UNIVERSITI PUTRA MALAYSIA
CARBOXYMETHYLATION OF CELLULOSE FROM KENAF (Hibiscus cannabinus L.) CORE FOR
HYDROGEL PRODUCTION
ISMAWATI PALLE
FH 2008 6
CARBOXYMETHYLATION OF CELLULOSE FROM KENAF (Hibiscus cannabinus L.) CORE FOR
HYDROGEL PRODUCTION
ISMAWATI PALLE
MASTER OF SCIENCE UNIVERSITI PUTRA MALAYSIA
2008
CARBOXYMETHYLATION OF CELLULOSE FROM KENAF (Hibiscus cannabinus L.) CORE FOR HYDROGEL PRODUCTION
By
ISMAWATI PALLE
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirement for the Degree of Master of
Science
April 2008
To My Beloved Mum,
Brothers Ibrahim, Ismail and Ishak
With grateful appreciation for their encouragement and love
ii
Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Master of Science
CARBOXYMETHYLATION OF CELLULOSE FROM KENAF (Hibiscus cannabinus L.) CORE FOR HYDROGEL PRODUCTION
By
ISMAWATI PALLE
April 2008
Chairman : Associate Professor Paridah Md. Tahir, PhD
Faculty : Forestry
Kenaf is known as fast growing species which is planted mainly for bast fibre
which have been used as an alternative raw material for particleboard,
medium density fibreboard or pulp and paper industry. On the contrary, the
core of kenaf stem which is consist of straw-like and short-length fibres cannot
be used exclusively in particleboard and pulp paper industries due to low
strength and dimensional stability. Thus, and alternative usage has to be
researched. Since kenaf core have relatively high amount of holocellulose, low
lignin content and is highly absorbent, these properties make kenaf core a
potential material for producing carboxymethyl cellulose (CMC) in hydrogels.
This study comprised three main aspects: 1) Evaluation of the basic properties
of kenaf core fibres, 2) Carboxymethylation of the kenaf core and 3) Formation
of hydrogel from the carboxymethylated kenaf core.
iii
The evaluations of chemical and physical properties of kenaf core fibres were
conducted prior to the carboxymethylation process. The samples for fibre
morphology and chemical analyses of the kenaf core were prepared from
macerized and mechanically refined fibres, respectively. All the chemical
analyses were conducted using fibre of 40-mesh size (425 µm size) whilst for
fibre morphology (fibre length, fibre diameter, lumen diameter and cell wall
thickness) match stick kenaf core samples were used. The study indicates that
kenaf core comprises approximately 50.6% alpha-cellulose, 27.1%
hemicellulose and 20.5% of lignin. A high percentage of water absorption of
kenaf core (i.e., 50%) was recorded due to the presence of a large number of
pits along the longitudinal axis of the cell wall as shown by pictures from SEM.
The core fibres has low Runkel ratio of 0.36 which is responsible for high water
absorption owing to large lumen size and thin fibre wall suggesting good liquid
transmission.
Carboxymethylated kenaf core was successfully produced under
heterogeneous condition by reacting the core fibres with sodium
monochloroacetate as an etherifying agent and isopropanol as reaction
medium in the presence of sodium hydroxide as a swelling agent. Several
factors affecting the carboxymethylation process such as time, sodium
hydroxide concentrations and temperature were studied. The degree of
substitution (DS), reaction efficiency (RE) and weight percent gain (WPG)
were also determined. Among the three types of kenaf core used, crude kenaf
iv
core (CKC), extractive-free kenaf core (KCFE), and extractive- and lignin-free
kenaf core (KCFL), KCFL gives the highest DS value. The purity of the
holocellulose was found to be the crucial factor in obtaining high yield. The
optimum reaction condition for producing carboxymethylated kenaf core with
DS value of 0.87 was based on the following procedures: firstly, by extracting
the extractives and lignin from the kenaf core to produce extractive- and lignin-
free kenaf core (KCFL) and then reacting the KCFL with sodium
monochloroacetate in 30% sodium hydroxide at 55oC for 2 hours. From FTIR
spectroscopy analysis, the existence of peak at 1591 cm-1 on modified kenaf
core revealed that some of hydroxyl groups of cellulose kenaf fibre had been
effectively substituted with the carboxymethyl group. The SEM micrograph
observation also reconfirmed the substitution process, where the unmodified
kenaf core had rough features with the pits still empty. On the other hand,
smoother features were observed on the modified kenaf core fibre with the pits
has been filled presumably with carboxymethyl of sodium monochloroacetate.
