mechanical properties of styrene butadiene rubber

MECHANICAL PROPERTIES OF STYRENE BUTADIENE RUBBER WITH

OIL PALM TRUNK FIBER AS FILLER

MOHD HAZIZUL BIN HAMZAH

A thesis submitted in fulfillment of the requirements for the award of the Degree of

Bachelor of Chemical Engineering

Faculty of Chemical & Natural Resources Engineering

Universiti Malaysia Pahang

DECEMBER 2010

vi

ABSTRACT

Synthetic rubber on the other hand is a rubber which is synthesized chemically.

Styrene-butadiene rubber is one of them. The synthetic rubber gives different properties

from natural rubber in every aspect. The objectives of this research are to investigate the

mechanical properties changes in styrene butadiene rubber (SBR) filled with oil palm

trunks as fillers and to check the differences in properties between the amounts of fillers

used. The purpose of this research is to investigate the properties of styrene butadiene

rubber blending with oil palm trunk fiber as filler. The research is based on experimental

lab research. The contribution of oil palm trunk as a filler in rubber compound will

decrease the burning activities and reducing environmental issues. Many researches have

been done in rubber/natural filler blending in order to improve the properties of rubber

with economically. The methods in this research are divided into three sections; mixing,

molding, and testing. Mixing required two roll mills as a device blending rubber with

filler, accelerator and vulcanizing agent. Molding required hot and cold press molding to

form a sheet of product before testing. Testing required a universal testing machine to test

the tensile properties of the rubber blend. Two chemical used in this swelling test;

kerosene and diesel. The samples were put into two different bottles with kerosene inside

one bottle and diesel inside another bottle. The time taken to complete the test was 24

hours – exactly one day. The result from testing showed that increasing amount of fillers

will actually decrease the tensile strength, increase the tensile modulus and increase

swelling behavior of the rubber blend. As conclusion, most of mechanical properties

decrease with increasing of filler content. As recommendation, increasing the filler

content might give the better result, and giving more information about capability of

styrene butadiene rubber to consume more filler.

vii

ABSTRAK

Getah sintetik di sisi lain adalah getah yang merupakan hasil campuran bahan

kimia. Getah stirena butadiena adalah salah satunya. Getah sintetik memberikan sifat

yang berbeza dari getah asli dalam setiap aspek. Tujuan kajian ini adalah untuk

mengetahui perubahan sifat mekanik dalam getah stirena butadiena (SBR) yang diisi

dengan batang kelapa sawit sebagai suapan dan untuk menyemak perbezaan sifat antara

jumlah suapan digunakan. Tujuan dari penelitian ini adalah untuk mengetahui sifat-sifat

campuran getah stirena butadiena dengan serat batang kelapa sawit sebagai suapan.

Penelitian ini berdasarkan pada penelitian ujikaji makmal. Sumbangan batang kelapa

sawit sebagai isian dalam campuran getah akan menurunkan kegiatan pembakaran dan

mengurangkan masalah alam sekitar. Banyak kajian telah dilakukan dalam

getah/pencampuran isian asli meningkatkan sifat getah dengan ekonomi. Kaedah dalam

kajian ini dibahagikan kepada tiga bahagian; pencampuran, pencetakan, dan ujian.

Mencampur memerlukan “two roll mill” sebagai campuran getah peranti dengan isian,

pencepat dan agen vulcanizing. Pencetakan memerlukan “hot and cold molding press”

untuk membentuk sehelai produk sebelum ujian. Ujian memerlukan mesin uji universal

untuk menguji sifat tarik dari getah campuran. Dua kimia yang digunakan dalam ujian

pembengkakan ialah minyak tanah dan diesel. Bahan uji dimasukkan ke dalam dua botol

yang berbeza dengan minyak tanah dalam satu botol dan diesel dalam botol lain. Waktu

yang diperlukan untuk menyelesaikan ujian adalah 24 jam - persis satu hari. Hasil dari

ujian menunjukkan bahawa peningkatan jumlah suapan benar-benar akan menurunkan

kekuatan tarik, meningkatkan modulus tarik dan meningkatkan perilaku pembengkakan

getah campuran. Sebagai kesimpulan, sebahagian besar sifat mekanik menurun dengan

peningkatan kadar isian. Sebagai cadangan, meningkatkan kadar isian dapat memberikan

hasil yang lebih baik, dan memberikan maklumat lebih lanjut tentang kemampuan getah

stirena butadiena untuk mengambil lebih banyak isian.

