EFFECT OF FIBRE SURFACE TREATMENT ON KENAF...

EFFECT OF FIBRE SURFACE TREATMENT ON

KENAF FILLED RECYCLED POLYPROPYLENE

COMPOSITES

MUHAMMAD REMANUL ISLAM

Thesis submitted for the fulfillment of the requirements

for the award of the degree of

Master of Engineering (Chemical)

Faculty of Chemical and Natural Resources Engineering

UNIVERSITI MALAYSIA PAHANG

JUNE 2012

vii

ABSTRACT

Lignocelluloses based natural fibre is being used as an alternative to traditional glass

and carbon fibre in the composite materials due to its low density and higher specific

properties. Furthermore, these fibres are available at a very low cost. Current work is

focused on kenaf fibre based reinforced recycled polypropylene composites. In this

project, initially the raw kenaf fibre was grinded to a small size (2 to 5 mm) and then

mixed with recycled polypropylene (RPP) followed by extrusion through a twin screw

extruder. Fibre loading in the composite was 10, 20, 30 40 and 50% by weight. After

that test specimens for tensile, flexural and impact testing were prepared through an

injection moulding machine. Melt flow indexer was used to evaluate the flow property

of the extruded materials. To improve the interfacial property between fibre and matrix

maleic anhydride grafted polypropylene (MAPP) was used as a coupling agent with

ratio of 10:1. Mechanical tests showed that significant improvement achieved due to

coupling agent. Fibre surface modifications for better adhesion between fibre and

matrix were carried out by three ways including alkali, ultrasound and laccase enzyme

treatment. Treated fibre was then blended with recycled polypropylene with 40% fibre

loading in the presence of MAPP, as 40% loading found the optimum regarding tensile

performances with untreated fibre based composites. For alkali treatment, both

concentration of the solution and soaking time were considered as treatment variables

for the fibre. Mechanical tests were carried out to evaluate the optimum treatment

condition for the best strength. For ultrasound, normal water was used as media for the

treatment. Both temperature and sonication power was considered as treatment

variables. Mechanical tests were carried out to evaluate the best strength at optimum

condition of fibre treatment. Enzymatic treatment was carried out for an alternative way

of fibre treatment. The composites strength was increased by 18% for fibre loading

whereas coupling agent improves it by 37%. Ultrasound and alkali treatment of fibre

improved the tensile strength of the composites almost by 57%. Weathering and water

uptake were carried out for the composites. After that mechanical tests were performed

to evaluate the properties of the composites. Thermal test like thermogravimetric

analysis (TGA) was carried out to evaluate the thermal stability of the composites. It

was found that, RPP degrade at one stage while composites degrade at two stages.

Activation energies of the composites were calculated from the TGA analysis.

Crystallinity and melting point were detected through differential scanning calorimetry

(DSC) analysis. Incorporation of fibre increased the crystallinity of the polymer matrix.

Structural morphology was carried out of the fractured samples to evaluate the bonding

interface between fibre and matrix. Improved adhesion between fibre and matrix was

found for the case of treated fibre based composites in the presence of MAPP. Fourier

transform of infrared radiation (FTIR) spectroscopy was used to find out any structural

change due to the treatment of the fibre and analysis found that treatment of fibre able

to remove the non-cellulosic compound to a varying extent depending on treatment

parameters. Response surface method (RSM) was used to optimize process parameters

and one of the best set of treatment conditions was 99.96% sonication power at 94.46 oC

to achieve 28.86 MPa of TS.

viii

ABSTRAK

Lignocelluloses berasaskan serat semula jadi yang digunakan sebagai alternatif kepada

kaca tradisional dan serat karbon dalam bahan komposit kerana ketumpatan yang

rendah dan sifat-sifat tertentu yang lebih tinggi. Selain itu, gentian ini didapati kos dia

adalah yang sangat rendah. Kerja semasa memberi tumpuan ke atas gentian kenaf

berasaskan komposit polipropilena kitar semula bertetulang. Dalam projek ini, pada

mulanya serat kenaf mentah dikisar pada saiz kecil (2-5 mm) dan kemudian

dicampurkan dengan polipropilena kitar semula (RPP) yang diikuti oleh penyemperitan

melalui penyemperit skru kembar. Muatan Serat dalam rencam adalah 10, 20, 30, 40

dan 50% mengikut berat. Selepas itu spesimen untuk ujian tegangan, lenturan dan kesan

telah disediakan melalui sebuah mesin pengacuan suntikan. Indexer mencairkan aliran

telah digunakan untuk menilai harta aliran bahan tersemperit. Untuk memperbaiki harta

antara muka di antara gentian dan matriks acetic maleic yang dicantumkan

polipropilena (MAPP) telah digunakan sebagai agen gandingan dengan nisbah

10:1. Ujian mekanikal menunjukkan bahawa peningkatan yang ketara dicapai kerana

agen gandingan. Pengubahsuaian permukaan gentian untuk lekatan yang lebih bail

antara gentian dan matriks telah dijalankan oleh tiga cara termasuk ultrasound, alkali

dan laccase rawatanenzim. Serat dirawat kemudian dicampur dengan polipropilena kitar

semula dengan muatan gentian 40% dalam kehadiran MAPP, sebagai beban 40%

mendapati prestasi tegangan optimum berhubung dengan komposit serat tidak dirawat