Hydrogels were successfully produced using different concentrations of
carboxymethylated kenaf core of extractive- and lignin-free (CMKCFL) at
several irradiation doses. A dose of 70 kGy was found to be the optimum
irradiation dose for crosslinking of CMKCFL hydrogel with gel content of
37.1%. The optimum crosslinking condition was 50 kGy irradiation and 50%
concentration, producing an acceptably good properties CMKCFL hydrogel.
The swelling ratio of CMKCFL hydrogel was the highest in de-ionized water
v
compared to alkaline (1.0 M NaOH) and acidic (1.0 M HCl) at all ranges of
irradiation doses except for 10 kGy. Increasing the level of concentration of
aqueous CMKCFL resulted in an increased in swelling. This result was
however opposite when the swelling test was conducted in acid and alkali
mediums. The overall results indicate that kenaf core fibre can be used as raw
material for carboxymethyl cellulose and hydrogel production and possess
satisfying other properties.
vi
Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains
KARBOKSIMETIL SELULOSA DARIPADA GENTIAN TERAS KENAF (Hibiscus cannabinus L.) UNTUK PENGHASILAN HIDROGEL
Oleh
ISMAWATI PALLE
April 2008
Pengerusi : Profesor Madya Paridah Md. Tahir, PhD
Fakulti : Perhutanan
Kenaf dikenali sebagai spesis cepat tumbuh yang ditanam khusus untuk
gentian kulit yang telah digunakan sebagai bahan alternatif untuk papan serpai,
papan serpai berketumpatan sederhana atau industri pulpa dan kertas.
Sebaliknya, gentian teras batang kenaf yang mengandungi bentuk seperti
jerami dan gentian yang pendek tidak boleh digunakan dengan sendirinya
dalam papan serpai, papan serpai berketumpatan sederhana atau industri
pulpa dan kertas kerana rendah kekuatan dan kestabilan dimensi. Oleh itu,
penggunaan alternatif perlu dikaji. Memandangkan gentian teras batang kenaf
mempunyai tinggi kandungan holoselulosa, kandungan lignin yang rendah dan
kadar serapan yang tinggi, sifat-sifat ini membuatkan gentian teras batang
kenaf sesuai untuk penghasilan karboksimetil selulosa (KS) dalam hidrogel.
Kajian ini terbahagi kepada tiga bahagian utama: 1) Penilaian sifat asas gentian
teras kenaf, 2) Karboksimetil gentian teras kenaf dan 3) Pembentukan hidrogel
daripada gentian teras kenaf yang dikarboksimetil.
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Penilaian sifat kimia dan fizikal gentian teras kenaf dilakukan sebelum proses
karboksimetil dijalankan. Sampel untuk morfologi gentian dan analisis kimia
disediakan daripada maserasi dan gentian dihalusi secara mekanikal. Semua
analisis kimia dijalankan menggunakan gentian bersaiz 40-mesh (saiz 425 µm)
manakala untuk analisis morfologi serat (panjang gentian, diameter gentian,
diameter lumen dan tebal dinding sel) gentian teras kenaf berukuran mancis
digunakan. Kajian ini mendapati gentian teras kenaf mengandungi 50.6% alfa-
selulosa, 27.1% hemiselulosa dan 20.5% lignin. Peratus serapan air gentian
teras kenaf yang tinggi ( 50%) telah dicatatkan kerana peratus pit yang banyak
dibahagian memanjang dinding sel seperti yang diperhatikan melalui SEM.
