mechanical properties of pineapple leaf fibre (palf) reinforced rubber
TRANSCRIPT
MECHANICAL PROPERTIES OF PINEAPPLE LEAF FIBRE (PALF)
REINFORCED RUBBER COMPOSITE
NUR IMIRAH BINTI ISHAIMI
UNIVERSITI TEKNOLOGI MALAYSIA
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PSZ 19:16 (Pind. 1/97)
UUNNIIVVEERRSSIITTII TTEEKKNNOOLLOOGGII MMAALLAAYYSSIIAA
BORANG PENGESAHAN STATUS TESIS
JUDUL: MECHANICAL PROPERTIES OF PINEAPPLE LEAF FIBRE (PALF)
REINFORCED RUBBER COMPOSITES.
SESI PENGAJIAN: 2006 / 2007-2 Saya ________________________________________________________________________
(HURUF BESAR)
Disahkan oleh ____________________________________ __________________________________
(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)
Alamat Tetap: Nama Penyelia:
NO. 43 KAMPUNG CHAIN,
33400 LENGGONG,
PERAK DARUL RIDZUAN
Tarikh: 4th May 2007 Tarikh: 4th May 2007
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)
mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hakmilik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3 . Perpustakaan dibenarkan membuat sal inan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi. 4. **Sila tandakan ( )
SULIT
(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
TERHAD
TIDAK TERHAD
PROFESOR MADYA DR. ABDUL RAZAK B. RAHMAT
CATATAN: * Potong yang tidak berkenaan. ** J ika tesis in i SULIT a tau TERHAD, s i la lampirkan surat daripada pihak
berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.
Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM).
NUR IMIRAH BINTI ISHAIMI
I 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 Chemical Engineering (polymer)
Signature :��������������
Name of Supervisor : Assoc. Prof. Dr. Abdul Razak Bin Rahmat
Date : 4th May 2007
MECHANICAL PROPERTIES OF PINEAPPLE LEAF FIBRE (PALF)
REINFORCED RUBBER COMPOSITE
NUR IMIRAH BINTI ISHAIMI
A thesis submitted in partial fulfillment
of the requirements for the award of the degree of
Bachelor of Chemical Engineering (Polymer)
Faculty of Chemical and Natural Resources Engineering
Universiti Teknologi Malaysia
MAY 2007
I declare that this thesis entitled �Mechanical Properties of Pineapple Leaf Fibre
(PALF) Reinforced Rubber Composites� is the result of my own research except as
cited in the references.
Signature :��������������
Name : Nur Imirah Binti Ishaimi
Date : 4st May 2007
To my beloved family and fellow friends,
All your contributions, I will always keep in my heart.
Thanks a lot for the support and sacrificing.
ACKNOWLEDGEMENT
Alhamdulillah, thanks to Allah S.W.T, finally I have completed my thesis.
First of all, I wish to express my honest appreciation to my supervisor, Assoc. Prof.
Dr. Abdul Razak Bin Rahmat for his valuable idea, advice, encouragement and for
his guidance throughout this project. Without his continued support and interest, this
thesis would not been the same as presented here. Thanks also to Head of Polymer
Engineering Department, Prof. Dr. Azman Bin Hassan and others lecturer for their
on-going support and contribution to the success of this thesis.
My truthful appreciation also to the polymer laboratory assistants and
technicians Mr. Sukor Ishak, Mr. Nordin Ahmad, Mr. Azri, Mr. Suhee Tan Hassan
and Miss Zainab Salleh for their guidance and support since I startied my project
through the end.
Last but not least, to my beloved family for their moral support. Not forgotten
to all my lovely friends who always give support, share knowledge and lend a hand
in this project. Thank you very much.
ABSTRACT
Pineapple leaf fibre (PALF) is a waste product of pineapple cultivation. This
fibre has potential as reinforcing fillers in thermosets, thermoplastics, and elastomers
and exhibit excellent mechanical properties. However, PALF reinforced natural
rubber has not been reported in literature. Therefore, the mechanical properties of
pineapple leaf fibre (PALF) reinforced rubber composite have been studied. The
objectives in this study were to investigate the effect of fibre loading, addition of
coupling agent and fibre treatment in rubber composite by comparing the mechanical
properties. PALF and rubber were compounded in two roll mill machine and hot
press to form composite sheet. Sodium Hydroxide (NaOH) was used as treatment
agent and Vinyl trimethoxysilane (VTMO) as a coupling agent. The mechanical
properties were analyzed by standard testing namely Tensile Test (ASTM D412) and
Hardness Test (ASTM D2240). Tensile and hardness properties basically show
improvement. Tensile strength decreased with increasing fibre loading. Meanwhile,
hardness and the Young�s modulus are increased with increasing fibre loading.
Moreover, by the addition of coupling agent, tensile strength and hardness were
improved. The results also showed that rubber composite filled with treated fibre had
higher tensile strength and hardness than untreated fibre at similar loading.
ABSTRAK
Serat daun nenas (PALF) merupakan sisa daripada penanaman nenas. Serat
ini mempunyai potensi sebagai bahan peneguh dalam termoset, tremoplastik dan
elastomers. dan juga sifat mekanikal yang baik. Walaubagaimanapun, PALF
meneguhkan getah semulajadi belum pernah dilaporkan di dalam kesussasteraan.
Oleh itu, sifat-sifat mekanikal komposit getah yang diteguh oleh serat daun nenas
telah di kaji. Tujuan kajian ini adalah untuk mengetahui kesan daripada penambahan
serat, penambahan agen perangkai and serat yang telah dirawat.PALF dan getah
diadun dengan menggunakkan �two roll mill� dan �hot press� untuk membentuk
kepingan komposit. Sodium Hydroxide (NaOH) digunakan sebagai bahan rawatan
dan Vinyl trimethoxysilane (VTMO) sebagai agen perangkai. sifat-sifat mekanikal di
analisis dengan alat ujikaji piawai iaitu Ujian Ketegangan (ASTM D412) dan Ujian
Kekerasan (ASTM D2240). Selalunya sifat ketegangan dan kekerasn menunjukan
perubahan yang biak. Kekuatan tegangan menurun dengan penambahan serat.
