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THE EFFECT OF OIL PALM TRUNK FILLER IN EPOXIED NATURAL RUBBER
MOHD SAIFUL AFFENDI BIN ZABIDI
A thesis submitted in fulfillment
of the requirements for the award of the Degree of
Bachelor of Chemical Engineering
Faculty of Chemical Engineering & Natural Resources
Universiti Malaysia Pahang
NOVEMBER 2010
iv
ABSTRACT
The effect of loading oil palm trunk as filler in natural rubber was investigated in
this research. The testing that will be made on the reinforced fiber rubber are tensile
strength test and swelling test. The natural rubber is obtained from Rubber Research
Institute Malaysia (RRIM). There are three types of rubber in this research. They are
Epoxied Natural Rubber (ENR), Standard Malaysian Rubber (SMR), and Styrene-
Butadiene Rubber (SBR). The selected ENR will be milled on the two roll mill machine
and mix with filler after the milling process. The filler will be divided into five different
of parts per hundred rubbers (phr). The compounds will be vulcanized with sulfur and
ready to be molded. The molded rubber will be tested. The machines that will be used in
this research are two roll mill for compounding and hot press machine for molding. Two
roll mills will operate for 3 hours per compound. The hot press machine will be used for
25 minutes each molding sessions. Conventional filler is the carbon black filler. Oil
palm trunk is used as filler to compare with carbon black filler in terms of rubber
properties. It was found out that the higher the amount of oil palm trunk in rubber, the
lower the tensile strength of the rubber. The swelling of rubber product is higher in
kerosene compare with diesel. When the filler content increase, the mixing time will be
increased.
v
ABSTRAK
Pengaruh bebanan fiber batang pokok kelapa sawit diuji di dalam kajian ini.
Antara ujian yang dilakukan pada getah pencampuran fiber adalah ujian kekuatan
tegangan dan ujian pengembangan. Getah asli didapati dari Lembaga Getah Malaysia.
Terdapat tiga jenis getah yang terdapat di dalam kajian ini iaitu Getah asli epoxied
(ENR), Getah asli standard Malaysia (SMR) and Getah sintetik (SBR). ENR yang telah
dipilih akan dileperkan menggunakan two roll mill and dicampur dengan pengisi setelah
proses penleperan selesai. Pengisi dibahagikan kepada lima bahagian per seratus getah
(phr). Campuran tersebut akan divulknanisasi dengan sulfur dan bersedia untuk dibentuk
mengikut acuan. Campuran tersebut akan diuji. Peralatan yang digunakan adalah two
roll mill untuk pencampuran dan hot press machine untuk pembentukan. Two roll mill
akan beroperasi untuk 3 jam setiap sampel. Hot press machine pula beroperasi untuk 25
minut setiap sampel. Pengisi konventional ialah karbon hitam. Dari segi sifat getah, fiber
batang pokok kelapa sawit digunakan dan dibandingkan dengan pengisi karbon hitam.
Semakin tinggi fiber batang pokok kelapa sawit, semakin rendah kekuatan tegangan
getah tersebut. Dalam ujian pengembangan, getah yang direndam dalam minyak tanah
lebih kembang berbanding rendaman dalam minyak diesel. Semakin tinggi kandungan
fiber batang pokok kelapa sawit, semakin tinggi masa untuk pencampuran.
