UNIVERSITI PUTRA MALAYSIA

RADIATION-INDUCED GRAFT COPOLYMERIZATION OF METHYL ACRYLATE AND ACRYLIC ACID ONTO RUBBER WOOD FIBER

SALIZA BINTI JAM

FSAS 2002 12

RADIATION-INDUCED GRAFf COPOLYMERIZATION OF METHYL ACRYLATE AND ACRYLIC ACID ONTO RUBBER WOOD FIBER

By

SALIZA BINTI JAM

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia

in Fulfilment of the Requirement for the Degree of Master of Science

March 2002

DEDICATION

To my beloved husband, ZuI Hisham, whose patience, supports and

companionship has facilitated my work. To "Mak" and "Abah", and also my

family thanks for everything.

II

Abstract of Thesis presented to the Senate ofUniversiti Putra Malaysia in fulfilment of the requirement for the degree of Master of Science

RADIATION-INDUCED GRAFf COPOLYMERIZATION OF METHYL ACRYLATE AND ACRYLIC ACID ONTO RUBBER WOOD FIBER

By

SALIZA BINTI JAM

March 2002

Chairman: Dr. Mansor Hj. Ahmad

Faculty: Science and Environmental Studies

Graft copolymerization of methyl acrylate and acrylic acid monomers onto rubber

wood fiber (RWF) was carried out by simultaneous radiation-induced technique.

The parameters affecting the grafting reaction were investigated and the optimum

conditions for both monomers obtained are as follows: impregnation time, 1 6

hours; total dose, 3 0 kGy; methanol:water ratio, 3: 1 ; monomers concentration, 40

v/v% and sulphuric acid concentration, 0.1 moUL.

Fourier Transfonn Infrared (FTIR) , Thennogravimetry Analysis (TGA) , and

Scanning Electron Microscope (SEM) analyses were perfonned to characterize

graft copolymers. The structural investigation by X-ray diffraction (XRD) shows

the degree of crystallinity of rubber wood fiber decreased with the incorporation of

poly(methyl acrylate) and poly(acrylic acid) grafts which causes partial destruction

of the inherent crystallinity in fiber. The sorption behavior of poly(acrylic acid)-

grafted R WF resin toward some metal ions was investigated using a batch

technique. The binding capacities ofeu, Fe, Zn, Cd and Pb ions were 0.379, 0.795,

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0.189, 0.921 and 1.218 mmol/g, respectively. The sorption capacities of

poly(acrylic acid)-grafted RWF resin were selectivity toward these metal ions is in

the following order: Pb > Cd> Fe > Cu > Zn.

Irradiated PP/poly(methyl acrylate)-grafted RWF composite has higher mechanical

properties than PP/poly(methyl acrylate)-grafted RWF composite because of EB­

treatment of PP is a highly efficient technique of creating chemically active sites

on PP matrix, which created a better coupling, and can be proved by SEM studies

and TGA analysis. Generally, the addition of poly(methyl acrylate)-grafted RWF

as coupling agent into the composites reduces the flexural and tensile properties,

which, causes poor and incompatible dispersion, which leads to poor filler-matrix

interfacial bonding. But, the addition of 1.0 wt % of P(MA)-g-RWF into the blend

give an optimum value of flexural and tensile properties.

IV

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

PENGKOPOLIMERAN CANGKUK TERARUH SINARAN METIL AKRILIK DAN ASID AKRILIT KE ATAS SERABUT KAYU GETAH

Oleh

SALIZA HINTI JAM

Mac 2002

Pengerusi: Dr. Mansor Hj. Ahmad

Fakulti: Sains dan Pengajian Alam Sekitar

Pengkopolimeran cangkuk monomer metil akrilat dan asid akrilik ke atas serabut

kayu getah telah dilakukan melalui teknik radiasi secara berterusan. Parameter-

parameter yang memberi kesan terhadap pengkopolimeran telah dikaji dan keadaan

optimum tindak balas yaang diperolehi untuk kedua-dua monomer adalah seperti

berikut: masa rendaman, 1 6 jam; jumlah dos yang diserap, 30 kGy; nisbah

metanol:air, 3:1 ; kepekatan momomer, 40 v/v%, dan kepekatan asid sulfurik, 0 . 1

mollL.

