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UNIVERSITI PUTRA MALAYSIA
ACETYLATION OF ACACIA MANGI UM WOOD FIBRES AND ITS APPLICATION IN THE
MEDIUM DENSITY FIBREBOARD
SINING UNCHI
FH 1996 5
ACETYLATION OF Acacia mangi um WOOD FIBRES
AND ITS APPLICATION IN THE MEDIUM DENSITY FIBREBOARD
BY
SINING UNCHI
Dissertation Submitted in fulfilment of the Requirements for the Degree of
Doctor of Philosophy in the Faculty of Forestry,
Universiti Pertanian Malaysia.
June 1996
ACKNOWLEDGEMENTS
I am greatly indebted t o As s o c . Prof . M ohd . Z in Ju s oh , Chai rman o f the Supervi sory Commi t tee , f or his constant guidance , assistance and sugges t i ons throughout the preparat i on o f thi s the s i s . I w ou l d al s o l ike t o expre s s my pro f ound grat i tude to Dr . Jalaluddin Harun and Assoc . Prof . Dr . Fauj an Ahmad for the i r invaluable sugge stions and c onstruct ive comment s .
S i n c e r e g r a t i t u d e i s d u e t o t h e S ab a h S t a t e G ov e r nm e n t f o r t h e s c h o l a r s h i p g r a n t . S i n c e r e appre c i a t i on i s a l s o d i rec ted t o the Publ i c S e rvice Commi s s ion and Sabah Forestry Department for their kind p e rm i s s i o n t o s t udy a t t h e U n i ve r s i t i P e r t a n i a n Malaysia .
Acknowl edgements are extended to the S tate Forestry Director o f Neger i Semb i l an f or kindly p roviding the research material s , and the Director General of Fore st Research I ns t i tute of Malaysia and Dean o f the Faculty o f Fore s t ry , Unive rs i t i Pertanian Ma l ay s i a f o r the i r permi s sion to u s e the facilities available . Cooperation f rom other staff members of these organisat ions i s al so greatly appreciated .
Heart iest grati tude i s al s o due t o my col l eague s , Mr . Herman Anj in , Mr . Eric Juin , Mr . Fedil i s Baj au , Mr . J o s eph Ahl an , Mr . Johnly Kul ik and others f or the ir constant support and encouragement s .
To my w i f e , chi ldren and re l a t ive s , grat i tude and thanks for the i r pa t i ence , support .
i i
I render my concern and
TABLE OF CON'rENTS
Page
ACKNOWLEDGMENTS i i
L I ST O F TABLES vi
L I ST OF FIGURES ix
ABSTRACT
ABSTRAK
CHAPTER
I
I I
xi i i
xvi
INTRODUCTION 1
Obj ect ives 6
L ITERATURE REVIEW 7
A Short N ote on Aca ci a mangi um 7
Importance of Acaci a mangi um 8
Growth and Yield 9
General Characterist ics and Properties of Wood . . . . . . . . . . . . . . 1 1
Wood Uti l isat ion for Compos ite Products . . . . . . . . . . . . . . . 16
Maj or Chemical Const ituent s of Wood 17
Cel lulose 18
Hemicel lul oses 2 0
L ignin 21
Extraneous Constituent s 22
Chemical Modif icat i on of Wood 23
Proofs of Bonding of Chemical to Wood Polymers . . . . ............ 27
iii
I I I
Page
Dist ribution of Bonded Chemi cal s . . 29
Propert ies of Chemi cally Modif ied Wood Product . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Water Adsorpt ion 30
Dimens ional Stabil i ty 33
Mechani cal Properties 3 7
Biological Resi stance 42
Other Related Properties 45
Potent ial of Chemical Modification of Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7
RAW MATERIAL PREPARATION AND CHEMI CAL CONSTITUENTS OF Acacia mangi um WOOD
Raw Material
S ource of Raw Material and
5 0
5 0
Bac}cground . . . . . . . . . . . . . . . . . . . . . . 5 0
Preparation o f Raw Material s 5 2
Maj or Chemical Const ituent s of Acacia mangi um Wood . . . . . . . . . . . . . . . . . . . 5 3
Preparation of Samples 53
Ethanol -Acetone Ext ractives Determination . . . . . . . . . . . . . . . . . . . 5 5
Holocellulose Determinat ion 55
Alpha cel lulose Determinat ion 5 6
Hemicel lulose Determination 5 7
Lignin Determination 5 7
Ash Determination 5 8
Data Analys i s 5 8
Resul ts and Discussion 5 8
lV
IV
V
VI
ACETYLATION CHARACTERISTICS OF Acacia mangi um WOOD FIBRES . . . . . . . . . . . .
