UNIVERSITI TEKNIKAL MALAYSIA MELAKA A STUDY OF MECHANICAL PROPERTIES IN RELATION WITH MORPHOLOGICAL STRUCTURE OF PP/KENAF FIBER REINFORCED PLASTIC COMPOSITE This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering (Materials Engineering) with Honours. by NOOR SYAFIQ BIN SHAARI FACULTY OF MANUFACTURING ENGINEERING 2009
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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
A STUDY OF MECHANICAL PROPERTIES IN RELATION WITH
MORPHOLOGICAL STRUCTURE OF PP/KENAF FIBER
REINFORCED PLASTIC COMPOSITE
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Materials Engineering) with Honours.
by
NOOR SYAFIQ BIN SHAARI
FACULTY OF MANUFACTURING ENGINEERING
2009
i
ABSTRACT
This research aims to study and analyze the effects of different fiber loading and
coupling agent addition on the mechanical properties and its relationship to the micro
structural behavior of the kenaf fiber reinforced polypropylene composites. The main
raw materials used in this project are polypropylene (PP) resin as matrix materials and
kenaf fiber as reinforcement materials for the composite fabrication. Typically, the
observed size of kenaf fibers used in this study is around 513.39µm. The composite
panels were fabricated by using an internal mixer and compression molding machine
and were then cut into the specific dimension according to the specific ASTM standard
of testing. The specimens primarily were tested for the Critical Properties Analysis -
Tensile Test. The best compounding formulation of composite was found at the weight
percentage (wt%) of 60wt% of PP matrix and 40wt% of the kenaf fibers. Further
analyses for various mechanical properties of the composite were done accordingly to
all composites formulation. The microstructures of tested specimens fracture surface
were observed as to understand the fracture behavior, the fiber distribution and the
surface morphology and its significant correlation to the mechanical properties studied.
The results showed that the increasing of fiber loading had significantly increased the
mechanical properties of the fabricated composite. The introduction of 3wt% of
polypropylene-graft-maleic anhydride (MAPP) was done to the best formulated
composites which indicate the improvement of the interfacial adhesion between the
fiber-matrix interphase through the morphology observed and also improvement in the
properties studied especially in water absorption behavior. Through the study, the
enhancement of fabricated composite could be applied to the structural engineering
applications through the advantage of the mechanical properties performance of tensile,
flexural and impact properties.
ii
ABSTRAK
Matlamat penulisan kertas kerja ini adalah untuk mengkaji dan menganalisis kesan
penambahan gentian dan agen perangkai serta hubungan struktur mikro pada sifat
mekanik komposit gentian kenaf yang diperkuatkan dengan polipropilena. Bahan utama
yang digunakan di dalam kajian ini adalah resin polipropilena (PP) sebagai bahan matrik
dan gentian kenaf sebagai bahan penenulangan komposit. Saiz gentian kenaf yang
digunakan dalam kajian ini adalah dalam lingkungan 513.39µm. Kepingan komposit
dibentuk dengan menggunakan mesin pencampuran dalaman serta mesin pemampat dan
kemudiannya dipotong mengikut spesifikasi tertentu berdasarkan piawaian ujian ASTM.
Pada permulaannya, spesimen-spesimen diuji pada Analisa Sifat Kritikal iaitu ujian
tegangan. Formula sebatian terbaik komposit didapati pada peratusan berat (wt%)
dengan 60wt% matrik PP dan 40wt% gentian kenaf. Analisa lanjutan pelbagai sifat
mekanik komposit diteruskan terhadap semua formula sebatian. Struktur mikro pada
permukaan spesimen yang telah retak dikaji dalam memahami sifat rekahan, taburan
gentian dan morfologi permukaan serta hubungannya terhadap kajian sifat mekanik.
