innovative thermoplastic starch based...
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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
INNOVATIVE THERMOPLASTIC STARCH BASED
BIODEGRADABLE PACKAGING FOR FOOD INDUSTRIES
APPLICATION
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Engineering Materials)
by
MAZLIAH BINTI MAZLAN
B050810283
FACULTY OF MANUFACTURING ENGINEERING
2011
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA
TAJUK: INNOVATIVE THERMOPLASTIC STARCH BASED BIODEGRADABLE PACKAGING FOR FOOD INDUSTRIES APPLICATION
SESI PENGAJIAN: 2010/11 Semester 2 Saya MAZLIAH BINTI MAZLAN mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:
1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan
untuk tujuan pengajian sahaja dengan izin penulis. 3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan
pertukaran antara institusi pengajian tinggi. 4. **Sila tandakan (√)
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
Alamat Tetap:
J7743, KM32 Jalan Salim,
Kampung Batu Gajah,
77300 Merlimau, Melaka. Tarikh: _________________________
Disahkan oleh:
PENYELIA PSM
Tarikh: ______________________
** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT atau TERHAD.
DECLARATION
I hereby, declared this report entitled “Innovative Thermoplastic Starch based
Biodegradable Packaging for Food Industries Application” is the results of my
own research except as cited in references.
Signature : ………………………
Author’s Name : Mazliah binti Mazlan
Date : 18 th May 2011
APPROVAL
This report is submitted to the Faculty of Manufacturing Engineering of UTeM
as a partial fulfillment of the requirements for the Degree in Bachelor of
Manufacturing Engineering (Engineering Materials). The member of the
supervisory committee is as follow:
………………………………
Supervisor
i
ABSTRAK
Penyelidikan ini menunjukkan prestasi komposit plastik biolupus yang menggunakan
tepung ubi kayu (TS) dan polypropylene (PP) sebagai bahan utama matriks dengan
penambahan serat gentian tebu (SCFC) sebagai penguat dan gliserol sebagai bahan
tambah pemplastik. Tujuan utama penyelidikan ini adalah untuk membuat
bungkusan plastik biolupus untuk industri makanan dengan menggunakan kaedah
pencampur dalaman yang dinamakan sebagai PTSG Biodegradable Hybrid
Composite. Kesan penggunaan hampas tebu di dalam komposit ini dikaji dengan
lebih lanjut dan hasil komposit yang baik telah dicadangkan. Sampel komposit
dihasilkan dengan menggunakan formula pencampuran yang berbeza dengan
menggunakan kaedah campuran dan mampatan. Bagi mencapai objektif penyelidikan
ini, pengujianan lanjutan untuk mengenalpasti sifat-sifat komposit tersebut dilakukan
melalui ujian tegangan, ujian hentaman, dan ujian lenturan. Ujian-ujian ini dilakukan
bagi menentukan sifat-sifat mekanikal bahan komposit tersebut. Kemudian, diikuti
dengan penilaian sifat persekitaran PTSG Biodegradable Hybrid Composite seperti
ujian biolupus, uji penyerapan air dan ujian pembengkakan tebal. Dalam rangka
untuk mengetahui morfologi patahan sampel, pemerhatian melalui mikroskop
imbasan elektron (SEM) telah dijalankan. Peningkatan kadar tepung ubi telah
meningkatkan kadar pelupusan, penyerapan air dan pembengkakan tebal yang
dihasilkan oleh komposit. Perumusan yang terbaik adalah pada kombinasi 90% PP,
10% TS 1% SCFC dan 3% glycerol untuk PTSG Biodegradable Hybrid Composite
yang mempunyai potensi kinetik pelupusan sebanyak 0.014%/hari bagi penurunan
berat yang memberikan cirri-ciri potensi dalam industri pembungkusan makanan.
