrylamide resins in cationic form cross-linked by glyoxal that are in use for acidic to neutral

papers, and amino resins based on melamine are used for acidic papers.

Table: 1.2: Composition for regular MF3 &high

efficiency (HE) colloid resins Materials Regular MF3 HE MF8

Water, 20±10oC, kg 412 330.8

HCl, 20o Be, kg (1.16g/mL), kg 17.7 14.1

Formaldehyde, 37%, kg 0 84.8

Trimethylolmelamine, kg 45.4 45.4

Total 475.1 475.1

Composition for MF3 and High Efficiency colloids has been described in Table 1.2 [66].

Materials are loaded in order as enlisted, to500L tank with good ventilation and agitation. Fumes

of formaldehyde are emitted even from regular colloid. After aging, colloids are developed and

fresh solutions are not effective for wet strength efficiency. Stability of the colloids depends on

concentration and temperature. Colloids with 10to 12% contents are more stable for up to one

week at ambient temperature. By dilution after aging properly, stability of colloids can be

extended.

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Regular and High Efficiency colloids both increase the wet strength of the paper by

promoting adhesion between paper fibers; while strength of the individual fiber is not affected

individually. [67]. Resin improves adhesion between the fibers in dry or wet conditions, by

creating bonds that are not affected by water. Excess available formaldehyde in High Efficiency

colloids do perform by increasing its amount in the colloidal solution [66].

Input of additional formaldehyde increases amount in bound form of formaldehyde within

the colloid. When High Efficiency colloid is stored at lower concentration up to 0.05%, extra

formaldehyde bounded in the colloid is lost behaving as regular colloid. In past, urea formaldehyde

based resins are used as wet strength additives, were anionic in nature, formed by reacting urea

formaldehyde resin with sodium bisulfite. [68]. Nonionic urea formaldehyde resins have been

attempted but were not successful, because neutral charged resin made it nonreactive with fiber

resulting in lack of the retention. Sulfomethylated group is introduced by reacting with sodium

bisulfite that imparts polymers strong anionic character, but the reactivity is lowered to unbleached

kraft pulp. Alum use as a mordant was important since resin and fiber both were anionic. Urea

formaldehyde reaction with bisulfite is may be expressed as reaction no. 18

Cationic urea formaldehyde condensates were introduced in 1945, and quickly replaced

anionic form of resins, because they were compatible with all types of pulp forms [69]. They have

become now commodities, as alkaline and neutral papermaking process continues, their use has

been declining steadily in the industry. They are made commonly by the reaction of formaldehyde

and urea with one or more types of polyethylene polyamines. Structure of such type of resins is

complex and still not determined. During the reaction, ammonia gas is produced as per reaction

no. 19.

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Formalin is reactive with active hydrogen on both amine and urea and therefore polymer i s

a highly cross-linked. The type and amount of polyamine (10 to 15%), amount of the formaldehyde

(2-4 moles/1 mole of urea) and concentration of resin are variable and many methods have been

patented throughout world. Usually urea, polyamine, water and formaldehyde react at 85to 100oC.

Two steps are involved in the reaction, methylolation under basic pH, following by condensation

upto desired degree under acidic pH, whole of the reaction can be performed in acidic conditions

[70]. The product with 25-35% active contents in syrup form is stable for up to three months.

TAPPI monograph [71-72] provides a source of

information on economic and technical sides of wet strength.

1.5Regulatory concerns Melamine and urea formaldehyde resins are with low toxicity. In resinous state, amino

resin possess some free form of formaldehyde that can be disagreeable with environmental

legislations. Uncured resins however have nasty tastes that even discourage trace amount to be

ingested. Approaches have been reported for achieving low levels of formaldehyde in resins [73,

74].Molded forms of plastic or cured amino resin on paper or textiles may be nontoxic. Thermal

decomposition or combustion of cross-linked resins can produce toxic gases, like hydrogen

cyanide, formaldehyde and oxides of nitrogen.

1.6. Tanning chemistry Collagen is comparatively inert to biological and chemical attack but to enhance both the

mechanical strength and ability to resist putrification, hides are processed to stabilize by tanning

agents. [75]

1.6.1. Pretanning, tanning and retanning agents

The physical characteristics of leather is mainly dependent on the type of tanning agent,

quantity of tannins fixed, drying methods, and other parameters such as the application of oils, fats

and retanning agents. Tanning agents, who are used in pretanning step of leather manufacturing,

are different from those tanning agents that are used in the main tannage of leather manufacturing.

Pretanning operation may be performed to (i) decrease astringency of the main tanning agent for

collagen, e.g., in vegetable based tannages, (ii) to enhance the shrinkage temperature so that the

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leather is not damaged during the process of shaving or in degreasing step, during which higher

temperature upto 60°C can easily be reached, and (iii) to form a stable material for short term

preservation [76-78].

1.6.1.1. Mineral tanning agents

Mineral tanning agents are basically inorganic in nature and generally involve the

interaction of metal ions with the collagen. These include chromium, zirconium, [79], [80]

titanium, [81], [82] aluminium, [83] iron [84], [85] and some of the novel rare earth metals, usually

in the form of basic sulfates and silicates. The initial fixation of mineral tanning agent is by

coordination bond with carboxylate group of collagen triple helix. Bound water in the collagen is

displaced and metals form bridging or aggregate complexes that stabilize the skin structure

resulting in increasing the shrinkage temperature. The respective chemistries of each element will

determine the extent of penetration into the collagen and its fixation. Mineral salts dictate their

own pickle and basification pH during their processing. (Table 1.3).

Table 1.3: A comparison of general pickle and

basification pHs for chromium and zirconium tanning

processes. [83] Tanning Agent Pickle pH Basification pH

Basic Zirconium Sulfate 1.0-2.0 2.0-4.0

Basic Chromium Sulfate 2.5-3.0 3.8-4.2

Masking agents may be used to assist in the penetration of the metal cations [86].

They partially stabilize tanning salts by making a tanning complex with lower astringency

(surface reactive behavior) to collagen and less sensitivity to pH variations [87]. This behavior

allows masking agents to manipulate pickling and basification pHs. The masking agents also

contribute their own properties to leather and improve others, such as increased shrinkage

temperature, fullness, smoothness, grain pattern, fullness, modification of handle, bleaching of

leather color and improving distribution of tanning agents. Masking agents are anions with

different affinities for metal ions, e.g., nitrate < chloride < sulfate < sulfite <formate< acetate

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<sulfophthalate< succinate < tartrate < glycolate < phthalate < sulfosalicylate < malonate < lactate

< citrate <oxalate < hydroxide show increasing trend for complex affinity with the chromium,

where each anion can displace the one existing before it. Masked tanning complex can be stabilized

to a degree on reaching a limiting value where it has no affinity for collagen.

[88]

1.6.1.2. Vegetable tannins

Vegetable tannins are leached out from different parts of plant such as leaves, bark, nuts

and wood. They consist of large size, generally acidic, polyphenolic compounds with molecular

masses ranges from 500 to 20 000 g.mol-1 which make several hydrogen bonds with the collagen's

side chains and the peptide backbone[89].Vegetable tannins are used as the main tannage and

normally as retanning agents. There are two types of vegetable tannins such as hydrolysable16, 17

and condensed18.

Hydrolysable tannins may hydrolyze and are formed from esters of gallic acid, known as

gallotannins (e.g., Tara and Sumach) [90], or possess modified hexa hydroxydiphenic acid (ellagic

acid), known as ellagitannins (e.g., Valonea, Chestnut, Divi Divi and, Myrabolams) [91].

Condensed tannins are found widely and possess complex forms of leucoanthocyanidins, examples

are Quebracho and Mimosa. All the vegetable tannins have astringent behavior which can be

reduced by sulfitation along with increasing solubility to improve penetration.

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1.6.1.3. Syntan

Syntans or "Synthetic tannins" are tanning agents that are synthesized including resins,

aldehydes and polymers. Conventionally, there are four types of syntans which include auxiliary,

combination, replacement and mineral syntans.

Auxiliary syntans are produced from aromatic sulfonic acids and they assist processes such

as the tanning and dyeing (as dispersing agents), while with little to no inherent ability for tanning

[92].

Replacement syntans are phenolic in nature and replace originally vegetable tannins.[93]

Replacement may be employed as a sole tannage or as a pretanning and leather retanning agents

[94-95]. Replacement syntans are produced by polymierizing monomers using formaldehyde to

produce methylene condensed resinous compound although further linkages are also used to

increase light fastness in the following order

- CHR- < -CH2NHCONHCH2- < -CR2- < CO2- < -SO2NH-

Combination syntans are produced by blending or polymerization of aromatic and phenolic

sulphonic acid monomers to form multiple structures with hybrid properties. Solubility and

penetration of Syntans are improved by sulfitation, and are therefore anionic in character. The

ionizable sulfonic group of syntan has great ionic attraction for cationic amino groups of the

collagen side chains, whereas the phenolic moiety of the syntans bind similarly to the vegetable

tannins, i.e., by hydrogen bonds [96].

121

Mineral syntans are produced by two main methods: (i) by blending synthetic tanning

agents and mineral, where conventional masking occurs in the situ form, and (ii) by forming a

complex of cation-syntan with hybrid properties, where "masking" may be considered on

permanent basis and a new, neutral or anionic, syntans can be produced [97].In this method,

tanning agents may be synthesized with variable, color, penetration power, astringency, and filling

properties.

1.6.1.4. Aldehydes

The aldehyde functionality reacts with nonionized amino side chain of collagen and forms

covalent bonds. The aldehyde based tanning chemicals are formaldehyde, dialdehyde starches,

glutaraldehyde, [98], [99]and oxazolidines. Without lubrication of leather, aldehyde tannages yield

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thin and hard leathers. Glutaraldehyde is most versatile and used widely, especially in upholstery

leathers for automotive. Oxazolidines are derived from heterocyclic compounds, obtained by the

reaction of aldehydes with aminohydroxy compounds but their functionality remain aldehydic and

are alternatives for true aldehyde21 [100-101].

1.6.1.5. Polymers and resins

Polyurethanes, Acrylics, and amino resins (urea, melamine and dicyandiamide [102-105]

formaldehyde condensates) are included in this large and distinct group. They are all used as

leather retanning agents. They have very little to no affect on shrinkage temperature of leather.

Polymer deposits improve cutting yields because of selective filling of open structured parts of

skins and hides and resulting in tightening of the grain.

1.6.2. Tanning mechanisms

It has been accepted that collagen of leather is stabilised by the hydrogen bonding and

shrinkage of collagen after heating is due to breaking of hydrogen bonds [106]. Miles and Bailey

[107

]have shown that shrinking occurs in the hydroxyproline areas of the collagen structural

chain which supports the suggestion of Weir and Carter [108] that shrinking initiate at a "shrinking

nucleus." The shrinkage temperatures are characteristic of each tannage (Table 1.4).

Tanning process modifies at least one of the essential characteristics of collagen. According

to Tony Covington [112], tanning may affect: (a) making the collagen non-putrescible, (b)

modification in physical properties and appearance e.g., handle and opacity (c) raise in the

shrinkage temperature, and (d) irreversibility of above mentioned properties.

123

Table 1.4: Tanning agents and characteristic

shrinkage temperature ranges

Tannage Type Tanning Agent

Shrinkage Temp. Range

(°C)

Raw Hide or Pelt None 60-65

Mineral

Chromium 100-115

Zirconium 90-98

Aluminium 70-80

Titanium 70-80

Vegetable

Condensed Tannins 80-85

Hydrolysable

Tannins 75-80

Syntan

Auxiliary 60-70

Replacement 70-80

Combination 70-80

Aldehyde

Formaldehyde 75-80

Glutaraldehyde 70-80

Polymers and Resins All 60-70

Definition of "Leathering" is difficult to describe from a scientific perspective but it

generally provides desired qualities for the production of any useful article. The raise in shrinkage

temperature is used as a scientific measure of tanning ability of a compound but it does not provide

any indication of the leathering. Aldehyde, Vegetable, tawing, brain, oil and smoke tanning

produce usable leathers after sole tanning, however, zirconium and chromium tanning produce

hard leathers which require additional processes (like retanning and fatliquoring) to achieve the

properties generally associated with the leather.

Brain, oil and smoke tanning [109] do not raise the shrinkage temperature and tawing

tanning is reversible and therefore these do not satisfy Covington's criteria for leather tanning. On

the basis of shrinkage temperature, tanning is divided into four zones as described in Table 1.5.

124

Table 1.5: The four tannage zones based on shrinkage

temperature.[112]

Tanning Zone Shrinkage Temperature (ºC)

Negative Tannages 30-60

Moderate Stability Tannages 60-85

Combination Tannages 80-100

High Stability Tannages 100-130

There is always a growing thrust towards uncovering a single strong theory for the tanning

within the leather science society. Following different approaches have been adopted for this quest,

(a) types of the interactive forces (b) identification of protein reactive sites with tanning systems

(c) changes in the shrinkage temperature, (d) evidence for the intermolecular crosslinking (e)

variations in protein charge and (f) changes in the collagen hydration [110].

Tanning does not modify the shrinking mechanism but it merely stabilizes thermal

degradation of the tanned material in which breaking of hydrogen bonds is involved without

affecting tannincollagen interactions [111]. Tanning agents show interaction with reactive sites on

collagen and thus vary collagen hydration, results in increased crosslinking and increase of

shrinkage temperature [112].

CHAPTER-2

125

LITERATURE REVIEW Literature review is grouped into following subcategories.

2.1Low/free formaldehyde amino resins National and international agencies and organization evaluated and classified the

carcinogenicity of formaldehyde both in occupational and non-occupational environment. The

differences in database and accordingly, conclusion are described in short historical review since

the formaldehyde was considered for the first time as concerned with health effects [113].

The ecological concerns have pushed leather industry to find out possible alternates for

chromium. A combination of vegetable and aluminum has been evaluated. Aluminum is part of

mineral tanning agents that are normally used to stabilize the collagens in leather tanneries. The

crosslinking of vegetable based retanning agents with aluminum and collagens results in chromium

free leather. This chrome free tannage process produces leathers with achieved specifications of

shrinkage temperature of upto 125oC, percentage elongation at break (65.6%),tensile strength 38

N/ m2, and tear strength 98 N/m2. The chemical characteristics of the retanned leathers are normal

in shrinkage temperature. Among the combination system, a vegetable based pre- tannage followed

by further retanning with basic aluminum sulfate produced stronger leather with the greater

durability. Pre-tanning of leather with aluminum made tanning agent tighten the collagen fiber that

prevents high molecular weight vegetable based tannins from affecting the collagen fibers.

Optimal results were produced at 10% of vegetable tannins and 2% Aluminum sulfate was used

[114].

Eco labeling awareness has grown demand towards the production of free formaldehyde

leather in global market. In the first part of this working, optimization of performance application

as a single syntan with desired properties has been described. The use of free formaldehyde syntan

in blend to make leather with acceptable characteristics has been applied. Three different

combinations of retanning have been selected by using free formaldehyde resin, polyacrylic and

protein hydrolysates. The leathers performance in terms of tensile strength and bulk properties was

126

found to be similar and even superior for all the retanning combinations which were selected for

comparison with control. Particularly, Experiment design “C” (based on syntan

- formaldehyde free 3%, acrylic based resin 4% and protein hydrolysates 2%) produces

leathers having improved tensile strength , color and bulk characteristics as well as low TS loads

and low

COD, besides producing leather free from formalin. Scanning electron

microscopic (SEM) shows similar extent of the leather filling in all

designed three combinations of retannings [115].

Melamine glyoxal resin is synthesized without catalyst using single vessel reaction of

melamine and biformyl in solvent dimethyl formamide. The catalysis nature of Melamine glyoxal

resin has been evaluated catalytically in the oxidation of the cyclohexene. The Melamine

glyoxylated resin/solvent/O2 oxidation approach can be subjected to cost effective, additive free,

metal-free, and eco-friendly favorable catalytic system. Oxidative behavior of the melamine

glyoxal resin is attributed to its capability to produce in situ organic peroxide moieties during

reaction process. Production of peroxide species is verified by KI/starch analysis and further its

presence is verified by complete inhibition effect of the 2, 2, 6, 6-tetramethylpiperidine-1-oxyl

(TEMPO) over the oxidation [116].

Catechins extracted from green tea have high reactivity with formaldehyde at room

temperature in the aqueous solution. Green tea extract with 30% catechins was investigated as a

scavenger for formaldehyde. Firstly, filter paper treated with tea extract was used to evaluate the

formaldehyde scavenging ability of green tea extract. Results concluded that filter paper saturated

with extract of green tea had strong ability to absorb vapors of formaldehyde and once

formaldehyde absorbed was released very hardly. Absorbed formaldehyde was not released even

the temperature was increased to 60oC. Green tea extract was applied to plywood and investigated

its formaldehyde scavenging ability. Formaldehyde was remarkably suppressed from the plywood

surface. Green tea extract has great potential to be used as formaldehyde scavenger [117].

127

Traditional procedure for the production of Urea-formaldehyde (UF) resin is condensation

polymerization of urea and formaldehyde in aqueous solution that produces low resistance of UF

resins against moisture and water and ultimately increases emission of formaldehyde. The recent

method for the synthesis of UF resin was involved melt condensation polymerization of urea and

paraformaldehyde. For the elucidation of uron rings of UF resin, 13C nuclear magnetic resonance

and infra-red spectroscopy were used. The stability at application and during the storage was

characterized by estimating concentration free formaldehyde, methanol TG and DSC analysis. It

was observed that UF resin by melt condensation polymerization as reduced content of free

formaldehyde with increased thermal and storage stability [118-123].

2.2Stability of amino resins A new melamine resin based tanning agent was prepared by using ethanolamine as an

etherifying agent. Water solubility and storage stability of newly developed product had been

improved greatly in comparison with melamine resins synthesized by conventional methods. In

this work, mechanism and conditions for the synthesis of new melamine tanning resin was

described in detail [124].

The storage uncertainty mechanism of water based melamine formaldehyde resin has been

studied. The plot of storage certainty which is explained as the time from the resin production till

milky character produced in the resin, against process time consists of descending and ascending

branch. By this study, it is noticed that formation of methylene bridges had more tendency for

coagulation rather than the formation of ether bridges [125-131].

The excellent stability polyhydroxymethyl melamine resin solution is prepared. The effect

of temperature and time on the reaction, effect of pH value of medium, concentration of the

reactant was studied in this study. IR used to elucidate the structure of the product. The optimum

reaction conditions are achieved, which are as follows, melamine: formaldehyde: MeOH mole

ratio =1:(3.5-6):(4-7) mole ratio, pH of hydroxymethylation step pH=7.5-9, reaction temperature

is 70-90℃,time of reaction is 0.5-1.5h,condensation and etherification step pH=4- 7,its

temperature is 50-70℃, and its time is 0.5-2h [132].

128

High-sulfonated melamine–formaldehyde (HSMF) resin was produced with a

sulfite/melamine (S/M = 1.5) molar ratios. In the sulfonation process, the effect on the resin by the

reactions temperatures and the added velocity of sodium bisulfite were studied. In condensation

stage, where the pH range is 6.0 and the temperatures are about 25°C, the condensation reaction

time was prolonged above 24 hours. The stability and water solubility of resin was better. It is

good super-plasticizer at small dosages of admixture [133].In this study, melamine formaldehyde

resin was studied with respect to storing stability, percentage of free formaldehyde, and solid

content. Further mutual relationship between structure and function of melamine resin was

analyzed [134].

2.3Structural elucidation

The experimental study for the addition reaction of formaldehyde and melamine has been

performed by direct observation with high speed liquid chromatography and nuclear magnetic

resonance (NMR) spectroscopy. All nine possible methylol melamines were assigned including

two isomeric forms of di-, tri- and tetramethylol melamine. Distribution of molecular size and

quantitative analysis of methylol melamine was studied by liquid-chromatographic technique.

Equilibrium and rate constants for individual reversible reactions were studied by these

quantitative methods [135].

The study and comparison of the structure of different syntans and natural tanning agents

is worked out. With reference to the tanning efficiency, following relationship of structure and

property was found. Although, there are methoxy groups in natural tannins which could not surely

proof a tanning effect as such. The spacer moiety between phenolic rings does play a significant

role in the tanning. Comparing different spacers, the benzyliden spacer proofed to be most valuable

for the shrinkage temperature. Whereas, methylene spacer and sulfone spacers appear more

valuable for physicochemical properties (solubility and accessibility). Catechol and pyrogallol are

highly oxidizable moieties which are present in natural tannins. Experimental trials showed that

they have less influence on the shrinkage temperature than the light fastness effect on the obtained

leathers. While, phenol based resins give best light fastness. Tanning capacity is influenced by the

129

molecular weight of resin condensates. A comparative trial of three different products with

different molecular weights, all products containing sodium salt of phenol sulfonic acid and found

different shrinkage temperatures of the resultant leather which showed increasing trend with

increasing molecular weight of product [136].

Melamine formaldehyde resin with high degree of sulphonation (HSMF) is synthesized by

reacting melamine, sodium sulphite, formaldehyde and sodium metabisulphite under reflux

through a four steps reaction. Mole ratio of sulphite/melamine varied between 1 .0—2 .0 and the

mole ratio of formaldehyde to melamine varied from 3.0 to 5.0. Fluidity behavior of amino resins

were studied with the effects of degree of sulphonation and F/M ratio were studied on the fluidly

of resin solutions. It was observed that F/M mole ratio is directly and S/M mole ratio is inversely

proportional to the viscosity of resin solutions. Highly sulphonated resins (HSMF) are expected to

be comparatively highly effective super plasticisers than that of sulphonated resin (SMF) for use

in cement sand mortar. The results of the study show that the fluidity of the resins decrease with

increasing molecular weight (M) of the polymeric resins until a critical stage of molecular weight,

then there is rapid increase in the viscosity beyond this point, due to the formation of hexagonal

close packed system [137].

Copolymer prepared by the condensation of melamine and p-cresol with an acid catalyst

present and by the use of variety of molar ratios of reacting monomers. The estimation of the

compositions of copolymer resin was done on the basis of elemental analysis. The determination

of the number average molecular weight was exercised in non-aqueous media by conductometric

titration. To verify the characteristic functions and constants of the copolymer resin the viscosity

of solution was measured in dimethyl sulfoxide (DMSO). The further characterization of

copolymer was carried out in non-aqueous media by UV-visible absorption spectra, nuclear

magnetic resonance and infra-red spectra. The thermal studies were conducted to ascertain the

activation energy (Ea), mode of decomposition, frequency factor Z, order of reaction (n), free

energy change (DF), entropy change (DS) and apparent antropy change (S*) of the copolymer

resins. The minute details of thermal decomposition curves were discussed with great care.

130

Thermal stability and thermal activation energy were estimated by the methods described

by Sharp-Wentworth and Freeman-Carroll. Thermal activation energy determined by this method

was in accordance with each other. The results from Freeman-Carroll procedure was used to study

various thermodynamic parameters. Thermal stability order of copolymers was estimated by TGA

[138].

Synthetic method for terpolymer of urea, melamine and formaldehyde was studied by using

melamine upto 2-12% levels. The reaction of melamine was performed at pH level 6.3 with

Formalin/(Urea + Melamine) molar ratios of 2.1 till required viscosity was obtained and second

stage urea was added at pH level 8.0 to get final Formalin/(Urea + Melamine) molar ratios of 1.15.

13C-NMR technique and viscosity determinations showed that MF reagents react very quickly and

UF component slowly in melamine reaction. As extent of preadvancement of UF resin was

lowered, the time of reaction to reach target

viscosity increased and MF resin reagents started showing higher degrees of condensation.

The over-polymerization of MF component results dense resins, with stable viscosity upto one

month. As the pre-advancement of Urea Formaldehyde based resin was progressed, the extents of

advancement of Melamine Formaldehyde components lowered, to

give clear resins, with increasing viscosity at room temperatures. [139].

Particle boards are manufactured by urea formaldehyde condensates. The processing of UF

resins is affected by the hardening behavior of the UF glue. TG-DTA process has been used to

study curing behavior of UF glue. Different grades of UF resins were selected and their curing

behavior was comparatively evaluated by TG-DTA technique. Experimentation was performed

with and without catalyst. Ammonium sulfate and ammonium chloride were used as a curing agent.

Crosslinking behavior of aged and fresh resins was also evaluated. [140].

2.4Applications of amino resins A urea formaldehyde condensate has been prepared under optimum conditions to use as a

tanning agent. The effects and characteristics of this condensate as a tanning agent were studied.

131

Different parameters like, tear strength, tensile strength, elongation at break, shrinkage area,

shrinkage temperature, putrefaction resistance, scanning electron microscopy and thermal

gravimetric analysis were studied [141].

2, 2-bis (hydroxmethyl)-1,3-propanediyl bis(dihydrogen phosphate) was prepared from

melamine, phosphous oxychloride and pentaerythritol. Optimum conditions for its synthesis were

obtained by orthogonal experiment. The structure of compound was confirmed by element

analysis, melting point and IR. The synthesized compound was modified further by using

formaldehyde and appropriate hydrophilic auxiliary, resulting a new multi-functional melamine

based tanning agent was obtained having flame resistance properties. The experimental results

prove that the product has good solubility, high-stability, good capability of filler retanning and

efficient flame resistance [142].

The better properties, the characteristics of the synthetic reaction, methods for modification

of melamine resin and application in the leather industry are introduced in this work. Especially,

it is very essential that multifunctional melamine based retanning resin was developed and found

its application in leather industry [143].

Amphoteric aromatic based retanning agent is synthesized from fatty aldehyde, α- halo acid, and

compound containing amino group like urea, aniline, and dicyandiamide etc. The technology and

synthetic routes are studied. Existance of amphoteric group in the product is proved with the help

of IR technique [144].

All types of organic tanning and retanning agents have been categorized in to different

groups, formula and name of tanning agent, tanning mechanisms and different properties of the

tanned leathers are discussed. In this work, recent developments since 1990s in different research

fields are summarized [145].

A sulphited urea formaldehyde condensate has been synthesized for pre and retanning

agent. The retanning behavior of prepared polymer on the buffalo leather was studied and

compared with most commonly functional products, basic chromium sulfate tan with vegetable

132

extract as retannage. The properties of treated leather were studied. These properties were

comparatively used to evaluate applicability of polymer as efficient tanning agent [146].

The comprehensive characteristics of casein dry film have been found to be improved in

friction resistance, water resistance and impact resistance etc., by crosslinking of-NH2,-NH-,-

COOH and-OH functional groups in the casein with melamine. The principle of its chemical

modification and applications of melamine crosslinked casein are also studied in this work

modification [147].

Melamine, urea, aniline, dicyandiamide, chloroacetic acid and formaldehyde were used to

synthesize amphoteric, new amino resin based tanning agent, Optimum conditions were obtained

by carrying out series of experiments. IR analysis proved existence of amphoteric group in the

resin [148].

Melamine–formaldehyde–di-ethylene-tri-amine-penta-acetic acid di-ethylene-tri-amine-

pentaacetic acid to melamine during melamine formaldehyde reaction in acidic media. The effects

of conditions, like temperature, water content, acidity on resin properties such as rigidity, water

regain, DTPA functionality and porosity were studied to identify the optimum synthetic conditions

[149].

Chemically the resin was characterized by FTIR, elemental analysis, solid state 15N NMR

and 13

C NMR. The resin was morphologically characterized by BET technique, scanning electron

microscopy. The regaining water factor was checked to evaluate water loving nature of the

synthetic resin. The performance of modified melamine resin as adsorbant for heavy metals, like

Cd (II), Co (II), cu (II), Zn (II) was studied too. Quantitative estimation for adsorptions was

determined by atomic absorption. In this work, potential application of modified melamine resin

was confirmed to remove heavy metal ions form effluent [150].

133

Formaldehyde based lower molecular weights pre-condensates (fixers) are important in the

woven fabrics processing. Their two important uses are fixing of dyestuff and crease resistant

improvement. The synthesis of pre-condensates by condensing formaldehyde with various molar

ratios of melamine and urea was studied which belongs to thermo-setting resins. Specimens of

dyed cotton pieces were impregnated with synthesized fixers and cured at temperature 150°C for

three minutes with curing catalyst acetic acid. Crocking to dry and wet rubb fastness, light fastness,

color fastness is determined. These testing depend on fixing performance of pre-condensate to the

dye. Pre-condensate based on melamine, urea and formaldehyde with molar ratios of 50/50 gave

an optimum fixing efficiency. Light fastness is dependent on aromatic nature of the melamine ring

which was due to absorption in UV region. Intense color fabrics with good properties were resulted

from experiments that present a possibility for the extension of the applied, in practice, textile pre-

condensates [151].

In the presence of etherified melamine formaldehyde (MF) resin the possibility of

production of crosslinkable latex by emulsion polymerization was studied. At ambient temperature

the latexes were crosslinked to give solvent resistant and tough films. The acid catalysts of high

levels were required. The better results were expressed by hydrophobic MF resin that was

etherified with almost 1 mole of isooctanol 5 moles of methanol than monomeric MF resins

completely etherified with methanol, that was more hydrophilic and MF resin etherified with

butanol, less miscible in acrylic copolymers [152].

Melamine-glyoxal condensed polymer as a decolorizing flocculent was prepared with

glyoxal and melamine and ammonium chloride as catalyst. The effect of reaction time, reaction

temperature, and dosage of glyoxal, melamine and ammonium chloride were studied. Moreover

COD removal efficiency and the de colorization were also studied. The optimized conditions were

as the dosage of glyoxal, melamine and ammonium chloride 58, 10 and 10 respectively. The time

for reaction was for hours at 60 °C. The product expressed convincing decolorizing effect at 94 -

96 % rate and 49-57 % was the rate of COD removal [153].

134

A wet strength resin similar to melamine formaldehyde is a new melamine-glyoxal. It was

synthesized by the substitution of glyoxal for formaldehyde. The parameters of reaction were

optimized by orthogonal experiments and performance was studied [154].

Study on vegetable based tanning agents was performed by rural tanners of Hukuntsi

District, Botswana. In 14 villages, Interview of 57 tanners was taken using a questionnaire. Data

was also composed by direct interviewing with observation of elemental informants. Data was

composed on variety of tanned skins, tanning agents of vegetable based and experience of the

respondents in the tanning was collected. Majority of tanners were males according to given

results. About (81.7%) of respondents said they are practicing leather tanning from 5 to 30 years,

which indicate that majority of respondents were experienced in the tanning. The two types of

vegetable tanning agents in their villages were Terminalia cericea (mogonono) and Elephatina

elephantorrhiza (mositsane) are very common. The tanning agents of vegetable were used in

combination or alone with different others to boost performance. The parts of the plants used for

tanning were roots tubers, and barks. Other tanning materials used were brains and fats of animal.

In this study, popular skins (71.9%) tanned were small stocks (goats and sheep) along with wild

cats. skins which are tanned were utilized for blankets, clothing, shoes and saddles that were source

of income by selling them. These results suggest that the artisan tanning plays an important part in

reducing poverty and the food security of household [155].

The chrome tanning system, which is most popular leather producing procedure, is under

constant pressure from international regulations and environmental groups. Therefore, from many

years, frequent experiments have been performed on chrome free leather production. In this present

study, newly synthesized organic and inorganic chemicals were processed as tanning and

pretanning agents as a substitute to chrome tanning agent. The newly developed titanium based

compound, collected from the processing wastes of nonferrous metals industry, was processed as

a main tannage. In addition, an oligomeric form of melamine-formaldehyde resin and prepolymer

of resorcinol formaldehyde condensate were used in pre-tanning for producing chrome free

leathers. Physical and chemical testing of chrome free produced leather gave equivalent results to

leather tanned with salt of basic chromium sulfate [156].

135

CHAPTER-3

EXPERIMENTAL WORK Amino resins like melamine formaldehyde and urea formaldehyde resins are

widely used in the leather industry as a tanning agent. There are some drawbacks in the

136

application of these resins like they get precipitated in the acidic media causing

superficial deposition of the resin on the leather surface. They possess formaldehyde

contents greater than permissible limit, facing international legislation of environmental

concern.

In this work, different series of hydrazide modified amino resins with

permissible limit of formaldehyde content and non-formaldehyde eco-friendly amino

resins has been worked out.

A collaborated research work was accomplished between Department of

Chemistry, G.C University, Lahore and Research & Development department of SRC

(PVT) LTD, a national specialty leather chemical manufacturing company.

The study was divided into two major parts.

1- Synthesis, characterization and application of low formaldehyde hydrazide

modified amino resins

2- Synthesis, characterization and application of non formaldehyde eco friendly

amino resins

3.1 Chemicals used in the study Chemicals used in the present research work are given as below.

Table 3.1: List of chemicals

Sr. No Chemical Company Remarks

1 Succinic dihydrazide Vtolo Industrial Limited Commercial

2 Glutaric dihydrazide Vtolo Industrial Limited Commercial

3 Adipic dihydrazide Vtolo Industrial Limited Commercial

4 Isophthalic dihydrazide Vtolo Industrial Limited Commercial

5 Terephthalic dihydrazide Vtolo Industrial Limited Commercial

6 Melamine DSM Commercial

7 Formaldehyde Wah Nobel Commercial

137

8 Glyoxal Merck Analytical grade

9 Glutaraldehyde BASF Commercial

10 Sodium metabisulfite Panreac Analytical grade

11 Sodium hydroxide BDH (England) Analytical grade

12 Sulfamic acid Sigma Aldrich Analytical grade

13 Formic Acid BASF Commercial

14 Sodium carbonate Merck (Germany) Analytical grade

15 Sodium formate BASF Analytical grade

16 Glacial acetic acid Merck Analytical grade

17 Ammonium acetate Fluka Chemie Analytical grade

18 Acetyl acetone Fluka Chemie Analytical grade

19 5, 5’-Dimethyl-1, 3-cyclohexanedione Sigma Aldrich Analytical grade

20 Sulfuric acid Sigma Aldrich Analytical grade

21 Sodium Thiosulfate Sigma Aldrich Analytical grade

3.2 Synthesis of sulfonated succinic dihydrazide

formaldehyde condensates Sulfonated succinic dihydrazide formaldehyde condensates were prepared by the

following procedure.

0.2 moles of aqueous solution of formaldehyde (36%) was taken in a three neck

round bottom flask, assembled with stirrer, thermometer and condenser, 90g of water

was added and the mixture was heated to 55oC. The pH of formaldehyde solution was

adjusted to

7.5 with 0.5N sodium hydroxide solution. 0.1 mole of succinic dihydrazide1 was

added to reaction vessel and reaction temperature was increased to 60oC and stirred for

15 minutes to yield dimethylol succinic dihydrazide. Sodium metabisulfite (0.01 mole)

was added to the reaction mixture and heated to 80oC for one hour.

The pH of reaction mixture was adjusted to 5-6 by addition of few drops of 30%

(W/W) of formic acid. Reaction mixture was maintained in these conditions for 30

minutes. The pH of reaction mixture was raised to 7.5-8.0 with 0.1N sodium hydroxide

138

to quench the reaction. The reaction mixture was heated to 80oC for one hour with

constant stirring. The resulting resin solution was cooled to 25oC and filtered. The dry

content of the resin was determined by drying a known quantity of resin in oven for 1

hour at 103-105oC and adjusting dry contents up to 35±1% by water.

Under these optimum conditions, the following sets of experiments given in

Table 3.2 were performed with varying mole ratios of sodium metabisulfite/succinic

dihydrazide and formaldehyde/succinic dihydrazide.

Table 3.2: Experimental data of succinic dihydrazide formaldehyde condensates

Trials

Sodium metabisulfite/

succinic dihydrazide

(S/SDH)

Formaldehyde/

succinic dihydrazide

(F/SDH)

SDH # 01 0.1 2

SDH # 02 0.2 2

SDH # 03 0.3 2

SDH # 04 0.4 2

SDH # 05 0.1 3

SDH # 06 0.2 3

SDH # 07 0.3 3

SDH # 08 0.4 3

SDH # 09 0.1 4

SDH # 10 0.2 4

SDH # 11 0.3 4

SDH # 12 0.4 4

SDH # 13 0.1 5

SDH # 14 0.2 5

SDH # 15 0.3 5

SDH # 16 0.4 5

139

3.2.1 Mechanism for the synthesis of succinic dihydrazide

formaldehyde condensate

The reaction for synthesis of succinic dihydrazide formaldehyde condensate was

divided into four steps as provided in scheme 1.1 to 1.4.

3.2.1.1 Methylolation of succinic dihydrazide (1)

Succinic dihydrazide (1) reacts with formaldehyde (2) through addition reaction

by nucleophilic attack of succinic dihydrazide on carbonyl functionality of

formaldehyde in alkaline media, which produces methylol succinic dihydrazide (3) as

described in scheme 1.1. Different parameters like pH, reaction time, reaction

temperature and molar concentration of reactants affect this methylolation step.

Scheme 1.1: Methylolation of succinic dihydrazide with formaldehyde

3.2.1.2 Sulfonation of dimethylol succinic dihydrazide (3)

Methylolated succinic dihydrazide (3) was sulfonated by sodium metabisulfite

(4). Sulfonating agent first hydrolyzed in water to form hydroxide and bisulfite ions (4a)

as shown below in equation no. 1

Hydroxide ion raises the pH of solution to 9-10 and the bisulfite ion take part in

sulfonation of methylolated succinic dihydrazide (3) in basic media as given in scheme

140

1.2.

O

OO

O + + HSO3- Na HO.CH

HO.CHCH2.SO3-Na+

CH2.OH

3 5 Scheme 1.2: Sulfonation of dimethylolated succinic dihydrazide with sodium

metabisulfite in basic medium.