Pil ot Study
Material s and Methods
Resul t s and Discus s i ons
Bulk Acetylat ion
Materials and Methods
Resul t s and Di scus sion
Evidences of Chemical Bonding
Colour
Infrared Data
Water Adsorption Theoret i cal
Page
61
61
62
71
9 2
9 2
95
96
96
9 9
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 3
MANUFACTURING AND PERFORMANCES OF MEDIUM DENS I TY F IBREBOARD . . . . . . . . . . . . . 113
Manufacturing of Board 113
Material s and Methods 114
Resul t s and Discussion 1 1 6
Performances of Board 1 1 7
Materials and Methods 11 7
Results and Di scus s i on 1 3 0
CONCLUS IONS AND RECOMMENDATIONS . . . . . . . . 184
Conclus ions 184
Recommendations . . . . . . . . . . . . . . . . . . 1 8 7
REFERENCES 1 9 0
VITA 2 10
v
LIST OF TABLES
Table
1. Dbh, Height and Mean Annual Increment s (MAl) of Dbh and Height Value s f or Acacia mangium
Page
of Dif f erent Ages . . . . . .... . . . . . . . . . . . . . . . . . 10
2. Major Chemical Constituent s (%) of Acacia mangium Wood .. . . ... . . . ............. 5 9
3. Re lationship of Extracted Materia l s t o Chemical Weight Gain in the Acetyl ation of Acacia mangium Wood Fibre s . . . . . . . . . . . . . . . . 75
4 . Weight Gain ( %) o f Acacia mangium Wood Fibre s Acetyl ated at 9 0 ° C and 1 20 °C . . . . . . . . . . . . . . 8 0
5 . Weight Gain ( % ) o f Acacia mangium Wood Fibre s Acetyl ated f or 6 hours with Various Concerntrations of Acetic Anhydride and Dif f erent Catalyst . . . . . . . . ... . . . . . . . . . . . . . 83
6 . Weight Gain ( % ) o f Acacia mangium Wood Fibre s with Dif ferent Initial Moisture Cont ent Acetyl at ed at 1 20 ° C Unc atalys ed and Cat al ys ed with Pyridine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7
7. Weight Gain Percentage in Bul k Acetylation o f Acacia mangium Wood Fibre s . . . . . . . . . . . . . ... 9 5
8 . Rel ative Humiditie s Over Saturated Salt S olution at 2 0 °C . . . . . . . . . . . . . . . . . . . . . . . . . . 1 04
9. Observed (Upper) and Cal cu la ted Values ( Lower) of Equil ibrium Moisture Content ( % ) of Unacetyl a t ed and Acetyl ated Acacia mangium Wood Fibre s at Various Rel ative Humiditie s 10 8
10 . Regression Coe f f icient s , Correl ation Coef ficient , Hailwood-Horrobin Equation Parameters , Hydrated and Dis solved Wat er and Fibre Saturation Point (% ) o f Unacetyl ated and Acetyl ated Acacia mangium " Wood Fibre s 10 9
1 1. Equil ibrium Mois ture Content ( % ) o f Acacia mangium MDF at Variou s Rel ative Humidities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
vi
Table
12. Equ i l i brium Moisture Content ( % ) of Acacia mangium MOF (Recond i t i oned ) Af t er
Page
Exposure t o Vari ous Tests . . . . . . . . . . .. . . . . . 136
13. Thickne s s Swe l l ing of Acacia mangium MOF Af t er 2 - hour Boi l ed in Water . . . . . . . . . . . . . . 143
14 . Thi ckness Swel l ing ( % ) of Aca cia mangium MOF Af t er 9 Cycles of Water Soak- dry Cycl i cal Trial s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
15 . Revers i bl e Thi ckness Swel l ing (% ) of Aca cia mangium MDF Af t er Cycl i cal Wat er S oaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
16. Modulus of Elast i c i ty (MPa) of Acacia mangium MOF Af t er Exposure to Various Types o f Treatment Condi t i ons . . . . . . . . . . . . . . . . . . . . . . 1 6 0
17 . Modulus o f Rupture (MPa) o f Unaged Acacia mangium MOF and Af ter Exposure t o Vari ous Type of Treatments . . . . . . . . . . . . . . . . 16 6