Secara keseluruhan, semua tujuan kajian yang dinyatakan telah tercapai dengan
jayanya.
ii
ABSTRACT
This research shows the performance of biodegradable plastic composite using
tapioca starch (TS) and polypropylene (PP) as a primary matrix material with
addition of sugar cane fiber cellulose (SCFC) as reinforcement and glycerol as
additive plasticizer. The main objective of this research is to fabricate a
biodegradable plastic packaging for food industries using an internal mixer method
which produced the novel biocomposites that simply named as PTSG Biodegradable
Hybrid Composite. The effect of SCFC loading was studied as to establish the best
formulation of the PTSG Biodegradable Hybrid Composite. The composites were
fabricated into thin sheets using a hot compression molding machine. The PTSG
Biodegradable Hybrid Composite were tested for tensile test, impact test, and
flexural test. Then, the environmental properties were determined through soil
burying test, weathering test, water absorption test and thickness swelling test. The
fracture morphology of the samples was observed under scanning electron
microscope (SEM). The increasing of tapioca starch content had significantly
increased the degradation, water absorption and swelling thickness of produced
composite. The optimum compounding formulation of the fabricated composites was
observed at the combination of 90 wt.% of PP, 10 wt.% of TS, 1 wt.% of SCFC and
3 wt.% of glycerol for PTSG Biodegradable Hybrid Composites that have the
potential kinetic of degradation at 0.014 %/day of weight reduction which could
potentially applied in the real green food packaging industries as one of new
candidates for future food packaging materials. In overall, all the listed research
objectives were successfully achieved from this preliminary research
iii
ACKNOWLEDGEMENT
Bismillahirrahmanirrahim,
I am so thankful to Allah S.W.T for giving me patient and spirit throughout
this project until the research is successfully completed. With the mercifulness from
Allah therefore I can produce a lot of idea to this project.
I am indebted to my supervisor, Mr. Jeefferie bin. Abd Razak, lecturer from
the Faculty of Manufacturing Engineering for his advice, insightful comments and
support. Thank for your guide and without your guide this research will not be
completed and well organized. Not forgetting for my panels, Dr. Noraiham binti
Mohamad and Miss Siti Rahmah binti Shamsuri for the continuous support and
constructive ideas. Thank you very much.
iv
DEDICATION
Emak, Abah and All My Family Members
Along, Angah, Kak De, Kak Nak, Atam, Atih, Achik, Mamat, Ida
My Bear
My Lecturer, Che Jep
Lovely Friends 4 BMFB 2011
v
TABLE OF CONTENT
Abstrak i
Abstract ii
Acknowledgement iii
Dedication iv
Table of Content v
List of Tables vi
List of Figures vii
List of Abbreviations viii
1. INTRODUCTION 1
1.1 Introduction 1
1.2 Objectives 3
1.3 Problem Statement 3
1.4 Significant of Study 4
1.5 Thesis Overview 4
2. LITERATURE REVIEW 5
2.1 Introduction 5
2.2 Composite 5
2.3 Polymer Matrix Composites (PMC) 6
2.4 Polypropylene (PP) as Matrix Materials 8
2.5 Reinforcement 9
2.6 Natural Fiber 11
2.7 Sugar Cane Fiber Cellulose (SCFC) as Natural Fiber 12
2.7.1 Properties of Sugar Cane Fiber Cellulose (SCFC) 14
2.7.1.1 Physical Properties 14
2.7.1.2 Mechanical Properties 14
2.8 Matrix 15
vi
2.9 Tapioca Starch as Matrix 16
2.10 Glycerol as Plasticizer 18
2.10.1 General Properties of Glycerol 19
2.10.2 Physical Properties of Glycerol 19
2.11 Mechanical Properties of the Composites 20
2.11.1 Tensile Properties 20
2.11.2 Impact Properties 21
2.11 3 Flexural Properties 22
2.12 Environmental Properties Evaluation for PTSG Biodegradable
Hybrid Composite 23