Gentian teras mempunyai nisbah Runkel yang rendah iaitu 0.36, serta
menunjukkan kadar serapan air tinggi kerana saiz lumen besar dan dinding
gentian nipis membantu memudahkan pemindahan cecair.
Gentian teras kenaf berjaya dikarboksimetilkan dalam keadaan heteregen
terhasil daripada tindakbalas gentian teras dengan sodium monokloroasetat
sebagai agen eter dan isopropanol sebagai media tindakbalas dengan
kehadiran natrium hidroksida sebagai agen pembengkakan. Beberapa faktor
yang mempengaruhi proses pengkarboksimetilan seperti masa, kepekatan
natrum hidroksida dan suhu yang digunakan dikaji. Darjah penukargantian
(DP), peratus kecekapan (PK) and peratus pertambahan berat (PPB) juga
ditentukan. Antara tiga jenis gentian teras kenaf yang digunakan, gentian teras
sebenar batang kenaf (GTSK), gentian teras kenaf tanpa ekstraktif (GTKTE)
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juga gentian teras kenaf tanpa ekstraktif dan lignin (GTKTEL), GTKTEL
memberikan nilai DP tertinggi. Ketulinan holoselulosa didapati faktor penting
untuk memperolehi hasil yang tinggi. Keadaan untuk tindakbalas optimum bagi
menghasilkan karboksimetil gentian teras kenaf dengan DP 0.87 adalah
berdasarkan prosedur berikut: pertama, mengekstrak ekstraktif dan lignin
daripada gentian teras kenaf untuk menghasilkan GTKTEL dan tindakbalaskan
dengan sodium monokloroasetat dalam 30% natrium hidroksida pada suhu
55oC selama 2 jam. Daripada analisis spektroskopi inframerah transformasi
Fourier (FTIR), kewujudan puncak pada 1591 cm-1 pada gentian teras kenaf
yang dimodifikasi menunjukkan beberapa kumpulan hidroksil selulosa gentian
teras kenaf telah diambilalih oleh kumpulan karboksimetil. Kajian mikroskop
pengimbasan elektron juga menyokong proses penukargantian terjadi, dimana
gentian teras kenaf yang tidak dimodifikasi mempunyai permukaan yang kasar
dengan pit yang masih kosong. Sebaliknya, permukaan yang licin dapat
diperhatikan daripada gentian yang dimodifikasi dengan menganggap pit terisi
dengan karboksimetil natrium monokloroasetat.
Hidrogel berjaya dihasilkan menggunakan larutan yang berkepekatan berbeza-
beza terdiri daripada karboksimetil gentian teras kenaf tanpa ekstraktif dan
lignin (KGTKTEL) pada beberapa dos sinaran. Didapati dos 70 kGy adalah
sinaran optimum untuk tautsilang oleh hidrogel KGTKTEL dengan kandungan
gel 37.1%. Keadaan tautsilang optimum adalah 50 kGy iradiasi dan 50%
kepekatan, menghasilkan sifat-sifat yang baik hidrogel KGTKTEL. Nisbah
ix
x
pembengkakan hidrogel KGTKTEL adalah tertinggi dalam air suling berbanding
dengan alkali (1.0 M NaOH) dan asid (1.0 M HCl) untuk semua peringkat dos
sinaran kecuali 10 kGy. Peningkatan tahap kepekatan KGTKTEL menunjukkan
peningkatan pembengkakan. Keputusan ini walaubagaimanapun menunjukkan
sebaliknya bila ujian pembengkakan dijalankan dalam media asid dan alkali.