Pencirian kopolimer cangkuk telah dilakukan melalui analisis spektroskopi

inframerah, analisis termogravimetri dan fotomikrograf pengimbasan elektron

mikroskop (SEM). Kajian struktur melalui pembelauan sinar-X (XRD)

menunjukkan kandungan darjah penghabluran serabut kayu getah berkurangan

dengan kemasukan poli(metil akrilat) dan poli(asid akrilik) di mana ia

menyebabkan pemusnahan sebahagian hablur semulajadi serabut. Ciri serapan

poli(asid akrilik) terhadap ion sebahagian logam telah dikaji melalui teknik

v

0.379, 0.795, 0.189, 0.921 dan 1.218 mmollg. Kapasiti serapan resin kopolimer

asid akrilit adalah mengikut susunan berikut: Pb > Cd > Fe > eu> Zn.

Komposit PP tersinar/poli(metil akrilat)-cangkuk-serabut kayu getah mempunyai

sifat mekanikal lebih baik daripada komposit PP/poli(metil akrilat)-cangkuk­

serabut kayu getah kerana rawatan sinaran elektron (EB) ke atas PP merupakan

teknik berkesan untuk mencipta tapak. aktif di atas PP secara kimia, di mana ia

menghasilkan campuran yang lebih baik dan ini dibuktikan melalui analisis­

analisis SEM dan TGA. Secara amnya, penambahan poli(metil akrilat)-cangkuk­

serabut kayu getah sebagai agen penggandingan ke dalam komposit merendahkan

sifat mekanikal komposit tersebut, di mana ketidakserasian penyebaran berlaku

yang menghasilkan ikatan antara permukaan pengisi-matrik yang iemah. Tetapi,

penambahan berat 1.0 % poli(metil akrilat)-cangkuk-serabut kayu getah pada ke

dalam adunan memberikan nilai optimum sifat mekanikal komposit tersebut.

VI

ACKNOWLEGDEMENTS

I would to take to express my truly appreciation and gratitude to the chairman of

my supervisory committee, Dr. Mansor Haji Ahmad and committee.

members,

Prof. Dr. Wan Md. Zin Wan Yuous and Dr. Khairul Zaman Hj. Dahlan (MINT) for

their invaluable guidance, constructive comments, continuous moral support, and

suggestion throughout this study.

Special thanks to all the staff in MINT, Jalan Dengkil, Bangi, Encik Zahid, Encik

Rosli, Chantara. Kah Zab, Kak Ina, and Encik Wan Ali, and for their kind

assistance. Grateful thanks to all the staff in Chemistry Department for their

assistance for contributing their experience to my study, especially to Encik

Kamal. A special thanks to Dr. Jalaluddin Haruo and En. Harmaen from Faculty of

Forestry, UPM. I also like to thank Miss Azilah and Ms. Siti Selina from Faculty

of Veterinary for their technical assistant with the SEM analysis.

Special thanks to my lab mates, Lynn, Fima and Radin for their help in one-way or

another.

I am also greatly indebted to UPM and MINT for providing the analysis facilities

and the Government for PASCA grant for me to complete the study successfully.