2.12.1 Biodegradation Test 23
2.12.2 Water Absorption Test 25
2.12.3 Thickness Swelling Test 27
2.13 Morphology Observation 27
3. METHODOLOGY 30
3.1 Introduction 30
3.2 Methodology 30
3.2.1 Flow Chart of Methodology 31
3.3 Materials 31
3.3.1 Tapioca Starch (TS) 33
3.3.2 Sugar Cane Fiber Cellulose (SCFC) 34
3.3.3 Glycerol 34
3.3.4 Polypropylene 35
3.4 Raw Materials Preparation 36
3.4.1 Sugar Cane Fiber Cellulose (SCFC) Drying Process 36
3.4.2 Crushing Process 37
3.5 Characterization of Sugar Cane Fiber Cellulose 38
3.5.1 Drying Profile Study 38
3.5.2 Density Measurement 38
3.5.3 Morphological Observation 39
3.6 Sample Fabrication 40
3.6.1 Compounding of PTSG Biodegradable Hybrid composite 40
vii
3.6.2 Hot Compression Molding 42
3.7 Mechanical Testing 42
3.7.1 Tensile Test 43
3.7.2 Impact Test 44
3.7.3 Flexural Test 44
3.8 Environmental Properties Evaluation for PTSG Biodegradable
Hybrid Composite 46
3.8.1a Weathering Test 46
3.8.1b Soil Test 46
3.8.2 Water Absorption Test 47
3.8.3 Thickness Swelling Test 47
4. RESULTS AND DISCUSSIONS 48
4.1 Introduction 48
4.2 Raw Material Characterization 48
4.2.1 SCFC Density Measurement 48
4.3 The Study on the processability of PTSG Biodegradable Hybrid
Composite 51
4.3.1 Processing characteristics of PTSG Biodegradable Hybrid
Composite 51
4.3.2 Torque analysis of PTSG Biodegradable Hybrid Composite 51
4.4 Characterization of Mechanical properties for PTSG Biodegradable
Hybrid Composite 53
4.4.1 Tensile Test Analysis for PTSG Biodegradable Hybrid
Composite 53
4.4.2 Flexural Test / Three Point Bending Analysis for PTSG
Biodegradable Hybrid Composite 57
4.4.3 Charpy Impact Strength Analysis for PTSG Biodegradable Hybrid
Composite 59
4.5 Characterization of environmental evolution for PTSG Biodegradable
Hybrid Composite 61
4.5.1 Weathering properties of PTSG Biodegradable Hybrid
Composite 62
viii
4.5.2 Soil Properties of PTSG Biodegradable Hybrid Composite 65
4.6 Characterization of water absorption properties for PTSG Biodegradable
Hybrid Composite 69
4.7 Characterization of thickness swelling properties for PTSG Biodegradable
Hybrid Composite 70
4.8 SEM analysis of tensile test fractured surface of PTSG Biodegradable
Hybrid Composite 72
5. CONCLUSION AND RECOMMENDATIONS 75
5.1 Conclusion 75
5.2 Recommendations 77
REFERENCES 78
APPENDICES
A Gantt chart for PSM I I
B American Standard Testing Material (2000) Standard Test Method for
Tensile Properties of Plastics
C American Standard Testing Material (2000) Standard Test Methods for
Flexural Properties of Unreinforced and Reinforced Plastics and Electrical
Insulating Materials E Results of Hardness Test
D American Standard Testing Material (2000) Standard Test Methods for
Determining the Izod Pendulum Impact Resistance of Plastics
E American Standard Testing Material (2000) Standard Test Methods for Water
Absorption of Plastics
ix
LIST OF TABLES
2.1 Melting and glass transition temperature for selected polymers 9
2.2 Bagasse chemical compositions 13
2.3 Physical characteristic for some common types of fiber 14
2.4 Mechanical properties of some natural fibers 15
2.5 Physical properties of TS/PCL blends using granular (TS) starch in
various proportions 17
2.6 Specifications for tapioca starch by Thai Tapioca Flour Industry
Trade Association 17
2.7 General information of glycerol 19
2.8 Physical properties of glycerol 19
3.1 Standard Specification of native cassava starch for modification purpose 33
3.2 The basic physical properties of the glycerol used 35
3.3 The Polypropylene (PP) Typical Properties 36
3.4 The PTSG Biodegradable Hybrid Composites formulation 40
3.5 PTSG Biodegradable Hybrid Composite formulation 41
4.1 Density measurement of sugar cane fiber cellulose 49