Manakala, kekerasan dan Young�s modulus juga meningkat dengan penambahan
serat. Selain itu, dengan penambahan agen perangkai kekuatan teganan and
kekerasan telah menunjukkan perubahan yang baik. Begitu juga dengan komposit
yang telah diteguh dengan serat yang dirawat telah menunjukkan serat yang dirawat
mempunyai kekuatan tegangan dan kekerasan yang lebih tinngi berbanding serat
tanpa rawatan pada penambahan serat yang sama.
TABLE OF CONTENTS
CHAPTER TITLE
PAGE
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES x
LIST OF SYMBOLS xi
LIST OF APPENDIX xii
1 INTRODUCTION
1.1 Introduction 1
1.2 Statement of Problem 3
1.3 Objectives 4
1.4 Scopes of Research 4
2 LITERATURE REVIEW
2.1 Introduction 5
2.2 Natural Fibre 8
2.3 Pineapple leaf fibre (PALF) 9
2.4 Natural Rubber 12
3 METHODOLOGY
3.1 Introduction 15
3.2 Raw Materials Preparation 15
3.2.1 Preparation of Pineapple Leaf Fibre
(PALF)
15
3.3 Sample Preparation 16
3.3.1 PALF-Rubber Composite Preparation 16
3.3.2 Testing Sample Preparation 18
3.4 Testing Methods 18
3.4.1 Tensile Testing 18
3.4.2 Hardness Testing 20
4 RESULTS AND DISCUSSION
4.1 Introduction 22
4.1.1 Effect of coupling agent 22
4.1.2 Effect of fibre loading 24
4.1.3 Effect of fibre treatment 27
5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 29
5.2 Recommendation and future work 30
REFERENCES 31
APPENDIX 35
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Comparison between natural and glass fibres 7
2.2 Advantages and disadvantages of natural fibre compared to
glass 8
2.3 The physical and mechanical properties of PALF from SITRA 11
2.4 Properties of Natural Rubber 13
3.1 Different loadings of PALF and varying amount of Silane
coupling agent in rubber composites. 17
3.2 Dimension of the dumbbell shaped (Type v) tensile test sample 19
LIST OF FIGURES
FIGURE NO. TITLE PAGE
3.1 The extraction machine 16
3.2 The extraction machine
3.3 Dumbbell Shaped Specimen Dimension for type v
in ASTM D638 19
3.4 The type A indentor 20
3.5 The Shore Durometer 21
4.1 Tensile strength for various concentrations of
coupling agent at various fibres loading in rubber
composites 23
4.2 Hardness for various fibres loading in rubber
composites 24
4.3 Tensile strength and Young�s modulus at 5 phr of
coupling agent by increased fibre loading. 24
4.4 Elongation at break by increased fibre loading 26
4.5 Tensile strength for treated and untreated PALF 27
4.6 Hardness for treated and untreated PALF 27
4.7 Young�s modulus for treated and untreated PALF 28
LIST OF SYMBOLS AND ABBREVIATIONS
CBS - N-cyclo-hexyl-2-benzothiazole sulfenamide
CO2 - Carbon dioxide
DCP - Dicumyl Peroxide
HDPE - High Density Polyethylene
HRH - Hexa-Resorcinol-Hydrated Silica
IFSS - Interfacial Shear Strength
LDPE - Low Density Polyethhylene
NaOH - Sodium Hydroxide
NR - Natural Rubber
phr Part per hundred
PALF - Pineapple Leaf Fibre
PALFs - Pineapple Leaf Fibres
PE - Polyethylene
PF - Phenol Formaldehyde
PMPPIC - Poly(methylene) poly(phenyl) isocynate
PP - Polypropylene
PS - Polystyrene
SBR Styrene Butadiene Rubber
SEM - Scanning Electron Microscope
SMR L - Standard Malaysia Rubber
t2 - Scorch Time
t90 - Cure Time
TDI - Toluene Diisocyanate
VTMO Vinyl trimethoxysilane
LIST OF APPENDIX
APPENDIX
NO
TITLE
PAGE
A Tensile Test Results 35
CHAPTER 1
INTRODUCTION
1.1 Introduction
Natural fibres, often referred to as vegetable fibres, are extracted from plants
and are classified into three categories, depending on the part of the plant they are
extracted from (fruit, bast and leaf). Currently many types of natural fibre are being
studied to reinforce with polymer like flax, hemp, jute, straw, wood fibre, rice husks,
cane (sugar and bamboo), grass, reeds, ramie, oil palm empty fruit bunch, sisal, coir,
kapok, banana fibre, pineapple leaf fibre and papyrus. Natural fibres form an
interesting alternative for the most widely applied fibre in the composite technology.
People like to use natural fibres as reinforcement because its have advantages such as
renewable nature, low cost, easy availability, and ease of chemical and mechanical
modification.
Natural fibres are increasingly being used as reinforcement in commercial
thermoplastics and thermoset. Many researchers have carried out study to ensure the
potential of natural fibres to be reinforced in thermoplastics and thermoset that can
be applied in industries. The most common thermoplastic and thermoset that have
been used are polypropylene (PP), polystyrene (PS), polyester, epoxy, and
polyethylene (PE). A studied in relation to natural fibre with thermoplastic has been
carried out by Ajay et al. (2006) on mechanical properties of wood�fibre reinforced
polypropylene composites with addition of compatibilizer or coupling agent. The
studies found that the addition of the compatibilizer has resulted in greater
reinforcement of composites, as indicated by the improvement in mechanical
properties. With the wood-fibre content in the composites (PP) increasing from 10 to
50 wt %, the tensile strength, tensile modulus and flexural strength were increased.
However the addition of wood�fibre has resulted in a decrease in elongation at break
and impact strength of the composites.