Sodium metabisulfite (4) is sulfonating agent and its molar ratio vs succinic

dihydrazide varies from 0.1-0.4. Sulfonation step is affected by pH, reaction temperature

and time.

3.2.1.3 Acidic pH condensation

Under acidic (pH 4.5-5) condition, resin condensation takes place. During this

condensation, ether linkage is developed in the oligomeric condensed form (6) as shown

in scheme 1.3. Reaction mixture undergoes at a higher rate, further condenses under

reduced pH of the solution, which leads to viscous solution due to high molecular

structure (7) up to such extent that gellation of the product usually occurs.

O O

N H

N H

N H N H 2

N H

N H

N H N H 2

141

CH2.SO3-Na+

O O

Polymeric Condensed Resin

7

Scheme 1.3: Condensation of succinic dihydrazide, monomethylolated succinic

dihydrazide and sulfonated monomethylolated succinic dihydrazide in acidic media

3.2.1.4 Basic pH condensation

The resin solution is stabilized in this step. The reaction is quenched by raising

pH to 7.58.0with 0.2N sodium hydroxide. Otherwise the product may go to gellation

with high molecular weight. During this stage, condensations of resin take place and

methylene bridges are formed in the resulting structure (8, 9) between methylol moieties

of methylolated succinic dihydrazide with amino functionality of other

N H

N H O

N H N H

CH 2 .SO 3 - Na

+ HO.CH 2

+ N H

N H O

N H N H HO.CH 2

O H

O

N H N H

O

N H

N H

CH 2 .SO 3 - Na

+

O

N H N H

O

O

N H N H

O H

Condensation of monomers in acidic media

6

5 3

O

N H N H

N H N H O N H

N H O

N H N H

O H

n

142

monomethylolated succinic dihydrazide as shown in scheme 1.4, which results in

stabilization of the resin.

O O

O

+

HO.CH

CH2.SO 3-

Na+

HO

5 3

O

Na O

Oligomeric Condensed form II

8

9

Scheme 1.4: Condensation of succinic dihydrazide, monomethylolated succinic

dihydrazide and sulfonated monomethylolated succinic dihydrazide in basic media

O

N H

N H

O

N H N H

N H

N H

O

O

N H N H

O H

S

O

O

O - Na

+

n Polymeric Condensed Resin

N H

N H

N H N H 2

N H 2

N H O

N H N H

Condensation of monomers in basic media

N H N H

O

N H N H

N H N H O

O

N H N H

O H

S O

O

+ -

143

3.3Synthesis of sulfonated glutaric dihydrazide formaldehyde resin

Sulfonated glutaric dihydrazide formaldehyde resins were synthesized with

various reactants mole ratio. Formaldehyde (aqueous solution 34-35%, 0.1 mol) was

taken in three necked round bottom flask, fitted with thermometer, condenser and stirrer

by addition of 50 g of water keeping the pH of the formaldehyde solution at 7.5-8.0 by

using 0.5N sodium hydroxide solution. Glutaric dihydrazide (0.1 mol) was added to

reaction mixture followed by addition of 0.01 mole of sodium metabisulfite and reaction

mixture was heated to 90°C and pH was adjusted to 4.5-5.0 with 0.2N formic acid and

stirred for half hour at 90°C. Reaction was quenched by adjusting pH to 7.5-8.0 with

0.5N sodium hydroxide to make a water soluble polymer. Stirring of reaction mixture

was continued throughout reaction. Resulting resinous solution was cooled to 30±2oC.

The solid contents of reaction product was calculated by drying a known amount of resin

in the oven at 103-105°C for one hour as per standard procedure [199] and finally

adjusting solid contents up to 32±1% by water.

Under these optimum conditions, the following set of experiments given in Table

3.3 were performed with varying mole ratios of sodium metabisulfite/glutaric

dihydrazide and formaldehyde/glutaric dihydrazide.

Table 3.3: Experimental data of glutaric dihydrazide formaldehyde condensates

S.No. Sodium metabisulfite/ Glutaric dihydrazide

(S/GDH)

Formaldehyde/ Glutaric dihydrazide

(F/GDH)

GDH # 01 0.1 1

GDH # 02 0.2 1

GDH # 03 0.3 1

GDH # 04 0.4 1

GDH # 05 0.5 1

GDH # 06 0.1 2

GDH # 07 0.2 2

GDH # 08 0.3 2

GDH # 09 0.4 2

GDH # 10 0.5 2

144

GDH # 11 0.1 3

GDH # 12 0.2 3

GDH # 13 0.3 3

GDH # 14 0.4 3

GDH # 15 0.5 3

3.3.1 Mechanism for the synthesis of glutaric dihydrazide formaldehyde

condensate

The schematic route for the synthesis of glutaric dihydrazide formaldehyde

condensate was divided in three following steps:

3.3.1.1 Methylolation

Glutaric dihydrazide (10) reacts by nucleophilic attack on carbonyl group of

formaldehyde (2) in basic media, which produces hydroxymethylated glutaric

dihydrazide. Different reaction parameters like reaction time, pH, mole ratio of

reactants and reaction time affected the methylolation. Monomethylol (11), dimethylol

(12), trimethylol (13) and tetramethylol (14) glutaric dihydrazide are formed as shown

in scheme 2.1.

145

Scheme 2.1: Methylolation of glutaric dihydrazide with formaldehyde by the

mole ratio of glutaric dihydrazide and formaldehyde of 1:1, 1:2, 1:3 and 1:4.

3.3.1.2 Sulfonation

Sulfonation of methylolated glutaric dihydrazide was achieved by sodium

metabisulfite. Sodium metabisulfite hydrolyzed in water to form bisulfite ion as shown

in equation no1. Bisulfite ion takes part in sulfonation of methylolated glutaric

dihydrazide in basic medium to form sulfomethylated glutaric dihydrazide (15) as

shown in scheme 2.2. The mole ratio of sodium metabisulfite was varied from 0.1-0.5

with respect to glutaric dihydrazide.

Scheme 2.2: Sulfonation of monomethylolated glutaric dihydrazide with sodium


3.3.1.3 Condensation of monomers

In condensation reaction, methylolated monomers condensed with each other in

two ways depending upon reaction conditions. Ether linkages were developed in the

resulting molecular structure (16) by methylol moieties of two different monomers in

acidic pH range of 4.5-5.0 and methylene bridges were developed in the resulting

structure (17) by condensation between methylol moiety of methylolated glutaric

dihydrazide and amine functionality of glutaric dihydrazide (10) in pH range of 7.5-8.5.

Condensation of glutaric

dihydrazide (10), monomethylolated glutaric dihydrazide (11) and sulfonated

monomethylolated glutaric dihydrazide (15) in acidic media is shown in scheme 2.3

146

Scheme 2.3: Condensation of glutaric dihydrazide, monomethylolated glutaric

dihydrazide and sulfonated monomethylolated glutaric dihydrazide in acidic and

alkaline media

3.4Preparation of sulfonated adipic dihydrazide formaldehyde resin

Sulfonated adipic dihydrazide formaldehyde resins were synthesized by

following procedure. Briefly, 30.77g (0.369 mole) of formaldehyde (aqueous solution

36%) was taken in three necked round bottom flask, fitted with thermometer and a

condenser. 197g of water added and stirrer, and pH of the formaldehyde was kept at

7.5–8.0 by adding 0.5 N sodium hydroxide solutions. Then, 64.80 (0.369 mole) of adipic

dihydrazide was added to reaction mixture followed by addition of 7.16g (0.0369 mole)

of sodium metabisulfite; the reaction mixture was heated to 90°C under stirring for two

hours and then pH was adjusted to 4.5–5.0 with 0.2N formic acid and stirred for half

hour at 90°C. After half hour, reaction was quenched by adjusting pH to 7.5–8.0 by

using0.5N sodium hydroxide to make water soluble polymer. Resulting resinous

147

solution was cool down to 30±2°C. The solid contents of reaction product were

calculated by drying a known amount of resin in the oven at 103–105°C for one hour as

per standard procedure [199] and finally adjusting solid contents up to 32±0.25% by

water.

Under these optimized conditions, set of different experiments given in table 3.4

were performed with various mole ratios of reactants.

Table 3.4: Experimental data of adipic dihydrazide formaldehyde condensates

Sr. # (S/ADH) (F/ADH)

ADH #01 0.1 1

ADH #02 0.2 1

ADH #03 0.3 1

ADH #04 0.4 1

ADH #05 0.5 1

ADH #06 0.1 2

ADH #07 0.2 2

ADH #08 0.3 2

ADH #09 0.4 2

ADH #10 0.5 2

ADH #11 0.1 3

ADH #12 0.2 3

ADH #13 0.3 3

ADH #14 0.4 3

ADH #15 0.5 3

F/ADH Formaldehyde/Adipic dihydrazide, S/ADH Sodium

metabisulfite/Adipic dihydrazide.

148

3.4.1 Mechanism for the synthesis of adipic dihydrazide formaldehyde

condensate The schematic route for synthesis of adipic dihydrazide formaldehyde

condensate was divided in three steps of scheme 3.


Adipic dihydrazide (18) undergo nucleophilic attack on carbonyl functional

group of formaldehyde (2) in basic media, which produce monomethylol (19),

dimethylol (20), trimethylol (21) and tetramethylol (22) of adipic dihydrazide depending

upon the mole ratio of formaldehyde to adipic dihydrazide as shown in scheme 3.1.

O

OO O HN + HCHO

O O O

18 H2N 2

OH 19

Scheme 3.1: Methylolation of adipic dihydrazide with formaldehyde

The mole ratio of adipic dihydrazide and formalin was varied from 1–3.

3.4.1.2 Sulfonation

Sulfonation of methylolated adipic dihydrazide (19) was conducted by sodium

metabisulfite. Bisulfite ion takes part in sulfonation of methylolated adipic

dihydrazide in basic media to form sulfomethylated adipic dihydrazide (23) as shown in

scheme 3.2, which is produced by hydrolysis of sodium metabisulfite as shown in

equation no. 1.

N H N H

O

N H

N H

O H O H

O

N H N

N H

N H

O H O H

O H

O

N H N

N H

N O H

O H

O H

O H 20 21 22

N H N H 2

N H

N H

N H N H 2

149

O O

OO

+ HSO3- Na+

OH 19 SO3Na 23

Scheme 3.2: Sulfonation of monomethylolated adipic dihydrazide with

sodium metabisulfite in basic medium.


During condensation reaction, methylolated monomers condense with each other

in two ways depending upon reaction conditions. Ether linkage is developed in the

resulting polymer (24) by reaction of methylol moieties of two different monomers in

acidic pH range of 4.5–5.0 and methylene bridges are formed in the resulting polymer

(25) by condensation between methylol moiety and amine functionality of adipic

dihydrazide in pH range of 7.5–8.5 as shown in scheme 3.3.

O O

O

+ Condensation of

monomers In

acidic and Basic media

23

N H N H 2

N H

N H N H N H 2

N H

N H

150

25 Scheme 3.3: Condensation of monomethylolated adipic dihydrazide and

sulfonated monomethylolated adipic dihydrazide in acidic and basic media

3.5 Preparation of sulfonated isophthalic dihydrazide formaldehyde resin

Sulfonated Isophthalic dihydrazide formaldehyde resins were synthesized by various

reactant molar ratios. 138.66g of water was taken in a three necked flask fitted with

condenser, stirrer and thermometer; 70.50g of isophthalic dihydrazide (0.35 mole) and

41.875 of sodium metabisulfite (0.215 mole) were added to the reaction mixture and

stirred to disperse the material. 44.97g of 36% strength formaldehyde (0.539 mole)

whose pH has already adjusted with 0.5N sodium hydroxide solution up to 7.5 -8 and

reaction mixture was heated to 90oC and stirred for one hour at this temperature. In this

reaction, formaldehyde to isophthalic dihydrazide mole ratio (F/ISPDH) was kept 1.5:1

and sodium metabisulfite to isophthalic dihydrazide mole ratio (S/ISPDH) was kept 0.6:

1. Stirring of reaction was continued throughout the reaction. The resulting resinous

solution was cool down to 30±2oC temperature. The final solid contents of the resin

solution was adjusted to 40±0.2 which was determined by drying the resin at 103-105oC

for one hour as per standard procedure [157].

Under these conditions, set of experiments were conducted given in Table 3.5

with various molar ratios of reactants.

Table 3.5: Experimental data of isophthalic dihydrazide formaldehyde condensates

Experiment No. Formaldehyde/Isophthalic

dihydrazide mole ratio (F/ISPDH)


Isophthalic dihydrazide mole

ratio (S/ISPDH)

ISPDH # 01 1.5 0.1

ISPDH # 02 1.5 0.2

ISPDH # 03 1.5 0.3

ISPDH # 04 1.5 0.4

ISPDH # 05 1.5 0.5

ISPDH # 06 1.5 0.6

151

ISPDH # 07 1.5 0.7

ISPDH # 08 2 0.1

ISPDH # 09 2 0.2

ISPDH # 10 2 0.3

ISPDH # 11 2 0.4

ISPDH # 12 2 0.5

ISPDH # 13 2 0.6

ISPDH # 14 2 0.7

ISPDH # 15 2.5 0.1

ISPDH # 16 2.5 0.2

ISPDH # 17 2.5 0.3

ISPDH # 18 2.5 0.4

ISPDH # 19 2.5 0.5

ISPDH # 20 2.5 0.6

ISPDH # 21 2.5 0.7

ISPDH # 22 2.5 0.8

ISPDH # 23 2.5 0.9

ISPDH # 24 2.5 1

ISPDH # 25 3 0.1

ISPDH # 26 3 0.2

ISPDH # 27 3 0.3

ISPDH # 28 3 0.4

ISPDH # 29 3 0.5

ISPDH # 30 3 0.6

ISPDH # 31 3 0.7

ISPDH # 32 3 0.8

ISPDH # 33 3 0.9

ISPDH # 34 3 1

Note: Gel formed resins were not applied on leather as retanning agents. Only

stabilized resins were evaluated as retanning agents

152

3.5.1 Mechanism for the synthesis of Isophthalic dihydrazide

formaldehyde condensate

The schematic route for synthesis of Isophthalic formaldehyde condensate was

described by following steps in scheme 4.


Isophthalic dihydrazide (26) reacts by nucleophilic attack on the carbonyl group

of formaldehyde (2) in basic media to form monomethylol isophthalic dihydrazide (27),

dimethylol isophthalic dihydrazide (28), trimethylol isophthalic dihydrazide (29) and

tetramethylol isophthalic dihydrazide (30) depending upon the mole ratio of

formaldehyde to isophthalic dihydrazide as shown in scheme 4.1.

O NH O NH 2OH

O Basic media

+ HCHO

H2N 2 H2N 27

26

O

NH O NH O NH OHOHOH

HO

HO HO HO 28 29 30

N H

N H

O

N H

N H

N H

N

O

N H

O H

N H

N

O

N

O H

N H

N H

O

N H

153

Scheme 4.1: Methylolation of isophthalic dihydrazide with formaldehyde

These hydroxymethylated isophthalic dihydrazides are highly reactive and self

polymerize to form a crosslinked water insoluble product. Different parameters like

reaction time, molar ratios and pH affect this methylolation step. Mole ratio of

formaldehyde to isophthalic dihydrazide was varied from 1.5 – 3.

3.5.1.2 Sulfonation

Sulfonation of methylolated isophthalic dihydrazide was

conducted by sodium metabisuphite (4), which hydrolyze in

aqueous media as shown in equation no. 1.

Bisulfite ion takes part in sulfonation of

dimethylolated isophthalic dihydrazide to form

sulfonated monomethylolated isophthalic

dihydrazide (27) as shown in scheme 4.2.

+ - Na+

HSO3

NH NH

- +

NHOH 4aNHSO3 Na

O

28 31

Scheme 4.2: Sulfonation of dimethylolated isophthalic dihydrazide with sodium


Molar ratio of sodium metabisulfite vs isophthalic dihydrazide varied from 0.1-

1 to stabilize the resin in liquid form.


In condensation reaction, methylolated monomers condense with each other to

form condensed polymer with varying degree of condensation in two ways depending

N H

N H

O

O H

N H

N H

O

O H

O

154

upon reaction conditions. Ether linkage is developed in polymer (32) by methylol

moieties of two different hydroxymethylated monomers under acidic conditions and

methylene bridges in polymer (33) are formed by condensation between methylol

moiety and amine functionality of isophthalic dihydrazide under basic conditions.

Scheme 4.3: Condensation of isophthalic dihydrazide, monomethylolated

isophthalic dihydrazide and sulfonated monomethylolated isophthalic dihydrazide in acid

and basic media

3.6 Preparation of sulfonated terephthalic dihydrazide

formaldehyde condensates

Sulfonated terephthalic dihydrazide formaldehyde condensates were prepared by

various reactant molar ratios. 138.66g of water was taken in a three necked flask fitted

with condenser, thermometer and stirrer, added 70.50g of terphthalic dihydrazide (0.35

mole), 41.87g of sodium metabisulfite (0.215 mole) and mixed to disperse the material.

44.97g of 36% strength formaldehyde (0.539 mole) was added whose pH already

adjusted with 0.5N sodium hydroxide solution to 7.5-8 and the reaction mixture was

heated to 90oC and stirred for one hour at this temperature. In this reaction,

formaldehyde to terephthalic dihydrazide mole ratio (F/TPDH) was 1.5:1 and sodium

metabisulfite to terephthalic dihydrazide mole ratio (S/TPDH) was 0.6: 1. The reaction

mixture was stirred throughout the reaction. The resulting resinous solution was cooled

to 30±2oC temperature. The final solid contents of the resin solution was adjusted to

155

40±0.2 which was determined by drying the resin at 103-105oC for one hour as per

standard procedure [158].

Under these conditions, the set of experiments conducted are given in Table 3.6

with various molar ratios of reactants.

Table 3.6: Experimental data of terephthalic dihydrazide formaldehyde

condensates

Experiment No. Formaldehyde/Terephthalic

dihydrazide mole ratio (F/TPDH)


Terephthalic dihydrazide

mole ratio (S/TPDH)

TPDH # 01 1.5 0.1

TPDH # 02 1.5 0.2

TPDH # 03 1.5 0.3

TPDH # 04 1.5 0.4

TPDH # 05 1.5 0.5

TPDH # 06 1.5 0.6

TPDH # 07 1.5 0.7

TPDH # 08 2 0.1

TPDH # 09 2 0.2

TPDH # 10 2 0.3

TPDH # 11 2 0.4

TPDH # 12 2 0.5

TPDH # 13 2 0.6

TPDH # 14 2 0.7

TPDH # 15 2.5 0.1

TPDH # 16 2.5 0.2

TPDH # 17 2.5 0.3

TPDH # 18 2.5 0.4

TPDH # 19 2.5 0.5

TPDH # 20 2.5 0.6

TPDH # 21 2.5 0.7

TPDH # 22 2.5 0.8

TPDH # 23 2.5 0.9

TPDH # 24 3 1

156

TPDH # 25 3 0.1

TPDH # 26 3 0.2

TPDH # 27 3 0.3

TPDH # 28 3 0.4

TPDH # 29 3 0.5

TPDH # 30 3 0.6

TPDH # 31 3 0.7

TPDH # 32 3 0.8

TPDH # 33 3 0.9

TPDH # 34 3 1

3.6.1 Mechanism for the synthesis of terephthalic dihydrazide formaldehyde

condensate

The schematic route for synthesis of Terephthalic dihydrazide formaldehyde

condensate was described by following steps in scheme 5.1 to 5.3.


Terephthalic dihydrazide (34) reacts by nucleophilic attack on the carbonyl

group of formaldehyde (2) in basic media to form monomethylol Terephthalic

dihydrazide (35), dimethylol Terephthalic dihydrazide (36), trimethylol Terephthalic

dihydrazide (37) and tetramethylol Terephthalic dihydrazide (38) depending upon the

mole ratio of formaldehyde to Terephthalic dihydrazide as shown in scheme 5.1.

O NH NH2

Basic media

+ HCHO

H2

N

NH 34 O 2 NH O

35

N H 2

O N H N H O H

157

36 37

38

Scheme 5.1: Methylolation of terephthalic dihydrazide with formaldehyde

These hydroxymethylated terephthalic dihydrazides are highly reactive and self

polymerize to form a cross-linked water insoluble product. Mole ratio of formaldehyde

was varied from 1.5 – 3.

3.6.1.2 Sulfonation

Sulfonation of methylolated terephthalic dihydrazide was conducted by sodium

metabisulphite (4). In water, Sodium metabisulfite was hydrolyzed to form hydroxide

ions and bisulfite (4a) ions as in equation no. 1. Bisulfite (4a) ion takes part in

sulfonation of methylolated terephthalic dihydrazide in basic media to form

sulfomethylated terephthalic dihydrazide (39) as shown in scheme 5.2.

OHOH

N H

O

N

O H

O H

O

N H N

O H

O H

O H

N H

O

N H

O H

O

N H N

O H

O H

N H O N H O H

O N H N H

158

+ - Na+

HSO3

4a

OHSO3-Na+

Scheme 5.2: Sulfonation of dimethylolated

terephthalic dihydrazide with sodium metabisulfite in

basic medium.

Molar ratio of sodium metabisulfite vs terephthalic dihydrazide was varied from

0.1-1 to stabilize the resin in liquid form.


In condensation reaction, methylolated monomers condense with each other to

form condensed polymer with varying degree of condensation in two ways depending

upon reaction conditions. Ether linkage is developed in polymer (40) by methylol

moieties of two different hydroxymethylated monomers and methylene bridges in

polymer (41) are formed by condensation between methylol moiety and amine

functionality of terephthalic dihydrazide depending on reaction conditions as shown in

scheme 5.3.

40

O N H

N H

- +

O N H N H O H

O N H N H O N H

N H O

n

n

O N H

N H

SO 3 - Na

+

O N H N H N H

N H O

O N H

N H O H

36

N H

N H

O

N H

N H

O

39

N H

N H

O

N H

N H

O

159

SO3 Na 41

Scheme 5.3: Condensation of terephthalic dihydrazide, monomethylolated

terephthalic dihydrazide and sulfonated monomethylolated terephthalic dihydrazide in

acid and basic media

3.7Preparation of sulfonated melamine glyoxylated resin

Sulfonated melamine glyoxylated resins were prepared by following procedure.

94.54g of water was taken in round bottom three necked flask, fitted with

condenser and thermometer. 87.31g of (0.601 mol) of glyoxal (aqueous solution 40%)

was added in the flask. Then 44.03g (0.451 mol) of sulfamic acid and 36.10g (0.451

mol) of sodium hydroxide (aqueous solution 50%) were added to form sodium sulfamate

and pH was adjusted to 7.5-8 by sodium hydroxide solution (0.5 N). Then, 37.98 g (0.3

mol) of melamine was added and the reaction mixture was heated to70oC under stirring

for three hours. Reaction mixture was cooled to 28±2oC. Solid contents of resulting resin

was determined by heating a known amount of the resin in oven at 103-105oC for one

hour as per standard procedure [159]. Solid content of the resin was adjusted upto

45±0.5 % by adding water.

Different set of experiments as given in Table 3.7 were performed under the

optimum conditions with different reactant mole ratios.

Table 3.7: Experimental data of Melamine glyoxylated condensates

Experiment No G/M S/M

MGO Resin # 01 2 0.5

MGO Resin # 02 2 1


MGO Resin # 04 2 2


MGO Resin # 06 2 3

160


MGO Resin # 08 3 1


MGO Resin # 10 3 2


MGO Resin # 12 3 3


MGO Resin # 14 4 1


MGO Resin # 16 4 2


MGO Resin # 18 4 3


MGO Resin # 20 5 1


MGO Resin # 22 5 2


MGO Resin # 24 5 3


MGO Resin # 26 6 1


MGO Resin # 28 6 2


MGO Resin # 30 6 3

3.7.1 Mechanism for the synthesis of melamine glyoxylated resin

The scheme 6 involved following three steps in the synthesis of glyoxylated

melamine based resin.

161

3.7.1.1 Glyoxylation

Amino functionality of melamine (42), nucleophilically attack on the carbonyl

group of glyoxal (43) in the basic media to produce mono- (44) , di- (45), tri- (46), tetra-

(47) , penta- (48) and hexa (49) glyoxylated derivatives of melamine. Degree of

glyoxylation depends upon the mole ratio of glyoxal to melamine. The parameters like

mole ratio of reactants, reaction time and pH affect on the glyoxylation step. Glyoxal to

melamine ratio ratio was varied from 1 to 6. Synthesis of different glyoxylated

derivatives of melamine has been shown in scheme 6.1.

H2N

N NH2 OH

42 43 44 45

46 47 OH

OH OH

O O

48 49

Scheme 6.1. Glyoxylation of melamine at various mole ratios

N N

N H 2

+

O H N

N

N

N H 2 N H 2

N H

O H

O

N

N

N

N N H

N O

O H

O

O H

O

O

O H

N

N

N

N H N H

N H

O H

O

O H

O

O H

O

162

3.7.1.2 Sulfonation

Glyoxylated melamine was sulfonated by sodium sulfamate (52). Sulfamic acid

(50) was first neutralized with sodium hydroxide (51) in aqueous media to form sodium

sulfamate as shown in scheme 6.2. Sulfonation of glyoxylated melamine was carried out

by sodium sulfamate to form sulfonated glyoxylated melamine derivative (53) as shown

in scheme

6.3. During sulfonation, mole ratio of sodium sulfamate to melamine was varied

from

0.5-3. Process of sulfonation is affected by reaction time, pH and temperature.

NH2 NH2

O O + NaOH O O

OH ONa

50 51 52

Scheme 6.2. Synthesis of sodium sulfamate

47 52 53

Scheme 6.3. Sulfonation of glyoxylated melamine

3.7.1.3 Condensation

During condensation, sulfonated glyoxylated monomers react with each other to

form large molecule (54) as shown in scheme 6.4. The rate of condensation is increased

in acidic media. Substantivity of glyoxylated melamine resins with collagen is

dependent on its molecular size and solubility behavior which change by changing

degree of sulfonation and G/M mole ratio.

S S

N

N

N

N H N H

N H O H

O

O H

O H

O H O N H

S O

O

ONa

N

N

N

N H N H

N H O H

O

O H O H O O

+ NH 2 SO 3 Na

163

Scheme 6.4: Condensation of monomers to form proposed polymer structure

3.8 Preparation of sulfonated melamine glutaraldehyde based resin

Sulfonated melamine glutaraldehyde based resins were prepared by following

procedure.

In a three necked flask fitted with condenser, stirrer and thermometer, 105g water

(5.83 moles), 118.92g sulfamic acid (1.22 moles), 97.60g 50% strength sodium

hydroxide (1.22 moles) were mixed to form sodium sulfamate. An amount of 51.44g

melamine (0.40 mole) was added and heated to 45oC. Afterward, 326.63g 50% strength

of glutaraldehyde (1.63 moles) was added and temperature was raised to 85±2oC to

obtain a clear resin solution. The reaction temperature was maintained for ten minutes

and then cooled to 60oC for further condensation of the resin at 60oC for 30 minutes.

The reaction mixture was allowed to cool to room temperature. The solid content of the

resin was about 45±1%.

164

Under these optimum conditions, the following set of experiments given in Table

3.8 was performed with varying mole ratios of glutaraldehyde/melamine and sodium

sulfamate/melamine.

Table 3.8: Experimental data of Melamine glutaraldehyde condensates

Sample G/M S/M

MGT # 01 3 0.5

MGT # 02 3 1

MGT # 03 3 1.5

MGT # 04 3 2

MGT # 05 3 2.5

MGT # 06 3 3

MGT # 07 4 0.5

MGT # 08 4 1

MGT # 09 4 1.5

MGT # 10 4 2

MGT # 11 4 2.5

MGT # 12 4 3

MGT # 13 5 0.5

MGT # 14 5 1

MGT # 15 5 1.5

MGT # 16 5 2

MGT # 17 5 2.5

MGT # 18 5 3

MGT # 19 6 0.5

MGT # 20 6 1

MGT # 21 6 1.5

MGT # 22 6 2

MGT # 23 6 2.5

MGT # 24 6 3

165

3.8.1 Mechanism for the synthesis of melamine glutaraldehyde resin

Synthesis of melamine glutaraldehyde condensate was described by scheme 7.1

to 7.3.


Melamine (42) reacts by nucleophilic attack on the carbonyl group of

glutaraldehyde (55) in basic media to form monohydroxy (56), dihydroxyl (57),

trihydroxy (58), tetrahydroxy (59), pentahydroxy (60) and hexahydroxy (61) derivatives

of melamine with glutaraldehyde depending upon the mole ratio of glutaraldehyde to

melamine as shown in scheme 7.1.

166

42 H2N

OH

167

Scheme 7.1: Reaction of melamine with glutaraldehyde at various mole ratios

These hydroxyl derivatives of melamine are highly reactive and self-polymerize

to form a cross linked water insoluble product. Different parameters like reaction time,

molar ratios and pH affect condensation step. In this research, melamine to

glutaraldehyde mole ratio of 1:4 was found with optimum performance.

3.8.1.2 Sulfonation

Melamine glutaraldehyde condensate was sulfonated by sodium sulfamate (52).

Sulfamic acid (50) was first neutralized with sodium hydroxide (51) in aqueous media

to form sodium sulfamate as shown in scheme 6.2. Sulfonation of Melamine

glutaraldehyde condensate was carried out by sodium sulfamate to form sulfonated

melamine glutaraldehyde condensate in monomer form as shown in scheme 7.2. During

sulfonation, mole ratio of sodium sulfamate to melamine was varied from 0.5-3. Process

of sulfonation is affected by reaction time, pH and temperature.

O O

Scheme 7.2: Sulfonation of glutaraldehyde condensed melamine

3.8.1.3 Condensation

During condensation, sulfonated melamine glutaraldehyde condensate

monomers react with each other to form large molecular structure (63) as shown in

scheme 7.3. The rate of condensation is increased in acidic media. Substantively of

N

N

N

N H N H

N H O H

O H O H

O

O

+ NH 2 SO 3 Na

58 52 62

N

N

N

N H N H

N H O H

O H O H

O

N H O H

S O O ONa

168

sulfonated melamine glutaraldehyde resins with collagen is dependent on its molecular

size and solubility behavior which change by changing degree of sulfonation and G/M

mole ratio.

H O

Scheme 7.3: Condensation of monomers to form proposed polymer structure

3.9 Physical characterization of resins

3.9.1 Estimation of solid content

Solid content of liquid resin was determined by weighing known quantity of the

resin in an empty petri dish and drying at 103-105oC for one hour as per standard

procedure [199]. Solid contents of the product were calculated on dried weight basis.

169

3.9.2 Viscosity determination

Viscosity of the synthetic resins was measured by means of Brookfield DV-I

viscometer-

LVDVE 230 [200]. Apparent viscosity was determined at 25°C temperature by

using appropriate spindle relative to the viscosity of the resin. Reading of viscometer

was noted in centipoises (cps)

3.9.3 Specific gravity

Specific gravity of liquid resins was determined by standard ASTM method

D5355 – 95, 2012 [201] in which specific gravity of liquid resins was calculated by the

ratio of weight of a unit volume of liquid resin sample to weight of a unit volume of

water at 25°C.

3.9.4 Determination of color and pH

Color of liquid resins was observed visually and pH of liquid resins was

determined by standard test method, ASTM E70 – 07 [202], in which pH of resinous

solutions was determined with the glass electrode.

3.9.5 Determination of solubility and acid sensitivity

The solubility of resins in water was determined at 10% concentration by

dissolving 10g of liquid resin in 90g of water. Acid sensitivity was measured by adding

0.1N Hydrochloric acid solution to 10% solution of liquid resin, solutions of acid

sensitive resins were precipitated and acid resistant resins tolerate addition of acid and

their solutions were not disturbed.

3.9.6 Free formaldehyde in the synthetic resin

Free formaldehyde in liquid synthetic resins was determined by using following

standard

170

method, ASTM D2194 – 02 [203].

50 ml of analytically pure sodium sulfite solution (one molar) was taken in 500

ml glass flask. Added few drops of thymolphthalein solution as an indicator. The

mixture was titrated with 0.5 molar hydrochloric acid until solution become colorless,

0.5g of synthetic resin solution was added to 25 ml of distilled water for dilution and 15

ml of sodium sulfite solution (one molar).Few drops of thymolphthalien as an indicator

were poured in the resulting mixture and titrated it against 0.5 mole/dm3 hydrochloric

acid till solution become colorless. This analysis was carried out at the end of

condensation reaction of adipic dihdydrazide with formaldehyde. Free formaldehyde

contents (CH2O %) was determined from the following equation.

Where, V = volume of HCl (cm3); c = concentration of HCl (mol/dm3); E

= equivalent weight of formaldehyde; a = weight of samples (g).

3.10 Chemical characterization of resins

3.10.1 Fourier transforms infra-red spectroscopy (FT-IR)

FT-IR technique was used as a key technique in the chemical characterization of

polymers for verification of the synthesis path. The spectra of the synthetic resins were

recorded on Fourier transform infrared (FTIR) spectrometer Bruker IFS 48. The

scanning region was 4000 cm-1 to 500 cm-1. Spectra are given in annexes section.

3.10.2 Nuclear magnetic resonance (NMR) spectroscopy

All the 1H NMR spectra were recorded in deuterated water Bruker Advance 300

MHz Spectrometer at HEJ Karachi Pakistan. The dried resin films were dissolved in

deuterated water while TMS was used as a standard. Spectra are given in annexes section.

171

3.11 Viscosity average molecular weight

The molecular weights of polymer resin samples were determined by using the

viscometery technique [205]. A general procedure was adopted for the determination of

molecular weight. Flow time of each dilution of polymer solution was noted using

Cannon Ubbelohde viscometer. The experiments were carried out at constant

temperature of 27oC ± 0.1oC. Flow time for the solvent (water) was noted by taking the

measured volume of solvent in the viscometer. Three concordant readings of flow time

were noted and averaged for achieving the maximum accuracy in the results. The

viscometer was then emptied, dried and 10 ml of resinous solution of 0.08 g/10 ml of

water concentration was taken. Again three concordant readings of flow time were

taken. The solution was then diluted to 0.07g/10 ml and the corresponding flow time

was noted again. Similarly, 0.06g/10 ml, 0.05g /10 ml, 0.04g /10 ml dilutions were made

and their flow time was noted. The corresponding viscosity average molecular weight

was measured.

Efflux time of the pure solvent is given by (to). The relative viscosity is the

viscosity of the polymer solutions to the viscosity of the pure solvent. This is done by

taking the efflux time of the polymer solution at a given concentration which is (t) and

dividing it by (to) as explained below:

Relative viscosity = Efflux time of solution

Efflux time of solvent

ηr = t/to

The specific viscosity was measured by taking the difference in the efflux times of the

solution and the pure solvent. In other words, the efflux time of the pure solvent ‘to’ was

subtracted from the efflux time of the solution‘t’ as explained below:

Specific viscosity = Efflux time of solution - Efflux time of solvent

Efflux time of solvent

ηsp = t – to

to

172

The intrinsic viscosity of the sample was determined by extrapolating graph

between the concentration and (ŋsp – lnŋr) /c2. This plot gives the value of 1/2 [ŋ] 2 at

zero.

From the flow time relative velocity (ηr), specific viscosity (ηsp) and ultimately

the

intrinsic viscosity ([η]) were calculated for the synthesized samples. Then, the

molecular weight of the polymers was determined by using Mark Houwink equation

(Allcock and Lampe, 1981).

[η] = K [M]a

Where, [η] is intrinsic viscosity, ‘M’ is the molecular mass of the polymer, ‘K’

is the characteristics of the polymer and solvent and ‘a’ is a constant and a function of

the shape of the polymer coil in the solution.

In case of melamine formaldehyde resin the value of ‘a’ is usually 0.6 and ‘K’ is

0.076. In this experiment, the values of ‘K’ and ‘a’ were based on the behavior of

homopolymers in the aqueous phase. The values of these constants depend upon the

polymer solvent interactions.

3.12 Application of resins as retanning agents

Procedure for post tanning for experimental and control processes are given in

Table 3.9. The retanning properties of sulfonated succinic dihydrazide formaldehyde

condensates, glutaric dihydrazide formaldehyde condensates, adipic dihydrazide

formaldehyde condensates, isophthalic dihydrazide formaldehyde condensates,

terephthalic dihydrazide formaldehyde condensates, sulfonated melamine glyoxylated

condensates and sulfonated melamine glutaraldehyde condensate were assessed by

comparison against leather developed by commercial retanning agent.

Table 3.9: Post-tanning recipe for processing wet blue

Process and chemicals % Duration in mints Remarks

Washing

173

Water 100 15 Drained water

Neutralization

Water 150

Sodium formate 1.5 10

Sodium bicarbonate 1 90

Adjusted pH 5.0-5.2 and

drained water

Washing

Water 200 15 Drained water

Retanning, Dyeing and Fat liquoring

Water 100

Melamine glutaraldehyde based amino

resin* 10 45

Synthetic Fatliquor 4

Semi-synthetic Fatliquor 4 60 Mixed in hot water

Acid Dye 2 30

Formic acid 1.5 4X10+20

Bath exhaustion checked

and

drained the water

Washing 100 15 Drained

The processed leathers were set twice and hooked to dry. They were conditioned and staked.