vi
TABLE OF CONTENTS
CHAPTER TITLE PAGE
TITLE PAGE i
DECLARATION ii
ACKNOWLEDGEMENT iii
ABSTRACT iv
ABSTRAK v
TABLE OF CONTENT vi
LIST OF FIGURES x
LIST OF TABLES xii
LIST OF APPENDICES xiii
LIST OF ABBREVIATIONS xiv
1 INTRODUCTION
1.0 Background 1
1.1 Problem Statement 3
1.2 Objective 3
1.3 Scope of study 4
1.4 Rational & Significance 4
2 LITERATURE REVIEW
2.1 Introduction 5
2.1.1 History 5
2.2 Types of Rubber 6
2.2.1 Natural Rubber 6
vii
2.2.2 Epoxied Natural Rubber 7
2.2.3 Styrene Butadiene Rubber 8
2.2.4 Cross-linked rubber 9
2.2.5 Polybutadiene Rubber 10
2.2.6 Ethylene-Propylene-Diene 11
2.3 Filler 12
2.3.1 Particle Size 13
2.3.2 Surface Area 13
2.3.3 Structure 13
2.4 Types of Fillers 14
2.4.1 Carbon Black 14
2.4.1.1 N550 17
2.4.1.2 N660 17
2.4.2 Oil Palm Fibre 18
2.4.3 Coconut Fibre 19
2.5 Rubber Processing 20
2.5.1 Masticating 20
2.5.2 Compounding 21
2.5.3 Vulcanization 22
2.5.4 Molding 23
2.5.4.1 Extrusion 23
2.5.4.2 Compression Molding 24
2.5.5 Testing 25
2.5.5.1 Tear strength 25
2.5.5.2 Tensile strength 26
2.5.5.3 Hardness 28
2.5.5.4 Scanning Electron Microscope 29
2.5.5.5 Swelling test 29
viii
3 RESEARCH METHODOLOGY
3.1 Introduction 30
3.2 Raw Material & Chemical Used 32
3.2.1 Epoxied Natural Rubber 34
3.2.2 Oil Palm Trunk Filler 35
3.2.3 Sulphur 36
3.2.4 Zinc Oxide and Stearic Acid 37
3.2.5 CBS 38
3.2.6 6PPD 39
3.3 Rubber Formulation 40
3.4 Equipment Used 42
3.4.1 Two Roll Mill 42
3.4.2 Hot Press Machine 43
3.4.3 Universal Tensile Machine 44
3.5 Experimental preparation 45
3.6 Testing 45
3.6.1 Swelling Test 46
3.6.2 Tensile Test 47
4 RESULT & DISCUSSIONS
4.1 Introduction 48
4.2 Tensile test 49
4.2.1 0 phr of filler loading 49
4.2.2 15 phr of filler loading 50
4.2.3 30 phr of filler loading 51
4.2.4 40 phr of filler loading 52
4.2.5 50 phr of filler loading 53
4.2.6 Ultimate Tensile Strength 54
4.2.7 % Elongation 55
4.2.8 Young’s Modulus 56
ix
4.3 Swelling Test 57
4.3.1 % swelling of ENR in diesel 57
4.3.2 % swelling of ENR in kerosene 58
4.3.3 Comparison between ENR’s swellings in each
solvent
59
4.4 Mixing Process 60
4.4.1 Mixing Time 60
5 CONCLUSION & RECOMMENDATIONS
5.1 Conclusion 61
5.2 Recommendations 62
REFERNCES 63
APPENDIX A 67
APPENDIX B 70
x
LIST OF FIGURE
FIGURE NO TITLE PAGE
Figure 2.1 Structure of natural rubber 7
Figure 2.2 Structure of SBR 8
Figure 2.3 Cross-linked Reaction 9
Figure 2.4 Chemical structure of PBR 10
Figure 2.5 Structure of EPDM containing ENB 11
Figure 2.6 Categories of Fillers 12
Figure 2.7 Production of Carbon Black 16
Figure 2.8 Mechanical Properties of Oil Palm Fibre 18
Figure 2.9 SEM of Coir Fibre 19
Figure 2.10 Example of Rubber Compounding 21
Figure 2.11 Schematic diagram of an extruder 23
Figure 2.12 Schematic diagram of compression molding 24
Figure 2.13 Example of tear strength result 26
Figure 2.14 Typical tensile test machine 27
Figure 2.15 Example of natural rubber tensile test result 27
Figure 2.16 Hardness test 28
Figure 2.17 Schematic presentations of rubber vulcanizates 29
Figure 3.1 Process flow of producing rubber products 31
Figure 3.2 Chemicals in Stage 1 33
Figure 3.3 Chemicals in Stage 2 33
Figure 3.4 Natural Rubber in bulk size 34
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Figure 3.5 Oil Palm Trunk filler 35
Figure 3.6 Sulphur photo 36
Figure 3.7 Chemical structure of sulphur 36
Figure 3.8 Chemical structure of Zinc Oxide 37
Figure 3.9 Chemical structure of Stearic Acid 37
Figure 3.10 Chemical structure of CBS 38
Figure 3.11 Chemical Structure of 6PPD 39
Figure 3.12 Laboratory Two Roll Mill 42
Figure 3.13 Hot & Cold Molding Press Machine 43
Figure 3.14 Universal Tensile Machine 44
Figure 3.15 Swelling test 46
Figure 3.16 Sample at initial of testing 47
Figure 3.17 Sample at during of testing 47
Figure 3.18 Sample at after of testing 47
Figure 4.1 Graph of stress vs. strain for 0 phr of filler loading 49
Figure 4.2 Graph of stress vs. strain for 15 phr of filler loading 50
Figure 4.3 Graph of stress vs. strain for 30 phr of filler loading 51
Figure 4.4 Graph of stress vs. strain for 40 phr of filler loading 52
Figure 4.5 Graph of stress vs. strain for 50 phr of filler loading 53
Figure 4.6 Graph of tensile strength vs. filler content 54
Figure 4.7 Graph of % elongation vs. filler content 55
Figure 4.8 Graph of Young’s modulus vs. filler content 56
Figure 4.9 Graph of % Swelling vs Filler Content (diesel) 57
Figure 4.10 Graph of % Swelling vs Filler Content (kerosene) 58
Figure 4.11 Graph of % Swelling vs Filler Content in each solvent 59
Figure 4.12 Graph of mixing time vs. filler content 60
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LIST OF TABLE
TABLE NO TITLE PAGE
Table 2.1 Types of carbon black used 15
Table 3.1 Additives and its function 32
Table 3.2 Formulation of rubber product by parts 40
