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THE EFFECT OF CHICKEN FEATHER FIBER LOADING AND CHEMICAL MODIFICATION OF

RECYCLED HIGH DENSITY POLYETHYLENE/

NATURAL RUBBER/ CHICKEN FEATHER FIBER COMPOSITES

MOHAMMED IZZUDDEEN BIN MOHD YAZID

UNIVERSITI MALAYSIA PERLIS 2014

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THE EFFECT OF CHICKEN FEATHER FIBER LOADING AND CHEMICAL MODIFICATION OF

RECYCLED HIGH DENSITY POLYETHYLENE/

NATURAL RUBBER/ CHICKEN FEATHER FIBER COMPOSITES

by

MOHAMMED IZZUDDEEN BIN MOHD YAZID 1230410752

A thesis submitted in fulfillment of the requirements for the degree of Master of Science (Materials Engineering)

School of Materials

UNIVERSITI MALAYSIA PERLIS

Year 2014

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UNIVERSITI MALAYSIA PERLIS

NOTES : * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from the organization with period and reasons for confidentially or restriction.

DECLARATION OF THESIS

Author’s full name : ………...

Date of birth : ………

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Academic Session : ………

I hereby declare that the thesis becomes the property of Universiti Malaysia Perlis (UniMAP) and to be placed at the library of UniMAP. This thesis is classified as :

CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)*

RESTRICTED (Contains restricted information as specified by the organization where research was done)*

OPEN ACCESS I agree that my thesis is to be made immediately available as hard copy or on-line open access (full text)

I, the author, give permission to the UniMAP to reproduce this thesis in whole or in part for the purpose of research or academic exchange only (except during a period of _____ years, if so requested above).

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ACKNOWLEDGEMENT

Alhamdulillah, thank god for His graciousness and mercifulness has gave me the strength and ability to complete this thesis successfully.

I would like to express my utmost appreciation to my respectful supervisor, Assoc. Prof. Dr. Supri A. Ghani for his never ending guidance and support throughout the course of this work. His enthusiasm inspires me throughout the research period to strive as a student, researcher and also as a human. I also would like to extend my gratitude to my co-supervisor, Dr Luqman Musa for his cared and guidance on my study.

Special thanks to Dr. Khairel Rafezi Ahmad, Dean of School of Materials Enginering for his support in completion my research and thesis. My sincere thanks also go to all the staff, technicians and PLV of School of Materials Engineering for their generous effort and assistance in the laboratory’s work. I also want to thank to all my postgraduates colleagues for helping me to get through the difficult times, and for all the emotional support they provided. My days of research and thesis writing were easier with them around.

Last but not least, I record my gratitude to my lovely family especially my parents for their supports, understanding, loveliness and providing the financial support.

I am also grateful to Universiti Malaysia Perlis for giving me the opportunity to be one of their MSc program students. Thank you very much.

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TABLE OF CONTENTS

PAGE

THESIS DECLARATION i

ACKKNOWLEDGEMENT ii

TABLE OF CONTENTS iii

LIST OF TABLES vii

LIST OF FIGURES ix

LIST OF SYMBOLS, ABBREVIATIONS OR NOMENCLATURE xii

ABSTRAK xvi

ABSTRACT xvii

CHAPTER 1 INTRODUCTION

1.1 Research Background 1

1.2 Problem Statement 7

1.3 Objectives 8

1.4 Scope of study 9

CHAPTER 2 LITERATURE REVIEW

2.1 Thermoplastic Elastomers (TPEs) 10

2.1.1 Styrenic Block Copolymers 11

2.1.1.1 Multi-Block Copolymers 12

2.1.1.2 Hard Polymer-Elastomer Combination 13

2.1.1.3 Graft Copolymers 14

2.1.1.4 Ionomers 14

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2.1.1.5 Core-Shell Morphologies 15

