UNIVERSITI PUTRA MALAYSIA

CHARACTERISATIONS OF KRAFT PULP AND PAPER PROPERTIES FROM ACACIA AURICULIFORMIS A. CUNN.

EX BENTH.- A CONFOCAL MICROSCOPY ANALYSIS

LIEW KANG CHIANG

FH 2002 1

CHARACTERISATIONS OF KRAFT PULP AND PAPER PROPERTIES FROM ACACIA AURICUUFORMIS A. CUNN. EX BENTH. - A CONFOCAL

MICROSCOPY ANALYSIS

By

LIEW KANG CHIANG

Thesis Submitted in Fulfilment of the Requirement for the Degree of Doctor of Philosophy in the Faculty of Forestry

Universiti Putra Malaysia

January 2 002

Abstract of thesis submitted to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Doctor of Philosophy

CHARACTERISATIONS OF KRAFT PULP AND PAPER PROPERTIES FROM ACACIA AURICUUFORMIS A. CUNN. EX BENTH. - A CONFOCAL

MICROSCOPY ANALYSIS

By

LIEW KANG CHIANG

January 2 002

Chairman : Dr. Jalaluddin Harun

Faculty : Forestry

This study was carried out to characterise the transverse dimensions of mechanically

treated (beaten) kraft Acacia auriculiformis pulp (AAP) and mixed tropical

hardwood commercial pulp (MTHCP) fibres using the fast and non-destructive

method of optical sectioning ability of confocal laser scanning microscopy. Also

included in the study are the determination of chemical constituents, fibre

morphologies using the image analyser and the optimum pulping conditions.

Laboratory handsheets were produced using pulps beaten at varying beating degrees

using the PFI mill, and evaluated for their physical and mechanical properties.

Established standards were followed throughout the study.

Results from the chemical constituents and fibre morphology determinations for A.

auriculiformis sample were within the comparable range of previous studies.

Optimum kraft pulping conditions was achieved at 1 9% active alkali for A.

auriculiformis wood chips with a 5 1 .9% screened yield, 0.085% reject and Kappa

number 1 9. 1 . Laboratory handsheets were produced from AAP and MTHCP fibres

ii

that were beaten using the PFI mill, at 3 beating degrees; 0, 5000 and 10000

revolutions. Generally, the AAP fibres exhibited comparable, if not better, physical

and mechanical properties than MTHCP. As beating progressed, pulp freeness

decreased with increasing drainage time. This has resulted the tensile strength,

bursting strength, tearing resistance, and folding endurance to increase but an inverse

for bulk and air permeance.

Beaten and unbeaten fibre cross-sectional images were generated under epi­

fluorescent mode, and different fibre cross-sectional images can be observed, with

unbeaten fibres usually uncollapsed to partial and fully collapsed fibres of beaten

fibres. Generally, transverse dimensions determined from image analysis were found

to decrease in centreline perimeter, lumen area, fibre area, lumen perimeter, fibre

thickness, fibre wall thickness, and aspect ratio except for fibre width and collapse

index, due to the beating process. In general, it was found that AAP has lower fibre

transverse dimensions than MTHCP.

Regression equations were built usmg the Maximum R Improvement method

involving pulp and paper properties and calculated fibre transverse dimensions.

Predictions were done at a beating range of 0-1 0000 rev. with CI dominantly

influenced the pulp and paper properties in the I-variable equations, followed by the

inclusion of AR in most of the 2-variable equations for AAP and MTHCP. The

correlation coefficients for fibre transverse dimensions indicated positive

relationships with freeness, bulk, tear index and air permeance whilst negative with

drainage time, tensile index, breaking length, burst index and fold.

III

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Doktor Falsafah

PENCIRIAN SIFAT PULPA KRAFT DAN KERTAS DARIACACIA AURICUUFORMIS A. CUNN. EX BENTH. - ANALISIS KONFOKAL

MIKROSKOPI

Oleh

LIEW KANG CHIANG

Januari2 002

Pengerusi : Dr. Jalaluddin Harun

Fakulti : Perhutanan

Penyelidikan ini dijalankan untuk mencirikan beberapa dimensi merentas gentian

pulpa kraft Acacia auriculiformis (AAP) dan pulpa komersial kayu keras tropika

campuran (MTHCP) secara mekanikal menggunakan keupayaan pemotongan optikal

mikroskopi konfokal imbasan laser yang merupakan kaedah yang cepat dan tidak

memusnahkan. Kajian di dalam penyelidikan ini merangkumi penentuan kandungan

kimia, morfologi gentian menggunakan alat penganalisa imej dan keadaan

pempulpaan optimum. Kertas makmal dibuat menggunakan pulpa yang dipukul

pada pelbagai takat menggunakan pemukul PFI, dan beberapa ujian dijalankan untuk

mengkaji sifat-sifat fizikal dan mekanikal mereka. Piawaian digunakan sepanjang

penyelidikan dijalankan.

