DEVELOPMENT OF HIGH PERFORMANCE LIGHTWEIGHT NANOCOMPOSITE SPORT SHOE
HUSNIYAH ALIYAH LUTPI
A dissertation submitted in fulfilment of the requirement for the degree of Master of Science
Kulliyyah of Engineering
International Islamic University Malaysia
The selection of material for shoe soles is important as it determines the long-term performance of sports shoes, especially the performances of athletes’ shoes with respect to comfort during walking, running, and jumping. An effective approach is developed to establish a strong high-density polyethylene (HDPE)/ethylene propylene rubber (EPR) matrix by introducing electron beam (EB) radiation to the nanocomposite as a crosslinking technique. This study focuses on the variation of carbon nanotubes (CNTs) in the HDPE/EPR polymer blend. The aim of this research is to find the optimum CNT content for the mechanical and thermal properties of EB- irradiated HDPE/EPR nanocomposite for shoe soles. The nanocomposites were melt blended before being compression moulded to form the specimens. The specimens were then irradiated under EBs at 100 kGy. The effect of CNT contents of 0.5, 1, 3, and 5 wt% on the mechanical properties of HDPE/EPR–CNT nanocomposites was investigated for application as the outer shoe sole. Meanwhile the content of organo montmorillonite (OMMT) filling the HDPE/EPR matrix was maintained at 4 wt% for insole shoe application. The combinations of nanofillers and polymer matrix enhance the performance of sports-shoes soles since they each exhibit superior properties. The irradiated and unirradiated nanocomposites were compared and analysed in terms of the mechanical and thermal properties. The irradiated nanocomposite with a CNT content of 3 wt% showed an improvement of the mechanical properties. The tensile strength and impact strength increased by nearly 50% compared to unirradiated and unreinforced CNTs. The thermal properties of the irradiated nanocomposite also showed an improvement in the glass transition temperature (Tg) of 9.6%, an increase in the melting temperature (Tm) from 133.2 to 134.7 °C, and a slight increment in the storage modulus (E’) from 2.45 to 2.50 MPa when compared with irradiated matrix.
These findings were also supported by field emission scanning electron micrography (FESEM) and transmission electron microscope (TEM), where distribution and disaggregation of nanofillers was observed. X-ray diffraction (XRD) showed greater intensity with the addition of CNT and EB radiation. The prototype of the outer sole HDPE/EPR–CNT nanocomposite showed an improvement in the flexing test, where it had the highest number of counts, indicating the ability of the prototype to withstand a bending force at a specific angle until it fully cracks. The enhancement of mechanical and thermal properties of irradiated HDPE/EPR-3 wt% CNTs established the development of high-performance lightweight nanocomposite sport shoe soles.
لاعنل داولما رايتخا نإ ءاذلحا
ةيذحأ اميس لا ليوطلا ىدم ىلع ةيضايرلا ةيذحلأا ءادأ دديح هنأ ابم ادج ماه ينيضايرلا
ءانثأ ةحارلا صوصبخ لا
يرس زفقلاو يرلجاو لا نم ممصلما بلاقلا ءاشنلإ ةلاّعفلا ةقيرطلا عضو تمو .
لياع ينليتيإ ليوب
ةفاثكلا ( ) HDPE ينليبوبرلاو ينليتيلإا نم طاّطم /
( ) EPR ةمزلحا عاعشإ يمدقت قيرط نع لإا
ةينوروكل ( ) EB
كيبشتلا ةينقت هفصوب ةيونانلا ةبيكرولل .
عاونأ ىلع ةساردلا هذه زكرتو ةيونانلا نوبركلا بيبانأ
CNTs ( في ةدوجولما )
تايرميلوب جئازم نم ةنوكلما
/ HDPE . EPR
فاشتكا لىإ ثحبلا اذه فدهيو ىلثلما ةجردلا
ىوتلمح بنأ و ب
يونانلا نوبركلا CNT (
ةيرارلحاو ةيكيناكيلما تييصالخ ) نم ةنوكلما ةيونانلا ةبيكرولل
/ HDPE او EPR
لم ةمزلحاب ةعش
لإا ةينوروكل ( ) EB لاعنل ءاذلحا . عينصتل ةطوغضم ةبلوقلا نوكت نأ لبق ةيونانلا ةبيكرولا طيلخ رهص تمو تانّيعلا
تانّيعلا ةعشعش تم ،ثم ب
تامزلحا عاعشإ لإا
ةينوروكل ( ) EBs في 011 يارغ وليك .