* Commercial melamine formaldehyde syntan was used for retanning control leathers

3.13 Mechanical properties of retanned leather

Leather strength has great importance in the physical assessment of leather. It

gives indication of conditions of fiber bundles. Physical measurements like tensile

strength, tear strength and elongation at break were performed to show the effects of

prepared polymers as synthetic tanning agent and to illustrate the effects of different

resins synthesized at different conditions.

3.13.1 Conditioning of leather before testing

Conditioning of the samples was carried out by following standard method IUP

3 [160].

174

Conditioning of the test piece was carried out by placing under standard conditions

as specified in Table 1. Test piece was supported to allow whole surface to get free access

of air. The test pieces were conditioned for 48 hours before testing.

Table 3.10 standard atmosphere and tolerances

Designation Temperature (oC) Relative humidity (%)

20/65 20 ±2 65 ±5

Alternative of this but not equivalent, a set of conditions might be used

23/50 23 ±2 50 ±5

3.13.2 Determination of tensile strength

Tensile testing of the leather specimens were carried out by standard procedure

IUP 6 [161].

1- Principle. A piece of test is elongated/stretched in one direction at specified

rate till the forces reach at value of predetermined or till the test specimen of

leather break.

2- Apparatus.

2.1. Tensile testing machine

2.2. A means of determining the extension of the piece of test, either by

monitoring the separation of the jaws.

2.3. Thickness gauge

2.4. press knives, capable of cutting a piece of test as shown in figure 3.1

with dimension as given in Table 3.11.

2.5. Vernier calipers, reading up to 0.1 mm.

175

Figure 3.1: Shape of test piece

Table 3.11: Dimensions of Test specimens

Designation b b1 l L1 L2 R

Large 20 40 190 100 45 10

standard 10 25 110 50 30 5

3. Sample preparation

3.1 Test pieces were cut by applying a press knife (4.4) to the grain

surface, two pieces of test specimens with longer sides parallel to backbone and

two pieces of test with the longer side perpendicular to backbone.

3.2 Test pieces were conditioned according to IUP 3.

4- Procedure.

4.1 Determination of the dimensions.

4.1.1 By using vernier calipers (4.5), width of each test piece was measured to

the nearest 0.1 mm at three positions on the grain side and three on the flesh side.

In each group of three measurements, make one at the mid-point E (as shown in

figure 1) and other two at the positions approximately mid-way between

176

midpoint E and the lines BA and DC. Standard mean of the six measurements

was taken as the width of the test piece, w.

4.1.2 Thickness of test piece was measured in accordance with IUP 4.

Measurements were taken at three positions namely the mid-point E and at

positions approximately mid-way between mid point E and the lines BA and

DC. Standard mean was taken of the three measurements as the thickness of the

test piece.

4.2 Tensile strength determination.

4.2.1 Jaws of the tensile strength testing apparatus were set. Test piece was

clamped in jaws so that the jaws edges lie along the lines BA and DC while

ensuring grain surface lies in one plane.

4.2.2 Machine was run till the test piece was broken and recorded highest

exerted force as the breaking force, F

Tensile strength was calculated in newtons per square centimeter by

using the following formula [161]

T = F

w x t

Where

F is the highest force which was recorded in Newton

w is the mean width of test piece in

centimeter t is the mean thickness of test piece

in centimeter.

177

3.13.3 Determination of percentage elongation at break

[1] Jaws of the tensile strength testing apparatus were set. Test piece was clamped

in jaws so that the jaws edges lie along the lines BA and DC while ensuring grain

surface lies in one plane

[2] Tensile test machine was run till the test piece breaks.

[3] Distance between the jaws was measured at the instant when rupture of test piece

appears. Distance was recorded as the length of the piece of test break at, L2.

The percentage elongation at break was calculated by the following formula

% Elongation = L2 – L0 X 100

L0

Where

L2 is the separation of the jaws at break

L0 is the initial separation of the jaws

3.13.4 Tear strength of retanned leathers was determined by standard procedure

of IUP 8 [162].

1- Apparatus

1. Tear testing machine –STM 566ST was used to determine the tear strength

2. Test piece holders

3. Thickness gauge specified in IUP

4. Press knife

178

2- Procedure

The apparatus was adjusted in a way so that the turn up ends of the specimen

holder became in slight contact with each other. The test piece was slipped over the

turned up ends protruded through the slot with the width of the turned ends parallel to

the straight edges of the slot. The test piece was pressed firmly into the holder

The tensile machine was run until the tearing of test piece into parts and the

maximum required force was recorded which was measured in Newton per centimeter.

3.13.5 Grain strength was determined by standard procedure IUP 9 [163].

Machine: Lastometer was used to determine grain strength.

1- Procedure: The conditioned specimen was clamped in the instrument. Its grain

surface was kept flat and its flesh surface was kept adjacent to the ball.

The distension was increased to around one fifth of millimeter per second. The

grain surface was observed for the occurrence of crack. The load and distension was

observed and the loading was continued without any delay and if the burst happened the

distension was recorded.

The distension and load at grain crack were reported and also their corresponding

values at the burst (if any) before reaching the maximum load were recorded.

3.13.6 Organoleptic properties

Organoleptic properties such as fullness and softness of leather fibers, roundness

and tightness of leather grain, and color uniformity after dying for control and

experimental crust leathers were comparatively visually evaluated. An average rating to

each functional property of the experiment was given in Figure. 2. Better property was

expressed by higher number. Fullness, grain tightness and softness of experimental

retanned leather was higher than control melamine formaldehyde retanned leather where

179

as roundness and color uniformity of retanned leathers after dying were comparable in

control and experimental leathers.

3.13.7 Free formaldehyde analysis in leather

Standard procedure of IUC 19-2 [164] was used to determine free formaldehyde

content in the leather swatches.

1- Scope

Formaldehyde content is the quantity of formaldehyde present in extracted

water of leather under specified conditions.

2- Chemicals

2.1 0.1% solution of sodium dodecylsulphonate (surfactant) was prepared by

dissolving 1g of sodium dodecylsulphonate in 1000 ml of distilled water

2.2 3 ml of glacial acetic acid, 150 g ammonium acetate and 2ml of acetyl

acetone (pentane-2, 4-dione) were dissolved in 1000ml distilled water.

This mixture is sensitive to light and was either used immediately or

stored in dark room.

2.3 3 ml of glacial acetic acid and 150 g of ammonium acetate were dissolved in

1000ml distilled water

2.4 5g of methone (dimedone = 5, 5’-Dimethyl-1, 3-cyclohexanedione) was

dissolved in 1000ml of wat.

3- Apparatus

3.1 Thermostatically controlled water bath upto 40oC±0.5oC

3.2 Thermometer over range of 20oC to 50oC with 0.1oC gradient.

3.3 Spectrophotometer (SHIMADZU UV – 1800), wavelength 412 nm

3.4 Photometric quartz cell

180

3.5 Membrane filter, polyamide, 0.45μm

3.6 Analytical weighing balance, with an accuracy upto 0.1mg

4-Preparation and standardization of formaldehyde stock solution

4.1 Reagents

4.1.1 37% strength of formaldehyde solution

4.1.2 0.05M iodine solution (12.68g of iodine dissolved in 1000ml of

distilled water along with 10.5g of potassium iodide)

4.1.3 2 M sodium hydroxide (80g of sodium hydroxide dissolved in

1000ml of distilled water)

4.1.4 1.5M sulphuric acid prepared by diluting 10ml of 18M conc.

sulphuric acid upto 120ml by distilled water

4.1.5 0.1 M sodium thiosulfate solution prepared by dissolving 24.82g

of sodium thiosulfate pentahydrate in 1 L of distilled water

4.1.6 1% starch solution prepared by dissolving 1g of starch in 100ml of

distilled water.

4.2 Quantitative determination of formaldehyde in stock solution

To prepare stock solution of formaldehyde, 5 ml of formaldehyde

solution (4.1.1) is taken in a 1000ml measuring flask, which contains 100ml

distilled water and is further filled up to mark with distilled water.

10ml of the sample is taken from this solution into 250 ml Erlenmeyer

flask and further mixed with 50ml solution of iodine (4.1.2), and sodium

hydroxide (4.1.3) is added till the solution turns yellow. It is settled for 15 min±1

min at 18oC to 26oC, and then 50ml of sulphuric acid (4.1.4) while mixing are

added.

181

After addition of 2 ml of starch solution (4.1.6), excess iodine is titrated

against sodium thiosulphate (4.1.5) until the color changes. Three separate

determinations were made. A blank reference solution is titrated in the same

way.

5- Procedure for quantitative determination of the

formaldehyde in leather 5.1 Sampling and sample

preparation

Sample was taken from leather swatch and grinded as per standard

procedure IUC 3 [206].

5.2 Formaldehyde extraction

2g of ground leather is taken in 100ml Erlenmeyer flask. 50 ml of

detergent solution (2.1) is added and glass stoppered. The flask is shaken gently

at 40oC in a hot water bath (3.1) for one hour. Warm extracted solution is filtered

immediately by vacuum through a glass fiber filter (3.5) in to a flask. Filtrate in

closed flask is cooled to room temperature of 25oC.

CFA = (Vo – V1).c1.MFA

2

CFA = Concentration of formaldehyde stock solution (mg/10 ml)

Vo = Titre of sodium thiosulphate solution for blank solution (ml)

V1 = Titre of sodium thiosulfate solution for sample solution (ml)

MFA = Molecular weight of formaldehyde (30.08g/mol)

c1 = Concentration of the thiosulfate solution (M)

182

5.3 Derivatization with acetylacetone

5ml of filtrate obtained at 5.2 was taken into a 25ml Erlenmeyer flask

and 5ml of reagent solution (2.2) was added. Flask was closed with glass stopper

and stirred for 30 minutes at a temperature of 40±1oC. The flask contents were

cooled in dark and absorbance was measured spectrophotometrically (3.3) at

wavelength of 412 nm against blank solution prepared by 5ml of detergent

solution (2.1) and 5ml reagent solution (2.2). The measured absorbance is

registered as Epr. To determine absorbance from self coloring of the filtrate

obtained at step 5.2, 5ml of filtrate (5.2) was taken in a 25 ml Erlenmeyer flask

and 5ml of solution (2.3) was added. The same method was then applied as with

the sample. The measured absorbance

was registered as Ec.

5.4 Calibration

3ml of formaldehyde stock solution obtained in 4.2 was with exactly

known amount of formaldehyde content, taken in 1000 ml volumetric flask. The

flask was filled with water upto the mark and mixed thoroughly. This was

standard solution used for calibration. The standard solution has approximate

formaldehyde content of 6µg/ml.

From this standard solution, 3, 5, 10, 15, 25 ml each are taken in a

separate 50ml flask and filled with the water. These solutions cover the range of

formaldehyde from 0.4 µg/ml to 3.0 µg/ml.

5ml of sample is pipette from these 5 solutions and mixed in a 25ml

Erlenmeyer flask with 5 ml of reagent solution (2.2). The prepared mixture is

vigorously shaken and warmed upto 40±1oC for 30 minutes.

After cooling to room temperature in dark, absorbance was measured

with a spectrophotometer (3.3) at 412 nm against blank solution prepared of 5ml

reagent solution (2.2) and 5ml of water.

183

Before measurement of absorbance, zero point of spectrophotometer was set

with blank sample, which was treated as the calibration solution. Concentration

(µg/ml) along x axis is plotted against the measured absorbance along the y-axis

in the calibration graph.

5.5 Calculations of the formaldehyde content in the leather sample

Cp = (Ep – Ee).Vo.Vf

F.W.Va

Cp = Concentration of the formaldehyde in leather sample (mg/kg)

Ep = Absorbance of the filtrate after reaction with the acetylacetone

Ee = Absorbance of filtrate (for self coloring)

Vo = Volume of elution ml (standard conditions: 50ml)

Va = Aliquot taken from filtrate (ml) (standard conditions: 5 ml)

Vf = Volume of the solution obtained at step 6.3 after derivatisation

(standard conditions: 10 ml)

F = gradient of calibration curve (y/x) in ml/ µg

W = weight of leather (g)

The standard procedure is specific for the determination of released and

free formaldehyde in leathers. The method is primarily based on colorimetric

analysis [164].

3.13.8 Scanning electron microscopic analysis

Samples from control and experimental dye crust leathers were taken from the

standard position of sampling [211]. Specimens of leather were cut with uniform

thickness and washed with acetone. They were coated with 300oA thickness of gold

184

using Ion sputtering device, Model JFC 1500, JEOL Japan. A JEOL JSM 6490

analytical scanning electron Microscope embedded with Energy dispersive X-ray

analyzer was used for analysis. Micrographs of grain and cross section of fibers were

obtained by operating SEM at high vacuum and voltage of 15 KV with higher

magnification of X500 levels.

3.13.9 Thermal analysis

Thermo gravimetric analysis was carried out by using thermo gravimetric and

differential Scanning analysis (TG/ DSC) SDT Q 600 machine of Universal V4.5A TA

instruments.

TGA was performed in a platinum pan with a neutral environment under the flow

rate of 50 mL/min of nitrogen gas. Temperature scan was carried out from ambient

temperature (25 oC) to 600 oC with a gradient of 10 oC. Weight loss of sample in percent

(%) was recorded versus change in temperature (oC).

185

CHAPTER-4

RESULTS AND DISCUSSION In the present study, novel hydrazide modified amino resins and formaldehyde free

melamine based resins were developed. Optimized molar ratios were determined by comparative

application of resins synthesized at varying molar ratios against commercial synthetic retanning

agent.

4.1 Physical properties of novel hydrazide modified

amino resins and formaldehyde free amino resins Novel hydrazide amino resins based on succinic dihydrazide, glutaric dihydrazide, adipic

dihydrazide, isophthalic dihydrazide and terephthalic dihydrazide were synthesized under various

mole ratios of reactants to produce resin with stabilized and optimum performance. Succinic

dihydrazide modified amino resins were analyzed for physical properties and results are given in

Table 4.1.

Table 4.1: Succinic dihydrazide formaldehyde condensates

186

Trials Color

pH Specific

Gravity Acid sensitivity

Solids Content

Viscosity Solubility

(%) (cp)

SDH # 01 Transparent 7.76 1.24 Sensitive 35.4 Gelling Soluble

SDH # 02 Transparent 7.75 1.25 Not Sensitive 35.6 35 Soluble



SDH # 05 Transparent 7.78 1.25 Sensitive 35.7 Gelling Partially soluble


SDH # 07 Transparent 7.74 1.27 Not Sensitive 35.3 35.8 Soluble










Glutaric dihydrazide modified amino resins were analyzed for physical properties and

results are mentioned in Table 4.2.

Table 4.2: Glutaric dihydrazide formaldehyde condensates

Trials

Color/

pH Specific


Solids Content Viscosity

Solubility

Appearance (%) (cp)

GDH # 01 0.1 7.75 1.21 Not Sensitive 32.35 22 Soluble


GDH # 03 0.3 7.79 1.24 Not Sensitive 32.54 18.5 Soluble



GDH # 06 0.2 7.78 1.26 Sensitive 32.46 Gel Partially soluble



187








Adipic dihydrazide modified amino resins were analyzed for physical properties and results are

given in Table 4.3

Table 4.3: Adipic dihydrazide formaldehyde condensates

Trials

Color/

Appearance

pH Specific

Gravity

Acid

sensitivity

Solids

Content Viscosity

Solubility

(%) (cp)

ADH # 01 Transparent 7.75 1.21 Not Sensitive 32.98 27.48 Soluble





ADH # 06 Transparent 7.78 1.26 Sensitive 32.92 72.38 at 75oC Soluble

ADH # 06 Transparent 7.73 1.24 Sensitive 32.23 Gel at 70oC Soluble



ADH # 08 Transparent 7.76 1.22 Not Sensitive 32.59 60.43 at 75oC Soluble

ADH # 08 Transparent 7.72 1.28 Not Sensitive 32.87 Gel at 40oC Soluble







188






Isophthalic dihydrazide modified amino resins were analyzed for physical properties and results are

given in table 4.4

Table 4.4: Isophthalic dihydrazide formaldehyde condensates

Trials

Color/

pH Specific


Solids Content Viscosity

Solubility

Appearance (%) (cp)

ISPDH # 01 Transparent 7.75 1.38 Sensitive 40.12 Gel Insoluble



ISPDH # 04 Transparent 7.77 1.37 Not Sensitive 40.26 55.7 Soluble



ISPDH # 07 Transparent 7.75 1.36 Not Sensitive 40.89 35.6 Insoluble


















189











Terephthalic dihydrazide modified amino resins were analyzed for physical properties and results

are given in table 4.5

Table 4.5: Terephthalic dihydrazide formaldehyde condensates

Trials Color/

pH Specific

Gravity

Acid

sensitivity

Solids Content


Appearance (%) (cp)

TPDH # 01 Transparent 7.75 1.38 Sensitivity 40.05 Gel Insoluble



TPDH # 04 Transparent 7.72 1.37 Not Sensitive 40.02 58.8 Soluble



TPDH # 07 Transparent 7.79 1.35 Sensitivity 40.07 Precipitation insoluble

TPDH # 08 Transparent 7.74 1.33 Not Sensitive 40.05 Gel Insoluble

TPDH # 09 Transparent 7.75 1.32 Not Sensitive 40.04 Gel Soluble

TPDH # 10 Transparent 7.78 1.39 Not Sensitive 40.01 Gel Soluble

TPDH # 11 Transparent 7.73 1.34 Sensitivity 40.02 Precipitation Soluble




TPDH # 15 Transparent 7.76 1.36 Sensitivity 40.03 Cured Gel Insoluble





190
















Formaldehyde free, Melamine glyoxylated based amino resins were analyzed for physical

properties and results are given in table 4.6

Table 4.6: Melamine Glyoxylated condensates

Trials Color/

pH Specific

Gravity

Acid

sensitivity

Solids

Content Viscosity

Solubility

Appearance (%) (cp)

MGO Resin # 01 Solid gel 7.75 1.43 Sensitive 45.01 Gel Insoluble

MGO Resin # 02 Viscous solution 7.71 1.48 Sensitive 45.05 Viscous Soluble

MGO Resin # 03 Clear Solution 7.70 1.47 Sensitive 45.09 60.5 Soluble

MGO Resin # 04 Clear solution 7.78 1.42 Sensitive 45.04 45.7 Soluble

MGO Resin # 05 Slightly turbid solution 7.76 1.45 not sensitive 45.01 19.8 Soluble

MGO Resin # 06 Turbid solution 7.74 1.41 Sensitive 45.08 18 Soluble

MGO Resin # 07 Solid gel 7.79 1.46 Sensitive 45.02 Gel Insoluble

MGO Resin # 08 Viscous solution 7.73 1.47 Sensitive 45.07 Viscous Soluble

MGO Resin # 09 Clear Solution 7.77 1.43 Sensitive 45.06 75 Soluble

MGO Resin # 10 Clear solution 7.71 1.45 Sensitive 45.09 65 Soluble

MGO Resin # 11 Clear Solution 7.72 1.49 Sensitive 45.04 20.8 Soluble

MGO Resin # 12 Clear solution 7.78 1.41 Not sensitive 45.01 17 Soluble

191

MGO Resin # 13 Viscous gel 7.76 1.47 Sensitive 45.06 538 Partially soluble

MGO Resin # 14 Clear Solution 7.73 1.42 Sensitive 45.07 300 Soluble

MGO Resin # 15 Clear solution 7.77 1.49 Sensitive 45.02 235 Soluble

MGO Resin # 16 Clear Solution 7.71 1.44 sensitive 45.03 120 Soluble

MGO Resin # 17 Clear solution 7.76 1.43 Not sensitive 45.05 24.9 Soluble


MGO Resin # 19 Viscous solution 7.73 1.45 Sensitive 45.09 86 Soluble

MGO Resin # 20 Clear solution 7.79 1.41 Sensitive 45.02 51.6 Partially soluble


MGO Resin # 22 Clear solution 7.78 1.42 Not sensitive 45.06 19 Soluble






MGO Resin # 28 Clear solution 7.76 1.45 not sensitive 45.05 15.72 Soluble



Formaldehyde free, melamine glutaraldehyde based amino resins were analyzed for physical

properties and results are given in table 4.7.

Table 4.7: Melamine Glutaraldehyde condensates

Trials Color/

pH Specific


Solids Content


Appearance (%) (cp)

MGT Resin # 01 Gel 7.75 1.40 Sensitive 45.02 Gel Insoluble


MGT Resin # 03 Clear Solution 7.78 1.43 Sensitive 45.09 189 Soluble

MGT Resin # 04 Clear solution 7.71 1.45 Sensitive 45.04 98 Soluble

MGT Resin # 05 Clear Solution 7.70 1.47 Not sensitive 45.05 42 Soluble

MGT Resin # 06 Clear solution 7.72 1.42 Not sensitive 45.07 33 Soluble



MGT Resin # 09 viscous solution 7.79 1.48 Sensitive 45.08 Viscous Soluble

192

MGT Resin # 10 Viscous solution 7.72 1.43 Not sensitive 45.01 Viscous Soluble





MGT Resin # 15 Viscous solution 7.76 1.43 Sensitive 45.04 Viscous Soluble

MGT Resin # 16 viscous solution 7.78 1.49 Not sensitive 45.07 viscous Soluble




MGT Resin # 20 Clear Solution 7.77 1.48 Sensitive 45.01 1600 Soluble





4.2. Chemical characterization of Novel amino resins

and formaldehyde free amino resins Stabilized novel hydrazide modified amino resins and formaldehyde free amino resins

synthesized at different mole ratios with different molecular weights were evaluated by FTIR and

Proton NMR technique. Results of proton NMR and FTIR are given in section 4.2.1.

4.2.1 Chemical characterization of SDH series

Stabilized succinic dihydrazide based amino resins synthesized at different mole ratios with

different molecular weights were evaluated by FTIR and Proton NMR technique as per following

data

SDH # 01; FTIR (cm-1): 3415 (O-H), 3242 (N-H), 2925 (C-H), 1643 ( C=O, Amide), 1584

(C=C str), 1411 (CH2 ben), 1037 (C-O). H1 NMR: 3.852ppm (4H s), 4.0ppm (2H m)

6.18ppm (NH dd), 7.37 ppm (NH dd) , 9.3ppm (OH br s)

193


(C=C str), 1411 (CH2 ben), 1051 (C-O). H1 NMR: 2.394 ppm (4H s), 3.99 ppm (2H m) 6.54ppm

(NH d) , 6.99 ppm (NH d) , 9.3ppm (OH br s)


(C=C str), 1415 (CH2 ben), 1035 (C-O). H1 NMR: 2.351 ppm (4H s), 3.82 ppm (2H dd ), 6.49 ppm

(NH d) , 6.93 ppm (NH d) , 9.3ppm (OH br s)

SDH # 04; FTIR (cm-1): 3427 (O-H), 3271 (N-H), 2922 (C-H), 1637 (C=O, Amide), 1584

(C=C str), 1415 (CH2 ben), 1035 (C-O). H1 NMR: 2.42 ppm (4H s), 3.93 ppm (2H d ), 6.49 ppm

(NH

d) , 6.94 ppm (NH d) , 9.3ppm (OH br s).


(C=C str), 1415 (CH2 ben), 1180(S=O), 1035 (C-O). H1 NMR: 2.74 ppm (4H s), 3.85 ppm (2H

m), 6.40 ppm (NH dd), 6.97 ppm (NH dd), 9.215 (1H br s) 9.9 ppm (OH br s)


(C=C str), 1411 (CH2 ben), 1182 (S=O), 1039 (C-O). H1 NMR: 2.47 ppm (4H s), 3.81 ppm (2H

m), 6.51 ppm (NH d) , 6.95 ppm (NH d) , 9.3ppm (OH br s)



d), 6.485 ppm (NH dd) , 6.93 ppm (NH dd) , 9.3ppm (OH br s)



t), 6.48 ppm (NH dd) , 6.935 ppm (NH dd) , 9.3ppm (OH br s)

194



t),

6.49 ppm (NH dd) , 6.93 ppm (NH dd) , 9.3ppm (OH br s).

SDH # 10; 3591 (O-H), 3317 (N-H), 2883 (C-H), 1712 (C=O, Amide), 1494 (C=C str),

1309 (CH2 ben), 1230 (S=O), 1025 (C-O). H1 NMR: 2.64 ppm (4H s), 3.81 ppm (2H d), 6.49 ppm

(NH dd) , 6.94 ppm (NH dd) , 8.27 (1H s ) 9.9 ppm (OH br s)


1413 (CH2 ben), 1184 (S=O), 1033 (C-O). H1 NMR: 2.40 ppm (4H s), 3.98 ppm (2H m ), 6.57

ppm (NH dd) , 7.01 ppm (NH dd) , 8.33 (1H s ) 9.9 ppm (OH br s)


1413 (CH2 ben), 1186 (S=O), 1033 (C-O). H1 NMR: 2.41 ppm (4H s), 3.90 ppm (2H m), 6.62 ppm

(NH dd), 7.05 ppm (NH dd), 8.38 (1H s) 9.4 ppm (OH br s)


1413

(CH2 ben), 1184 (S=O), 1033 (C-O). H1 NMR: 2.41 ppm (4H s), 3.755 ppm (2H m), 6.465

ppm (NH dd) , 6.92 ppm (NH dd) , 8.25 (1H s ) 9.4 ppm (OH br s)


1413


ppm (NH dd), 6.92 ppm (NH dd), 8.31 (1H s ) 9.4 ppm (OH br s)


1413

195


ppm (NH d) , 6.95 ppm (NH d) , 8.28 (1H s ) 9.4 ppm (OH br s)


1355 (CH2 ben), 1211 (S=O), 1025 (C-O). H1 NMR: 2.41 ppm (4H s), 3.86 ppm (2H m), 6.52 ppm

(NH d) , 6.96 ppm (NH d) , 8.28 (1H s ) 9.4 ppm (OH br s)

The infrared spectra of the synthesized SDH amino resins revealed absorption bands due

to presence of stretching and bending vibrations of functional groups such as O-H,N-H, C-H, C=O,

C=C, C=N, SO3H, and C-O at 3396-3738, 3228-3271, 2881-2925, 1641-1712, 1494-1544,

13091415, 1182-1230, 1025-1045 cm-1 respectively. Specifically speaking, using FTIR spectrum

of SDH-1 to SDH-16 a broad band is observed in the range 3500-3750 cm-1. In resins SDH-1,

SDH-3, SDH-8-16, the broad band is lowered from its normal absorption frequency due to

Hbonding in resins and in SDH-2, SDH-7, O-H stretchings are at their normal frequencies

representing that strength of O-H bond. N-H stretching absorption bands are seen in range

32283271, revealing the presence of extended H-bonding. A peak is observed in the range 1637-

1712 cm-1 which is due to C=O functionality of SDH resins which is very prominent peak in all

resins. The absorption bands at 1510-1584cm-1 depicted the presence of C=C stretching vibrations

formed due to tautomerism in the resins and due to conjugation, C=O peaks are shifted to smaller

wave numbers which decrease the strength of double bonds. Peaks in the range 1355- 1415cm-1

are due to CH2 out of plane bending vibrations.

In all SDH resins there is a peak in the range at 2829-2927 cm-1 is due to CH2 stretching

vibrations of succinic dihydrazide. It has been observed that the peak in the range 1180-1230 cm-

1 is due to S=O bond in all resins produced due to sulfonation of resins and this peak is

more prominent in resins SDH-1, SDH-5, SDH-6, SDH-11-SDH-15 might be due to formation

of polymers of lower molecular weight and more sulfonated chain ends are obtained. Due to the

CO functionality present in all SDH resins, there is a peak at 1025-1051 cm-1 which shows that

ether as well as primary alcoholic functionality is present.

196

The 1H-NMR spectrum of SDH-1-SDH-15 showed 4H singlet peaks 2.34-2.71 ppm due to

CH2 methylene protons present in the repeat unit of succinic dihydrazide and 2H multiplet peak at

3.75-4.0 ppm due to two methylene protons adjacent to carbonyl groups and ether linkage. At

position 6.18-6.62 and 6.92-7.37 ppm two doublet of doublet peaks are present which confirm the

presence of amide N-H groups present in all repeat units of succinic dihydrazide monomers present

in all SDH resins and these downfield due to neighboring carbonyl functionalities and so they

appear at 6.40-7.37 ppm.. In SDH-5 one group of doublet peaks is shifted upfield due to high

electron density around nitrogen atom and downfield shift is seen in resin SDH-12 due to low

electron density around nitrogen atom. All these resins are materials of a series where difference

arises in degree of polymerization, which depends upon the ratio between monomers. In case of

SDH-1, SDH-5 , SDH-11, SDH-12 and SDH-13, polymers of higher molecular weights are

formed, in their spectra, peak intensity is 40-45 times higher than NH amide peaks, which is

indication of polymerization and intensity is different in different cases showing the difference in

the molecular weights of polymers. Methylene protons adjacent to oxygen become singlet in resins

where amide NH protons involved more in hydrogen bonding and methylene protons cannot sense

the hydrogens and multiplet peaks are seen for resins where less hydrogen bonding occurs, and

less cross linking occurs. FTIR and 1H NMR spectra of optimized SDH resin # 03 are given in

figures 4.52 and 4.53 in annexes.

4.2.2 Chemical characterization of GDH series

Stabilized glutaric dihydrazide based amino resins synthesized at different mole ratios with

different molecular weights were evaluated by FTIR and Proton NMR technique and data is given

GDH # 01; FTIR (cm-1): 3724 (O-H), 3103 (N-H), 2925 (C-H), 1643 ( C=O, Amide),

1504 (C=C str), 1415 (CH2 ben), 1080 (C-O). H1 NMR: 2.11 ppm (2H pentet), 2.20 ppm (4H

triplet), 3.78 ppm (2H triplet), 6.49 (NH doublet) 6.95 ppm (NH dd).


1554 (C=C str), 1415 (CH2 ben), 1193(S=O), 1080 (C-O). H1 NMR: 1.72 ppm (2H br s), 2.12 ppm

(4H br s ), 3.93 ppm (2H singlet), 6.51 (NH doublet) 6.95 ppm (NH d).

197



(4H br s ), 3.93 ppm (2H singlet), 6.55 (NH doublet) 6.99 ppm (NH d).



(4H br s ), 3.95 ppm (2H m), 6.57 (NH doublet) 6.98 ppm (NH d).



(4H br s ), 3.95 ppm (2H m), 6.59 (NH doublet) 7.0 ppm (NH d).


1542 (C=C str), 1451 (CH2 ben), 1148 (S=O), 1037 (C-O). H1 NMR: 2.11 ppm (2H pentet), 2.20

ppm (4H triplet), 3.81 ppm (2H triplet), 6.49 (NH d) 6.95 ppm (NH d).


1541 (C=C str), 1452 (CH2 ben), 1182 (S=O), 1039 (C-O). H1 NMR: 1.75 ppm (2H br s), 2.16

ppm (4H br s ), 3.95 ppm (2H s), 6.52 (NH d) 6.95 ppm (NH d).


1541 (C=C str), 1454 (CH2 ben), 1182 (S=O), 1039 (C-O). H1 NMR: 1.77 ppm (2H br s), 2.12

ppm (4H br s ), 3.90 ppm (2H s), 6.55 (NH d) 6.99 ppm (NH d).

GDH # 09; FTIR (cm-1): 3562 (O-H), 3271 (N-H), 3034 (C-H), 1651 (C=O, Amide), 1543

(C=C str), 1454 (CH2 ben), 1180 (S=O), 1041 (C-O). H1 NMR: 1.78 ppm (2H br s), 2.13 ppm (4H

br s ), 3.91 ppm (2H s), 6.55 (NH d) 6.99 ppm (NH d).



br s ), 3.83 ppm (2H s), 6.55 (NH d) 6.99 ppm (NH d).

198



br s ), 3.83 ppm (2H m), 6.52 (NH d) 6.95 ppm (NH d).



br s), 3.84 ppm (2H s), 6.53 (NH d) 6.95 ppm (NH s).



br s ), 3.97 ppm (2H m), 6.56 (NH d) 6.98 ppm (NH s).



br s ), 3.99 ppm (2H m), 6.58 (NH br s)



br s ), 3.97 ppm (2H m), ), 6.57 (NH d) 6.99 ppm (NH s).

The infrared spectra of the synthesized GDH amino resins showed absorption bands due to

OH,N-H, C-H, C=O, C=C, C=N, SO3H, and C-O stretching and bending vibrations at 3500-3750,

3200-3250, 2925-3100, 1643-1676, 1542-1558, 1148-1208, 1027-1080 cm-1 respectively.

Specifically speaking, using FTIR spectrum of GDH-1 to GDH-15 a broad band is observed

in the range 3500-3750 cm-1 which is due to less H-bonding of OH groups present in the

synthesized polymers. This broad band is masking the peaks of N-H functionality. A peak is

observed in the range 1643-1676 cm-1 which is due to C=O functionality of GDH resins. The

absorption bands at 1504-1556cm-1 depicted the presence of C=C stretching vibrations in the

resins. These peaks are shifted to smaller wave numbers due to extended conjugation which

199

decrease the strength of double bonds. Peaks in the range 1408- 1484cm-1 are due to CH2 out of

plane bending vibrations.

In GDG-1, GDH-2, GDH-11, GDH-13 and GDH-15 resins there is a conspicuous peak in

the range at 2343-2355 cm-1 is due to larger content of oligomers where N=C=O functionality is

introduced due to resonance of electrons from nitrogen to carbonyl carbon, which result into IR

absorption at this position. It has been observed that the peak in the range 1148-1206 cm-1 is due

to S=O bond in resins GDH-7-GDH-10, where ratio of formaldehyde to glutaric dihydrazide is 2,

might to due to formation of polymers of lower molecular weight and more sulfonated chain ends

are obtained. When ratio between formaldehyde and glutaric dihydrazide is 3 then more

polymerization occurs and there are less chains with sulfonated ends and so the prominence of the

above said peak is vanished in resins from GDH-11- GDH-15.

The 1H-NMR spectrum of GDH-1-GDH-15 showed 2H pentet peaks 1.71-2.11 ppm due to

CH2 methylene protons present in the repeat unit of glutaric dihydrazide and 4H triplet peak at

2.112.25ppm in the TMS four methylene protons adjacent to carbonyl groups. A broad singlet is

observed at 2.47-2.55 ppm because of O-H groups present at the end of all GDH resins. At range

3.78-3.97 ppm multiplet peak is observed due to CH2 group adjacent to oxygen atom present in the

repeat unit of resins. Two sets of doublet peaks are seen at 6.52-6.58 and 6.95-7.00 ppm in all these

resins GDH-1 to GDH-15. All these resins are materials of a series where difference arises in

degree of polymerization, which depends upon the ratio between monomers. In case of GDH3 and

GDH-4 resins, peak intensity is 40 -45 times higher than NH amide peaks, which is indication of

polymerization and intensity is different in different cases showing the difference in the molecular

weights of polymers. In case of GDH-2 –GDH-5, triplet peak at 1.71-2.11ppm has changed into

broad singlets due to higher degree of polymerization. Similar is the case for peaks 2.12-2.25 in

resins GDH-2-GDH-7. While CH2 peaks adjacent to oxygen become singlet in resins where amide

NH protons involved more in hydrogen bonding and methylene protons cannot sense the

hydrogens and multiplet peaks are seen for resins where less hydrogen bonding occurs, and less

cross linking occurs. NH peaks are low field due to neighboring carbonyl functionalities and so

they appear at 6.52-7.00ppm. FTIR and 1H NMR spectra of optimized GDH resin # 09 are given

in figures 4.54 and 4.55 in annexes.

200

4.2.3 Chemical characterization of ADH series

Stabilized adipic dihydrazide based amino resins synthesized at different mole ratios with

different molecular weights were evaluated by FTIR and Proton NMR technique and data is given

ADH # 01; FTIR (cm-1): 3515 (O-H), 3246 (N-H), 2935 (C-H), 1658 ( C=O, Amide),

1371 (CH2 ben), 1193 (S=O), 1041 (C-O).H1 NMR: 1.717ppm (4H t), 2.069 ppm (4H t), 2.11ppm

(OH t), 6.69 ppm (NH d), 7.18 ppm (NH d).

ADH # 02; FTIR (cm-1): 3439 (N-H), 2937 (C-H), 1653 ( C=O, Amide), 1339 (CH2 ben),

1195

(S=O), 1033 (C-O). H1 NMR: 1.476 ppm (4H br s), 2.115 ppm (4H br s), 3.86ppm (2H p)

2.25ppm (OH br), 6.57 ppm (NH dd), 7.01 ppm (NH dd).


1365 (CH2 ben), 1195 (S=O), 1043 (C-O). H1 NMR: 1.478 ppm (4H br s), 2.116 ppm (4H br s),

3.94ppm (2H dd) 2.24ppm (OH br), 6.55 ppm (NH d), 6.96 ppm (NH d).



3.81-3.98 ppm (2H dq) 2.21ppm (OH br), 6.54 ppm (NH dd), 6.98 ppm (NH dd).



3.85ppm (2H s) 2.14ppm (OH br), 6.53 ppm (NH dd), 6.96 ppm (NH dd).



3.91ppm (2H dd) 2.12ppm (OH br), 6.52 ppm (NH d), 6.96 ppm (NH d).

201



3.88ppm (2H p) 2.48ppm (OH br), 6.55 ppm (NH dd), 6.99 ppm (NH dd).

ADH-08; FTIR (cm-1): 3541 (O-H), 3332 (N-H), 2941 (C-H), 1647 ( C=O, Amide), 1339

(CH2 ben), 1226 (S=O), 1058 (C-O). H1 NMR: 1.461 ppm (4H br s), 2.095 ppm (4H br s), 3.81ppm

(2H s) 2.48ppm (OH br), 6.55 ppm (NH dd), 6.99 ppm (NH dd).