Vll

I certify that an Examination Committee met on 5th March 2002 to conduct the final examination of Graduate Student on her degree of Master of Science thesis entitled "Radiation-Induced Graft Copolymerization of Methyl Acrylate and Acrylic Acid onto Rubber Wood Fiber" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examonation Committee are as follows:

Sidik Silong, Ph.D. Faculty Science and Environmental Studies Universiti Putra Malaysia (Chairman)

Mansor Hj. Ahmad, Ph.D. Faculty Science and Environmental Studies Universiti Putra Malaysia (Member)

Wan Md. Zin Wan Yunus, Ph.D. Professor Faculty Science and Environmental Studies Universiti Putra Malaysia (Member)

Khairul Zaman Hj. Mohd. Dahlan, Ph.D. Malaysian Institute of Nuclear Technology Research (MINT) Dengkil, Bangi (Member)

�OHA;;;;; -;

Vlll

RAMADaI, Ph.D. Professor, Deputy Dean of Graduate School, Universiti Putra Malaysia

Date: 2 R MAR 2002

This thesis submitted to the Senate of Universiti Putra Malaysia has been accepted as fulfilment of the requirement for the degree of Master of Science.

IX

AINI IDERIS, Ph.D. Professor, Dean of Graduate School, Universiti Putra Malaysia

Date: I 3 JUN 2002

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that is has not been previously or concurrently submitted for any other degree at UPM or other institutions.

x

Date: 2 B MAR 2002

TABLE OF CONTENTS

DEDICATION ABSTRACT ABSTRAK. ACKNOWLEDGEMENTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS

CHAPTER I INTRODUCTION

Significance of The Study Objectives of The Study

II LITERATURE REVIEW Rubber Wood

General Characteristics Durability Mechanical Properties Uses Chemical Composition of Rubber Wood

Holocellulose Cellulose Hemicelluloses Lignin Extraneous Components

Poly(Methyl Acrylate) Polymerization of Methyl Acrylate Properties of Poly(Methyl Acrylate)

Thennal Properties

Mechanical Properties Application of Poly (Methyl Acrylate)

Poly(Acrylic Acid) Polymerization of Acrylic Acid Properties of Poly(Acrylic Acid)

Tacticity Thermal Properties Solubility Viscosity Chemical Properties

Application of Poly(Acrylic Acid)

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Page

11 III v VIl Vlll X XlV xv XVll

1 2 4

6 6 6 7 7

10 11 12 13 14 16 18 19 20 20 20 21 21 22 22 23 23 23 24 24 25 25

Ion Exchange Resins Bio-Composite Materials Radiation Grafting

Method of Radiation Grafting The Pre-irradiation Method The Peroxide Method The Simultaneous Method

ill METHODOLOGY

26 27 29 30 30 31 33

Materials 35 Methods 36 Radiation Graft Copolymerization 36

Extraction of Homopolymer 36 Calculation of Percentage of Grafting 37 Characterization of Grafted Rubber Wood Fiber 37

Fourier Transform Infrared Analysis (FTIR) 37 Thermogravimetric Analysis (TGA) 38 Scanning Electron Microscope (SEM) 38 X-ray Diffractions (XRD) 39 Atomic Absorption Spectrophotometry (AAS) 39

Ion Exchange Resins 40 Metal Ion Capacity 40 Carboxylic Acid Capacity 40

Bio-Composite Materials 41 The Preparation of The Blends 41 Mechanical Testing 41

N RESULTS AND DISCUSSION 43 Radiation-Induced Grafting Copolymerization of Rubber Wood Fiber 43

Effect of Impregnation Time 43 Effect of Total Dose 45 Effect of Methanol Composition in Water 47 Effect of Monomers Concentration 49 Effect of Sulphuric Acid 5 1

Characterization of Grafted Rubber Wood Fiber 53 Analysis of FTIR Spectra 53 Thermogravimetric Analysis 57 SEM Studies of Grafted Fiber 59 X-Ray Diffraction Measurements 61

Bio-Composites 63 Thermogravimetry-Derivative Thermal Analysis 63 Effect of and Poly(Methyl Acrylate)- Grafted Rubber Wood Fiber on Mechanical Properties of Composites 69

XII

v

Effect ofPoly(Methyl Acrylate )-Grafted Rubber Wood Fiber as Coupling Agent on Mechanical Properties of Irradiated PPIRWF Composites 71 SEM Studies of Various Rubber Wood Fibers

