THE EFFECT OF DISPERSION ON THE MECHANICAL PROPERTIES OF PLA- BASED POLYMER COMPOSITES
QURRATU AINI BINTI YAACOB
SUPERVISOR DECLARATION
“I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award of the degree of
Bachelor of Mechanical Engineering (Structure & Materials)”
Signature : ...
Supervisor Name : DR. SITI HAJAR BINTI SHEIKH MD FADZULLAH
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THE EFFECT OF DISPERSION ON THE MECHANICAL PROPERTIES OF PLA-BASED POLYMER COMPOSITES
QURRATU’ AINI BINTI YAACOB
This thesis is submitted in partial fulfillment of the requirements for the award of Bachelor of Mechanical Engineering (Structure & Materials)
Faculty of Mechanical Engineering Universiti Teknikal Malaysia Melaka
ii
DECLARATION
“I hereby declare that the work in this thesis is my own except for summaries and
quotations which have been duly acknowledged”
Signature : ...
Author : QURRATU’ AINI BINTI YAACOB
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Special dedications to my beloved family especially to my parents, Yaacob Bin
Senin and Fazilah Binti Mohamed Noor and also do not forgotten to my lovely
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ACKNOWLEDGMENT
I am grateful to Allah S.W.T for His Blessings that put ability to complete
this research. Thousand of sincere thanks are indebted to Dr. Siti Hajar Binti Sheikh
Md Fadzullah. As a supervisor of the project, her cynosure from the initial to the
final level definitely helped towards the completion of this work.
Furthermore, I owe my deepest gratitude to Mr. Hairul Hisham and all the
technicians from either Faculty of Manufacturing Engineering or Faculty of
Mechanical Engineering, who never reject to lean their hands whenever their helps
are needed. Their guidance to handle the machine effectively and efficiently ensured
my safety along completing my research on time.
During this period, I have met many people who are nice and always share
their knowledge and experience regarding this research with me. I learnt a lot from
them. This project would not have possible unless with their experience and
suggestion. Thus, I would take this opportunity to thank them all. On the other hand,
it is an honor for me to give token of appreciation to all my friends and family that
aid directly or indirectly in this research. Lastly, i hope that this research may useful
v ABSTRACT
This project investigates the effect on mechanical properties when pineapple
leaf fibres (PALF) are reinforced with bio-based polymer, polylactic acid (PLA). At
the same time, production of this biocomposite is aiming to replace the
non-biodegradable plastic. Alkaline treatment was employed to modify the strength of
PALF and to improve fiber to matrix adhesion. PALF reinforced PLA biocomposites
are made by using compression moulding process. PLA thin films were stacked
together with unidirectional aligned PALF fibre prior to compression moulding via
hot press machine to form a biocomposite plate. Mechanical properties of PALF
reinforced PLA biocomposite shows a superior improvement with alkaline treatment.
Three types of test were considered for this project which is tensile test (ASTM
D3039), flexural test (ASTM D790) and impact test (ASTM D6110). Scanning
Electron Microscope (SEM) was used to scrutinize the morphology of the PALF
reinforced PLA biocomposite as well as to investigate dispersion on the
biocomposite. It was demonstrated that a superior enhancement on mechanical
properties of PALF reinforced PLA biocomposite can be achieved via the efficient of
vi ABSTRAK
Projek ini mengkaji kesan ke atas sifat mekanikal apabila gentian daun nanas
(PALF) diperkukuhkan dengan bio-polimer, polilactic asid (PLA). Pada masa yang
sama, penghasilan biokomposit ini adalah bertujuan untuk menggantikan plastik
yang tidak mesra alam. Rawatan alkali telah digunakan untuk mengubah suai
kekuatan PALF dan untuk meningkatkan lekatan gentian-matrik. PALF bertetulang
biokomposit PLA dibuat dengan menggunakan acuan mampatan proses. Filem PLA
nipis telah disusun bersama-sama dengan PALF yang telah disusun dengan satu arah
sejajar sebelum ia dimampatkan menggunakan mesin acuan mampatan untuk
membentuk kepingan biokomposit. Sifat mekanikal PALF bertetulang PLA
biokomposit dengan rawatan alkali menunjukkan peningkatan yang tinggi. Tiga jenis
ujian mekanik telah dipertimbangkan untuk projek ini iaitu ujian regangan (ASTM
D3039), ujian lenturan (ASTM D790) and ujian hentaman (ASTM D6110).