4.2 Density measurement of some natural fibers and raw material 50
4.3 Mechanical properties of some natural fibers 51
4.4 Impact properties of PTSG Biodegradable Hybrid Composite 60
4.5 Before and after observation of weathering test 63
4.6 Weight before and after weathering test; Percentages of
weight reduction (%). 65
4.7 Before and after observation of soil burial test 66
4.8 Weight before and after burying test; Percentages of
weight reduction (%). 68
x
LIST OF FIGURES
2.1 Polymerization of propylene to polypropylene 8
2.2 Fiber arrangement patterns in the layer of fiber reinforce composite
Material 10
2.3 Classification of natural fibers 12
2.4 Part of the sugar cane 12
2.5 Tensile strength and %strain of LDPE composite sheets 21
2.6 Tensile strengths of LDPE, LDPE/S and LDPE/MS blends 24
2.7 Percentage water absorption of starch-filled poly
(styrene-co-butyl acrylate) polyester nonwoven composites
at room temperature for 24 hrs and 8 days 26
2.8 Rate of water absorption of starch-filled
poly (styrene-co-butyl acrylate) polyester nonwoven composites
at room temperature 26
2.9 Percentage thickness swelling of starch-filled
poly (styrene-co-butyl acrylate) polyester nonwoven composites
at room temperature 27
2.10 SEM micrographs of the cryogenically fractured surface of
(a) and (b) 80/20 LLDPE/TS blend
(c) 80/20/2 LLDPE/S/S-g-OSA (DS = 0.024) blend, and
(d) 80/20/2 LLDPE/S/S-g-OSA (DS = 0.045) blend 28
2.11 SEM micrographs of kenaf fiber surface in composites
(A) 100μm (at 200x) and (B) 10μm (at 500x) 29
3.1 Flow chart of methodology 32
3.2 Tapioca starch 33
3.3. Sugar cane fiber cellulose 34
3.4 Glycerol 35
3.5 Polypropylene 36
xi
3.6 Drying sugar cane fiber cellulose in the oven model
UFB 400, MEMMERT 37
3.7 Rotor mill machine 37
3.8 Drying SCFC in the laboratory oven 38
3.9 Electronic Densimeter 39
3.10 SEM model EVO 50 44
3.11 HAAKE Rheomix OS 41
3.12 Hot compression molding 42
3.13 Universal Testing Machine (UTM) 43
3.14 Tensile specimen 43
3.15 Charpy Types Specimen 44
3.16 Flexural testing at three-point bending set-up 45
3.17 Standard test configuration of flexural test 45
4.1 Average plot of torque value (Nm) versus time (minutes) for the
PTSG Biodegradable Hybrid Composite with different
wt.% of filler loading 51
4.2 Tensile strength of PTSG Biodegradable Hybrid composite
at different composition of PP/TS/SCFC/glycerol 54
4.3 Percentage of Elongation for PTSG Biodegradable Hybrid composite
at different composition of PP/TS/SCFC/glycerol 56
4.4 Tensile Modulus of PTSG Biodegradable Hybrid composite
at different composition of PP/TS/SCFC/glycerol 56
4.5 Flexural Strength of PTSG Biodegradable Hybrid Composite
at different composition of PP/TS/SCFC/glycerol 58
4.6 Flexural Modulus of PTSG Biodegradable Hybrid Composite
at different composition of PP/TS/SCFC/glycerol 58
4.7 Impact strength of PTSG Biodegradable Hybrid composite
at different composition of PP/TS/SCFC/glycerol 61
4.8 Comparison of normal, weathering and soil burial degradation test
for impact strength test results. 69
xii
4.9 Water absorption characteristic PTSG Biodegr adable Hybrid
Composite at different composition of PP/TS/SCFC/glycerol
within 10 days of immersion. 70
4.10 Comparison of thickness deflection PTSG Biodegradable Hybrid
Composite at different composition of PP/TS/SCFC/glycerol
within 10 days 72
4.11 SEM micrograph showed the fractured surface of the virgin pp sample at
a) 500X and
b) 1 000X of magnification 73
4.12 SEM micrograph showed the fractured surface of the PTSG
Biodegradable Hybrid Composite with various compositions
of PP/TS/SCFC/glycerol
a) 100/0/1/3
b) 90/10/1/3
c) 80/20/1/3
d) 70/30/1/3 and
d) 60/40/1/3. 74
xiii
LIST OF ABBREVIATIONS
