Chapter 4

LEATHER BONDING

Chapter 4

Partl Studies on Polymeric Solution Adhesives for Bonding Leather

The footwear manufacture involves joining of many intricate parts using adhesives‘. The

forces of attraction may be strong chemical bonds or the weaker forces known as Van der Waal’s

attraction 1-‘. Bonding may also results from mechanical interlocking or by penetration ofadhesive

molecules into the substrates by dilfiision‘.

Neoprene rubber, nitrile rubber, polyurethane rubber 5'“ and natural rubber based adhesives

are common in shoe industry 7. Disadvantage ofnitrile based adhesives is that , it is necessary

to activate the substrates at higher temperature (70-80 "C) to get better bonding strength.

In this work we developed three diflerent types of novel solution adhesives are proposed

to be tried for leather to leather bonding . The peel and shear strength of the adhesive joints are

proposed to be compared with joints made with commercial adhesives.

Experimental:

Materials used:

Commercial N01: Poly urethane based commercial adhesive supplied by CLRI Madras.

Commercial N02: Dentrite adhesive supplied by Superchem

Adhesive preparation:

I- PVC based: Suspension grade PVC was dissolved in either cyclohexanone or

tetrahydro furan. The solid content of the solution was l0 percentage.

2. CR based: Chloroprene rubber was compounded as per the formulation in Table

4. l. I. This compound was then put in a solvent (usually toluene) and kept for two

days. After that a mechanical stirring was given to make the solution uniform, the

total solid content was about 20 percentage.

3. NR based: Natural mbber was compounded as per the formulations in Table 4.1.1.

This was then dissolved in solvent and the adhesive was prepared explained above.

93

Table 4.1.1 Formulations ofleather adhesives. pi-.1

i

1

r

I

I

V

l5. _

I

I

I

I

I

|

A Ingredients JNR adhesive SBR sole l

1 ­

f"'":"" Z ‘it J" J “"—*"._‘:T“""'f:""'* " ' ‘_”*:""”1;T" o ' “|‘:"-" o of(:R adhesive i NR sole 1" MC sole

NRCR

ii sen1; NBR

PVC

ZnO

MgO

Stearic acid

Accinox 'l'Q

Clay

Silica

HAF

Aromatic oil

MBTS

TiO2

DNPT

PF resin

Wood rosin

DEG

DOP

Vulcafor F

SulphurTMTD

1

I

I ()0

2.0

1.5

20

20

——'777-—---v- _ '_,~-_ . ..l .5100 iI00 0ii i 1 00I

1

5 Z 4 44 ~ i2 21.01.0 1.0is

i45 40

‘ 2 ; 2. 1.5 1.5

20

l0

J 1'5 J 2.0

1.0i 1.0

>

1

' r

50

50

5

2

2

80

20

2

I0

2

1-5

5

1.5

1.5

0.5

I.‘Il

l

Commercial adhesive I: The polyurethane based adhesive chips supplied by CLRI

was dissolved in THF to get a 20 percentage solution. This was used as the commercial

adhesive in this study.

94

L

I. Upper Leather to Upper Leather bonding:

leather pieces ( hereafter menrmrmrg Q/'1<.'u!/zer means upper {cut/2t.'r) were cut into llilx Z5

mm size. lihese pieces were roughened using sand paper no.50 and wiped with MEK and dried.

These specimens were treated with the adhesives so that the pores, completely tilled and there

was a uniform layer of the adhesive formed. When the adhesive surface is dried another layer oi

adhesive was applied in the same manner. When the second adhesive film is dry to a point there

is still an aggressive tackiness but no tendency for the film to Iitt when tested with a finger. The

coated surface ofthe two strips were aligned face to face carefully, without entrapping air, in

such a way that the free ends of the strips lie in opposite direction for shear strength and lie in

the same direction for peel strength testing. The pieces were pressed together by applying a

pressure of around 10- I 2 kg/cm? The test specimens were conditioned for 48 hours. For peel

strength testing adhesive was applied over an area 2.5x2cm at one of the buffed surface of the

strips- For shear strength testing adhesive was applied over an area of 2.5x 4cm at one of the

bufled surface of each strip.

All the three types of adhesives prepared with two commercial adhesives were used for

bonding the adherends to determine the peel and lap shear strength. Adhesion strengths were

tested on a Zwick UTM model 1445 with a cross head speed of 50 mm/min. at room temperature

as per ASTM l876(89) ~ adhesive strength for two flexible adherends. For each result six

specimens were tested and the mean was taken.

The leather to leather joints made were kept immersed in water at room temperature for

24 hours. After that the specimens were taken out, dried and thier strengths were determined as

per ASTM D 1137 (90). Leather joints were kept in an air oven at 50°C for 24 hours. The

specimens were then taken outside, conditioned and strength were determined. The leather

pieces were tested after 30 minutes of joining in peel or lap shear form so that the quick stick ot

the adhesives were obtained. Flcxing was given to the leather joints on Ross flex instrument.

Number ofcycles to failure were noted. Leather in both peel and shear joints were tested for the

flex resistance.

95

\

Q

2. Bonding of different leather foot wear components:

Types ol'_joints tested;

I. Upper leather to sole leather

2. Upper leather to vulcanised natural rubber sole

3. Upper leather to vulcaniscd synthetic rubber(SBR) sole

4. Upper leather to microcellular (MC )sole

5 MC to vulcanised natural rubber sole

6, MC to vulcanised synthetic rubber sole.

7. Upper leather to plastic sole

8. Sole leather to plastic sole

Natural rubber (NR) sole, synthetic rubber (SBR) sole and micro cellular (MC) sole were

prepared in the laboratory as per the formulations in Table4. I .l. The compounds were prepared

on a two roll mill ( l 5.x 30 cm). The optimum cure time was determined on Goefertt elastograph

and they were vulcanised on a hydraulic press at l60"C for their optimum cure times. Vulcanised

soles were then conditioned for 24 hours and hardness ofthe soles were measured on a Zwick

durometer.

Leather pieces were cut into 150x25 mm size and vulcanised rubber soles were cut into

25x 25 mm size. The leather and rubber pieces were bonded as per IS 4663(68). Rubber and

leather pieces were abraded with sand paper no. 50 and wiped with MEK solvent and dried. Two

leather pieces were taken and in between these pieces the rubber piece was kept and bonded in

a sandwich model- The rubber piece was coated with the adhesive on both sides and jointed

with the leather pieces. Both peel and lap joints were prepared for strength measurement. For

joining MC and leather both the adherends were cut into l50x25mm size- Rubber and MC joints

and upper leather to plastic sole were also prepared as above. In all the ditferent types of joints

the adhesives prepared were used and strength were determined as above.

Optical mr'cr0sc0p:'c studies

Optical microscopic examination of the roughened and peeled off surfaces of upper leather,

sole leather, rubber sole and microcellular sole etc. with CR adhesive was examined. The

96

peeled otlsurfaces with commercial adhesive Dentrite were also studied by optical photographs.

Results and l)iscussion:

Figure 4. l. I shows ettect oftotal solid content on peel and lap shear strength ofleather to

leather joints. As the solid content increases peel strength increases, reaches a maximum and

then decreases. Lap shear strength also shows same trend in this figure. This may be due to

lower penetration of adhesives when solid content is very high.