lB. Internal Bond Strength ( MPa ) o f Un aged and Aft er 2 - hour Boi led Acacia mangium MDF . . . . . 17 0
19 . Weight Los s ( % ) o f Aca cia mangium MOF After Exposure t o Pycnoporus sanguineus Fungal At tack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4
2 0 . Weight Los s (%) o f Aca cia mangium MDF After Exposure t o Coptotermes curvignathus Termit e s Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8
2 1 . Relationship o f Mortal i ty Rat e o f Coptotermes curvignathus with Type of Feed .. 180
vi i
LIST OF FIGURES
Figure
1 . Map of Peninsular Malaysia Showing the
Page
Locat i on of Source of Raw Material . . . . . . . . 51
2 . Sample Preparat i on for Chemi cal Const i tuent s Determination and Board Manufacturing . . . . . . 54
3 . Pilot Acetylat i on of Acacia mangi um Fibres 64
4 . Reaction Rate of Acacia mangi um Fibres Reacted with Acetic Anhydride at 1 2 0 ° C 73
5 . Reaction Rate of Acacia mangium Fibres Reacted with Acetic Anhydride and Catalysed with Pyridine at 12 0 ° C . . . . . . . . . . . 74
6 . Component s of Acetylated Wood of Acacia mangi um with and without Extract ives Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6
7 . Weight Gain Percentage of Acacia mangium Wood Fibres Acetyl ated at 9 0 ° C and 12 0 ° C 79
8 . Weight Gain Percentage of Aca ci a mangi um Wood Fibres Acetylated with Various Concentrat ions of Acetic Anhydride and Di f ferent Catalyst . . 8 2
9 . Weight Gain Percentage of Acacia mangium Wood Fibres with Dif ferent Init ial Moi s ture Content Acetylated at 1 2 0 ° C Uncatalysed 8 8
1 0 . Weight Gain Percentage of Acacia mangi um Wood Fibres with Dif ferent Init ial Moi sture Content Acetylated at 12 0 ° C with Pyrid ine 89
11. Bulk Acetylation of Acacia mangi um Wood Fibres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4
12 . Colour v ariat ion of Acaci a mangi um Wood Fibres Acetylated to Variou s Level s of Weight Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8
1 3 . An I l lustration of Potassium Bromide Disc Preparat i on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 0
14 . Infrared Spectra of Unacetylated and Acetylated Acacia mangium Wood Fibres 1 0 2
ix
Figure
15. The Calcul ated Curves of the Ratio HIM Against Relat ive Humidity f or Acacia mangium Wood Fibres Ace tylated at Various Leve ls o f
Page
We ight Gain . . . . . . .. . . . . . . ........ . .... . . . . . 110
16. The Cal cul ated Curves f or Hydrated Water ( Mh) and Dissolved Wat er (Ms) of Acacia mangium Wood Fibres with Various We ight Gain Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III
17. An I l lustrati on of the Apparatus Used i n the Decay Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4
18 . Equil ibrium Moi s ture Content ( % ) of Acacia mangium MDF at Vari ous Leve l s of Relative Humidity ................. . . . . .. . . . 132
19. Percentage Reduction o f Equil ibrium Moisture Content of Acacia mangium MDF Due to Acetylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
20. Compari s on o f Equil ibrium Moi sture Content o f Acacia mangium MDF and Fibres at Various Leve l s o f Relative Humidity . . . . . . . . .. . .. . . 134
2 1 . Equil ibrium Moisture Content of Acacia mangium MDF (Recond itioned) After Exposure to Various Type o f Treatment Condi ti ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