Manikandan Nair et al. (2001) have been presented a research on thermal and
dynamic mechanical analysis of polystyrene (PS) composites reinforced with short
sisal fibres. The effects of fibre loading, fibre length, fibre orientation and fibre
modification on the dynamic mechanical properties of the composites were
evaluated. PS/sisal composites are thermally more stable than unreinforced PS and
sisal fibre. The addition of 10% fibre considerably increased the modulus but the
increase was found to level off at higher fibre loadings. The Tg values of the
composites were lower than that of unreinforced PS. The treated-fibre composites
showed better properties than those of untreated-fibre composites. Therefore, natural
fibres reinforcement is a good alternative to improve mechanical, dynamic and
thermal properties of composites and cheaper than others.
Among various natural fibres, pineapple leaf fibres (PALFs) exhibit excellent
mechanical properties which are associated with its high cellulose content and
comparatively low microfibrillar angle. PALFs are a waste product of cultivation.
Hence, without high additional cost input, PALFs can be obtained for industrial
purposes. Therefore, many researches have carried out research to investigate the
effect and advantages of PALFs reinforce in thermoplastic and thermoset.
Fewer researches have been proved that mechanical properties of polymer
composites can be improved by PALFs as reinforcement. Among those researchers
were Arib et al. (2006) who studied on the mechanical properties of pineapple leaf
fibres (PALFs) reinforced polypropylene (PP) composites. The observation showed
that tensile modulus (modulus Young�s) and tensile strength increased with the
increase in volume fraction with addition of fibres until 10.8%, but the modulus
slightly decreased with addition of high volume (16.2% of fibres). This is because at
high volume fraction the fibres act as flaws and are not perfectly aligned with matrix.
However, the elongation at break decreased with increasing of volume fraction
because the elasticity of polypropylene decreased and the composite became brittle
after the increase in volume fraction. The increase in volume fraction also provided
higher void content and low interfacial between PALFs and PP.
Mechanical properties of PALFs reinforced polyester composites were
carried out by Devi et al. (1997). The research was to investigate the effect of fibre
length, fibre loading and coupling agent on mechanical properties of the composites.
The result illustrated that the stress-strain behavior in tension of polyester was brittle
and the addition of fibers made the matrix more ductile. The tensile strength,
Young�s modulus and impact strength of PALF polyester composites increased
linearly with the fiber weight fraction. However, flexural strength was leveling off
further than 30%. Compared to other natural-fiber polyester composites, the PALF
composites demonstrated greater mechanical properties and can be applied as
structural composites.
Based on the previous findings mentioned above, PALFs have a good
potential to be used as a reinforcement of polymer composites whether in
thermoplastics or thermoset matrix. However, PALFs have not been used by any
other research to reinforce natural rubber. The advantages of rubber composites are
design flexibility, high low strain moduli, stiffness, damping and process economy.
Few researchers have presented rubber composites study by using natural fibre as
reinforcement material such as oil palm fibre, coir fibre and bamboo fibre. Thus, this
research interest is to study the mechanical properties of PALFs reinforced rubber
composites by varying the fibres loading and the amount of coupling agent.
1.2 Problem Statement
There are several questions that need to be answered from this research:
i. What are the effect of fibre loading on the mechanical properties of PALF
rubber composites such as tensile and hardness?
ii. What is the achievement in mechanical properties after treating the fibre in
rubber composites?
iii. What is the effect of adding coupling agent on the mechanical properties of
PALF rubber composites?
1.3 Objectives
The goals of this research are:
i. To investigate the mechanical properties of PALF rubber composites such as
tensile and hardness with various fibre loading.
ii. To compare the mechanical properties of untreated and treated fibre in rubber
composite.
iii. To study the effect of adding coupling agent on the mechanical properties of
rubber composite.
1.4 Scopes of Research
The scopes of research are:
i. Preparation of pineapple leaf fibre (PALF) - fibre extraction from leaf
ii. Treatment of fibre
iii. Preparation of rubber
iv. Compounding of PALF, rubber and coupling agent using Two-roll mill
machine
v. Rubber curing using hot press
vi. Testing to find out mechanical properties
Tensile Test (ASTM D412)
Hardness Test (ASTM D2240)
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
A composite material is a combination of two or more materials differing in
form or composition on a microscale which do not dissolve or merge completely into
one another, it can be physically identified and exhibit an interface between one
another. There are several composite of classifications. The most common composite
classification is Polymer Matrix Composite (PMC�s) or Fibre Reinforced Polymers
(FRP). These materials use a polymer based resin as the matrix and a variety of fibre
such as glass, carbon, aramid and natural fibre as reinforcement.
In the past few decades, research and engineering interest has been shifting
from monolithic materials to fibre-reinforced polymeric materials. These composite
materials (notably aramid, carbon and glass fibre reinforced plastics) now dominate
the aerospace, leisure, automotive, construction and sporting industries. Glass fibres
are the most widely used to reinforce plastics due to their low cost (compared to
aramid and carbon) and fairly good mechanical properties. However, these fibres
have serious drawbacks as indicated in Table 2.1(Paul et al., 2003).
Table 2.1 Comparison between natural and glass fibres (Paul et al., 2003 )
Natural fibres Glass fibres
Density Low Twice that of natural fibres
Cost Low Low but higher than NF
Renewability Yes No
Recyclability Yes No
Energy consumption Low High
Distribution Wide Wide
CO2 neutral Yes No
Abrasion to machines No Yes
Health risk when inhaled No Yes
Disposal Biodegradable Not biodegradable
Attempts have been made to use natural fibre composites in place of glass
mostly in non-structural applications. So far a good number of automotive
components previously made with glass fibre composites are now being
manufactured using environmentally friendly composites. Currently, plenty of
research material is being generated on the potential of cellulose based fibres as
reinforcement for plastics. All researchers who have worked in the area of natural
fibres and their composites are agreed that these renewable, abundantly available
materials have several bottlenecks: poor wettability, incompatibility with some
polymericmatrices and high moisture absorption by the fibres (Paul et al., 2003).