Mikroskop Imbasan Elektron (SEM) telah digunakan untuk meneliti morfologi
PALF bertetulang PLA biokomposit serta untuk menyiasat penyebaran gentian daun
nenas di dalam biokomposit. Ia telah menunjukkan bahawa peningkatan yang unggul
dalam sifat mekanik bagi PALF bertetulang PLA biokomposit boleh dicapai melalui
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TABLE OF CONTENT
CHAPTER INDEX PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENT vii
LIST OF TABLES xi
LIST OF FIGURES xiii
LIST OF SYMBOLS xvii
LIST OF APPENDIX xviii
CHAPTER I INTRODUCTION
1.1 Introduction 1
1.2 Objectives 3
viii
1.4 Problem Statement 4
1.5 Planning and Execution 5
CHAPTER II LITERATURE REVIEW
2.1 Introduction 7
2.2 Composite 7
2.2.1 Classification of Composite Material 10
2.2.1.1 Polymer Matrix Composite 11
2.2.1.2 Metal Matrix Composite 12
2.2.1.3 Ceramic Matrix Composite 13
2.3 Biocomposites 14
2.3.1 Matrix Material 15
2.3.1.1 Polylactic Acid 15
2.3.1.2 Polypropylene 16
2.3.2 Natural Fibre Reinforcement 16
2.3.2.1 Properties of natural fibre 20
2.3.3 Pineapple Leaf Fibre 21
2.4 Mechanical Properties of Biocomposite 23
2.4.1 Tensile Properties of PALF Biocomposite 23
2.4.2 Flexural Properties of PALF Biocomposite 26
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2.5 Factors Affecting The Composite Properties 28
2.6 Modification of Natural Fibre 29
2.6.1 Chemical Methods 29
2.6.1.1 Alkaline Treatment 29
2.6.1.2 Silane Treatment 31
CHAPTER III RESEARCH METHODOLOGY
3.1 Introduction 32
3.2 Materials 35
3.3 Fiber Surface Modification 38
3.4 Composite Preparation 39
3.4.1 Testing Sample Preparation 42
3.5 Testing Methods 44
3.5.1 Tensile Testing 44
3.5.2 Flexural Testing 46
3.5.3 Impact Testing 49
3.5.4 Morphology Study 50
CHAPTER IV RESULT AND DISCUSSION
4.1 Introduction 51
x
4.1.2 Flexural Properties 60
4.1.3 Impact Properties 64
CHAPTER V CONCLUSIONS AND RECOMMENDATION
5.1 Conclusions 68
5.2 Recommendation For Future Works 70
REFERENCES 71
BIBLIOGRAPHY 76
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LIST OF TABLES
NO. TITLE PAGE
1.1 Gantt chart for Final Year Project 1 5
1.2 Gantt chart for Final Year Project 2 6
2.1 Chemical composition of natural fibres [25] 19
2.2 Properties of natural fibre [26] 20
3.1 Properties of Polylactide Acid (6100D) 36
3.2 Properties of pineapple leaf fibre 37
4.1 Average tensile properties of the sample 52
4.2 Comparison on tensile strength and modulus of elasticity for PALF reinforced PLA biocomposite between
experimental and theoretical
54
4.3 Comparison on tensile properties of PALF reinforced PLA biocomposite between treated with NaOH, theoretical and treated with silane coupling agent.
58
4.4 Average flexural strength and modulus of elastic result 60
4.5 Comparison on flexural properties of PALF reinforced PLA biocomposite between treated with NaOH, theoretical and treated with silane coupling agent
62
4.6 Energy absorbed of plain PLA and PALF reinforced PLA biocomposite samples
64
4.7 Comparison on energy absorbed of PALF reinforced PLA biocomposite treated with NaOH and treated with silane coupling agent
xii
xiii
LIST OF FIGURES
NO. TITLE PAGE
2.1 Classification of composite material respect to the matrix constituent [17]
10
2.2 The molecular structure of PLA [9] 15
2.3 Molecular structure of polypropylene [4] 16
2.4 Categories of natural fibres [23] 17
2.5 Different kind of reinforcing natural fibres [24] 18
2.6 Structure of cell wall of the natural fibres [24] 19
2.7 Views of pineapple leaf 21
2.8 Optical micrograph of cross section of PALF [10] 22
2.9 Relationship between Young’s modulus and tensile
strength versus volume fraction of pineapple leaf fibre of PALF/PP composite (Arib et al .,2006)
24
2.10 Graph of tensile strength and Young’s modulus versus (a) mixing time and (b) rotor speed (George et al., 1995)
25
2.11 Flexural modulus versus volume fraction (Arib et al., 2006)
26
2.12 Graph of work of fracture of PALF-Polyester composite versus fibre content with fibre length of 30mm (Dewi et al., 1998)
27
2.13 Typical structure of (a) untreated and (b) treated with alkaline treatment [32]
30
xiv
3.2 Overview of research methodology 34
3.3 Flow of the fabrication process 35
3.4 Views of (a) polylactide acid and (b) pineapple leaf fibre
37
3.5 Views of PALF immersed in NaOH solution 38
3.6 Views of PALF were air dried 39
3.7 Graph of temperature versus time for the fabrication process
40
3.8 Compression moulding 41