berasaskan. Untuk rawatan alkali, kedua-dua kepekatan larutan dan masa rendaman

dianggap sebagai pembolehubah rawatan bagi gentian. Ujian mekanikal yang telah

dijalankan untuk menilai keadaan rawatan optimum untuk menghasilkan kekuatan

terbaik. Ultrasound, air biasa telah digunakan sebagai media untuk rawatan. Kedua-dua

suhu dan kuasa sonication dianggap sebagai pembolehubah rawatan. Ujian mekanikal

telah dijalankan untuk menilai kekuatan yang terbaik pada keadaan optimum rawatan

gentian. Rawatan enzim telah dijalankan untuk cara alternatif rawatan

gentian. Kekuatan komposit telah meningkat sebanyak 18% untuk muatan serat

manakala gandingan ejen meningkatkan sebanyak 37%. Ultrasound dan rawatan alkali

serat meningkat kekuatan hampir 57%. Luluhawa dan pengambilan air telah dijalankan

bagi komposit. Selepas itu ujian mekanikal telah dijalankan untuk menilai sifat-sifat

komposit. Ujian terma seperti Termogravimetri analisis (TGA) telah dijalankan untuk

menilai kestabilan terma komposit. Ia telah didapati bahawa, RPP merendahkan pada

satu peringkat manakala komposit merendahkan pada dua peringkat. Tenaga

pengaktifan bagi komposit dikira dari analisis TGA. penghabluran dan titik lebur

dikesan melalui analisis kalori pengimbasan kebezaan (DSC). Penubuhan serat

meningkatkan penghabluran komposit. Morfologi struktur telah dijalankan sampel patah

untuk menilai antara muka ikatan antara gentian dan matriks. Lekatan yang lebih baik di

antara gentian dan matriks telah dijumpai untuk kes kompositserat berasaskan dirawat

di hadapan MAPP. Jelmaan fourier spektroskopi sinaran inframerah (FTIR) telah

digunakan untuk mengetahui perubahan-perubahan struktur yang disebabkan rawatan

gentian dan analisis yang dijumpai bahawa rawatan dapat serat untuk mengeluarkan

kompaun bukan cellulosic ke tahap yang berbeza-beza bergantung kepada parameter

rawatan. Kaedah respons permukaan (RSM) telah digunakan untuk mengoptimumkan

parameter proses dan satu set keadaan rawatan yang Terbail adalah 99.96% kuasa

sonication pada 94.46 oC untuk mencapai 28.86 MPa TS.