ىوتمح رثأ قيقتح تم ،لياتلابو
بنأ و يونانلا نوبركلا ب CNT (
يهو ) و 1.0 و 0 و 3 ةينزو ةبسن 0 wt% (
ةيكيناكيلما ةيصالخا ىلع ) ةبيكرولل
ةيونانلا نم ةعونصلما / HDPE
يجرالخا ءاذلحا لاعنل EPR .
و كلذ نوضغ في ىوتمح ىقبي ،
يرومتنوم ل تيان
ةيوضع (OMMT) بلاقل ةوشحك
ةينزو ةبسن 4 wt% (
لعن ) ا ل لحا ءاذ لا يلخاد . نم
لحا بيكرت نأ ظحلالما ةيقوفتلا ةيصالخا رهظي هنأ ثيح يضايرلا ءاذلحا لاعن ءادأ زّزعي رميلوبلا بلاقو ونانلا وش
ةيرارلحاو ةيكيناكيلما تييحان نم اهليلتحو ةعشعشلما يرغو ةعشعشلما ةيونانلا ةبيكرولا ةنراقم تم ،انه .
عم ةعشعشلما ىوتمح
بنأ و يونانلا نوبركلا ب CNT (
نم ) ةينزو ةبسن 3 wt% (
ةيكيناكيلما ةيصالخ انستح زبرت ) .
تدادزا مواقم تي دشلا و مدصلا 01 ب ةنراقم ابيرقت % نأا
بي يونانلا نوبركلا ب ة
( ) CNTs ةاوقم يرغو ةعشعشم يرغ
في انستح رهظت اضيأ ةعشعشلما ةيونانلا ةبيكرولل ةيرارلحا ةيصاخو يجاجزلا لّوحتلا ةرارح ةجرد
( يأ ) 6.9
عافتراو راهصنلاا ةرارح ةجرد (
نم ) 033.1 لىإ
034.1 نيزختلا لماعم في فيفخ ديازتو ، °C
1.40 ىلإ لاكسب اغيم 1.06
عشعشم يرغ بلاقب ةنراقم MPa ةمّعدم ثحبلا جئاتن هذه .
ب يرهلمجا ريوصتلا
لإا يوروكل لما سا ب رادصإ ّيلق لحا
ره لإا يوروكل لا سكاع (TEM) لاصفناو عيزوت ةبقارم تم ثيح
ونانلا وشلحا .
و ةينيسلا ةعشلأا دويح (XRD)
فشكي لأا عاعشلإا ةفاثك ةدايزب ضو
بنأ و يونانلا نوبركلا ب
CNT ( ) ةمزلحا عاعشإ و لإا
ةينوروكل EB (
يلصلأا جذومنلا .) ةيونانلا ةبيكرولا نم نم ةعونصلما يجرالخا ءاذلحا لاعنل
HDPE/EPR–CNT لا رهظي
في يلصلأا جذومنلا ةردق لىإ يرشم ،دادعتلا رثكأ هلو نيلحا رابتخا في ينسحت
اماتم رسكنا تىح ةددمح ةيواز في ءاننحلاا ةوق ةمواقم .
لأ ةيرارلحاو ةيكيناكيلما تييصاخ ينستح ،كلذل ناب
ي نوبركلا ب
يونانلا ة CNTs ( ةعشعشلما )
نم ةينزو ةبسن 3 wt% (
نم ةعونصلما ) HDPE/EPR
ررقي لاعن ريوطت تبثيو
ةيونانلا ةبيكرولا نم ةعونصلما ةيضايرلا ءاذلحا ءادلأا لياع
I certify that I have supervised and read this study and that in my opinion, it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Master of Science (Materials Engineering).
Hazleen Anuar Supervisor
Noorasikin Samat Co-Supervisor
I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Master of Science (Materials Engineering).
Zuraida Ahmad Examiner
Ma’an Fahmi Rashid Alkhatib Examiner
This dissertation was submitted to the Department of Manufacturing and Materials and is accepted as a fulfilment of the requirement for the degree of Master of Science (Materials Engineering).