Keseluruhan keputusan menunjukkan bahawa gentian teras batang kenaf boleh
digunakan sebagai bahan alternatif untuk penghasilan karboksimetil selulos
dan hidrogel dan menunjukkan sifat-sifat lain yang memuaskan.
ACKNOWLEDGEMENTS
In The Name of Allah, The Most Merciful and The Most Gracious.
First and foremost, I wish to express my deepest gratitude and appreciation to
my project supervisor, Associate Professor Dr. Paridah Md. Tahir for her
guidance, supervision and encouragement throughout the course of this study.
Appreciation is also extended to Dr. Kamaruddin Hashim, who continuously
helped me a lot throughout this project. I also wish to convey my thanks to
Associate Professor Dr. Mohamad Zaki Ab. Rahman, Professor Dr. Sarani
Zakaria and Associate Professor Dr. Jalaluddin Harun for their time and
support.
Special thanks are forwarded to Mrs Norzita and all Malaysian Nuclear Agency
staff, for their kindness, help and support towards the completion of this project.
The author is also indebted to Jabatan Perkhidmatan Awam (JPA) for
scholarship, not forgetting all the staffs of Faculty of Forestry for kindly providing
the facilities and assistance, and to everyone who have directly or indirectly
contributed in the completion of the experimental work.
Last but not least, my warmest gratitude is dedicated to my family, my
colleagues at SPTA, UMS and friends for their constant support, patience and
encouragement throughout my study.
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I certify that an Examination Committee met on 28 April 2008 to conduct the final examination of Ismawati Palle on her Master of Science thesis entitled “Carboxymethylation of Cellulose from Kenaf (Hibiscus cannabinus L.) Core for Hydrogel Production” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the student be awarded the degree of Master of Science. Members of the Examination Committee were as follows: Jegatheswaran Ratnasingam, PhD Associate Professor Faculty of Forestry Universiti Putra Malaysia (Chairman) H’ng Paik San, PhD Lecturer Faculty of Forestry Universiti Putra Malaysia (Internal Examiner) Nor Azowa Ibrahim, PhD Lecturer Faculty of Science Universiti Putra Malaysia (Internal Examiner) Khalil Shawkataly, PhD Associate Professor School of Bio Resource Industry Universiti Sains Malaysia (External Examiner)
____________________________ HASANAH MOHD. GHAZALI, PhD Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date : 22 July 2008
xii
This thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows: Paridah Md. Tahir, PhD Associate Professor Faculty of Forestry Universiti Putra Malaysia (Chairman) Jalaluddin Harun, PhD Associate Professor Faculty of Forestry Universiti Putra Malaysia (Member) Kamaruddin Hashim, PhD Senior Research Officer Malaysian Nuclear Agency (Member) Sarani Zakaria, PhD Professor School of Applied Physics Universiti Kebangsaan Malaysia (Member) Mohamad Zaki Ab. Rahman, PhD Associate Professor Faculty of Science Universiti Putra Malaysia (Member)
______________________ AINI IDERIS, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia
Date : 14 AUGUST 2008
xiii
xiv
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 it has not been previously or concurrently submitted for any other degree at UPM or other institutions.