ix

TABLE OF CONTENT

Page

TITLE OF RESEARCH i

STATEMENT OF AWARD FOR DEGREE ii

SUPERVISOR’S DECLARATION iii

STUDENT’S DECLARATION iv

ACKNOWLEDGEMENT v

LIST OF PUBLICATIONS vi

ABSTRACT vii

ABSTRAK viii

TABLE OF CONTENTS ix

LIST OF FIGURES xv

LIST OF TABLES xix

LIST OF SYMBOLS xxi

LIST OF ABBREVIATIONS xxii

CHAPTER 1 INTRODUCTION

1.1 GENERAL INTRODUCTION 1

1.2 RESEARCH BACKGROUND 4

1.3 PROSPECTS OF NATURAL FIBRE COMPOSITES 6

1.4 PROBLEM STATEMENT 7

1.5 OBJECTIVES 8

1.6 SCOPES 8

CHAPTER 2 LITERATURE REVIEW

2 INTRODUCTION 10

2.1 COMPOSITE (DEFINITION AND CLASSIFICATION) 10

2.1.1 Definition of composite 10

2.1.2 Classification of Composites 11

2.2 POLYMER MATRIX 14

2.2.1 Thermoplastic Polymer 15

x

2.2.2 Thermosetting Polymer 15

2.2.3 Recycled Plastic 16

2.3 NATURAL FIBRE 18

2.3.1 Main Components of Natural Fibres 20

2.3.2 Physical and Mechanical Properties of Natural Fibres 25

2.4 PROPERTIES BASED ON COMPOSITES BASED ON

RECYCLED THERMOPLASTICS

26

2.5 KENAF FIBRE REINFORED POLYMER COMPOSITES 26

2.6 PARAMETERS RELATED TO THE PROPERTIES OF

NATURAL FIBRE REINFORCED POLYMER COMPOSITES

27

2.6.1 Dispersion of Fibre in The Composites 27

2.6.2 Thermal Stability of The Fibre 28

2.6.3 Hydrophilic Nature of Natural Fibre 29

2.6.4 Fibre Length, Orientation and Volume Fraction 29

2.7 COMPOUNDING PROCESS 30

2.8 COMPATIBILIZER AND COUPLING AGENT 33

2.9 FIBRE SURFACE TREATMENT AND ITS IMPACT ON THE

PROPERTIES OF THE COMPOSITE MATERIALS

35

2.9.1 Alkali Treatment 36

2.9.2 Acetylation 37

2.9.3 Peroxide Treatment 38

2.9.4 Ultrasound Treatment 38

2.9.5 Enzymatic Treatment 39

2.9.6 Fibre Surface Modification By Using Coupling Agent 40

2.10 MOISTURE ABSORPTION CHARECTERISTICS OF

NATURAL FIBRE BASED POLYMER COMPOSITE

41

2.11 CONCERN RELATED TO OUTDOOR APPLICATION OF

NATURAL FIBRE BASED POLYMER COMPOSITES

42

xi

2.12 RESPONSE SURFACE METHODE 45

2.13 RATIONAL OF CURRENT WORK 45

CHAPTER 3 METHODOLOGY

3.1 EXPERIMENTAL DESIGN 47

3.2 MATERIALS 49

3.2.1 Polymer Matrix (Recycled Polypropylene) 49

3.2.2 Kenaf Fibre 49

3.3.3 Coupling Agent (MAPP) 51

3.3 FORMULATION OF COMPOSITES 51

3.3.1 Physical Treatment 51

3.3.2 Fibre Treatment through Ultrasound 53

3.3.3 Treatment of Fibre through NaOH 55

3.3.4 Fibre Treatment through Laccase Enzyme 55

3.3.5 Preparation of Composite Specimen 56

3.3.5.1 Mixing Process 57

3.3.5.2 Extrusion Process 59

3.3.5.3 Pelletizing Process 60

3.3.5.4 Injection Molding Process 60

3.4 OPTIMIZATION WITH THE HELP OF RESPONSE SURFACE

METHODE

63

3.5 CHARACTERIZATION OF THE FIBRE AND COMPOSITES 64

3.5.1 Fourier Transform of Infrared Spectrophotometry (FTIR) 65

3.5.2 Scanning Electron Microscope (SEM) 66

3.5.3 Elemental Analysis of Fibre by Energy Dispersive X-ray

Spectroscopy (EDX)

67

3.5.4 Thermogravimetric Analysis (TGA) 67

3.5.5 Differential Scanning Calorimetry (DSC) 68

3.5.6 Melt Flow Index (MFI) 69

3.5.7 Dansity Measurement 70

xii

3.5.8 Mechanical properties of Fibre and Composites 71

3.5.8.1 Single Fibre Tensile Strength 71

3.5.8.2 Tensile Properties of Composites 72

3.5.8.3 Flexural Properties Analysis 73

3.5.8.4 Impact Test 74

3.6 WATER UPTAKE ANALYSIS 75

3.7 ACCELERATED WEATHERING TEST 75

CHAPTER 4 RESULTS AND DISCUSSION

4.1 OPTIMIZATION OF TREATMENT (ULTRASOUND, ALKALI

AND ENZYME) PARAMETERS USING RESPONSE SURFACE

METHOD

77

4.1.1 Ultrasound treatment 78

4.1.2 Alkali treatment 82

4.1.3 Enzymatic treatment 87

4.2 OPTIMIZATION OF FIBRE LOADING AND COUPLING

AGENT EFFECT

91

4.2.1 Tensile properties of the composites 91

4.2.2 Flexural properties analysis 93

4.2.3 Impact test analysis 94

4.2.4 MFI of the composites 95

4.2.5 Densities of the composites 95

4.2.6 Scanning electron microscope analysis 96

4.2.7 Thermogravimetric analysis 97

4.2.8 Differential scanning calorimetry analysis 100

4.2.9 Water uptake analysis 102

4.2.10 Accelerated weathering testing 104

4.3 EFFECT OF ULTRASOUND TREATMENT OF KENAF FIBRE

REINFORCED RECYCLED POLYPROPYLENE COMPOSITE

106

4.3.1 SEM and elemental analysis of fibre before and after

alkali ultrasound treatment

106

xiii

4.3.2 FTIR of fibre before and after ultrasound treatment 108

4.3.3 Tensile properties of fibre 111

4.3.4 Tensile properties of composites 112

4.3.5 Flexural test analysis 115


4.3.7 Density of the fibre and composites 116

4.3.8 Melt Flow Index of Composites 116

4.3.9 Scanning electron microscope of composites 117

4.3.10 Thermogravimetric analysis of composites 119

4.3.11 DSC analysis 120


4.3.13 Accelerated weathering test 122

4.4 EFFECT OF ALKALI TREATMENT OF KENAF FIBRE

REINFORCED RECYCLED POLYPROPYLENE COMPOSITE

124


alkali treatment

124

4.4.2 FTIR of fibre before and after alkali treatment 127












4.5 EFFECT OF LACCASE ENZYME TREATMENT OF KENAF

FIBRE REINFORCED RECYCLED POLYPROPYLENE

COMPOSITE

143


Laccase enzyme treatment

143

xiv












CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS FOR

FUTURE WORK

5.1 CONCLUSIONS 159

5.2 RECOMMENDATIONS FOR FUTURE WORK 161

REFERENCES 163

xv

LIST OF FIGURES

Figure No. Title Page

2.1 Systematic illustration of the structural components of composite

materials.

14

2.2 Classification of natural fibres 19

2.3 Schematic picture of cell wall of the natural plants 21

2.4 Cellulose structure 22

2.5 Lignin structure 23

2.6 Chemical reaction mechanism of natural fibre and MAPP 34

2.7 Acetylation reaction with natural fibre 37

2.8 Laccase-catalyzed oxidation of phenolic hydroxyl groups to

phenoxy radicals.

40

2.9 Reaction between silane and natural fibre 41

3.1 Flow chart of experimental procedure 48

3.2 Green kenaf plant (a), kenaf plant (up rooted) (b), processed green

kenaf fibre (c) and grinded kenaf fibre (d).