Mohammad Yeakub Ali Head, Department of
Manufacturing and Materials
This dissertation was submitted to the Kulliyyah of Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Science (Materials Engineering).
Md Noor Bin Salleh
Dean, Kulliyyah of Engineering
I hereby declare that this thesis is the result of my own investigations, except where otherwise stated. I also declare that it has not been previously or concurrently submitted as a whole for any other degrees at IIUM or other institutions.
Husniyah Aliyah Lutpi
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARH
Copyright © 2015 by International Islamic University Malaysia. All rights reserved.
DEVELOPMENT OF HIGH PERFORMANCE LIGHTWEIGHT NANOCOMPOSITE SPORT SHOE SOLES
I hereby affirm that The International Islamic University Malaysia (IIUM) holds all the rights in the copyright of this Work and henceforth any reproduction or use in any form or by means whatsoever is prohibited without the written of IIUM. No part of this unpublished research may be reproduced, stored in a retrieval system, or transmitted, in any form or by means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of the copyright holder.
Affirmed by Husniyah Aliyah Lutpi
First of all, I am grateful to Allah SWT, for guiding me during the course of this research. Indeed, without His Help and Will, nothing is accomplished.
I would like to take this opportunity to extend my sincerest gratitude to my supervisor, Dr. Hazleen Anuar for her ever-lasting enthusiasm, encouragement, excellent advice and great concern to my work. I really appreciate her guidance and helpful advises given to me throughout this research. Although being busy, yet she extends her time to monitor my progress and this encourages me to work with greater determination.
I am also wish to register my deep appreciation and sincere thanks to my co-supervisor, Dr. Noorasikin Samat for her help, guidance, motivation and invaluable advices.
I would also like to thank Sis. Nur Aimi Nasir and Sis. Nur Ayuni Jamal for a tremendous help in completing my research period. Not to forget, all the staffs in IIUM, SIRIM, MINT and MARDI for giving help in every possible way. I would also wish to express my thankful to all the technicians especially Bro. Hairi and members of composite laboratory for helping and making the lab an enjoyable place to work.
I am gratefully acknowledged to Research Management Center (RMC), for generous financial and Ministry of Higher Education (MOHE) and UKM for providing me scholarship, Fellowship Scheme to carry out the study.
Lastly, thank you also to my family for their constant prayers and support, the entire lecturer from Department of Manufacturing and Materials (MME) and those who have contributed in the preparation of this thesis.
TABLE OF CONTENTS
Abstract ... ii
cartsbAt in Arabic ... iii
Approval Page ... iv
Declaration ... v
Copyright ... vi
Acknowledgements ... vii
List of Tables ... x
List of Figures ... xi
List of Abbreviations ... xiv
CHAPTER 1: INTRODUCTION ... 1
1.1 Overview... 1
1.2 Problem Statement and Significance ... 3
1.3 Research Objectives... 4
1.4 Scope of Research... 4
1.5 Thesis Organization ... 5
CHAPTER 2: LITERATURE REVIEW ... 8
2.1 Introduction... 8
2.2 Background of Materials Used ... 8
2.2.1 High Density Polyethylene (HDPE) ... 8
2.2.2 Ethylene Propylene Rubber (EPR) ... 11
2.2.3 Carbon Nanotube (CNT) ... 13
2.2.4 Montmorillonite (MMT) ... 17
2.3 Nanocomposite Treatment ... 20
2.4 Shoe Soles ... 23
2.5 Summary ... 26
CHAPTER 3: EXPERIMENTAL METHOD ... 27
3.1 Introduction... 27
3.2 Materials ... 27
3.3 Fabrication of Polymer Blend and Nanocomposites ... 28
3.3.1 Preparation of HDPE/EPR Blend ... 28
3.3.2 Preparation of Polymer Blend and Nanofiller ... 28