Keputusan menunjukkan bahawa dengan peningkatan pertambahan gentian telah
meningkatkan sifat-sifat mekanik komposit. Pengenalan polypropylene-graft-maleic
anhydride, (MAPP) dilakukan terhadap formula sebatian terbaik komposit yang
menunjukkan penambahbaikan terhadap lekatan antara muka di antara matrik-gentian
melalui pemerhatian morfologi dan juga peningkatan sifat mekanik komposit
terutamanya sifat penyerapan air. Melalui kajian ini juga, penambahbaikan terhadap
sifat mekanik komposit diharap dapat diaplikasikan dengan penggunaan di dalam
industri melalui kelebihan pencapaian dalam sifat tegangan, sifat lenturan dan sifat
hentaman komposit.
iii
DEDICATION
For my beloved family and friends
iv
ACKNOWLEDGEMENT
I would like to convey my thanks to the all person who had contributed in ensuring a
successful occurrence throughout the duration of my final year project (PSM I). I also
gratefully acknowledge to my ex-supervisor, Mrs. Zurina binti Shamsudin, my
supervisor Mr. Jefferie bin Abd Razak and my previous and my current examiners Mr.
Edeerozey bin Abd. Manaf and Associated Professor Dr Thangaraj Joseph Sahaya
Anand for their encouragement, fully support, by providing me enormous guidance and
idea for my research project. Without them all, this project may not valuable. Their
knowledge and experience has fully inspired, motivated and drive me to complete my
final year project successfully. Also, my special thanks to Mr. Hairulhisham bin Rosnan,
for your time and co-operation completing my research project. Subsequently to Mohd
Azhar Bin Abu Shah and all technicians involved to complete this project. To all my
peers, especially those who are undergoing final year in Degree programs, thanks for
your all kindness of delivering ideas and motivation that necessary for me to complete
this study. Besides those mentioned, I also would like to express my gratitude with
highly appreciation and dedication to my family because without them, I won’t be here
to complete my study in Universiti Teknikal Malaysia, Melaka.
v
TABLE OF CONTENTS
Abstract i
Abstrak ii
Dedication iii
Acknowledgement iv
Table of Contents v
List of Tables ix
List of Figures x
List of Abbreviations, Symbols, Specialized Nomenclature xiv
1. INTRODUCTION 1
1.1 Background of study 1
1.2 Problem Statements 3
1.3 Objectives 4
1.4 Hypotheses 5
1.5 Scope of study 5
2. LITERATURE REVIEW 7
2.1 Introduction 7
2.2 Composite 7
2.2.1 Introduction to Composite 7
2.2.2 Polymer Matrix Composite (PMC) 9
2.3 Matrix 10
2.3.1 Polypropylene (PP) as Matrix Material 11
2.4 Reinforcement 12
2.4.1 Natural fiber 13
2.4.1.1 Kenaf fiber 15
2.5 Processing of composites 18
2.6 Rules of Mixture (RoM) 19
vi
2.6.1 Elastic Modulus 19
2.6.2 Density 20
2.7 Fiber loading 21
2.8 Tensile and flexural properties 22
2.9 Impact properties 24
2.10 Water absorption 25
2.11 Coupling Agent 27
2.12 Morphological study 31
3. METHODOLOGY 33
3.1 Introduction 33
3.2 Materials 34
3.2.1 Polypropylene (PP) 34
3.2.2 Kenaf short fiber (core) 36
3.2.3 Coupling agents 37
3.3 Raw materials preparation 38
3.3.1 Crushing 38
3.3.2 Kenaf fiber drying process 38
3.4 Characterization of kenaf short fiber 39
3.4.1 Density measurement 39
3.4.2 Water absorption 40
3.4.3 Drying profile study 40
3.4.4 Microscopy study 40
3.5 Sample fabrication 41
3.5.1 Compounding of PP/kenaf composite 41
3.5.2 Introduction of Coupling Agent 43
3.5.3 Hot and cold compression molding 43
3.6 Mechanical testing 44
3.6.1 Critical Properties Analysis – Tensile Test 44
3.6.2 Flexural Test 45
3.6.3 Izod Pendulum Impact Test 46
vii
3.6.4 Water Absorption Test 47
3.6.5 Thickness Swelling Test 47