50

3.3 Physical treatment for the preparation of kenaf fibre 52

3.4 Plastic crusher 53

3.5 Ultrasound cleaner (Daihan DH. D300H) 54

3.6 Experimental process of ultrasound treatment of kenaf fibre 54

3.7 Experimental procedure of alkali treatment of kenaf fibre 55

3.8 Experimental flow chart of enzymatic treatment of kenaf fibre 56

3.9 Flow chart of test sample preparation. 57

3.10 Twin-screw extruder (model- THERMO SCIENTIFIC

EUROLAB 16) used for compounding

59

3.11 Pelletize machine 60

3.12 Injection molding machine (model-PNX-60) 61

3.13 Basic operations of the injection moulding cycle: (a) start up; (b)

screw back 1; (c) injection; (d) hold-on; (e) screw back 2; (f)

cooling and ejection

62

3.14 Tensile, flexural and impact specimen 63

3.15 FTIR spectrophotometer (Model – Thermo) 65

3.16 SEM apparatus (model-ZEISS, EVO-50) 66

3.17 TGA analyzer (TA Q500) 68

3.18 DSC analyzer (TA Q1000) 69

xvi

3.19 Melt flow indexer (Dynisco) 70

3.20 Gas pycnometer (micromeritics, AccuPyc II 1340) 71

3.21 Universal tensile testing machine (Model- SHIMADZU, AG-1) 73

3.22 Accelerated weathering tester (model-QUV/spray with solar eye

irradiance control)

76

4.1 Predicted vs. Actual (experimental) values of the reponse 80

4.2 Residual plot of the quardratic model for the response 81

4.3 3-D plot of the response as the function of sonication power and

temperture

81

4.4 Interaction graph of the response as the function of sonication

power and temperature

82



4.7 3-D plot of the response as the function of NaOH conc. and time 86

4.8 Interaction graph of the response as the function of NaOH conc.

and time

86



4.11 3-D plot of the response as the function of enzyme activity and

time

90

4.12 Interaction graph of the response as the function of enzyme

activity and time

90

4.13 TS and TM of RPP and composites based on untreated fibres with

and without coupling agent at various percentages of fibre

loading.

92

4.14 Elongation at break (%) of RPP and composites at various loading

of fibres.

93

4.15 FS and FM of RPP and composites with and without coupling

agent at 40% fibre (untreated) loading.

94

4.16 SEM micrographs of untreated/uncoupled (a) and

untreated/coupled (b) formulation based composites.

97

4.17 Thermogram of the RPP and composites with and without

coupling agent at 40% fibre loading.

99

4.18 lnln (1/y) vs. 1/T (K) curve for recycled polypropylene. 99

4.19 Heat Flow (W/g) vs. Temperature (oC) curve to calculate enthalpy

and melt peak temperature of RPP.

101

4.20 Moisture absorptipn by the composites at various time duration. 103

4.21 Deterioration of TS after water uptake analysis. 104

4.22 Deterioration of TS after accelerated weathering testing at various

time period.

105

4.23 SEM of kenaf fibre before (a) and after (b) ultrasound treatment

(high sonication at 95 oC).

107

xvii

4.24 FTIR spectra of untreated (lower) and ultrasound treated (uper)

kenaf fibre.

110

4.25 TS and TM of composites with ultrasound treated (at 60 oC) fibre

at 40% fibre loading with coupling agent.

113

4.26 TS and TM of composites with ultrasound treated (at high

sonication power) fibre at 40% fibre loading with coupling agent.

113

4.27 TS and TM of composites based on treated and untreated fibre

with MAPP at 40% fibre loading.

114

4.28 Elongation at break (%) of untreated/coupled and treated (high

sonication power at 95 oC)/coupled composites.

114

4.29 FS and FM of composites with untreated and treated fibre in the

presence of coupling agent at 40% fibre loading.

115

4.30 SEM of fractured surface of untreated/coupled (a) and treated

(high sonication power at 95 oC)/coupled (b) composite.

118

4.31 Deriv. Weight (%/oC) vs. Temperature (

oC) curve of the

composites based on untreated fibre with coupling agent and

treated (high sonication power at 95 oC) fibre with coupling agent.

119

4.32 Moisture content (%) of the composites at various soaking time

duration (days).

121

4.33 TS (MPa) of composites (before and after water uptake). 122

4.34 Deterioration of TS of composites due to accelerated weathering. 123

4.35 SEM of untreated (a) and treated -5%NaOH/2hr (b),

5%NaOH/4hr (c), 5%NaOH/6hr (d) fibre.

125

4.36 FTIR spectra of untreated (lower) and alkali treated (upper) kenaf

fibre.

128

4.37 TS and TM of composites with alkali treated (2hr of soaking time

duration) fibre at 40% fibre loading with coupling agent (at

various concentration of NaOH).

131

4.38 TS and TM of composites with alkali treated (5% NaOH

concentration) fibre at 40% fibre loading with coupling agent (at

various soaking time duration).

131

4.39 TS and TM of composites based on untreated/coupled and

treated/coupled formulation at 40% fibre loading.

132

4.40 Elongation at break (%) of untreated/coupled and treated (5%

NaOH concentration, 4hr)/coupled formulation based composites

at 40% fibre loading.

133

4.41 FS and FM of composites based on untreated/coupled and

treated/coupled formulation at 40% fiber loading.