3.9 PALF/PLA composite plate (a) before and (b) after demoulded produced via hot press machine
41
3.10 Shearing machine 42
3.11 Tensile specimen 43
3.12 Tensile specimen with aluminum plate end tabbed 43
3.13 The dimension of the specimen for tensile test 45
3.14 Views of (a) Universal Testing Machine (UTM) for tensile and flexural testing and (b) UTM during tensile test
45
3.15 Allowable range of loading nose and support radii in ASTM D790 [36]
47
3.16 The dimension of the specimen for impact test 49
3.17 Scanning Electron Microscope 50
4.1 Graph of comparison on the tensile strength between plain PLA and PALF reinforced PLA biocomposite
52
4.2 Graph of comparison on modulus of elasticity between plain PLA and PALF reinforced PLA biocomposite
52
4.3 Graph of comparison on the tensile strength for PALF reinforced PLA biocomposite between experimental and theoretical result
xv
4.4 Graph of comparison on the modulus of elasticity for PALF reinforced PLA biocomposite between
experimental and theoretical result
55
4.5 Visual observation on failed tensile test specimen of (a) plain PLA and (b) PALF reinforced PLA biocomposite
57
4.6 SEM micrographs image of plain PLA specimen failed in tensile test at (a) 100 x and (b) 500 x magnification
57
4.7 SEM micrographs image of PALF reinforced PLA biocomposite specimen failed in tensile test at (a) 100 x and (b) 500 x magnification
57
4.8 Graph of comparison on the tensile strength for PALF reinforced PLA biocomposite between treated with NaOH, theoretical and treated with silane coupling agent
58
4.9 Graph of comparison on break elongation for PALF reinforced PLA biocomposite between treated with NaOH and treated with silane coupling agent
59
4.10 Graph of comparison on flexural strength between plain PLA and PALF reinforced PLA biocomposite
60
4.11 Graph of comparison on modulus of elasticity between plain PLA and PALF reinforced PLA biocomposite
61
4.12 Graph of comparison on flexural strength for PALF reinforced PLA biocomposite between treated with NaOH and treated with silane coupling agent
62
4.13 Graph of comparison on modulus of elasticity for PALF reinforced PLA biocomposite between treated with NaOH and treated with silane coupling agent
63
4.14 Graph of comparison on the energy absorbed between plain PLA and PALF reinforced PLA biocomposite specimens
65
4.15 Graph of comparison on the energy absorbed for PALF reinforced PLA biocomposite between treated with NaOH and treated with silane coupling agent with plain PLA as the control value
66
4.16 Visual observation on failed impact test specimen of (a)
xvi
4.17 SEM micrographs image of plain PLA specimen failed in impact test at (a) 100 x and (b) 500 x magnification
67
4.18 SEM micrographs image of PALF reinforced PLA biocomposite specimen failed in impact test at (a) 100 x and (b) 500 x magnification
xvii
LIST OF SYMBOLS
v = Volume fraction
w = Weight fraction
V = Volume
W = Weight
°C = Degree Celsius
σ = Stress
ε = Strain
E = Modulus of Elasticity
% = Percentage
xviii
LIST OF APPENDIX
NO TITLE PAGE
A Results of tensile 78
B Results of flexural 80
1 CHAPTER I
INTRODUCTION
1.1 INTRODUCTION
Polymeric material may be regarded as a renewable source with good
potential on the biodegradability or compost ability in order to reduce the overall
environmental impact since over the past decades. The result from this has brought
the academic and industrial people of polymer composite towards the biodegradable
polymers from renewable resources for many kind of application [1]. In this context,
biodegradable polymers like polylactide acid (PLA) as one of the natural fiber-based
polymer have been subject of many researches during the past decade [2]. In order to
produce an alternative material which can replace the conventional petroleum-based
plastics, the technological innovation has been developing the scientific knowledge
of producing new materials [3]. The succesful development of a new material will
bring a lot of benefits to humankind and the environment. As for example, by
making use of biodegradable material can reduce the impact of overall
environmental. The constraints that always arise when the desire to fulfill the needs for promoting the performance of these materials were leads the all over the world’s researchers to boost their efforts in producing a new and better materials. Composite materials, especially ‘green composite’ which can be found from the daily products fit well into this new paradigm shift.
