UNIVERSITI TEKNOLOGI MARA
MECHANICAL AND WEAR PROPERTIES OF
FUNCTIONALISED
CARBON NANOTUBES MODIFIED KENAF COMPOSITES
NAPISAH BINTI SAPIAI
Thesis submitted in fulfillment of the requirements for the degree of
Doctor of Philosophy
Faculty of Mechanical Engineering
November 2017
ABSTRACT
Natural fibres reinforced polymer composites have been gaining great attention in several applications due to its eco-friendly nature, sustainability, stronger and cost effective. Among all natural fibres available, kenaf fibre has been identified as an attractive option for reinforcing fibres due to its availability, high aspect ratio and superior toughness properties. However, limitation arise with respect to the mechanical properties when kenaf fibres and epoxy resin are used. The combination of these materials has been reported to have poor-matrix interfacial addition due to hydrophilic kenaf fibres and hydrophobic epoxy resin in nature. In addition, majority of epoxy systems are degraded by their brittleness property, low impact strength and low fracture toughness. The objective of this study is to improve the properties of the kenaf fibres reinforced composites by incorporating carbon nanotubes (CNT) in epoxy matrix and hybridised with glass fibres. Moreover, the study was focused on the functionalisation of CNT surface via concentrated acid and amino silane. This surface modification aims to enhance the dispersibility of CNT into epoxy matrix and improve the interfacial adhesion bonding between three phases (CNT/epoxy/kenaf fibres) composites. In this study, the modified epoxy with 0.5, 0.75 and 1.0 wt% pristine CNT (PCNT)/ acid treated (ACNT)/silane treated (SCNT) was impregnated with kenaf fibres to fabricate the kenaf fibres reinforced composites system. The woven glass fibres (G) plies were placed at top and underneath kenaf fibres (K) in fabrication of hybrid G/K fibres composites system. The effect of CNT addition and functionalised CNT on the longitudinal and transverse tensile, flexural, compressive, impact and wear properties of kenaf and hybrid G/K composites were studied. Several types of analytical methods such as X-Ray Diffractometer (XRD), Transmission Electron Microscopy (TEM), Fourier Transforms Infrared Spectroscopy (FTIR) and Scanning Electron Spectroscopy (SEM) were used to examine these composites. FTIR tests showed the presence of Si- 0 and Si-OH functional groups on silane treated CNT surface at peak 803 and 1070 cm"
', respectively. This results in improved dispersion and interfacial bonding between CNT and epoxy resin as shown in TEM and SEM micrographs. The inclusion of SCNT improved the mechanical properties of kenaf and hybrid glass/kenaf composites. The maximum improvements were achieved at 1.0 wt% of SCNT loading. For example, the
l.OSCNT-modified kenaf composites were improved about 43.39% for longitudinal tensile strength, 28.2% for transverse tensile strength, 21.1% for flexural strength, 20.15% compressive strength and 130.6 % for impact strength when compared to kenaf composite. In addition, the 1 .OSCNT-modified hybrid glass/kenaf composites were improved about 48.78% for longitudinal tensile strength, 19.36% for transverse tensile strength, 11.36% for flexural strength, 7.73% compressive strength and 24.45% for impact strength when compared to hybrid G/K composite. However, the inclusion of SCNT did not improve the wear properties due to rougher worn debris produced that induced the three-body abrasive wear effect, thus increased the wear rates of the kenaf composites. When hybridised with glass fibres, the kenaf composites showed improvement of 40.0% for longitudinal tensile strength, 86.9 % for transverse tensile strength, 155% for impact strength and 49.1% for flexural strength. In contrast, there is insignificant improvement in compressive and wear properties due the premature failure of the specimens when subjected to compressive load and glass fibres were easily pulverised when exposed to abrasive roller.
IV
ACKNOWLEDGEMENT
In the name of Almighty Allah, The Most Beneficent, The Most Merciful Alhamdulilah, all praises to Allah for the strengths and his blessing in completing this thesis. I would like to thank my supervisor, Assoc. Prof. Dr Aidah Jumahat, who has provided invaluable guidance, encouragement and direction throughout this study.
Without her guidance, understanding and persistent support, this PhD thesis would not have been possible. I would also like to thank my co-supervisor, Assoc. Prof. Dr Jamaluddin Mahmud for his support and encouragement extended to me.