134

4.42 SEM of fractured surface of untreated/uncoupled (a),

treated/coupled (b) composites at 40% fibre loading.

137

4.43 Deriv. Weight (%/oC) vs. Temperature (

oC) curves of composites

with untreated and treated fibre with coupling agent at 40% fibre

load.

138

4.44 Moisture content of the RPP and composites (at 40% fibre

loading) at various soaking time duration

140

4.45 TS of the composites (at 40% fibre loading) before and after water

uptake.

141

4.46 Comparison of TS of composites before and after accelerted 142

xviii

weathering.

4.47 SEM of kenaf fibre (a) before and (b) after Laccase enzyme

treatment (80 U/ml at 4 hrs of soaking time duration).

144

4.48 TS and TM of composites based on Laccase enzyme treated fibre

(40% fibre loading) at various enzyme activities for 2 hrs of

soaking time duration.

147

4.49 TS and TM of composites based on Laccase enzyme treated (at 80

U/ml enzyme activity) fibre (40% fibre loading) at various

soaking time duration (hr).

147

4.50 TS and TM of composites based on untreated and treated fibre in

the presence of coupling agent at 40% fibre loading.

148

4.51 Elongation at break (%) of RPP and composites. 149

4.52 FS and FM of composites. 150

4.53 SEM of fractured surfaces of tensile specimen of the composites

based on untreated/coupled (a) and treated/coupled (b)

formulation.

152

4.54 Thermograms of composites based on untreated fibre at various

percentages of fibre loading.

154

4.55 Moisture content of composites against various soaking time

duration.

156

4.56 Deterioration of TS of the composites after water uptake. 157

4.57 Deterioration of TS of composites due to accelerted weathering at

various period of time.

158

xix

LIST OF TABLES

Table No. Title Page

2.1 Annual production of natural fibres and sources 20

2.2 Chemical composition, moisture content, and microfibrillar angle

of vegetable fibres

24

2.3 Characteristic values for the density, diameter, and mechanical

properties of (natural) plant and synthetic fibres

25

2.4 Cell wall polymers responsible for the properties of

lignocellulosics in order of importance

44

3.1 Properties of recycled polypropylene 49

3.2 Physical properties of Maleic Anhydride Grafted Polypropylene

(MAPP): Polybond 3200

51

3.3 Mixing formulations for untreated kenaf fibres with RPP 58

3.4 Mixing formulations of untreated fibre with RPP and coupling

agent

58

3.5 Mixing formulations for treated fibre with RPP and MAPP 58

3.6 Arrangement of experiment using Central Composite Design 64

4.1 Experimental design with actual value range and response for

each run.

78

4.2 Analysis of varience (ANOVA) for tensile strength (MPa) 79


each run.

83



each run.

87


4.7 IS of the composites 94

4.8 Density, MFI and impact strength of the composites 95

4.9 Thermal properties of composites 100

4.10 DSC analysis of composites 101

4.11 Tensile property and density of fibre before and after ultrasound

treatment

108

4.12 Elemental analysis of untreated and ultrasound treated fibre

through EDX analysis.

108

4.13 FTIR spectra of kenaf fibre before and after ultrasound treatment 111

4.14 Density, MFI and Charpy impact strength of the composites 116



xx

4.17 Elemental analysis of untreated and treated kenaf fibre by EDX 125

4.18 FTIR spectra of fibre 129

4.19 Tensile property and density of fibre before and after treatment 130

4.20 Density, MFI and Charpy impact strength of the composites 135



4.23 Elemental analysis of kenaf fibre through EDX before and after

Laccase enzyme treatment.

145

4.24 Tensile properties of untreated and treated fibre 146

4.25 Density, MFI and impact strength of the composites 150



xxi

LIST OF SYMBOLS

y Fraction of non-volatized material not yet decomposed (%)

Tmax Temperature at maximum reaction rate (K)

β Heating rate (oC/min)

z Frequency factor

Ea Activation energy (j/mol.K)

R Gas constant (J.K-1

.mol-1

)

σt Tensile strength (MPa)

A Cross sectional area (m2)

Fmax The maximum peak load (N)

L Original length (mm)

Lo Length at breaking point (mm)

Ef Flexural modulus of elasticity (MPa)

L Support span (mm)

m Applied load (N)

b Width of specimen (mm)

d Depth of specimen (mm)

Wf Final weight (g)

wi Initial weight (g)

xxii

LIST OF ABBREVIATIONS

PP Polypropylene

RPP Recycled polypropylene

PE Polyethylene

LDPE Low density polyethylene

HDPE High density polyethylene

PVC Polyvinylechloride

PLA Polylactic acid

PET Polyethylene terephthalate

MAPP Maleic anhydride grafted polypropylene

MMC Metallic matrix composites

CMC Ceramic matrix composites

PMC Polymer matrix composites

CCC Carbon carbon composite

IMC Intermetallic matrix composites

NaOH Sodium Hydroxide

TS Tensile strength

TM Tensile modulus

FS Flexural strength

FM Flexural modulus

IS Impact strength

SEM Scanning electron microscope

FTIR Fourier transform of infrared radiation

DSC Differential scanning calorimetry

EDX Energy dispersive X-ray

TGA Thermogravimetric analysis

DTA Differential thermal analysis

MFI Melt flow index

WPC Wood plastic composite

CO2 Carbon di-oxide

PBS Polybutadiene styrene

PS Polystyrene

ASTM American Society for Testing and Materials

ISO International Organization for Standardization

HBT 1-hydroxybenzotrlazole hydrate

EDTA Ethylenediaminetetraacetic Acid

YM Young Modulus

RM Malaysian Ringgit

OH Hydroxyl group

UV Ultra violate

MA Maleic anhydride

KF Kenaf fibre

TPNR Thermoplastic Natural Rubber

EPDM Ethylene-polypropylene-diene-monomer

RPM Revulation per minute

RSM Response surface methode

CHAPTER 1

INTRODUCTION

1.1 GENERAL INTRODUCTION

Over the past few decades, there is a growing interest in the development of

composites from natural plant fibres as a renewable source of materials. Natural fibres