(CH2 ben), 1226 (S=O), 1058 (C-O). H1 NMR: 1.476 ppm (4H br s), 2.14 ppm (4H br s), 3.96 ppm



(CH2 ben), 1226 (S=O), 1060 (C-O). H1 NMR: 1.465 ppm (4H br s), 2.090 ppm (4H br s), 4.09

ppm (2H s) 2.23ppm (OH br), 6.52 ppm (NH dd), 6.965 ppm (NH dd).


(CH2 ben), 1226 (S=O), 1060 (C-O). H1 NMR: 1.473 ppm (4H br s), 2.16 ppm (4H br s), 4.22 ppm


ADH-13; FTIR (cm-1): 3728 (O-H), 3348 (N-H), 2997 (C-H), 1651 (C=O, Amide), 1328




(CH2 ben), 1111 (S=O), 971 (C-O). H1 NMR: 1.454 ppm (4H br s), 2.15 ppm (4H br s), 3.84ppm

(2H p) 2.25ppm (OH br), 6.525 ppm (NH dd), 6.96 ppm (NH dd).




202

The FTIR spectra of the synthesized ADH amino resins exhibited absorption bands owing

to existence of stretching and bending vibrations of functional groups such as O-H,N-H, C-H,

C=O, C=C, C=N, SO3H, and C-O at 3439-3728, 3346-3348, 2928-2999, 1639-1678, 1328-1377,

11111226, 971-1074 cm-1 respectively. Specifically speaking, using FTIR spectrum of ADH-1 to

ADH-13 a broad band is observed in the range 3439-3728 cm-1. In resins ADH-4, ADH-5, ADH9,

ADH-10, ADH-12, ADH-13, ADH-14, and ADH-15 the absorption band is too much broad due

to H-bonding in resins and is masking N-H stretchings. N-H stretching absorption bands are seen

in range 3346-3348, revealing normal stretching frequency of secondary amines. A peak is

observed in the range 1639-1678 cm-1 which is due to C=O functionality of ADH resins and is very

prominent peak in all resins. In ADH-8, ADH -9, and ADH-10, the stretching frequency of C=O

group is much lowered than normal amide bonds, due to resonance of electrons from nitrogen of

hydrazide which result in the deficiency of carbonyl bond strength and these peaks are shifted to

smaller wave numbers. Peaks in the range 1328-1377 cm-1 are due to CH2 out of plane bending

vibrations.

In all ADH resins there is a peak in the range at 2928-2999 cm-1 due to CH2 stretching

vibrations present in monomers as well as polymers. It has been observed that the peak in the range

11111226cm-1 is due to S=O bond in all resins produced due to sulfonation of resins and this peak

is prominent in all resins ADH, due to formation of polymers of lower molecular weight and more

sulfonated chain ends are obtained. Due to the C-O functionality present in all ADH resins, there

is a peak at 971-1074 cm-1 which shows that ether as well as primary alcoholic functionality is

present.

The 1H-NMR spectrum of ADH -1- ADH -15 showed 4H singlet peaks at 1.453-1.717

ppm due to CH2 methylene protons present in the repeat unit of adipic dihydrazide and 4H broad

singlet peak at 2.090-2.17 ppm due to CH2 protons. At position 3.81-4.225 ppm peaks are to

methylene protons in the monomeric repeat units adjacent to ether linkage and 2.12- 2.43 ppm

singlet peaks are present which confirm the presence of amine O-H groups present in all ends of

polymeric molecules present in all ADH resins. At 6.52-6.89 ppm and 6.95- 7.18 ppm double

doublet peaks are present and are upfield due to high electron densities around these amine

203

hydrogens and so they appear upfield. In ADH-2 to ADH-15 one group of doublet peaks is shifted

upfield due to high electron density around nitrogen atom and downfield shifts are seen in resin

ADH-1, due to low electron density around nitrogen atom. All these resins are materials of a series

where difference arises in degree of polymerization, which depends upon the ratio between

monomers.

In all ADH -1 to ADH -15 resins, polymers of higher molecular weights are formed, here

peak intensity is 50-60 times higher than NH amide peaks, which is indication of polymerization

and intensity is different in different cases showing the difference in the molecular weights of

polymers. Methylene protons adjacent to oxygen become singlet in resins where amide NH protons

involved more in hydrogen bonding and methylene protons cannot sense the hydrogens and

multiplet peaks are seen for resins where less hydrogen bonding occurs, and less cross linking

occurs. FTIR and 1H NMR spectra of optimized ADH resin # 02 are given in figures 4.56 and 4.57

in annexes.

4.2.4 Chemical characterization of ISPDH series

Stabilized isophthalic dihydrazide based amino resins synthesized at different mole ratios

with different molecular weights were evaluated by FTIR and Proton NMR technique and data is

given

ISPDH # 04; FTIR (cm-1): 3574 (O-H), 3250 (N-H), 3057 (C-H), 1678( C=O, Amide),

1531(C=C str), (1049(C-O). H1 NMR: 3.95 ppm (4H s), 4.250 ppm (2H t), 6.69 ppm (NH d),

7.18 ppm (NH d) , 7.44-7.995ppm (3H m).

ISPDH # 05; FTIR (cm-1): 3580 (O-H), 3234 (N-H), 3070 (C-H), 1670( C=O,

Amide),1539 (C=C str),1465 (CH2 ben), 1047(C-O). H1 NMR: 4.01 ppm (4H s), 4.27 ppm (2H t),

6.69 ppm (NH d) , 7.18 ppm (NH d) , 7.24-7.84 ppm (3H m).

204

ISPDH # 06; FTIR (cm-1): 3558 (O-H), 3238.48 (N-H), 3074.53 (C-H), 1662.64( C=O,

Amide),1539.20 (C=C str),1463.97 (CH2 ben), 1051(C-O), 1199.72 (SO3H) H1 NMR: 4.05 ppm

(4H s), 4.34 ppm (2H t), 6.69 ppm (NH d) , 7.18 ppm (NH d) , 7.50-8.04 ppm (3H m).

ISPDH # 13; FTIR (cm-1): 3562 (O-H), 3236 (N-H), 3051 (C-H), 1666 ( C=O,

Amide),1537 (C=C str),1467 (CH2 ben), 1051(C-O). H1 NMR: 4.07 ppm (4H s), 4.36 ppm (2H t),

6.69 ppm (NH d) , 7.18 ppm (NH d) , 7.38-8.03 ppm (3H m).


Amide),1533 (C=C str),1471 (CH2 ben), 1049 (C-O). H1 NMR: 3.96 ppm (4H s), 4.26 ppm (2H

t), 6.69 ppm (NH d) , 7.18 ppm (NH d) , 7.44-7.95 ppm (3H m).
















205

ISPDH # 34; FTIR (cm-1): 3631 (O-H), 3190 (N-H), 3045 (C-H), 1681( C=O,


t), 6.69 ppm (NH d), 7.18 ppm (NH d), 7.48-7.99 ppm (3H m).

The FTIR spectra of the synthesized ISPDH amino resins exhibited absorption bands owing




of ISPDH-4 to ISPDH-34 a broad band is observed in the range 3555-3641cm-1. In all resins

ISPDH-4 to ISPDH-34, the broad band is present at its normal absorption frequency and N-H

stretchings are lowered from their normal frequencies representing that hydrogen bonding

involved in intermolecularly intangled chains of amino resins and are present in the range

31803250 cm-1. A peak is observed in the range 1666-1681cm-1 which is due to C=O functionality

of

ISPDH resins and is very prominent peak in all resins and are present at their normal

frequency.

The absorption bands at 1531-1539cm-1 depicted the presence of C=C stretching vibrations

formed due to tautomerism in the resins and due to conjugation, which result in the deficiency of

carbonyl bond strength and these peaks are shifted to smaller wave numbers. Peaks in the range

1425-1471cm-1 are due to CH2 out of plane bending vibrations.

In all ISPDH resins there is a peak in the range at 3010-3070 cm-1 due to CH stretching


1197-1268 cm-1 is due to S=O bond in all resins produced due to sulfonation of resins and this

peak is prominent in all resins ISPDH, due to formation of polymers of lower molecular weight

and more sulfonated chain ends are obtained. Due to the C-O functionality present in all ISPDH

resins, there is a peak at 1047-1051 cm-1 which shows that ether as well as primary alcoholic

functionality is present.

206

The 1H-NMR spectrum of ISPDH-4 to ISPDH -34 represented 4H singlet peaks at 3.95-

4.08 ppm due to CH2 methylene protons present in the repeat unit of isophorone dihydrazide and

1H singlet peak at 4.22-4.32 ppm due to OH protons. At position 6.69 ppm and 7.18 ppm doublet

peaks are present which confirm the presence of amine N-H groups present in all repeat units of

isophorone dihydrazide monomers present in all ISPDH resins and are low field due to low electron

densities around these amine hydrogens and so they appear low field. In all ISPDH resins the peaks

of amide protons are seen at the same positions which confirm the integrity of resins of

comparative molecular weights formed. All these resins are materials of a series where difference

arises in degree of polymerization, which depends upon the ratio between monomers. In all

ISPDH-4 to ISPDH-34, resins polymers of higher molecular weights are formed, where peak

intensity is 40-50 times higher than NH amide peaks, which is indication of polymerization and

intensity is different in different cases showing the difference in the molecular weights of

polymers. Methylene protons adjacent to oxygen become singlet in resins where amide NH protons

involved more in hydrogen bonding and methylene protons cannot sense the hydrogens and

multiplet peaks are seen for resins where less hydrogen bonding occurs, and less cross linking

occurs. FTIR and 1H NMR spectra of optimized ISPDH resin # 06 are given in figures

4.58 and 4.59 in annexes.

4.2.5 Chemical characterization of TPDH series

Stabilized terephthalic dihydrazide based amino resins synthesized at different mole ratios


given

TPDH # 02; FTIR (cm-1): 3612 (O-H), 3269 (N-H), 3197 (C-Hstr), 1714 ( C=O, Amide),

1670, 1533, 1494 (C=C str), 1112 (S=O), 1049 (C-O). 1H NMR-D2O: 3.734 ppm (1H br s), 3.916

ppm (4H br s), 4.16 ppm (2H s) 7.61 ppm (4H m).




207






ppm (4H br s), 4.00 ppm (2H s) 7.53 ppm (4H t).

TPDH # 06; FTIR (cm-1): 3606 (O-H), 3201 (N-H), 3014 (C-Hstr), 1710 (C=O, Amide),

1670,

1547, 1470 (C=C str), 1215 (S=O), 1049 (C-O). 1H NMR-D2O: 3.75 ppm (2H br s), 3.911

ppm (4H br s), 4.206 ppm (2H s) 7.656 ppm (4H s).


1662,


ppm (4H br s), 4.278 ppm (2H s) 7.56 ppm (4H sep).



ppm

(4H br s), 4.215 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.56 ppm (4H br s),



ppm (4H br s), 4.303 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.50 ppm (4H br m),


1662,

208


ppm (4H br s), 4.314 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.60 ppm (4H br m),



ppm (4H br s), 4.21 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.75 ppm (4H br m).



ppm (4H br s), 4.15 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.71 ppm (4H br m).

TPDH # 14; FTIR (cm-1): 3604 (O-H), 3196 (N-H), 3012 (C-H str), 1714 (C=O, Amide),


ppm (4H br s), 4.15 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.70 ppm (4H br s).



ppm (4H br s), 4.32 ppm (2H s), 6.64 ppm (NH d), 7.14 ppm (NH d), 7.55 ppm (4H, m).










209




The FTIR spectra of the synthesized TPDH amino resins exhibited absorption bands owing



14311671, 1405-1438, 1112-1272, 1047-1057 cm-1 respectively. Specifically speaking, using

FTIR spectrum of TPDH-2 to TPDH-34 a broad band is observed in the range 3597-3631cm-1. In

resins TPDH-5 and TPDH-10 the broad band is lowered from its normal absorption frequency due

to H-bonding in resins and in all other TPDH O-H stretchings are at their normal frequencies

representing that less hydrogen bonding in chains of amino resins. N-H stretching absorption

bands are seen in range 3196-3271, revealing normal stretching frequency of secondary amines. A

peak is observed in the range 1705-1715 cm-1 which is due to C=O functionality of TPDH resins

and is very prominent peak in all resins. The absorption bands at 1431- 1671cm-1 depicted the

presence of C=C stretching vibrations formed due to tautomerism in the resins and due to

conjugation, which result in the deficiency of carbonyl bond strength and these peaks are shifted

to smaller wave numbers. Peaks in the range 1405-1438cm-1 are due to CH2 out of plane bending

vibrations.

In all TPDH resins there is a peak in the range at3001-3195 and 2939-2946cm-1 due to CH

(ArH) and CH2 stretching vibrations present in monomers as well as polymers. It has been observed

that the peak in the range 1112-1272 cm-1 is due to S=O bond in all resins produced due to

sulfonation of resins and this peak is prominent in all resins TPDH, due to formation of polymers

of lower molecular weight and more sulfonated chain ends are obtained. Due to the CO

functionality present in all TPDH resins, there is a peak at 1047-1057 cm-1 which shows that ether

as well as primary alcoholic functionality is present.

The 1H-NMR spectrum of TPDH -2 to TPDH -34 showed 4H singlet peaks 3.916-4.10

ppm due to CH2 methylene protons present in the repeat unit of melamine dihydrazide and 1H

210

broad multiplet peak at 3.61-3.75 ppm due to OH protons. At position 4.15-4.32 ppm peaks are to

methylene protons in the monomeric repeat units adjacent to ether linkage and 6.53-6.64 ppm

doublet peaks are present which confirm the presence of amine N-H groups present in all repeat

units of dihydrazide monomers present in all TPDH resins. At 7.14-7.20 ppm and 5.87- 6.63 ppm

doublet peaks are present and are low field due to low electron densities around these amine

hydrogens and so they appear low field. In all resins at 7.50-7.75 ppm broad multiplet peak is seen

which confirm the presence of aromatic nuclei present in resins. In TPDH-6, TPDH-9, TPDH-11,

TPDH-12, TPDH-13 and TPDH-24, OH peaks is shifted down field due to low electron density

around oxygen atom due to involvement of Hydrogens in hydrogen bonding and up field shifts are

seen in resin TPDH-09 and TPDH-12 due to high electron density around oxygen atom due to less

hydrogen bonding. All these resins are materials of a series where difference arises in degree of

polymerization, which depends upon the ratio between monomers. FTIR and 1H NMR spectra of

optimized TPDH resin # 05 are given in figures 4.60 and 4.61 in annexes.

4.2.6 Chemical characterization of MGO resin series

Stabilized melamine glyoxylated based amino resins synthesized at different mole ratios


given

MGO # 02; FTIR (cm-1): 3720 (O-H), 3201 (N-H), 2812 (C-H), 1753(C=O), 1660 (C=C),

1577(C=C str), 1435(CH2 ben), 1188(S=O), 1006(C-O), 1H NMR-D2O: 8.32 (4H, s, CHO), 5.42

(6H, carbinyl carbon), 4.65 (2H, NH-SO) 4.00 (8H, NH), 3.80 (12H, s, -OH).

MGO # 03; FTIR (cm-1): 3776 (O-H), 3217(N-H), 2812 (C-H), 1753(C=O), 1668 ( C=C),

1563 (C=C str), 1427(CH2 ben), 1199 (S=O), 1033 (C-O). 1H NMR-D2O: 8.32 (4H, s, CHO), 5.36

(6H, carbinyl carbon), 4.68 (2H, NH-SO) 3.80 (8H, NH), 3.53 (12H, s, -OH),

MGO # 04; FTIR (cm-1): 3736(O-H), 3232 (N-H), 2812 (C-H), 1753(C=O), 1668 (C=C),

1518 (C=C str), 1456 (CH2 ben), 1188 (S=O), 1031(C-O), 1H NMR-D2O: 8.31 (4H, s, CHO), 5.34


211

MGO # 05; FTIR(cm-1): 3776(O-H), 3217 (N-H), 2814 (C-H), 1745 ( C=O ), 1666 (C=C

), 1587

(C=C str), 1427 (CH2 ben), 1192 (S=O), 1033 (C-O), 1H NMR-D2O: 8.32 (4H, s, CHO),

5.35


MGO # 06; FTIR(cm-1): 3736(O-H), 3330(N-H), 2812 (C-H), 1753(C=O), 1649(C=C),

1556(C=Cstr),1446(CH2 ben),1186 (S=O),1033(C-O), 1H NMR-D2O: 8.32 (4H, s, CHO),

5.35 (6H, carbinyl carbon), 4.65 (2H, NH-SO) 3.81 (8H, NH), 3.42 (12H, s, -OH),

MGO # 08; FTIR(cm-1) 3736(O-H),3192 (N-H), 2812 (C-H), 1753(C=O ), 1649(C=C),

1560 (C=C str),1419 (CH2 ben),1184(S=O), 1074 (C-O). 1H NMR-D2O: 8.30 (4H, s, CHO), 5.32


MGO # 09; FTIR(cm-1) 3738(O-H),3215 (N-H),2812 (C-H), 1753(C=O ), 1649(C=C),

1575 (C=C str), 1419 (CH2 ben),1182(S=O), 1076 (C-O), 1H NMR-D2O: 8.33 (4H, s, CHO), 5.46


MGO # 10; FTIR (cm-1): 3776(O-H), 3190 (N-H), 2926 (C-H), 1722(C=O ),

1649(C=C),1587 (C=C str),1431 (CH2 ben),1190(S=O),1024 (C-O). 1H NMR-D2O: 8.32 (4H, s,

CHO), 5.42 (6H, carbinyl carbon), 4.62 (2H, NH-SO) 3.80 (8H, NH), 3.52 (12H, s, -OH),

MGO # 11; FTIR (cm-1): 3778(O-H), 3176(N-H) 2881 (C-H), 1722(C=O ),

1649(C=C),1589 (C=C str),1483 (CH2 ben),1168(S=O),1072 (C-O). 1H NMR-D2O: 8.31 (4H, s,


MGO # 12; FTIR (cm-1) 3734(O-H),3238 (N-H), 2924 (C-H), 1747( C=O ), 1647( C=C ), 1548

(C=C str),1444 (CH2 ben),1190 (S=O),1031 (C-O), 1H NMR-D2O: 8.32 (4H, s, CHO), 5.43 (6H,

carbinyl carbon), 4.86 (2H, NH-SO) 4.00 (8H, NH), 3.80 (12H, s, -OH),

212

MGO # 14; FTIR (cm-1): 3718(O-H), 3213 (N-H), 2924 (C-H), 1747( C=O ), 1647( C=C

), 1548 (C=C str), 1423 (CH2 ben), 1192(S=O), 950 (C-O). 1H NMR-D2O: 8.29 (4H, s, CHO),


MGO # 15; FTIR (cm-1): 3736 (O-H), 3188 (N-H), 2924 (C-H), 1747( C=O ), 1647( C=C



MGO # 16; FTIR(cm-1) 3736(O-H), 3188 (N-H), 2956 (C-H), 1737 (C=O ), 1666 (C=C ),

1554 (C=C str), 1423 (CH2 ben), 1190(S=O), 958 (C-O), 1H NMR-D2O: 8.30 (4H, s, CHO), 5.30


MGO # 17; FTIR(cm-1):3776(O-H), 3263 (N-H), 2956 (C-H), 1737 (C=O ), 1666 (C=C ),

1581

(C=C str), 1543 ( ) 1435 (CH2 ben), 1190(S=O), 1020 (C-O), 1H NMR-D2O: 8.32 (4H, s,


MGO #18; FTIR (cm-1) 3776(O-H), 3217 (N-H), 2956 (C-H), 1737 (C=O ), 1666 (C=C ),

1589

(C=C str), 1429 (CH2 ben), 1188(S=O), 1029 (C-O). 1H NMR-D2O: 8.31 (4H, s, CHO),


MGO #19; FTIR(cm-1): 3778(O-H), 3390( N-H ), 2956 (C-H), 1724 ( C=O ), 1666 (C=C ), 1595

(C=C str), 1440 (CH2 ben),1346( ),1242( ), 1155(S=O), 1070 (C-O). 1H NMR-D2O: 8.30 (4H, s,

CHO), 5.38 (6H, carbinyl carbon), 4.65 (2H, NH-SO) 3.78 (8H, NH), 3.51 (12H, s, -OH).

MGO # 22; FTIR (cm-1): 3776(O-H), 3228 (N-H), 2814 (C-H), 1745 ( C=O ), 1666 (C=C ), 1587

(C=C str), 1427 (CH2 ben), 1193(S=O), 1031 (C-O). 1H NMR-D2O: 8.31 (4H, s, CHO), 5.35 (6H,

carbinyl carbon), 4.69 (2H, NH-SO) 3.82 (8H, NH), 3.58 (12H, s, -OH),

213

MGO # 23; FTIR(cm-1): 3778(O-H), 3334(N-H), 2920 (C-H),1745 ( C=O ), 1666 (C=C ),

1544

(C=C str), 1427 (CH2 ben), 1197(S=O), 1031 (C-O). 1H NMR-D2O: 8.31 (4H, s, CHO),


MGO # 24; FTIR(cm-1): 3778(O-H), 3342( N-H), 2812 (C-H), 1753(C=O ), 1668 ( C=C), 1589

(C=C str),1529 (C=C ben),1481 (CH2 ben),1433 (CH2 ben),1192 (S=O), 1026(C-O), 1H

NMRD2O: 8.32 (4H, s, CHO), 5.31 (6H, carbinyl carbon), 4.62 (2H, NH-SO) 3.80 (8H, NH), 3.53

(12H, s, -OH),

MGO # 28; FTIR(cm-1): 3776(O-H), 3302( N-H ), 2926 (C-H), 1745 ( C=O ), 1666 (C=C


5.28 (6H, carbinyl carbon), 4.77 (2H, NH-SO) 3.79 (8H, NH), 3.52 (12H, s, -OH).

MGO # 29; FTIR(cm-1): 3776(O-H), 3259 (N-H), 2926 (C-H), 1743 (C=O ), 1546 (C=C

str), 1429 (CH2 ben), 1197(S=O), 1024 (C-O). 1H NMR-D2O: 8.31 (4H, s, CHO), 5.16 (6H,

carbinyl carbon), 4.93 (2H, NH-SO) 3.79 (8H, NH), 3.52 (12H, s, -OH).

MGO # 30; FTIR (cm-1): 3776(O-H), 3265(N-H), 2926 (C-H), 1743 (C=O), 1666 (C=C),

1587 (C=C str), 1535 (C=C), 1431 (CH2 ben), 1195(S=O), 1020 (C-O). 1H NMR-D2O: 8.32 (4H,

s, CHO), 5.38 (6H, carbinyl carbon), 4.94 (2H, NH-SO) 3.80 (8H, NH), 3.53 (12H, s, -OH).

The FTIR spectra of the synthesized MGO amino resins exhibited absorption bands owing




of MGO-2 to MGO-30 a broad band is observed in the range 3720-3778 cm-1. In all MGT resins

the broad band for O-H is present at its normal absorption frequency and N-H stretchings are

lowered from their normal frequencies representing that hydrogen bonding involved in

intermolecularly intangled chains of amino resins and are present in the range 3176-3342 cm-1. A

peak is observed in the range 1722-1753 cm-1 which is due to C=O functionality of MGO resins

214

and is very prominent peak in all resins. The absorption bands at 1537-1666 cm-1 depicted the

presence of C=C stretching vibrations of aromatic nuclei present in the resins. Peaks in the range

1427-1456 cm-1 are due to CH2 out of plane bending vibrations.

In all MGO resins there is a peak in the range at 2824-2956cm-1 due to CH2 stretching


11681188 cm-1 is due to S=O bond in all resins produced due to sulfonation of resins and this peak

is prominent in all MGO resins, due to formation of polymers with more sulfonated chain ends.

Due to the C-O functionality present in all MGO resins, there is a peak at 1006-1103 cm-1 which

shows that ether as well as primary alcoholic functionality is present.

The 1H-NMR spectrum of MGO-1- MGO-30 showed 12H broad singlet peaks at 3.42-3.80

ppm due to OH protons present in oligomeric unit of dihydrazide. At position 4.62-4.87 ppm peaks

are to methylene protons in the monomeric repeat units adjacent to ether linkage and 5.16-5.47

ppm broad singlet peaks are present which confirm the presence of amine N-H groups present in

all repeat units of melamine glutaric dihydrazide monomers present in all MGO resinsn and these

peaks are upfield due to high electron densities around these amine hydrogens and so they appear

upfield. In all MGO resins the peaks of amide protons are seen at the same positions which confirm

the integrity of resins of comparative molecular weights formed. All these resins are materials of

a series where difference arises in degree of polymerization, which depends upon the ratio between

monomers. In all MGO-1 to MGO-18, resins polymers of higher molecular weights are formed,

here peak intensity is 50-60 times higher than NH amide peaks, which is indication of

polymerization and intensity is different in different cases showing the difference in the molecular

weights of polymers. Methylene protons adjacent to oxygen become singlet in resins where amide

NH protons involved more in hydrogen bonding and methylene protons cannot sense the

hydrogens and multiplet peaks are seen for resins where less hydrogen bonding occurs, and less

cross linking occurs. FTIR and 1H NMR spectra of optimized MGO resin # 24 are given in figures

4.62 and 4.63 in annexes.

215

4.2.7 Chemical characterization of MGT resin series

Stabilized melamine glutaraldehyde based amino resins synthesized at different mole ratios


given

MGT # 04; FTIR (cm-1): 3487 (O-H), 3341 (N-H), 2941 (C-H str, CH2), 1670 (C=O

amide) 1568 (C=N, amine), 1407 (CH2 ben), 1213 (S=O), 1056 (C-O). 1HNMR- D2O: 1.3 ppm

(79H, br, m), 3.53 (12H, br, m -OH) 3.80 (8H, NH), 4.967 ppm (6H, CH), 4.996 (2H, NH), 5.205

ppm (2H, NH-SO), 6.7 ppm (NH amide), 9.3 ppm(1H, CHO)


amide) 1565 (C=N, imine), 1408 (CH2 ben), 1199 (S=O), 1056 (C-O). 1HNMR- D2O: 1.38 ppm

(115H, br, m), 3.57 (13H, br, m -OH), 3.75 ppm (8H, NH), 4.95 ppm (7H, CH), 4.98 (2H, NH),

5.21 ppm (4H, NH-SO), 6.4 ppm (NH amide), 9.2 ppm (1H, CHO)



(13H, br, m), 3.57 (2H, br, m -OH), 3.749 ppm (1H, NH), 4.93 ppm (7H, CH), 5.05 (1H, OH),






MGT # 12; FTIR (cm-1): 3359.84 (O-H) & (N-H), 2942 (C-H str, CH2), 1566.07 (C=O

amide), 1409.87 (CH2 ben), 1198.41 (S=O), 1049.51 (C-O). 1HNMR- D2O: 1.31 ppm (148H, br,

m), 3.59 (7H, br, m -OH), 3.69 ppm (5H, NH), 4.945 ppm (16H, CH), 5.00 (4H, OH), 5.21 ppm

(1H, NH-SO), 6.6 ppm (NH amide), 9.2 ppm (1H, CHO)

216



(76H, br, m), 3.57 (8H, br, m -OH), 3.72 ppm (5H, NH), 4.95 ppm (9H, CH), 5.14 (4H, OH), 5.25

ppm (1H, NH-SO), 6.6 ppm (NH amide), 9.19 ppm (1H, CHO)





MGT # 20; FTIR (cm-1): 3488 (O-H), 3359 (N-H), 2942 (C-H str, CH2), 2868 (CHO)

1659 (C=O amide) 1583 (C=N, imine), 1409 (CH2 ben), 1198 (S=O), 1052 (C-O). 1HNMRD2O:

1.68 ppm (90H, br, m), 3.56 (6H, br, m -OH), 3.76 ppm (6H, NH), 4.969 ppm (10H, CH), 5.05

(4H, OH), 5.25 ppm (2H, NH-SO), 6.61 ppm (NH amide), 9.53 ppm (1H, CHO)



1.67 ppm (92H, br, m), 3.46 (4H, br, m -OH), 3.56 ppm (9H, NH), 4.94 ppm (3H, CH), 5.13 (8H,

OH), 5.20 ppm (2H, NH-SO), 6.53 ppm (NH amide), 9.23 ppm (1H, CHO)



1.67 ppm (99H, br, m), 3.49 (4H, br, m -OH), 3.57 ppm (9H, NH), 4.969 ppm (3H, CH), 5.05 (8H,

OH), 5.25 ppm (2H, NH-SO), 6.59 ppm (NH amide), 9.20 ppm (1H, CHO)



1.57 ppm (131H, br, m), 3.46 (8H, br, m -OH), 3.65 ppm (8H, NH), 4.94 ppm (14H, CH), 5.17

(5H, OH), 5.43 ppm (2H, NH-SO), 5.87 ppm (NH amide), 9.19 ppm (1H, CHO)

217



1.70 ppm (126H, br, m), 3.59 (5H, br, m -OH), 3.87 ppm (6H, NH), 4.95 ppm (7H, CH),

5.16 (7H, OH), 5.25 ppm (2H, NH-SO), 6.3 ppm (NH amide), 9.5 ppm (1H, CHO)

The FTIR spectra of the synthesized MGT amino resins exhibited absorption bands owing




of MGT-4 to MGT-24 a broad band is observed in the range 3450-3492 cm-1. In resins MGT-4 to

MGT-24, O-H stretchings lowered from their normal frequencies representing that hydrogen

bonding involved in intermolecularly intangled chains of amino resins. N-H stretching absorption

bands are seen in range 3337-3362, revealing normal stretching frequency of secondary amines. A

peak is observed in the range 1658-1712 cm-1 which is due to C=O functionality of MGT resins

and is very prominent peak in all resins. The absorption bands at 1537-1583cm-1 depicted the

presence of C=C stretching vibrations formed due to tautomerism in the resins and due to

conjugation, which result in the deficiency of carbonyl bond strength and these peaks are shifted

to smaller wave numbers. Peaks in the range 1405-1438cm-1 are due to CH2 out of plane bending

vibrations. In all MGT resins there is a peak in the range at 29392946cm-1 due to CH2 stretching


1197-1268 cm-1 is due to S=O bond in all resins produced due to sulfonation of resins and this

peak is prominent in all resins MGT, due to formation of polymers of lower molecular weight and

more sulfonated chain ends are obtained. Due to the CO functionality present in all MGT resins,

there is a peak at 1028-1092 cm-1 which shows that ether as well as primary alcoholic functionality

is present.

The 1H-NMR spectrum of MGT -4- MGT -24 showed 90-126H singlet peaks 1.31-1.70

ppm due to CH2 methylene protons present in the repeat unit of melamine dihydrazide and 5-11H

broad multiplet peak at 3.48-3.59 ppm due to OH protons. At position 3.57-3.87 ppm peaks are to

218

methylene protons in the monomeric repeat units adjacent to ether linkage and 4.93-4.97 ppm

singlet peaks are present which confirm the presence of amine N-H groups present in all repeat

units of melamine dihydrazide monomers present in all MGT resins. At 5.05-5.41 ppm and

5.876.63 ppm double doublet peaks are present and are upfield due to high electron densities

around these amine hydrogens and so they appear upfield. In MGT -23 one group of doublet peaks

is shifted upfield due to high electron density around nitrogen atom and downfield shifts are seen

in resin MGT-12, MGT-17, MGT-18 and MGT-20 due to low electron density around nitrogen

atom. All these resins are materials of a series where difference arises in degree of polymerization,

which depends upon the ratio between monomers. In all MGT -2 to MGT-24, resins polymers of

higher molecular weights are formed, here peak intensity is 100-140 times higher than NH amide

peaks, which is indication of polymerization and intensity is different in different cases showing

the difference in the molecular weights of polymers. Methylene protons adjacent to oxygen

become singlet in resins where amide NH protons involved more in hydrogen bonding and

methylene protons cannot sense the hydrogens and multiplet peaks are seen for resins where less

hydrogen bonding occurs, and less cross linking occurs. FTIR and 1H NMR spectra of optimized

MGT resin # 12 are given in figures 4.64 and 4.65 in annexes.

4.3Molecular weight of resins Molecular weight was determined by intrinsic viscosity method for each series of resins

and given below

4.3.1 Molecular weight of SDH series:

The molecular weight of ten stabilized succinic hydrazide formaldehyde condensates was

measured and presented in Table 4.10. ∆/c2 for the sample SDH #02 was calculated at different

concentrations from relative viscosity, specific viscosity and given in Table 4.8. The intrinsic

viscosity of the sample SDH # 02 was determined by extrapolating graph between the

concentration and ∆/c2 as shown in figure 4.1. This plot gives the value of 1/2 [ŋ]2 at zero

concentration which was 25.260. Thus, intrinsic viscosity was calculated to be 7.107. From the

intrinsic viscosity, molecular weight of the resin was calculated by applying Mark Houwink equation

and calculated to be 1926.93 as given in Table 4.10 and figure 4.3.

219

Table 4.8: Dependence of the flow time, relative viscosity, specific viscosity, ∆ = ŋsp - lnŋr and

∆/c2 on the concentration of the sample SDH # 02.

Conc.g/ml

Flow

time

seconds

ŋr ŋsp

lnŋr

∆ =ŋsp lnŋr ∆/c2

0.008 127.5 1.0712 0.0712 0.069 0.002 37.870

0.007 126.3 1.0611 0.0611 0.059 0.002 36.688

0.006 125.1 1.0510 0.0510 0.050 0.001 35.055

0.005 124.6 1.0468 0.0468 0.046 0.001 42.633

0.004 122.5 1.0292 0.0292 0.029 0.000 26.206

Figure 4.1: Dependence of ∆/c2 on the concentration of the sample SDH # 02.

Similar procedure was adopted for all the stabilized resinous samples of SDH series

(SDH # 03, SDH # 04, SDH # 06, SDH # 07, SDH # 08, SDH # 11, SDH # 12, SDH # 15 and

SDH # 16) and their measured intrinsic viscosity values were 7.108, 6.673, 5.641, 7.474, 7.301,

7.020, 7.755,

7.194, 8.172 and 7.543 respectively.

220

Their corresponding values for ∆/c2 are given in Table 4.9 and figure 4.2.

Table 4.9: Dependence of the concentration of sample (SDH # 03, SDH # 04, SDH # 06,

SDH # 07, SDH # 08, SDH # 11, SDH # 12, SDH # 15 and SDH # 16) on ∆/c2

Conc.g/ml SDH # 03 SDH # 04 SDH # 06 SDH # 07 SDH # 08 SDH # 11 SDH # 12 SDH # 15 SDH # 16

0.008 28.850 12.785 68.323 41.440 31.995 68.323 41.440 90.584 66.032

0.007 30.084 9.559 64.047 38.690 30.989 70.649 35.706 86.246 72.006

0.006 31.732 10.358 65.782 37.359 19.198 81.984 37.359 78.608 64.255

0.005 26.439 10.744 69.984 39.674 28.877 71.908 44.151 92.527 52.125

0.004 25.466 15.611 37.665 31.682 30.066 37.665 27.719 49.094 49.094

Figure 4.2: Dependence of ∆/c2 on the concentration of the samples SDH # 02, SDH # 03,

SDH # 04, SDH # 06, SDH # 07, SDH # 08, SDH # 11, SDH # 12, SDH # 15 and SDH # 16.

The molecular weights of the samples SDH # 03, SDH # 04, SDH # 06, SDH # 07, SDH

# 08, SDH # 11, SDH # 12, SDH # 15 and SDH # 16 were calculated and given in Table 4.10

and figure 4.3.

Table 4.10: Dependence of Molecular weight of SDH samples on monomers ratios

Trials

Sodium metabisulfite/ Formaldehyde/ Viscosity Molecular

Weight (Mv) succinic dihydrazide succinic dihydrazide

(Centipoise) (S/SDH) (F/SDH)

SDH # 01 0.1 2 Gelling N.A

SDH # 02 0.2 2 35 1926.932

221

SDH # 03 0.3 2 30 1734.549

SDH # 04 0.4 2 28 1311.092


SDH # 06 0.2 3 38 2095.360

SDH # 07 0.3 3 35.8 2014.891

SDH # 08 0.4 3 32.6 1887.605



SDH # 11 0.3 4 41.5 2228.275

SDH # 12 0.4 4 35.6 1966.028



SDH # 15 0.3 5 45.6 2431.532

SDH # 16 0.4 5 40.5 2127.568

Figure 4.3: Molecular weight of SDH resin samples

The data given in Table 4.10 and in Figure 4.3 shows that molecular weight of the sample

SDH #15 is at higher value. Viscosity is directly related to the molecular weight of the resin which

was confirmed by comparative viscosity behavior in relation to molecular weight as shown in

Figure 4.4.

222

Figure 4.4: Molecular weight of SDH resin samples versus viscosity (cps).

In Figure 4.5, effects of F/SDH mole ratio on viscosity of resin solutions at 35% solid

contents was shown with various mole ratios of S/SDH (data in Table: 3). Viscosity of resin

solutions showed increasing trend by increasing F/SDH mole ratio for all reactions performed

under similar conditions. N-methylol functionalities of resin increased with increasing F/GDH

mole ratio and resulted in high rates of condensation with increasing trend of viscosity [16].

Whereas, viscosity decreased with increasing of S/SDH mole ratio with constant F/SDH ratio.