Reinforced Composites 76 Ion Exchange

Sorption of Metal Ions By Batch Method 80 The Carboxylic Acid Capacity 80

CONCLUSIONS 81

BffiLIOGRAP HY APP ENDICES

85 93 98 BIODATA OF THE AUTHOR

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LIST OF TABLES

Table Page

1 Strength Properties of Rubber Wood as Compared to Other Malaysian Timbers 8

2 Basic and Grade Stresses of Rubber Wood 9

3 Chemical Composition of Oil Palm Residues. Douglas fir. Rubber Wood, Bagasse and Coconut 12

4 Composition and Mechanical Properties of Various Rubber Wood Fiber Reinforced Composites 70

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LIST OF FIGURES

Figure Page

1 The partial molecular structure of cellulose [(C6HIOOS)x] in the 1 ,4-�-D-glucopyranose form. 1 3

2 Partial molecular structure of O-acetyl-4-0-methyl-glucuronoxylan. 15

3 The most common linkages between phenylpropane units in lignin. 1 7

4 Effect of impregnation time on absorption ofMA and AA onto RWF. 44

5 Effect of total dose on radiation graft copolymerization of MA and AA onto RWF. 46

6 Effect of methanol composition in methanol-water system on radiation graft copolymerization ofMA and AA onto RWF. 48

7 Effect of monomers concentration on radiation graft copolymerization of methyl acrylate and acrylic acid onto rubber wood fiber. 50

8 Effect of sulphuric acid concentration on radiation graft copolymerization of MA and AA onto R WF. 52

9 FTIR spectra ofRWF, P(MA)-g-RWF, and P(MA)-g-RWF. 55

1 0 Modes of free radical generation into irradiated fiber: Radicals are formed after C-H, C-O, or C-C bond cleavages: (a) hydrogen and hydroxyl abstraction, (b) cycle opening, (c) chain scission 56

1 1 TGA Thennograms ofRWF, P(MA)-g-RWF, and P(MA)-g-RWF. 58

12 SEM micrographs illustrating the surface morphology of RWF, P(MA)-g-RWF, and P(MA)-g-RWF at magnification 2 ,500x. 59

1 3 Diffraction patterns of RWF, P(MA)-g-RWF, and P(AA)-g-RWF. 62

1 4 TGA-DTG Thermograms ofPPIRWF, PPIP(MA)-g-RWF, irradiated PPIP(MA)-g-RWF and irradiated PPIRWF (treated with 1 % P(MA)-g-RWF) composites. 65

xv

15 Effect of P(MArg-RWF on flexural modulus and strength of RWF reinforced composites. 73

16 Effect ofP(MA )-g-RWF on tensile modulus and strength of RWF reinforced composites. 74

17 Effect ofP(MA)-g-RWF on impact strength ofRWF reinforced composites. 75

18 SEM micrographs illustrating the fracture surface ofP PIRWF, PPIP(MA)-g-RWF, irradiated PPIP(MA)-g-RWF, and irradiated PPIRWF (treated with 1% (P(MA)-g-RWF)) composites at magnification 200x. 77

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LIST OF ABBREVITIONS

FTIR Fourier-Transfonn Infrared

Irradiated PPIP(MA)-g- Irradiated polypropylene blends with poly(methyl R WF acrylate )-grafted rubber wood fiber

Irradiated PP/ RWF

Irradiated PP/ RWF (treated 1% P(MA)-g­RWF)

MINT

P(AA)

P(MA)

P(AA)-g-RWF

P(MA)-g-RWF

PPIRWF

PPIP(MA)-g-RWF

RWF

SEM

TGA

XRD

Irradiated polypropylene blends with rubber wood fiber

Irradiated polypropylene blends with rubber wood fiber (treated with 1% poly(methyl acrylate)-grafted rubber wood fiber)

Malaysian Institute for Nuclear Technology Research

Poly( acrylic acid)

Poly(methyl acrylate)