2.1.2 Thermoplastic Polyolefin Blends (TPOs) 16

2.1.3 Thermoplastic Vulcanizates (TPVs) 17

2.1.4 Thermoplastic Natural Rubber (TPNR) 18

2.2 Composites 20

2.2.1 Polymer Matrix Composites (PMC) 21

2.3 Recycled Plastic 22

2.3.1 Polyethylene 26

2.3.2 High Density Polyethylene (HDPE) 27

2.3.2.1 Properties of High Density Polyethylene (HDPE) 28 2.3.2.2 Application of High Density Polyethylene 29

2.4 Natural Rubber (NR) 31

2.4.1 Properties of Natural Rubber (NR) 32

2.4.2 Applications of Natural Rubber 33

2.5 Fillers 35

2.6 Natural Fibers 37

2.6.1 Natural Fiber Composites 38

2.6.2 Chicken Feather 40

2.7 Interaction between Natural Fiber and Polymer Matrix 46 2.7.1 The Interphase and Interface in Composites 47

2.7.2 Wetting, Adhesion, and Dispersion 48

2.8 Factors Influencing Natural Fibers in Polymer Composites 50

2.9 Compatibilization 51

2.10 Coupling Agent 52

2.10.1 Benzyl urea 53

2.10.2 ɛ-Caprolactam 53

2.11 Chemical Modification 56

2.11.1 Ethanol 57

2.11.2 Methyl Methacrylate 58

CHAPTER 3 RESEARCH METHODOLOGY

3.1 Materials 61

3.2 Preparation of Chicken Feather Fiber 62

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3.3 Treatment of Chicken Fiber Feathers with Ethanol and Methyl 62 Methacrylate

3.4 Compounding of RHDPE/NR/CFF Composites with Coupling 63 Agent

3.5 Compounding of RHDPE/NR/CFF_Eth Composites and 65 RHDPE/NR/CFF_MMA Composites

3.6 Compression Molding 65

3.7. Testing and Characterizations 66

3.7.1 Tensile Test 66

3.7.2 Swelling Behavior 67

3.7.3 Scanning Electron Microscopy (SEM) 67

3.7.4 Fourier Transform Infrared Spectroscopy (FTIR) 68

3.7.5 Termogravimetric Analysis (TGA) 68

3.7.6 Differential Scanning Calorimetry (DSC) 68 CHAPTER 4 RESULTS AND DISCUSSION

4.1 Properties of HDPE/NR/CFF Composites and RHDPE/NR/CFF 70 Composites

4.1.1 Tensile Properties 70

4.1.3 Morphology Analysis 75

4.1.4 Thermal Degradation of the Composites Using TGA 77 4.2 Effect of Benzyl Urea on Properties of RHDPE/NR/CFF Composites 79

4.2.4 Spectroscopy Infrared Analysis 85

4.2.5 Thermal Degradation of the Composites Using TGA 88

4.2.6 Thermal Properties of DSC 90

4.3 Effect of ɛ-Caprolactam on Properties of RHDPE/NR/CFF Composites 92

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4.3.4 Spectroscopy Infrared Spectroscopy 99

4.4 Effect of Chemical Treatment on Properties of RHDPE/NR/CFF 106 Composites

CHAPTER 5 CONCLUSION AND SUGGESTION

5.1 Conclusion 120

5.2 Suggestions 121

REFERENCES 122

APPENDICES 140

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LIST OF TABLES

NO. PAGE

2.1 Most commonly recycled polymers and their applications 23

2.2 Common thermoplastic and their applications 24

2.3 Classification of polyethylene according to ASTM D 883-00 27

2.4 Different types of fillers 37

2.5 Amino acid content in chicken feather 42

3.1 Ingredients of chicken feather fiber 62

3.2 The formulations of HDPE/NR/CFF composites, RHDPE/NR/CFF composites, RHDPE/NR/CFFBU composites and RHDPE/NR/CFFCL

composites

64

3.3 The formulations of RHDPE/NR/CFFEth composites and RHDPE/NR/CFF_MMA composites

65 4.1 Weight swell percentage of HDPE/NR/CFF and RHDPE/NR/CFF

composites were immersed in toluene at room temperature for 46 hours 75

4.2 Data the weight loss at 500^oC (%) and residual mass (%) of HDPE/NR/CFF and RHDPE/NR/CFF composites from thermogravimetry analysis

79

4.3 Weight swell percentage of RHDPE/NR/CFF composites and RHDPE/NR/CFFBU composites were immersed in toluene at room temperature for 46 hours

83

4.4 The weight loss at 500^oC (%) and residual mass (%) of RHDPE/NR/CFF composites and RHDPE/NR/CFFBU composites from thermogravimetry analysis