-F.-......__ .,_____-_.___-_¢----—— i_a.-Q.’-..— .-- —-—-----_-o.a----——--he----I - - -->~—- -ii—--—-nu-r —---—--ii-------\--——— —sot‘ 1. —I— Shear N/cm2

Adhes on streng h

5 8 8 8 8 8 Es‘

0 *** " ’T’ * "i H it” 7; * 1-’ “Ti *' "*7 *'* " i I10 15 20 25 30 35 40 45Solid eontent.%

FIg.4.1.1 Effect of solid content on adhesion strength

Figure 4.1.2 shows the etlect of viscosity of adhesive to the peel and shear strength of

leather to leather joints. When the v iscosity increases joint strength both in peel and shear

increases to some extent and then decreases. However,when the viscosity is higher the penetration

of the adhesive solution is restricted, resulting in lower peel (series l)and shear strength (series 2).

97

Figure 4. i.3 shows the pecl strength ofditferenl adhesives used for bonding upper leatner

lo upper leather before and after soaking in water. Commercial adhesives show inferior properties

compared lo the adhesives prepared in laboratory.

-Q—"

eson s reng h

{-1

. i

AdhPeel strength,N/om

90

80

70

8

50

88

20

10

O

35

30

IOO’!B

.1U!

-AO

5

|

I

|.‘\U

|

I

4!I

if

T-.­

-q}.\

I\

-0-— Peel Nlcm

-a— shear N/cm2

i

I

I

i

!

.1

-4

O

i— —7———.--_—— _ ' ______ ___ ._.__ _ _ 1? ' ——7 F------'7?-—---~. »1000 2000 3000 4000 H100 6000

Viscosity,cp

Fig.4.1.2 Effect of viscosity on adhesion strength

I

-'.

-n_|

--4

mbefore

.8119!‘

...7_.1 2 3 comm. 1 comm.2Adhesives used

Fig.4.1.3 Effect of water soaking on peel strength ofleatherjoints

98

-_-_.- -1-u-w-1. i__

Figure 4 1.4 shows the shear strength of lcathcrjoints before and after soaking in water.

Shear strength of commercial adhesives are found to he much lower than adhesives prepared in

laboratory. In hoth peel and shear strength NR based adhesives show tower strength compared

to PVC and CR adhesives. This may be due to the higher polarity of PVC and CR than NR

which gives more adhesion strength.

S cm2QU=aa8'a%88%85=8

m before ;' .3 . anef0-P :|

reng h NI

‘I ,-bvl

8fST18

1 2 3 com.1 com. 2Adhesives used

Fig.-1.1.4 Effect of hot water on shear strength of leatherjoints.

25 " i — ' _' ‘mi,’ 1- i f20 tIbetore :_ 15 II-MUH

strength N/crn2

E5

P88

01

qi ‘0% t1 2 3 eomfl com.2Achesixes used

Flg.4.1.6 Effect of ageing on peel strength of leather joints

99

wlnlncrmal adhesives.

strength N/0m2

0­

ShearPee -strength N/cm2

Figure 4.I.5 shows the pccl etmngjth of dnflcrcnt adhunvus before and after abcmg

AdhLSl\/CS prcparcd in laboratory (an, iound '0 ba. bctlu IT} agung r,s|stanu. wmpurcd 10

Figure 4.1.6 shows the shear strpnglh OfdlflLl'LI1Iddht,blVCb bufon. and aitu" dgung Nauml

mbbcr solution based adhesive show lower fU§lSIdflCC COmp.1rCd chloroprcnc and PVC baud

58B-sQ

w _,______._______,_ ____h__ _ _ _ _,_ l_________ _ _____ _i ._______

2 3Acheswes used

Fig.4.1.6 Effect of agemg on shear strength of leather

1.?‘-;'.f_. _.' .t

-1»U1

_aQ

25 1% ‘Ah "T ‘ ‘ ” “.,_..{

1' ,..

!) '1" T'­..|.~ \­1-#:~5l'>

\ \‘,..J"p11,I .­'.~‘|. ._]].-,­

;_v.|.'s"":'Jl-‘ii

|i;.>'l L .

1 2 3Adheswes used

Flg.4.1.7 Quick peel strength of leather ;omts

__._._._l._-­L-f,

com oom2

I quick suck

com1 com2

adhesives. This may be due to the better ageing resistance of CR and PVC than NR solution

Commercial adhesives show lower ageing resistance compared to adhesive prepared in laboratory

so so » g __ _45 in

4° "ii H original

Shear s rang h N/cm2-~ to re to ozU1 O U1 O U't-l _{ - it; 4-14

s‘ I quick shear ii l4-I

|

Q-I

l

l

l

|

10¢‘

5“J

1 2 3 com.1 com2Adhesives used

Fig.4.1.8 Quick shear strength of leather joints

Figure 4.1.7 and 4.1.8 show the quick stick values of the difi'erent adhesives in peel and

shear joints respectively. The quick stick strength in both peel and shear test shows that the

adhesives prepared in laboratory are superior to commercial adhesive. The adhesives prepared

in laboratory gained the adhesive strength within 30 minutes of time.

Table 4. I .2 shows number of cycles to failure of adhesive joints were failed. The adhesive

prepared in laboratory are found to be more resistance to flexing - Flex resistance ofeommereial

adhesives are found to be poor compared to adhesives prepared in laboratory.

101

O

Table 4.1.2 Flex test results:

J Adhesives No. of cycles to failure

i

6» wee

l. l 1I . peel p 2856 ’; 1 shear Above l lakh 12 peel l508lI 1 shear l Above I lakh E.1 5 1%1 3 11 peel 1 16446 Z

H shear Above l lakh it1 Commercial I 1; peel 50 1. 6 shear A 200 \1 ll1 Commercial 2 5 peel 1 15046A ' shear Above 1 lakh

Table 4- l .3 shows the strength of different foot wear components which were jointed with

the adhesives prepared in the laboratory. lt may be observed that the adhesive prepared in

laboratory shows much superior bonding compared to commercial ones.»