Poly( acrylic acid)-grafted rubber wood fiber

Poly(methyl acrylate )-grafted rubber wood fiber

Polypropylene blends with rubber wood fiber

Polypropylene blends with poly(methyl acrylate)­grafted rubber wood fiber

Rubber wood fiber

Scanning Electron Microscope

Thennogravimetry Analysis

X-Ray Diffraction

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1

CHAPTER 1

INTRODUCTION

Graft copolymerization onto fiber can be carried out by chemical and radiation

method. Radiation method has been widely used to initiate grafting because it has

many advantages over other conventional methods. In radiation processing, no

catalyst or additives are required to initiate grafting. Generally in the radiation

technique, absorption of energy by backbone polymer initiates a free radicals

process. With chemical initiation, free radicals are brought forth by the

decomposition of the initiator into fragments, which then attack the base polymer

leading to radicals. Chemical initiation is however limited by the concentration and

purity of initiators. However, in case of radiation processing, the dose rate of the

radiation can be varied widely and thus the reaction can be better controlled.

Unlike the chemical initiation method, the radiation-induced process is also free

from contamination. Chemical initiation often brings about problems arising from

local overheating of the initiator. But in the radiation-induced process, the

fonnation of free radicals sites on the polymer is not dependent on temperature but

is only dependent on the absorption of the penetrating high-energy radiation by the

polymer matrix. Therefore, radiation processing is temperature independent or, in

other words, it is a zero activation energy process for initiation.

2

Significance of The Study

Since the event of worldwide ecological awareness, there has been a trend to

produce low cost, biodegradable materials with improved properties. Lately, there

has been a great interest to produce thermoplastic composites reinforced with

natural products. In particular, cellulose fibers are becoming popular because they

have lower cost and lower density and exhibit better processing flexibility and

lower equipment wear than those of fiber glass, (Zadorecki and Mitchell, 1989� Raj

and Kokta, 1991) which is still the common reinforcement. Also, cellulose fibers

yield composites with better mechanical properties than those produced with

materials such as wood floor and peanut shells (Maldas and Kokta, 1991; Raj et

ai., 1990). However cellulose fibers have not been amply used because it is

difficult to produce good dispersions of the fibers in the matrix due to the poor

interfacial adhesion between them (Czarnecki and White, 1980). As the

mechanical properties of composites depend on interfacial adhesion, it is necessary

to have good adhesion between the reinforcement and polymeric matrix (Felix et

ai., 1994).

To improve the interfacial adhesion between a polymeric matrix and cellulose

fibers, a matrix-compatible polymer is commonly grafted to the fibers. Gaylord

demonstrated that grafted cellulose, besides being more compatible with the

matrix, helps to "compatibilize" nongrafted cellulose with the matrix (Gaylord,

1972). He also showed that composites with grafted cellulose have better

processing properties and impact resistance than do those reinforced with

nongrafted cellulose fibers

3

Graft copolymerization is a well-established technique for the modification of the

physical and chemical characteristics of polymers. The nature of modification, for

example, improvement in textile performances, depends on the properties of

monomer. The properties of the grafted copolymer depend not only on the type of

the monomer but also on the grafting level and distribution of monomer units. For

example, the grafting of PMMA onto wool fabric improved textile performances

such as dyeing, moisture regain and mechanical properties (Bashar et ai., 1995;

Varma and Sadhir, 1978). However, further increase in graft yield was found to

cause a slight reduction in moisture regain (EL-Naggar et ai., 1996).

In the past, extensive research has been carried out on radiation-induced grafting of

acrylic acid, acrylamide, methyl methacrylate (Ml\1A), styrene, and acrylonitrile

onto polyethylene, poly(vinyl chloride), and nylon (ehapiro, 1958� Stannett, 1990;

Trivedi et aI., 1975). Very limited works (Garnett and Ng, 1996; Khan and Ahmad,

1997; Zahran and Zohdy, 1986) have so far reported on the effectiveness of

radiation-induced grafting onto cellulosic fiber. Therefore, this research has been

carried out to fulfill the requirements.