89

4.5 The thermal parameter of DSC for RHDPE/NR/CFF composites and RHDPE/NR/CFFBU composites at different fiber loading

92 4.6 Weight swell percentage of RHDPE/NR/CFF and RHDPE/NR/CFF_CL

composites were immersed in toluene at room temperature for 46 hours

96

4.7 The weight loss at 500^oC (%) and residual mass (%) of RHDPE/NR/CFF and RHDPE/NR/CFF_CL composites from thermogravimetry analysis

103

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4.8 The thermal parameter of DSC for RHDPE/NR/CFF composites and RHDPE/NR/CFF_CLcomposites at different fiber loading

105

4.9 Weight swell percentage of RHDPE/NR/CFFEth composites and RHDPE/NR/CFFMMA composites were immersed in toluene at room temperature for 46 hours

111

4.10 The weight loss at 500^oC (%) and residual mass (%) of RHDPE/NR/CFF_Eth composites and RHDPE/NR/CFF_MMA composites from thermogravimetry analysis

116

4.11 The thermal parameter of DSC for RHDPE/NR/CFF_Eth composites and RHDPE/NR/CFF_MMA composites at different fiber loading

119

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LIST OF FIGURES

NO. PAGE

2.1 Morphology of multi-block polymers with crystalline hard segments 13

2.2 Polymer chain of graft copolymer 14

2.3 Chemical structures of (a) ethylene and (b) polyethylene 26

2.4 Schematic of (a) linear and (b) branched arrangement 28

2.5 Isoprene units in natural rubber 31

2.6 Common fillers particle shape 36

2.7 A contour feather 41

2.8 A schematic diagram of chicken feather 44

2.9 Chicken feather keratin (a) fiber structures and (b) surface structure 44 2.10 Contact angle for a liquid drop on a solid surface 50

2.11 The chemical structure of benzyl urea 53

2.12 The chemical structure of ɛ-Caprolactam 54

2.13 Synthesis of ɛ-Caprolactam from 1,3-butadiene 54

2.14 Chemical structure of methyl methacrylate 58

4.1 Tensile strength vs fiber loading of HDPE/NR/CFF composites and RHDPE/NR/CFF composites

71 4.2 Young’s modulus vs fiber loading of HDPE/NR/CFF composites and

RHDPE/NR/CFF composites.

72 4.3 Elongation at break vs fiber loading of HDPE/NR/CFF composites and

RHDPE/NR/CFF composites.

73 4.4 SEM morphology of the tensile fracture surface of HDPE/NR/CFF and

RHDPE/NR/CFF composites, (a) HDPE/NR/CFF-1, (b) HDPE/NR/CFF- 5, (c) HDPE/NR/CFF-10, (d) RHDPE/NR/CFF-1, (e) RHDPE/NR/CFF- 5, and (f) RHDPE/NR/CFF-10.

77

4.5 TG thermogram of HDPE/NR/CFF composites and RHDPE/NR/CFF composites with different fiber loading

78

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4.6 Tensile strength vs fiber loading of RHDPE/NR/CFF composites and RHDPE/NR/CFF_BU composites.

80 4.7 Young’s modulus vs fiber loading of RHDPE/NR/CFF composites and

RHDPE/NR/CFFBU composites

81 4.8 Elongation at break vs fiber loading of RHDPE/NR/CFF composites and

RHDPE/NR/CFFBU composites

82 4.9 SEM morphology of the tensile fracture surface of RHDPE/NR/CFF

composites and RHDPE/NR/CFFBUcomposites, (a) RHDPE/NR/CFF-1, (b) RHDPE/NR/CFF-5, (c) RHDPE/NR/CFF-10,

(d) RHDPE/NR/CFF_BU-1, (e) RHDPE/NR/CFF_BU-5, and (f) RHDPE/NR/CFFBU-10.

85

4.10 Infrared spectroscopy spectra of (a) RHDPE/NR, (b) RHDPE/NR/CFF-5 composites, and (c) RHDPE/NR/CFFBU-5 composites.

86 4.11 Proposed interaction of benzyl urea with chicken feather fibers and

RHDPE/NR matrix

87

4.12 TG thermogram of RHDPE/NR/CFF composite and RHDPE/NR/CFFBU

composites at different fiber loading

89 4.13 DSC thermograms of RHDPE/NR/CFF composites at different fiber

loading.

