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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


4.5 Impact properties of pure PP and PP/kenaf fiber composite with


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

xi

3.1 Polypropylene Pellets 34

3.2 Flow chart of methodology 35

3.3 Kenaf fibers 36

3.4 Polypropylene-graft-maleic anhydride (MAPP) 37

3.5 Rotor mill machine 38

3.6 Dried kenaf fiber 39

3.7 Electronic Densimeter MD-300S 39

3.8 Scanning Electron Microscopy SEM EVO 50 41

3.9 Internal mixer HAAKE Rheomix OS 42

3.10 Hot Press machine G0-7014-A30 43

3.11 Universal Testing Machine UTM 44

3.12 Flexural Testing at three-point bending process 45

3.13 Standard test configuration of flexural test 46

3.14 Standard test configuration of Impact Test 46

3.15 Specimens mounted on the SEM stubs 48

4.1 Morphology of the kenaf fibers 50

4.2 Total weight loss of the kenaf short fiber in gram (g) of the drying process 52

4.3 Tensile Strength of the PP/Kenaf/MAPP composite

at different composition 54

4.4 Tensile Modulus of the PP/Kenaf/MAPP composite at different

composition 55

4.5 The SEM image of the fractured surface of pure PP at the 1000x

of magnification 56

4.6 The SEM image of the fractured surface of PP/kenaf composite with

10wt% of kenaf addition at the 1000x of magnification 57





xii




40wt% of kenaf addition and 3wt% of MAPP at the 1000x

of magnification 59

4.11 Flexural Strength of the PP/Kenaf/MAPP composite at different

composition 60

4.12 Flexural Modulus of the PP/Kenaf/MAPP composite at different

composition 61

4.13 The SEM image of the bending surface for pure PP at the 3000x

of magnification 62

4.14 The SEM image of the bending surface for PP/kenaf composite with

10wt% of kenaf fiber addition at the 1000x of magnification 63








40wt% of kenaf fiber and 3wt% of MAPP at the 500x of magnification 65

4.19 Impact Strength of the PP/Kenaf/MAPP composite at different

composition 66

4.20 The SEM image of the fractured surface for pure PP at the 1000x

of magnification 67

4.21 The SEM image of the fractured surface for PP/kenaf composite with






xiii




40wt% of kenaf fiber addition and 3wt% of MAPP at the 350x

of magnification 70

4.26 Percentages of weight gain at the ambient temperature after 24 hours

immersion for different specimen composition 72

4.27 Percentages of thickness swelling at the ambient temperature after

24 hours immersion for different specimen composition 74

5.1 SEM morphology of the PP/Kenaf reinforced composite with

the introduction of 3wt% of MAPP 78

5.2 Tensile Properties and Morphological Behavior (1000 X Magnification)

of the pure PP and PP/Kenaf composites 79

5.3 Tensile Properties and Morphological Behavior (1000 X Magnification)

of the PP/Kenaf/MAPP composites 81

5.4 SEM Fractured Surface for PP/Kenaf reinforced composite with

40wt% of kenaf fiber 82

5.5 Flexural Properties and Morphological Behavior (1000 X Magnification)

of the pure PP and PP/Kenaf/MAPP composites 85

5.6 Flexural Properties and Morphological Behavior (1000 X Magnification)


5.7 Impact Strength and Morphological Behavior (1000 X Magnification)

of the pure PP and PP/Kenaf/MAPP composites 88

5.8 Impact Strength and Morphological Behavior (1000 X Magnification)


xiv

LIST OF ABBREVIATIONS, SYMBOLS, SPECIALIZED

NOMENCLATURE

200x - 200 times magnification

% - Percent 0C - Degrees Celsius

Ρ - Density

σ/ρ - Tensile Strength per unit mass (specific strength)

E/ρ - Tensile Modulus per unit mass (specific modulus)