ASTM American Standard Testing of Materials
CMC Ceramic Matrix Composite
DS Degrees of Substitution
DSC Differential Scanning Calorimetry
Eg. Example
et al. and others
etc. Et cetera
LDPE Low Density Polyethylene
LLDPE Linear Low Density Polyethylene
MAPP Maleic-Anhydride Grafted Polypropylene
MMC Metal Matrix Composite
MS Modified starch
PC Polycarbonates
PCL Polycaprolactrone
PHA Polyhydroxyalkanoate
PHBV polyhydroxybutyrate and hydroxyvalerate
PLA polylactic acid
PMC Polymer Matrix Composite
PP Polypropylene
TS / SCFC Tapioca starch reinforced sugar cane fiber cellulose
S Starch
SCFC Sugar Cane Fiber Cellulose
SEM Scanning electron microscopy
S-g-OSA Succinylated Starches
TGA Thermo Gravimetric Analyzer
TS Tapioca Starch
Wt% Percent of weight fraction
WA Water Absorption
1
CHAPTER 1 INTRODUCTION
1.1 Introduction
A plastic material is one of a wide range of synthetic or semi-synthetic organic
amorphous solid used in the manufacture of industrial products. Due to their
versatility, plastic is great for packaging of a variety products such as processed and
convenience foods, pharmaceuticals and medicines, cosmetics and toiletries,
household and agricultural chemicals, petroleum product and detergent. Nowdays,
plastic containers are successfully replacing glass, tin, metal, aluminum and paper
containers in many applications. This is because plastics are typically polymers of
high molecular mass, and may contain other substances to improve performance of
the fabricated products. Therefore, the advantages of plastics are light and less bulky
than other packaging materials that could be processed into any desired shape or
form such as films, sheets and pouches. On the other hand, it saves costs of storage
and transportation because of lower volume, easy coloring, no rusting and first-rate
water resistance. Although plastic package have great advantages, however they also
have some limitations that includes some chemical attack on particular plastics,
tendency to creep, less heat resistance, lower gas barrier and lower dimensional
stability (Athalye, 2002).
Into the bargain, there are grave problems connected with the analytical control of
such materials which are toxic hazards from the modified plastics and also from their
degradation products, increased costs and the possible encouragement of litter. In
order to trim down this problem, the application of biodegradable material as an
alternative choice is increasingly applied. Biodegradable which are often produced
2
from renewable sources, are being increasingly sought after by food processors as
part of a solution to environmental concerns over waste and the use of fossil fuels.
The process is called biodegradation (Dong et al. 2008). Biodegradation is a natural
process by which organic chemicals in the environment are converted to simpler
compounds, mineralized, and redistributed through the elemental cycles such as the
carbon, nitrogen, and sulphur by the action of microorganism.
In this research, biodegradable polymer matrix composites (PMCs) were developed.
There are two natural components were combined which are tapioca starch (TS) as a
natural matrix material and sugar cane fiber cellulose (SCFC) as a natural biofiber.
Sugar cane has good performance as filler reinforcement, together with the
advantages to the environment when it combines with the tapioca starch matrix.
Polypropylene (PP) and glycerol are being utilized as part of two mixtures as to
produce the innovative formulation as well as to facilitate the processing. It is
expected that the development of this product, will contribute to the world as novel
biodegradable, non-toxic and non-allergenic bio environmental friendly natural green
products.