Table 4.1.3 Strength of the joints of different leather foot wear componentsI. --i-~-~v-~ ~ ———-~~~.---~e--~ ~ V —-ii ~ Y V -e -~ , ———~—i- ~~ ~— — ————————~———-—— - -vIp . 101.461 1 1 2 3 A Comm.l C0mm.2'5 T '_i _‘ *il>'"" 5"‘ 5’ ”””*_?* ‘r "r"? 5 '5 1" '5‘ ‘*7 5"“ _; __—“' " " ‘11 ' i 1 " ! 5 1 li A1, csrve 1' peel shear peel shear “ peel shear . peell shearL peel lshear Aj .. .__._ . ....__ __ ___l . ___ _ . . _" I

Q I_J'\OIO

ll " 7”_ "V _' irl __"——"'i'__ _‘ 1 1' Vii ‘— " '7 ' V-WT‘ ' _ ‘ —— if? 7*l l. 1 ll.5 5. 59.5 Z 15.7 1 43.] 11.44 4.9 1 l.2 9 8.6 Q 9-8 ..- I

2. T1 5.8 24.l 12.7 7 47.0 3.0 A 8.4 2 A 8.8 A 6.8 E“ 29.4 in‘i A i Ii . 3F 3. 4.6 1 31.7 ll 8.6 A 22.9 1 3.5 ll 6.4 1 0.2 04 1 6.2 1' 24.6 E1 l ‘ 4 | ‘ :1 . ­1 ' I , ' | Iii 1 ‘ " ' E; ' 1 ‘ I‘ 1 '1. I p ‘ . 1' ' l. 4, a 16.412-4.9 13.3 l9_9 l.3 . 5.4 61 1.5 T 6.3 ll l().3 1; l9.5 1

5. 1 10.21 28.0 1 9.5 A 22-5 1 5.2 1 0.1 1 0.6 29 11 16-4 1I l 1 1 . 5 1 1 I A 1I. 1. =1 l Ii It 1 ‘1 '1 6 1 12-6 29.4 8.3 1 27.8 §10.6 . 13.7 1 0.5 1 6.1 1 11.71 114.2 1

A 7, 12.61 29.4 1 3.3 27.8 ? 10.6 § 18.7 0.5 6.1 . 11.7 1.-———~l-—— .. .. 1~ A e-- ~———.:~~~_:_——— . _,__-_-.a-L“; _- .-L-K __-__-_1+___._ _-_e_J _-~. ----444...;-_-_-T_ee___._—_— _

9°to

‘P’

.' -' “@­

4. .,,

Photograph 4. l .l Roughed upper leather surface before adhesive application.

l

l

l$7‘ - -.- - — -1' —- - ~—

Photograph 4.1.2 Peeled ofl‘ upper leather surface with laboratory adhesive

.. lPhotograph 4. l .3 Peeled off upper leather surface with commercialadhesive.

5')Q

1--_“:m_ \_. _ _ ._ . . ‘_.-6‘ I‘ ~4- _,.' . ""7-; - _1' ' .,‘- - '- .-"_-5-_. §_q=:._ _»::.|..__.,';-_v _ _.-_. - , 3 ," "' —' .a'?"'-‘-.*"- .‘ u- “.+_--~"'\­

» ,..*_'I“- --..?

.-1"? ~ {U;I 5*‘I-I '.

I .Q I-Q \'_ ' _:_ ,27*:‘

""1§r';wt’

JP kl"

__ _ ' ' I ..=-P." = -K"?-'1C . )~-b-'. f ~- I ;

V‘q * 0:?“_ ‘ri" .‘"" 1'.‘ .. - '_

. _‘Y \ = . "Ig-"‘¥.—‘»'. fkw’ 3

. -‘_ i ' __ ‘\ _\-'; __ -.-- ‘I .) '- IQ. \_'-‘* \ .1. - '- . |. T‘ ' :­‘ 0.; ­Q

I

5-. ; Pi­/.,' .. ' ' \_-'‘I .._< ‘J Q ‘T.5 . '- ' , In .-. ' "‘n -\ V‘.~r - .. ‘S':%‘~.9'|’ ‘ 1~‘ -*‘!o';‘.z "-_-I.‘ -.-.. .‘inf? _..

-'~ v

,.

_.- ~_'_ . ,- , _ J, » V1- w - . 0-» _-¢_ >' . ' " ‘c' 2' ‘­.. _ ' . -9'$1 ,_I‘ -Q 'f . ‘ R ­‘i 1' '1-1 ' ' .“-I ‘"- __ ,-<_....,q:. . I‘:If r. -|._J>_ q;'*>‘g:.;: "1 __~ ‘ " ‘.44 .

Fiim.

; |1%(,;[,<%_,-W1] ,¢1_1_4 Rougzhcd _§'()/Q lc2{1Tl1¢;?I' _<1|:'f’:1<r<;: hclmc :1(_H"|(2Si\/Q.‘ appli<:m.in

]')hQ{Ogr3ph 4 1 5' l7‘c;:<.:lc(i nl"l‘ -W/<L’L l0nll1<}"1" .~41,%|r'i‘:.":<.;%c with l;;1lm|'atm'f.? :1rih<:s' ­IV"

-\_w­

“\­

Photograph 4.1.6 Peelcd of!” $,,;@ leather sllrfacer with commercialadhesive.

i

|

I

4

I

I

I

Photograph 4.1.1 Roughed rubber surface before adhesive application

Photograph 4.1.8 Peeled off rubber surface with laboratory adhesive

Photograph 4.1.9 Peeled off rubber surface with commercial adhesive.

'32‘.--‘- - - _ , ‘I '- 4 .‘*>".\-»- - -T .. I1.:_-|.~,‘I|_‘l. -"‘:~'L,).\' U‘ , .‘ "~ 2" '. '

Photograph 4.1 .10Roughed M C surface before adhesive application.

Photograph 4.1.11Pee|ecl off M C surface with laboratory adhesive.

I-i1~‘§flE3*I'?5¥¥\ <7» “

Photograph 4.1.12. Peeled off M C surface with commercial adhesive

‘Y ‘ W ' 7* it‘ *' ' ' '_ T’ i C i’ ‘ ii‘ f ' ' i ' ' ‘ ‘ ‘ '* ""'iI .gt l. Upper leather to sole leather 1 5. MC to NR sole

2. Upper leather to NR sole Y” 6. MC to SBR sole *7

1* 3. Upper leather to SBR sole ;r 7. Upper leather to plastic sole i:

q 4. Upper leather to MC sole ~'iIL 717' 7 7'. _ __ _

Photograph 4. l .l shows the roughed upper leather surface and photographs 4- l .2and 4. 1.3

show the peeled ofi' surfaces with CR adhesive(laboratory) and commercial (Dentrite) adhesive

respectively.

Photograph 4.1.4 shows roughed sole leather surface. Photograph 4. l -5 and 4. l .6 show

peeled ofi" surfaces of sole leather with CR adhesive and commercial adhesive respectively.

Photo graph 4. 1.7 shows roughed rubber surface. Photograph 4- l .8 and 4- l .9 show peeled

off surfaces with CR adhesive and commercial adhesives respectively.

Photograph 4. l . l0 shows roughed surface of MC sole. Photograph 4. l . l l and 4. l . l 2 show

peeled off surfaces with CR adhesive and commercial adhesives respectively.

ln all the photographs the surfaces of CR adhesives and commercial adhesive are found to

be comparable.

Conclusions:

l. Natural rubber, chloroprene rubber and polyvinyl chloride based solution adhesives superior

to costly polyurethane based adhesives for bonding leather substrates.

2. The water resistance and ageing resistance of such adhesives are found to be superior compared

to the commercial adhesives.

3. Quick stick strength and flex resistance of these adhesives are also superior to commercial

adhesives.

l 03

References:

I. I-. Skeist. Hand bg0k_Qf Adhesives, second Edn, p 29, Van Nostrand Reinhold, New York

(1977).

2. R- K. Goel , R- K. Gupta, Industrial Adhesives and Gems First Edn. Small Business Pub

New Delhi,( I980).