2 2 . Percentage I ncrease in Equ i l ibrium Moisture Content o f Acacia mangium MDF After Exposure to Various Types o f Te st (Based on EMC o f Unaged MDF ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
23. Thicknes s Swelling of Acacia mangium MDF After 2-hour Boiled in Wat er ... . . . . . . . . . . . 1 4 4
2 4 . Anti swe l l ing E f f ici ency of Acetylated Acacia mangium MDF of Various Weight Gain After 2-hour Boi l ed in Water .. .. . . . . . . . . . . 144
2 5 . Thickness Swell ing of Acacia mangium MDF After 9 Cycl es of Water Soak - dry Cycl i cal Trial s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
2 6. Revers ible Thicknes s Swell ing o f Acacia mangium MD F After 9 Cycl es of Water S oak-dry Cycl ical Trial s . . ... . . . . . . . . . . . . . 15 0
x
Figure
27 .
2 8 .
29 .
30.
31.
32.
33.
34.
35.
36.
37 .
38 .
Ant i swel l ing E f f iciency (% ) of Acetylated Acacia mangium MDF of Variou s Weight Ga ins Af ter 9 Cycles of Water S oak-dry Cycl ical Trial s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ant i swel l ing E f f iciency (% ) of Rever sible Thicknes s Swel l ing of Acetyl ated Acacia mangium MDF Af t er 9 Cycles of Water Soak -dry Cycl ical Tri a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Modulus o f Elast ici ty o f Unaged Acacia mangi um MDF . . . . . . . . . . . . . . . . . . . . . . . .
Percent age changes o f Modulus of Elas t icity of Acacia mangium MDF Due to Acetylat ion
Percent age Retent ion of Modulus o f Elas t icity of Acacia mangium MDF After 9 Cycles of Water S oak-dry Cycl ical Tri a l s . . . . . . . . . . . . . . . . . .
Final Modulus of E lasticity of Acacia mangium MDF Af ter Exposure t o Variou s Treatment Condit i ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percent age Retent ion of Modulus of Elasticity of Acacia mangium MDF Af ter Exposure to Various Type of Treatments . . . . . . . . . . . . . . . . .
Modulus of Rupture of Unaged Acacia mangium MDF
Percentge changes of Modulus of Rupture of Acacia mangium MDF Due to Acetyl at ion . . . . . .
Modulus of Rupture of Unaged Acacia mangium MDF and Af ter Exposure to Various Type of Treatment Conditions . . . . . . . . . . . . . . . . . . . . . .
Percentage Retention of Modulus of Rupture of Acacia mangium MDF Af ter Exposure to Various Treatments Conditions . . . . . . . . . . . . . . . . . . . . .
Internal Bond St rength o f Unaged and Af ter 2-hour Boi led Acacia mangium MDF . . . . . . . . . . .
xi
Page
1 5 1
1 52
157
1 5 7
1 5 9
1 6 1
1 62
1 6 4
1 6 4
1 6 7
1 6 8
1 7 1
Figure
39. Percentage changes of Internal Bond S trength
Page
of Acaci a mangi um MDF Due t o Acetylat ion 1 72
40. Weight Loss of Acaci a mangi um MDF Af ter Exposure t o Pycnoporus sanguineus ... . . . . . . . 175
41. Percentage Reduct ion of Weight Loss of Acacia mangi um MDF After Exposure to Pycnoporus sanguineus Due to Acetyl at ion . . . . . . . . . ... . .. . . . . . . . . .. . . . . . . . 175
42. Weight Los s of Acacia mangi um MDF After Exposure to Coptotermes curvigna tus . . . . .. . . . 179
43. Percentage changes of Weight Los s of Acaci a mangi um MDF Af ter Exposure to Coptotermes curvigna tus Due to Acetyl at ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9
xii
Abs tract of di s sertati on submitted to the Senate of Un i ve rs i t i P ertan i an M a l ays i a i n fu l f i l me nt of the requirements for the degree of Doctor of Phi l os ophy.