There is considerable interest and noble aims in this research where to produce an
alternative material by compounding tapioca starch (TS), polypropylene (PP), sugar
cane fiber cellulose (SCFC) and glycerol to replace the existing non biodegradable
plastic material in the commercial market. Thus, overall of this research is to
formulate the biodegradable based composites filled with an agro-waste biofiller by
using the internal mixer method in order to investigate and understand the behavior
and properties as well as characteristic of the tapioca starch (TS), polypropylene
(PP), sugar cane fiber cellulose (SCFC) and glycerol biocomposites or in short is
namely as PTSG Biodegradable Hybrid Composite. Utilization of biodegradable
based product will significantly reduce the need for synthetic polymer production at
low cost, thereby producing a positive effect both environmentally and economically.
3
1.2 Objective
The purposes of this study are:
• To formulate biodegradable packaging material for food industries by using
internal mixer method combining the tapioca starch (TS), polypropylene
(PP), sugar cane fiber cellulose (SCFC) and glycerol, in their formulations.
• To establish and understand the mechanical, morphological and degradation
behavior of novel biocomposites containing tapioca starch (TS),
polypropylene (PP), and sugar cane fiber cellulose (SCFC) and glycerol
mixtures, in comparisons to other biocomposites.
1.3 Problem Statement
There are problems connected with the utilization of hydrocarbon plastic based
materials which are toxic hazards from the modified plastics and also from their
degradation products, high costs and possible encouragement of litter. Allocated to
this problem, it is important to produce innovative products which combine the
utilization of natural filler with other elements such as glass, plastics and synthetics
material. Ecological concerns have resulted in overwhelming interest in natural and
compostable materials and issues related with the biodegrability and environmental
safely that are becoming corresponding important (Yu et al., 2007). Biodegradable or
environmentally acceptable materials have attained increasing interest in few decades
to the researchers and manufactures due to environmental pressure derived from the
consumption of petroleum based materials, difficulties in degradation in a landfill
and composting environments (Liu et al. 2006; Huda et al. 2007). Starch is one of
the most promising materials for biodegradable plastics because of its versatile
biopolymer characteristic with immense potential and low price for application in the
food industries (Mohanty et al., 2000). However, starch was mostly water soluble,
difficult to process and brittle in nature when it is used without the addition of
plasticizer. Furthermore, the mechanical properties are very sensitive to moisture
4
content, which is difficult to control and predict. In principle, some properties of
starch could be significantly improved by blending it with polymer (Dufresne et al.,
2000). As a result, the TS, PP, SCFC and glycerol are combined as to formulate the
new potential biodegradable packaging material for food industries application.
1.4 Significant of Study
In this research, the noble aim is to develop the PTSG Biodegradable Hybrid
Composite for the food packaging application. As a consequence, by conducting this
research, it is expected that it will be benefited to the environment that suffer with
non-degradable waste of plastic food packaging caused by uncontrolled solid waste
disposal and extensive utilization of this necessity. Development of this novel food
packaging alternative will create potential solution to the environmental friendly and
safe packaging medium either for food, consumer or environment as a whole.
1.5 Thesis Overview
This thesis is divided into five chapters that describe the analytical and experimental
research performed. The First Chapter is an introduction to the study that brief about
objectives, problem statement, significant of study and the thesis overview. Chapter
Two present the literature review that relates to the theories on composites and
previous investigations on the biocomposites. The important element that included in
this chapter is about the types of properties for SCFC and TS and also related
experimental testing. Chapter Three, provides details explanations on the
methodology used for overall research work, raw materials, procedure property
analysis that had been done. In Chapter Four, the result of the characterization and
measurement of various engineering properties for the fabricated biocomposites were
explained in details. The final chapter (Chapter 5) concludes the overall results
obtained from this research. In this chapter, it explains either the objectives of this
study are achieved or not. The recommendation for future project also has been
included in this Chapter 5.
5
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction
This chapter review related studies done by previous researcher on the tapioca starch
(TS) as matrix whiles the sugar cane fiber cellulose (SCFC) as reinforcement in the
biocomposites product based development. Through this chapter, the study on the
SCFC, TS and Polypropylene (PP) engineering properties had been highlighted and
extensively reviewed. The literature review mainly focused on the various types of
engineering properties and related experimental testing will be studied and discussed.
The fundamental of composites were reviewed in the first following section and
followed by the engineering properties from the existing research of the
biocomposites, as well as the degradation of the composites.