3. Teppema, J. Manning, J-F, U.S. Patent 2379552 July 3, (1945).

4. D.D. Gerst, Adhesive age, 36, 13, p12 (I993).

5. R. Panda and H. Panda, Chem. weekly, 38, I7, p 137-144( I992).

6. T. Drozd and P. Penczek, Adhesion, 35, 4, p 30 (I991).

7. P. Cranley and O. G. Lay, Adhesive age, 37,6, p6 ( I994).

I 04

Part 2 Aqueous adhesives for bonding leather components

ln recent years concem for the environmental etlects of solvents is growing. The increasing

awareness ofthe impact of solvent emissions is leading to greater restrictions on solvent usagé.

Volatile organic solvent containing preparations such as adhesives and finishes are being

restricted nowadays Chlorinated solvents used as cleaners and propellants lead in depletion of

the ozone layer in the upper atmosphere which protect us from harmful UV radiations’ . Solvents

participate in photochemical reactions involving nitrogen oxides and sunlight to produce ozone

in the lower atmosphere which is harmful to biological processes and a major contribution to

smog. Two methods which may be used to avoid such pollution are to use solvent free adhesives

and to contain or destroy solvent vapours. Non solvent adhesives such as latex and hot melts are

used in footwear industry "‘.

l n this study, latex based adhesives for bonding leather components are proposed to be

developed . The peel and shear strength of the adhesive joints are proposed to be tested and the

resistance of the joints under different environments and shelf life of the adhesives are also to

be determined.

Experimental

NR ,VP and XNBR latices were compounded according to the formulations in Table

4.2.1. Leather pieces were bonded using these compounds and their peel and shear strengths

were determined as explained in part l of chapter 4.

Table 4.2.1 Formulations for latex adhesives , Pi-i1I. i_ _. — ____._ _ _1F;f*—-' __-._;--if, _._. - -'- 7 _;‘f_ fi;;:_;.* -- _.‘—"‘ __J_‘

It

j Ingredients ”NRlatex up VP latex j XNBR latex H

7 NR latex it 100 f ’M VP latex l00 lj XNBR latex 5; 100= KO}-l 7 0.l 0,1 0.l4E Ammo- caseinatey 5 5 5Starch i 2.5 2.5 2.5RF resin 7.5 , 7.5 I 7.5 j5 CMC 7 10 10 7 10, l. || |I ' 1l_.._ _t s fig _e_,_ _ :1 l._s__ H E4

ln order to compare the adhesion strength with a commercial latex based adhesive, joints

made with Fevicol were tested for peel and shear strength.

Results and Discussion

Figures 4.2.1 and 4.2-2 show the effect of ammonium caseinate in NR,VP and XNBR

latices for peel and shear strength of leather joints respectively. Ammonium caseinate acts as a

thickener in latices and increases the adhesion strength of the bonds initially, but after an optimum

amount there is a reduction in adhesion strength. When the amount of thickener increases

above the optimum level the inherent tackiness of latex molecules may get affected reducing

the bond strength .zse s » ~ll -0--N? l1 -l—VP ll- it VPBR \I ‘( I‘

strength N/cmE5 E5 8

l5 i l

Pee

0’~— » 10 2 4 e e 10 12Ammo.Caseinate,phr

Fig.4.2.1 Effect of ammo.caseinate on peel strength

*_i__.__ ___7 --____ _--—_ .-¢__ — ...-_ —-qqii..-_,i_.__.-.i_i_~_a-..,-..i__-ii.‘-m

100:1 ___,..£_-.._ -~'.-'­so l1 5 " VP' 1 / I -“:H~XN8R s

s rength N/cm2

O)O

1

it r s " ""*"*r “"‘""i"‘-e ~~--%_. i40 1 Q

Shear

» l20!rO

O ,_______.

l\!

A

Oi

OD

-5O

.4M

I

-- __ . _”---i_ --%i-___~---_-i__-\—_?~.~1--i~--—ii- ----v-_ __. .-..i...._--- .-._.. ..---.___-_.-vt wu--- ---—- -- -1 — -- -- -- ‘

Arnm0.caseinate_phrfig.4.2.2 EffectofAmm.caseInate on shear strength

Figures 4.2.3 and 4.2.4 show the effect ofcarboxy methyl cellulose in NR,VP and XNBR

latices on peel and shear strength respectively. CMC is found to increase the taekiness of latex

particles thereby enhancing the adhesion strength . As the amount OTCMC inereasee aboxe It)

phr there is an increase in the viscosity ofthe adhesive and lacks its spreadability

N/cm2

.­

10-0

rang h

IO-I

Shears

I

I6* /I#­- ’§ L” 4~" ;- 4 il JA­*__e__,_­

~ _ —— ~ —___.-—_-& ~~— ——-_ ———~_\~ ——_7——— i _ i'______ _ _ __

N/cmU1

nghM (.0

F9

+; ' , if ~o' *““##f§#‘r —+—NR —a—VP iI

5

-0-Ii

Pee s

1 L _.»_ men ;0 "Ni iiifii ‘Q —'—T—— M ‘ii K-7 i — — ' hi i — — M i—i——i_f* i ' "_— _"—'__'_i

O *r—‘

N

-ts

O’)

CD

6

F3

CMC content, phr

Fig.4.2.3 Effect og CMC on peel strength of leatherjoints

25 ~1 -~=~——i»~ e ~~ —— ~— “M ~ » h|i -0- NR ir —I— VP * t-A---XNBR

6‘. 8

\

/" 1'-/ 5'

. I“ ‘i-'..-H-F

..-I»

Q

4 __ H __1._.e j'_ 7; ~I=_5 ‘$1 iI,

i0 -1 t i *7?’ t "*****—w " —%O 2 4 6 8 10 12CMC conter|t,phr

F ig.4.2.4 Effect of CIVIC on shear strength

I07

Figures 4.2.5 and 4.2.6 show the peel and strengths of leather joints with the variation oi

resoreinol formaldehyde (RF l)resin content in the latices. When the RF resin content increases

peel and shear strength ofleatherjoints increase, reach a maximum and then decrease. Resin

increases adhesion strength up to an optimum level , but further increase of resin may increases

the modulus of the adhesive films resulting in stiflening of the adhesive joints thus reducing the

adhesion strength 4 . The same pattem is observed for all the three cases , NR latex based shows

highest adhesion strength followed by VP and XNBR.