Keputusan daripada penentuan kandungan kimia dan morfologi gentian pada sampeJ

A. auriculiformis adalah tergolong dalam julat perbandingan dengan penyelidikan

dahulu. Pempulpaan optimum didapati pada kegunaan 1 9% aktif alkali dengan hasil

bertapis 5 1 .9%, hasil terbuang 0.085% dan nombor Kappa 19. 1 . Kertas makmal

iv

dihasiIkan daripada gentian AAP dan MTHCP, dipukul menggunakan PFI, pada 3

takat pukulan, 0, 5000 dan 1 0000 revolusi . Pada amnya, gentian AAP menunjukkan

sifat-sifat fizik dan mekanik yang setanding atau lebih baik berbanding dengan

MTHCP. Apabila pukulan diteruskan, kebebasan pulpa menurun dengan

peningkatan masa pengaliran. Ini mengakibatkan kekuatan regangan, pecahan,

koyakan, dan l ipatan kertas meningkat tetapi keputusan sebaliknya bagi sifat pukal

dan penembusan angin.

Beberapa imej keratan-rentas gentian yang tidak dipukul dan dipukul dijana di bawah

mod "epi-fluorescent", dan imej keratan-rentas gentian boleh dilihat; dengan gentian

yang tidak dipukul biasanya tidak runtuh kepada runtuhan sebahagian dan runtuh

sepenuhnya bagi gentian yang dipukul. Pad a amnya, dimensi merentas ditentukan

daripada analisa imej didapati menurun dalam lilitan garisan tengah, ruangan lumen,

ruangan gentian, lilitan lumen, ketebalan gentian, ketebalan din ding gentian, nisbah

aspek kecuali bagi kelebaran gentian dan indek keruntuhan, disebabkan oleh proses

pukulan. Pad a amnya, didapati AAP mempunyai dimensi-dimensi merentas gentian

yang 1ebih rendah daripada MTHCP.

Formula regresi dibuat menggunakan kaedah "Maximum R Improvement" yang

melibatkan sifat-sifat pulpa dan kertas dan dimensi merentas gentian yang dikira.

Ramalan dilakukan pada julat pukulan 0- 10000 rev. dengan CI mempengaruhi kukuh

sifat-sifat pulpa dan kertas dalam persamaan I-pembolehubah, dengan diikuti oleh

AR dalam kebanyakan persamaan 2-pembolehubah untuk AAP dan MTHCP.

Perkaitan koeffisien untuk dimensi merentas gentian menunjukkan hubungan positif

dengan kebebasan, sifat pukal, indek koyakan dan penembusan angin semen tara

v

r )"'��:�J'''1

TNIVE�;Slll l' U 1 ,,1,. .-,.h,LAYSIA negatif dengan masa pengaliran, indek regangatt, '1cepanJangan memutus, mdek

pecahan dan lipatan.

vi

ACKNOWLEDGEMENTS

The author wishes to express his sincere gratitude to his supervisory committee

consisting of Dr. lalaluddin Harun (Universiti Putra Malaysia), Dr. Sarani Zakaria

(Universiti Kebangsaan Malaysia) and Dr. Mohd. Nor Mohd. Yusoff (Forest

Research Institute of Malaysia) for their invaluable guidance and comments.

Acknowledgements are extended to the staffs of Centre for Electron Microscopy and

Imaging System, Institute of Bioscience, Universiti Putra Malaysia especially to Ms.

Suleka Madhavan and Mr. Ho Oi Kuan for their assistance in conducting the image

acquisition. Many thanks to Mr. Y ong Fook Onn from Pulp and Paper Laboratory of

Forest Research Institute of Malaysia for pulp and paper evaluations and Dr. Anuar

Abdul Rahim for the statistical analysis . Word of thanks are also conveyed to the

Dean of the Faculty of Forestry, Universiti Putra Malaysia for his permission to the

use the available facilities throughout the course of this study. Acknowledgement is

also due to Universiti Putra Malaysia for sponsoring the author's study through the

PASCA scheme and to those involved directly or indirectly in the completion of his

study.