3.4 Compression Moulding ... 29
3.4.1 Compression of Polymer Blend and Nanocomposite ... 29
3.4.2 Compression of Outer sole Prototype ... 30
3.5 Electron Beam Radiation ... 30
3.6 Characterization of Nanocomposites ... 31
3.6.1 Tensile Test ... 31
3.6.2 Impact Test ... 31
3.6.3 Hardness Test ... 31
3.6.4 Wear Test ... 32
3.6.5 Outer sole Flexing Test ... 32
3.6.6 Thermogravimetric Analysis (TGA) ... 33
3.6.7 Differential Scanning Calorimeter (DSC) Analysis ... 33
3.6.8 Dynamic Mechanical Analysis (DMA) ... 35
3.6.9 Gel Content Analysis ... 35
3.6.10 X-Ray Diffraction Analysis (XRD) ... 36
3.6.11 Field Emission Scanning Electron Microscope (FESEM) ... 36
3.6.12 Transmission Electron Microscopy (TEM) ... 37
3.7 Summary ... 37
CHAPTER 4: RESULTS AND DISCUSSION ... 38
4.1 Introduction... 38
4.2 Tensile Properties ... 38
4.2.1 Tensile strength ... 38
4.2.2 Tensile Modulus ... 42
4.2.3 Strain at Break ... 44
4.2.4 Stress–Strain Curve ... 47
4.3 Impact Strength ... 50
4.4 Hardness ... 53
4.5 Wear Test ... 55
4.6 Gel Content Analysis ... 58
4.7 X-Ray Diffraction Analysis (XRD) ... 61
4.8 Thermogravimetric Analysis (TGA) ... 65
4.9 Differential Scanning Calorimetry Analysis (DSC) ... 70
4.10 Dynamic Mechanical Analysis (DMA) ... 76
4.11 Field Emission Scanning Electron Microscopy (FESEM) ... 82
4.12 Transmission Electron Microscope (TEM) ... 87
4.13 Flexing Test ... 93
4.14 Summary ... 98
CHAPTER 5: CONCLUSION AND RECOMMENDATION ... 100
5.1 Conclusion ... 100
5.2 Recommendation ... 101
REFERENCES ... 103
LIST OF PUBLICATIONS ... 116
APPENDIX A ... 117
LIST OF TABLES
Table No. Page No.
2.1 Mechanical properties of shoe sole 25
3.1 Composition of HDPE/EPR-CNT nanocomposites. 29 4.1 Thermal properties for HDPE/EPR matrix and
HDPE/EPR–CNT nanocomposite for both unirradiated and irradiated obtained from TGA
4.2 Thermal properties for HDPE/EPR matrix and HDPE/EPR–OMMT nanocomposite for both unirradiated and irradiated obtained from TGA
4.3 DSC results for HDPE/EPR matrix and HDPE/EPR–
CNT nanocomposite for both unirradiated and
4. 4 DSC results for HDPE/EPR matrix and HDPE/EPR–
OMMT nanocomposite for both unirradiated and
4. 5 DMA results for HDPE/EPR matrix and HDPE/EPR–3 wt% CNT nanocomposite for both
unirradiated and irradiated. 76
4. 6 DMA results for HDPE/EPR matrix and HDPE/EPR– OMMT nanocomposite for both
unirradiated and irradiated. 81
4. 7 Result of outer sole flexing test 94
LIST OF FIGURES
Figure No. Page No.
3.1 Mould of outer sole prototype 30
4.1 Tensile strength for unirradiated and irradiated HDPE/EPR–CNT nanocomposites at different
CNT contents. 39
4.2 Tensile strength for unirradiated and irradiated of HDPE/EPR matrix and HDPE/EPR–4 wt%
OMMT nanocomposites. 41
4.3 Tensile modulus for unirradiated and irradiated HDPE/EPR–CNT nanocomposites at different
CNT contents. 43
4.4 Tensile modulus for unirradiated and irradiated of HDPE/EPR matrix and HDPE/EPR–4 wt%
OMMT nanocomposites. 44
4.5 Strain at break for unirradiated and irradiated HDPE/EPR–CNT nanocomposites at different
CNT contents. 45
4.6 Strain at break for unirradiated and irradiated
HDPE/EPR–4 wt% OMMT nanocomposites. 46 4.7 Stress–strain curves of a) unirradiated, and b)
irradiated HDPE/EPR–CNT nanocomposites. 48 4.8 Stress – strain curves of a) unirradiated and b)
irradiated HDPE/EPR–4 wt% OMMT
4.9 Impact strength for unirradiated and irradiated
HDPE/EPR–CNT nanocomposites. 52
4.10 Impact strength for unirradiated and irradiated
HDPE/EPR–4 wt% OMMT nanocomposites. 53 4.11 Hardness value for unirradiated and irradiated
HDPE/EPR–CNT nanocomposites. 54
4.12 Hardness value for unirradiated and irradiated
HDPE/EPR–4 w% OMMT nanocomposites. 55
4.13 Wear rate of unirradiated (UR) and irradiated (R) HDPE/EPR matrix and HDPE/EPR-3 wt% CNT