40 _ s _ .____s__ s e.______ _ __.._s e -.._____---­l135 1!: \. 5

om

55

i .l l‘H __ .- ‘ii " ' ' tH ,.,.= -es" no e it

Peesengh,N/E5 Z; 8 8

| i, .__

F

//I _,/ —-0--— NRU‘r #-- —-I-—\/P5 A t XNBR

0 ‘*—’ _f—‘_——" '_';_l"" ' "“—'_"l ' i i‘ l'_*_’ “iii " F ‘i "" "'_ 7*’O 2 4 6 8 10 12RF1 resin, phr

Fig.4.2.5 Effect of RF1 resin on peel strength of leatherjoints

1

I

I

- l: /‘ "'———i0 I

-1}’ - . _. _____i__..--...----_ii..._--~ -_-.___i._._ - .--i--__._.. -- -Q -----___~-.----- —- —- — —— —|

Shear strength Nlcm2

Q e a so ~> - -~=

N, b­

b

O5

Q

6

5 ._._______

"" A---—""'_'.so ts: as 4

i is ”"'“ ’ T’ " in’ '—" Tim‘ '— ii ii 1'7‘ ""“‘ _'—‘”+—"_ _"” " '

RF resinphr

-0-l\R -n—VP -4- XNBR

Fig-4.2.6VItdlonofshea|'st|'engtl1vdthRF1 neslnoontent

108

The variation of cooked starch content in NR, VP, XNBR latices on peel and shear strength

is shown in figures 4.2.7 and 4.2.8 respectively. There is a slight reduction in bond strength as

the amount of starch is increased from 2.5 to l0phr as expected. ln leather joints starch causes

slight reduction in bond strength and water resistance 5­

N/cm

0­

reng h

Q-ll

§-9

-1

Pee sShear strength N/cm2

10

9

8

7

6

5

4

3

CD-\l\)

27

BlE3PO-I

19

....s\l

ii"

-»

13

fl

J

"lfl

_I

lli

J¢_

/.____~__H“ k ‘

—o—NR

—§—-VP

a XNBR

“__l

--.‘_'--­

W--\"x.

__,£

l

i

|

l

1

0 2 4 6 8 10 12Fig.4.2.7 Effect of starch on peel strength of leather joints

I .

|

2

l

.|

|

ll t—0—l\R

—I~—\/P

1 )Q\BR

15 L-_.____..___. ‘Mr...

7 — U‘-W **' l ' ——l_—‘_' l "ii 'T" _ "' f— "' l ll?!“ l *""

Starch, phr

——_.---- 7 TH - —._.i____ i _--.~-H?-_i@i_.-Qq------___~,,.__,.-_.__ii._-k-Q» Q --- .__,_

£

__-__ .

O 2 4 6 8 10 12Siarrhphr

F-19.428 Effed ofstamh on shear strength

109

l

l

\_._.-t. .-.-5. - -__ ­

I

Figures 4.2.9 and 4.2.10 show the peel and shear strength of leather joints before and after

soaking in water. lfrom this it is clear that NR latex based adhesive shows highest strength

compared to otherilatices. This may be due to the higher solid content of NR latex. XNBR latex

based adhesive shows better bonding strength compared to VP latex. However, there is some

reduction in adhesive strength for all the adhesives due to the presence of water

40 i is c- » s- r M? r

_-J

renghN/emor 6 E3 8 El 8 8

s EtbeioreI >Ii’ ‘

---_­

letterI-0-I ‘

Pee s

__fi_.._ _...__,i .._tBR VP )¢~BRLatices used

Fig.4.?_9 Effect of water soaking on peel strength

250 — ~ —

N/cm2

§

t mbetorelatter

>

5%

ngh

*"' 1 I|

{i

shear s re

§

504 in@t_ _T*.~ _,__ »A

XNBRNR Laticdspused

FIg.4.2.10 Effect of water soaking on shear strength ofleather joints

110

Figures 4.2.1 I and 4.2.12 show the peel and shear strength ofjoints before and alter soaking

in hot water at 80"C. ln the cases of VP and XN BR latices slight crosslinking may occur which

may be the reason for increase in adhesion strength. But in NR latex slight decrease in strength

is observed which may be due to naturally occurring easily decomposable materials present in

NR latex.

40 sag» - E »~ ssss -~

Peesrenghhl/cmas at 8 8

_“ "_aM"_"_aM-m__J

W zabefona__‘ 25 pi Iafler at4-0 ‘Q51 |'

_._—_ —

5 IO s——— — —- -%—-~ s -—1NR VP XNBR

Latices used

F ig.4.2.1 1 Effect of hot water on peel strength

250,,“ J» -~s ~ -- ­

gth N/cm2

1% §

l ll, u before ILy I after ;

Shear stren

é‘

___ _,_ i.‘ii.50 ‘ ;i

4l r ,BR VP XNBR

Laioes used

Flg.4.2.12 Effect of hot water on shear strength

ll]

Figures 4.2. l3 and 4.2.14 show the peel and shear strength of leather joints before and

alter ageing in air oven at 50 "C. Leather pieces joined with NR latex based adhesive show

more decrease in strength compared to other two latices. This may be due to the higher degradation

of NR latex­

4o»~~~ - ~ -—- — 1­35 II III

Peel strength N/cm

0» 6 a 8 2% 8

latter » e — I.>

I0 —.-— P-—iNR VP XNBRLatices used

Fig.4.2.13 Effect of ageing on peel strength

250 e - » » ---- W» as --e see»-I

?N/cm2

flD6lOf8Q Iafter

eng h

8

I

\—-0-0 I

Shear s

8 8

-iw i- —i—@ __ --_---..-.­NR VP XNBRLatices used

F ig.4.2.14 Effect of ageing on shear strength

I12

The quick peel and shear strength of latex based adhesives are shown in figures 4.2. l5 and

4.2.16. All the three latices attain almost full joint strength within 30 minutes.

49 _ " at ewe em; '7i‘ _35 originall‘I -quick peel

Pee st N/cme at 8 8 8

4.4 - l

rang h

?- ‘Q

51 L .__.-_..r-___~i_ _i--1.__-__ .___NR VP XNBRLatices used

Fig.4.2.15 Quick peel strength of leatherjoints

250 sci has-as-so ~s— s

N/cm2

§

.__._..- .___._l

l 5: original" I quick peelQi

streng h

8 8

1‘I I4I l

l

t ,l

1

She

8

*6 INR VP XNBR

Latices used

Fig.4.2.16 Quick shear strength of leatherjoints

The peel and shear strength of latices stored for one to four weeks are shown in figure

4.2.17 and 4.2, I 8. NR latex shows slightly more reduction in peel and shear strength compared

H3

to VP and XNBR latices. This may be due to the comparatively low storage stability of NR

latex. So for better storage stability synthetic latices may be preferred to natural latex

35 ____30+ l

8 8+_i$~_4_l.__

g h,N/cm

Q-'4

en-LU1

OI‘

our _

QGST

3

_L5fi._¥_*

-+-—NR

-—I—\/P

-to ems._____“ atC

|

P

sal

0 '1'_~— —_ ill - I k -1’ " H 1"’ ‘W “Til ’: F" ' _"

' it '1 = e ' V“”“I

‘l

R Y

atO 1 2 3 4 5 6Storage time meek

Fig.4.2.17 Effect of storage of latices on peel strength

250 .];t__,_ _ _

n, N/cm2

“8’

eng-A -58 8

¢—?;'~;— ; _'T

44'

C-I

GSFST

¢ .-‘_ ‘_

-0-—NR

-l—VP-:- XNBR

Sh

w I e ' * ’-i'*"—' ~ __.___ _ __

0 U _ as s s 1

1

l4 _._ Il

W. I0 1 2F ig.4.2.18 Efiect of storage of latices on shear strength

Table 4.2.2 shows the peel and shear strength of different leather components jointed

using the latex based adhesives. The strength ofjoints made of NR latex based adhesives are

found to be superior compared to other two latices- This may be due to the highest solid

content of centrifuged latex.