such as sisal, kenaf, hemp, henequen, flax, jute, oil palm empty fruit bunch, coconut

fibre (coir), banana, bamboo and wood fibres are belonged to this category, and still

new fibres are being added to this arena. Composites using natural fibres are on the

horizon, thus bringing new trends in composite materials (Satyanarayana et al., 1990).

These fibres are abundantly available in all over the world, and chemically consist of

mainly cellulose, hemicelluloses and lignin. Cellulose fibres present many advantages

compared to synthetic fibres, which, make them attractive as reinforcing agents in the

composite materials. Although, cellulose fibres have very low strength but composites

based on it posses high specific properties due to their low density. Beside this,

cellulose fibres are now considered as the replacement of traditional, synthetic fibres

such as glass, aramid and carbon due to their low cost, good mechanical properties, non-

abrasive nature, eco-friendly and bio-degradability characteristics (Ku et al., 2011).

Although, using natural fibres in the polymer composites has many advantages,

but polar fibres have low compatibility with non-polar hydrocarbon polymer matrices

(examples: polypropylene and polyethylene) (Bledzki et al., 1998 and Cantero et al.,

2003). Therefore, these two different categories of materials don‟t match properly due

to their inherent nature while they are blended together for the preparation of the

composites. Beside this, they can absorb moisture from the environment, due to the

nature of plant based fibres; they may be attacked by the fungi which, results in low life

cycle and poor interfacial bonding between fibres and matrixes etc. So, to improve the

properties, initiation of the following steps has already been taken by the previous

2

researchers. For examples, modification of the fibre surface by some chemical or

enzymatic treatments, addition of coupling agent and using other additives or fillers.

Nam et al. (2011) in a recent work has showed that, the mechanical properties of alkali-

treated coir fibre/PBS composites are significantly higher than those of untreated fibres.

The moisture absorbed by the fibres can be reduced by chemical modifications of fibres

such as acetylation, mercerization (alkaline treatment), methylation, cyanoethylation,

benzoylation, permanganate treatment, acrylation (Sreekala et al., 2003; Seena et al.,

2005; Mishra et al., 2008; Joseph et al., 1997 and Mishra et al., 2011). The use of

enzyme technology is increasing substantially in the processing of natural fibre, and the

use of enzyme in the field of textile and natural fibre modification is also rapidly

increasing. A major reason for using this technology is the fact that application of the

enzyme is considered as environmental friendly, and the reactions catalysed are very

specific with a focussed performance as a consequence. Other potential benefits of

enzyme technology include cost reduction, energy and water saving, improved product

quality and potential process integration (Aehle et al, 2007). Another most useful

technique, which, can be introduced for fibre treatment is ultrasound treatment. This

technique is already being used efficiently for physical and chemical processes due to

ultrasound cavitations‟ effect in the liquid medium which is a growth and explosive

collapse of microscopic bubbles (Liu et al., 2008). Due to sudden collapse of bubbles

hot spot can be generated and localized high temperature, high pressure shock waves

and severe shear force are able to break chemical bonds (Liu et al., 2008). Moreover,

this process can be used as environment friendly instead of so called traditional

chemical treatment of fibres using green chemistry.

Among coupling agent maleic anhydride grafted polypropylene and silane are

mentionable which are using commonly to improve adhesion between natural fibres and

matrices. Kim et al. (2007) in their experiment has found that, MAPP-treated

composites showed strong bonding between fibre and matrix. In addition, the improved

interfacial adhesion of the MAPP-treated composites was confirmed by spectral analysis

of the chemical structure using attenuated total reflectance. For the case of silane, the

interaction modes of the silane and matrix are dominated by the organofunctionality of

silane and the matrix characteristics. Physical compatibility (such as molecular

entanglement or acid–base interactions) between silane-grafted fibre and thermoplastic

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matrices only provides a limited improvement in the mechanical properties of the

resulting composites (Xie et al., 2010).

Application and end uses determines the selection of polymers whether it would

be thermoplastic or thermosetting polymer. Polyesters (Vilay et al., 2008), polyurethane

(Bakare et al., 2010) and epoxy resins (Benjamin et al., 2011) among the thermosetting

polymers are most commonly cited in the journals for the preparation of natural fibre

based polymer composites. Among the thermoplastic polymers, polypropylene (Ichazo

et al., 2001), polystyrene (Antich et al., 2006), poly vinyl chloride (Zheng et al., 2007),

high density polyethylene (Mulinari et al., 2009), low density polyethylene (Sailaja,

2006), and recycled thermoplastics (Corradini et al., 2009) are commonly cited in the

journals.