__________________ ISMAWATI PALLE Date : 21 July 2008
TABLE OF CONTENTS Page DEDICATION ii ABSTRACT iii ABSTRAK vii ACKNOWLEDGEMENTS xi APPROVAL xii DECLARATION xiv LIST OF TABLES xix LIST OF FIGURES xx LIST OF ABBREVIATIONS xxiv CHAPTER 1
INTRODUCTION 1.1 Background of the Study 1.2 Statement of Problem and Justification 1.3 Objectives
1 6 7
2
LITERATURE REVIEW 2.1 Origin of Kenaf (Hibiscus cannabinus L.) 2.1.1 Kenaf as Raw Material in Biocomposite Industry 2.2 Factors Influencing the Use of Lignocellulosic Material as Raw Material for Cellulose Derivatives
2.2.1 Extractives 2.2.2 Lignin 2.2.3 Hemicellulose 2.2.4 Cellulose
2.3 Modification of Cellulose 2.3.1 Etherification of Cellulose 2.3.2 Alkali Cellulose
2.4 Carboxymethylation of Cellulose 2.4.1 Reaction Conditions for Carboxymethylation Process
Reaction Time Sodium Hydroxide Concentration Reaction Temperature Amount of Sodium Monochloroacetate Reaction Medium
2.4.2 Effect of Lignin and Extractive 2.5 Applications of CMC 2.6 Applications of CMC as Hydrogel
2.6.1 Hydrogel Formation by Irradiations 2.6.2 Factors Influencing the Irradiation of Hydrogels in Aqueous Conditions
9 11 16
18 19 21 22 24 25 27 28 31 31 32 34 35 36 38 40 41 42 44
xv
CMC Mixture (Paste Like) Concentration Irradiation Doses Degree of Substitution
2.7 Swelling Behaviour of Hydrogel 2.7.1 Swelling in Water 2.7.2 Swelling at Different pH
44 45 45 46 46 47
3
PROPERTIES OF KENAF CORE FIBRES 3.1 Introduction 3.2 Material and Methods
3.2.1 Separation of Bast and Core 3.2.2 Preparations of Kenaf Core for Chemical Analysis Chipping and Flaking of Kenaf Core Stem Screening Drying Fibre Separations 3.2.3 Preparations of Kenaf Core for Physical Properties Test Moisture Content Water Absorptions 3.2.4 Preparations of Kenaf Core for Fibre Morphology Fibre Morphology 3.2.5 Determination of Chemical Components of Kenaf Core Determination of pH Determination of Cold- and Hot Water Solubility Determination of Alcohol-Acetone Solubility Determination of Lignin Determination of Holocellulose Determination of Alpha-Cellulose Determination of Hemicellulose Determination of Ash
3.3 Results and Discussion 3.3.1 Physical Properties of Kenaf Core
Water Absorption 3.3.2 Fibre Morphology 3.3.3 Chemical Properties
3.4 Conclusions
49 51 53 54 54 55 55 56
56 56 57 58 58 59 61 61 62 63 64 65 66 66 67 67 68 70 74 77
4 CARBOXYMETHYLATION OF KENAF CORE 4.1 Introduction 4.2 Materials 4.3 Experimental Parameters
4.3.1 Synthesis of CMC from Crude Kenaf Core 4.3.2 Synthesis of CMC from Extractive-Free and Extractive- and Lignin-Free Kenaf Core 4.3.3 Determination of the Degree of Substitution
79 81 82 85 87
87
xvi
4.3.4 Determination of Reaction Efficiency 4.3.5 Determination of Weight Percent Gain
4.4 Characterization of Carboxymethylated Kenaf Core 4.4.1 Fourier Transform Infrared Analysis 4.4.2 Examination of Carboxymethylated Kenaf Core under SEM
4.5 Results and Discussion 4.5.1 Effect of Time 4.5.2 Effect of Sodium Hydroxide 4.5.3 Effect of Temperature 4.5.4 Effect of Extractive and Lignin on the Carboxymethylation of Kenaf Core 4.5.5 Fourier Transform Infrared Analysis of Carboxymethylated Kenaf Core 4.5.6 Morphology of Kenaf Core Fibre and Carboxymethylation Kenaf Core