ACETYLATION OF Acacia mangium WOOD FIBRES AND ITS APPLICATION IN THE MEDIUM DENSITY FIBREBOARD.
By
SINING UNCHI
JUNE 1 9 9 6
Chairman As s ociate Prof . Mohd. Zin Jusoh
Faculty Forestry
The effective uti l i sati on of l ow qu a l i ty wood of
Acacia mangium W i l l d . wou l d be for the production of
m e d i um d e n s i t y f i br e b o a rd (MD F ) . H o w e v e r , MD F i s
susceptabl e to biodegradation and dimensional l y unstabl e
when i n contact with water , whi ch i s also a s s oci ated
with the deteri orati on of the mechanical and physical
properties of the board . Nonethe l ess, research on wood
h a s s ho w n t h a t i t i s p o ss i b l e t o e l i m i n a t e t h e
b i o d e gradat i on and d imensi onal i n s tabi l i ty through
chemical modification. Th i s stu dy w a s t h e r e f o r e
conducted w i th the a im o f evalua ting the acetyl ation
characteri stics of Aca cia mangium wood fibres and the
properti es and performances of the board produced.
pi l o t acety l ation was conducted to establ i s h the
optimum reaction conditions , which was subsequently used
as a guide in the bul k acetyl ation of the fibre s . Boards
xi i i
w e r e manu f a c t u r e d f r om b o t h t h e a c e t y l a t e d and
unacetyl ated f ibres and the propert ies and performances
of the boards were evaluated .
The pilot acetylation showed that the best reaction
conditions was on wood f ibres with 6 . 5 % ini t ial moistu re
content reacted at 1 2 0 ° C using pyridine as a catalyst .
The bu l k a c e t y l a t ion was su c c e s s f u l l y c ondu c t ed t o
a c h i eve t h e t a r ge t t e d we i gh t ga i n . N o p r obl em w a s
encountered in t he manufacturing o f board o f both the
unacetyl ated and acetyl ated f ibres .
The evaluation on the propert ies and performances of
the boards showed that the equil ibrium moisture content
( EMC) of the b oard of ace tyl a t ed f ibres ( acetylated
b o a r d ) d e c r e a s e d . D i me n s i o n a l s t ab i l i t y o f t h e
acetyl a t ed boards were enhanc ed . Both reve r s ibl e and
i r r e v e r s i b l e t h i c k n e s s s w e l l i n g r e du c e d . T h e
ant i swe l l i ng e f f i c i en c i e s ( AS E ) o f the 9 . 1 % W G board
range s f rom 3 0 . 9 % to 3 6 . 8 %; f o r the 1 3�9 % WG board ,
5 1 . 6 % t o 5 7 . 6 %; and f or the 2 0 . 4 % WG board , 6 7 . 1 % t o
7 0 . 1 % . The values of both the modulus o f e l a s t i c i ty
( MOE ) and the modulus of rupture ( MaR ) of the acetyl ated
boards have sl ightly reduced . However , af ter aged test ,
the values of MOE and MOR of the acetylated boards were
xiv
higher than that of the unacetylated board . The internal
b on d ( I B ) s t r e n g t h o f t h e a c e t y l a t e d b o a r d s w a s
s l i gh t l y enhan c e d . Af t e r b e ing b o i l ed , only t he I B
s t r e n g t h o f t h e u n a c e t y l a t e d b o a r d r e du c e d
sign i f icantly . The acetylated b oards were considerably
res i s t ant to Pycnoporus sanguineus fungal attack , but
not much t o the Coptotermes curvi gna thus termite attack .
Comparat ively , t he 1 3 .9 % WG board s howed the be s t
performance .