viii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF APPENDICES xiv

LIST OF ABBREVIATIONS xv

1 INTRODUCTION

1.1 Background of Study 1

1.2 Problem Statements 2

1.3 Objectives of the Research 3

1.4 Scope of Study 3

1.5 Rationale and Significance 4

2 LITERATURE REVIEW

2.1 Styrene Butadiene Rubber 5

ix

2.2 Natural Filler 6

2.3 Oil Palm Trunk Fiber 6

2.4 Crosslink 7

2.5 Vulcanization 7

2.6 Mechanical Properties 8

2.6.1 Tensile Strength 8

2.6.2 Tensile Modulus 10

2.6.3 Swelling 12

2.6.4 Elongation 13

2.7 Recycled Elastomer 14

2.8 Carbon Black Filler 16

2.9 Organoclay 19

3 METHODOLOGY

3.1 Chemical and Apparatus 20

3.2 Rubber Formulation 21

3.3 Sieving 22

3.4 Blending 23

3.5 Molding 24

3.6 Tensile Test 25

3.7 Swelling Test 26

3.8 Precaution Steps 27

4 RESULTS AND DISCUSSIONS

4.1 Result 28

4.1.1 Tensile Test 28

4.1.2 Swelling Test 29

4.2 Discussion 30

4.2.1 Time to Break 30

4.2.2 Tensile Strength 31

4.2.3 Extension at Break 32

x

4.2.4 Stress-Strain Relationship 35

4.2.5 Tensile Modulus 39

4.2.6 Swelling 41

5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 44

5.2 Recommendation 45

REFERENCES 46

APPENDICES 49

xi

LIST OF TABLES

TABLE TITLE PAGE

3.1 Part per hundred Rubber Formulations 21

3.2 Ingredient weight value based on 250 grams per sample 22

3.3 Rubber Stages during Blending 23

3.4 Result available for rubber tensile test at Universal Tensile Machine 25

4.1 Result in tensile test 28

4.2 Result in swelling test 29

xii

LIST OF FIGURES

FIGURE TITLE PAGE

2.1 Oil palm trunk fiber 6

2.2 Tensile strength-rice husk content relationship (A.I. Khalf et al.,

2010) 8

2.3 Tensile strength of natural rubber reinforced with various fillers (N.

Rattanasom et al., 2009) 9

2.4 Tensile strength of rubber-filler content relationship (Hanafi Ismail

et al., 1996) 10

2.5

Tensile modulus of white rice husk ash loading in natural

rubber/linear low density polyethylene blends (Hanafi Ismail et al.,

2000)

11

2.6 Modulus at 100% elongation according to fiber loading (Hanafi

Ismail et al., 1999) 12

2.7 Swelling behavior of recycled rubber powder filler on natural rubber

(Hanafi Ismail et al., 2001) 13

2.8 Elongation at break versus fiber loading in sisal/oil palm hybrid

fiber reinforced natural rubber (Maya Jacob et al., 2003) 14

2.9

Horizontal profile of liquid axial velocity in downcomer for three

The tensile strength of SBR/NBRr with/without ENR-50 (Noriman

et al., 2009)

15

2.10 The tensile modulus of SBR/NBRr with/without ENR-50 (Noriman

et al., 2009) 15

2.11 Swelling behavior of natural rubber filled silica/carbon black (N.


xiii

2.12 100% modulus in silica content (N. Rattanasom et al., 2007) 17

2.13 Tensile strength of rubber-silica/carbon black relationship (N.


2.14

Modulus at 100% elongation versus filler content in natural

rubber/carbon black/calcium carbonate (Saowaroj Chuayjuljit et al.,

2002)