_, ___.. |Storage time, weeks

1 14

3 4 5 6

Table 4.2.2 adhesion strength of different components by latex adhesives

Adhesives K Nlllatex it VP latex 1 XNBR latex 11 1 peel shear 2 peel T shear 1 peel 6 shear 1

_ _ _,_,_,_ __ ____]_i

N/cm 1 N/cm: N/cm N/cm: . N/cm N/em: .

1|

| 1Upper leather to

sole leather

Upper leather to

NR sole

Upper leather to

SBR sole

Upper leather to

Me sole

Me to NR sole

Me to SBR sole

Upper leather to

plastic sole

Table 4.2.3 shows the results in comparison with the commercial latex based adhesive­

1

l.

1

3.4

3.5

9.4

4.3

6.4

10.2 1

3.5 11

1 J 1

. _fi_I

I

|

03.2 Ei

28.41K

28.5

24.3 1

16.9 p10.9 1

25.6

1 44.4

. 20.3

23-0

1 13.8. 12.2

11.1

Z 23.2

1

i

Table 4.2.3 Comparison of latex adhesives

10.9

1* 8.91

9.0

10.12 8.3

8.1

8.3

-- ---_--2 __‘

70.7 .

. 25

17.7 J

1 10.9 ‘1 10.9 1

11.9

A 20.3

Pevicol. The peel and shear strength of upper leather to upper leather is shown here­

|_LV_ ._...__

—~* —————- — - —- -- - -- ‘ &— - - -— ~-- - — 7 — -V 2 7 ' —“i‘7:lYI ~­

1

Latex adhesives i Peel strength, N/cm p Shcarstrength,N/em: 1

_ .‘_

NR

VP

1 XNBR4 Fevicol

— —~*--L2 ----~ as 1 as A -9 — 9-—~-—** is--1 -—- 9- *~-~- 4I

|

1

1

1

30.5

12.2

20

12.1

193.5

61.5

90.8

120.3 ‘

115

Conclusions

l. latices of NR, VP and XNBR can be used to prepare adhesives for bonding leather

components­

2. Ammonium cascinate and CMC can be used as modifiers to increase the adhesion strength.

3. Starch can be used as a filler in latex based adhesives without much deterioration in

properties.

4- An optimum level of resorcinol formaldehyde resin can increase bond strength.

5. Compared to synthetic latices natural rubber latex shows marginally lower ageing resistance.

6. NR latex based adhesive for leather shows superior bond strength compared to commercial

latex based adhesive-Fevicol.

References

l. L.H. Lee (ed), Adhesive Chemistry Development and Trends, p 693, Plenum Press, New

York (I984).

2. J. Carol, Rubber World, p I8, Sept I993.

3. K. Palanivelu, Leathers, 46, July (1997)­

4. M. Mitoh, lnt. Polymn. Sci. Techno], l4 (6), T/89 (I987).

5. D. C. Blackley, Polymer Latices, 2 nd cdn, Vol.1, p392, (I997).

I16

Part 3 Studies on novel low cost adhesive system for bonding different components in

leather products.

ln leather product industry many dissimilar adhcrcnds are jointed using ditierent types

of adhesives. The joining mechanisms relate to include the complex chemistry of the adherend

surfaces‘ ­

Polyurethane based adhesives are widely used in the leather industry. These adhesives

have disadvantages like low tack, shorter pot life and limited durability’ ln foot wear

manufacture different adherends like upper leather, sole leather, rubber sole, plastic sole,

micro cellular sole s etc- are bonded using adhesives’ . The adhesive used should be compatible

with all the adherends used and must comprise of low cost and easily available components‘

ln this part of the study, adhesives from blends of thermoplastic elastomer solutions

are proposed to be developed and evaluated for bonding leather.

Experimental

Two types of adhesives based on thermoplastic elastomers from rubber/plastic blends

were prepared and i-vestigated for leather to leather bonding- The ellieiency ofsueh adhesives

was compared with those of commercial adhesives. Polyureathane based (Commercial l)

and dentrite (Commercial 2).

This part of the study also being patented The auther requests to be excused for not

giving the details ofthe materials and formulations.

Leather components were jointed with the adhesives prepared and also with the

commercial adhesive(l)entrite). The peel and shear strengths ofthe joints were detennmed

as per procedures explained in part l ofthis chapter.

H7

Results and discussion

Figure 4.3.! shows the variation of peel and shear strength of leather joints when the

viscosity of the adhesive blend type l changes. This shows that on decreasing the viscosity the

adhesion strength decreases. On reducing the viscosity the solvent content increases and solid

content decreases thus adhesion strength reduces. Similar behaviour is observed for blend 2

200 u- --1»--__--» ----i- - -~ - ----------q‘.

I1 V-0- peel Nlcm

éé

4- shear Nlcm2 ;140 E lto-I 1 _ ——I'e ' e—.-» ..; l

s reng h.-LMo

F

80 1 1

Jo'nt

so 0

see

O

9

‘F

L

_' —;__'i -— — i'*' f’ ‘ "*Y'"’ ' — "'—_' ' * ' '—0 500 1000 1 500 2000

Viseosity,cpFig.4.3.1 Effect of viscosity on joint strength of ble nd1

adhesive

w __.--.._.__._..-.....__i.-.- ..._. _ __.__. ___ __ _ ______,__,._,___________________ \___________ ,____jl80 I’ ____.s..._..___.--—-———"* 0 i ' A A ha. '

1,‘, _;

70 ; t

strength

8 8

__, 40 .i ——o—peel NIGHT!. -1-» shear N/cm2 f

Jon

8

20 ~j ­101 -sassy ~~~ 1» ~~~ ea» EQ a ee___________ _ _____,__________________10 1000 2000 3000 4000 5-000 6000

v|scosity_cp

Fig.4.3.2 Viscosity of blend2 adhesive onjointstrength

I18

(figure 4.3.2) also. Higher viscosity if preferred for better strength but when viscosity increases

more than an optimum level the spreadability of the adhesive over the adherend decreases. So

we maintain a viscosity of around l000cp.

Figure 4.3.3 shows the effect of peel strength of leather joints when the amount of

thermoplastic content varied. When thermoplastic content is zero strength were very low in

39 ~_-___. ___-_-_. __ _ » .25 ‘J —o—blend1 L_l -——I— blend2 5a i;

ngnN/cma 8

~ l1 if0-I lli

1

I

'1l

-0-I3 ‘

Pee sre-5O

5-! _jr#-=4* I 'on —+—J l0 ‘1__: 1 * t*’* *"" ""'“"T’ “ _' A 7 —_’ *’ i”“_’ i lO 20 40 60 80 100

"thermoplastic c0ntent,phr

Fig.4.3.3 Effect of thermoplastic content on peelstrength of leatherjoints

both types blends. But when TP content increases peel strength increases as modulus of the

adhesive film increases 5 Thermoplastic alone is used then also peel strength is lower. This

may be due to the unique property ofthemoplastic elastomers. ln blend 2 the strength of adhesive

film is low so that adhesion strength also found to be lower. Similar behaviour was obtained as

in the case ofshear strength also in figure 4.3-4.