91 4.14 DSC thermograms of RHDPE/NR/CFFBU composites at different fiber

loading

91 4.15 Tensile strength vs fiber loading of RHDPE/NR/CFF composites and

RHDPE/NR/CFFCL composites

93 4.16 Young’s modulus vs fiber loading of RHDPE/NR/CFF composites and

RHDPE/NR/CFFCL composites

94 4.17 Elongation at break vs fiber loading of RHDPE/NR/CFF composites and

RHDPE/NR/CFFCL composites.

composites and RHDPE/NR/CFFCL composites, (a) RHDPE/NR/CFF-1, (b) RHDPE/NR/CFF-5, (c) RHDPE/NR/CFF-10,

(d) RHDPE/NR/CFF_CL-1, (e) RHDPE/NR/CFF_CL-5, and (f) RHDPE/NR/CFFCL-10.

98

4.19 Infrared spectroscopy spectra of (a) RHDPE/NR, (b) RHDPE/NR/CFF-5 composites, and (c) RHDPE/NR/CFFCL-5 composites.

100

4.20 Proposed interaction of ɛ-Caprolactam with chicken feather fibers and 101

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4.21 TG thermogram of RHDPE/NR/CFF_CL composites for different fiber loading.

102 4.22 DSC thermogram of RHDPE/NR/CFF composites at different fiber

loading

104 4.23 DSC thermogram of RHDPE/NR/CFF_CL composites at different fiber

loading

105 4.24 Tensile strength vs fiber loading of RHDPE/NR/CFF_Eth composites and

RHDPE/NR/CFF_MMA composites.

107

4.25 Young’s modulus vs fiber loading of RHDPE/NR/CFFEth composites and RHDPE/NR/CFF_MMA composites.

109 4.26 Elongation at break vs fiber loading of RHDPE/NR/ CFFEth composites

and RHDPE/NR/CFF_MMA composites

composites, RHDPE/NR/CFFEth composites and RHDPE/NR/CFFMMA

composites,(a) RHDPE/NR, (b) RHDPE/NR/CFF-1, (c) RHDPE/NR/CFFEth-1, (d) RHDPE/NR/CFFMMA-1, (e) RHDPE/NR/CFF-5, (f) RHDPE/NR/CFFEth-5, (g) RHDPE/NR/CFF_MMA-5, (h) RHDPE/NR/CFF-10, (i) RHDPE/NR/CFFEth-10, and (j) RHDPE/NR/CFFMMA-10

114

4.28 TG thermogram of RHDPE/NR/CFF, RHDPE/NR/CFF_Eth and RHDPE/NR/CFF_MMA composites for different fiber loading

115

4.29 DSC thermogram of RHDPE/NR/CFF composites at different fiber loading

117 4.30 DSC thermogram of RHDPE/NR/CFFEth composites at different fiber

loading

118 4.31 DSC thermogram of RHDPE/NR/CFFMMA composites at different fiber

loading

118

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LIST OF SYMBOLS, ABBREVIATIONS OR NOMENCLATURE

ABS Acrylonitrile-butadiene-styrene

AE Acoustic emission

ASTM American Society for Testing and Materials

AT Attapulgite

Br Bromine

CFF Chicken feather fiber CMC Ceramic matrix composites

CNT Carbon nanotube

COPE Copolyester

Cu Copper

DSC Differential scanning calorimetry

EB Electron-beam

EPDM Ethylene propylene diene monomer EPM Ethylene propylene rubber

EVA Ethylene vinyl acetate

Ff Feather fiber

FTIR Fourier transform infrared spectroscopy

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xiii HDPE High density polyethylene HIPS High-impact polystyrene

iPP Isotactic polypropylene

Kf Retted kenaf bast fiber

LDPE Low density polyethylene LLDPE Linear low density polyethylene LNR Liquid natural rubber

MA-g-PP Maleic anhydride-grafted-polypropylene MANR Maleic anhydride grafted natural rubber MAPE Maleic anhydride-grafted-polyethylene MAPP Maleated polypropylene

MDPE Medium density polyethylene

MMA Methyl methacrylate

MMA-g-LR Methyl methacrylate-grafted latex rubber MMC Metal matrix composites

MNR Maleated natural rubber

MRPRA Malaysian Rubber Producers’ Research Association MWNT Multiwall carbon nanotubes

NaOH Sodium hydroxide

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Nf Recycled news pulp fiber

NR Natural rubber

NRP Natural rubber powder

OA Oleic acid

PBS Polybutylene succinate

PCBs Printed circuit boards

Pf Recycled kraft pulp fiber

Phr Part per hundred resins PLA Poly (lactic acid)