Table 3.3 Formulation of rubber product by weight 41
xiii
LIST OF APPENDICES
APPENDIX CONTENT PAGE
A List of Calculation 67
B Data For Tensile Strength & % Elongation 70
xiv
LIST OF ABBREVIATIONS
ABBREVIATIONS FULL NAME
CBS n-cyclohexyl-2-benzothiazyl sulphenamide
6PPD N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylene-diamine
ENR Epoxied Natural Rubber
PHR Part per Hundred Rubber
CHAPTER 1
INTRODUCTION
1.0 Background
Carbon black is the predominant filler that is being widely used in reinforcing the
rubber compound. Surface area to volume ratio of carbon black is rather low compared
to activated carbon. Usually it will increase the thermal properties, the rubber
vulcanizates’ elastic modulus, tensile strength as well as the increasing of hysteresis.
Hysteresis represents the history dependence of physical systems (James P. Sethnaet al,
1999). If the rubber was applied with force, it will bounce back to its initial properties.
Generally, this research is to predict the elasticity of a kind of rubber when it is being
reinforced by carbon black. Most studies in the experimental are emphasis on (1) the
reinforcement obtained within a matrix, (2) The interaction between rubber and the filler
and (3) the agglomerate structure (B. Omnes et al., 2008).
In the past, many researchers have conducted various types of experimental
works in order to find out the characteristics and the effects of carbon black loaded
rubber. There are various types of carbon black existed in the industry. The carbon black
2
examples are such as, N220, N300 and N990. The differences between these
carbon blacks are their particle size. In order to choose the best rubber that can be built,
we must select the best carbon black in order to increase the strength and elasticity of the
rubber. There are other type of fillers in the industry such as oil palm and bamboo filler.
In this research, the carbon black has been chosen as the main material in order to run
this research.
Natural fibres has widely used in the industry nowadays. The selection of natural
fibres is wide. This is depending on the product that need to be produced and the
demand of the market. Converting from waste to wealth is a bonus to researchers
nowadays. From a waste such as vehicles tire can be converted to rubber product again
using several methods that are available. The raw material is cheap and recycled product
can be used in the society. Thus, the environmental waste is reduced.
Of course, the properties of rubber product reinforced by natural fibres must be
equal or better than the current rubber product in the market. To make sure the product is
competitive to be market; the formulation of producing the product is an important
factor to make sure the product is saleable.
3
1.1 Problem Statement
This research has been conducted due to the increase of price of rubber products
in the market. This is because the price of the product mostly based on the production
cost itself. By cheapening the cost of production, we can reduce the price of rubber
products. On the other hand, new formulation is needed to be created. This is where we
are using less amount of natural rubber but at the same time, we are going to maintain its
crucial properties such as tensile strength and tear strength. In addition, the research on
this topic has not been widely conducted around the world. This is to help the industry to
have a better selection on the natural fillers. With this research, the advantages and
disadvantages of the selected natural fibre could be determined.
In addition, the processability will determine whether the method is usable or
not. This is because, processing errors may occur during the manufacturing the rubber
product.
1.2 Objective
To load various parts of oil palm trunk fillers in epoxied natural rubber to
determine the strength and elongation of the rubber product.
.
4
1.3 Scope of study
This research consists of several main scopes:
To use oil palm trunk as the filler for rubber
Use only epoxied natural rubber as the main raw material
Tensile strength, and swelling will be the testing of this research
Tensile strength of each rubber product will be studied
1.4 Rational & Significance
Several significances will be found during conducting the research. One of them
is the price of rubber product will be decreased. During the running of research, new
formulation will be created and the parts of natural rubber will be less in it. Thus, the
price of rubber products will be decrease. On the other hand, higher quality of rubber
products will be produced. Lastly, the processability will be determined whether this
method is usable or not. We can see throughout the research whether this method is
suitable or not to run this research.