I am gratefully acknowledged the Faculty of Mechanical Engineering, UiTM Shah Alam for providing facilities to carry out this project. I wish to thank all the staff for their help and support especially Dr Muhamad Hussien, Mr Naziman, Mr Mohamad Suhairi, Mr Mohd Fami, Mr Norazman, Mr Azerif, Mr Pazali, Mr Mohd Rahimi, Mr Harysham and Mr Nor Azizi. I also would like to thank Mr Hizwan from faculty of Dentistry for his helps in performing scanning electron microscopy.
I am eternally grateful to my family members, especially my father Sapiai Semail, my mother Siti Asiah Abdullah and my siblings whose always love and support me through every obstacle that appeared in my study and pray for my success in life and hereafter.
My sincere gratitude should also be accorded to my friends Norazean Md Noh, Eliya Farah Hana Mohd Kamal, Anis Adillah Abu Talib, Najiy Rizal Surani Rizal, Ummu Raihanah Hashim, Norhasyidah Manap, Faris Syafiq, Mazyan Yahya, Mahfuzah Zainudin, Norshamimi Md Noh, Syam Sazani, Syafiqahdahiyah Ramlan, Noor Leha Abdul Rahman, Hamisah Ismail, Syahriza Ismail, Mustapha Ali Azhar and to all people who did not mansions here for moral support, assistance and inspiration during my research period.
I am very indebted to every individual that helped me throughout this PhD journey. I really appreciate whatever help I have received through it all. Thank you.
Last but not least, my appreciation also extends to my sponsor, MyBrain 15 programme under Ministry of Higher Education (MOHE) and FRGS grant for funding this study.
TABLE OF CONTENT
Page
CONFIRMATION BY PANEL OF EXAMINERS ii
AUTHOR'S DECLARATION iii
ABSTRACT iv ACKNOWLEDGEMENT v
TABLE OF CONTENT vi LIST OF TABLES xii LIST OF FIGURES xvi LIST OF PLATES xxvi LIST OF SYMBOLS xxviii LIST OF ABBREVIATIONS xxx
CHAPTER ONE : INTRODUCTION 1
1.1 Research Background 1 1.2 Problem Statement 3
1.3 Objectives 4 1.4 Scope of Work 4 1.5 Significance of Study 5 1.6 Structure of Thesis 6
CHAPTER TWO : LITERATURE REVIEW 7
2.1 Kenaf Fibres as A Reinforcement 7 2.1.1 Introduction to Natural Fibres 7
2.1.2 Kenaf Fibres 10 2.2 Epoxy as A Polymer Matrix 12
2.2.1 Introduction to Matrix 12
2.2.2 Epoxy Resin 13 2.3 Carbon Nanotubes as A Nanofiller 14
2.3.1 Introduction to Nanofillers 14 2.3.2 Carbon nanotubes (CNT) 15
vi
2.3.2.1 Introduction to Carbon Nanotubes 15 2.3.2.2 Properties of Carbon Nanotubes 18 2.3.2.3 Surface Modification of Carbon Nanotubes (CNT) 18
2.4 Natural Fibres Reinforced Polymer 24 2.4.1 Properties of Natural Fibres Reinforced Polymer Composites 24
2.4.1.1 Mechanical Properties 24 2.4.1.2 Wear Properties 30 2.4.2 Natural Fibres in Industrial Commercialization 33
2.5 Improving The Properties of Natural Fibres Reinforced Polymer
Composites 36 2.5.1 Orientation and Arrangement of the fibres 36
2.5.2 Enhancing the Matrix by Addition of Nanofiller 39
2.5.3 Hybridisation 45 2.6 Concluding Remarks 47
CHAPTER THREE : RESEARCH METHODOLOGY 50
3.1 Introduction 50 3.2 Materials 51
3.2.1 Epoxy 51 3.2.2 Kenaf Fibres 51 3.2.3 Glass Fibres 52 3.2.4 Multi-walled Carbon Nanotubes (MWCNTs) 53
3.2.5 Nitric Acid (HN03) 54
3.2.6 Sulfuric Acid (H2SO4) 54
3.2.7 Distilled Water 55 3.2.8 3-Aminopropyl Triethoxysilane (3AMPTES) 55
3.2.9 Ethanol 56 3.3 Fabrication of Composites Laminates 56
3.3.1 Kenaf (K) and Hybrid G/K Composites 58
3.3.1.1 Winding of kenaf fibres 58 3.3.1.2 Resin Impregnation 58 3.3.1.3 Post Curing Process 60