3.6.6 Morphological study 48
4. RESULTS 49
4.1 Introduction 49
4.2 Characterization 49
4.2.1 Fiber size 49
4.2.2 Density 50
4.2.3 Drying study 51
4.3 Observation of Sample Preparation Process 52
4.4 Critical Property Analysis - Tensile Test 53
4.4.1 Fracture Surface Morphology of Tensile Specimen 55
4.5 Flexural Test 59
4.5.1 Bending Surface Morphology of Flexural Specimen 61
4.6 Impact Test 65
4.6.1 Fracture Surface Morphology of Impact Specimen 67
4.7 Water Absorption Testing 70
4.8 Thickness Swelling Testing 72
5. DISCUSSION 75
5.1 Introduction 75
5.2 Tensile Properties 75
5.3 Flexural Properties 82
5.4 Impact Properties 87
5.5 Water Absorption and Thickness Swelling Behavior 90
6. CONCLUSION AND RECOMMENDATION 92
6.1 Conclusion 92
6.2 Recommendation 94
viii
REFERENCES 95
APPENDIX
A Gantt chart for PSM I 100
B Gantt chart for PSM II 101
C Micrograph of Kenaf Fibers size 102
D Data of Kenaf Fiber Size Analysis 103
E Sample designation by weight percentage (wt %) 104
ix
LIST OF TABLES
2.1 Comparison of Thermoplastics and Thermosets polymer 12
2.2 Comparison of Properties of Kenaf-Filled PP with typical
commercially filled PP composites 13
2.3 Comparison between natural fiber and synthetic fiber 14
2.4 Scientific classification of kenaf plant 16
2.5 Chemical composition in Kenaf fiber 17
2.6 Results on mechanical test on various PP/kenaf composite blends 30
3.1 Physical properties of the polypropylene (PP) 36
3.2 Technical properties of Polypropylene-graft-maleic anhydride (MAPP) 37
4.1 Measurement of kenaf fiber density 51
4.2 Total of weight loss of kenaf short fiber of the drying process 51
4.3 Tensile properties of pure PP and PP/kenaf fiber composite with
the absence and presence of MAPP 54
4.4 Flexural properties of pure PP and PP/kenaf fiber composite with
the absence and presence of MAPP 60
4.5 Impact properties of pure PP and PP/kenaf fiber composite with
the absence and presence of MAPP 66
4.6 Weight deflection and Percentage of weight gain of specimens
at the different composition of kenaf fiber addition 71
4.7 Thickness deflection and Percentage of thickness swelling of specimens
at the different composition of kenaf fiber addition 73
x
LIST OF FIGURES
2.1 A classification scheme for the various composites types 8
2.2 Molecular structure of PP 11
2.3 Parts of Kenaf Plant 15
2.4 Configuration of kenaf fiber 17
2.5 Stress-strain curves of the kenaf sheet, the PLLA film and the
PLLA/kenaf composite 22
2.6 Relationship between tensile properties and fiber content 23
2.7 Relationship between flexural properties and fiber content 23
2.8 Effect of the amount kenaf versus the notched and un-notched
Izod impact strength of PP/kenaf coupled composites with 2% of
weight of coupling agent 25
2.9 Water absorption of natural and glass fiber composites (untreated) 26
2.10 Water absorption of natural fiber composites (treated) 26
2.11 Hypothetical reaction of silanol and the fiber 28
2.12 Proposed reaction mechanism for compatibilization 28
2.13 Stress-strain curves of typical kenaf filled coupled composites with 2%
of weight of coupling agent 29
2.14 Reaction steps in silane grafting of bio fiber surface 30
2.15A SEM micrographs of kenaf fiber surface in composites 100µm
(at 200x) 31
2.15B SEM micrographs of kenaf fiber surface in composites 10µm
(at 500x) 31
2.16a SEM micrographs of the tensile fracture surface of PP/kenaf (20%)
without MAPP 32
2.16b SEM micrographs of the tensile fracture surface of PP/kenaf (20%)
with MAPP 32
2.17a SEM micrograph of an untreated kenaf fiber 32
2.17b SEM micrograph of 3% NaOH treated kenaf fiber 32