223

Figure 4.5: Viscosity variation with various S/SDH and F/SDH mole ratio

As the degree of sulfonation increased, concentration of anionic groups increased on the

polymer chains, thereby making the chains to slide over each other more easily. Free functional

hydroxyl groups decreased by increasing sulfonation of the N-methylol groups along with

lowering hydrogen bonding that were involved in polymer system, thus resulting in low molecular

weight resinous solutions with lower viscosity. It was believed that at higher pH values, potential

energy and double layer parameter (I/k) were reduced, thus producing an aggregation because of

double layer compression [17]. Particles in this case fall into deep energy minima and get into

close contact with each other. Consequently number of total particles was decreased due to

attraction, leading to decrease in viscosity. At lower pH values, potential energy and double layer

parameter (I/k) of interactions were increased and resulted in expansion of electric field of the

particles as a result, a gellation of resin occurs due to long range interaction between the particles.

4.3.2 Molecular weight of GDH Series:

The molecular weight of eleven stabilized glutaric dihydrazide formaldehyde condensates

were measured and presented in Table 4.13. ∆/c2 for the sample GDH #01 was calculated at

224

different concentrations from relative viscosity, specific viscosity and given in Table 4.11.The

intrinsic viscosity of the sample GDH # 01 was determined by extrapolating graph between the


concentration which was 17.953. Thus, intrinsic viscosity was calculated to be 5.992. From the

intrinsic viscosity, molecular weight of the resin was calculated by applying Mark Houwink equation

and calculated to be 1449.72 as given in Table 4.13 and figure 4.8.


∆/c2 on the concentration of the sample GDH # 01.

Conc.g/ml Flow time seconds ŋr ŋsp lnŋr ∆ = ŋsp - lnŋr ∆/c2

0.008 128.18 1.077 0.077 0.074 0.003 44.029

0.007 126.5 1.063 0.063 0.061 0.002 38.690

0.006 125.09 1.051 0.051 0.050 0.001 34.942

0.005 124 1.042 0.041 0.050 0.001 34.068

0.004 122.8 1.032 0.032 0.031 0.000 30.869

Figure 4.6: Dependence of ∆/c2 on the concentration of the sample GDH # 01.

225

Similar procedure was adopted for all the stabilized resinous samples of GDH series (GDH

# 02,

GDH # 03, GDH # 04, GDH # 05, GDH # 08, GDH # 09, GDH # 10, GDH # 13, GDH # 14, GDH

# 15)

and their measured intrinsic viscosity values were found 5.936, 5.919, 4.949, 4.297, 6.791,

6.131, 5.829, 6.903, 6.836 and 5.965 respectively. Their corresponding values for ∆/c2 are given in

Table

4.12 and figure 4.7.

Table 4.12: Dependence of the concentration of sample (GDH # 02, GDH # 03, GDH # 04,

GDH #

05, GDH # 08, GDH # 09, GDH # 10, GDH # 13, GDH # 14, GDH # 15) on ∆/c2

Conc.g/ml GDH # 02 GDH # 03 GDH # 04 GDH # 05 GDH # 08

0.008 40.533 28.851 12.785 6.184 68.323

0.007 33.781 26.595 10.614 7.157 58.987

0.006 30.660 29.606 9.742 8.564 62.745

0.005 30.136 30.136 10.744 9.264 58.965

0.004 29.589 19.269 13.382 6.539 39.467

Conc.g/ml GDH # 09 GDH # 10 GDH # 13 GDH # 14 GDH # 15

0.008 60.465 22.350 70.651 63.777 40.533

0.007 43.919 17.381 70.649 73.375 93.817

0.006 49.936 17.541 68.886 65.782 156.384

0.005 42.633 19.756 53.797 39.674 285.048

0.004 37.665 19.269 47.087 51.142 542.632

226

Figure 4.7: Dependence of ∆/c2 on the concentration of the samples GDH # 02, GDH # 03,

GDH #

04, GDH # 05, GDH # 08, GDH # 09, GDH # 10, GDH # 13, GDH # 14, GDH # 15.

The molecular weights of the samples GDH # 02, GDH # 03, GDH # 04, GDH # 05, GDH #

08, GDH # 09, GDH # 10, GDH # 13, GDH # 14, GDH # 15 were calculated and given in Table 4.13

and figure 4.8.

Table 4.13: Viscosity and molecular weight of resins of GDH Series

S.No.

Sodium

metabisulfite/Glutaric

dihydrazide

(S/GDH)

Formaldehyde/Glutaric

dihydrazide (F/GDH)

Viscosity

(Centipoise)

Molecular

weight

(Mv)

1 0.1 1 22 1449.724

2 0.2 1 20 1427.24

3 0.3 1 18.5 1420.399

4 0.4 1 16.4 1054.12

5 0.5 1 10.6 832.904

227

6 0.1 2 Gel N.A

7 0.2 2 Gel N.A

8 0.3 2 44.5 1785.828

9 0.4 2 25.68 1505.977

10 0.5 2 15.98 1384.433

11 0.1 3 Gel N.A

12 0.2 3 Gel N.A

13 0.3 3 43 1835.279

14 0.4 3 40 1805.78

15 0.5 3 21.72 1438.964

228

Figure 4.8: Molecular weight of GDH resin samples

The data given in Table 4.13 and in Figure 4.8 showed that molecular weight of the sample

GDH # 13 is at higher value. Viscosity is directly related to the molecular weight of the resin which

was confirmed by comparative viscosity behavior in relation to molecular weight as shown in

Figure 4.9.

Figure 4.9: Molecular weight of GDH resin samples versus viscosity (cps)

In Figure 4.10, effects of F/GDH mole ratio on viscosity of resin solutions at 32% solid

contents is shown with various mole ratios of S/GDH (data in Table: 3). Viscosity of resin

solutions showed increasing trend by increasing F/GDH mole ratio for all reactions performed



Whereas, viscosity decreased with increasing of S/GDH mole ratio with constant F/GDH ratio.

229

Figure 4.10: Viscosity variation with S/GDH and F/GDH mole ratio.





weight resinous solutions with lower viscosity

4.3.3 Molecular weight of ADH Series:

The molecular weight of fifteen samples of adipic dihydrazide formaldehyde condensates

were measured and presented in Table 4.16. ∆/c2 for the sample GDH #01 was calculated at

different concentrations from relative viscosity, specific viscosity and given in Table 4.14. The

intrinsic viscosity of the sample ADH # 01 was determined by extrapolating graph between the


concentration which was 43.670. Thus, intrinsic viscosity was calculated to be 9.346.

230

From the intrinsic viscosity, molecular weight of the resin was calculated by applying Marl

Houwink equation and calculated to be 3040.793 as given in Table 8 and figure 12.


∆/c2 on the concentration of the sample ADH # 01.

Conc.g/ml

Flow

time

seconds ŋr ŋsp lnŋr

∆ = ŋsp

lnŋr ∆/c

2

0.008 136.7 1.149 0.149 0.138 0.010 157.020

0.007 134.2 1.128 0.128 0.120 0.008 153.100

0.006 130.6 1.097 0.097 0.093 0.004 123.525

0.005 128.7 1.081 0.081 0.078 0.003 125.532

0.004 125.8 1.057 0.057 0.055 0.002 97.714

Figure 4.11: Dependence of ∆/c2 on the concentration of the sample GDH # 01.

Similar procedure was adopted for all the stabilized resinous samples of ADH series ( ADH

# 02,

231

ADH # 03, ADH # 04, ADH # 05, ADH # 06, ADH # 07, ADH # 08, ADH # 09, ADH # 10, ADH # 11,

ADH # 12, ADH # 13, ADH # 14, ADH # 15) and their measured intrinsic viscosity values were

found 8.303, 7.726, 7.375, 7.194, 33.507, 31.372, 28.275, 25.795, 11.872, 38.845, 33.927, 32.074, 9.692

and 9.054 respectively. Their corresponding values for ∆/c2 are given in Table 4.15 and

figure

4.12.

Table 4.15: Dependence of the concentration of sample (ADH # 02, ADH # 03, ADH # 04,

ADH #

05, ADH # 06, ADH # 07, ADH # 08, ADH # 09, ADH # 10, ADH # 11, ADH # 12, ADH # 13,

ADH #

14, ADH # 15) on ∆/c2

Conc.g/ml ADH # 02 ADH # 03 ADH # 04 ADH # 05 ADH # 06 ADH # 07 ADH # 08

0.008 46.116 34.454 32.805 28.850 227.467 185.248 169.109

0.007 49.463 36.687 35.705 27.447 271.405 218.589 202.874

0.006 48.599 42.179 35.055 24.604 249.708 235.553 219.064

0.005 50.479 39.674 38.233 31.420 300.076 281.347 263.177

0.004 35.904 27.718 26.206 25.465 433.856 351.864 282.605

Conc.g/ml ADH # 09 ADH # 10 ADH # 11 ADH # 12 ADH # 13 ADH # 14 ADH # 15

0.008 151.963 105.616 325.632 245.850 207.794 77.854 56.178

0.007 177.186 103.297 383.261 271.405 239.571 77.556 62.763

0.006 200.536 99.872 393.746 270.157 255.475 64.255 65.781

0.005 205.640 113.198 437.426 315.459 277.668 53.797 50.479

0.004 250.656 76.341 574.820 445.388 389.135 71.397 49.093

232

Figure 4.12: Dependence of ∆/c2 on the concentration of the samples ADH #01, ADH #

02, ADH

# 03, ADH # 04, ADH # 05, ADH # 06, ADH # 07, ADH # 08, ADH # 09, ADH # 10, ADH # 11,

ADH # 12, ADH # 13, ADH # 14, ADH # 15.

The molecular weights of the samples ADH # 02, ADH # 03, ADH # 04, ADH # 05, ADH #

06, ADH # 07, ADH # 08, ADH # 09, ADH # 10, ADH # 11, ADH # 12, ADH # 13, ADH # 14, ADH #

15 were calculated and given in Table 4.16 and figure 4.13.

Table 4.16: Viscosity and molecular weight of resins of ADH Series with different mole

ratios of monomers

233

Sr. # (S/ADH) (F/ADH) Viscosity(Centipoise)

Molecular

weight

(Mv)

1 0.1 1 27.48 3040.793

2 0.2 1 13.74 2496.568

3 0.3 1 16.38 2214.652

4 0.4 1 11.22 2049.416

5 0.5 1 10.2 1966.187

6 0.1 (not applied) 2 72.38 at 75oC, Gell at 70oC 25539.44


8 0.3 2 60.43 at 75oC, Gell at 40oC 19245.14

9 0.4 2 52.57 at 75oC, Gell at 30oC 16515.06

10 0.5 2 38.4 4530.994




14 0.4 3 29.28 3230.975

15 0.5 3 27.66 2884.348

234

Figure 4.13: Molecular weight of resins of ADH series


ADH # 11 is at higher value. Viscosity is directly related to the molecular weight of the resin,

which was confirmed by comparative viscosity behavior in relation to molecular weight as shown

in Figure 4.14.

235

Figure 4.14: Correlation of viscosity average molecular weight with viscosity (cps)

In Figure 4.15, effects of F/ADH mole ratio on viscosity of resin solutions at 32% solid

contents is shown with various mole ratios of S/ADH (data in Table: 8). Viscosity of resin

solutions showed increasing trend by increasing F/ADH mole ratio for all reactions performed



Whereas, Viscosity decreased with increasing of S/ADH mole ratio with constant F/ADH ratio.

Figure 4.15: Viscosity variation of ADH resins with varying S/ADH and F/ADH mole

ratio.






236

4.3.4 Molecular weight of ISPDH Series: The molecular weight of twelve samples of

Isophthalic dihydrazide formaldehyde condensates were measured and presented in Table 4.19.

∆/c2 for the sample ISPDH #04 was calculated at different concentrations from relative viscosity,

specific viscosity and given in Table 4.17. The intrinsic viscosity of the sample ISPDH # 04 was

determined by extrapolating graph between the concentration and ∆/c2 as shown in figure 4.16.

This plot gives the value of 1/2 [ŋ] 2 at zero concentration which was 42491.33. Thus,

intrinsic viscosity was calculated to be 70.588. From the intrinsic viscosity, molecular weight of

the resin was calculated by applying Mark Houwink equation and calculated to be 88415.57 as

given in Table 11 and figure 17.


∆/c2 on the concentration of the sample ISPDH # 04.

Conc.g/ml Flow time seconds ŋr ŋsp lnŋr ∆ = ŋsp - lnŋr ∆/c2

0.008 155.6 1.31 0.307 0.267 0.039 614.785

0.007 154.1 1.29 0.294 0.258 0.036 743.473

0.006 152.8 1.28 0.283 0.249 0.033 943.875

0.005 150.4 1.26 0.263 0.234 0.029 1185.852

0.004 148.2 1.25 0.245 0.219 0.025 1618.607

237

Figure 4.16: Dependence of ∆/c2 on the concentration of the sample ISPDH # 04.

Similar procedure was adopted for all the stabilized resinous samples of ISPDH series

(ISPDH #

05, ISPDH # 06, ISPDH # 07, ISPDH # 13, ISPDH # 14, ISPDH # 22, ISPDH # 23, ISPDH # 24,

ISPDH # 32, ISPDH # 33, ISPDH # 34) and their measured intrinsic viscosity values were found

65.442,

63.632, 47.699, 64.027, 50.898, 63.849, 49.472, 47.301, 65.562, 64.356 and 50.671. Their

corresponding values for ∆/c2 are given in Table 4.18 and figure 4.17.

Table 4.18: Dependence of the concentration of sample (ISPDH # 05, ISPDH # 06, ISPDH #

07,

ISPDH # 13, ISPDH # 14, ISPDH # 22, ISPDH # 23, ISPDH # 24, ISPDH # 32, ISPDH # 33,

ISPDH # 34) on ∆/c2

Conc.g/ml ISPDH # 05 ISPDH # 06 ISPDH # 07 ISPDH # 13 ISPDH # 14 ISPDH # 22

0.008 548.463 465.966 332.721 493.769 422.919 477.005

0.007 597.889 580.205 362.959 580.205 450.202 542.103

0.006 751.856 714.791 411.551 714.791 505.789 674.063

0.005 1009.585 945.063 541.863 945.063 640.055 901.0

0.004 1407.813 1302.528 785.503 1340.4 917.914 1340.4

Conc.g/ml ISPDH # 23 ISPDH # 24 ISPDH # 32 ISPDH # 33 ISPDH # 34

238

0.008 389.271 356.834 551.409 460.487 420.288

0.007 434.575 440.797 615.799 538.694 440.797

0.006 490.134 463.263 747.179 678.537 494.02

0.005 629.376 587.465 1016.13 951.432 634.705

0.004 846.661 778.003 1417.56 1321.40 909.870

Figure 4.17: Dependence of ∆/c2 on the concentration of the samples ISPDH # 04,

ISPDH # 05,

ISPDH # 06, ISPDH # 07, ISPDH # 13, ISPDH # 14, ISPDH # 22, ISPDH # 23, ISPDH # 24,

ISPDH #

32, ISPDH # 33, ISPDH # 34

The molecular weights of the samples ISPDH # 05, ISPDH # 06, ISPDH # 07, ISPDH # 13,

ISPDH # 14, ISPDH # 22, ISPDH # 23, ISPDH # 24, ISPDH # 32, ISPDH # 33, ISPDH # 34 were

calculated and given in Table 4.19 and figure 4.18.

Table 4.19: Viscosity and molecular weight of resins of ISPDH Series with different mole

ratios of monomers

239

Experiment

No. Formaldehyde/Isophthalic

dihdyrazide mole ratio (F/ISPDH)


Isopthalic

dihdyrazide mole

ratio (S/ISPDH)

Viscosity (Centipoise)

Molecular

weight (Mv)

ISPDH # 04 1.5 0.4 55.7 88415.57

ISPDH # 05 1.5 0.5 50.5 77936.98

ISPDH # 06 1.5 0.6 45.4 74376.17

ISPDH # 07 1.5 0.7 35.6 46007.31

ISPDH # 13 2 0.6 45.7 75147.42

ISPDH # 14 2 0.7 40.6 51263.22

ISPDH # 22 2.5 0.8 45.3 74799.24

ISPDH # 23 2.5 0.9 38.4 48893.08

ISPDH # 24 2.5 1 35.5 45368.66

ISPDH # 32 3 0.8 50.5 78174.84

ISPDH # 33 3 0.9 48.7 75792.62

ISPDH # 34 3 1 39.5 50883.65

240

Figure 4.18: Molecular weight of resins of ISPDH series


ISPDH # 04 is at higher value. Viscosity is directly related to the molecular weight of the resin,


in Figure 4.19.


In Figure 4.20, effects of F/ISPDH mole ratio on viscosity of resin solutions at 32% solid

contents is shown with various mole ratios of S/ISPDH (data in Table: 11). Viscosity of resin

solutions showed increasing trend by increasing F/ISPDH mole ratio for all reactions performed

under similar conditions. N-methylol functionalities of resin increased with increasing F/ISPDH


Whereas, viscosity decreased with increasing of S/ISPDH mole ratio with constant F/ISPDH

ratio.

241

Figure 4.20: Viscosity variation of ISPDH resins with varying S/ISPDH and F/ISPDH mole ratio.





weight resinous solutions with lower viscosity.

4.3.5Molecular weight of TPDH series

The molecular weight of twelve samples of Isophthalic dihydrazide formaldehyde

condensates were measured and presented in Table 4.22. ∆/c2 for the sample TPDH #04 was

calculated at different concentrations from relative viscosity, specific viscosity and given in Table

4.20. The intrinsic viscosity of the sample TPDH # 04 was determined by extrapolating graph

between the concentration and ∆/c2 as shown in figure 4.21. This plot gives the value of 1/2 [ŋ] 2

at zero concentration which was 2711.923. Thus, intrinsic viscosity was calculated to be 73.647.

From the intrinsic viscosity, molecular weight of the resin was calculated by applying Mark

houwink equation and calculated to be 94892.84 as given in Table 14 and figure 22.

242

Table 4.20: Dependence of the flow time, relative viscosity, specific viscosity, ∆ = ŋsp -

lnŋr and ∆/c2 on the concentration of the sample TPDH # 04.

Conc.g/ml Flow time

seconds ŋr ŋsp lnŋr ∆ = ŋsp

lnŋr ∆/c

2

0.008 160.3 1.346 0.346 0.297 0.049 766.827

0.007 157.9 1.326 0.326 0.282 0.043 897.906

0.006 155.2 1.303 0.303 0.265 0.038 1071.09

0.005 152.6 1.282 0.282 0.248 0.033 1344.35

0.004 150.1 1.261 0.261 0.232 0.029 1820.149

Figure 4.21: Dependence of ∆/c2 on the concentration of the sample TPDH # 04.

Similar procedure was adopted for all the stabilized resinous samples of TPDH series

(TPDH #

05, TPDH # 06, TPDH # 14, TPDH # 22, TPDH # 23, TPDH # 24, TPDH # 33 and TPDH # 34)

and their measured intrinsic viscosity values were found 71.489, 64.913, 68.038, 50.805, 48.028,

41.267,

64.827 and 44.896. Their corresponding values for ∆/c2 are given in Table 4.21 and figure

4.22.

243

Table 4.21: Dependence of the concentration of sample (TPDH # 05, TPDH # 06, TPDH #

14,

TPDH # 22, TPDH # 23, TPDH # 24, TPDH # 33 and TPDH # 34) on ∆/c2

Conc.g/ml TPDH # 05 TPDH # 06 TPDH # 14 TPDH # 22 TPDH # 23 TPDH # 24 TPDH # 33 TPDH # 34

0.008 614.784 477.005 563.257 384.201 307.053 215.568 479.782 275.7

0.007 735.683 576.695 641.251 431.479 357.248 249.176 573.195 294.484

0.006 872.814 683.024 761.248 525.662 390.227 316.432 687.524 362.588

0.005 1206.967 951.432 1055.842 613.509 531.954 384.755 945.063 464.907

0.004 1660.192 1369.115 1526.709 893.877 785.503 568.314 1369.115 683.478

Figure 4.22: Dependence of ∆/c2 on the concentration of the samples TPDH # 04, TPDH

# 05,

TPDH # 06, TPDH # 14, TPDH # 22, TPDH # 23, TPDH # 24, TPDH # 33 and TPDH # 34

The molecular weights of the samples TPDH # 05, TPDH # 06, TPDH # 14, TPDH # 22, TPDH

# 23, TPDH # 24, TPDH # 33 and TPDH # 34 were calculated and given in Table 4.22 and figure 4.23.

244

Table 4.22: Viscosity and molecular weight of resins of TPDH Series with different mole

ratios of monomers

Experiment

No.

Formaldehyde/Terephthalic

dihydrazide mole ratio

(F/TPDH)

Sodium

metabisulfite/

Terephthalic

dihydrazide mole

ratio (S/TPDH)

Viscosity

(Centipoise)

Molecular

weight

(Mv)

TPDH # 04 1.5 0.4 58.8 94892.838

TPDH # 05 1.5 0.5 56.4 90304.762

TPDH # 06 1.5 0.6 45.7 76888.250

TPDH # 14 2 0.7 52.9 83155.772

TPDH # 22 2.5 0.8 40.8 51107.949

TPDH # 23 2.5 0.9 36.7 46537.884

TPDH # 24 3 1 30.4 36139.88

TPDH # 33 3 0.9 45.5 76718.753

TPDH # 34 3 1 34.6 41589.872

Figure 4.23: Molecular weight of resins of TPDH series


TPDH # 04 is at higher value. Viscosity is directly related to the molecular weight of the resin,


in figure 4.24.

245


In Figure 4.25,effects of F/TPDH mole ratio on viscosity of resin solutions at 40% solid

contents is shown with various mole ratios of S/TPDH (data in Table: 14). Viscosity of resin

solutions showed increasing trend by increasing F/TPDH mole ratio for all reactions performed

under similar conditions. N-methylol functionalities of resin increased with increasing F/TPDH


Whereas, viscosity decreased with increasing of S/TPDH mole ratio with constant F/TPDH ratio.

246

Figure 4.25: Viscosity variation of TPDH resins with varying S/TPDH and F/TPDH mole

ratio.






4.3.6 Molecular weight of MGO series: The molecular weight of twenty six samples of

sulfonated glyoxylated melamine condensates were measured and presented in Table 4.25. ∆/c2

for the sample MGO Resin # 03 was calculated at different concentrations from relative viscosity,

specific viscosity and given in Table 4.23. The intrinsic viscosity of the sample MGO Resin # 03

was determined by extrapolating graph between the concentration and ∆/c2 as shown in figure 25.

This plot gives the value of 1/2 [ŋ] 2 at zero concentration which was 3992.893. Thus, intrinsic

247

viscosity was calculated to be 89.363. From the intrinsic viscosity, molecular weight of the resin

was calculated by applying mark houwink equation and calculated to be 130991.2 as given in

Table 4.25 and figure 4.28.


lnŋr and ∆/c2 on the concentration of the sample MGO Resin # 03.

Conc.g/ml Flow time (seconds) ŋr ŋsp lnŋr ∆ = ŋsp lnɳr

∆/c2

0.008 165.7 1.392 0.392 0.330 0.061 958.056

0.007 164.2 1.379 0.379 0.321 0.057 1179.722

0.006 162.9 1.368 0.368 0.313 0.054 1523.126

0.005 159.8 1.342 0.342 0.294 0.04 1920

0.004 156.4 1.314 0.314 0.273 0.040 2558.723

Figure 4.26: Dependence of ∆/c2 on the concentration of the sample MGO Resin # 03.

Similar procedure was adopted for all the stabilized resinous samples of MGO series ( MGO

248

Resin # 04, MGO Resin # 05, MGO Resin # 06, MGO Resin # 09, MGO Resin # 10, MGO Resin

# 11, MGO Resin # 12, MGO Resin # 13, MGO Resin # 14, MGO Resin # 15, MGO Resin # 16, MGO

Resin #

17, MGO Resin # 18, MGO Resin # 19, MGO Resin # 20, MGO Resin # 21, MGO Resin # 22,

MGO


# 28, MGO Resin # 29, MGO Resin # 30) and their measured intrinsic viscosity values were found

67.494, 43.764, 42.476, 98.462, 91.031, 44.792, 41.558, 158.074, 112.886, 103.621, 94.569,

54.917, 52.501, 102.757, 72.920, 67.617, 47.521, 57.054, 49.828, 46.879, 49.275, 42.795, 38.584, 37.093

and

34.471 respectively. Their corresponding values for ∆/c2 are given in Table 4.24 and figure

4.27.

Table 4.24: Dependence of the concentration of sample (MGO Resin # 04, MGO Resin # 05,

MGO


# 13,

MGO Resin # 14, MGO Resin # 15, MGO Resin # 16, MGO Resin # 17, MGO Resin # 18, MGO

Resin # 19, MGO Resin # 20, MGO Resin # 21, MGO Resin # 22, MGO Resin # 23, MGO Resin # 24,

MGO


# 30) on ∆/c2

Conc.g/ml MGO # 04 MGO # 05 MGO # 06 MGO # 09 MGO # 10 MGO # 11 MGO # 12 MGO # 13 MGO # 14

0.008 551.409 330.351 297.944 1153.925 1059.964 351.953 288.955 2306.704 6.983

0.007 693.459 392.111 340.357 1324.628 1309.838 410.076 334.807 2939.14 7.496

0.006 789.724 448.211 415.154 1703.211 1637.971 490.135 400.826 3847.215 8.583

0.005 1049.179 546.849 502.721 2275.386 2094.637 592.634 478.931 5246.308 9.594

0.004 1506.603 655.513 607.855 3121.595 2659.943 676.437 587.933 7864.011 11.997

Conc.g/ml MGO # 15 MGO # 16 MGO # 17 MGO # 18 MGO # 19 MGO # 20 MGO # 21 MGO # 22 MGO # 23

0.008 1259.195 1126.197 463.224 444.220 1218.285 608.625 554.3614 323.284 482.566

0.007 1501.973 1359.393 545.521 525.153 1399.559 727.929 689.6732 377.411 552.385

249

0.006 1884.381 1703.211 660.717 595.733 1816.436 918.226 794.5131 429.707 674.063

0.005 2368.007 2094.637 791.934 756.954 2567.282 1221.133 1042.535 522.128 876.234

0.004 3540.947 2946.593 1016.896 934.097 3314.631 1712.81 1516.642 785.503 1068.07

Conc.g/ml MGO # 24 MGO # 25 MGO # 26 MGO # 27 MGO # 28 MGO # 29 MGO # 30

0.008 335.1 304.765 335.1 300.210 219.503 187.083 170.870

0.007 392.111 351.578 386.201 348.758 244.353 198.483 187.697

0.006 451.954 426.048 451.954 407.962 300.639 238.354 205.754

0.005 572.082 527.031 561.927 493.143 367.885 323.284 288.772

0.004 846.662 740.993 831.179 628.079 505.132 462.947 405.642

250

Figure 4.27: Dependence of ∆/c2 on the concentration of the samples MGO Resin # 03,

MGO



251


MGO Resin # 23, MGO Resin # 24, MGO Resin # 25, MGO Resin # 26, MGO Resin # 27, MGO Resin #

28, MGO Resin # 29, MGO Resin # 30

The molecular weights of the samples MGO Resin # 04, MGO Resin # 05, MGO Resin # 06,

MGO




MGO Resin # 26, MGO Resin # 27, MGO Resin # 28, MGO Resin # 29 and MGO Resin # 30 were

calculated and given in Table 4.25 and figure 4.28.

Table 4.25: Viscosity and molecular weight of resins of MGO resins with different mole

ratios of monomers

Experiment No G/M S/M Viscosity Molecular Weight (Mv)

MGO Resin # 01 2 0.5 Gel N.A

MGO Resin # 02 2 1 Viscous N.A

MGO Resin # 03 2 1.5 60.5 130991.2

MGO Resin # 04 2 2 45.7 82051.99

MGO Resin # 05 2 2.5 19.8 39857.09

MGO Resin # 06 2 3 18 37921.78

MGO Resin # 07 3 0.5 Gel N.A

MGO Resin # 08 3 1 Viscous N.A

MGO Resin # 09 3 1.5 75 153966.8

MGO Resin # 10 3 2 65 135091

MGO Resin # 11 3 2.5 20.8 41429.69

MGO Resin # 12 3 3 17 36565.4

MGO Resin # 13 4 0.5 538 338906.2

MGO Resin # 14 4 1 300 193365.4

MGO Resin # 15 4 1.5 235 167644

MGO Resin # 16 4 2 120 143954

MGO Resin # 17 4 2.5 24.9 58185.66

MGO Resin # 18 4 3 22.5 53982.56

MGO Resin # 19 5 0.5 86 165321.3

252

MGO Resin # 20 5 1 51.6 93338.02

MGO Resin # 21 5 1.5 45.8 82299.83

MGO Resin # 22 5 2 19 45720.68

MGO Resin # 23 5 2.5 25.2 62008.87

MGO Resin # 24 5 3 20.6 49481.17

MGO Resin # 25 6 0.5 18.72 44696.9

MGO Resin # 26 6 1 19.7 48568.21

MGO Resin # 27 6 1.5 17.4 38397.11

MGO Resin # 28 6 2 15.72 32309.44

MGO Resin # 29 6 2.5 13.26 30255.11

MGO Resin # 30 6 3 12.56 26775.03

Figure 4.28: Molecular weight of resins of MGO series

The data given in Table 4.25 showed that molecular weight of the sample MGO Resin #

13 is at higher value. Viscosity is directly related to the molecular weight of the resin, which was

confirmed by comparative viscosity behavior in relation to molecular weight as shown in figure

4.29.

253


In Table 4.25, effects of G/M mole ratio on viscosity of resin solutions at 40% solid

contents is shown with various mole ratios of S/M . Viscosity of resin solutions showed lowering

trend by increasing G/M mole ratio for all reactions performed under similar conditions. As the

number of N-methylol functionalities of resin increased, aldehydic functionalities also increase

which impart more solubilizing ability in the resin resulting in more fluid product. Whereas,

viscosity of glyoxylated resins also decrease by increasing S/M mole ratio at standard G/M mole

ratio. As degree of sulfonation increased, concentration of anionic groups increased on the polymer

chains, thereby making the chains to slide over each other more easily. Free functional hydroxyl

groups decreased by increasing sulfonation of the N-methylol groups along with lowering

hydrogen bonding that were involved in polymer system, thus resulting in low molecular weight

resinous solutions with lower viscosity.

4.3.7 Molecular weight of MGT series:

The molecular weight of seventeen samples of sulfonated glutaraldehyde melamine

condensates were measured and presented in Table 4.28. ∆/c2 for the sample MGT Resin # 03 was

calculated at different concentrations from relative viscosity, specific viscosity and given in Table

4.26. The intrinsic viscosity of the sample MGT Resin # 03 was determined by extrapolating graph

between the concentration and ∆/c2 as shown in figure 4.30. This plot gives the value of 1/2 [ŋ] 2

at zero concentration which was 5925.585. Thus, intrinsic viscosity was calculated to be 108.863.

254

From the intrinsic viscosity, molecular weight of the resin was calculated by applying mark

houwink equation and calculated to be 182016.9 as given in Table 4.28 and figure 4.32.


lnŋr and ∆/c2 on the concentration of the sample MGT Resin # 03.

Conc.g/ml Flow time seconds ŋr Ŋsp lnŋr ∆ = ŋsp - lnŋr ∆/c2

0.008 176.7 1.485 0.485 0.395 0.089 1397.853

0.007 173.5 1.458 0.458 0.377 0.081 1650.044

0.006 170.5 1.433 0.433 0.359 0.073 2030.239

0.005 168.4 1.415 0.415 0.347 0.068 2713.508

0.004 165.9 1.394 0.394 0.332 0.062 3861.858

Figure 4.30: Dependence of ∆/c2 on the concentration of the sample MGT Resin # 03.

Similar procedure was adopted for all the stabilized resinous samples of MGT series ( MGT

Resin

# 04, MGT Resin # 05, MGT Resin # 06, MGT Resin # 09, MGT Resin # 10, MGT Resin # 11,

MGT Resin # 12, MGT Resin # 15, MGT Resin # 16, MGT Resin # 17, MGT Resin # 18, MGT Resin #

20, MGT Resin # 21, MGT Resin # 22, MGT Resin # 23 and MGT Resin # 24) and their measured

intrinsic viscosity values were found 100.438, 66.262, 52.0655, 257.409, 226.005, 102.388, 66.547,

255

212.444, 196.898, 106.404, 99.282, 175.466, 167.716, 136.963, 115.786 and 86.128 respectively.

Their corresponding values for ∆/c2 are given in Table 4.27 and figure 4.31.

Table 4.27: Dependence of the concentration of sample (MGT Resin # 04, MGT Resin # 05,

MGT

Resin # 06, MGT Resin # 09, MGT Resin # 10, MGT Resin # 11, MGT Resin # 12, MGT Resin #

15,

MGT Resin # 16, MGT Resin # 17, MGT Resin # 18, MGT Resin # 20, MGT Resin # 21, MGT

Resin #

22, MGT Resin # 23 and MGT Resin # 24) on ∆/c2

Conc.g/ml MGT Resin # 04 MGT Resin # 05 MGT Resin # 06 MGT Resin # 09

0.008 1230.503 533.836 330.351 6897.325

0.007 1486.430 641.252 416.142 8310.672

0.006 1850.285 761.249 494.028 10995.735

0.005 2396.081 1009.585 613.509 14350.329

0.004 3272.871 1446.98 901.858 21194.130


0.008 4654.74 1222.352 733.326 4156.126

0.007 5701.118 1512.369 868.553 5322.144

0.006 7545.441 1863.894 949.041 6870.087

0.005 10575.46 2471.589 1102.987 9456.418

0.004 16074.97 3370.644 1587.717 14222.93


0.008 3712.063 1288.142 1198.027 3209.286

0.007 4644.22 1617.861 1470.951 4004.683

0.006 6057.782 2016.164 1809.696 4924.264

0.005 8215.771 2693.827 2358.678 6784.005

0.004 12264.34 3598.464 3189.996 9852.317


256

0.008 2808.428 2537.277 2044.402 1126.197

0.007 3334.892 3012.838 2454.388 1359.393

0.006 4304.048 3634.493 2974.125 1491.824

0.005 6037.575 4543.845 3534.724 1784.795

0.004 8939.907 6257.038 4504.788 2609.13

Figure 4.31: Dependence of ∆/c2 on the concentration of the samples MGT Resin # 03,

MGT


11,


Resin # 20, MGT Resin # 21, MGT Resin # 22, MGT Resin # 23 and MGT Resin # 24

257

The molecular weights of the samples MGT Resin # 04, MGT Resin # 05, MGT Resin # 06,

MGT


16,


Resin #

23 and MGT Resin # 24 were calculated and given in Table 4.28 and figure 4.32.

Table 4.28: Viscosity and molecular weight of resins of MGT Series with different mole

ratios of monomers

Sample G/M S/M Viscosity Molecular weight

(Mv)

MGT GT Resin # 01 3 0.5 Gel N.A

MGT GT Resin # 02 3 1 Gel N.A

MGT GT Resin # 03 3 1.5 189 182016.9

MGT GT Resin # 04 3 2 98 159149.5

MGT GT Resin # 05 3 2.5 42 79571.25

MGT GT Resin # 06 3 3 33 53238.63



MGT GT Resin # 09 4 1.5 Viscous 763863.6

MGT GT Resin # 10 4 2 Viscous 614953.1

MGT GT Resin # 11 4 2.5 116 164333.4

MGT GT Resin # 12 4 3 58 80141.73



MGT GT Resin # 15 5 1.5 Viscous 554692

MGT GT Resin # 16 5 2 viscous 488706

MGT GT Resin # 17 5 2.5 125 175215

MGT GT Resin # 18 5 3 95 156109

258


MGT GT Resin # 20 6 1 1600 403303.4

MGT GT Resin # 21 6 1.5 1450 374055

MGT GT Resin # 22 6 2 800 266879.7

MGT GT Resin # 23 6 2.5 450 201713.4

MGT GT Resin # 24 6 3 150 123183.5

Figure 4.32: Molecular weight of resins of MGT series

The data given in Table 4.28 showed that molecular weight of the sample MGT Resin # 15

is at higher value. As viscosity is directly related to the molecular weight of the resin, which was

confirmed by correlation figure of molecular weight with viscosity as shown in Figure 4.33.

259


In Table 4.28,effects of G/M mole ratio on viscosity of resin solutions at 40% solid contents

is shown with various mole ratios of S/M. Viscosity of resin solutions showed lowering trend by

increasing G/M mole ratio for all reactions performed under similar conditions. As the number of

N-methylol functionalities of resin increased, aldehydic functionalities also increase which impart

more solubilizing ability in the resin resulting in more fluid product. Whereas, viscosity of

glyoxylated resins also decrease by increasing S/M mole ratio at standard G/M mole ratio. As

degree of sulfonation increased, concentration of anionic groups increased on the polymer chains,

thereby making the chains to slide over each other more easily. Free functional hydroxyl groups

decreased by increasing sulfonation of the N-methylol groups along with lowering hydrogen

bonding that were involved in polymer system, thus resulting in low molecular weight resinous

solutions with lower viscosity.