Recent research and development (Rijswijk et al., 2003) have shown that
these aspects can be improved considerably. Knowing that natural fibres are cheap
and have a better stiffness per weight than glass, which results in lighter components,
the grown interest in natural fibres is clear. Secondly, the environmental impact is
smaller since the natural fibre can be thermally recycled and fibres come from a
renewable resource. Their moderate mechanical properties restrain the fibres from
using them in high-tech applications, but for many reasons they can compete with
glass fibres. Advantages and disadvantages determine the choice in Table 2.2
(Rijswijk et al., 2003).
Table 2.2 Advantages and disadvantages of natural fibre compared to glass
(Rijswijk et al., 2003)
Advantages Disadvantages
i. Low specific weight, which results in a
higher specific strength and stiffness
than glass. This is a benefit especially
in parts designed for bending stiffness.
ii. It is a renewable resource, the
production requires little energy, CO2 is
used while oxygen is given back to the
environment.
iii. Producible with low investment at low
cost, which makes the material an
interesting product for low-wage
countries.
iv. Friendly processing, no wear of tooling.
v. No skin irritation.
vi. Thermal recycling is possible, where
glass causes problems in combustion
furnaces.
vii. Good thermal and acoustic insulating
properties.
i. Lower strength properties,
particularly its impact
strength
ii. Variable quality, depending
on unpredictable influences
such as weather.
iii. Moisture absorption, which
causes swelling of the
fibres.
iv. Restricted maximum
processing temperature.
v. Lower durability, fibre
treatments can improve this
considerably.
vi. Poor fire resistance.
vii. Price can fluctuate by
harvest results or
agricultural politics.
Composite technology in the rubber industry has been a growing science. A
large number of researches have been done in fibre reinforcement of rubber. Rubber
is used as the base material in a product if it requires rubber-like elasticity and
flexibility. In certain cases, rubber products require stiffness along with flexibility,
often in specific directions. This can be achieved by reinforcing rubbers with long or
short fibers to form composites. The advantages of rubber composites are design
flexibility, high low strain moduli, stiffness, damping and process economy.
2.2 Natural Fibre
Fibre is a class of hair-like materials that are continuous filaments or are in
discrete elongated pieces, similar to pieces of thread. Fibres can be spun into
filaments, thread, or rope. Fibres can be used as a component of composite materials.
Fibres can also be matted into sheets to make products such as paper or felt. Fibres
are of two types, there are natural fibers and man made or synthetic fiber.
Natural fibres often referred to as vegetable fibres. Vegetable fibers generally
comprise cellulose examples include cotton, linen, jute, flax, ramie, sisal and hemp.
Cellulose fibers usually serve in the manufacture of paper and cloth. Synthetic fibre-
reinforced composites impart good long-term behavior to various aggressive
environments and an enhancement in strength and stiffness. However, it is found that
natural fibre-reinforced composites are more or less sensitive to humidity through
absorption of water, leading to physical degradation such as plasticization of the
matrix with water and the differential swelling between the fibres and the resin.
Pervaiz and Sain (2003) have presented strength data for sheet molded
polyolefin hemp fiber composites. They noticed an influence of the compression
ratio on the mechanical properties. These properties were found to be close to the
ones published in the literature for other natural fiber systems. In addition, the tensile
and impact strength of these materials were shown to be substantially lower than
their glass fiber counterparts. The composite properties are influenced by the fibre
properties. Natural fibre properties are highly variable and depend on conditions of
growth. It is therefore very difficult to get the same mechanical properties after
repeat testing. The fibre properties, such as dimensional instability, have been found
to improve after treatment with chemicals such as natrium hydroxide, acetic
anhydride and silanes. Though natural fibres� mechanical properties are much lower
than those of glass fibres specific properties, especially stiffness, are comparable to
the stated values of glass fibres. Moreover, natural fibres are about 50% lighter than
glass, and in general cheaper.
The mechanical properties of sisal, hemp, coir, kenaf and jute reinforced
polypropylene composites have been investigated by Paul et al. (2003) entitle natural
fibres replace glass in fibre reinforced plastics. Among all the fibre composites
tested, coir reinforced polypropylene composites registered the lowest mechanical
properties whereas hemp composites showed the highest. However, coir composites
displayed higher impact strength than jute and kenaf composites. The mechanical
properties of the natural fibre composites tested were found to compare favourably
with the corresponding properties of glass mat polypropylene composites. The
specific properties of the natural fibre composites were in some cases better than
those of glass. This result also show that the tensile strength and modulus increases
with increasing fibre volume fraction.
Another research has been presented by Manikandan Nair et al. (2001) on
thermal and dynamic mechanical analysis of polystyrene (PS) composites reinforced
with short sisal fibres. Found that the thermal stability of the composites higher than
that of sisal fibre and the PS matrix. The effects of fibre loading, fibre length, fibre
orientation and fibre modification on the dynamic mechanical properties of the
composites were evaluated. The thermal stability of PS/sisal composites is more
stable than unreinforced PS and sisal fibre. The addition of 10% fibre regard as
increased the modulus but the increase was found to level off at higher fibre
loadings. The Tg values of the composites were lower than that of unreinforced PS
and could be attributed to the presence of some residual solvents in the composites
entrapped during the composite preparation. The treated-fibre composites showed
improved properties than those of untreated-fibre composites.
2.3 Pineapple leaf fibre (PALF)
PALFs often referred to as vegetable fibres (extracted from the leaves) are
rough and sturdy and form part of the plant's transportation system and called leaf
fibres. PALF is obtained from the leaf of the plant Ananas cosomos belonging to
Bromeliaceae family. PALF was chosen because at present, it is a waste product of
pineapple cultivation and hence without any additional cost input, it can be harnessed
for industrial purposes. As these fibres are showing superior mechanical properties,
they have potential as reinforcing fillers in thermosets thermoplastics, and
elastomers. PALF are easily available and they possess excellent mechanical
properties. These fibers show high ultimate tensile strength and initial modulus
because they have high cellulose content and comparatively low microfibrillar angle.