PMC Polymer matrix composites PMMA Poly (methyl methacrylate)

PP Polypropylene

PVA Poly (vinyl alcohol) PVC Poly (vinyl chloride)

RHDPE Recycled high density polyethylene RTR Reclaimed tire rubber

SBC Styrenic block copolymers SEM Scanning electron microscopy

SNR Synthesized polystyrene-modified natural rubber

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Td Decomposition temperature

T_g Glass transition temperature TGA Thermogravimetric analysis

TiO₂ Titanium dioxide

T_m Melting temperature

TPE Thermoplastic elastomer

TPNR Thermoplastic natural rubber

TPO Thermoplastic polyolefin elastomers TPU Thermoplastic polyurethane

TPV Thermoplastic vulcanizates

UHMWPE Ultra-high molecular weight polyethylene VPP Virgin isotactic polypropylene

WPC Wood polymer composite

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Kesan Muatan Serat Bulu Ayam dan Modifikasi Kimia pada Komposit Polietilena Ketumpatan Tinggi Kitar Semula/Getah Asli/Serat Bulu Ayam

ABSTRAK

Komposit polietilena ketumpatan tinggi kitar semula/getah asli/serat bulu ayam (RHDPE/NR/CFF) telah disediakan menggunakan Brabender Plasticorder pada suhu 160˚C dan kelajuan rotor 50 rpm. Kesan kandungan CFF dan ejen gandingan ke atas sifat-sifat tegangan, sifat pembengkakan, morfologi, analisis spektroskopi inframerah (FTIR), pemeteran kalori pengimbasan kebezaan (DSC) dan analisis pemeteran graviti haba (TGA) komposit RHDPE/NR/CFF telah dikaji. Keputusan menunjukkan bahawa penambahan CFF telah mengurangkan kekuatan tegangan, pemanjangan pada takat putus dan darjah penghabluran, manakala modulus Young, peratus pembengkakan berat dan kestabilan terma komposit pula telah meningkat. Ejen gandingan seperti benzil urea dan ɛ-Kaprolaktam telah digunakan, dimana kesan positif pada sifat-sifat tegangan dan sifat pembengkakan komposit RHDPE/NR/CFF telah dihasilkan. Kehadiran benzil urea dan ɛ-Kaprolaktam telah meningkatkan kekuatan tegangan, modulus Young, dan kestabilan terma tetapi telah mengurangkan darjah penghabluran. Di samping itu, komposit RHDPE/NR/CFF juga telah dirawat menggunakan etanol dan metil metakrilat. Komposit RHDPE/NR/CFF dengan rawatan etanol mempunyai kekuatan tegangan, modulus Young, dan kestabilan terma yang lebih tinggi tetapi pemanjangan pada takat putus, peratus pembengkakan berat dan darjah penghabluran pula lebih rendah jika dibandingkan dengan komposit RHDPE/NR/CFF dengan rawatan metil metakrilat. Mikroskop penskanan elektron (SEM) permukaan patahan tegangan untuk komposit modifikasi kimia dengan benzil urea, ɛ-Kaprolaktam, etanol dan metil metakrilat menunjukkan bahawa interaksi antara muka di antara CFF dengan adunan RHDPE/NR adalah lebih baik dibandingkan dengan komposit kawalan RHDPE/NR/CFF.

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The Effect of Chicken Feather Fiber Loading and Chemical Modification of Recycled High Density Polyethylene/ Natural Rubber/ Chicken Feather Fiber

Composites

ABSTRACT

Recycled high density polyethylene/ natural rubber/ chicken feather fiber (RHDPE/NR/CFF) composites had been prepared using Brabender Plasticorder at temperature 160˚C and rotor speed of 50 rpm. The effect of CFF content and coupling agent on tensil properties, swelling behavior, morphology, spectroscopy infrared (FTIR) analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of RHDPE/NR/CFF composites were studied. The result showed that the addition of CFF reduced the tensile strength, elongation at break and degree of crystallinity, whereas the Young’s modulus, weight swell percentage, and the thermal stability of composites increased. Coupling agent such as benzyl urea and ɛ- Caprolactam were used, which resulted in positive effect on mechanical properties, and swelling behavior of RHDPE/NR/CFF composites. The presence of benzyl urea and ɛ- Caprolactam, have increased the tensile strength, Young’s modulus, and thermal stability but the degree of crystallinity decreased. In addition, RHDPE/NR/CFF composites were treated using ethanol and methyl methacrylate. The ethanol treated RHDPE/NR/CFF composites have higher tensile strength, Young’s modulus, and thermal stability but lower elongation at break, weight swell percentage and the degree of crystallinity compared to the methyl methacrylate treated RHDPE/NR/CFF composites. The scanning electron microscopy (SEM) micrographs of tensile fracture surfaces for the composites with chemical modification of benzyl urea, ɛ-Caprolactam, ethanol and methyl methacrylate indicated that the interfacial interaction between CFF and RHDPE/NR blends were better than the control RHDPE/NR/CFF composites.