4.14 Wear rate of a) unirradiated (UR) and b) irradiated (R) HDPE/EPR matrix and
HDPE/EPR–4 wt% OMMT nanocomposite. 58
4.15 The percentage of gel content of HDPE/EPR and HDPE/EPR–CNT at optimum CNT loading (3
4.16 The percentage of gel content of HDPE/EPR and
HDPE/EPR-4 wt% OMMT. 60
4.17 XRD pattern of a) pure CNTs, and b)
HDPE/EPR–3 wt% CNT nanocomposites. 62
4.18 XRD pattern of a) pure OMMT and b)
HDPE/EPR–4 wt% OMMT nanocomposites. 64 4.19 TGA curves of HDPE/EPR matrix and
HDPE/EPR–3 wt% CNT nanocomposite, both
unirradiated (UR) and irradiated (R). 66 4.20 TGA curves of HDPE/EPR matrix and
HDPE/EPR–4 wt% OMMT nanocomposite for
both unirradiated (UR) and irradiated (R). 68 4.21 Melting endotherms of HDPE/EPR matrix and
HDPE/EPR–CNT nanocomposite, both
unirradiated (UR) and irradiated (R). 71 4.22 Melting endothermic reaction of HDPE/EPR
matrix and HDPE/EPR–OMMT nanocomposite
for both unirradiated (UR) and irradiated (R). 75 4.23 Storage modulus of HDPE/EPR matrix and
HDPE/EPR–3 wt% CNT for unirradiated (UR)
and irradiated (R). 77
4.24 Tangent delta as a function of temperature for HDPE/EPR matrix and HDPE/EPR–3 wt% CNT for unirradiated (UR) and irradiated (R)
4.25 Storage modulus of HDPE/EPR matrix and HDPE/EPR–4 wt% OMMT in unirradiated (UR)
and irradiated (R). 80
4.26 Tangent delta as a function of temperature for HDPE/EPR matrix and HDPE/EPR–4 wt%
OMMT for unirirradiated (UR) and irradiated
4.27 Fracture surface of HDPE/EPR matrix at 3000×
magnification: a)unirradiated b) irradiated. 83 4.28 Fracture surface of HDPE/EPR–3 wt% CNT
nanocomposites at 3000× magnification:
a) unirradiated b) irradiated. 84
4.29 Fracture surface of unirradiated HDPE/EPR–4 wt% OMMT nanocomposites a) 1000× and
b) 3000× magnification. 85
4.30 Fracture surface of irradiated HDPE/EPR–4 wt%
OMMT nanocomposites at a) 1000× and
b) 3000× magnification. 86
4.31 TEM image of distribution of CNTs in the ternary nanocomposite at 200 nm: a) unirradiated and b)
irradiated HDPE/EPR–3 wt% CNT
4.32 TEM image distribution of CNTs with outer diameter at 100 nm in the ternary nanocomposite:
a) unirradiated and b) irradiated HDPE/EPR–3
wt% CNT nanocomposites. 90
4.33 TEM image of distribution of OMMT layers in
the ternary nanocomposite at 200nm:
a) unirradiated and b) irradiated HDPE/EPR–4
wt% OMMT nanocomposites. 92
4.34 Fractographic examination of unirradiated
HDPE/EPR matrix 96
4.35 Fractographic examination of irradiated
HDPE/EPR matrix 96
4.36 Fractographic examination of unirradiated
HDPE/EPR–3 wt% CNT nanocomposite 96
4.37 Fractographic examination of irradiated
HDPE/EPR–3 wt% CNT nanocomposite 97
LIST OF ABBREVIATIONS
ASTM American Society for Testing Materials
CNT Carbon Nanotube
DMA Dynamic Mechanical Analysis DSC Differential Scanning Calorimetry
E’ Storage modulus
E’’ Loss modulus
EB Electron beam
e.g (example gratia) as for example EPR Ethylene Propylene Rubber et al. (et alia): and others
etc (et cetera): and so forth EVA Ethylene Vinyl Acetate
FESEM Field Emission Scanning Electron Microscopy
g/min Gram per minute
HDPE High Density Polyethylene
i.e (id est) that is
ISO International Organization for Standardization
J/g Joules per gram
J/m Joules per metre
kg/cm3 Kilo-gram per cubic centimeter kGy/pass Kilo-gray per pass
MeV Megaelectron volt
MFI Melt flow index
ml/min Millilitre per minute
mm/min Millimetre per minute
rpm Revolution per minute
SATRA Shoe and Allied Trade Research Association
xv tan δ Tan delta
TEM Transmission electron microscopy Tf Final decomposition temperature Tg Glass transition temperature TGA Thermogravimetry Analysis Ti Initial decomposition temperature
Tm Melting temperature
wt % Weight percent
Xc Crystalline percentage.