Devi et al. (1997) reported that the main chemical constituents of pineapple
fibre are cellulose (70-82%), lignin (5-12%), and ash (1.1%). Table 2.3 shows the
physical and mechanical properties of PALF obtain from South India Textile
Research Association (SITRA), Coimbatore, India.
Table 2.3 The physical and mechanical properties of PALF from SITRA
Properties Value
Density (g/cm3) 1.526
Tensile Strength (MPa) 170
Young�s Modulus (MPa) 6260
Specific Strength (MPa) 110
Specific Modulus (MPa) 4070
Elongation at break (%) 3
Moisture regain (%) 12
The potentiality of pineapple leaf fibre as reinforcement in polyester
composite has been presented by Mishra et al. (2001). The study investigated the
mechanical properties like tensile, flexural and impact behavior of PALF-reinforced
polyester composites as a function of fibre loading and fibre surface modification.
The results of the study showed that a useful composite with good strength could be
successfully developed using different surface modified pineapple leaf fibres as a
reinforcing agent for the polyester matrix. The tensile strength and flexural strength
of these PALF-polyester composites increased linearly with the fibre weight fraction
up to 30 wt% and then decreased. The impact strength also increased linearly with
the weight fraction of the fibre. The composite with 30 wt% fibre content exhibited
impact strength of 80.29 J/m. The best improvement in tensile strength was observed
in the case of 10% AN-grafted PALF composite whereas cyanoethylated PALF
composite exhibited better flexural and impact strength.
Devi et al. (1997) have also made a research on PALFs reinforcement. The
research was about mechanical properties of PALFs reinforced polyester composites.
The research was to analyse the influence of fibre length, fibre loading and coupling
agent on mechanical properties of the composites. The result showed that the
optimum length of the fibre required was found to be 30mm. The stress-strain
behavior in tension revealed that neat polyester was brittle and the addition of fibers
made the matrix more ductile. The tensile strength and Young�s modulus of PALF
polyester composites increased linearly with the fiber weight fraction. But in the case
of flexural strength, there was a leveling off beyond 30%. The impact strength also
increased linearly with the weight fraction of the fiber. The high toughness of this
natural fiber polymer composite places it in the category of tough engineering
materials. A significant increase in the strength of the composites was observed after
treatment of the fibers. The best improvement was observed in the case of silane A-
172-treated fiber composites. The PALF composites exhibited superior mechanical
properties when compared to other natural-fiber polyester composites and can be
used as structural composites.
A research on short pineapple leaf fibre reinforced polypropylene (PP)
composite conducted by Weng (2005) showed that PALf has enhanced tensile
properties in Young�s modulus, flexural as well as impact properties of PP. The
study has demonstrated that the optimum fibre loading for peak performance was at
30 wt%. Fibre matrix interaction was well adhered and compatible with the use of
coupling agent at this concentration of fibre. Splitting, peeling and pull out of the
fibre was not obvious in the SEM micrographs for the 30 wt% but rather a more
corrugated fibre.
Another research which applied PALF in polymer composite has been
presented by Saniah Husin (2006). She investigated of the effect of different
coupling agent on the mechanical properties of pineapple leaf fibre reinforced
polypropylene composites. Two types of coupling agent were used in her research,
anhydride grafted polypropylene (MAPP) and vinyl trymethoxysilane (VTMO).
Results of the research showed that tensile and flexural properties were increased
with increasing percentage of coupling agent. However, adding coupling agent gave
poor impact properties of the composite. The optimum loading of coupling agent was
3 wt% and the better coupling agent for PALF reinforced PP was MAPP compared
to VTMO.
2.4 Natural Rubber
Nowadays, fibre reinforced rubber composites are of tremendous importance
both in end-use applications and in the area of research and development. Rubber is
used as the base material in a product if it requires rubber-like elasticity and
flexibility. In certain cases, rubber products require stiffness along with flexibility,
often in specific directions. This can be achieved by reinforcing rubbers with long or
short fibers to form composites. Fiber reinforced rubber composites are more
advantageous due to their easy processability and great flexibility in product design.
Beside that, the use of bonding agents can improve the mechanical properties and the
adhesion between the fibre surface and matrix. Table 2.4 shows the properties of
natural rubber (Geethamma, 2005):
Table 2.4 Properties of Natural Rubber
Properties Value
Dirt content (% by mass) 0.03
Volatile mass (% by mass) 0.50
Nitrogen (% by mass) 0.30
Ash (% by mass) 0.40
Initial plasticity number, Po 38
Plasticity retention index 78
Ismail et al. (1997) have investigated the curing characteristic and mechanical
properties of short oil palm fibre reinforced rubber composites. Modification of fibre
surface and use of various bonding systems increased the mechanical properties. The
presence of bonding agents in composites have prolonged the curing time. However,
scorch and curing time were found to be independent of fibre loading. Maximum and
minimum torque values increased with the presence of various bonding agents and
increasing fibre loading. The vulcanized with various type of bonding agent had
shown a higher mechanical properties compared to the control compound. It showed
that tensile strength increased when different types of bonding agent used in the
composites. The elongation at break for treated fibre has a lower value than untreated
fibre and also show higher torque value compared to untreated fibres. The elongation
at break shows reduction with increasing fibre loading. Increased fibre loading in
rubber matrix resulted in composites becoming stiffness and harder.
Ismail et al. (2002a) have also investigated the effect of a silane coupling
agent on curing characteristics and mechanical properties of bamboo fibre filled
natural rubber composites. The investigation showed that the scorch time, cure time
and mechanical properties viz. tensile strength, tear strength and elongation at break
decreased with increasing bamboo fibre loading. However, the Mooney viscosity,
hardness and tensile modulus showed apposite trend. The present of a coupling
agent, silane improved the adhesion between the fibre and rubber matrix and
consequently enhanced the mechanical properties of the composites.