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1 CHAPTER 1

INTRODUCTION

1.1 Research Background

Thermoplastic elastomers (TPEs) are rubbery materials with an equivalent performance in terms of elasticity as the conventional thermoset rubbers. Due to the favorable manufacturing methods and environmental considerations, replacement of conventional vulcanized rubber by TPEs for industrial applications is growing rapidly.

The major advantage in some cases is that the middle range properties are better than those showed by either of the single materials. Moreover, some adjustments in terms of, cost, processing characteristics and durability are achievable through polymer blending.Thermoplastic elastomers (TPEs) can be fabricated from polymer blends made up of thermoplastic polymers, non-vulcanized rubber and vulcanized rubber (Nevatia et al., 2002). The resulting TPEs exhibit rubbery characteristics while retaining its thermo plasticity. The excellent properties of TPEs make them cover a wide range of applications in many industries, particularly in automotive industry such as body side moldings, interior skin and airbag covers. Other major applications are weather stripping, wire insulation, food wear and general mechanical goods such as hose and tube.

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In addition, the TPEs have a lot of commercial significance, which is fabricated without having vulcanization process, while available for reprocessing work to avoid the waste (Kahar et al., 2012). Among the various types of TPEs, the blending of natural rubber (NR) and polyolefin (Polyethylene) physically had caught respectable attention because of the uncomplicated preparation and less effort to achieve the needed technical properties. Furthermore, its environmental friendly approach has gain a lot of reputation since TPEs is recyclable. It has the potential to be recycled again and again without suffering losing the substantial properties (Grigoryeva et al., 2004).

Recycled polyethylene is the largest amount plastic manufactured in the world and extensively used polyolefin. Recycled polyethylene is produced in numerous polymeric forms, varying by their linearity and molecular weight, or branches, or presence of irregularities and many more. The density of the polymer is used as the principals classification features of polyethylene (Klyosov, 2007). Polyethylene exhibits a range of tensile strength and flexibilities, is generally tough, can be readily extruded or molded, and is relatively inexpensive. These characteristics guarantee that the various families of PE find major use as a commodity polymer.

The post-consumer plastics recycling stays one of the desired recycling options for ecological and energy reasons, as long as it stays economically profitable. The recycled post-consumer plastics are low in cost, due to the rising number of plastic waste produced daily in large cities around the world. Furthermore, the post-consumer plastics recycling offer the solution for landfill problem. The municipalities are becoming more concerned about the increasing of plastic waste generation every year (increasing at 25% per year) when the landfill area only capable to increase at 7.5% per year. It is estimated that by 2015, there will be out of disposal options for plastic waste.

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High density polyethylene (HDPE) is a famous plastic type due to its versatility, having a wide range of applications such as consumer goods, containers and furniture.

Post-consumer HDPE from bottles is a fascinating source of recycled material because, on one hand, it cannot be used again in alimentary applications and, on the other hand, its high melting viscosity makes direct transformation via injection moulding very difficult. Recycled HDPE can be used in an increasing amount of potential applications, as long as the mechanical, impact, and thermal properties of the material (recycled- virgin) is not far from each other (Maspoch et al., 2005).

Natural rubber (NR) is an elastomer acquired from rubber tree latex that consist of 93–95% cis-1, 4-polyisoprene. NR has various outstanding properties, such as high strength, superior resilience, and good processability. The good properties, especially resilience, play an important role among other elastomers (Harper, 2000). The applications of NR include automotive tire, tire tread, gloves, and mechanical goods.

Polymer composites are the combinations of materials consisting reinforcing phase (fibers, particles or sheets) and the matrix phase (polymer, ceramic or metal). Leading elements in a fiber-reinforced composite material are the matrix and reinforcing fibers.