XRD X-ray Diffraction
°/min Degree per minute
°C/min. Celsius per minute
%X Percentage of crystallinity
ΔH Enthalphy of fusion
CHAPTER 1 INTRODUCTION
The selection of a sport shoe emphasizes a few criteria such as light weight, flexibility, and adequate grip, as these features offer comfort to athletes and also improve their performances in their sports fields. The use of suitable material for the shoe, especially the sole, definitely provides benefits to the athlete in terms of satisfaction, health, and ergonomic and biomechanical factors during training. The performance of athletes is related to the selection of sport shoes whereby the properties of the shoe sole have a tremendous effect on comfort during walking, running, and jumping.
A material that is often chosen as a shoe sole is polymer. The main reason is because of its elasticity and flexibility. For a sport shoe sole, standard actions such as compression and bending during activities demand an elastic material that can deform up to a certain limit and is recoverable. Elastic and flexible behaviours can also help the shoe sole resist aggressive movement, especially jumping. During jumping, the whole body weight is carried by the shoe, mostly when the shoe hits the ground.
Therefore, elasticity and flexibility of the material are essential to preserve the shape and structure of the shoe in the long term as well as to provide comfort through the cushioning properties of the sole.
Apart from that, the main concern in the development of a sport shoe sole is shock absorption (Shariatmadari et al., 2012; Shih et al., 2011; Silva et al., 2009).
Shock absorption is one of the most significant properties of comfort that can prevent injury, particularly during the impact with the ground. Moreover, a lightweight characteristic is necessary during lifting of the foot when the shoe needs to move against gravity. The heavier the shoe sole, the more difficulties may be faced during lifting. Therefore, a lightweight shoe sole can relieve the pressure on the foot during activities.
In addition, many researchers have aimed to improve shoe soles by using polyurethane (PU) foam and ethylene vinyl acetate (EVA) foam (Silva et al., 2009;
Verdejo and Mills, 2004a, 2004b). According to Silva et al. (2009), polymers, especially cellular materials such as foams, ethyl-vinyl-acetate, and polyurethane, are commonly selected as shoe sole material due to their good cushioning properties. On the other hand, there are many aspects to be considered in the development of a shoe sole. Some of them are the material and its properties, biomechanical and ergonomic factors. Nonetheless, for the fundamental stage, the right selection of material can have a remarkable effect on the properties of the entire sport shoe.
Cellular material is often used as sole material hence advantageously to propose new material for shoe sole from nanocomposite. In addition, there is no interest from other industries has been reported in nanocomposite shoe soles thus it has become new development in sport shoe applications. Therefore, this research aims to fabricate a new crosslinked nanocomposite based on high density polyethylene (HDPE)/ethylene propylene rubber (EPR)-filled montmorillonite for the shoe insole and carbon nanotubes (CNTs) for the shoe outer sole.
1.2 PROBLEM STATEMENT AND SIGNIFICANCE
EVA and PU are generally used as shoe soles due to their mechanical properties.
According to Brückner et al. (2010), in damping tests, EVA has shown average results in terms of damping properties in short-term tests compared to PU that shown better results in long-term testing. EVA showed low durability and ageing resistance and as for the outer sole, EVA shows a decaying problem which shortens the lifetime of the shoes. Silva et al. (2009) also stated that PU and EVA are commonly used as shoe soles but they have limitations in terms of being poor in tear strength, abrasion compliance, and gradual deformation. Since then, these issues have given rise to some possible approaches to developing new materials for shoe soles by mixing polymer and rubber as the base material. Nanofillers are then added to this polymer blend as the reinforcement for the development of shoe soles from nanocomposite materials.