Polymers are petroleum based product. Petroleum is limited and will be finished

in future. On the other side due to versatile use of polymer, the demand and production

of it increasing sharply. This is the indication of the utilization of petroleum more than

the previous time. Polymer can be reused and recycled. Thus, we should think an

alternate way for the utilization of waste based plastic product to reduce the demand of

petroleum. Recycling of waste based plastic can be used in making some value added

products. The most developed countries like United States, Switzerland etc. are giving

importance on recycling of post consumer plastics. Attempts have been made to recycle

the post-consumer plastics in order to reduce the environmental impact and

consumption of virgin plastics. These lead the researchers work on recycled plastic for

the best use of it. Numbers of research works have been cited on recycled plastics.

Interestingly, the properties of the composites made with pure plastic are same to the

composites made with recycled plastic and in some cases even enhance the properties

(Adhikary et al., 2008).

Natural fibre reinforced composites can be produced in many ways such as

extrusion and injection molding (Suradi et al., 2010); two-roll plastic mill and hot press

(YU et al., 2009), melt blending and compression molding (Lei et al., 2007). Fibres are

normally processed either mechanically or chemically before mixing with polymer

matrix followed by cutting into small size. After that, fibres are blended with polymer

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together with competibillizer (if use any) at a particular temperature for reactive

processing.

The produced composites may have good strength with reasonable flexibity and

can endure a moderate impact load. The interfacial adhesion may be improved due to

the addition of couling agent and treatment of fibre. Combining all the properties of the

composites may suit it for any application.

1.2 RESEARCH BACKGROUND

A number of natural fibres such as flax (Arbelaiz et al., 2005), wheat straw

(Avella et al., 1995), pineapple leaf (Devi et al., 1997), hemp (Benjamin et al., 2011),

abaca (Bledzki et al., 2010), ramie (Yu et al., 2010), coconut (coir) (Haque et al., 2009),

sugarcane bagasse (Corradini et al., 2009), banana (Kazuya et al., 2004), oil palm empty

fruit bunch (Khalid et al., 2008), sisal (Joseph et al., 2002), jute (Albuquerque et al.,

1999), wood (kraft) (Beg et al., 2008) etc. are cited as a reinforcing agent for the

composites materials with various polymer matrix such as high density polyethylene

(Daniella et al., 2009), low density polyethylene (George et al., 1998), poly vinyl

chloride (Zheng et al., 2007), polypropylene (Avella et al.,1995), poly styrene

(Albuquerque et al., 1999), epoxy (Benjamin et al., 2011), poly lactic acid (Islam et al.,

2010), poly ethylene teraphthalate (Corradini et al., 2009) etc. The various advantages

of lignocellulosic plant-based fibres over synthetic fibres are low density, high specific

properties, non-abrasive to the machine-equipments, non-irritation to the human skin

with less health risk, low energy consumption, recyclability, renewability, low cost, and

bio-degradability (Malkapuram et al., 2008). For examples, composite materials are

using as parts or accessories for aerospace, building-construction, sport-item and mostly

for automotive industries (Malkapuram et al., 2008; Wambua et al., 2003).

Some parameters of the composites are regardless to the selection or types of

polymer matrices and natural fibres. For examples, there are many factors that can

influence the performance of natural fibre reinforced polymer composites. Apart, from

the hydrophilic nature of fibre, the properties of the natural fibre reinforced composites

can also be influenced by fibre content or the amount of filler presence in the composite.

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In general, high fibre content is required to achieve high performance of the composites.

Therefore, fibre content has a significant effect on the properties of natural fibre

reinforced composites.

Kenaf (Hibiscus cannabinus L)- a member of the hibiscus family, is a warm

season annual fibre which is closely related to some other natural plant based fibres like

jute, cotton etc. Beside that, it is biodegradable and environmentally friendly crop. In

previous, it has been used as cordage crop for the preparation of twine, rope and

sackcloth etc. In America, it is widely being used as a major ingredient of pulp and

paper. Recently, it has been found to be an important source of fibre for composites and

other industrial applications. It was found that kenaf fibre has almost 45-57% of

cellulose (Bismarck et al., 2005). So, regarding the source of cellulose, it is quite good

to be used in composites materials for reinforcement. Malaysian prospectus regarding

kenaf production and demand are now growing faster. The renowned company,

Panasonic Electric Works which is established in 2004, have monthly consumption of

kenaf fibre of about 600 tonnes from a plant situated in Kuantan, Malaysia. More than

90% of kenaf fibre comes from Bangladesh, and the rest is collectively from Myanmar,

Vietnam and Malaysia (Chen, 2011). Malaysian government has been given the

importance on the cultivation of kenaf fibre in various states of Malaysia. Day by day,

their production in all over Malaysia is increasing and the fibre quality is superior to

other plant based fibre. Moreover, only after 120-150 days, it reaches near about 3-5

meter of average height. Thus, it is found to be a fast growing plant although, it is

considered as a seasonal crop.

On the other hand, currently recycling rate of plastics in Malaysia is only 3 to

5% whereas; the other developed countries already achieved about 30 to 47% (Leoi,

2003). Thus, it is very much essential to increase the recycling rate of polymer based

product as the resource of petroleum is limited. A variety of polymer based product

such as domestic plastic goods, toys, shopping bags, containers, automobile parts such

as vehicle battery case and car bumper can be recyclable when they are not useable after

a long period of its life time. Moreover, a lot of other polypropylene based materials can

be easily recyclable for the enhancement of the recycling rate in Malaysia.