Lastly, the author would like to dedicate his deepest gratitude to his family members

and friends for their support and encouragement.

vii

I certify that an Examination Committee met on 1 1th January 2002 to conduct the final examination of Liew Kang Chiang on his Doctor of Philosophy thesis entitled "Characterisations of Kraft Pulp and Paper Properties from Acacia auriculiformis A. Cunn. ex Benth. - A Confocal Microscopy Analysis" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1 980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1 98 1 . The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

PARIDAH MD. TAHIR, Ph.D Lecturer Faculty of Forestry Universiti Putra Malaysia (Chairman)

JALALUDDIN HARUN, Ph.D Lecturer Faculty of Forestry Universiti Putra Malaysia (Member)

SARANI ZAKARIA, Ph.D Lecturer School of Applied Physics Faculty of Science and Technology Universiti Kebangsaan Malaysia (Member)

MOHD. NOR MOHD. YUSOFF, Ph.D Director Wood Chemistry Division Forest Research Institute of Malaysia (Member)

KEN (KWEI-NAM) LAW, Ph.D Senior Research Scientist Pulp and Paper Research Center Universite du Quebec a Trois-Rivieres (Independent Examiner)

viii

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

Date: 1 6 JAN 2002

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

IX

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

Date: 14 � 1002

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 Universiti Putra Malaysia or other institutions.

Date: 1 6 JAN 2002

x

ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL SHEETS DECLARATION LIST OF TABLES LIST OF FIGURES

TABLE OF CONTENTS

LIST OF ABBREVIATIONS

CHAPTER

Page ii iv Vll VIlI x

xiii xv

X V III

1 INTRODUCTION 1

2 LITERATURE REVIEW 6 2.1 General Overview 6 2.2 Acacia auriculiformis A. Cunn. ex Benth. 6 2.3 Chemical Constituents of Wood 9

2.3.1 Cellulose 10 2.3.2 Hemicellulose 12 2.3.3 Lignin 13 2.3.4 Extraneous Materials 14

2.4 Hardwood Fibre Morphology 14 2.4.1 Fibre Length 16 2.4.2 Fibre Wall Thickness 17 2.4.3 Fibre Flexibility and Collapsibility 18

2.5 Kraft Pulping 19 2.6 Mechanical Treatment and Their Effect on Fibre and Paper

Properties 20 2.7 Confocal Laser Scanning Microscopy 26

2.7.1 The Principle 26 2.7.2 Confocal Techniques and Their Advantages 29 2.7.3 Application of CLSM in Pulp and Paper Research 33

3 RAW MATERIAL PREPARATION AND PROPERTIES OF ACACIA AURICUUFORMIS WOOD 38 3.1 General Overview 38 3.2 Raw Material 38

3.2.1 Apparent Density Determination 42 3.2.2 Proximate Chemical Analysis Determination 42 3.2.3 Fibre Morphology Determination Using Image Analyser 43

3.3 Results and Discussion 44 3.3.1 Wood Apparent Density 44 3.3.2 Proximate Chemical Analysis 45 3.3.3 Fibre Morphology 54

xi

4 KRAFT PULPING AND PAPER PROPERTIES 62 4.1 General Overview 62 4.2 Pulp Preparation 62 4.3 Kappa Number Determination 65 4.4 Fibre Classification 65 4.5 Handsheet Making and Evaluations 66 4.6 Scanning Electron Microscopy 68 4.7 Statistical Analysis 68 4.8 Results and Discussion 69

4.8.1 Pulping Properties 69 4.8.2 Fibre Classification 70 4.8.3 Pulp and Paper Properties 72

5 SAMPLE PREPARATION AND CONFOCAL LASER SCANNING MICROSCOPY OF WOOD PULP FIBRES 86 5.1 General Overview 86 5.2 Slide Preparation 86 5.3 Confocal Laser Scanning Microscopy 88

5.3.1 Image Acquisition 88 5.3.2 Image Processing and Analysis 91

5.4 Statistical Analysis 97 5.5 Results and Discussion 98

5.5.1 Fibre Cross-Sectional Images 98 5.5.2 Transverse Dimensions Measurements 98 5.5.3 Relationships of Different Variables Studied 115