-OH - Hydroxyl

AMPTES - 3-aminopropyl-triethoxysilane

APS - 3-aminopropyl-triethoxysilane

ASTM - American Society for Testing and Materials

CCC - Carbon-Carbon Composite

CMC - Ceramic-Matrix Composite

EcL - Longitudinal Young Modulus of Composite

EcT - Transverse Young Modulus of Composite

eg. - Example

et al. - and others

etc. - Et cetera

FRP - Fiber-reinforced plastics

g/cm3 - Gram per Centimeter Cube

GPa - Giga Pascal

i.e., - That is

J - Joule

Kw - Kilowatt

(M) - Malaysia

MAPP - Maleic-Anhydride Grafted Polypropylene

MAPP - Polypropylene-graft-maleic anhydride

xv

min - Minutes

mm - Milimeter

mm/min - Milimeter per minute

µm - Micrometer

MMC - Metal-Matrix Composite

MPa - Mega Pascal

N - Newton

NF - Natural Fiber

N/mm2 - Newton millimeter square

NaOH - Sodium Hydroxide

OH - Hydroxyl

PE - Polyethylene

PLLA - Poly-L-lactic acid

PMC - Polymer Matrix Composite

PP - Polypropylene

PP/kenaf - Kenaf Fiber Reinforced Polypropylene Composite

PS - Polystyrene

RoM - Rules of Mixtures

rpm - Revolution per minute

SEM - Scanning Electron Microscope

UTM - Universal Testing Machine

UV - ultraviolet

wt% - Percent of weight fraction

1

CHAPTER 1 INTRODUCTION

1.1 Background of Study

Recently, the used of fiber-reinforced plastics (FRP) composite becomes famous in

manufacturing industry. The primary advantages of using fiber as filler/reinforcement in

plastics are low densities, non abrasive high filling levels possible resulting in high

stiffness properties, high specific properties, easily recyclable, the fibers will not

fractured when processing over sharp curvatures, biodegradable, low energy

consumption and low cost of production (Kahraman et al., 2005). Throughout its

performance, FRP composites play a vital role in consumer needs or products that

exhibits high level of mechanical properties. The main purpose of using the FRP

composites is to improve the mechanical properties of existing polymeric materials. The

FRP composite can be defined as a material consists of polymer such as Polypropylene

(PP), Polyethylene (PE), Polystyrene (PS) and etc. as matrix and fiber as reinforcement.

Each matrix or reinforcement type can be distinct because of its physical or mechanical

properties, materials form and chemical composition.

Products in a monolithic material are widely used in a daily life such as bottle, food

packaging, vehicles, piping, electronic and etc. These examples of plastics product were

specifically produced by using PP, PE, and PS. However, the manipulation of

monolithic polymer materials as daily life products are not exhibits the high

performances especially in vehicles and electronics application. High impact resistance

is necessary for vehicles and high melting temperature is needed for electronic part

2

(Paul et al., 2008). Melting temperature for PP which is 175ºC has proved that it is not

suitable to be used in electronic and engine vehicles which commonly operated at

higher temperature of service (Kalpakjian and Schmid, 2006; Callister, 2003).

Therefore, the introduction to the fabrication of composites which utilizes the

advantages of fiber reinforcement should capable to improve the performances compare

to monolithic polymeric material, especially in highly demanding application like

automotives and electronics application.

There are two types of fiber commonly used in composites which are natural fiber and

synthetic fiber. Both types of fiber got higher potential to be used as a reinforcement

agent in composite materials. For low cost of production and widely availability of

fiber, natural fiber had been chosen for this study. Natural fiber had played important

roles in enhancing the composites performance. Kenaf, Jute, and Hemp namely as

natural fiber were widely used as reinforcement for composites. In addition, the

performance of the natural fiber, especially kenaf has proved by researchers previously

as the multipurpose used materials because of kenaf plant itself include the stalks (bast

and core), leaves and seeds to be produced as useful material in manufacturing industry.

Beyond the new uses for kenaf including its utilization in building material, absorbents,

household, and vehicles, the commercial success of kenaf has great potential economic

and environmental benefits in replacement or reduced use of fiberglass in industrial

products and the increased used of recycled plastics (Webber et al., 2002). However,

there were also disadvantages of using natural fiber in thermoplastics through its ligno-

cellulosic properties which are the high moisture absorption of the fibers and the low

processing temperature permissible during the fabrication process (Sanadi et al., 1995).

In order to increase the performances and properties of fabricated composites, the

compatibilizer should be introduced. Various types of chemical reagents have been used

in previous study by researchers such as silane, Maleic-Anhydride Grafted

Polypropylene (MAPP), alkoxysilane and etc. Besides the using of Silane, Maleated

coupling agents are widely used as its main function to enhance the interactions

3

between the matrix and fiber and to strengthen composites containing fillers and fiber

reinforcement (Keener et al., 2004). Therefore, the introduction of MAPP as

compatibilizer has been employed through the study in order to improve the mechanical

properties of the fabricated composites.