4.6 Conclusions
88 89 90 90 90
91 91 94 96 99
102
106 107
5
FORMATION OF HYDROGEL FROM CARBOXYMETHYLATED KENAF CORE 5.1 Introduction 5.2 Material and Methods
5.2.1 Experimental Parameters 5.2.2 Preparations of CMKCFL Hydrogel by Electron Beam Irradiation 5.2.3 Determination of Gel Content of CMKCFL Hydrogel 5.2.4 Swelling Behaviour of CMKCFL Hydrogel 5.2.5 Examination of Morphology of CMKCFL Hydrogel
5.3 Results and Discussion 5.3.1 Formation of CMKCFL Hydrogel by Electron Beam Irradiation
Effect of Irradiation Dose on the Degree of Crosslinking of CMKCFL Effect of CMKCFL Paste-Like Concentration on Crosslinking of CMKCFL
5.3.2 Swelling Behaviour of CMKCFL Hydrogel Effect Irradiation Doses on Swelling in De-Ionized Water Effect of Irradiation Doses and Concentration on Swelling of CMKCFL Hydrogel in Alkaline and Acidic Medium Morphology of CMKCFL Hydrogel
5.4 Conclusions
108 110 110
112
112 114 114 115
115 116
118
119 120
121
123 126
6 OVERALL CONCLUSIONS AND RECOMMENDATIONS 6.1 Conclusions
128
xvii
LIST OF TABLES
TABLE PAGE
1.0 Chemical Content of Kenaf Core, Kenaf Bast in Comparison with OPEFB and Rubberwood
4
2.1 World Inventory of Biomass 11
2.2 Fibre Length of Kenaf and Wood 13
2.3 Chemical Constituents of Wood and Non-Wood Fibres 17
2.4 Industrial Applications of Cellulose Derivatives 26
2.5 Examples of Important Cellulose Esters and Ethers Commercially Produced
30
3.1 Fibre Morphology of Kenaf Core from Variety Tainung-2
71
3.2 Proximate Chemical Component of Kenaf Core from Different Kenaf Varieties
74
4.1 Infrared Band Assignments for Kenaf Core Fibres
104
4.2 Infrared Band Assignments for Carboxymethylation Kenaf Core 105
xix
LIST OF FIGURES FIGURE PAGE
2.1 (a) Kenaf Plant and (b) Different Part of Kenaf (Source: Nishimura et al., 2002)
9
2.2 Comparison of Tensile Strength Kenaf/PP-MAPP Composites to Other Natural Fibre Composites (Source: Zampaloni et al., 2007)
14
2.3 Comparison of Flexural Strength of Kenaf/PP-MAPP Composites to Other Natural Fibre Composites (Source: Zampaloni et al., 2007)
14
2.4 Basic Structural Unit of Lignin (Source: Petterson, 1984) 19
2.5 Structure of Cellulose (Source: Hons and Shiraishi, 1991) 23
2.6 A Typical Structure of Carboxymethyl Cellulose (Source: Merle et al., 1999)
29
2.7 Crosslinking Mechanism of CMC by Electron Beam Irradiation 43
2.8 Scheme of Hydrogel Network, Circle Denote Available Space for Diffusion. In the Insert Four Functional (a) and Trifunctional (b) Points of Chains Junction are Shown (Source: Rosiak et al., 1995)
47
3.1 Preparations of Kenaf Core Powder for Chemical Analysis and Determination of Fibre Morphology and Water Absorption
52
3.2 Separation of Kenaf Stalk into Core and Bast 53
3.3 Preparations of Raw Material (a) Chipping (b) Flaking (c) Kenaf Core after Chipping (d) and kenaf Core After Flaking
54
3.4 A Vibrating Screen Used for Separating the Particles 55
3.5 Sample Preparation for Water Absorption Test 57
3.6 Image Analyzer (Leitz DMRB) used for Determining the Fibre Morphology
59
3.7 Isolation of Pure Cellulose from Crude Kenaf Core 60
xx
3.8 The degree of Water Absorption of Kenaf Core over Time 68