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
Our everyday life has a strong connection with rubber. Most of our equipment is
made of rubber inclusive of natural rubber and synthetic rubber. It is the statement that
can say that, without rubber our life is not smooth to run its daily schedule. Malaysia is
among the biggest producer of natural rubber in the world. The first person to found out
rubber is Charles Marie de La Condamine where he found rubber in the year of 1736.
2.1.1 History
In the past, rubber is among the most valuable product that can be found in the
forest. It is stated that rubber originally came from South America. Mostly are from
Brazil. In 1839, Charles Goodyear accidentally dropped rubber and sulfur on a hot
stovetop, causing it to char like leather yet remain plastic and elastic (Wade Davis,
6
1996). This process is called vulcanization. This is where the rubber has been cross
linked with sulfur.
2.2 Types of Rubber
2.2.1 Natural Rubber
The most common form of rubber is in liquid form which is latex. The chemical
name of this rubber is poly-isoprene. Natural rubber can be gathered from the rubber
tree. The name of this tree is called Heveabrasiliensis. It is also the only non-synthetic
elastomer where it is being widely used in the industry. Low temperature can cause
natural rubber to be crystallized spontaneously. Because of this, the effect of
crystallization can cause stiffness. This process can be reverse by warming up the
natural rubber.
Natural rubber has properties such as poor resistance to ozone, high temperatures
and also concentrated acids and bases. In order to overcome these types of problems,
synthetic rubber is usually mixed with natural rubber. The reasons why this natural
rubber is mixed with other type of ingredients is to increase component-to-component
adhesion, improving the tear strength of the natural rubber, and lower tire rolling
resistance to improve vehicle fuel efficiency (James E. Mark et al, 2005). The crucial
property of natural rubber is the elasticity. This is because the natural rubber can be
distorted and it can recover to its original shape. NR is not oil resistant and is swollen by
aromatic, aliphatic and halogenated hydrocarbons. It is resistant to many inorganic
chemicals, but not to oxidizing acids and had limited resistance to mineral acids. It is
unsuitable for use with organic liquids in general, the major exception being alcohols of
low molecular weight. (Richard Simpson, 2002)
7
Figure 2.1 Structure of natural rubber taken from (Robin Bartoletti, 2005)
2.2.2 Epoxied Natural Rubber
Epoxied Natural Rubber (ENR) is prepared by chemically introducing epoxied
groups randomly onto the NR molecule. This chemical modification leads to increased
oil resistance, greater impermeability to gases, but an increase in the glass transition
temperature, Tg, and damping characteristics; the excellent mechanical properties of NR
are retained.
As stated by M.Pire et al, 2010, the ENR remains the properties of natural rubber
while having double functionality for cross-linking. It has the double bond and epoxy
sites in the ENR. The degree of epoxidation increases, the glass transition temperature,
Tg, increase and lastly the resilience is decrease.
8
2.2.3 Styrene Butadiene Rubber
Synthetic rubber is another form of rubber where it is produced to replace mainly
on the function of natural rubber. This is because the synthetic rubber has a better
pricing where it is cheaper than the natural rubber. On the other hand, synthetic rubber is
made from polymerization process. Synthetic rubber consumption is mostly in tires
where it is around 60% of usage. The most common synthetic rubber that is being
widely used is styrene butadiene rubber, is currently called SBR. SBR is a synthetic
rubber that reacted from a reaction styrene and butadiene. In tire industry, SBR is added
with natural rubber to increase abrasion resistance and it also has good aging stability. In
most of the cases, SBR is representing around 65% of the total usage of synthetic rubber
used in tires. The process of SBR compounds are similar to the processing of natural
rubber and additives are used. SBR is compounded with better abrasion and crack
initiation than natural rubber. SBR products are smoother and maintain their shape better
compared with natural rubber products.
Figure 2.2 Structure of SBR taken from (Luigi Chiesa, 2008)
9
2.2.4 Cross-linked rubber
Cross-linked are bonds that linked one polymer chain to another. In rubber, the
cross linked agent is the sulphur. Sulphur links polyisoprene chain from the upper to the
lower chain. It is working as a bridge cross-linking agent. The cross linking of the
elastomeric polymer is achieved by an irreversible chemical reaction usually at high
temperatures. Increasing the amount of cross-link agent will favour shorter cross-links.
Figure 2.3 Cross-linked Reaction taken from (Nick Greeves et al, 2008)
10
2.24 Polybutadiene Rubber
By using emulsion process or solution process, polybutadiene can be produced.