2.2 Composites
A composite material is a material system that composed of a suitably arranged
mixture or combination of two or more micro or macroconstituents with an interface
separating them that differ in form and chemical composition and are essentially
insoluble in each other (Smith et al. 2000). An engineering importance of a
composite material is that two or more distinctly different materials combine to form
a composite material that possesses properties that are superior, or important in some
other manner, to the properties of the individual components (Smith et al. 2000).
6
Thus, composites are those materials formed by aligning extremely strong and stiff
constituents such as fibers and particulates in a binder called matrix. The materials in
this category have excellent mechanical properties. There are two components in the
composite, which are reinforcing phase and matrix phase. Polymers, ceramic and
metals have found their application as matrix materials. The reinforcing phase is
other component and is called reinforcement and could be fiber, particulate or
laminar (Gupta, 2005). According to Matthews and Rawlings (2002), each of
materials (i.e., matrix and reinforcement) must exist of more than 5 wt% to be
classified as composites material. The purposed of introducing the composites
material is to improve the properties that have been performed by monolithic
material. Thus, the composite is expected to improve the mechanical characteristics
such as stiffness, toughness, ambient and high-temperature resistance (Callister,
2003).
According to Callister (2003), the composites materials are classified by the
geometry of reinforcement and the types of matrix materials used in its constituent.
As a result, there are three main types of geometries of the reinforcement which are
particle-reinforced, fiber-reinforced and structural composites (Callister, 2003).
Types of matrix used in composites also can be divided into four types, namely as
polymer-matrix composite (PMC), metal-matrix composites (MMC), ceramics-
matrix composites (CMC), and carbon-carbon composites (CCC) (Matthews and
Rawlings, 2002; Callister, 2003; Taj et al. 2007). In this study, PMC becomes as the
topic of investigation.
2.3 Polymer Matrix Composites (PMC)
As the terms implied, the polymer matrix composites consists of polymeric material
as the matrix material and fiber as the reinforcement elements (Luz et al. 2007).
Research and engineering interest has been shifted from the monolithic material to
fiber-reinforced polymeric material (Wambua et al. 2003). Polymer matrix
composite is the common types of matrix composites used for a few decades. The
7
enormous applications of PMC have exhibited various performances that cannot be
performed by any monolithic material (Wambua et al. 2003).
There are three types of major classes in polymeric materials which are
thermoplastics, thermosets, and elastomers (Kalpakjian, 2006). Reinforcement of
polymers by strong fibrous network permits fabrication of PMC characterized by the
properties such as high tensile strength, high stiffness, high fracture toughness, good
abrasion resistance, good corrosion and puncture resistance but the main
disadvantages are low thermal resistance and high coefficient of thermal expansion
(Liu et al. 2007; Taj et al. 2007).
The extensive used of PMC as daily life components, exhibits that the PMC has low
density, ρ where the benefit of low density becomes apparent when the tensile
modulus per unit mass, E/ρ (specific modulus), and tensile strength per unit mass,
σ/ρ (specific strength), are considered. Contrarily, it is also observed that the used of
PMC has resulted in the reduction of flexural and tensile strength of the fabricated
composites (Wambua et al. 2003).
There were limitations of PMC which need to be considered, such as their low
maximum working temperatures, high coefficient of thermal expansion, dimensional
instability, and sensitivity to radiation and moisture (Hanlon et al. 1998; Selke et al.
2004; Harper, 2006). This leads to a degree of environmental degradation greater
than that experienced by the component of material alone. Until early 1970s, the
focus was given on the preventing the plastic degradation to avoid the loss in the
performance of the plastic properties. The extent of degradation was generally
measured by the loss percentages of the useful properties. It was stated that 90
percent loss in the tensile strength was equivalent to total degradation, as this was
sufficient to render the plastic object unusable. In the middle of 1980s, when
concerns about solid waste disposal were increased, the interest in biodegradation
intensified as some perceived it as a solution to the landfill crisis (Hanlon et al. 1998;
Selke et al. 2004; Harper, 2006).