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1.3 PROSPECT OF NATURAL FIBRE COMPOSITES

About 3000 years ago, in ancient Egypt, the straw was used as a reinforcing

agent in clay for the preparation of buildings. This process is even now ongoing in rural

villages of almost all developing countries. After that, a long period of time natural fibre

was not concerned due to the variety of innovations and attractions of others inorganic

materials for their individual characteristics and applications. When the concern turn to

a wide, complex and competitive market of new materials with new potentiality such as

lighter weight, lower manufacturing cost, less CO2 emission, environment friendly,

easily available and most importantly when the concern come to the point that, one day

our limited resources that lie in the underground will be finished, then natural fibres

arise as a new research arena for a sustainable earth and it is now fast growing. In

connection with that, in 1896 natural fibres and a small amount of polymer based binder

were used to prepare aeroplane fuel-tanks and seats which was reported by Bledzki

(1999). Composites prepared from paper or cotton, as a reinforcing agent with phenol or

melamine-formaldehyde for the fabrication of sheets, pipes and tubes were reported as

the first composite based materials in 1908 (Bledzki et al., 1995).

Environmental concerns drive the automakers to develop natural fibre based

composites for the interior of the automobiles. Door panels, seat backs, package trays

and trunk liners which were made from natural fibre based thermoplastics and

thermosetting polymers (Bledzki et al., 1999). Mercedes-Benz, the famous automobile

company, is using natural fibres like flax, hemp, coir and others for the interior of the

vehicle body parts (Bledzki et al., 1999). Jute-coir hybrid composites for panel, flax-

carbon hybrid bike, jute-PP composites for suitcase are some excellent examples of the

utilization of natural fibres.

Other than that, more beneficial aspect of the utilization of natural fibre is they

can be produced at lower utilization of energy and natural fibre can store CO2 to a

significant amount during their growth. Thus, both economical and environmental

concern, natural fibres have a very good prospect to develop it more and more for a

green world.

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1.4 PROBLEM STATEMENT

Due to versatile use, the demand of plastic and plastic made products are

increasing tremendously which leads to create pressure on petroleum resources. Thus,

boosting up the utilization of recycled plastic is necessary. In another way, waste based

product may add some extra values to the existing product regarding cost and energy

consumptions. Moreover, large amount of plastic wastage can cause serious

environmental impact, also limiting land filling area whereas; in some countries this

practice is totally restricted.

Although, a number of researches have been carried out with natural

fibre reinforced polymer composites, however, fibres are not compatible with most

thermoplastics due to their hydrophilic nature whereas; plastics are mostly hydrophobic

in nature.

Natural fibre reinforced polymer composites also produces some

problems like, easily degradable by UV radiation, high moisture absorption, low

weathering stability etc.

Chemical pretreatments or surface modifications of fibres to improve

adhesion and mechanical properties of composites are drawing attention to the

researchers widely. Alkaline peroxide treatment of fibre is the most common one. Still

fibres reinforced composites have those problems mentioned above, and concerns of

environment, health and hazard are also associated with this process. So, other methods

like ultrasound, enzymatic treatment may be used to mitigate this problem. Moreover,

specific properties of composites can be achieved by using those treatment processes

effectively.

There are continuous industrial pressures to invent new composite

materials for sustainability which can be made from low-cost raw materials, through

low manufacturing cost and low energy consumption. At the same time, environmental

concerns to control green house gases emission and light- weighted natural plant based

products are also their requirements.

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1.5 OBJECTIVES

The major objective of this research work was the production and

characterization of composites from kenaf with recycled polypropylene. More

specifically the objectives are to:

Produce composites using treated (alkali, ultrasound and enzymatic)

fibres with recycled plastics and compare the mechanical properties with the untreated

one.

Investigate the effect of MAPP on the mechanical properties of the

composites to enhance the interfacial bonding between fibre and matrix.

Study the effect of extreme weathering and water uptake testing.

1.6 SCOPE

This experiment was carried out to the preparation and characterization of kenaf

fibre reinforced recycled polypropylene composites. Fibre surface modification through

alkali, ultrasound and enzyme were carried out, and the properties of the composites

with the effect of coupling agent were studied. The scopes of this research are as

follows:

1. Treatment of fibre by alkali solution with various treatment variables like

NaOH concentration (3, 5 and 7%) and duration of soaking time (2, 4 and 6hrs).

2. Treatment of fibre by ultrasound with various treatment variables such as

sonication power (low, medium and high) and temperature (60, 80 and 95 oC).

3. Treatment of fibre by laccase enzyme with various treatment variables like

enzyme activity (60, 80 and 100 U/ml) and soaking time duration (2, 4 and 6hrs).

4. Preparation of composite with 10 to 50% fibre loading and optimization

according to the best tensile strength performances.

5. Incorporation of coupling agent with a ratio of 1:10 as coupling agent to

fibre.

6. Production of composites through various reactive processes such as

extrusion and injection molding. Various process variables, such as temperature, screw

speed and rotation were involved with this experiment. Fibre loading and fibre size

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were also important considerations in this experiment. Characterizations of the

composites were done by various mechanical, thermal, structural and morphological

testing.

EFFECT OF FIBRE SURFACE TREATMENT ON KENAF...

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