In the same year, Ismail et al. (2002b) continued their research by studying
filler loading and bonding agent of bamboo filled natural rubber composites. The
curing characteristics and mechanical properties of bamboo fibre reinforced natural
rubber composites were examined as a function of fibre loading and bonding agent.
The scorch time, t2 and cure time, t90 decreased with increasing filler loading and the
presence of bonding agent. Tensile modulus and hardness of composites increased
with increasing filler loading and the presence of bonding agents. The adhesion
between the bamboo fibre and natural rubber can be enhanced by using of a bonding
agent.
Effect of chemical medication, loading and orientation of short coir fibres
reinforced natural rubber were studied by Geethamma et al. (1998). Different
chemical treatments were tried on coir fibre in order to improve its efficiency as
reinforcement in natural rubber composites. It was found that composites containing
alkali-treated coir fibres that had been subjected to a pretreatment with
depolymerized liquid natural rubber solution exhibit improved tear strength and fibre
orientation even though the tensile properties were marginally lower than those of
composites containing coir fibres treated with natural rubber (NR) and toluene
diisocyanate solutions (TDI). Tensile and tear testing have been performed to
evaluate the role of silica in the tricomponent HRH (hexa-resorcinol-hydrated silica)
dry bonding system. It was observed that silica was not an essential component in
producing good coir/rubber interfacial adhesion. The variation of tensile strength
with fibre loading was studied. The tensile strength decreased sharply up to 30 phr
and showed only a slight increase even at a high fibre loading of 60 phr. This
behaviour was explained on the basis of the shear flow that occurs during
compression moulding and the poor interfacial adhesion.
The processability characteristics and mechanical properties of sisal/oil palm
hybrid fiber reinforced natural rubber composites have been investigated as a
function of fiber loading, ratio and treatment (Jacob et al., 2004). Fiber breakage
analysis revealed that the extent of breaking was low. The mechanical properties of
the composites in the longitudinal direction are superior to those in the transverse
direction. Addition of sisal and oil palm fibers led to increase of tensile strength and
tear strength but increased modulus. The extent of adhesion between fiber and rubber
matrix was found to increase on alkali treatment of fibers. From the mechanical
properties the alkali treated fibers exhibited better tensile properties than untreated
composites. Processing characteristics were found to be independent of fiber loading
and modification of fiber surface. Swelling studies revealed that composites
containing bonding agents and alkali treated fibers showed higher crosslink density
and better adhesion. Anisotropic swelling studies indicated that the presence of short
fibers restricted the entry of solvent.
CHAPTER 3
METHODOLOGY
3.1 Introductions
This chapter is a combination of three basic stages:
Raw material preparation
Sample preparation
Testing
3.2 Raw Material Preparation
3.2.1 Preparation of Pineapple Leaf Fibre (PALF)
PALF is a waste pineapple leaves collected from Pekan Nenas, Johore. These
leaves were pressed using fibre extraction machine to remove 90% of the water
content. The extraction machine is shown in Figure 3.1. The fibres were then washed
thoroughly in water solution at room temperature. Basically, this cleaning step will
remove most of the foreign object and impurities inside the fibres. Then the fibres
were dried in an oven at 80 ºC for 24 hours before chemical treatment for further
processing.
Figure 3.1: The extraction machine
Prior to composite preparation, the fibres must be treated with chemical agent
such as sodium hydroxide (NaOH) (alkali) to remove natural and artificial impurities
which improves the adhesion between the matrix and fibre. It may also destroy the
hydrogen bonding in cellulose hydroxyl groups of the fibre, thereby making them
more reactive to the functional group of chemical agent, which in turn bond to the
polymer matrix.
The treated (T) fibres were prepared by immersing it in 5% aqueous alkali
(NaOH) in reflux equipment at 30°C for 1hour, washing with distillate water for
several times then followed by drying at 60 ºC for 24 hours. After dring, the fibres
were chopped into 10mm to 2mm length by using grinder.
3.3 Sample preparation
3.3.1 PALF-Rubber Composite Preparation
Natural rubber (SMR 10) was obtained from Malaysian Rubber Board
(MRB). Other chemicals were used as rubber�s basic recipe of vulcanization (Table
3.1). Base on an amount of rubber, different loadings of PALF and amount of
coupling agent were compounded in two roll mill at room temperature. Mixing was
carried out on a two roll-mill machine (Figure 3.2). Rubber compounds were
prepared on an open two-roll mill at room temperature.
Figure 3.2: The two roll mill machine
Vinyl trimethoxysilane(VTMO) was used as a coupling agent. The addition
of coupling agent into the compound was to improve the adhesion between the fibre
and rubber. The presence of coupling agent also gives shorter curing time and
enhanced mechanical properties.
The compounded composites were pressed by hot press machine to make
sheet with thickness of 2mm and 8mm according to the specification that are
Table 3.1 Different loadings of PALF and varying amount of silane
coupling agent in rubber composites.
Material Value (phr)
Natural Rubber (SMR 10) 100
Zinc oxide 5
Stearic acid 2
CBS(N-cyclo-hexyl-2-benzothiazole sulfenamide) 0.5
Sulfur 2.5
Silane Coupling Agent 0, 3, 5, 10
PALF 0, 5, 10, 15
required in testing sample. The operating temperature was use 150°C according to
the cure time of sample for 10 minutes.
3.3.2 Testing Sample Preparation
PALF-Rubber Composites sheet with thickness 2mm and 8mm were prepared
for tensile test specimens and hardness test specimens. All these samples were cut to
the shape that is required according to standards of testing sample. Dumbbell cutter
was used to get the dumbbell shaped according to ASTM D412 for tensile test
specimens, while, hardness test specimens were cut to bar shape.
3.4 Testing
There are two testing methods that were used in this study based on American
Standard Testing Methods (ASTM) namely Tensile Test (ASTM D412) and hardness
Test (ASTM D2240).
