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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.
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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.
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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
XIV
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
XVI
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).