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

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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

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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

xviii

6.2 Recommendations

129

REFERENCES 131 APPENDIX 141 BIODATA OF THE STUDENT 142

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

5.11 SEM of CMKCFL Hydrogel with Different Paste-Like Concentrations at 50 kGy: (a) 50% Paste-Like Concentrations and (b) 70% Paste-Like Concentrations at 200X Magnification

126

xxiii