4.4 Evaluation of retanning performance

Stabilized hydrazide modified amino resins and formaldehyde free amino resins were applied on

leather to get their retanning performance by the method given in table 3

4.4.1 Retanning performance of succinic dihydrazide formaldehyde condensates

260

Synthetic resins of SDH Series were applied on the leather to evaluate their retanning performance

by method given in Table 3.9. For physical testing of control and experimental leathers, samples were

obtained as per standard IUP 2 method. Conditionings of samples were carried out at 65±2% relative

humidity and at 80±4oF for a period of 48 hours. Physical properties such as grain cracking, Tear strength,

tensile strength and % elongation at break were evaluated as per standard procedures. Tear and tensile

strength were carried out for all the crust leathers both along and across the backbone line. The average

values along with standard deviation are given in Table 4.29. Grain distention for the leathers were also

performed and average values along with standard deviation is given in table 4.29.

Table 4.29: Effect of synthesized SDH resins on mechanical properties of leather

Mechanical Testing of Leather

Tensile

strength

Tear

Strength

%

Elongation

Tensile

strength

Tear

Strength

%

Elongation

Sample

(N/cm2)

(N/cm) (N/cm2) (N/cm)

Parallel to Backbone Perpendicular to Backbone

Resin N.2 2158.3 49 71 2508.3 68.8 57

SDH # 01 3062.4 68.6 67 3185 78.4 52

SDH # 02 3164.5 73.5 69 3634.1 78.4 61

SDH # 03 4264.8 112.7 98 4390.2 107.8 90

SDH # 04 2654.2 78.4 71 3675 58.8 68

SDH # 05 3142.3 53.9 65 2597.9 53.9 68

SDH # 06 3184.9 88.2 68 3096.5 93.1 66

SDH # 07 2722.2 73.5 50 3529.2 63.7 54

SDH # 08 2580.7 58.8 58 3470.8 58.8 58

SDH # 09 2280.5 73.5 70 2542.7 58.8 44

SDH # 10 2245.7 73.7 59 2994.4 83.3 63

261

SDH # 11 2232.2 107 70 3452.2 78.4 59

SDH # 12 3204.1 93.1 78 3096.5 88.2 71

SDH # 13 1939.5 49.98 54 2603 49 46

SDH # 14 2613.3 53.9 78 2776.6 58.8 70

SDH # 15 3266.6 73.5 79 3538.8 98 60

SDH # 16 2654.1 63.7 53 3470.7 68.6 65

Physical assessment of leather was measured by strength of leather fibers. It gives an

indication of condition of fiber bundles. The optimum results obtained through physical

assessment of leather help to select most suitable conditions with optimum S/SDH molar ratio and

F/SDH ratio.

Physical characteristics of re-tanned leather are graphically explained in Figure 4.34.

262

Figure 4.34: Physical assessment of leather; (a)Effect of SDH resins on Tensile strength of leather

fibers parallel to backbone; (b) Effect of SDH resins on Tear strength of leather fibers parallel to backbone;

(c) Effect of SDH resins on % Elongation of leather parallel to backbone;(d) Effect of SDH resins on Tensile

strength of leather fibers perpendicular to backbone;(e) Effect of SDH resins on Tear strength of leather

fibers perpendicular to backbone;(f) Effect of SDH resins on % Elongation of leather perpendicular to

backbone.

263

Table 4.29 and Figure 4.34 showed that resin synthesized at F/SDH mole ratio equal to 2

and S/SDH mole ratio equal to 0.3 shows optimum tear and tensile strength with maximum percent

elongation at break as compared to Resin N.2. Resin synthesized under these conditions reacts

properly with active sites of leather fibers to form new stable composite material. As the mole ratio

and degree of sulfonation is increased, molecular size and solubilizing factor change which limit

the reactivity of the resin with collagen fiber.

4.4.2 Retanning performance of glutaric dihydrazide formaldehyde condensates

Synthetic resins of GDH Series were applied on the leather to evaluate their retanning performance

by method given in Table 3.9. For physical testing of control and experimental leathers, samples were







Table 4.30: Effect of synthesized GDH resins on mechanical properties of leather

Experimental Samples

Parallel to backbone

Perpendicular to backbone Distension at

Grain Cracking

Tensile Strength % Elongation Tear Strength Tensile Strength % Elongation Tear Strength (mm)

(N/cm2) (N/cm2) (N/cm2) (N/cm)

Resin UFT 1169.2±122.19 50±7.07 245±14.14 1067.2±167.16 50±5.65 311.8±19.24 9.75±0.35

GDH #01 1150.7±90.79 52±2.83 356.3±27.58 1410.5±35.50 43±9.90 534.5±75.94 9.43±1.08

GDH #02 1187.7±126.43 43±5.65 534.5±19.23 1893.1±46.10 33±2.24 579±118.79 8.6±0.56

GDH #03 1054.8±29.13 60±2.83 356.36±41.56 1190.9±49.35 54±2.83 445.45±78.84 8.58±0.95

GDH #04 1105.8±35.35 60±7.07 326.6±49.50 1293±35.35 50±8.49 530.8±63.64 8.8±1.41

GDH #05 1088.8±14.14 61±5.65 326.6±35.53 1701.3±49.50 44±9.90 530.8±70.71 9.4±0.70

GDH #08 1150.7±41.15 41±5.66 445.4±49.50 1224.9±142.52 39±8.48 575.5±218.65 8.25±1.69

GDH #09 1531.2±78.34 60±7.07 602.5±68.30 1987.1±53.74 70±14.14 530.8±67.31 8.73±1.01

GDH #10 1373.4±39.59 41±2.82 534.5±93.62 1701.2±140.00 35±9.90 579±44.54 8.79±2.06

264

GDH #13 1447.7±31.25 46±2.83 445.4±77.50 1262.1±82.59 28±5.65 490±42.42 7.65±1.20

GDH #14 1360.3±35.50 52±11.31 356.3±98.28 990.7±162.77 44±8.48 343±101.82 8.69±1.68

GDH #15 1258.9±65.76 54±4.24 668.2±53.17 1769.4±101.96 53±9.90 490±31.67 8.14±0.40

NOTE: GDH # 06, 07, 11 and 12 were not applied in leather retanning process due to gellation.

Physical assessment of leather was measured by strength of leather fibers. It gives an

indication of condition of fiber bundles. The optimum results obtained through physical

assessment of leather help to select most suitable conditions with optimum S/GDH molar ratio and

F/GDH ratio. Physical characteristics of re-tanned leather are graphically explained in Figure 4.35.

265

Figure 4.35: Physical assessment of leather; (a) Effect of GDH resins on tensile strength

of leather fibers parallel to backbone; (b) Effect of GDH resins on tensile strength of leather fibers

perpendicular to backbone; (c) Effect of GDH resins on tear strength of leather fibers parallel to

backbone; (d) Effect of GDH resins on tear strength of leather fibers perpendicular to backbone;

(e) Effect of GDH resins on % elongation of leather parallel to backbone; (f) Effect of GDH resins

on % elongation perpendicular to backbone; (g) Effect of GDH resins on grain cracking

It has been observed from Table 4.30 and Figures 4.35 that GDH # 09 resin synthesized at

S/GDH and F/GDH mole ratios of 0.4 and 2.0, respectively, showed most favorable values for

grain cracking tear strength and tensile strength with maximum elongation values. The resin

synthesized under these optimum conditions possessed good reactivity with collagen fibers of

leather to form stabilized composite material. Molecular size and solubilizing factor of the resins

changed with varying degree of sulfonation and F/GDH molar ratio, which ultimately limit the

reactivity of resin with collagen fiber of leather.

4.4.3 Retanning performance of adipic dihydrazide formaldehyde condensates

266

Synthetic resins of ADH Series were applied on the leather to evaluate their retanning performance

by method given in table 3.9. For physical testing of control and experimental leathers, samples were







Table 4.31: Effect of synthesized ADH resins on mechanical properties of leather

Experiments


Perpendicular to backbone Parallel to

backbone Perpendicular to

backbone

Distension at Grain Cracking

Free

formaldehyde

contents

Tensile Strength

% Elongation

Tensile Strength

% Elongation Tear Strength

(N/cm) Tear Strength

(N/cm) (mm) (ppm)

(N/cm2) (N/cm2)

Commercial Resin 1677.6 ± 4.38 54 ± 2.83 1035.5 ± 34.36 35 ± 2.82 144.54 ± 3.90 185.35 ± 20.64 8.54 ± 1.34 154 ± 4.67

ADH # 01 2107.78 ± 142.43 63 ± 2.82 2095.8 ± 42.28 57 ± 2.83 257.9 ± 17.25 335.55 ± 6.85 9.85 ± 1.27 <10

ADH # 02 2246.78 ± 142.94 66 ± 2.83 2797 ± 138.59 58 ± 1.42 381.11 ± 15.00 200.9 ± 7.21 10.99 ± 1.61 <10

ADH # 03 2021.9 ± 9.61 60 ± 4.24 1781.7 ± 26.58 50 ± 4.24 240 ± 49.50 196 ± 29.70 9.35 ± 0.57 <10

ADH # 04 1942.2 ± 58.97 62 ± 2.83 2071.5 ± 121.34 56 ± 1.42 335.55 ± 49.71 190 ± 7.07 9.88 ± 0.14 <10

ADH # 05 1272.7 ± 39.74 41 ± 5.65 1263.6 ± 52.73 35 ± 7.07 267.2 ± 47.58 298.2 ± 38.60 7.47 ± 1.38 <10

ADH # 08 775.8 ± 21.21 42 ± 5.65 1037.8 ± 29.56 39 ± 4.24 149 ± 8.49 189.02 ± 16.09 6.56 ± 1.32 65 ± 2.3

ADH # 09 667.4 ± 32.66 33 ± 7.07 726.9 ± 12.44 30 ± 5.65 189 ± 8.48 155.6 ± 27.43 7.2 ± 1.70 58 ± 3

ADH # 10 779.6 ± 29.13 36 ± 4.24 834.4 ± 82.87 27 ± 1.42 222.7 ± 75.23 298.2 ± 3.11 6.28 ± 1.37 560 ± 2

ADH # 14 790.7 ± 27.86 40 ± 2.82 816.6 ± 37.05 34 ± 4.24 178.2 ± 10.18 156.3 ± 12.58 6.33 ± 1.15 100 ± 1.56

ADH # 15 655.6 ± 28.70 31 ± 2.82 214.9 ± 29.27 29 ± 2.82 108 ± 9.89 147 ± 18.38 6.66 ± 0.83 89 ± 3.75

NOTE: ADH # 06, 07, 11, 12 and 13 were not applied in leather retanning process due to

gelling form at room temperature.

Physical assessment of re-tanned leather was determined by the strength of leather fibers.

The optimum results obtained through physical assessment of leather help to select most suitable

conditions with optimum S/ADH molar ratio and F/ADH ratio. Physical characteristics of retanned

leather are graphically explained in Figure 4.36.

267

Figure 4.36: Physical characteristics of re-tanned leather, (a) Effect of polymer on Tensile

268

Strength perpendicular to backbone; (b) Effect of polymer on % Elongation perpendicular

to backbone; (c) Effect of polymer on Tensile Strength parallel to backbone; (d) Effect of polymer

on % Elongation parallel to backbone; (e) Effect of polymer on Tear Strength parallel to backbone;

(f) Effect of ADH polymers on Tear Strength perpendicular to backbone; (g) Effect of ADH

polymers on Distension at grain cracking of the leather.

It has been observed in Table 4.31, and Figure 4.36 that ADH resin synthesized at S/ADH

and F/ADH mole ratios of 0.2 and 1, respectively had maximum values for grain distension of

leather surface, tear strength and tensile strength of leather fibers with maximum elongation values.

The resin prepared in these optimum conditions has good reactivity with fiber of leather to form

stable composite material. Solubilizing factors and molecular size of resins changes by varying

degrees of sulfonation and F/ADH mole ratios, which results in limiting substantivity of the resin

with collagen of leather fibers.

4.4.4 Retanning performance of isophthalic dihydrazide formaldehyde condensates

Synthetic resins of ISPDH Series were applied on the leather to evaluate their retanning

performance by method given in table 3.9. For physical testing of control and experimental

leathers, samples were obtained as per standard IUP 2 method. Conditionings of samples were

carried out at 65±2% relative humidity and at 80±4oF for a period of 48 hours. Physical properties

such as grain cracking, Tear strength, tensile strength and % elongation at break were evaluated as

per standard procedures. Tear and tensile strength were carried out for all the crust leathers both

along and across the backbone line. The average values along with standard deviation are given in

Table 4.32. Grain distention for the leathers were also performed and

average values along with standard deviation is given in table 4.32

269

Table 4.32: Effect of synthesized ISPDH resins on mechanical properties of leather

Experiments

Parallel to

backbone

Perpendicula

r to backbone

Distension at Grain Cracking

Distension at Burst

Parallel to backbone Perpendicular to backbone Free formaldehyde

contents

Tear

Strength

(N/cm2)

Tear

Strength

(N/cm)

(mm) (mm) Tensile

Strength

(N/cm2)

%

Elongation

Tensile

Strength

(N/cm2)

%

Elongation

(ppm)

Commercial product 476±5.8 550±7.9 6.85±0.06 9.82±0.25 1275±64.34 49.68±1.35 1583±58.92 35.68±1.89 185±8.75

ISPDH # 04 267.3±6.8 361±7.5 6.945±0.6293 9.09±0.55 1189±107.621 51±1.41 1408.7±28.99 35.75±0.35 <10

ISPDH # 05 441±9.7 620.6±6.8 6.98±0.45 8.82±0.947 1145±60.31 36.5±0.707 1653.75±86.62 33±1.41 <10

ISPDH # 06 490±8.4 623.6±5.8 7.66±0.08 10.26±0.0212 1362.05±105 49±1.41 1633.3±57.69 35±4.24 <10

ISPDH # 07 400.9±6.9 588±6.9 6.38±0.68 8.685±0.304 1262.3±36.76 41±4.242 1367.9±86.69 26±2.82 <10

ISPDH # 13 544.4±4.4 707.7±8.4 8.01±0.05 9.61±0.311 1878.3±519.72 46±2.82 1615.5±275.84 42±2.82 20±3

ISPDH # 14 272.2±6.5 551.2±6.7 8.135±0.47 9.41±0.44 1565.2±32.10 39.5±0.707 1429.1±144.39 23±1.41 15±2.3

ISPDH # 22 108.8±8.9 147±7.9 8.65±0.212 10.68±0.53 837.05±86.62 47±1.41 1254±132.2 31±4.24 30±3

ISPDH # 23 551.2±10.6 673.7±6.3 8.08±0.26 9.77±0.42 1369.6±12.02 39±1.41 1166.25±18.87 29±1.41 27±2

ISPDH # 24 762.2±8.5 866.6±7.9 9.53±0.51 10.39±0.87 2381.9±96.30 43±1.41 2220±21.21 35±1.41 26±1.56

ISPDH # 32 206.3±9.3 272.2±9.4 7.035±0.516 8.585±0.44 1156.9±96.30 36.5±0.70 798.5±89.80 28.2±0.28 35±3.75

ISPDH # 33 653.3±7.9 816.6±8.2 9.215±0.12 11.59±0.431 1705.85±25.66 38±2.82 1375.25±148.42 34±2.82 28±2.35

270

ISPDH # 34 272.2±9.4 518.8±7.8 7.99±0.19 9.55±0.212 1142.45±287.58 41±1.41 952.7±192.47 36.2±0.28 17±1.56

Physical assessment of re-tanned leather was determined by the strength of leather fibers. The optimum results obtained through

physical assessment of leather help to select most suitable conditions with optimum S/ISPDH molar ratio and F/ISPDH mole ratio.

Physical characteristics of re-tanned leather are graphically explained in Figure 4.37.

271

Figure 4.37: Physical characteristics of re-tanned leather, (a) Effect of ISPDH resins on Tear strength of the leather fibers parallel

to backbone; (b) Effect of ISPDH resins on Tear strength of the leather fibers perpendicular to backbone; (c) Effect of ISPDH resins on

Distension at ball burst; (d) Effect of ISPDH resins on Tensile strength of the leather fibers parallel to backbone; (e) Effect of ISPDH

272

resins on % Elongation of the leather fibers parallel to backbone; (f) Effect of ISPDH resins on Tensile strength of the leather fibers

perpendicular to backbone; (g) Effect of ISPDH resins on % Elongation of the leather fibers perpendicular to backbone.

It is evident from the results that all the resin synthesized at different reactant molar ratios is showing comparable strengths with

commercial melamine formaldehyde resin. Isophthalic dihydrazide formaldehyde condensates synthesized at F/ISPDH molar ratio of

1.5 : 1 are showing free formaldehyde contents in retanned leather within in permissible limits (<10ppm) as compared to other resins

synthesized at higher ratio of formaldehyde contents. At constant molar ratio of F/ISPDH of 1.5:1, as the degree of sulfonation is

increased, resin has more stability in liquid form and has better retanning performance with optimum results at S/ISPDH mole ratio of

0.6: 1.

4.4.5Retanning performance of terephthalic dihydrazide formaldehyde condensates

Synthetic resins of TPDH Series were applied on the leather to evaluate their retanning performance by method given in table

3.9. For physical testing of control and experimental leathers, samples were obtained as per standard IUP 2 method. Conditionings of

samples were carried out at 65±2% relative humidity and at 80±4oF for a period of 48 hours. Physical properties such as grain

cracking, Tear strength, tensile strength and % elongation at break were evaluated as per standard procedures. Tear and tensi le strength

were carried out for all the crust leathers both along and across the backbone line. The average values along with standard deviation

are given in Table 4.33. Grain distention for the leathers were also performed and average values along with standard deviation is

given in table.

4.33.

273

Table 4.33: Effect of synthesized TPDH resins on mechanical properties of leather

Experiment

No. Parallel to backbone

Perpendicular to backbone

Distension

at Grain

Cracking

Tensile Strength % Elongation Tear Strength Tensile Strength % Elongation Tear Strength (mm)

(N/cm2) (N/cm) (N/cm2) (N/cm) (N/cm)

TPDH # 04 816.66±115.49 52±2.82 663.86±69.09 857.5±173.24 33±4.24 489±1.41 8.46±0.76

TPDH # 05 1657.35±370.87 61±1.41 893±130.81 1204.55±144.32 46±5.65 624.8±1.69 10.02±0.6

7

TPDH # 06 853.75±52.53 47±4.24 710±35.35 837.05±86.62 45±7.07 394±2.82 9.48±0.49

TPDH # 14 1388.3±230.94 47±4.24 572.25±53.38 845.7±69.72 36±8.48 443±2.82 9.00±0.16

TPDH # 22 1025.65±6.85 57±4.24 483±59.39 890.85±52.53 45±7.07 390.5±2.12 9.73±0.66

TPDH # 23 816.6±144.39 59±1.41 747.37±69.11 1065±120.20 43±12.72 613.75±1.76 7.69±0.30

TPDH # 24 866.55±186.03 43.5±0.70 473±53.03 902.85±6.43 39±1.41 295±1.41 9.1±0.11

TPDH # 33 775.8±57.69 35±4.24 462.63±50.86 694.1±173.24 29.5±0.70 216.38±1.95 8.34±0.36

TPDH # 34 1013.35±68.23 43±1.41 525.75±50.55 865.75±35.56 36±5.65 442.5±2.12 8.46±0.05

Counter

product 849.125±98.46 53.5±6.36 600.75±27.78 929.95±49.70 39±1.41 297±4.24 8.39±0.97

274


The optimum results obtained through physical assessment of leather help to select most suitable

conditions with optimum S/TPDH molar ratio and F/TPDH ratio. Physical characteristics of

retanned leather are graphically explained in Figure 4.38.

275

Figure 4.38: Physical characteristics of re-tanned leather; (a) Effect of TPDH resins on Tensile

strength of leather fibers parallel to backbone; (b) Effect of TPDH resins on % Elongation of leather

fibers parallel to backbone; (c) Effect of TPDH resins on Tear Strength of leather fibers parallel to

backbone; (d) Effect of TPDH resins on Tensile strength of leather fibers perpendicular to backbone;

(e) Effect of TPDH resins on % Elongation of leather fibers perpendicular to backbone; (f)

Effect of TPDH resins on Tear Strength of leather fibers perpendicular to backbone

It is evident from the results that all the resin synthesized at different reactant molar ratios is

showing comparable strengths with commercial melamine formaldehyde resin. Isophthalic dihydrazide

formaldehyde condensates synthesized at F/TPDH molar ratio of 1.5 : 1 are showing free formaldehyde

contents in retanned leather within in permissible limits (<10ppm) as compared to other resins

synthesized at higher ratio of formaldehyde contents. At constant molar ratio of F/TPDH of 1.5:1, as

276

the degree of sulfonation is increased, resin has more stability in liquid form and has better retanning

performance with optimum results at S/TPDH mole ratio of 0.5: 1.

4.4.6Retanning performance of melamine glyoxylated condensates

Synthetic resins of MGO Series were applied on the leather to evaluate their retanning

performance by method given in table 3.9. For physical testing of control and experimental

leathers, samples were obtained as per standard IUP 2 method. Conditionings of samples were

carried out at 65±2% relative humidity and at 80±4oF for a period of 48 hours. Physical properties

such as grain cracking, Tear strength, tensile strength and % elongation at break were evaluated as

per standard procedures. Tear and tensile strength were carried out for all the crust leathers both

along and across the backbone line. The average values along with standard deviation are given in

Table 4.34. Grain distention for the leathers were also performed and average values along with

standard deviation is given in table. 4.34

Table 4.34: Effect of synthesized MGO resins on mechanical properties of leather

Sr # Load at Burst kg Distension at Burst (mm)

Tear Strength (N/cm2)

Tensile strength (N/cm)

% Elongation

Tear Strength (N/cm2)

Tensile strength (N/cm)

% Elongation

Parallel to backbone Perpendicular to backbone

MGO Resin # 03 37±2.83 8.88±0.59 960±28.28 1525.55±56.17 72.5±3.53 1084±8.48 3574.75±15.76 47.5±3.53

MGO Resin # 04 76.5±2.12 11.18±0.72 58.8±1.69 2660.8±101.54 88±2.82 128.4±2.26 3516.5±66.60 48.5±2.12

MGO Resin # 05 73.5±0.71 10.35±0.44 1151.65±11.80 2624.2±121.05 74.5±2.12 1405.5±21.92 3419.8±49.92 48±2.82

MGO Resin # 09 62±8.48 9.48±0.05 740±7.07 1768.05±258.58 77.5±3.53 820.8±5.93 1377.5±126.00 57.5±3.53

MGO Resin # 10 72±4.24 9.44±0.77 878.5±4.94 2419.3±796.62 53±1.41 1091.5±19.09 2574±171.11 39.25±1.06

MGO Resin # 11 72±1.42 10.02±0.48 750.8±35.35 2343.6±269.54 71.5±3.53 1076.05±20.43 3526.45±157.47 28.5±0.70

MGO Resin # 12 82.5±3.53 9.89±0.60 1174.25±22.83 2759.85±86.76 79±1.42 1164.35±29.76 3351.5±139.30 35±1.41

MGO Resin # 14 68.75±3.18 8.75±0.08 899.4±1.55 1986.72±77.60 55.25±1.06 1076±20.36 2769.4±125.72 37.35±1.90

MGO Resin # 15 68.5±2.12 9.21±0.37 526.9±19.23 2156.7±530.18 45.25±2.47 731.45±26.51 2726.55±123.67 41.5±2.12

MGO Resin # 16 77±1.41 10.69±0.02 788.66±18.15 2479.15±288.71 64±2.82 905.415±10.01 4100.95±135.69 38±2.82

MGO Resin # 17 72.5±2.13 10.98±0.42 962.25±32.73 3177±111.72 47±1.41 1002.5±31.81 4474.6±168.43 38.5±2.12

MGO Resin # 18 85±2.81 11.1±0.21 702.3±17.96 3253.8±143.25 59.5±2.12 865±35.35 3674.95±44.47 52±2.83

MGO Resin # 20 63.75±1.77 9.59±0.41 704.55±14.77 1769.4±64.20 42±2.83 782.9±10.04 2943.35±72.19 47.25±1.06

MGO Resin # 21 60±1.42 11.53±0.29 412.95±17.04 2501±24.04 55±1.40 519.15±8.27 3480.2±82.87 31±1.42

MGO Resin # 22 64.5±0.70 9.92±0.21 725.95±13.93 3004.6±81.88 50.75±1.77 781.35±27.08 3754.85±148.28 47±1.40

MGO Resin # 23 73.25±1.06 9.56±0.44 629.7±8.62 3709±48.08 51.5±3.53 731.36±26.36 3821.5±177.76 34.5±2.10

MGO Resin # 24 85.5±0.70 10.24±0.09 1495±35.35 4862.8±262.47 58.75±1.06 1452.1±37.75 4487.45±150.26 38.5±2.13

MGO Resin # 25 83±4.24 12.21±0.41 1250±35.35 1990.85±129.61 42.25±3.18 1305.62±27.40 1560.4±103.09 54±2.83

MGO Resin # 26 62±1.42 9.17±0.22 277.12±18.78 2064.55±111.36 69±1.40 500±14.14 2480.65±148.42 50.5±0.70

MGO Resin # 27 63.5±2.13 10.44±0.05 669.36±22.67 1958.05±39.24 33.5±2.12 828.58±16.85 3002±164.19 34.25±0.35

MGO Resin # 28 66.5±3.53 11.11±0.42 365.98±13.60 2055.76±145.04 60.5±2.12 408.2±10.32 3081.04±52.52 37.5±0.71

MGO Resin # 29 73.5±2.12 10.87±0.02 334.25±20.15 2482.6±138.59 81.5±3.53 497.5±10.60 3123.85±145.16 34.25±2.13

MGO Resin # 30 71.75±2.47 12.71±1.68 193.25±10.25 2974.55±46.59 38±2.83 367.9±11.17 3688.5±139.72 42±2.82

Conventional melamine

resin 73.75±1.77 9.55±0.42 908±24.74 2871.45±107.55 75±4.23 1000.5±35.35 3027.85±90.15 66.25±0.36

163

279


The optimum performance obtained by physical assessment of leather help to optimize the mole

ratio of S/M and G/M for the synthesis of glyoxylated melamine based resin. Physical

characteristics of re-tanned leather are graphically explained in Figure 4.39.

280

164

Figure 4.39: Physical characteristics of re-tanned leather; (a) Effect of MGO Resins on Tensile

strength of leather fibers perpendicular to backbone; (b) Effect of MGO Resins on % Elongation of

leather fibers perpendicular to backbone; (c) Effect of MGO Resins on Tensile strength of leather fibers

parallel to backbone; (d) Effect of MGO Resins on % Elongation of leather fibers parallel to backbone;

(e) Effect of MGO Resins on Tear Strength of leather fibers perpendicular to backbone; (f) Effect of

MGO Resins on Tear Strength of leather fibers parallel to backbone; (g) Effect of MGO

Resins on Distension at burst of the leather fibers

It has been noticed from data given in Table 4.34 and figure 4.39 that glyoxylated melamine

based resin (MGO Resin # 24) prepared at mole ratios of 3 and 5 for S/M and G/M respectively showed

maximum values for grain distension of leather surface, tear and tensile strength of leather fibers.

281

Under these optimum conditions, resin has good cross linking ability with collagen (Leather fiber

protein) to form stabilized composite material.

4.4.7Retanning performance of melamine glutaraldehyde condensates

Synthetic resins of MGT Series were applied on the leather to evaluate their retanning performance by method given in table 3.9.

For physical testing of control and experimental leathers, samples were obtained as per standard IUP 2 method. Conditionings of samples

were carried out at 65±2% relative humidity and at 80±4oF for a period of 48 hours. Physical properties such as grain cracking, Tear

strength, tensile strength and % elongation at break were evaluated as per standard procedures. Tear and tensile strength were carried

out for all the crust leathers both along and across the backbone line. The average values along with standard deviation are given in

Table 4.35. Grain distention for the leathers were also performed and average values along with standard deviation is given in table.

4.35

Table 4.35: Effect of synthesized MGT resins on mechanical properties of leather

Experimental Samples


Perpendicular to backbone Distension

at Grain

Cracking

Tensile Strength % Elongation

Tear Strength Tensile Strength % Elongation

Tear Strength (mm)

(N/cm2) (N/cm2) (N/cm) (N/cm)

Commercial melamine resin 1420±28.28 50±2.82 496±26.69 1514±55.15 41±2.82 630±42.42 7.35±1.41

MGT GT Resin # 03 799.3±71.7 64±14.14 487.5±3.53 1385.75±227.3 45±1.41 478±67.88 7.32±0.67

MGT GT Resin # 04 1807±60.81 36±5.65 480±14.14 1682.85±163.97 45±1.41 492.5±3.53 7.27±0.45

MGT GT Resin # 06 1277.5±215.66 59±1.41 458±24.04 1602.4±115.39 43.5±0.70 345.5±3.53 6.89±1.28

MGT GT Resin # 10 1679.15±64.84 61.5±0.70 495±21.21 1559.3±536.97 44±5.65 542±4.24 7.56±0.30

MGT GT Resin # 11 1572±73.53 47±4.24 473.37±31.28 1672.25±183.49 43.75±0.35 493±4.24 7.25±1.55

MGT GT Resin # 12 1920±77.78 50±1.41 500±35.35 1720±42.42 45±2.82 675±35.35 7.75±0.21

MGT GT Resin # 17 1716±48.08 53.5±0.70 465±42.42 1600.85±118.86 41±1.41 589±1.41 7.08±0.45

MGT GT Resin # 18 1755±148.49 68±2.82 472.5±53.03 1695.2±188.23 44±1.41 555.625±6.18 7.44±0.28

MGT GT Resin # 20 1516±65.05 57±1.41 501.5±15.55 1632.15±155.91 43.5±0.70 577±2.82 6.93±0.35

MGT GT Resin # 21 1646.25±125.51 67±4.24 498.8±18.80 1436.9±142.69 44.5±3.53 462±36.76 7.50±0.07

MGT GT Resin # 22 1588.15±88.60 67±4.24 497.75±61.16 1553±322.44 43.5±2.12 586.5±2.12 7.55±0.55

MGT GT Resin # 23 1751.6±139.58 55±1.41 438.5±65.76 1654.55±73.60 44.5±2.12 492±2.82 7.00±0.19

MGT GT Resin # 24 1776.45±125.37 61±7.07 482.5±10.60 1661.65±109.81 43±1.41 492.5±3.53 7.38±0.24

166

284


The optimum performance obtained by physical assessment of leather help to optimize the mole

ratio of S/M and G/M for the synthesis of melamine glutaraldehyde based resin. Physical

characteristics of re-tanned leather are graphically explained in Figure 4.40.

285

Figure 4.40: Physical characteristics of re-tanned leather; (a) Effect of MGT Resins on

Tensile Strength of leather fibers perpendicular to backbone; (b) Effect of MGT Resins on %

Elongation leather fibers perpendicular to backbone; (c) Effect of MGT Resins on Tear Strength

of leather fibers perpendicular to backbone; (d) Effect of MGT Resins on Tensile Strength of

leather fibers parallel to backbone; (e) Effect of MGT Resins on % Elongation leather fibers

parallel to backbone; (f) Effect of MGT Resins on Tear Strength of leather fibers parallel to

backbone; (g) Effect of MGT Resins on distension at grain cracking of leather.

It has been noticed from data given in Table 4.35 and figure 4.40 that glyoxylated melamine

based resin (MGT Resin # 12) prepared at mole ratios of 3 and 4 for S/M and G/M respectively

showed maximum values for grain distension of leather surface, tear and tensile strength of leather

fibers. Under these optimum conditions, resin has good cross linking ability with collagen (Leather

fiber protein) to form stabilized composite material.

4.5Organoleptic properties To be an effective retanning agent, the synthetic resinous material should improve the

fullness, softness, grain smoothness, roundness and tightness of the leather, as they are important

parameters especially for making upper leathers. Organoleptic properties of leathers retanned with

stabilized resins of all the series were comparatively evaluated as following against leather

retanned with commercial retanning agent.

286

4.5.1Organoleptic properties of SDH series

Control leather tanned with commercial Resin N.2 and experimental leathers tanned with

stabilized SDH resins were assessed for fullness, softness, grain smoothness, ground roundness

and grain tightness by visual observation and hand feel. Each property was rated from 0-10 points

for both tanned leathers and higher point is given to better property. Comparative organoleptic

properties for both control and experimental leathers are given in Table 4.36 and Figure 4.41,

which shows comparatively better results of leather tanned with SDH resin # 03.

Table 4.36: Organoleptic properties of control and experimental retanned leathers.

Samples Fullness Softness Grain smoothness Grain roundness Grain tightness

Resin N.2 8 7.5 8 7.5 8

SDH # 01 4 2 2 3 2

SDH # 02 6 7 4 6 6

SDH # 03 9 8 9 8 7

SDH # 04 8 8 7 7 7

SDH # 05 3 2 2 3 3

SDH # 06 5 6 5 4 3

SDH # 07 6 5 7 8 6

SDH # 08 7 6 5 7 7

SDH # 09 3 2 2 2 3

SDH # 10 2 2 3 2 2

SDH # 11 8 7 6 5 4

SDH # 12 8 6 5 6 6

SDH # 13 3 2 2 2 3

SDH # 14 3 2 2 2 3

SDH # 15 7 6 5 6 6

SDH # 16 7 5 5 7 5

287

Figure 4.41: Comparison of organoleptic properties of SDH resin series

4.5.2 Organoleptic

properties of GDH series

Control leather tanned with Resin UFT and experimental leathers tanned with stabilized GDH

resins were assessed for fullness, softness, grain smoothness, ground roundness and grain tightness by

visual observation and hand feel. Each property was rated from 0-10 points for both tanned leathers

and higher point is given to better property. Comparative organoleptic properties for both control and

experimental leathers are given in Table 4.37 and in Figure 4.42, which shows comparatively better

results of leather tanned with GDH resin # 09.

Table 4.37: Organoleptic properties of control and experimental retanned leathers

Samples Fullness Softness Grain Smoothness Grain Roundness Grain Tightness

Resin UFT 7.5 7 8 8.5 8

GDH # 01 7 6 6 7 6

GDH # 02 7.5 6.4 6 7.5 6

GDH # 03 6 7 7 6 5

GDH # 04 6 6 5 5 4

GDH # 05 5 5.5 4 4.5 4

GDH # 08 7 6 6 7 6

GDH # 09 8.5 9 8 8 9

288

GDH # 10 7.5 8 7 7 7

GDH # 13 2 3 2 3 2

GDH # 14 6 7 7 7.5 7

GDH # 15 5 6 6 6.5 6

Figure 4.42: Comparison of organoleptic properties of GDH resin series

4.5.3Organoleptic properties of ADH series

Control leather tanned with Resin UFT and experimental leathers tanned with stabilized

ADH resins were assessed for fullness, softness, grain smoothness, ground roundness and grain

tightness by visual observation and hand feel. Each property was rated from 0-10 points for both

tanned leathers and higher point is given to better property. Comparative organoleptic properties

for both control and experimental leathers are given in Table 4.38 and Figure 4.43, which shows

comparatively better results of leather tanned with ADH resin # 02.



Resin UFT 8 7.5 8 9 8

ADH # 01 8 7.5 7 7.5 8

ADH # 02 9 8.5 8 9 9

289

ADH # 03 7.5 7 7 6 7.5

ADH # 04 7 6.5 6 5 6.5

ADH # 05 5 4 4.5 4 3

ADH # 08 5 5.5 4 4 3

ADH # 09 5 6 5 4.5 3.5

ADH # 10 5.5 6.5 6 5 3

ADH # 14 6 7 6.5 5.5 3

ADH # 15 6 6.5 5 4 3

Figure 4.43: Comparison of organoleptic properties of ADH resin series

4.5.4Organoleptic properties of ISPDH series

Control leather tanned with commercial melamine formaldehyde resin and experimental

leathers tanned with stabilized ISPDH resins were assessed for fullness, softness, grain

smoothness, ground roundness and grain tightness by visual observation and hand feel. Each

290

property was rated from 0-10 points for both tanned leathers and higher point is given to better

property. Comparative organoleptic properties for both control and experimental leathers are given

in Table 4.39 and in Figure 4.44, which shows comparatively better results of leather tanned with

ISPDH resin # 04.



Commercial melamine

formaldehyde resin 8 7.5 8 7.5 8

ISPDH # 04 7 6 6 6.5 6

ISPDH # 05 8 7 6.5 7 6

ISPDH # 06 9 8 9 8 7

ISPDH # 07 8 7 8 7 6

ISPDH # 13 9 7 8 8 6

ISPDH # 14 5 6 7 7 6

ISPDH # 22 5 7 6 5 7

ISPDH # 23 9 8 7 7 6

ISPDH # 24 8 7 6.5 7 6

ISPDH # 32 5 6 5.5 6 7

ISPDH # 33 8 7 7 6.5 6

ISPDH # 34 5 5.5 6 6.5 7

291

Figure 4.44: Comparison of organoleptic properties of ISPDH resin series

4.5.5Organoleptic properties of TPDH series

Control leather tanned with conventional amino resin and experimental leathers tanned

with stabilized TPDH resins were assessed for fullness, softness, grain smoothness, ground

roundness and grain tightness by visual observation and hand feel. Each property was rated from

0-10 points for both tanned leathers and higher point is given to better property. Comparative

organoleptic properties for both control and experimental leathers are given in Table 4.40 and in

Figure 4.45, which shows comparatively better results of leather tanned with TPDH resin # 05.



