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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
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