1.2 Problem Statements

It is important and possible to produce a new types of material that exhibit the

economically and environmentally benefits for the applications in automotive, building,

furniture and packaging industries. By combining the different resources, it is possible

to blend, mix or process the natural fiber with other elements such as glass, plastics and

synthetics material to produces new classes of materials (Sanadi et al., 1990).

Biodegradable or environmentally acceptable materials have attained increasing interest

in few decades to the researchers and manufactures due to the environmental pressure

derived from the consumption of petroleum-based materials, difficulties in degrade in a

landfill and composting environments (Liu et al., 2006; Huda et al., 2007). Thus, the

introduction of natural fiber such as kenaf, hemp, ramie and flex has attractively

influenced the production of biodegradable materials lately, especially in manufacturing

industry (Bledski et al., 2002).

Natural fiber like kenaf can be used as replacement to the conventional fiber. Global

environmental issues have led to a renewed interest in bio-based materials like fiber

glass or carbon fiber; which the focus on renewable raw materials can be biodegradable

or recyclable at reasonable cost (Hong et al., 2007; Zampaloni et al., 2007). The

problem faced by the researchers and manufacturers is to find the good natural fiber for

polymer composite application equipped with the most promising and outstanding

mechanical and physical properties. The uses of natural plant fibers as a reinforcement

materials to replace synthetic fibers is receiving great attention, due to the advantages of

renewability, low density and high specific strength (Ochi, 2008). These fiber

4

outstanding properties such as high specific strength in stiffness, impact resistance,

flexibility, and modulus make them an attractive alternative over the traditional

materials (Sgriccia et al., 2008). Specifically, the good properties of kenaf fiber include

good specific strengths and modulus, economical viability, low density and low weight

has make them as a reinforcement of choice by industry.

The low processing temperature permissible to the ligno-cellulosic fiber in

thermoplastics is limited due to fiber degradation at higher processing temperatures

(Sanadi et al., 1995). It is important to ensure that the fabrication are employed in the

controlled temperature processing, because the degradation of the kenaf fiber will lead

to the failure or poor performance to the properties of the fabricated composite.

Therefore, the chosen suitable processing temperature is important consideration

accordance to the fabrication of PP/kenaf composites.

1.3 Objectives

The purpose of this study is:

a) To study the effects of different fibers loading of kenaf (wt %) to the mechanical

properties of the fiber reinforced polypropylene composite;

b) To study the effects of proposed compatibilizer on the fabrication of PP/kenaf

fiber and compare its effect to the properties enhancement of the fabricated

composites.

5

1.4 Hypotheses

i). The different filler loading or proportion of kenaf short fiber used for this study

will affect the mechanical properties of the composite. It is expected that, by

increasing the proportion of filler loading, mechanical properties of the

fabricated composite must be also increased correspondingly in accordance with

the rules of mixture theory.

ii). Introduction of compatibilizer in this study will increased the mechanical

properties of the fabricated composites. The good interfacial adhesion formed

between the surface interaction of kenaf fiber and PP matrix is expected to

improve the properties of composites materials.

1.5 Scope of study

The study was started by preparing and characterizing the kenaf fiber as raw materials

to be used as reinforcement material in the fabrication of PP/kenaf composite. The

materials used that related in this study are polypropylene (PP) pellets and kenaf short

fibers. The kenaf short fibers were prepared by using the rotor mill to get the various

size of fiber length. The size and density of the fiber reinforced were determined by

using Scanning Electron Microscope (SEM) model EVO 5 and Electronic Densimeter

model MD300-S, respectively. However, the kenaf properties are difficult to measure,

thus no preliminary study on the kenaf properties was carried out during this research

(Sanadi et al., 1995).

Next stage of process involves the drying study of kenaf fiber. Kenaf fibers will be

dried in the drying oven for seven hours period of time and the weight losses of fibers

were weighed for every hour. The effects of fiber loading for kenaf short fiber on

polypropylene composites were investigates by varying the weight percentage (wt%)

for both materials. There are five fraction of fiber loading will be employed in this study

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