Counter product 8.5 8 7 8 9

TPDH # 04 7 6.5 7 7.5 8

TPDH # 05 9 9.5 8 9 9

TPDH # 06 7 7 6.5 6 7

TPDH # 14 8 8.5 9 8 8

TPDH # 22 7 8 7.5 7 7

292

TPDH # 23 6 7 8 7.5 7

TPDH # 24 7 6 7.5 8 7

TPDH # 33 6 5 6 6.5 6

TPDH # 34 7 8 7.5 8 8

Figure 4.45: Comparison of organoleptic properties of TPDH resin series

4.5.6Organoleptic properties of MGO resin series

Control leather tanned with conventional melamine resin and experimental leathers tanned

with stabilized MGO resins were assessed for fullness, softness, grain smoothness, ground




Figure 4.46, which shows comparatively better results of leather tanned with MGO resin #

24


293


Conventional melamine resin 9 8 8 9 8

MGO Resin # 03 6 7 7 7.5 7

MGO Resin # 04 7 7.5 7 8 7.5

MGO Resin # 05 8 7 6.5 7 7.5

MGO Resin # 09 5 4.5 5 6 7

MGO Resin # 10 5.5 5 6 7 7.5

MGO Resin # 11 6 7 8 7 6

MGO Resin # 12 7.5 8 7 7.5 7

MGO Resin # 14 4 4 5 5 6

MGO Resin # 15 4 3 4 3 5

MGO Resin # 16 6 6 5 4 6

MGO Resin # 17 8 7.5 7 7.5 7

MGO Resin # 18 7 8 7.5 7 7.5

MGO Resin # 20 4 3 6 6.5 6

MGO Resin # 21 5 4 5 7 5.5

MGO Resin # 22 6 5 5 7 6

MGO Resin # 23 7 7.5 8 7 7

MGO Resin # 24 9.5 8 9 8 9

MGO Resin # 25 7 6 7 8 8.5

MGO Resin # 26 7.5 6.5 7 7.5 7

MGO Resin # 27 8 7 7.5 7 6.5

MGO Resin # 28 7 7.5 8 7.5 8

MGO Resin # 29 8 8 7.5 8 8

MGO Resin # 30 7 8 7 7.5 7

294

Figure 4.46: Comparison of organoleptic properties of MGO resin series

4.5.7Organoleptic properties of MGT GT resin series

Control leather tanned with conventional melamine resin and experimental leathers tanned

with stabilized MGT resins were assessed for fullness, softness, grain smoothness, ground



295


Figure 4.47, which shows comparatively better results of leather tanned with MGT resin # 12.



Commercial melamine

resin 9 8 8.5 7 8

MGT GT Resin # 03 7 6 7 6.5 7

MGT GT Resin # 04 7 8 7 8 7

MGT GT Resin # 06 7.5 6 8 7 7.5

MGT GT Resin # 10 8 7 7.5 6 7.5

MGT GT Resin # 11 7.5 8 7 6.5 7

MGT GT Resin # 12 10 9 9 8 9

MGT GT Resin # 17 7 8 6.5 7 6

MGT GT Resin # 18 8.5 7 8 7.5 8

MGT GT Resin # 20 8 7.5 7 8 7

MGT GT Resin # 21 9 8 6.5 7 7.5

MGT GT Resin # 22 7.5 7 8 6.5 6

MGT GT Resin # 23 8 7 8.5 7 9

MGT GT Resin # 24 8 7.5 7 7.5 8

296

Figure 4.47: Comparison of organoleptic properties of MGT GT resin series

297

4.6Comparative thermal analysis

4.6.1Comparative thermal analysis of optimized resins

Figure 4.48: Comparative Thermal Analysis of optimized Resins

Thermo gravimetric analysis was used for calculating the percentage of weight loss of

polymer with increasing temperature. It follows the mass change of a substrate as a function of

temperature or time at a specific temperature field14. As the crosslinking ability of the polymer

increases, it forms stable polymer cross-linked matrix, results in thermal stability.

Thermal degradation of sulfonated succinic dihydrazide formaldehyde resin (precipitated

out in methanol) occurs in four stages as shown in figure 4.48. The percent mass loss 19.45%

occurs at 160oC which corresponds to loss of water entrained in the resin. The second loss of mass

6.31% extends up to 240oC due to release of formaldehyde upon further condensation of the resin.

Radicals are formed above 240oC by crosslinking which induce the cyclic structure formation in

298

the polymer which further undergoes extensive fragments above 300oC. Third degradation step

starts at 240oC and ends at 450oC for the resin. The mass loss in this step is 47.6%, which indicates

degradation of polymer. Fourth degradation step starts at 450oC and goes up to 680oC. The mass

loss percent at this step is 8.33%. The polymer having thermal stability up to 250oC with percent

mass loss up to 7% is good for leather heat fastness. The comparative thermal stability trend was

given below.

Stability of MGO Resin # 24 > Stability of ISPDH Resin # 06 > stability of MGT Resin #

12 > Stability of TPDH Resin # 05 > Stability of ADH # 02 > Stability of SDH Resin # 03 >

Stability of GDH Resin # 09.

4.6.2Study of curing behavior of optimized resins

Figure 4.49: Comparative DSC Analysis of optimized resins.

Curing of the optimized resins was presented by DSC curves as shown in figure 4.49 at a

heating rate of 10oC/minute in the temperature range of 25 to 500oC. As hydrazide modified resins

and non-formaldehyde melamine resins are thermosetting resins, so there curing was an

exothermic reaction. Endothermic and exothermic peaks were shown in the DSC curves. One

299

endothermic peak was shown at about 100oC indicating release of water entrained in the resin.

Obvious exothermic peaks were observed during the curing study of optimized resins. During the

curing reaction of optimized resins, average onset temperature, peak temperature and temperature

at completion of curing are summarized in table 4.43.

Table 4.43: Curing parameters for optimized resins at heating rate of 10oC/min

Resin type Onset Temperature Peak Temperature Temperature at

completion of curing

SDH Resin #03 190 250 280

GDH Resin # 09 213 238 274

ADH Resin # 02 196.98 265 312

ISPDH Resin # 06 239 262 299

TPDH Resin # 05 226 251 275

MGO Resin # 24 230 254 308

MGT Resin # 12 225 250 331

From the table, it can be seen that the onset temperature of SDH Resin # 03 is lower than

all other resins, showing that it polymerizes at lower temperature comparatively to its other resins.

Non-formaldehyde melamine based eco-friendly resins, start polymerization at higher

temperatures of 225oC and 230oC for MGT resin # 12 and MGO Resin # 24 respectively. The

resins with higher temperature at completion of curing have higher thermal stability which is

significantly correlated with the thermal analysis as shown in figure 4.48.

300

4.6.3 Comparative thermal analysis of control leather and optimized

experimental leather

Figure 4.50: Comparative Thermal Analysis of Leathers retanned with optimized Resins.

Thermo gravimetric analysis of retanned leather was performed to calculate the percentage

of weight loss of leather with increasing temperature. Thermo gravimetric analysis follows the

principal of mass change of a substrate as a function of temperature or time at a specific

temperature range14. As the crosslinking ability of the resin increases, it forms stable polymer

cross-linked matrix, results in thermal stability and ultimately increased the thermal stability of the

polymer collagen composite. Comparatively thermal degradation of leathers retanned with

optimized resins and control leather was shown in figure. Experimental retanned leathers have

higher stability as compared to control leather. Control and experimental retanned leathers showed

weight loss of 15-17% upto 100oC due to escape of water entrained in the leather fibers. Different

Weight losses of 63-82% upto 550oC were notices in control and experimental leathers due to

degradation of leather with following thermal stability details.

From the figure 4.50, it is clear that % age of mass change of leather retanned with MGO

Resin # 24 showed upto 63.82% >MGT Resin # 12 upto 65.49% >ISPDH Resin # 06 upto 67.65%

301

>TPDH Resin # 05 upto 68.65%>SDH Resin # 03 upto 69% >ADH Resin # 02 upto

69.52%

>GDH Resin # 09 upto 71.75% > Control Leather upto 82.83%

4.7Scanning electron microscopy

Scanning electron microscopy was performed to deeply observe effects on the skin fiber and grain structure after retanning with

optimized sulfonated formaldehyde condensates of succinic, glutaric, adipic, isophthalic and terephthalic dihydrazides, glyoxylate d

melamine and glutaraldehyde melamine condensates. Scanning electron microscopy of fiber cross section (X50) of animal skins retanned

with optimized formaldehyde dihydrazide condensates and non-formaldehyde melamine condensates were showed in comparison with

control leather in Figure 4.51.

182

Figure 4.51: Scanning electron micrographs of fiber structure cross section (X500) and grain structure (X50). (a) grain surface

of control leather; (b) fiber cross section of control leather; (c) grain surface of SDH resin retanned leather grain; (d) fiber cross section

of SDH resin retanned leather grain; (e) grain surface of GDH resin retanned leather grain; (f) fiber cross section of GDH resin retanned

leather grain; (g) grain surface of ADH resin retanned leather grain; (h) fiber cross section of ADH resin retanned leather grain; (i) grain

surface of ISPDH resin retanned leather grain; (j) fiber cross section of ISPDH resin retanned leather grain; (k) grain surface of TPDH

resin retanned leather grain; (l) fiber cross section of TPDH resin retanned leather grain; (m) grain surface of MGO resin retanned

leather grain; (n) fiber cross section of MGO resin retanned leather grain; (o) grain surface of MGT resin retanned leather grain; (p)

fiber cross section of MGT resin retanned leather grain.

183

199

Examination of skin fibers through SEM cross section of control leather sample showed

the presence of collagen banding pattern and flat grain shown by the grain surface. It was shown

from the figure 4.51 that, as the crosslink density of the resin increased, cross section of the skin

fiber showed better separation of the fibers with low fiber density and grain surface with

compactness. All the optimized resins have shown good cross-linking ability with collagen of

leather to form compact surface with better fiber separation.

CONCLUSION

Novel dihydrazide formaldehyde condensates and non-formaldehyde melamine based

amino resins were prepared. Structures of stabilized resins were elucidated by 1H NMR and FTIR

spectroscopic analysis. Molecular weights of the resins were determined by intrinsic viscosity

method. The variation in trend of the viscosity and molecular weight at constant

Formaldehyde/Dihydrazide mole ratio and varying Sulfonation/Dihydrazide mole ratios were

studied. The results clearly showed that the viscosity and molecular weight of resins showed

increasing trend by increasing Formaldehyde/Dihydrazide mole ratio and decreasing trend by

increasing Sulfonation/dihydrazide mole ratio. Therefore, increasing Formaldehyde/ADH molar

ratio was directly related to molecular weight and increase in viscosity, whereas S/ADH mole ratio

showed inverse relation with molecular weight and viscosity behavior.

Retanning performance of all the resins of the respective series were evaluated against commercial

resin on leather, organoleptic properties and mechanical properties of leather like, tensile, tear, elongation

at break and ball burst of grain were studied comparatively. Most of the resins synthesized at different

conditions showed better performance than commercial resin. A common characteristic was observed that

with increasing degree of formaldehyde, molecular mass of the resin increased which showed little affi nity

with collagen fiber of leather. In the meanwhile, as the degree of sulfonation increased, highly water soluble

resins were produced which showed less substantivity with collagen of skin. Whereas, the resin synthesized

at optimized conditions of reactant mole ratios showed optimum performance as synthetic retanning agent.

200

The results showed that the resin of sulfonated succinct dihydrazide formaldehyde

condensates synthesized at F/SDH ratio 2, and S/SDH ratio 0.3 shows optimum performance as a

synthetic tanning agent. Whereas, the resin of sulfonated glutaric dihydrazide formaldehyde

condensates synthesized at F/GDH mole ratio 2.0 and S/GDH mole ratio 0.4 showed optimum

performance as synthetic retanning agent. In the series of sulfonated dihydrazide formaldehyde

condensates, resin synthesized at F/ADH mole ratio 1, and S/ADH mole ratio 0.2 demonstrated

the maximum performance as a synthetic re-tanning agent. Sulfonated isophthalic dihydrazide

formaldehyde condensates, at constant molar ratio of F/ISPDH of 1.5:1, as the degree of

sulfonation is increased, the resin has better stability in liquid form and also has better retanning

performance with optimum retanning performance at S/ISPDH mole ratio of 0.6:1. In sulfonated

terephthalic dihydrazide formaldehyde condensates, resin synthesized at molar ratio 1.5:1 of

F/TPDH and S/TPDH mole ratio of 0.5:1 showed optimum retanning performance.

The quest to completely eliminate emissions of formaldehyde from leather goods tanned

with synthetic tanning agents is increasing. Currently environmental legislations are focusing on

eliminating formaldehyde containing chemicals from leather processing. Environmental

regulations regarding formaldehyde are not mostly met by formaldehyde based resins even when

formaldehyde is used in minimum concentration.

In non-formaldehyde melamine based research work, formaldehyde was completely

replaced by glyoxal and glutaraldehyde. LD50 value of formaldehyde is about 70-140mg/kg body

weight, while oral LD50 value of glyoxal ranges from 3000-9000mg/kg body weight. Glyoxal has

been classified as non-toxic. Glutaraldehyde is also an industrial available aldehyde used as protein

crosslinking agent and disinfecting agent13. Glutaraldehyde is less harmful than formaldehyde.

LD50 value (oral, rat) for glutaraldehyde is 1470 mg/kg14 than formaldehyde.

Glyoxylated resin synthesized at G/M mole ratio 5 and S/M mole ratio 3 and

Glutaraldehyde melamine condensates synthesized at G/M mole ratio 4 and S/M mole ratio 3

showed maximum retanning performance. Resins with high viscosities were superficially

deposited on the surface

201

giving a harsh grain and a hard handle. As the glyoxal/melamine ratio and

glutaraldehyde/melamine mole ratio increased a greater number of cross-linking sites

developed giving the resins higher astringency towards the skins resulting in a tighter grain and a

harder feel.

Thermal stability of optimized resins and leather retanned with optimized resins clearly

showed that resin with higher crosslinking ability form most stable composite with leather to

increase the heat stability property. Leather retanned with MGO resin and MGT resin showed

higher thermal stability which is also confirmed by their curing behavior evaluated by DSC

analysis.

Grain structure, fiber separation and filling of leather after retanning was assessed by

Scanning electron microscopy and it was found that better fiber separation, compact grain structure

and uniform filling was observed in leather retanned with optimized resins. While other retanned

leathers showed different characteristic, as resins with high viscosities were superficially deposited

on the surface giving a harsh grain and a hard handle. As the cross-linking sites of the resin

increase, its astringency with leather also increase which results in retanning the leather with

tighter grain and harsh feel as also confirmed by evaluating the organoleptic properties of retanned

leathers. All the resins of different series synthesized under optimum conditions show better

thermal stability and less sensitive to fluctuations in pH as compared to commercial retanning

agents and results in better uniform tanning.

Contribution to national development

1- The final outcome of this research work has developed environment friendly amino resins

which can be commercially produced indigenously.

2- By commercial production of these optimized resins, import of tanning materials can be

minimized.

3- REACH and other legislation on export of leather goods are fully satisfied by new

developed amino resins which fulfill all the requirements of export market.

202

Implications for further research

Pakistan is a developing country and dependent on import of leather chemicals. Most of

leather wet end chemicals like, naphthalene based dispersing agents, phenol based bleaching

agents and sulfone based retanning agents are imported. Currently environmental legislations are

progressively focusing on eliminating formaldehyde containing chemicals from leather

processing. Environmental regulations regarding formaldehyde are not mostly covered by

formaldehyde based resins even when formaldehyde is used in minimum concentration. There is

a wide gap of research work in this area of non-formaldehyde working for wet end chemicals based

on naphthalene, phenol and beta-naphthol. Working in this field will open new horizon in the era

of leather science.

203

CHAPTER-5

REFERENCES [1] De Haas, J. A. (1925). Raw-Material Markets, Hides and Skins. USA: A. W. Shaw

Company.

[2] Landmann, W. (2003). The Machines in the Tannery, A Review of Leather Producing

Machinery and Equipment in Current Use. West Yorkshire, UK: World Trades Publishing [3] UK

Leather (2004). Production and Statistics, Retrieved on December 9, 2007 from ukleather.com

(Leather information 2004).

[4] Kite, M., Thomson R. (2006). Conservation of Leather and Related Materials. London,

New York, Boston, Paris, Singapore, Sydney and Tokyo: Elsevier Ltd

[5] FAO Agricultural Services Bulletin 67. (1986). London: Tropical Development and

Research Institute, Overseas Development Administration.

[6] Leather International. (2007, October). Technology: Fire Resistance,

Machinery:

Conveying, 209( 4779), 5-46

[7] Aqueous Finishing for Waterproof Footwear, Benchmarking: Options to Reduce waste,

Yield: Factors within Wet Processes and Operations .World Leather. 21(8), 3-48.

[8] World Footwear Journal, March/April, 2008, 22(2).

[9] R. Bainbridge, Sail 8(1), 142 (1977).

[10] Einhorn, A., Hamburger, A. (1908). Die methylol verbindungen des Harnstoff. Ber. dtsch.

Chem. Ges, 41, 27.

[11] Rossiter, E. C. (all to British Cyanides Co., Ltd.). Brit. Pats. 248,477 (Dec. 5, 1924),

258,950, July 1, 1925, and 266,028, Nov. 5, 1925.

204

[12] Pollak, F. Brit. Pats. 171,096, Nov. 1, 1921. 181,014, May 20, 1922. 193,420, Feb. 17,

1923. 201,906, July 23, 1923. 206,512, July 23, 1923. 213,567, Mar. 31, 1923. 238,904,

Aug. 25, 1924. 270,840, Oct. 1, 1924. 248,729, Mar. 3, 1925.

[13] Bippeb, K. (1923). U.S. Patent No. 1,460,606. Washington, DC: U.S. Patent and

Trademark Office.

[14] Goldschmidt, H., Neuss, O. Brit. Pats. 187,605, Oct. 17, 1922. 202,651, Aug. 17, 1923.

208,761, Sept. 20, 1922.

[15] Hentrich, W., Kohler, R. (both to Henkel and Co., GmbH). Ger. Pat. 647,303, July 6, 1937.

Brit. Pat. 455,008, Oct. 12, 1936.

[16] Rager, R. (1972). Cold runner thermoset molding. Mod. Pla, 49(4), 67.

[17] Drechsel, E. (1876). Ueber das Verhalten des Cyanamids, Dicyandiamids und Melamin

sbeimErhitzen. J. Prakt. Chem, 13(1), 330-333.

[18] Hochwalt, C. A. (1955). U.S. Patent No. 2,727,037. Washington, DC: U.S. Patent and

Trademark Office.

[19] Fromm, D. and co-workers (to Badische Anilin und Soda-Fabrik AG). Ger. Pat. 1,812,120,

June 11, 1970.

[20] Ellwood, P. (1970). Lower investment, easier operation to make melamine. Chemical

Engineering, 77(23), 101.

[21] Walker, J. F. (1964). Formaldehyde, Amer. Chem. Soc. Monograph (3rd ed.) Reinhold,

New York, 159.

[22] U.F. Concentrate-85, Technical Bulletin, Allied Chemical Corp., New York, 1985. [23]

Cleek, G. K. (1964). U.S. Patent No. 3,129,226. Washington, DC: U.S. Patent and

Trademark Office.

[24] Shriver, D. S. (1969). U.S. Patent No. 3,458,464. Washington, DC: U.S. Patent and

Trademark Office.

[25] J. F. Walker, Formaldehyde, American Chemical Society Monograph, No. 159, 3rd ed.,

Reinhold Publishing Corp., New York, 1964. p. 151.

205

[26] N-(iso-butoxymethyl) acrylamide, Technical Bulletin PRC 126, American Cyanamid Co.,

Wayne, N.J. Feb. 1976.

[27] Gordon, M., Halliwell, A., Wilson, T. (1966). Kinetics of the addition stage in the

melamine–formaldehyde reaction. Journal of Applied Polymer Science, 10(8): 1153-1170. [28]

Aldersley, J. W., Gordon, M., Halliwell, A., Wilson, T. (1968). The addition stage in the

melamine-formaldehyde reaction: Computer fittings to the non-random model. Polymer, 9:

345358.

[29] Anderson, I. H., Cawley, M., Steedman, W. (1969). 24 Anderson et al.: Melamine~!-"

ormaldehyde Resins I melamine formaldehyde resins I. An exaivhnation of some model

compound systems. British polymer journal, 1: 24.

[30] Sato, K. (1967). Thermodynamics of the Hydroxymethylation of Melamine and Urea with

Formaldehyde. Bulletin of the Chemical Society of Japan, 40(4), 724-731.

[31] Sato, K., Naito, T. (1973). Studies on Melamine Resin. VII. Kinetics of the AcidCatalyzed

Condensation of Di-and Trimethylolmelamine. Polymer Journal, 5(2), 144-157.

[32] Sato, K., Abe, Y., Sugawara, K. (1975). Studies on melamine resin. X. Acid‐catalyzed

hydrolysis of methylolmelamine. Journal of Polymer Science: Polymer Chemistry

Edition, 13(1), 263-265.

[33] Shenai, V. A., Manjeshwar, J. M. (1974). Kinetics of the reaction between urea and

formaldehyde in the presence of sulfuric acid. Journal of Applied Polymer Science, 18(5),

14071410.

[34] Berge, A., Gudmundsen, S., &Ugelstad, J. (1969). Melamine-formaldehyde compounds—

I The alkaline decomposition of methylolmelamines and

methoxymethylmelamines. European Polymer Journal, 5(1), 171-183.

[35] Berge, A., Kvaeven, B., &Ugelstad, J. (1970). Melamine-formaldehyde compounds—II.

The acid decomposition of methylolmelamines and methoxymethylmelamines. European

Polymer Journal, 6(7), 981-1003.

206

[36] DeJong, J. I., DeJonge, J. Recl. Trav. Chim. 71, 643, 661, 890, 1952; Recl. Trav. Chim. 72,

88, 139, 202, 207, 213, 1027, 1953.

[37] Steele, R. (1960). Catalysis of the reaction of urea–formaldehyde precondensates on

cellulose. J. Appl. Polym. Sci, 4(10), 45-54.

[38] Crowe Jr, G. A., & Lynch, C. C. (1948). Urea formaldehyde kinetic studies.Journal of the

American Chemical Society, 70(11), 3795-3797; Crowe Jr, G. A., & Lynch, C. C. (1950).

Journal of the American Chemical Society, 72(8), 3622-3623.

[39] Elbel, E. Brit. Pat. 829,953, Mar. 9, 1960.

[40] Oldham, W. N. (1961, 1963). U.S. Patent No. 3,007,885, 3,114,930. Washington, DC: U.S.

Patent and Trademark Office.

[41] Koral, J. N. (1972). U.S. Patent No. 3,661,819. Washington, DC: U.S. Patent and

Trademark Office.

[42] Calbo, L. J. (1974). U.S. Patent No. 3,803,095. Washington, DC: U.S. Patent and

Trademark Office.

[43] Lindlaw, W. The Preparation of Butylated Urea—Formaldehyde and Butylated Melamine

Formaldehyde Resins Using Celanese Formcel and Celanese Paraformaldehyde, Technical

Bulletin, Celanese Chemical Co., New York, Table XIIA.

[44] Technical Bulletin S-23-8, 1967, Supplement to Technical Bulletin S-23-8, Celanese

Chemical Co., New York, 1968, Example VIII.

[45] Blank, W. J., & Hensley, W. L. (1974). Use of Amino Crosslinking Agents in WaterBased

Coatings. Journal of Paint Technology, 46(593), 46-50.

[46] Wilson, A. L. (1950). U.S. Patent No. 2,517,750. Washington, DC: U.S. Patent and

Trademark Office.

[47] James, B. W. (1942). U.S. Patent No. 2,304,624. Washington, DC: U.S. Patent and

Trademark Office.

[48] Poon, G. S. Y. (1967). U.S. Patent No. 3,324,062. Washington, DC: U.S. Patent and

Trademark Office.

207

[49] Kadowaki, H. (1936). New compounds of urea-formaldehyde

condensation

products. Bulletin of the Chemical Society of Japan, 11(3), 248-261.

[50] Osfaima, T. (1963). U.S. Patent No. 3,089,859. Washington, DC: U.S. Patent and

Trademark Office.

[51] Reibnitz, B. V. co-workers (BASF); U.S. Pats. 2,731,472, Jan. 17, 1956. 2,764,573, Sept.

25, 1956. Torke, E. (to Phrix-Werke AG). U.S. Pat. 2,876,062, Mar. 3, 1959.

[52] Remley, K. H. (1969). U.S. Patent No. 3,487,088. Washington, DC: U.S. Patent and

Trademark Office.

[53] Gregson, J. E. (1970). U.S. Patent No. 3,524,876. Washington, DC: U.S. Patent and

Trademark Office.

[54] Gale, D. J. (1972). (To Deering Milliken Research Corp.). U.S. Pat. 3,658,458."multistep

reaction of textile materials with multi-functional groups reactive under different catalytic

conditions." U.S. Patent 3,658,458.

[55] Beer, L. U.S. Pats. 2,602,017. 2,602,018, July 1, 1952.

[56] Hasegawa, C. (1942). J. Soc. Chem. Ind. Jpn. 45: 416.

[57] Kaizerman, S. (1965). U.S. Patent No. 3,212,955. Washington, DC: U.S. Patent and

Trademark Office.

[58] Billmers, R. L., Jobe, P. G., Lamb, D. J., Solarek, D. B., Tessler, M. M., Tsai, J. J.

(1988). U.S. Patent No. 4,741,804. Washington, DC: U.S. Pat. and Trademark Office.

[59] Guerro, G. J., Tarvin, R. F. (1986). U.S. Patent No. 4,605,702. Washington, DC: U.S.


[60] Keim, G. I. (1960). U.S. Patent No. 2,926,116. 2,926,154, Washington, DC: U.S. Patent

and Trademark Office.

[61] Wohnsiedler, H. P., Thomas, W. M. (1944). U.S. Patent No. 2,345,543. Washington, DC:

U.S. Patent and Trademark Office.

[62] Landes, C. G., Maxwell, C. S. (1945). A Study of the Melamine Resin Process For

Producing Wet Strength Paper. Technical Association Papers, 205-214.

208

[63] Guender, W., Reuss, G. (to BadischeAnilin-und Soda-Fabrik AG). (1975). Ger. Pat.

2,332,046, Jan. 23.

[64] Dixon, J. K., Christopher, G. L. M., Salley, D. J. (1948). Pap. Trade J. 127(20): 49. [65]

Maxwell, C. S., Landes, C. G. (to American Cyanamid Co.).U.S. Pat. 2,559,220, July 3,

1951.

[66] Maxwell, C. S., House, R. R. (1961). Tappi, 44: 370.

[67] Salley, D. J. Blockman, A. F. (1945). Pap. Trade J. 121(6): 41.

[68] Auten, R. W., & Rainey, J. L. (1946). U.S. Patent No. 2,407,599. Washington, DC: U.S.


[69] Yost, R. S. (1956). U.S. Patent No. 2,742,450. Washington, DC: U.S. Patent and

Trademark Office.

[70] Davidson, J. B., Romatowski, E. J. (1954). U.S. Patent No. 2,683,134. Washington, DC:


[71] Weidner, J. P. ed., Wet Strength in Paper and Paper Board, Monograph Series, No. 29,

Technical Association of Pulp and Paper Industry, New York, 1965.

[72] Britt, K. W. Casey, J. P. ed., Pulp and Paper, Vol. III, John Wiley & Sons, Inc., New York,

1981, Chapt. 18.

[73] Kamutzki, W. (1988). Ind. Carta, 26: 297.

[74] Kamutzki, W. (1987). Kunstharz-Nachr. 24: 9.

[75] Bailey, A. J. (1992). J. Soc. Leath. Tech. Chem, 76: 111-127.

[76] Wren, S., Saddington, M. (1995). Wet white: pretanning with the" Derugan" system. J.

Am. Leather. Chem. Ass (USA), 90: 146-153.

[77] International Glossary of Leather Terms, International Council of Tanners, London,

England, (1968). 1-47.

[78] Gupta, S. D. (1980). J. Soc. Leath. Tech. Chem, 64: 16-23.

[79] Bienkiewicz, K. (1983). Physical Chemistry of Leather Making, Robert E. Krieger

Publishing Company, Malabar, Florida, USA, , Chapters 2-5, 10, 12 and 14-19.

209

[80] Heidemann, E. (1993). Fundamentals of leather manufacture. Roether, Darmstadt,

Germany, 4: 9-12 and 17.

[81] Covington, A. D., Lampard, G. S., Pennington, M. (1998). An investigation of titanium

(III) as a tanning agent. J. Soc. Leath. Tech. Chem, 82(2): 78-80.

[82] Gangopadhyay, S., Lahiri, S., Gangopadhyay, P. K. (2000). Chrome-free tannage by

sequential treatment with synthetic resins and aluminium or titanium. J. Soc. Leath. Tech.

Chem, 84(2): 88.-93.

[83] Covington, A. D. (1987). Tannages based on aluminum (III) + titanium (IV) complexes. J

Am Leath Chem Ass, 82(1): 1-14.

[84] Gaidau, C., Platon, F., Badea, N. (1998). Investigation into iron tannage. J. Soc. Leath.

Tech. Chem, 82(4): 143-146.

[85] Thanikaivelan, P., Geetha, V., Rao, J. R. (2000). A novel chromium-iron tanning agent:

cross-fertilization in solo tannage. Journal J. Soc. Leath. Tech. Chem, 84(2): 82-87.

[86] Slabbert, N. P. (1980). Metal complexes and mineral tanning. Das Leder, 31: 79-82. [87]

Thorstensen, T. C. (1993). Practical Leather Technology, Krieger Publishing Company,

Malabar, USA, 4th Ed., Chapters 4 and 7.

[88] Anonymous, (1997). Pocket Book for the Leather Technologist, BASF, Ludwigshafen,

Germany, 3: 85-128.

[89] Slabbert, N. P. (1999). The basics of practical tanning systems reconciled with vegetable

tanning theories. J. Am. Leather. Chem. Ass, 94(1): 1-7.

[90] Madhan, B., RaghavaRao, J., Subramanian, V., Unninair, B., Ramasami, T. (2004). Role

of phenolics in the stabilization of collagen. J. Am. Leather. Chem. Ass, 99(4): 157-163.

[91] Bickley, J. C. (1992). Vegetable tannins and tanning. J. Soc. Leath. Tech. Chem, 76: 1-5.

[92] Bickley, J. C. (1986). J. Soc. Leath. Tech. Chem, 70: 143-147.

[93] E. Staisny, 50 Years: Synthetic Tannins, BASF, Ludwigshafen, Germany, 1962, 1-45.

[94] SundaraRao, V. S., Reddy, K. K., Nayudamma, Y. (1971). Leather Science, 18: 8-16.


210

[96] Traeubel, H., & Rogge, K. H. (1988). Retannage and retanning materials. J. Am. Leather.

Chem. Ass, 83(6): 193-205.

[97] Thanikaivelan, P., Kanthimathi, M., RaghavaRao, J., Balachandran, U. N. (2002). A novel

formaldehyde-free synthetic chrome tanning agent for pickle-less chrome tanning

comparative study on syntan versus modified basic chromium sulfate. J. Am. Leather.

Chem. Ass, 97(4): 127-136.

[98] Filachione, E. M., Fein, M. L., Harris, Jr. E. H. (1964). "Technical Notes. Tanning with

Glutaraldehyde." JALCA, 59: 281-292.

[99] Cheung, D. T., Perelman, N., Ko, E. C., Nimni, M. E. (1985). Mechanism of crosslinking

of proteins by glutaraldehyde III. Reaction with collagen in tissues.Connective tissue

research, 13(2): 109-115.

[100] Gunasekaran, A., Balasubramanian, K. (1988). Studies on 1, 3-oxazolidine and

3hydroxyethyl-1, 3-oxazolidine as tanning agents. J. Soc. Leath. Tech. Chem, 72: 25-6.

[101] Dasgupta, S. (1977). Oxazolidines new class of tanning agent. J. Soc. Leath. Tech.

Chem, 61(5): 97-105.

[102] Gupta, S. D. (1979). Amino Resins for Leather. J. Soc. Leath. Tech. Chem, 63(3): 49-54.

[103] Morera, J. M., Bartoli, E., Borras, M. D., Marsal, A. (1996). Vegetable-zinc

combination tannage on lambskin. J. Soc. Leath. Tech. Chem, 80(4): 120-122.

[104] Goldfarb, J. (1999). Principles of combination tannage: Chrome plus vegetable. The J. Am.

Leather. Chem. Ass, 94(3): 79-83.

[105] Covington, A. D. (1998). "The 1998 John Arthur Wilson Memorial Lecture: New tannages

for the new millenium. J. Soc. Leath. Tech. Chem, 93(6): 168-182.

[106] Astbury, W. T. (1940). The Molecular Structure of the Fibres of the Collagen Group. Inte

Soc leath trad chem, 24: 69-92.

[107] Miles, C. A., & Bailey, A. J. (1999). Thermal denaturation of collagen revisited. In

Proceedings of the Indian Academy of Sciences-Chemical Sciences, 111(1): 71-80. Springer India.

[108] Weir, C. E., Carter, J. (1950). Rate of shrinkage of tendon collagen. Further effects of

tannage and liquid environment on the activation constants of shrinkage. J. Res. Natl. Bur. Stand.

211

(US), 44: 599.-609.

[109] Sharphouse, J. H. (1985). "Theory and practice of modern chamois leather production." J.

Soc. Leath. Tech. Chem.

[110] Ramasami, T. (2001). "The 42nd John Arthur Wilson Memorial Lecture: Approach

towards a Unified Theory for Tanning. J. Am. Leather. Chem. Ass, 96(8): 290-304.

[111] Covington, A. D., Lampard, G. S., Hancock, R. A., & Ioannidis, I. A. (1998). Studies on

the origin of hydrothermal stability: a new theory of tanning. J. Am. Leather. Chem. Ass, 93(4):

107-120.

[112] Madan, B., Fathima, N. N., Rao, J. R., Subramanian, V., Nair, B. U., Ramasami, T., Leath,

J. A. N. (2003). Chem. Ass. 98: 263-272.

[113] Binetti, R., Costamagna, F. M., & Marcello, I. (2006). Development of carcinogenicity

classifications and evaluations: the case of formaldehyde. Anmali Istituto Superiore Di Sanita,

42(2), 132.

[114] Mahdi, H., Palmina, K., Gurshi, A., & Covington, D. (2009). Potential of vegetable tanning

materials and basic aluminum sulphate in Sudanese leather industry. J. Eng. Sci.

Technol, 4(1), 20-31.

[115] Mohan, C. R., Saravanabhavan, S., Thanikaivelan, P., Rao, J. R., & Nair, B. U. (2008).

Development of formaldehyde-free leathers in the perspective of retanning: part II. Combination

of formaldehyde-free retanning syntans. J. Clean Technologies and Environmental Policy, 10(3),

287-294.

[116] Ansari, M. B., Prasetyanto, E. A., Lee, J., & Park, S. E. (2010). Catalytic behavior of

melamine glyoxal resin towards consecutive oxidation and oxy-Michael addition. Res. Chem.

Intermed, 36(6-7), 677-684.

[117] Akiko, T., Katsuhiko, F., Fumio, N., Yukihiko, H. A. R. A., Masayuki, W., & Satoshi, S.

(2000). Application of green tea catechins as formaldehyde scavengers. ; J. Jpn. Wood Res.

Soc, 46(3), 231-237.

212

[118] Singru, R. N., Zade, A. B., Gurnule, W. B. (2008). Synthesis, characterization, and thermal

degradation studies of copolymer resin derived from p‐cresol, melamine, and formaldehyde. J.

Appl. Polym. Sci, 109(2), 859-868.

[119] Chen, S. H., Wu, W. J., & Ru, J. G. (2008). Synthesis and Application of Melamineglyoxal

Resin. Pap. Chem, 1, 005.

[120] Yun cheng, C., Ping, W., Guang, B. C., Chun bo, L. (2003). Synthesis and Application on

Urea-formaldehyde Resin of Benefit to Environmental Protection, Jilin Normal University Journal

(Natural Science Edition), 3, 19-26.

[121] Luo, Y., Zhu, P. F., Guo, J., Zheng, Z. C., & Shu, W. (2006). Study on low free

formaldehyde urea-formaldehyde resin adhesive. China Adhesives, 7.

[122] Chakraborty, D., Quadery, A. H., & Azad, M. A. K. (2008). Studies on the Tanning with

Glutaraldehyde as an Alternative to Traditional Chrome Tanning System for the Production of

Chrome Free Leather. Bangladesh J. Sci. Ind. Res, 43(4), 553-558.

[123] Myers, G. E. (1984). How mole ratio of UF resin affects formaldehyde emission and other

properties: A literature critique. Forest products journal, 34(5), 35-41.

[124] Li, L. xin., Yang, B., Chen, H. (2002). The synthesis of melamine resin tanning agent. J.

Chem. Res. Appl, 14 (2).

[125] Jahromi, S. (1999). Storage stability of melamine‐formaldehyde resin solutions, the

mechanism of instability. J. Macromol. Sci., Phys, 200(10), 2230-2239.

[126] Jahromi, S., Litvinov, V., Geladé, E. (1999). Physical gelation of melamine formaldehyde

resin solutions. II. A combined light‐scattering and low‐resolution relaxation proton NMR study.

J. Polym. Sci., Part B: Polym. Phys, 37(23), 3307-3318.




[128] Jahromi, S. (1999). The storage stability of melamine formaldehyde resin solutions: III.

Storage at elevated temperatures. J. Polym., 40(18), 5103-5109.

213

[129] Siimer, K., Christjanson, P., Kaljuvee, T., Pehk, T., Lasn, I., & Saks, I. (2008). TG-DTA

study of melamine-urea-formaldehyde resins. J. Therm. Anal. Calorim, 92(1), 19-27.