Rubber wood is a widely used m�terial due to its many excellent properties such as

its aesthetic appearance, lightness, strength, ease of workability and wide

availability. Nevertheless, it has some limitations. Rubber wood is cellulosic-based

fiber and a hygroscopic material that swells when it absorbs water and conversely,

shrinks when it is dried It is susceptible to insect and fungal attack and undergoes

decay especially in environments like those in the tropics. In order to improve

water resistant, cellulose is already widely modified by acetylation with acetic

4

anhydride (Youngquist et al., 1986). The modification of cellulose through grafting

with monomers was investigated in order to produce hydrophiliclhydrophobic

fiber.

In this work, the surface modification of rubber wood fiber by radiation-induced

grafting methyl acrylate (MA) and acrylic acid (AA) in methanol-water system by

using y-irradiation from Cow source as a mean of initiation was examined. Graft

copolymerization was carried out by mutual or simultaneous method in air.

Percentage of grafting was determined as functions of total dose, methanol

composition in reaction solution, concentration of monomer, and concentration of

sulphuric acid (H2S04). FTIR. TGA and XRD were used to characterize the

grafted fiber.

Objectives of The Study

The objectives of this study are as follows:

1. To graft methyl acrylate and acrylic acid onto rubber wood fiber using

simultaneous graft copolymerization technique.

2. To study the effecting reaction parameters to obtain an optimum condition

of grafting.

3. To characterize rubber wood fiber-grafted methyl acrylate and acrylic acid

by Fourier Transform Infrared Spectroscopy, thermogravimetry, X-ray

diffraction, and scanning electron microscopy.

4. To prepare bio-composite materials from rubber wooa noer-granea metnYI

acrylate and to characterize the mechanical properties of the blends.

5. To prepare ion exchange materials from rubber wood fiber-grafted acrylic

acid and to study metal ion and carboxylic acid capacity using atomic

absorption spectrophotometer.

6

CBAPTERII

LITERATURE REVIEW

Rubber Wood

Rubber wood is the Standard Malaysian Name for the timber of Hevea brasiliensis.

This species has been planted in Peninsular M8.Iaysia for the past hundred years

mainly for its latex. Though there is only one species of rubber tree planted in

Malaysia, there are numerous clones are developed to achieve a higher yield of

latex, and little has been done to improve the tree from on volumetric yield of

wood from these trees.

Rubber wood trees are normally replanted after attaining the age of 25 - 30 years

where they are generally attain a clear bole of more than 10 meters tall (Westgarth

and Buttery, 1965). Diameter of these trees could easily reach 500 mm at breast

height However, trees of newer clones are usually shorter and smaller. Boles of

the seedling trees are usually strong tapered

General Characteristics

Rubber wood is light timber with air-dry density ranging between 560 - 650 kglm3

averaging 640 kglm3 (40 lb/cu. ft.). The sapwood is generally not distinguishable

from the heartwood The wood is whitish yellow or pale cream when freshly cut,

and seasons to a light straw or light brown in color with a slight pinkish tinge. The

7

wood texture ranges from moderately coarse to coarse, with grain ranging from

straight to shallowly interlocking.

Durability

Although rubber wood in its natural from is classified as non.durable and found to

be susceptible to attack by fungi and insects, the durability can be enhanced easily

by proper treatment methods.

Mechanical Properties

Standard mechanical test, similar to the methods outlined in B.S. 373:1957 for 50

mm specimens and A.S.T.M D143-52 have been conducted on rubber wood and

the results are presented in Table 1, together with similar strength properties of

other popular Malaysian timbers, to facilitate ease of comparison. The basic and

grade stress of this timber have been worked out based on the formulae by Chile

(1980a), and are presented in Table 2. The timber falls in Strength Group C

following the criteria for strength grouping of Malaysian timbers (Chik, 1980b).

Results from steam bending trials indicated that rubber wood bends better than

Kapur (Dryobalanops aromatica) and some of the White Merantis (Shreaa spp.).

Rubber wood bends are very stable after they are left to set (Ser and Lim, 1980).