6 CONCLUSIONS AND RECOMMENDATIONS 125 6.1 Conclusions 125 6.2 Recommendations 127

REFERENCES 129

BIODATA OF THE AUTHOR 143

xii

LIST OF TABLES

Table

2.1 CLSM imaging techniques and their descriptions (Anonymous

Page

2000). 31

3.1 Information of individual standing tree. 40

3.2 Individual apparent density of different disc portions at different tree heights for the sampled A. auriculiformis trees. 45

3.3 Wood apparent density of A. auriculiformis of different ages and planting sites. 45

3.4 Proximate chemical analysis for A. auriculiformis wood meal, AAP and MTHCP compared to other studies. 46

3.5 The influence of wood chemical properties on pulp properties (Amidon 1981). 48

3.6 Comparison of fibre morphology for A. auriculiformis used in this study with other A. auriculiformis and other fast-growing plantation species. 55

4.1 Preliminary pulping studies. 64

4.2

4.3

4.4

4.5

4.6

5.1

5.2

Pulping properties of A. auriculiformis from different researchers and MTHCP.

Fibre classification of AAP and MTHCP fibres at different beating degrees.

Summary of analysis of variance for the effects of beating on the paper properties of AAP and MTHCP fibres.

Pulp and paper properties of AAP and MTHCP fibres at different beating degrees.

Correlation coefficients of pulp and paper properties for AAP and MTHCP at different beating degrees.

Calibration factors for image analysis from image acquisition programme.

Summary of analysis of variance for the effects of beating on the transverse dimensions of AAP and MTHCP fibres.

5.3 Transverse dimensions of AAP and MTHCP fibres at different beating degrees as compared to other pulp fibres.

xiii

70

71

73

74

78

91

103

104

5.4 Correlation coefficients of fibre transverse dimensions for AAP and MTHCP at different beating degrees. 107

5.5 Regression equations for pulp and paper properties at different calculated fibre transverse dimensions for AAP fibres beaten at different beating levels using PFI mill. 116

5.6 Regression equations for pulp and paper properties at different calculated fibre transverse dimensions for MTHCP fibres beaten at different beating levels using PFI mill. 117

5.7 Correlation coefficients between fibre transverse dimensions and pulp and paper properties with regards to AAP and MTHCP at different beating degrees. 123

xiv

Figure

2.1

2.2

2.3

2.4

2.5

2.6

3.1

3.2

LIST OF FIGURES

Various bar actions on pulp fibres (Clark 1985).

Effect of bars on fibres (Clark 1985).

The confocal principle (Moss et al . 1993).

Optical sectioning in the x-y plane (Moss et al . 1993).

Transmitted light image (left) with many fibres seen but only some in focus while confocal image (right) at the same area shows only fibres in the in-focus plane. Magnification: Not available (Moss et al . 1993).

Photomicrograph showing distorted cross-section of A. auriculiformis fibres using the normal microtome sectioning method. Magnification: 2000X.

Flow chart of experimental procedures for raw material preparation and properties of A. auriculiformis wood.

Location of Peninsular Malaysia showing UPM's Experimental Farm at latitude 3° 2' N, longitude 101° 42' E.

3.3 Breakdown of wood billet and branches in raw material preparation.

3.4

3.5

4.1

4.2

4.3

Position of apparent density blocks in a disc cross-section.

Schematic representation of the layered structure of a single wood fibre (Page 1969). e is the fibril angle of S2 layer. P=Primary wall, S,=Outer secondary wall layer, S2=Middle secondary wall layer, S3=Inner secondary wall layer.

Flow chart of experimental procedures for Kraft pulping and paper properties evaluations.

Photomicrographs showing fibre wall fibrillations for AAP at different beating degrees; (a) 0 rev. , (b) 5000 rev. and (c) 10000 rev. Magnification: 2000X.