3.4.1 Tensile Test
Tensile tests measure the force required to break a specimen and the extent to
which the specimen stretches or elongates to that breaking point. According to
ASTM D412 and ASTM638, dumbbell-shaped type v is recommended for rubber
testing. Dumbbell-shaped samples were cut by dumbbell cutter. The dimensions of
the test sample are shown in Figure 3.2 and Table 3.2. Universal Testing Machine
(Lloyd UTM L1000S) was used for this tensile testing and was measured at room
temperature (25 ± 2˚C).
Figure 3.3: Dumbbell Shaped Specimen Dimension for type v in ASTM D638
Table 3.2: Dimension of the dumbbell shaped (Type v) tensile test sample
Dimension Value (mm)
Width of narrow section, W 3.18
Length of narrow section, L 9.53
Width overall, Wo 9.53
Length overall, Lo 63.5
Gauge length 7.62
Distance between grips, D 25.4
Radius of fillet, R 12.7
Thickness, T 2.0 ± 0.2
The sample was pulled at 500 ± 50mm/min with the gauge was kept at 38.1
mm. A sample has to be positioned vertically in the grip of the testing machine. The
grip were tightened evenly and firmly to prevent any slippage. Five samples for each
compounded were tested to get better curve. From this testing method, results that
obtained were tensile strength, yield strength and elongation at break. Below are the
basic relationships to determine these properties:
3.4.2 Hardness test
The hardness of the plastics is most commonly measured by the Shore
(Durometer) test. The method measures the resistance of plastics toward indentation
and provides an empirical hardness value that doesn't necessarily correlate well to
other properties or fundamental characteristics. According to ASTM D2240, the
shore type A is suitable for softer rubber. The surfaces of the specimen shall be flat
and the thickness is at least 6.0mm. Figures 3.4 and 3.5 show the Shore Durometer
and the type A indentor
Figure 3.4: The type A indentor
Figure 3.5: The Shore Durometer
The hardness value was determined by the penetration of the Durometer
indenter foot into the sample. Because of the resilience of rubbers, the indentation
reading may change over time. The result was obtained after 29 second. The results
obtained from this test are a useful measure of relative resistance to indentation of
various grades of rubber.
CHAPTER 4
RESULT AND DISCUSSIONS
4.1 Introduction
This chapter covers the mechanical properties of pineapple leaf fibre
reinforced rubber composite.
4.1.1 Effect of coupling agent
One of the objectives in this research was to study the effect of coupling
agent in pineapple leaf fibre (PALF) reinforced rubber composite. Vinyl
trimethoxysilane (VTMO) was used as a coupling agent. The coupling agent was
added to the rubber by varying the concentrations (0 phr, 3 phr, 5 phr and 10 phr).
The addition of coupling agent into the compound was to improve the adhesion
between fibre and rubber.
Figure 4.1 shows the effect of coupling agent on tensile strength and fibre
loading in rubber composites. At 0 phr coupling agent, the graph showed that
increasing the fibre loading reduced the tensile strength. The rubber composite
without fibre has higher tensile strength. This is because the rubber composite more
elastic than the rubber composites filled fibre. The addition of 3 phr coupling agent
in the rubber composites showed that the lowest the tensile strength was at 0 phr
fibre loading and increased significantly at 5 phr fibre loading. However, the tensile
strength slightly reduced by further increased fibre loading. When added 5 phr
coupling agent into rubber composite, the tensile strength slowly reduced with
increasing fibre loading. At 10 phr coupling agent, the tensile strength showed
almost similar value at all fibre loading.
It can be seen that at 5 phr and 10 phr fibre loading the best concentration of
couplimg agent to improve adhesion between fibre and rubber matrix was 3 phr.
Meanwhile, 5 phr of coupling agent was the best concentration for 15 phr fibre
loading. The lower tensile strength obtained at other concentration coupling agent
added that the adhesion between the fibre and the rubber matrix turn to be weak.
0
2
4
6
8
10
12
14
16
18
0 3 5 10Concentration of Coupling Agent (phr)
Ten
sile
Str
engt
h (M
Pa)
0 phr fibre 5 phr fibre 10 phr fibre 15 phr fibre
Figure 4.1: Tensile strength for various concentrations of coupling agent at various
fibres loading in rubber composites.
According to Ismail et al. (2002a), by modification with silane coupling
agent, the fibre/filler surface can be transformed into a hydrophobic with the ability
to bind active groups of coupling agents. Consequently, rubber chemisorptions on the
surface of filler would increase the tensile strength.
Figure 4.2 shows the hardness of composite for 0 phr and 3 phr of coupling
agent with increased in fibre loading. Obviously that addition of coupling agent were
increased the hardness. This means that coupling agent are essential for pineapple
leaf fibre (PALF) reinforced in natural rubber. The presence of coupling agent (silane
coupling agent) improved the adhesion between the fibre and matrix and
consequently enhanced the mechanical properties. This is in agreement with the
research reported by Ismail et al. (2002a).
0
10
20
30
40
0 5 10 15
Fiber Loading (phr)
Har
dnes
s (S
hore
Typ
e A
)
3 phr CA 0 phr CA
Figure 4.2: Hardness for various fibres loading in rubber composites.
4.1.2 Effect of fibre loading
The effect of fibre loading in fibre reinforced rubber composite has been
widely studied. Generally the tensile strength initially drops up to a certain amount of
fibre and then increased. The minimum volume of fibre is known as the critical
volume above which the fibre reinforced the matrix. However, figure 4.3 illustrate
that the tensile strength decreased abruptly at 5 phr fibre loading. When fibre loading
was increased further, this property decreased again slowly. The tensile strength of
the composite decreases due to the inability of the fibre to support stresses
transferred from the polymer matrix. This shows that the composite becoming stiffer
and harder. Meanwhile, the Young�s modulus increased with increasing fibre loading
in rubber up to 10 phr and reduced slightly with further loading. The improvement of
stiffness and hardness can be seen in figure 4.2 whereby the hardness was increased
by increasing fibre loading.