During this decade, nanocomposites have received huge interest from over a thousand researchers due to their outstanding properties and uses in a wide range of applications. Generally, nanocomposites have been applied in aerospace structures, sporting goods, automotive components, optical barriers, conducting plastics, and electro-magnetics (Bhuiyanet al., 2013a). Interestingly, nanocomposite shoe soles have become a new development in sport shoe applications, while no interest has been reported from other researchers (Verdejo and Mills, 2004a, 2004b). Additionally, the most extraordinary about nanocomposites is that they offer tremendous effect by adding a very small amount of nanofiller yet maintain their properties. Thus nanocomposite surprisingly provide better properties than the polymer matrix alone (Valentino et al., 2008).
Therefore an alternative way of replacing EVA or PU as the shoe sole is by developing a nanocomposite of HDPE-EPR with OMMT (insole) and CNT (outer
sole) nanofillers. Blend HDPE and EPR have been chosen as the material for polymer based matrix of shoe sole, OMMT and CNT as nanofiller for insole and outer sole respectively. The presence of these nanofillers also requires the nanocomposite to be crosslinked by physical crosslinking (electron beam radiation), improving the mutual interface between HDPE, EPR, and nanofiller (CNT and OMMT) and dispersing both nanofillers well. It is also expected that HDPE/EPR nanocomposites may solve problems related to stiffness and damping characteristics via the use of tailor-made developed material.
1.3 RESEARCH OBJECTIVES
1) To fabricate a new crosslinked nanocomposite based on high density polyethylene (HDPE)/ethylene propylene rubber (EPR)-filled nanoclay for the insole and filled CNT for the outer sole.
2) To determine the effect of nanofillers content (carbon nanotube and organomontmorillonite) and electron beam (EB) irradiation on the mechanical properties, thermal properties and morphology of HDPE/EPR nanocomposites.
3) To investigate the flexibility of prototype developed of the outer shoe sole (HDPE/EPR-CNT).
1.4 SCOPE OF RESEARCH
In this research work, HDPE/EPR–OMMT and HDPE/EPR–CNT nanocomposites have been developed via the single melt blending method. Before the nanocomposites were fabricated, preliminary work was done in order to select the best ratio of
HDPE/EPR. Three different ratios of HDPE to EPR were selected: 70:30, 50:50, and 30:70, and these ratios were evaluated through mechanical testing. The CNT content in the HDPE/EPR–CNT nanocomposites was varied between 0.5, 1, 3, and 5 wt% to determine the optimum CNT content for shoe outer sole applications. Nevertheless, based on Jamal et al. (2011c), in this study, 4 wt% of OMMT was maintained throughout the research. All the samples were mixed using an internal mixer and compression moulded according to the ASTM standard. The samples were exposed to EB radiation at a 100 kGy/s dose before the characterization of the nanocomposites was carried out. The nanocomposites underwent characterization by mechanical testing (to study the tensile strength and tensile modulus, impact strength, hardness, and flexural strength), thermal analysis (to determine the weight loss of the materials, to measure the energy absorbed by the materials, and to measure changes in the viscoelastic response of the material), morphological examination (to observe the morphology of nanocomposite fractures), and other related tests such as X-ray diffraction (XRD) analysis and gel fraction test. The optimum CNT content was then selected for the development of the outer sole prototype of HDPE/EPR-CNT nanocomposite. The prototype was also developed through single melt blending, compression moulded into the outer sole shape, and exposed to EB radiation at the same radiation dose. Outer sole flexing tests were conducted in order to study the flexibility of the outer sole of HDPE/EPR–CNT nanocomposite.
1.5 THESIS ORGANIZATION
This research work is organized into five main parts, presented in Chapter 1, Chapter 2, Chapter 3, Chapter 4 and Chapter 5. The introduction and background of the
research done are briefly discussed in Chapter 1. This includes a brief description of nanocomposite materials used as shoe soles as well as the advantages of irradiating the materials. The characteristics of nanofillers employed in the nanocomposites are also generally explained. The history of nanocomposites as well as the future and bright prospects of nanocomposite systems are concisely explained in the introduction part.