18

2.15 Tensile strength and elongation at break of natural

rubber/organoclay nanocomposite (P. L. Teh et al., 2003) 19

3.1 Two rolls mill 23

3.2 25-ton hot and cold molding press 24

3.3 50kN universal testing machine 26

4.1 Graph of time to break (sec) versus filler content (PHR) 30

4.2 Graph of highest tensile strength (MPa) versus filler content (PHR) 31

4.3 Tensile strength versus loading (PHR) of rice husk/ENR (Z. A. M.

Ishak et al., 1994) 32

4.4 Graph of extension (mm) versus filler content (PHR) 33

4.5 Elongation result from various contents of filler (Siti Salina Sarkawi

et al., 2003) 34

4.6 Stress-Strain relationship of 0 parts filler in SBR 35





4.11 Graph of tensile modulus (MPa) versus filler content (PHR) 40

4.12 Tensile modulus versus filler loading in oil palm wood flour/natural

rubber blend (Hanafi Ismail et al., 1999) 41

4.13 Graph of swelling (%) versus filler content (PHR) 42

4.14 Effect on swelling index in various filler (P.L. Teh et al., 2004) 43

xiv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Stress-Strain Result 49

B Technical Report 50

xv

LIST OF ABBREVIATIONS

SBR Styrene Butadiene Rubber

NR Natural Rubber

SMR Standard Malaysia Rubber

kN Kilo Newton

mm Millimetre

Sec Second

MPa Mega Pascal

PHR Part per hundred Rubber

CB Carbon Black

ENR Epoxidized Natural Rubber

6-PPD N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene-diamine)

CBS N-cyclohexyl-2-benzothiazyl sulphenamide

W Weight

μ Micro

°C Degree Celsius

N/cm2

Newton per Centimetre Square

g/cm3 Gram per Centimetre Cube

1

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND OF STUDY

Rubber can be categorizes into two; natural rubber and synthetic rubber. Natural

rubber can be found in the form of latex, which is milky in color. The latex can be found

in typical rubber trees originally from South Africa. Rubber has the ability to undergo

plastic deformation and still can return to its previous form. This ability gives the rubber

advantages to be selected in many manufacturing product such as tire etc.



from natural rubber in every aspect. Styrene-butadiene rubber has low elasticity

properties; it is easy to cut and press compared to Standard Malaysian Rubber (SMR) –

natural rubber type of rubber.

Styrene-butadiene Rubber (SBR) is a polymer which combines copolymer of

styrene and butadiene to form whether 1,2-, cis-1,4-, or trans-1,4-unit components (Sung-

Seen Choi, 2001). Sung-Seen Choi also stated that styrene-butadiene rubber depend on

the component form, 1,2-, cis-1,4-, or trans-1,4-units to produce different microstructure.

Styrene-butadiene rubber is commonly used in tire compounds.

2

Oil palm trunk fiber can be found in oil palm tree that commonly plant in

Malaysia. Oil palm was brought into Malaysia from Botanical Garden, Singapore in 1870

(K. O. Lim et al., 1996). Oil palm trunk fiber can be use as a natural filler to produce

different properties to rubber.

1.2 PROBLEM STATEMENTS

Rubber is a special polymer with high tensile strength and low hardness. Rubber

take place in marketable as a good product such as tire, medical glove, slipper etc.

Different type of products needs different type of tensile strength as well as hardness.

Therefore, to reduce tensile strength and increase hardness, fillers are needed. Findik et

al., (2004) stated that fillers are reinforced into rubber mixture for better performance and

reducing cost.

Oil palm trees are trees with specialty to produce oil – usually to produce cooking

oil. The trees produce yields that decreasing every year, which leads to the tree being

replanted 25 – 30 years later after planting (K. O. Lim et al., 1996). The oil palm trunk

was treated as a waste and usually was burnt at plant location (H. Yamada et al., 2010).

The burning activities will led to environmental issues such as green house effect and

acid rain.

The purpose of this research is to investigate the properties of styrene butadiene

rubber blending with oil palm trunk fiber as filler. This research also carried out in order

to check significant of different parts of oil palm trunk fiber acting as filler used to

styrene butadiene rubber.

3

1.3 OBJECTIVES OF THE RESEARCH

There are two objectives that were carried out during this research after

considering the method and raw materials used.

To investigate the mechanical properties changes in styrene butadiene rubber

(SBR) filled with oil palm trunks as fillers.

To check the differences in properties between the amounts of fillers used.

1.4 SCOPE OF STUDY

The research is based on experimental lab research. Styrene butadiene rubber, oil

palm trunk fiber and other chemicals were ordered through chemical engineering

laboratory. The parts of oil palm trunk fiber that is going to be used are 0 parts, 15 parts,

30 parts, 40 parts and 50 parts. The blending was carried out at typical two rolls mill

located inside chemical engineering laboratory with speed 12 rotations per minute,

maximum temperature of 90 °C and minimum temperature 70°C. The molding process

was done using 25 ton hot and cold molding press located at chemical engineering

laboratory with maximum temperature of 165 °C and minimum temperature 155 °C.