According to Ismail et al. (2002b), tensile modulus and hardness of fibre
reinforced rubber composites with and without coupling agent increases with
increasing fibre loading. These indicate that the incorporation of fibre into rubber
matrix enhanced the stiffness of the composites.
Jacob et al. (2004) have reported that natural rubber inherently possesses high
strength due to strain-induced crystallization. When fibres are incorporated into
natural rubber, the regular arrangement of rubber molecules is disrupted and hence
the ability for crystallization in lost. This is the reason why fibre reinforced natural
rubber composites possesses lower tensile strength than without fibre compound.
When fibre reinforced rubber composites is subjected to load, the fibre act as carriers
of load and stress is transferred from matrix along the fibres leading to effective and
uniform stress which result in a composite having good mechanical properties. The
value of elongation at break was reduced with increasing fibre loading. Increased
fibre loading in rubber matrix resulted in composites becoming stiffer and harder.
This will reduce the composite�s resilience and toughness and lead to lower
elongation at break.
1
3
5
7
9
11
13
15
0 5 10 15
Fibre Loading (phr)
Ten
sile
Str
engt
h (M
Pa)
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
You
ng's
Mod
ulus
(M
Pa)
Tensile Strength Young's Modulus
Figure 4.3: Tensile strength and Young�s modulus at 5 phr of coupling agent by increased fibre loading.
Figure 4.4 shows that the elongation at break of the rubber composites was
reduced with increasing fibre loading, however, the value was quite similar for each
fibre loading.
0
200
400
600
800
1000
0 5 10 15
Fibre Loading (phr)
Elo
ngat
ion
at B
reak
(%)
0 phr CA 3 phr CA 5 phr CA 10 phr CA
Figure 4.4: Elongation at break by increased fibre loading
4.1.3 Effect of fibre treatment
Figure 4.1-4.4 shows the mechanical properties of treated PALF rubber
composite. Therefore, to identify whether treated better than untreated or not, Figure
4.5-4.7 were indicated the result. The main reason for fibre treatment was to obtain
excellent fibre reinforcement in rubber composite by improved the adhesion between
the rubber and the fibre. In this research, sodium hydroxide was used to treat PALF.
Figure 4.5 illustrates that treated fibre exhibit higher tensile strength than untreated
after 5phr fibre loading. This showed that filled treated fibre into rubber composites
improved the adhesion between the fibre and the rubber matrix. The improvement
also can be seen in figure 4.5 and 4.6 which treated fibre has higher hardness and
Young�s modulus than untreated fibre.
It is obvious that the aqueous alkali treatment of PALF improves the fibre
adhesion to rubber matrices. Ismail el al. (2002a) reported that the surface of fibre
can be modified by aqueous alkali treatment at elevated temperature and this was
found to improve its adhesion properties significantly. Murty and De (1982) also
reported that the modulus increases when the fibre loading is increased for natural
rubber-jute, SBR-jute, SBR-glass and natural rubber-glass composite.
0
2
4
6
8
10
12
14
16
0 5 10 15
Fibre loading (phr)
Ten
sile
Str
engt
h (M
Pa) Untreated Treated
Figure 4.5: Tensile strength for treated and untreated PALF
0
5
10
15
20
25
30
35
40
0 5 10 15
Fibre Loading (phr)
Har
dnes
s (S
hore
Typ
e A
)
Treated Untreated
Figure 4.6: Hardness for treated and untreated PALF.
0
0.5
1
1.5
2
2.5
0 5 10 15
Fibre Loading (phr)
You
ng's
Mod
ulus
(MP
a)
Untreted Treated
Figure 4.7: Young�s modulus for treated and untreated PALF.
CHAPTER 5
CONCLUSION
5.1 Conclusions
The results of the present study showed that a useful composite with good
strength could be successfully developed using PALF as reinforcement material for
the rubber matrix. Several conclusions can be drawn regarding the effect of fibre
loading, addition of coupling agent and fibre treatment on the mechanical properties
of PALF composite.
The effect of Fibre loading in rubber composite can be demonstrated by the
decreased in tensile strength abruptly at 5 phr. When fibre loading was further
increased, this property decreased again slowly. The tensile strength of the composite
decreased due to the inability of the fibre to support stresses transferred from the
polymer matrix. Meanwhile, the Young�s modulus increased with increasing fibre
loading in rubber up to 10 phr and reduced slightly with further loading. The
improvement of stiffness and hardness also can be seen when the hardness was
increased by increasing fibre loading.
The addition of coupling agent into rubber composite also exhibited
improvement. At 5 phr and 10 phr fibre loading the best concentration of couplimg
agent to improve adhesion between fibre and rubber matrix was 3 phr. Meanwhile, 5
phr of coupling agent was the best concentration for 15 phr fibre loading. The lower
tensile strength obtained at other concentration coupling agent added that the
adhesion between the fibre and the rubber matrix turn to be weak. The addition of
coupling agent was also increased the hardness.
Treated fibre reinforced to rubber composite showed better result in
mechanical properties than untreated fibre. The improvements in mechanical
properties occurred because of the adhesion between the fibre and the rubber matrix
has improved.
Finally to summarize everything, reinforcement of PALF has improved the
mechanical properties of rubber composite. The rubber composite has promoted
better mechanical properties by treating the fibre and adding coupling agent.
5.2 Recommendation and future work
Further research should be conducted in future in order to improve the
present result and to be more applicable. The suggestions are as follows:
(i) Chemical properties can be studied besides mechanical properties.
(ii) Besides silane coupling agent, others coupling agent should be used
and compare.
(iii) The amount of fibre loading can be increased up to50 or 60 phr to
obtain the optimum fibre in rubber composites.
(iv) Other effects should be investigated such as fibre orientation and fibre
ratio.
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APPENDIX
APPENDIX A