There is a growing trend to use biofibers as fillers and reinforced in polymer
composites. Their uniqueness has make them much attractive to manufacturers
2
much flexible during the fabrication processing, high in specific stiffness, low in
thermal expansion but really high in strength and fatigue resistance. This century has
witnessed ever-increasing demands for the utilization of plastics as important raw
materials, more than 80% of which are thermoplastics. Biofiber reinforced plastics
composites are gaining more and more acceptance in structural application [4].
On the other hands, natural fibers were introduced with lighter composited
and offer lower cost compared to existing synthetics materials such as fiber glass
reinforced composites. Natural fiber has produced a lighter composite. This is
because the natural fiber itself has a lower density (1.2 – 1.6 gcm-3) than the glass
fiber (2.4 gcm-3) [5]. Technological development connected with consumer demands
has continues to increase demands on global resources, leading to major issues of
material availability and environmental sustainability. Biofiber composite have
become more sufficient as new compositions and the related processes have been
intensively researched, developed and consequently applied. The petroleum crises
made biocomposite significantly important and have become engineering materials
with a very wide range of properties [4].
The use of bio-based plastics as reinforced matrices for biocomposites is
gaining more and more attention day by day. The rapidly wider use of composite
components in industries such automotive industry, construction industry, sports and
leisure and other mass production industries, have lead to growing concern to focus
on sustainable and renewable reinforced composites. Thus, the incorporation of
reinforcements of fiber into composites affords a means of extending and improving
the properties of the composites that meets the requirements of most engineering
applications. As a result, these improvements will be associated with economic
advantages. Hence, the demands for natural fiber reinforced composites have
increased drastically for various commercial applications in the industrial sector [5].
Since natural fiber reinforced biocomposites has been developed, it has been
used as automotive parts because of this material have good in mechanical properties
beside a light weight properties. Therefore, it will help the users in reducing the
consuming of petroleum oil since the price of oil is increasing from time to time. On
3
several years for the production of non-structural components and their use is
predicted to constantly increase in a coming years. The upcoming efforts are aimed
at developing 100 % structural composites with the utilizing of bio-source polymers
as the matrix for natural fibers reinforcement instead of depending on the using of
the synthetic fibers [6].
The adoption of PLA for automotive parts has been studied since PLA based
automotive parts emit less CO2 compared to other petroleum-based thermoplastics
materials. PLA also provides good aesthetics, easy process ability in most equipment
beside have a good strength. However, PLA has a brittleness properties and it needs
modification for most practical application. One of the best idea to improve the
mechanical and thermal properties of PLA is by introducing the fibers or filler
material to that matrix [7].
1.2 OBJECTIVES
The objectives of this project are listed as below:
1. To produce PLA-based polymer composites with good mechanical
and physical properties.
2. To study the effect of using chemical coupling agent on the bonding
mechanism present in the PLA-based polymer composites.
3. To access the effect of dispersion on the tensile and impact properties
of the degradable polymer composites.
1.3 SCOPES
The scopes of this project are listed as below:
i. Selection of materials and chemicals for the composites.
ii. Fabrication of biodegradable polymer composites test panels.
iii. Mechanical testing.
4 1.4 PROBLEM STATEMENT
The production rate for worldwide automotive at this time is drastically
increased. Therefore, the limited of petroleum resources will increase the
petroleum-based products; price from year to year [8]. The growing environmental awareness
and new rules and regulations are forcing the industries to seek more ecologically
friendly materials for their product.
Living green has become a popular trend in the last twenty years and
reducing oil consumption remains an important goal for the sustainably-minded
today [9]. The highest of uses of crude oil is in the production of plastics. These
plastics later end up in landfills where it takes years to break down or it will not
entirely break down. As consequently, it will bring a negative impact towards the
environmental. The becoming prices of petroleum-based plastics are predicted to be
more expensive as oil prices continue to increase [10]. The economic and ecological
drawbacks of petroleum-based plastics have pushed researchers to develop and
investigate biodegradable plastics as an environmentally-friendly alternative.
A bio-based polymer as well as natural resource such PLA is ideal candidate
to non-renewable petroleum based which is synthetic polymer. PLA is not only
having degradability but PLA is the only natural resource produce at a large scale
annually [11]. However, this type of material is brittle and has low tensile strength
and impact properties in comparison to that of the petroleum-based polymer
composites. Hence, this study aims to investigate the effect of dispersion on the