The mechanical properties that being tests are tensile and swelling test. The

tensile test was done using 50 kN universal testing machine located at manufacturing

engineering laboratory. The parameter used in this test are Tensile strain at Break

(Standard) (mm/mm), Load at Break (Standard) (N), Extension at Break (Standard)

(mm), Tensile extension at Break (Standard) (mm), Time at Break (Standard) (sec), and

Modulus (Automatic) (MPa). Swelling test was done in chemical engineering laboratory

with only two chemical test; kerosene and diesel. The diesel that is being used is a typical

diesel that can be bought at petrol station.

4

1.5 RATIONALE AND SIGNIFICANCE

Different type of products needs different type of tensile strength as well as

hardness. Therefore, to reduce tensile strength and increase hardness, fillers are needed.

The compatibility of styrene butadiene rubber with oil palm trunk fiber was test to

determine the properties in them.

The oil palm trees produce yields that decreasing every year, which leads to the

tree being replanted 25 – 30 years later after planting (K. O. Lim et al., 1996). The oil

palm trunk was treated as a waste and usually was burnt at plant location (H. Yamada et

al., 2010). The contribution of oil palm trunk as a filler in rubber compound will decrease

the burning activities and reducing environmental issues.

5

CHAPTER 2

LITERATURE REVIEW

2.1 STYRENE BUTADIENE RUBBER



from natural rubber in every aspect. Styrene-butadiene rubber has low elasticity

properties; it is easy to cut and press compared to Standard Malaysian Rubber (SMR) –

natural rubber type of rubber.

Styrene-butadiene Rubber (SBR) is a polymer which combines copolymer of

styrene and butadiene to form whether 1,2-, cis-1,4-, or trans-1,4-unit components (Sung-

Seen Choi, 2001). Sung-Seen Choi also stated that styrene-butadiene rubber depend on

the component form, 1,2-, cis-1,4-, or trans-1,4-units to produce different microstructure.

Styrene-butadiene rubber is commonly used in tire compounds.

M.T. Ramesan et al., (2004) reported that blending of natural rubber/styrene

butadiene rubber gives better abrasion resistance properties. This is proven that styrene

butadiene rubber give boost to natural rubber in term of properties and good.

6

2.2 NATURAL FILLER

Many researches have been done in rubber/natural filler blending in order to

improve the properties of rubber with economically. Natural filler that usually being used

in research are rise husk, oil palm fiber and coconut fiber. The differences in properties of

rubber product can be obtained from different filler.

2.3 OIL PALM TRUNK FIBER

Oil palm trunk fiber can be found in oil palm tree that commonly plant in

Malaysia. Oil palm was brought into Malaysia from Botanical Garden, Singapore in 1870

(K. O. Lim et al., 1996). Oil palm trunk fiber can be use as a natural filler to produce

different properties to rubber.

Figure 2.1: Oil palm trunk fiber.

7

RunCang Sun et al., (2001) reported that the oil palm trunk fiber enhance sulphate

pulp properties into fair strength. Oil palm trunk fiber can be potential in increasing

properties of rubber as filler. The cooperation of oil palm trunk fiber and styrene

butadiene rubber might enhance the rubber properties.

2.4 CROSSLINK

Rubber processing is a must to mix rubber and filler into one, solid rubber

product. Vulcanizing agent is a part of crosslink between rubber bonds. Fillers is

reinforced into rubber mixture for better performance and reducing cost (Findik et al.,

2004). Findik et al., (2004) also stated that, sulphur and peroxide are two common

vulcanizing agents that used activation energy which increase the mechanical properties

of rubber product at higher temperature.

2.5 VULCANIZATION

Vulcanization is a process where the rubber matrix is being crosslink with help

from vulcanizing agents. After being vulcanized, the rubber compound became cured;

with no more reaction happen causing the rubber became stable. The curing happens at

high temperature within 150 – 170 °C according to their rubber properties respectively.

Popular vulcanizing agents used are sulphur and peroxide.