Photomicrographs showing fibre wall fibrillations for MTHCP at different beating degrees; (a) 0 rev. , Magnification: 2000X, (b) 5000 rev. , Magnification: 2000X and (c) 10000 rev., Magnification: 1500X.

xv

Page

22

22

27

28

29

32

39

40

41

42

59

63

76

77

4.4 Photomicrographs showing fibre networks in handsheets for AAP at different beating degrees; (a) 0 rev. , (b) 5000 rev. and (c) 10000 rev. Magnification: I000X. 80

4.5 Photomicrographs showing fibre networks in handsheets for MTHCP at different beating degrees; (a) 0 rev. , (b) 5000 rev. and (c) 1 0000 rev. Magnification: 1OOOX. 8 1

5 . 1 Flow chart of experimental procedures for sample preparation and confocal laser scanning microscopy of wood pulp fibres. 87

5.2 Bio-Rad MRC- 1024ES confocal imaging system. 89

5 .3 Viewing method for optical sectioning to obtain fibre cross-sectional images. 90

5 .4 Image analysis procedure to determine fibre cross-sectional area and perimeter: (a) original confocal image, (b) image smoothed by a median (or Gaussian) filter, (c) edges found by using the maximum local gradient, (d) edges smoothed and (e) thinned to such an extent that fibre surface was still well connected, (f) grey-level edges threshold to binary, (g) another thinning applied to reduce the boundaries to a single pixel thickness, (h) the region between the outer and inner boundaries filled, and a pixel-wide centreline superimposed on to the fibre cross-section (Jang et al. 1 992). White lines drawn across the images were used to generate line intensity profile for the image processing effect. Sample: unbeaten AAP. 92

5.5 Line intensity profile for image analysis procedure to determine fibre cross-sectional area and perimeter: (a) original confocal image, (b) image smoothed by a median (or Gaussian) filter, (c) edges found by using the maximum local gradient, (d) edges smoothed and (e) thinned to such an extent that fibre surface was still well connected, (f) grey-level edges threshold to binary, (g) another thinning applied to reduce the boundaries to a single pixel thickness, (h) the region between the outer and inner boundaries filled, and a pixel-wide centreline superimposed on to the fibre cross-section. 93

5.6 Not collapsed fibre properties determined by image analysis : A, fibre cross-sectional area; LA, lumen area; P, centreline perimeter; T, mean fibre-wall thickness (T = AlP); Dmax, fibre width (longest Feret diameter of fibre); Dmm, fibre thickness (shortest Feret diameter of fibre); aspect ratio (AR = DmmlDmax); W (projected width) (Jang et al. 1996). 95

xvi

5 .7 Partially collapsed fibre properties determined by image analysis: Mean wall thickness (T = AlP); lumen perimeter (LP =

perimeters of both collapsed and uncollapsed portions) (Jang and Seth 1 998). 95

5 .8 Photomicrograph showing the diffuse-porous structure of A. auriculiformis at cross-section. Magnification: 20X. 96

5.9 Typical cross-sectional images of unbeaten AAP fibres. Scale bar = 5 �m (Liew 2000b) . 99

5 . 1 0 Typical cross-sectional images of unbeaten MTHCP fibres. Scale bar = 5 �m. 1 00

5 . 1 1 Different dimensions, (a) to (d), of typical cross-sectional images of unbeaten, unbleached Western Canadian spruce kraft pulp fibres obtained by confocal microscopy (Jang and Seth 1 998). 101

5 .l2 Different degrees of collapse: (A) original fibre, (B) partially collapsed fibre, and (C, D) completely collapsed fibres (Jayme and Hunger 1 96 1 ). 10 1

5 . 1 3 Typical cross-sectional images of pulp fibres at different beating degrees for AAP fibre [(a) 0 rev. , (b) 5000 rev. , (c) 1 0000 rev.] and MTHCP fibre [(d) 0 rev., (e) 5000 rev., (f) 1 0000 rev.]. Scale bar = 5 �m (Liew 2000a). 1 02

5 . l 4 Summary of morphological changes i n Buna (Japanese beech) fibres with the progress of beating (Nanko et al. 1 989). CSF for cross sections from top to bottom: unbeaten (freeness not available), 540, 355 and 1 50 ml, respectively. 1 10

XVll

AAP

MTHCP

rev.

a.a.