Polybutadiene rubber is resistance to cold and also excellent in flex properties. This is
the reason polybutadiene rubber is useful in blends of two or more polymers. The reason
polybutadiene rubber is mixed with fillers are: (1) lack of toughness, (2) lack of
durability and (3) cut growth resistance of the latter. The polybutadiene rubber should
not blend with polar elastomer. Commonly, polybutadiene rubber is mixed with NR or
SBR in order to improve the low temperature flexibility of NR and SBR. Despite its
unsaturation, polybutadiene have a fair resistance to oxidation. (R. School., 2001).
Figure 2.4 Chemical structure of PBR taken from (International Institute of Synthetic
Rubber Producers, Inc., 2002)
11
2.2.5 Ethylene-Propylene-Diene
Ethylene-Propylene-Diene (EPDM) is categorized under specialty elastomer and
it is widely used in automotive industries, wire-and-cable covers and many other fields.
The main attributes that makes it become special is its resistance to ozone. EPDM can be
highly loaded with low cost fillers such as clays and silica. This features makes
compounders can rely on EPDM to produce rubber products.
The process of curing EPDM can be done using sulphur or peroxides. Using
peroxides as the curing agent would produce products that will meet high heat required
application. On the other hand, the resistance of EPDM to aliphatic, aromatic and
chlorinated hydrocarbon is very poor. To overcome this problem, the reinforcing agent
is added to the process will provide the solution. This is where the reinforcing agent is
absorbing the poor resistance of EDPM.
EPDM require reinforcing agent to overcome lack of gum strength. As the
loading of reinforcing agent increases, the tensile and tear properties increase. (R.
School., 2001).
Figure 2.5 Structure of EPDM containing ENB taken from (R.Karpeles et al., 2001)
12
2.3 Filler
Fillers are things which added into material in order to improve some mechanical
properties of a material. Fillers are needed in the rubber compound as it strengthens the
rubber itself. There are two types of fillers. They are carbon black and non-carbon black.
On the other hand, fillers are compounding ingredients added to a rubber compound for
the purpose of either reinforcing or cheapening the compound. For non-carbon black
fillers, there are several examples of them. They are fumed silica, clay, ground or
precipitated calcium carbonate, titanium dioxide, wood flour, glass, limestone and talc.
Fillers will also improve processability, and durability of rubber products. On the other
hand, fillers can be used to alter electrical properties, improve heat, tear and moisture
resistance. There are several properties of fillers that needed to check before insert it into
the rubber. They are particle size, surface area, and structure (Peter A. Ciullo, 1999)
Figure 2.6 Categories of Fillers
Filler
Black Filler Carbon Black
Non-black Filler
Chemical Filler
Calcium Carbonate
Natural Filler
Coconut Fiber
Oil Palm Fiber
13
2.3.1 Particle Size
Fillers with higher number of particle size can reduce the performance rather
than reinforce or extend. The fillers can be classified into 3 classifications. The
classifications are non-reinforcing, Semi- reinforcing and reinforcing. The carbon black
fillers can be in various particle sizes where the carbon black can be semi – reinforcing
and reinforcing.
2.3.2 Surface Area
Fillers that have higher surface area have more contact area with the rubber chain
thus contributing to higher potential of reinforcing the rubber chain. Particles of carbon
black are usually spherical. Carbon black has the better more surface area per unit
weight rather than other type of fillers. Thus, this statement shows that carbon black has
a better contribution to reinforce rubber.
2.3.3 Structure
The structure of fillers plays essential part in reinforcing the rubber. High
structure filler has aggregates favouring high particle count. The increase of structure
size improves dispersibility but lowers blackness. Carbon black with a larger structure in
particular shows an excellent conductive property. In addition, the reinforcing potential
will be higher if the structure is larger in size.
14
2.4 Types of Fillers
2.4.1 Carbon Black
Carbon Black is the most common filler that is being used in the industry. There
are several processes to produce carbon black. The most and widely used process is the
furnace process. The other type of process is to Carbon blacks are produced by
converting either liquid or gaseous hydrocarbons to elemental carbon and hydrogen by
partial combustion or thermal decomposition. On the other hand, the oldest method for
producing the carbon black is using the lampblack process. The lampblack process is
consists of a flat cast-iron pan which contain the liquid feedstock. The feedstock
required is aromatic oil mainly based on coal tar (Gerhard Kühner et al, 1993). It is also
can be stated as method obtains carbon black by collecting soot from fumes generated
by burning oils or pine wood. The range of carbon black is from the smallest N110 to
the largest N991. The differences between these carbon blacks are their particle size. For
the smallest carbon black is average 17nm while the largest carbon black is average
300nm.