The reason for developing shoe soles from nanocomposites is discussed under the problem statement. Suggestions and ideas about how to overcome such problems are also stated in this part. In addition, the aims of developing nanocomposites have been concisely stated under the research objectives. Under the scope of the research topic, the background regarding nanocomposites systems has been briefly discussed.
In addition, the raw materials used and type of processing as well as parameters involved are also explained in this part.
The theoretical background of the polymer matrix composite, nanofillers, surface modification technique, shoe soles, and their advantages are discussed in the literature review in Chapter 2. In this chapter, each concept mentioned above is explained in detail.
The experimental method is elaborated in detail along with the presence of flow charts and figures for better understanding in Chapter 3. In this chapter, the types of materials used, processing parameters (temperature, time, and speed), HDPE/EPR matrix, CNT–filled HDPE/EPR, and OMMT–filled HDPE/EPR treatments comprising the application of the EB radiation technique as well as characterization methods to evaluate the properties of the nanocomposite systems are concisely explained. In addition, the theory and concepts regarding the methods of characterization are briefly listed.
Chapter 4 comprise the mechanical, thermal, and other testing methods used to assess the properties of the nanocomposites produced. Chapter 4 discusses on the effect of two nanofillers used to fill the HDPE/EPR matrix; CNT and OMMT.
Different sources of references used are presented to support the results obtained from these characterization methods. The results acquired from different techniques of characterization are then compared between unirradiated and irradiated systems. The optimum system is then determined based on the results obtained. The concluding remarks of the whole research work and recommendations for future works are described in the last chapter, Chapter 5.
Works of other researchers referred to are ordered in the bibliography section.
Following the complete compilation of all the data needed, a clean and concise abstract is presented at the beginning of the thesis. Brief information on the problem statement, research methodology, and the results attained are part of the main topic discussed in this section so that an overview of the study can be comprehended.
The development of high performance lightweight nanocomposite sport shoes application becomes new in the world of polymeric material. In the present work, polymer blend of high density polyethylene (HDPE) and ethylene propylene rubber (EPR) are used to produce ternary composites containing nanofillers of carbon nanotube (CNT) and organophilic-montmorillonite (OMMT) for outer sole and insole application, respectively. These combinations of different materials background distinguish the effectiveness of polymer blends and filler mixtures over polymer composite composed of single polymers and macro or micro fillers. In order to develop nanocomposite system with enhanced properties, structural characteristic of filler used is a concern. To obtain such characteristics, the right selection of polymer matrix and nanocomposites treatments plays an important role.
2.2 BACKGROUND OF MATERIALS USED
2.2.1 High Density Polyethylene (HDPE) Background
High density polyethylene is a thermoplastic polymer that derived from polyethylene group. This polyethylene with an average density between 0.941 and 0.965 g/cm3 group can be reshaped and recycled. HDPE is a material composed of carbon and hydrogen atoms joined together forming high molecular weight products that consist
of 500,000 – 1000,000 carbon units long. The mechanical and chemical properties of HDPE can be determined by the molecular weight and number of atoms. The longer the main chain indicates the greater the molecular weight and number of atoms. HDPE is the most important commercial polyolefins having a semi crystalline polymeric material that consist of both crystalline and amorphous regions (Sajwan et al., 2008) as a result HDPE has a very high strength (Park et al., 2009). Besides of exhibiting hard and more opaque characteristics, HDPE is reported able to endure high temperatures as high as 130 °C (Alothman, 2012; Stelescu et al., 2013).
Many researchers such as Pöllänen et al. (2013), Ayswarya et al. (2012) and Mir et al.
(2011) reported that HDPE is often used in building, automotive, household appliances, packaging industries (Dougnac et al., 2010; Puig et al., 2010) and aerospace industries as they are able to replace the use of conventional materials such as metals in an application. According to Pöllänen et al. (2013), HDPE have greater tensile modulus and strength that are suitable for most application that deals with stress. In addition, other properties exhibit by HDPE such as better mechanical and thermal properties, the availability, good process ability, high chemical resistance, waterproof and low cost (Guerreiro et al., 2012; Hwang et al., 2012). Other authors also added that HDPE has excellent low temperature toughness, chemical resistance, good dielectric properties and relatively high softening temperature (Ayswarya et al., 2012). These criteria of HDPE have made HDPE as the candidate of matrix material in a composite (Pöllänen et al., 2013).