8

2.6 MECHANICAL PROPERTIES

2.6.1 TENSILE STRENGTH

Many researches have been done in order to investigate the mechanical properties

of rubber and natural fillers before. A.I. Khalf et al., (2010) have investigated the effect

of rice husk filler in styrene butadiene rubber with the presence of maleic anhydride. The

tensile strength of rubber sample increase until 25 PHR of filler content, before it start to

decrease at 30 PHR. This is because of the high content of filler that may cause the poor

bonding in rubber matrix causing the tensile strength to drop.

Figure 2.2: Tensile strength-rice husk content relationship (A.I. Khalf et al., 2010).

9

N. Rattanasom et al., (2009) on the other hand have investigated the mechanical

properties of natural rubber reinforced with various fillers. Gum is virgin rubber, C6 is

addition of 6 PHR of clay, CB6 is addition of 6 PHR of carbon black, CB14 is addition of

14 PHR of carbon black, S6 is addition of 6 PHR of silica and S35 is addition of 35 PHR

of silica. Clay in 6 PHR quantity show promising aspect in tensile strength than the other.

Figure 2.3: Tensile strength of natural rubber reinforced with various fillers (N.

Rattanasom et al., 2009).

Hanafi Ismail et al., (1996) also have investigated the mechanical properties of

ENR/oil palm wood flour. The tensile strength of rubber decreases with increasing of

filler content and filler size.

10

Figure 2.4: Tensile strength of rubber-filler content relationship (Hanafi Ismail et al.,

1996)

2.6.2 TENSILE MODULUS

Many researches have been done to determine the tensile modulus of rubber

compound. In order to check the compatibility of rubber composite, the modulus is

defined in the stress-strain relationship. Hanafi Ismail et al., (2000) have determined the

tensile modulus of white rice husk ash loading in natural rubber/linear low density

polyethylene blends with proportional to filler content. The additions of natural filler

basically increase tensile modulus of the rubber compound.

11

Figure 2.5: Tensile modulus of white rice husk ash loading in natural rubber/linear low

density polyethylene blends (Hanafi Ismail et al., 2000).

Hanafi Ismail et al., (1999) have investigated the mechanical properties of rubber

reinforced short oil palm fiber. The tensile modulus for treated rubber compound is much

better than the untreated one. This is because of vulcanization process enhance the rubber

properties causing the tensile modulus to increase more than untreated one.

12

Figure 2.6: Modulus at 100% elongation according to fiber loading (Hanafi Ismail et al.,

1999).

2.6.3 SWELLING

Swelling behavior is the ability of the rubber product to absorb chemical.

Swelling test was done in order to check chemical resistance in rubber sample. Many

researches have been done according to swelling behavior. Hanafi Ismail et al., (2001)

have investigated the swelling behavior of recycled rubber powder filler on natural

rubber. The more filler give more chemical resistance. As the natural rubber was filled,

the rubber became more stable and increase chemical resistance ability and less chemical

can be absorb.

13

Figure 2.7: Swelling behavior of recycled rubber powder filler on natural rubber (Hanafi

Ismail et al., 2001).

2.6.4 ELONGATION

Elongation before break is determined to check the ability of rubber to extend

their length before break. Many researches have been done in order to determine this

property. Maya Jacob et al., (2003) have investigated the mechanical properties of sisal

and oil palm hybrid fiber reinforced with natural rubber. The elongation became shorter

as the filler content increase. This is because of brittleness of rubber sample increase with

increasing of filler loading.

14

Figure 2.8: Elongation at break versus fiber loading in sisal/oil palm hybrid fiber

reinforced natural rubber (Maya Jacob et al., 2003).

2.7 RECYCLED ELASTOMER

Recycling elastomer and converted it to reinforce with rubber proven economical

as the filler is already in the recycled elastomer. Various researches have been done in

order to determine recycled elastomer as filler properties. Noriman et al., (2009) has

investigated the mechanical properties of styrene butadiene rubber (SBR) reinforced with

recycled acrylonitrile-butadiene rubber (NBRr) assisted by epoxidized natural rubber

(ENR-50). The tensile strength has increased with decreasing of NBRr composition but

the existence of ENR-50 improved the property.

15

Figure 2.9: The tensile strength of SBR/NBRr with/without ENR-50 (Noriman et al.,

2009).

Figure 2.10: The tensile modulus of SBR/NBRr with/without ENR-50 (Noriman et al.,

2009).

mechanical properties of styrene butadiene rubber

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