119

Figures 4.3.6 and 4.3.5 show the effect of tackificr resin in peel and shear strength of

leather adhesives based on thermoplastic elastomer solutions respectively. Peel strength of the

joints decreases as resin content increases but as resin content increases shear strength (fig.4.3.'5i)

r strength N/cm2

Q

SheaShear strength N/cm2

4~

200T180 -1

160 --0-blend1——I—b|8fld2

é

120 T,

§

Q)‘;60¢

waif

0 —-- "1 "-'* *-1* ~"— 1” r’ i0 20 40 60 80 100 120Thermoplastic content,phr

Fig.4.3.4 Effect of thermoplastic content on shearstrength

2 T-——'~-ii__-»<-ii--ea---,i__h.__-—-%i_i.... d Q--»i__~-H —- -ii—--u——i--vi-H ———i--\-w-ii —-- ­

§2'§

5U:

0

/ -4--blend1a ——-I— blend2'11.»//as0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9

PF resin ,phrFig.4.3.5 Effect of PF resin on shear strength of leather

joints

I20

~-~u

___._-.__,--_ _._. _.

It\

E

(

!|

I

!

I

1

%" ’—’ K ‘ %—— *""*~~—r~~ ' -;-—'-1 ~ :‘ —- -L, e - ‘ ‘*7*'" :— -- *

increases reaches a maximum and then decreases in both types of adhesives.Thi shows that

resin present cannot increase the inherent strength of thermoplastic elastomers. As solid content

increases peel strength does not increases as in the case of shear strength‘ . So shear strength

initially increases when the resin is added to the adhesive.

Figures 4.3.7 and 4.3.8 show the efi°ect of a plastisicer in the thennoplastic elastomer

based adhesives on peel and shear strength of leather joints respectively. As the amount of

20 ~ e e ~-~ _18%;15% -#r~bbnd1 r

--I--UGIQ

Pmas hmvur-5 -L -5O N -In O5 Q O N -L

-5 -T44¥4_T4 \-’—- L 4

r

|

,.

1 ee ‘

rengt

“Lr —~_sQ‘. ‘ r1 "efi__ ,_T ____‘.+’

I -7 _—'7:—'1"“‘ 7 *_'__——lW ‘ " "f"'_'_ — '_ i ”"" 1|12 1.4 1.6 1.8 2PFres‘rtphr

Frg.4.3.6 Effect of PF resin on peel strength

3 s__.___-_._s___e_m _“_ we aa_-;i__t,,tt i_ it itII l

Pee nghNlcmM 0-! A U1 O‘)

8T8

{Ii

Q-Q . -4- b|end1 7r -u— b|end2 "i1-t“ A0 -»~----~---~-~-.--r--M»H ~-as as-as h-__.__,.___.._____~_-_;0 0.5 1 DOP‘ phr‘l.5 2 2.5Fig_4.3.7 Effect of DOP on peel strength of Ieatherjoints

plastisicer increases peel and shear strength of both the blends decreases. Plastisicers are used to

flexibilise the adhesive bonds but it reduces the adhesion strength of the joints ". This may be

due the more cohesive nature of the adhesive while plastisicer content increases.

35

30%

Ow‘O 05

Shear strength N/cm26 6 8 E3

51

v

44L}___A_|___.—L~

it

\

200

HSFBI1

IQ!‘

II!!!

0-Q

JO

20

0

I I ‘ 1I .._.-\¢ t ' t- : _ ':'~"=Z""~£@‘-*&" M'-.-I -' " . V - "'?"' . . = " P‘ ___ _ ll? . _~~- ;_;__w __ H I- “ ' 1 ""‘ |

—+—Uend1

—n—Uerd2

l .LI

‘i

"* "a 1 “ 1- ”~ r—*:‘ ~ a‘ *a 1 *—— :- i_"—*" ‘Mr

- 1 Mm 1.5H943-.8ElfectofDCPonsheastmngth

18° 1160$

K 14015 120 i

100 l,

ao60+ |f , , 149 J

:-'"'-"1-~+n I‘ %i 3E J P96*b8‘f0I'8'i Ipeel after

5* gshearbefore I. ; r I gsnear afterW .|\ ‘I 1r ~ 1V I!‘I 1 ‘ 'I I‘

2 2.5

btencfl bIend2 commAdhesives used

F ig.4.3.9 joint strength variation after soaking in water

122

Figure 4.3.9 shows the peel and shear strength of leather joints before and after soaking in

water. Strength of commercial adhesive(2) is also shown in the figure for comparison. Adhesives

based on lh6fl‘l’l0pl2lSiiC elastomers are found to display much improved water resistance.

Figure 4.3. l0 shows the effect of peel and shear strength of leather joints before and afler

soaking in hot water. This figure also shows the superior water resistance of the thermoplastic

elastomer based ashesives to commercial adhesive(2) ones.

Figure 4.3. ll shows the ageing behaviour of the adhesives. Both types of thermoplastic

elastomer based adhesives show better ageing resistance than commercial adhesive(2). Here1eo ii140 , ; IP9?] alter inT 4 i Qsheabeiore 5J ' I it [Jshear atter l0-I , ‘ '80-; 1! T

Joln strength

é E:

60* - 1 E40"?» 5 1 1 5l20 ._ . l l

O _ H, V _ _ _ t . J.-. .4 W; , __ A _ I ­l l‘btend1 btend2 Comm.Adhesives used

Fig.4.3.10 Effect of hot water on joint strength of leatherbonds

200 s - ~ .._j180 ii 1160 upeel before ll ll ' 1* Ll5. ‘ i; E1 shear before 1T, . gshear aft ,~ 100 in i l F" 6' l1

ngth

F3O

soil . A a 1

Join ere

so a ' I40 11 I A iE I l20 -l t 11 J-0 -- _ lblenolend1 d2 C0mm_

Adhesives used

Fig.4.3.11 Effect of ageing on joint strength123

also the thermal and ageing resistance of the thermoplastic adhesives are evident.

Figure 4.3.12 shows the quick stick resistance of the adhesives. In this case we can see

that thermoplastic elastomer based adhesives attain 80 % of their original strength within 30

minutes of bonding. Commercial adhesive(2) have only lower strength compared to the

thermoplastic elastomer based adhesives. Thermoplastic elastomer based adhesives are found

to be quick drying and attain the ultimate strength quicldy. So the production rate with this type

adhesives can be higher.

1 I

180+‘160% r‘ ' ~ ii­140 L 5 it "°'i9i"°' ii g \ ‘Z Iqlickped ‘E

ii Ii Umgina ;i,, , l “ ljquick shear 1!__ ‘i \ ‘I

trength

QssssééiJon

\ t l‘ r‘I ‘ l!: i‘ 1 ll ' I~ it\ v- ! ..

lI I '' I1 rl 1 ‘ ‘blend1 blend2 Comm.