[130] Yan, H. Y., Kou, K. C., & Zhang, N. (2008). Study on synthetic technology of

ureaformaldehyde resin adhesives with low free formaldehyde content [J].China Adhesives, 8,

004. [131] Lian-xiang, F. E. N. G. (2007). Progress in Modifying Amino Resin Tanning Agents.

J. West Leather, 2, 007.

[132] Yougong, Z., Xiufang, Y., & Yuntao, L. (1996). Synthesis of high stability

polyhydroxymethyl melamine initial condensate solution. J. Fine Chem, 5.

[133] Lixin, L., Honglei, Y., & Wuyong, C. (2004). Synthesis of a new modified amino resin

tanning agent. China Leather, 1, 001.

[134] Yiding, Y. J. S. (2004). Research Actuality and Application Prospect of

Melamineformaldehyde Resin and the Derivatives. Chem. Ind. Tim, 12, 002.

[135] Tomita, B. (1977). Melamine–formaldehyde resins: molecular species distributions of

methylolmelamines and some kinetics of methylolation. J. Polym. Sci: Polym. Chem. Ed, 15(10),

2347-2365.

[136] Ammenn, J., Glocknitzer, F., Tiarks, F., & Wolf, G. (2009). Structure-

ActivityRelationships in synthetic organic tanning agents. In IULTCS Congress.

[137] Rabbii, A. (2001). Synthesis of Water-soluble Highly Sulphonated

Melamineformaldehyde Resin as an Effective Superplasticizer in Concrete. Iranian Pol J, 10, 157-

164. [138] Koloka, O., Moreki, J. C. (2011). Tanning hides and skins using vegetable tanning

agents in Hukuntsi sub-district, Botswana. J. Agric Technol, 7(4), 915-922.

[139] Khalid P. B., Zuber, M. (2009) synthesis and application of melamine urea based

precondensates, AUTEX Res. J, (9) 4.

[140] Siimer, K., Kaljuvee, T., & Christjanson, P. (2003). Thermal behaviour of

ureaformaldehyde resins during curing. J. Therm. Anal. Calorim, 72(2), 607-617.

[141] El-Sayed, N. H., & Nashy, E. S. H. (2002). Synthesis and application of urea

paraformaldehyde polymer as a tanning agent. J. Soc. Leather Technol. Chem, 86(6), 240-248.

214

[142] Li-xin, L. I. Huan Zen, Pan T. (2004). Synthesis of new multi-fuctional amino resin tanning

agent with flame resistance [J]. Chemical Research and Application, 2.

[143] Yun-jun, C. X. Y. L., & Ming-gang, H. U. (2004). Modification of Melamine Resin and

Its Application in Leather Industry. West leacher, 6, 015.

[144] Yougong, Z., Xiufang, Y., Xihuai, Q., & Xuecheng, X. (1999). Synthesis of Aromatic

Amphoteric Retanning Agent. J. China Leather, 5.

[145] DU, G. W., PENG, Z. Y., & WANG, J. T. (2000). Organic Tanning Agent and Its

Development. J. Leather Chem, 5, 001.

[146] Nashy, E. S. H. (2003). Influence of a synthesized condensed polymer as a pre and

retanning agent on the properties of buffalo leather. J. Soc. Leather Technol. Chem, 87(2),

62-68.

[147] Meng, H., Tang L., Zheng W, H. (2003). Synthesis and Use of Melamine Resin-modified

Casein Leather Finishing Agent. J. Leather Chem, (4)

[148] Lu, S. H., Ma, J. Z., & Yang, Z. S. (2001). Synthesis and Study of Amphoteric Vinyl

Polymer Retanning Agent APT. Leather Chemicals, (2).

[149] No, B. Y., & Kim, M. G. (2004). Syntheses and properties of low‐level

melamine‐modified urea–melamine–formaldehyde resins. J. Appl. Polym. Sci, 93(6), 2559-

2569. [150] Baraka, A., Hall, P. J., & Heslop, M. J. (2007). Preparation and characterization of

melamine–formaldehyde–DTPA chelating resin and its use as an adsorbent for heavy metals

removal from wastewater. React. Funct. Polym, 67(7), 585-600.

[151] Su, L., Qiao, S., Xiao, J., Tang, X., Zhao, G., & Fu, S. (2001). Synthesis and properties of

high‐performance and good water‐soluble melamine–formaldehyde resin. J. Appl. Polym. Sci,

81(13), 3268-3271.

[152] Liu, Y. Q., Tian, Y., Zhao, G. Z., Sun, Y. Y., Zhu, F. T., & Cao, Y. (2008). Synthesis of

urea-formaldehyde resin by melt condensation polymerization. J. Polym. Res, 15(6), 501-505.

[153] Huang, Y., Jones, F. N. (1996). Synthesis of crosslinkable acrylic latexes by emulsion

polymerization in the presence of etherified melamine-formaldehyde (MF) resins. Prog. Org.

Coat, 28(2), 133-141.

215

[154] Zeng, X. J., Chen, Y. D., Su, Z. X., & Lu, Z. P. (2009). Synthesis of a novel

melamineglyoxal condensed polymer decolorizing flocculant and its application. Ind.

Water & Wastewater, 40(4), 67-69.

[155] Simon, C., Pizzi, A. (2002). Tannins/melamine–urea–formaldehyde (MUF) resins

substitution of chrome in leather and its characterization by thermomechanical analysis. J.

Appl. Polym. Sci, 88(8), 1889-1903.

[156] Zengin, A. C. A., Crudu, M., Maier, S. S., Deselnicu, V., Albu, L., Gulumser, G., ... &

Mutlu, M. M. (2012). Eco-leather: Chromium-free leather production using Titanium,

Oligomeric Melamine-Formaldehyde Resin, and Resorcinol Tanning Agents and the

Properties of the Resulting Leathers. Ekoloji, 21(82), 17-25.

[157] Eaton, A. D., & Franson, M. A. (2005). Standard methods for the examination of water &

wastewater, 17th ed. American Public Health Association.

[158] ASTM D2983 – 09 Standard Test Method for Low-Temperature Viscosity of Lubricants

Measured by Brookfield Viscometer

[159] ASTM D5355 - 95(2012) Standard Test Method for Specific Gravity of Oils and Liquid

Fats

[160] ASTM E70 - 07 Standard Test Method for pH of Aqueous Solutions With the Glass

Electrode

[161] ASTM D2194 - 02(2012) Standard Test Method for Concentration of Formaldehyde

Solutions

[162] Smith, B. C. (2011). Fundamentals of Fourier transform infrared spectroscopy. CRC

press.

[163] Ullah, S., Bustam, M. A., Nadeem, M., Naz, M. Y., Tan, W. L., & Shariff, A. M. (2014).

Synthesis and Thermal Degradation Studies of Melamine Formaldehyde Resins. ; The

Scientific World Journal, 2014, 1-6.

[164] IUP 3 (2006) Sample preparation and conditioning, ISO 2419.

[165] IUP 6 (2002) Measurement of tensile strength and percentage elongation, ISO 3376.

[166] IUP 8 (2002) Measurement of tear load - Double edge tear, ISO 3377-2.

216

[167] IUP 9 (1976) Measurement of distension and strength of grain by the ball burst test, ISO

3379.

[168] IUC 19-2 (2008), Determination of formaldehyde content in leather Part 1: Quantification

by colorimetric analysis, ISO 17226-2.

[169] IUP 2 (2002), Sampling location, ISO 2418.

Annexes

Figure 4.52: FTIR Spectrum of optimized SDH Resin # 03

218

Figure 4.53: H 1 NMR Spectrum of optimized SDH resin # 03

220

Figure 4.54: FTIR Spectrum of optimized GDH Resin # 09

222

Figure 4.55: GDH resin # 09

223

Figure 4.56: FTIR Spectrum of optimized ADH Resin # 02

225

Figure 4.57: ADH resin # 02

226

Figure 4.58: FTIR Spectrum of optimized ISPDH Resin # 06

227

Figure 4.59: ISPDH resin # 06

229

Figure 4.60: FTIR Spectrum of optimized TPDH Resin # 05

231

Figure 4.61:NMR Spectrum of optimized TPDH resin # 05

Figure 4.62: FTIR Spectrum of optimized MGO Resin # 24

233

Figure 4.63: H 1 NMR Spectrum of optimized MGO Resin # 24 Figure 4.64: FTIR

Spectrum of optimized MGT Resin # 12

235

Figure 4.65: H 1 NMR Spectrum of optimized MGT Resin # 12

CHAPTER-5

REFERENCES [3] De Haas, J. A. (1925). Raw-Material Markets, Hides and Skins. USA: A. W. Shaw

Company.

[4] Landmann, W. (2003). The Machines in the Tannery, A Review of Leather Producing

Machinery and Equipment in Current Use. West Yorkshire, UK: World Trades Publishing [3] UK

Leather (2004). Production and Statistics, Retrieved on December 9, 2007 from ukleather.com

(Leather information 2004).

[23] Kite, M., Thomson R. (2006). Conservation of Leather and Related Materials. London,

New York, Boston, Paris, Singapore, Sydney and Tokyo: Elsevier Ltd

[24] FAO Agricultural Services Bulletin 67. (1986). London: Tropical Development and

Research Institute, Overseas Development Administration.

[25] Leather International. (2007, October). Technology: Fire Resistance,

Machinery:

Conveying, 209( 4779), 5-46

[26] Aqueous Finishing for Waterproof Footwear, Benchmarking: Options to Reduce waste,

Yield: Factors within Wet Processes and Operations .World Leather. 21(8), 3-48.

[27] World Footwear Journal, March/April, 2008, 22(2).

[28] R. Bainbridge, Sail 8(1), 142 (1977).

[29] Einhorn, A., Hamburger, A. (1908). Die methylol verbindungen des Harnstoff. Ber. dtsch.

Chem. Ges, 41, 27.

[30] Rossiter, E. C. (all to British Cyanides Co., Ltd.). Brit. Pats. 248,477 (Dec. 5, 1924),

258,950, July 1, 1925, and 266,028, Nov. 5, 1925.

236

[31] Pollak, F. Brit. Pats. 171,096, Nov. 1, 1921. 181,014, May 20, 1922. 193,420, Feb. 17,

1923. 201,906, July 23, 1923. 206,512, July 23, 1923. 213,567, Mar. 31, 1923. 238,904,

Aug. 25, 1924. 270,840, Oct. 1, 1924. 248,729, Mar. 3, 1925.

[32] Bippeb, K. (1923). U.S. Patent No. 1,460,606. Washington, DC: U.S. Patent and

Trademark Office.

[33] Goldschmidt, H., Neuss, O. Brit. Pats. 187,605, Oct. 17, 1922. 202,651, Aug. 17, 1923.

208,761, Sept. 20, 1922.

[34] Hentrich, W., Kohler, R. (both to Henkel and Co., GmbH). Ger. Pat. 647,303, July 6, 1937.

Brit. Pat. 455,008, Oct. 12, 1936.

[35] Rager, R. (1972). Cold runner thermoset molding. Mod. Pla, 49(4), 67.

[36] Drechsel, E. (1876). Ueber das Verhalten des Cyanamids, Dicyandiamids und Melamin

sbeimErhitzen. J. Prakt. Chem, 13(1), 330-333.

[37] Hochwalt, C. A. (1955). U.S. Patent No. 2,727,037. Washington, DC: U.S. Patent and

Trademark Office.

[38] Fromm, D. and co-workers (to Badische Anilin und Soda-Fabrik AG). Ger. Pat. 1,812,120,

June 11, 1970.

[39] Ellwood, P. (1970). Lower investment, easier operation to make melamine. Chemical

Engineering, 77(23), 101.

[40] Walker, J. F. (1964). Formaldehyde, Amer. Chem. Soc. Monograph (3rd ed.) Reinhold,

New York, 159.

[41] U.F. Concentrate-85, Technical Bulletin, Allied Chemical Corp., New York, 1985. [23]

Cleek, G. K. (1964). U.S. Patent No. 3,129,226. Washington, DC: U.S. Patent and

Trademark Office.

[28] Shriver, D. S. (1969). U.S. Patent No. 3,458,464. Washington, DC: U.S. Patent and

Trademark Office.

[29] J. F. Walker, Formaldehyde, American Chemical Society Monograph, No. 159, 3rd ed.,

Reinhold Publishing Corp., New York, 1964. p. 151.

237

[30] N-(iso-butoxymethyl) acrylamide, Technical Bulletin PRC 126, American Cyanamid Co.,

Wayne, N.J. Feb. 1976.

[31] Gordon, M., Halliwell, A., Wilson, T. (1966). Kinetics of the addition stage in the

melamine–formaldehyde reaction. Journal of Applied Polymer Science, 10(8): 1153-1170. [28]

Aldersley, J. W., Gordon, M., Halliwell, A., Wilson, T. (1968). The addition stage in the

melamine-formaldehyde reaction: Computer fittings to the non-random model. Polymer, 9:

345358.

[65] Anderson, I. H., Cawley, M., Steedman, W. (1969). 24 Anderson et al.: Melamine~!-"

ormaldehyde Resins I melamine formaldehyde resins I. An exaivhnation of some model

compound systems. British polymer journal, 1: 24.

[66] Sato, K. (1967). Thermodynamics of the Hydroxymethylation of Melamine and Urea with

Formaldehyde. Bulletin of the Chemical Society of Japan, 40(4), 724-731.

[67] Sato, K., Naito, T. (1973). Studies on Melamine Resin. VII. Kinetics of the AcidCatalyzed

Condensation of Di-and Trimethylolmelamine. Polymer Journal, 5(2), 144-157.

[68] Sato, K., Abe, Y., Sugawara, K. (1975). Studies on melamine resin. X. Acid‐catalyzed

hydrolysis of methylolmelamine. Journal of Polymer Science: Polymer Chemistry

Edition, 13(1), 263-265.

[69] Shenai, V. A., Manjeshwar, J. M. (1974). Kinetics of the reaction between urea and

formaldehyde in the presence of sulfuric acid. Journal of Applied Polymer Science, 18(5),

14071410.

[70] Berge, A., Gudmundsen, S., &Ugelstad, J. (1969). Melamine-formaldehyde compounds—

I The alkaline decomposition of methylolmelamines and

methoxymethylmelamines. European Polymer Journal, 5(1), 171-183.

[71] Berge, A., Kvaeven, B., &Ugelstad, J. (1970). Melamine-formaldehyde compounds—II.

The acid decomposition of methylolmelamines and methoxymethylmelamines. European

Polymer Journal, 6(7), 981-1003.

238

[72] DeJong, J. I., DeJonge, J. Recl. Trav. Chim. 71, 643, 661, 890, 1952; Recl. Trav. Chim. 72,

88, 139, 202, 207, 213, 1027, 1953.

[73] Steele, R. (1960). Catalysis of the reaction of urea–formaldehyde precondensates on

cellulose. J. Appl. Polym. Sci, 4(10), 45-54.

[74] Crowe Jr, G. A., & Lynch, C. C. (1948). Urea formaldehyde kinetic studies.Journal of the

American Chemical Society, 70(11), 3795-3797; Crowe Jr, G. A., & Lynch, C. C. (1950).

Journal of the American Chemical Society, 72(8), 3622-3623.

[75] Elbel, E. Brit. Pat. 829,953, Mar. 9, 1960.

[76] Oldham, W. N. (1961, 1963). U.S. Patent No. 3,007,885, 3,114,930. Washington, DC: U.S.


[77] Koral, J. N. (1972). U.S. Patent No. 3,661,819. Washington, DC: U.S. Patent and

Trademark Office.

[78] Calbo, L. J. (1974). U.S. Patent No. 3,803,095. Washington, DC: U.S. Patent and

Trademark Office.

[79] Lindlaw, W. The Preparation of Butylated Urea—Formaldehyde and Butylated Melamine

Formaldehyde Resins Using Celanese Formcel and Celanese Paraformaldehyde, Technical

Bulletin, Celanese Chemical Co., New York, Table XIIA.

[80] Technical Bulletin S-23-8, 1967, Supplement to Technical Bulletin S-23-8, Celanese

Chemical Co., New York, 1968, Example VIII.

[81] Blank, W. J., & Hensley, W. L. (1974). Use of Amino Crosslinking Agents in WaterBased

Coatings. Journal of Paint Technology, 46(593), 46-50.

[82] Wilson, A. L. (1950). U.S. Patent No. 2,517,750. Washington, DC: U.S. Patent and

Trademark Office.

[83] James, B. W. (1942). U.S. Patent No. 2,304,624. Washington, DC: U.S. Patent and

Trademark Office.

[84] Poon, G. S. Y. (1967). U.S. Patent No. 3,324,062. Washington, DC: U.S. Patent and

Trademark Office.

[85] Kadowaki, H. (1936). New compounds of urea-formaldehyde

condensation

239

products. Bulletin of the Chemical Society of Japan, 11(3), 248-261.

[86] Osfaima, T. (1963). U.S. Patent No. 3,089,859. Washington, DC: U.S. Patent and

Trademark Office.

[87] Reibnitz, B. V. co-workers (BASF); U.S. Pats. 2,731,472, Jan. 17, 1956. 2,764,573, Sept.

25, 1956. Torke, E. (to Phrix-Werke AG). U.S. Pat. 2,876,062, Mar. 3, 1959.

[88] Remley, K. H. (1969). U.S. Patent No. 3,487,088. Washington, DC: U.S. Patent and

Trademark Office.

[89] Gregson, J. E. (1970). U.S. Patent No. 3,524,876. Washington, DC: U.S. Patent and

Trademark Office.

[90] Gale, D. J. (1972). (To Deering Milliken Research Corp.). U.S. Pat. 3,658,458."multistep

reaction of textile materials with multi-functional groups reactive under different catalytic

conditions." U.S. Patent 3,658,458.

[91] Beer, L. U.S. Pats. 2,602,017. 2,602,018, July 1, 1952.

[92] Hasegawa, C. (1942). J. Soc. Chem. Ind. Jpn. 45: 416.

[93] Kaizerman, S. (1965). U.S. Patent No. 3,212,955. Washington, DC: U.S. Patent and

Trademark Office.

[94] Billmers, R. L., Jobe, P. G., Lamb, D. J., Solarek, D. B., Tessler, M. M., Tsai, J. J.

(1988). U.S. Patent No. 4,741,804. Washington, DC: U.S. Pat. and Trademark Office.

[95] Guerro, G. J., Tarvin, R. F. (1986). U.S. Patent No. 4,605,702. Washington, DC: U.S.


[96] Keim, G. I. (1960). U.S. Patent No. 2,926,116. 2,926,154, Washington, DC: U.S. Patent

and Trademark Office.

[97] Wohnsiedler, H. P., Thomas, W. M. (1944). U.S. Patent No. 2,345,543. Washington, DC:


[98] Landes, C. G., Maxwell, C. S. (1945). A Study of the Melamine Resin Process For

Producing Wet Strength Paper. Technical Association Papers, 205-214.

[99] Guender, W., Reuss, G. (to BadischeAnilin-und Soda-Fabrik AG). (1975). Ger. Pat.

2,332,046, Jan. 23.

240

[100] Dixon, J. K., Christopher, G. L. M., Salley, D. J. (1948). Pap. Trade J. 127(20): 49. [65]

Maxwell, C. S., Landes, C. G. (to American Cyanamid Co.).U.S. Pat. 2,559,220, July 3,

1951.

[87] Maxwell, C. S., House, R. R. (1961). Tappi, 44: 370.

[88] Salley, D. J. Blockman, A. F. (1945). Pap. Trade J. 121(6): 41.

[89] Auten, R. W., & Rainey, J. L. (1946). U.S. Patent No. 2,407,599. Washington, DC: U.S.


[90] Yost, R. S. (1956). U.S. Patent No. 2,742,450. Washington, DC: U.S. Patent and

Trademark Office.

[91] Davidson, J. B., Romatowski, E. J. (1954). U.S. Patent No. 2,683,134. Washington, DC:


[92] Weidner, J. P. ed., Wet Strength in Paper and Paper Board, Monograph Series, No. 29,

Technical Association of Pulp and Paper Industry, New York, 1965.

[93] Britt, K. W. Casey, J. P. ed., Pulp and Paper, Vol. III, John Wiley & Sons, Inc., New York,

1981, Chapt. 18.

[94] Kamutzki, W. (1988). Ind. Carta, 26: 297.

[95] Kamutzki, W. (1987). Kunstharz-Nachr. 24: 9.

[96] Bailey, A. J. (1992). J. Soc. Leath. Tech. Chem, 76: 111-127.

[97] Wren, S., Saddington, M. (1995). Wet white: pretanning with the" Derugan" system. J. Am.

Leather. Chem. Ass (USA), 90: 146-153.

[98] International Glossary of Leather Terms, International Council of Tanners, London,

England, (1968). 1-47.

[99] Gupta, S. D. (1980). J. Soc. Leath. Tech. Chem, 64: 16-23.

[100] Bienkiewicz, K. (1983). Physical Chemistry of Leather Making, Robert E. Krieger

Publishing Company, Malabar, Florida, USA, , Chapters 2-5, 10, 12 and 14-19.

[101] Heidemann, E. (1993). Fundamentals of leather manufacture. Roether, Darmstadt,

Germany, 4: 9-12 and 17.

241

[102] Covington, A. D., Lampard, G. S., Pennington, M. (1998). An investigation of titanium

(III) as a tanning agent. J. Soc. Leath. Tech. Chem, 82(2): 78-80.

[103] Gangopadhyay, S., Lahiri, S., Gangopadhyay, P. K. (2000). Chrome-free tannage by

sequential treatment with synthetic resins and aluminium or titanium. J. Soc. Leath. Tech.

Chem, 84(2): 88.-93.

[104] Covington, A. D. (1987). Tannages based on aluminum (III) + titanium (IV) complexes. J

Am Leath Chem Ass, 82(1): 1-14.

[105] Gaidau, C., Platon, F., Badea, N. (1998). Investigation into iron tannage. J. Soc. Leath.

Tech. Chem, 82(4): 143-146.

[106] Thanikaivelan, P., Geetha, V., Rao, J. R. (2000). A novel chromium-iron tanning agent:

cross-fertilization in solo tannage. Journal J. Soc. Leath. Tech. Chem, 84(2): 82-87.

[107] Slabbert, N. P. (1980). Metal complexes and mineral tanning. Das Leder, 31: 79-82. [87]

Thorstensen, T. C. (1993). Practical Leather Technology, Krieger Publishing Company,

Malabar, USA, 4th Ed., Chapters 4 and 7.

[103] Anonymous, (1997). Pocket Book for the Leather Technologist, BASF, Ludwigshafen,

Germany, 3: 85-128.

[104] Slabbert, N. P. (1999). The basics of practical tanning systems reconciled with vegetable

tanning theories. J. Am. Leather. Chem. Ass, 94(1): 1-7.

[105] Madhan, B., RaghavaRao, J., Subramanian, V., Unninair, B., Ramasami, T. (2004). Role

of phenolics in the stabilization of collagen. J. Am. Leather. Chem. Ass, 99(4): 157-163.

[106] Bickley, J. C. (1992). Vegetable tannins and tanning. J. Soc. Leath. Tech. Chem, 76: 1-5.

[107] Bickley, J. C. (1986). J. Soc. Leath. Tech. Chem, 70: 143-147.

[108] E. Staisny, 50 Years: Synthetic Tannins, BASF, Ludwigshafen, Germany, 1962, 1-45.



[111] Traeubel, H., & Rogge, K. H. (1988). Retannage and retanning materials. J. Am. Leather.

Chem. Ass, 83(6): 193-205.

242

[112] Thanikaivelan, P., Kanthimathi, M., RaghavaRao, J., Balachandran, U. N. (2002). A novel

formaldehyde-free synthetic chrome tanning agent for pickle-less chrome tanning

comparative study on syntan versus modified basic chromium sulfate. J. Am. Leather.

Chem. Ass, 97(4): 127-136.

[113] Filachione, E. M., Fein, M. L., Harris, Jr. E. H. (1964). "Technical Notes. Tanning with

Glutaraldehyde." JALCA, 59: 281-292.

[114] Cheung, D. T., Perelman, N., Ko, E. C., Nimni, M. E. (1985). Mechanism of crosslinking

of proteins by glutaraldehyde III. Reaction with collagen in tissues.Connective tissue

research, 13(2): 109-115.

[115] Gunasekaran, A., Balasubramanian, K. (1988). Studies on 1, 3-oxazolidine and

3hydroxyethyl-1, 3-oxazolidine as tanning agents. J. Soc. Leath. Tech. Chem, 72: 25-6.

[116] Dasgupta, S. (1977). Oxazolidines new class of tanning agent. J. Soc. Leath. Tech.

Chem, 61(5): 97-105.

[117] Gupta, S. D. (1979). Amino Resins for Leather. J. Soc. Leath. Tech. Chem, 63(3): 49-54.

[103] Morera, J. M., Bartoli, E., Borras, M. D., Marsal, A. (1996). Vegetable-zinc

combination tannage on lambskin. J. Soc. Leath. Tech. Chem, 80(4): 120-122.

[131] Goldfarb, J. (1999). Principles of combination tannage: Chrome plus vegetable. The J. Am.

Leather. Chem. Ass, 94(3): 79-83.

[132] Covington, A. D. (1998). "The 1998 John Arthur Wilson Memorial Lecture: New tannages

for the new millenium. J. Soc. Leath. Tech. Chem, 93(6): 168-182.

[133] Astbury, W. T. (1940). The Molecular Structure of the Fibres of the Collagen Group. Inte

Soc leath trad chem, 24: 69-92.

[134] Miles, C. A., & Bailey, A. J. (1999). Thermal denaturation of collagen revisited. In

Proceedings of the Indian Academy of Sciences-Chemical Sciences, 111(1): 71-80. Springer India.

[135] Weir, C. E., Carter, J. (1950). Rate of shrinkage of tendon collagen. Further effects of

tannage and liquid environment on the activation constants of shrinkage. J. Res. Natl. Bur. Stand.

(US), 44: 599.-609.

243

[136] Sharphouse, J. H. (1985). "Theory and practice of modern chamois leather production." J.

Soc. Leath. Tech. Chem.

[137] Ramasami, T. (2001). "The 42nd John Arthur Wilson Memorial Lecture: Approach

towards a Unified Theory for Tanning. J. Am. Leather. Chem. Ass, 96(8): 290-304.

[138] Covington, A. D., Lampard, G. S., Hancock, R. A., & Ioannidis, I. A. (1998). Studies on

the origin of hydrothermal stability: a new theory of tanning. J. Am. Leather. Chem. Ass, 93(4):

107-120.

[139] Madan, B., Fathima, N. N., Rao, J. R., Subramanian, V., Nair, B. U., Ramasami, T., Leath,

J. A. N. (2003). Chem. Ass. 98: 263-272.

[140] Binetti, R., Costamagna, F. M., & Marcello, I. (2006). Development of carcinogenicity

classifications and evaluations: the case of formaldehyde. Anmali Istituto Superiore Di Sanita,

42(2), 132.

[141] Mahdi, H., Palmina, K., Gurshi, A., & Covington, D. (2009). Potential of vegetable tanning

materials and basic aluminum sulphate in Sudanese leather industry. J. Eng. Sci.

Technol, 4(1), 20-31.

[142] Mohan, C. R., Saravanabhavan, S., Thanikaivelan, P., Rao, J. R., & Nair, B. U. (2008).

Development of formaldehyde-free leathers in the perspective of retanning: part II. Combination

of formaldehyde-free retanning syntans. J. Clean Technologies and Environmental Policy, 10(3),

287-294.

[143] Ansari, M. B., Prasetyanto, E. A., Lee, J., & Park, S. E. (2010). Catalytic behavior of

melamine glyoxal resin towards consecutive oxidation and oxy-Michael addition. Res. Chem.

Intermed, 36(6-7), 677-684.

[144] Akiko, T., Katsuhiko, F., Fumio, N., Yukihiko, H. A. R. A., Masayuki, W., & Satoshi, S.

(2000). Application of green tea catechins as formaldehyde scavengers. ; J. Jpn. Wood Res.

Soc, 46(3), 231-237.

[145] Singru, R. N., Zade, A. B., Gurnule, W. B. (2008). Synthesis, characterization, and thermal

degradation studies of copolymer resin derived from p‐cresol, melamine, and formaldehyde. J.

Appl. Polym. Sci, 109(2), 859-868.

244

[146] Chen, S. H., Wu, W. J., & Ru, J. G. (2008). Synthesis and Application of Melamineglyoxal

Resin. Pap. Chem, 1, 005.

[147] Yun cheng, C., Ping, W., Guang, B. C., Chun bo, L. (2003). Synthesis and Application on

Urea-formaldehyde Resin of Benefit to Environmental Protection, Jilin Normal University Journal

(Natural Science Edition), 3, 19-26.

[148] Luo, Y., Zhu, P. F., Guo, J., Zheng, Z. C., & Shu, W. (2006). Study on low free

formaldehyde urea-formaldehyde resin adhesive. China Adhesives, 7.

[149] Chakraborty, D., Quadery, A. H., & Azad, M. A. K. (2008). Studies on the Tanning with

Glutaraldehyde as an Alternative to Traditional Chrome Tanning System for the Production of

Chrome Free Leather. Bangladesh J. Sci. Ind. Res, 43(4), 553-558.

[150] Myers, G. E. (1984). How mole ratio of UF resin affects formaldehyde emission and other

properties: A literature critique. Forest products journal, 34(5), 35-41.

[151] Li, L. xin., Yang, B., Chen, H. (2002). The synthesis of melamine resin tanning agent. J.

Chem. Res. Appl, 14 (2).

[152] Jahromi, S. (1999). Storage stability of melamine‐formaldehyde resin solutions, the

mechanism of instability. J. Macromol. Sci., Phys, 200(10), 2230-2239.







[155] Jahromi, S. (1999). The storage stability of melamine formaldehyde resin solutions: III.

Storage at elevated temperatures. J. Polym., 40(18), 5103-5109.

[156] Siimer, K., Christjanson, P., Kaljuvee, T., Pehk, T., Lasn, I., & Saks, I. (2008). TG-DTA

study of melamine-urea-formaldehyde resins. J. Therm. Anal. Calorim, 92(1), 19-27.

[157] Yan, H. Y., Kou, K. C., & Zhang, N. (2008). Study on synthetic technology of

ureaformaldehyde resin adhesives with low free formaldehyde content [J].China Adhesives, 8,

245

004. [131] Lian-xiang, F. E. N. G. (2007). Progress in Modifying Amino Resin Tanning Agents.

J. West Leather, 2, 007.

[138] Yougong, Z., Xiufang, Y., & Yuntao, L. (1996). Synthesis of high stability

polyhydroxymethyl melamine initial condensate solution. J. Fine Chem, 5.

[139] Lixin, L., Honglei, Y., & Wuyong, C. (2004). Synthesis of a new modified amino resin

tanning agent. China Leather, 1, 001.

[140] Yiding, Y. J. S. (2004). Research Actuality and Application Prospect of

Melamineformaldehyde Resin and the Derivatives. Chem. Ind. Tim, 12, 002.

[141] Tomita, B. (1977). Melamine–formaldehyde resins: molecular species distributions of

methylolmelamines and some kinetics of methylolation. J. Polym. Sci: Polym. Chem. Ed, 15(10),

2347-2365.

[142] Ammenn, J., Glocknitzer, F., Tiarks, F., & Wolf, G. (2009). Structure-

ActivityRelationships in synthetic organic tanning agents. In IULTCS Congress.

[143] Rabbii, A. (2001). Synthesis of Water-soluble Highly Sulphonated

Melamineformaldehyde Resin as an Effective Superplasticizer in Concrete. Iranian Pol J, 10, 157-

164. [138] Koloka, O., Moreki, J. C. (2011). Tanning hides and skins using vegetable tanning

agents in Hukuntsi sub-district, Botswana. J. Agric Technol, 7(4), 915-922.

[142] Khalid P. B., Zuber, M. (2009) synthesis and application of melamine urea based

precondensates, AUTEX Res. J, (9) 4.

[143] Siimer, K., Kaljuvee, T., & Christjanson, P. (2003). Thermal behaviour of

ureaformaldehyde resins during curing. J. Therm. Anal. Calorim, 72(2), 607-617.

[144] El-Sayed, N. H., & Nashy, E. S. H. (2002). Synthesis and application of urea

paraformaldehyde polymer as a tanning agent. J. Soc. Leather Technol. Chem, 86(6), 240-248.

[142] Li-xin, L. I. Huan Zen, Pan T. (2004). Synthesis of new multi-fuctional amino resin tanning

agent with flame resistance [J]. Chemical Research and Application, 2.

[150] Yun-jun, C. X. Y. L., & Ming-gang, H. U. (2004). Modification of Melamine Resin and

Its Application in Leather Industry. West leacher, 6, 015.

246

[151] Yougong, Z., Xiufang, Y., Xihuai, Q., & Xuecheng, X. (1999). Synthesis of Aromatic

Amphoteric Retanning Agent. J. China Leather, 5.

[152] DU, G. W., PENG, Z. Y., & WANG, J. T. (2000). Organic Tanning Agent and Its

Development. J. Leather Chem, 5, 001.

[153] Nashy, E. S. H. (2003). Influence of a synthesized condensed polymer as a pre and

retanning agent on the properties of buffalo leather. J. Soc. Leather Technol. Chem, 87(2),

62-68.

[154] Meng, H., Tang L., Zheng W, H. (2003). Synthesis and Use of Melamine Resin-modified

Casein Leather Finishing Agent. J. Leather Chem, (4)

[155] Lu, S. H., Ma, J. Z., & Yang, Z. S. (2001). Synthesis and Study of Amphoteric Vinyl

Polymer Retanning Agent APT. Leather Chemicals, (2).

[156] No, B. Y., & Kim, M. G. (2004). Syntheses and properties of low‐level

melamine‐modified urea–melamine–formaldehyde resins. J. Appl. Polym. Sci, 93(6), 2559-

2569. [150] Baraka, A., Hall, P. J., & Heslop, M. J. (2007). Preparation and characterization of

melamine–formaldehyde–DTPA chelating resin and its use as an adsorbent for heavy metals

removal from wastewater. React. Funct. Polym, 67(7), 585-600.

[153] Su, L., Qiao, S., Xiao, J., Tang, X., Zhao, G., & Fu, S. (2001). Synthesis and properties of

high‐performance and good water‐soluble melamine–formaldehyde resin. J. Appl. Polym. Sci,

81(13), 3268-3271.

[154] Liu, Y. Q., Tian, Y., Zhao, G. Z., Sun, Y. Y., Zhu, F. T., & Cao, Y. (2008). Synthesis of

urea-formaldehyde resin by melt condensation polymerization. J. Polym. Res, 15(6), 501-505.

[153] Huang, Y., Jones, F. N. (1996). Synthesis of crosslinkable acrylic latexes by emulsion

polymerization in the presence of etherified melamine-formaldehyde (MF) resins. Prog. Org.

Coat, 28(2), 133-141.

[170] Zeng, X. J., Chen, Y. D., Su, Z. X., & Lu, Z. P. (2009). Synthesis of a novel

melamineglyoxal condensed polymer decolorizing flocculant and its application. Ind.

Water & Wastewater, 40(4), 67-69.

247

[171] Simon, C., Pizzi, A. (2002). Tannins/melamine–urea–formaldehyde (MUF) resins

substitution of chrome in leather and its characterization by thermomechanical analysis. J.

Appl. Polym. Sci, 88(8), 1889-1903.

[172] Zengin, A. C. A., Crudu, M., Maier, S. S., Deselnicu, V., Albu, L., Gulumser, G., ... &

Mutlu, M. M. (2012). Eco-leather: Chromium-free leather production using Titanium,

Oligomeric Melamine-Formaldehyde Resin, and Resorcinol Tanning Agents and the

Properties of the Resulting Leathers. Ekoloji, 21(82), 17-25.

[173] Eaton, A. D., & Franson, M. A. (2005). Standard methods for the examination of water &

wastewater, 17th ed. American Public Health Association.

[174] ASTM D2983 – 09 Standard Test Method for Low-Temperature Viscosity of Lubricants

Measured by Brookfield Viscometer

[175] ASTM D5355 - 95(2012) Standard Test Method for Specific Gravity of Oils and Liquid

Fats

[176] ASTM E70 - 07 Standard Test Method for pH of Aqueous Solutions With the Glass

Electrode

[177] ASTM D2194 - 02(2012) Standard Test Method for Concentration of Formaldehyde

Solutions

[178] Smith, B. C. (2011). Fundamentals of Fourier transform infrared spectroscopy. CRC

press.

[179] Ullah, S., Bustam, M. A., Nadeem, M., Naz, M. Y., Tan, W. L., & Shariff, A. M. (2014).

Synthesis and Thermal Degradation Studies of Melamine Formaldehyde Resins. ; The

Scientific World Journal, 2014, 1-6.

[180] IUP 3 (2006) Sample preparation and conditioning, ISO 2419.

[181] IUP 6 (2002) Measurement of tensile strength and percentage elongation, ISO 3376.

[182] IUP 8 (2002) Measurement of tear load - Double edge tear, ISO 3377-2.

[183] IUP 9 (1976) Measurement of distension and strength of grain by the ball burst test, ISO

3379.

248

[184] IUC 19-2 (2008), Determination of formaldehyde content in leather Part 1: Quantification

by colorimetric analysis, ISO 17226-2.

[185] IUP 2 (2002), Sampling location, ISO 2418.

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