CLSM

CP

LA

FA

LP

Dmax

Dmin

PW

WT

AR

CI

LIST OF ABBREVIATIONS

1 9% Acacia auriculiformis pulp

Mixed tropical hardwood commercial pulp

Revolutions

Active alkali

Confocal laser scanning microscopy

Centreline perimeter

Lumen area

Fibre area

Lumen perimeter

Fibre width

Fibre thickness

Projected width

Fibre wall thickness

Aspect ratio

Collapse index

XVlll

CHAPTERl

INTRODUCTION

In recent years, forest-based supply of the world has been declining. As the demand

for wood increases with the increasing popul<l:tions and incomes, forests are rapidly

cleared and degraded, withdrawn from production for conservation purposes or other

reasons, leaving the saddle to the remaining production forests (Brown and Ball

2000). The decline became evident in the last 30 years and prompted the

intensification of reforestation with natural or exotic trees i.e. Pinus spp. , Eucalyptus

spp., Picea spp., Abies spp., Larix spp., Tectona spp., Araucaria spp. and Acacia spp.

In Malaysia, the Compensatory Forest Plantation Project was launched in 1 982,

aimed at establishing 1 88,000 ha of fast-growing species of trees within a 1 5 year­

period. The objective of this project was to supplement the projected shortage of

timber to meet domestic consumption in the mid 1 990's . Among the species planted

were Acacia mangium, Gmelina arborea and Paraserianthes Jalcataria (Mohd. Nor

and Salleh 1 992).

Another Acacia spp., Acacia auriculiformis was also introduced and planted at

degraded sites such as tin tailing areas in Peninsular Malaysia (Ang 1 986, Ang and

Yusuf 1 989, Ang 1 99 1 ) and in reforestation tree project in Sarawak (Joseph 1 992).

A. auriculi formis A. Cunn. ex Benth. is a mUltipurpose, leguminous tree in the

subfamily Mimosoideae, and grow naturally in Australia, Papua New Guinea and

Indonesia. It is a vigorous, nitrogen-fixing tree with an outstanding ability to grow

well on harsh sites and on different types of soil in the tropics, including very

infertile, clayey, saline and seasonally-waterlogged soils (Turnbull 1986). Doran and

Turnbull ( 1 997) add that the trees could also tolerate acidic, alkaline and moderate

dry seasons making them a very useful species for the rehabilitation of degraded

lands. This species is also better known outside its natural range of distribution as

the most adaptable species of all kinds of tree planting programmes in tropical humid

and subhumid lowland regions (Pinyopusarerk 1 990). It is widely cultivated as an

exotic plant in Asia, Africa and South America and increasingly used for

reforestation in new areas. In southeast Asia, A. auriculiformis is planted for

fuel wood purposes, erosion control, ornament or shade and a promising species for

pulpwood production (Turnbull 1 986). Doran and Turnbull ( 1 997) added that with

significant improvement on their stem form by selection and breeding would provide

outstanding prospects for industrial plantations to produce paper pulp and other

timber by-products.

In Malaysia, there are currently 1 8 paper mills utilising mainly waste paper and only

one integrated pulp and paper mill in Sabah, namely the Sabah Forest Industries Sdn.

Bhd. (Lai 1 997), that is utilising fibres from their plantation grown Acacia spp., A.

mangium. A. mangium also has proven to produce excellent particleboard - a type of

wood composite (Tham 1 976). Therefore, there is a need to evaluate the suitability

of planted A. auriculiformis as a source of wood, especially pulpwood. In pulp and

paper, much work was done in evaluating its pulping feasibility and paper properties

(Guha and Pant 1966, Phillips and Logan 1976, Phillips et al. 1 979, Logan and

Balodis 1 982, Mohd. Nor et al . 1 986). Logan ( 1 987) found that the plantation-grown

trees had the potential for the production of unbleached kraft pulp (for bags,

2

wrapping paper, linerboard) and high quality neutral sulfite semichemical pulp (for

corrugating, medium and higher-grade packaging-type products). The sulfate

process with 1 3% alkali yields up to 55% of screened pulp and is therefore less

suitable for high-yield mechanical pulps (Phillips et al . 1 979).