Adhesives used

Fig. 4.3. 12 Quick stick strength of leatherjointx

Figure 4.3.13 shows the effect of storage on peel strength of leather joint with

thermoplastic elastomer based adhesives. When these adhesive are stored adhesion strength is

found to be increasing. This may be due the slight increase in solid content due the evaporation

of solvents. From this figure it is evident that on storage the strength of the adhesives does not

get dreduced as so they have enough storage stability. Figure 4.3.14 shows the effect of shear

strength on storage of the adhesives.

124

rang h,N/cm2

Q‘

Q0

Shears

25r

Pea s rength N/om-.|>O

Q-I

I

5

r151‘?

___|g ~—-Ione ~ téu-—---'*

‘ ____________, , ‘_ _ ___‘_ - ———.. —~ Q‘

-0- bIend1-u— blend2

0 *"“ 1 _ ’i"— 1 * '—1 ‘ W*;;*""' i ‘:3 ‘ ‘ I‘ _;fl'0 1 2 3 4 5Weeks of storage

Fig.43.13 Effect of storage on peel strength

200 e» (1 »180

....x

U’)Q

....\-hrCD

._aPOQ

-AQQ

80

60

tr

J

_ 4- ‘_—_-4-‘-;—;4~_

t

|

|

i

|

.

- -+

-4~

'\

.!

1

—-0- blend1

-—I—~ blend2

F" __ . to ~<-~~»~ 0

0 1 2" — ‘ i _ MI _ _ 7 *fi.__ '" ’A’*__1 "V '71‘ i

Weeks of storage

Fig.4.3.14 Variation on shear strength on storage ofadhesives

3 4 5 6

Table 4.3.1 shows the number of flex cycics to failure of the adhesive joints The adhcswcs

based on thcmtoplastic elastomcr solutions withstand much larger number of cycles than

oommcrcial adhesive.

I25

Table 4.3.1 Flex cycles after leather joints failed~~— -—_i W f_i' __ _- ——— ii _ _ _, I I H _ _ ____ __ ,___,, __ _i~ --V-_ -- '7 V V . — V 7 — '--— ——— ' '

N/cm N/cmAdhesive joint '5 Adhesive type if Peel strength, Shear strength,

I

Blend I

Blend 2

Y Comm- I

.___ ._+_.4_4_4_‘;r

Leather to leather 2I

Comm.2Blend I

2 Blend 2" I Comm.l ‘Leather to plastic A,

Comm.2 7

I6464

53656

200

20646

10246

43264

150

IO489

2 _.-T-__;..--_. , - . .-_Ts.._T.._.-.__.._._.­Above I lakh

Above I lakh

I600

83456

Above l lakh

Above I lakh

I 500

64346

I

Table 4.3.2 shows the peel and shear strength of different leather components jointed

using these adhesive solutions. These are the main components used in leather products. In all

the types of adhesives thermoplastic elastomer based adhesives show better adhesion for bonding

applications in leather product industry.

Table 4.3.2 Adhesive strength of different foot wear components

._. _.___ _ . _ ______.__|

2 2 r "fi;*::lr"""** r r "IiI Blendl 1‘ Blend 2 C0|nm.2 2“Adhesivet Peel . Shear I Peelp I N/cm N/em N/cm

bl

I? joint i . I I;; Shear L Peel5 Nkm L Nkm

H

Shear

N/cm

‘r’-—"-'—'"—'-'—"—— — e"---~ - B I B ' _rI | 'IA =22 I 83I21 asi

I. I8 51 .I I5 L 61 .A I 20 i 42E L ‘A

\-OO¢\lO\U'1-F>~UJl\J-~

30

30

32

28

2 I

29

I 23 39 2525é; A I4 35 ;E; 20 3 64 47Ii. . " .. ..1. ..

3O0

an

.128!6| Q62.I 92 3I 48 t=I492A435‘ 8| II! . . . ..

l0

20

I2

2]

I4

23

22

IO

ll

.___ __ __i___ __._t ______.i..__.__--—-i--V--V-77 —'i'—-,-v ~ V - i ­

30

43

4|33

50

30

3l

Z8

32i_i__________i____ _ Hriii ._i__ ____ __i_____ ___ ll‘ __ ____ _ _ __ _i__; L

I26

l -Upper leather to upper lather; 2- Upper leather to sole leather; 3- upper leather to NR sole;

4- Upper leather to SBR sole; 5 -Upper leather to M/C sole; 6 -WC.‘ to NR sole; 7 »M/(.' to SBR

sole; 8 -Upper leather to plastic sole," 9- Sole leather to plastic sole.

Table 4.3.3 shows the peel and shear strength of upper leather to plastic soles jointed

using the adhesives before and after exposed to different environments.

Table 4.3.3 adhesion strength retention of leather to plastic soles. Peel (N/cm)and

If W’ a S S. . l T :7 ‘ L_ WQVT 73 B!¢"<!1_ s_ Blend? J Comte-13 3 t_

i Peel i Shear ll Peel Shear Peel n Shear i"

Shear (N/cm!) strength.I i; i L S; l lJY—— -- *;_.l :33.” ~ -. - _ a- ~34 ‘Li _: if3 r 3' it 3' "3"3 Normal ll l4 1: 35 l‘ 25 ii 43 l0 1: 28 lf, Water l l ‘ i1-_ —-- ~ —— —- _ - ­

soaking ‘ll 4' 35 23 l 40 , 7 t 18 3P‘ Hot water 5; E , lllg r t ,A soaking V 5 ~ 32 i 9 it 4l 3 t 9 ll- I , ­Ageing 39 J 36 10 1 42 l 5 i 20' ‘ti 2 l. I~ t| - I

l Quickstic 11 T" 33 1 23 ti 40 4 i I8 it..__ _s i___ e ' ‘ sConclusions

I. Thermoplastic elastomer solutions can be used as eflicient adhesives in leather product

industry.

2. Themioplastic elastomer based adhesives show much superior bonding compared to

commercial adhesives.

3. Thermoplastic elastomcr adhesive solutions show better resistance to different environment

oompared to commercial adhesives.

4. The shelf life of the thennoplastic elastomcr based adhesives ure found to be vet}-' good

I27

References

l.K. Palanivelu, Leathers, p46, July I997.

2.D. Briggs, Hand Book of Adhesion, D. E. Packham (ed), Longrnan Group, Ltd., p461,

U. K (I992).

3. KJ- Kedlaya, Leaxhers, ll, no.8, p70, (1995).

4. H. Pagel and E. R- Luchnm Adhesive Age, 34, (Oct 1981).

5. Leathers, I2, no.4, p49, (I996).

6. Lealhers, I3, no.6, p 56, (1997).

7. N. R. Legge and H. E. Schroedr, Thermoplastic Elastome1"s- A Comprehensive

Review, Hanser Publicaiions, New York (I987).

8. L. F. Ramos De Valle and R. R. Ramirez, Rubb. Chem. & Teehnol, 55, 1328 (1982).

9. D. W. Aubrey and M. Sl'lCfl'lff, J. Polym. Sci, Chem. Ed, l8, p 2597 (1980).

10. I. Sl-;eist(Ed) , Hand Book of Adhesives, 2"’ odn, Van Nostrand Reinhold Co. New

York, ( I977).

l27A