3.9 SEM Obtained from Kenaf Core: (a) Radial Section at 1200X Magnification, (b) Tangential Section at 1200X Magnification
69
3.10 The Various Types of Pits in Wood (Source: Haygreen and
Bowyer, 1989)
70
3.11 (a) Transverse Kenaf Core at 40X Magnification (b) Vessel in a Single Cell at 40X Magnification
72
3.12 SEM obtained from Kenaf Core Samples (a) Cross-Section of Kenaf Core at 35X Magnification, (b) Kenaf Core Centre at 1200X Magnification, (c) Kenaf Core Outer Section at 1200X Magnification and (d) Radial Section of Kenaf Core at 1200X Magnification, (P) Pits
73
4.1 Experimental Design for the Production of Carboxymethyl Cellulose from Crude Kenaf Core
83
4.2 Reaction Condition Adopted for the Production of Carboxymethyl Cellulose from Kenaf Core Extractive-Free (KCFE) and Kenaf Core Extractive- and Lignin-Free (KCFL)
84
4.3 Procedure to Synthesize CMC from Kenaf Core 86
4.4 Effect of Reaction Time on Degree of Substitutions (DS) of Carboxymethylated Crude Kenaf Core (CMCKC)
92
4.5 Effect of Reaction Time on Reaction Efficiency (%RE) and Weight Percent Gain (%WPG) of CMCKC
93
4.6 Effect of NaOH Concentration on Degree of Substitutions (DS) of CMCKC
94
4.7 Effect of NaOH Concentrations on Reaction Efficiency (%RE) and Weight Percent Gain (%WPG) of CMCKC
96
4.8 Effect of Temperature on Degree of Substitutions (DS) of CMCKC
97
4.9 Effect of Temperature on Reaction Efficiency (%RE) and Weight Percent Gain (%WPG) of CMCKC
98
4.10 Effects of Extractive and Lignin on Degree of Substitutions (DS) of CMCKC, CMKCFE and CMKCFL
100
xxi
4.11 Effects of Extractive and Lignin on Reaction Efficiency (%RE) and Weight Percent Gain (%WPG) of CMCKC, CMKCFE and CMKCFL
101
4.12 IR Spectrum of Kenaf Core 104
4.13 IR Spectrum of Carboxymethylation Kenaf Core 105
4.14 SEM Obtained from Kenaf Core Fibres: (a) Kenaf Core Fibre at 800X Magnification and (b) Carboxymethylation Kenaf Core at 800X Magnification
106
5.1 Experimental Design for Hydrogel Production from Carboxymethylated Kenaf Core Extractive- and Lignin-Free
111
5.2 Procedure to Synthesize Hydrogel from Carboxymethylated Kenaf Core Extractive- and Lignin-Free
113
5.3 Hydrogel Produced from Carboxymethylated Kenaf Core Extractive- and Lignin-Free (CMKCFL)
116
5.4 Effect of Irradiation Dose on Gel Content of CMKCFL Hydrogel (50% Concentration)
117
5.5 Effect of Paste-Like Concentration on the Gel Content of CMKCFL Hydrogel Irradiation at 50 kGy
119
5.6 Swelling of CMKCFL Hydrogel (50% Concentration) in Distilled Water for 48 Hours
120
5.7 Swelling of CMKCFL Hydrogel (50% Concentration) in Distilled Water, Alkali (1.0 M NaOH) and Acid (1.0 M HCl) after 48 Hours
121
5.8 CMKCFL hydrogel (brown colour) before soaking and white/yellowish after soaking for 48 hours in (a) distilled water, (b) 1.0 M NaOH and (c) 1.0 M HCl
122
5.9 Swelling of CMKCFL Hydrogel Irradiated at 50 kGy in Distilled Water, Alkali (1.0 M NaOH) and Acid (1.0 M HCl) after 48 Hours
123
5.10 SEM of 50% Paste-Like Concentration of Hydrogel at Different Irradiation Doses: (a) 25 kGy at 200X Magnification, (b) 40 kGy at 200X Magnification, (c) 50 kGy at 200X Magnification, (d) 70 kGy at 100X Magnification, (e) 80 kGy at 200X Magnification and (f) 100 kGy at 200X Magnification
125
xxii