Different pulping processes and conditions, pulp refining and other pulp processing

treatments, and product furnish compositions were used to modify and enhance

certain papermaking and product properties and behaviours. Pulp fibres, which are

tubular in shape, can be changed. In papermaking, mechanical treatment of beating

process is used to collapse the fibres' shapes. It introduces external forces to the

fibres, which subsequently changes their native cross-sectional shape and collapsed

(J ang and Seth 1 998, J ang et al. 1 996). J ang and Seth ( 1 998) stated that these fibre

cross-sectional properties could be measured accurately with the help of image

analysis, therefore enabling the examination of the nature of changes in fibres with

mechanical treatment. In addition, the development of automated computer based

image analysis systems over the last 1 5 years (Ilic and Hillis 1 983, Lee and Rosen

1 985, Schnell and Sell 1 989, Peachey and Osborne 1 990, Evans 1 994, Russ 1 995,

Van der Heijden et al. 1 995, Diao et al. 1 996) has greatly improved the speed and

accuracy with which wood cell dimensions can be measured, either for wood

anatomical descriptions or for wood quality assessment. With this information on

fibre morphology and fibre transverse dimensions could facilitate the determination

of the ultimate product qualities, and whether or not certain products can be

produced from certain fibres or fibre furnishes (Kibblewhite and Bailey 1 988).

3

The conventional light microscopy is a time consuming and expensive sample

preparation, often involving embedding, sectioning and staining of the specimen.

Such technique generally allows the measurement of large numbers of cells but at

poor resolution or with limited accuracy (Donaldson and Lausberg 1 998). These

limitations were overcome with by the introduction of the current technology of

confocal laser scanning microscopy (CLSM) that has found wide applications in the

biological sciences as well as material sciences. It is a relatively new light

microscopial imaging technique introduced around 1980 by M. Petran and A. Boyde

(Pawley 1 990, Boyde 1994). The primary value of the CLSM to the scientists is its

ability to produce optical sections through a 3-dimensional (3-D) specimen - e.g.,

living materials such as an entire cell or a piece of tissue, non-living materials such

as circuit boards or electronic chips. This ability could produce information from

only one focal plane to a good approximation and able to solve 3-D biological or

material problems where information from regions distant from the plane of focus

can obscure the image of thick objects. Digital confocal images generated from this

computer-controlled CLSM are amendable to image processing and analysis

(Anonymous 200 1 ). These advantages could be utilised in this study to generate

information on the fibres' transverse dimensions for the plantation-grown A.

auriculiformis hardwood. Currently, the information on their fibre cross-sectional

properties for use in pulp and paper research, whether as individual fibre or within a

population of fibres, is not available. Therefore, in this study, kraft pulp fibres of A.

auriculiformis were prepared, treated mechanically and viewed under

epifluorescence mode, and compared with mixed tropical hardwood commercial pulp

(MTHCP). Cross-sectional images are generated, using the optical sectioning ability

from the CLSM. Later, the images were processed and analysed using image

4

'I' " i ' r

JNJVBI��( I! • L ,I�,'\. ;,ul.LAYSfA analysis for their transverse/cross-sectional dimensions. This study specifically

aims:

(a) To determine the chemical constituents of A. auriculiformis, and their fibre

morphology using the image analyser.

(b) To determine the optimum pulping conditions for A. auriculiformis wood

chips, prepare laboratory handsheets from the pulp produced at various

beating degrees and evaluate their physical and mechanical properties.

(c) To generate cross-sectional images of A. auriculi formis kraft pulp fibres

beaten at various beating degrees using the CLSM and determine their cross-

sectional dimensions using the image analysis software.

(d) To evaluate the relationships of laboratory handsheet properties with

different calculated fibre transverse dimensions, and the correlations between

the fibre transverse dimensions and pulp and paper properties with the

beating.

5

CHAPTER 2

LITERATURE REVIEW

2.1 General Overview

This chapter presents a review of l iterature regarding A. auriculi formis, chemical

constituents of its wood, fibre morphology, kraft pulping and paper properties, and

CLSM.

2.2 Acacia auriculiformis A. Cunn. ex Benth.

The genus Acacia comprised about 1 , 1 00 species where 850 occur in Australia,

Papua New Guinea and Indonesia. It is an exotic tree to Malaysia where nine species

have been introduced; A. mangium, A. auriculiformis, A. crassicarpa, A.

aulacocarpa, A. holosericea, A. cincinnata, A. farnesiana, A. podalyriaefolia and A.

richii (Boland et al . 1 984).

Acacia auriculi formis is a nitrogen-fixing member of the family Leguminoseae, sub­

family Mimosoideae. Its natural occurrence is in Papua New Guinea, islands of the

Torres Straits, Northern Australia and Queensland to 1 5°S (Jackson 1994). Its

botanical name of Acacia auriculiformis A. Cunn. ex Benth. came from the Latin

name auricula - external ear of animals, forma - form, figure or shape in allusion to