The main idea of filler into the composites is to improve certain properties and lower the cost of the composites (Manchado & Arroyo, 2002).

Proper decision of the fiber length, fiber type, fiber orientation and fiber volume fraction is very crucial, since it influences the density, cost, and the composite properties such as tensile properties (Cao et al., 2012), thermal properties (Singha &

Thakur, 2009), mass swell resistance (Abu Bakar et al., 2010). The strength and the stiffness of the composites are influenced by disorientation of fibers, fibers of nonuniform strength, discontinuous fibers, Interfacial conditions and the residual

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stresses. For example, composites strength and stiffness will be reduced when the fibers are not parallel to the loading direction.

The application of natural fibers for the composites reinforcement has caught growing attention. It holds many significant rewards over synthetic fibers (Begum &

Islam, 2013). At this moment, numerous types of natural fibers have been studied for use in composites such as jute straw (Liu & Dai, 2007), hemp (Placet et al., 2012), flax (Bourmaud et al., 2013), rice husk (Ndazi et al., 2007), wood (Coutinho & Costa, 1999), wheat (Panthapulakkal et al., 2006), sugarcane (Lu et al., 2006), grass (De et al., 2004), kenaf (Feng et al., 2001), ramie (Goda et al., 2003), reeds (Han et al., 2001), sisal (Nair et al., 2000), coir (Rout et al., 2001), water hyacinth (A. G. Supri & Lim, 2009), kapok (G. V. Reddy et al., 2008), banana fiber (Pothan et al., 2003), pineapple leaf fiber (J.

George et al., 1997) and papyrus (Nishino et al., 2007).

Natural fibers are extensively separated into three classes depending on their source:

animal based, plant based, and mineral based. Plant-based fibers are ligno-cellulosic in nature consisted of lignin, hemicellulose and cellulose. On the other hand, animal based fibers are of proteins such as wool and silk. Generally, a mineral based composite is asbestos fiber and is only a naturally occurring mineral fiber (silicate based mineral).

Natural fiber-reinforced polymer composites have captivated many research pursuits due to their possibility to replace synthetic fiber composites such as carbon or glass fiber composites (Bledzki & Gassan, 1999). This happens because of natural fibers exceed synthetic fibers in term of less damage to processing equipment, lower weight, lower cost, good relative mechanical properties, better surface finish of moulded parts composite and renewable resources (Corbiere-Nicollier et al., 2001; Joshi et al., 2004).

However, despite the potential of replacing the synthetic fibers, natural fibers do have

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some problems at high fiber content due to the fiber-fiber interaction and fiber dispersion problems.

Many researchers reported that the mechanical properties for polymer composites reinforced with natural fiber are largely dependent on the matrix-fiber interface adhesion (Chin & Yousif, 2009; Rosa et al., 2009). This is primarily because natural fibers are abundant in hemicellulose, celluloses, lignin and pectin, which are hydroxyl groups. Natural fibers have the tendency to be hydrophilic and strong polar materials while polymers are hydrophobic. As a result, there are obvious problems of the matrix- fiber incompatibility, which weakens natural fiber-matrix interface area. However, many researchers suggested that chemical treatments namely alkali, acetylation, and bleaching treatment may enhance the interfacial adhesion between the matrix and the fiber (Alawar et al., 2009; Cantero et al., 2003; Haque et al., 2009; Hepworth et al., 2000; Saha et al., 2010). These chemical treatments clean the fibers surface from impurities thus increases the fiber surface roughness and interrupting the moisture absorption process by withdrawing the OH groups in fiber (Shalwan & Yousif, 2013).

ε-Caprolactam (C6H11NO, CPL) is used as a coupling agent in this research. It is a popular industrial organic chemical material that is used widely in the manufacture of polyamide engineering plastics and fiber. The final product properties depend on the purity of ε-Caprolactam. Water is widely occurring impurity in ε-Caprolactam, and it is usually eliminated by distillation. ε-Caprolactam is heat-sensitive substance, thus, the triple-effect evaporation process is widely used in the manufacture of high-quality caprolactam (Lin et al., 2012). Recently, Zhu et al. (2010) and Li et al. (2010) synthesized crosslinked PVA and other polymer membranes for the PV separation of CPL-water solution. The researchers reported that the decreasing crystallinity of the membrane‘s active layer will increased the flux.