Fu r t he r s t u d i e s s u c h a s o n t he re s i s t an c e o f
acetylated boards against other species o f wood decaying
fungi and t e rmi t e s would be neces s ary t o add t o the
cost ef fectivenes s of this proces s .
xv
Abs t rak d i ss e rt a s i yang d ikemukakan kepad a S enat Universiti Pertanian Mal aysia s ebagai memenuhi syarat keperluan untuk Ijazah Doktor Fal safah .
Pengerusi
Fakul t i
ASETILASI GENTIAN KAYO Acacia mangium DAN PENGGUNAANNYA DALAM
PAPAN GENTIAN BERKETUMPATAN SEDERHANA.
Oleh
S INING UNCHl
JUN 1 9 9 6
Prof . Madya Mohd . Z in Jusoh
Perhutanan
Penggunaan berkesan bagi kayu berkual i t i rendah
Acaci a mangi um Willd . adal ah mel alui penghas i l an papan
gentian berketumpatan sed erhana (MDF) . Bagaimana pun MDF
ad alah rentan terhad ap biod egradasi d an berd imens i t id ak
s t a b i l apab i l a t e rk e n a a i r , d i m a n a i a nya Juga
mengakibatkan kemerosotan s i fat mekanikal dan f i z ikal
papan . Namun d emikian , penyel id ikan terhad ap kayu telah
menunjukkan bahawa b i od egrad a s i d an ke t id ak s t ab i l an
dimensi boleh d i tingk atk an melalui pengubahsuaian k im ia .
Oleh y ang demikian , kaj ian ini d il akukan d engan tujuan
untuk m enilai c i ri aset ilasi gentian kayu Acaci a mangi um
dan sifat - sifat serta prestasi papan yang dihasilkan .
Aset ilasi panduan telah di lakukan untuk mewujudkan
kead aan tindakbalas yang opt imum , yang boleh d igunakan
xvi
s ebagai panduan dalam ase t ilas i pukal gen t i an. Papan
papan t elah d i sediakan dar i kedua-dua gent i an , i a i t u
yang t elah d i ase t i lkan d a n yang t i d ak d i ase t i lkan .
Sifat - sifat serta prestasi pap an telah dikaji .
Ase t i lasi panduan menunjukkan bahawa t indak balas
yang terbaik adalah dengan menggunakan gent i an kayu yang
mengandungi kelembapan awal 6 . 5 % untuk dit i ndakbalaskan
pada 120 °C dengan menggunakan pyridina sebagai mangkin.
Ase t ilasi pukal t elah berjaya di lakukan unt uk mencapai
p e role han b e ra t sasaran . P e mb ua t an p a p an dar i pada
g e n t i a n y a n g t e la h d i a s e t i lk a n d a n y a n g t i d ak
diaset ilkan dapat d i sediakan dengan mudah .
Penilaian t erhadap sifat - si fat dan prestasi papan
menunjukkan bahawa kandungan kelembapan seimbang ( EMC )
untuk papan yang disediakan daripada gentian yang telah
d i ase t i lkan ( p apan d i ase t i lkan ) te lah b erkurangan.
K e s t a b i lan d ime n s i bag i p ap a n - p apan d i a s e t i lkan
b e rtambah b aik . K e dua - d ua p e n g e mbangan t e bal yang
berbalik dan t idak berbalik berkurangan . Keberkesanan
ant i pengembangan bagi papan dengan perolehan berat 9 . 1%
b e r julat d ari 30 . 9 % k e 3 6 . 8 % ; bag i p ap a n d e n g a n
perolehan berat 13. 9 % , 5 1 . 6 % ke 57 . 6 % ; dan bag i papan
dengan p erolehan berat 20 . 4 % , 6 7 . 1% ke 7 0 . 1 % . N i lai
kedua- dua modulus kenyalan dan modulus pat ahan bagi
xvi i
papan-papan d i aset i l kan berkurangan sed i k i t . Setel ah
m e l a l u i uj i an p enu a an, n i l a i modul u s k e ny a l an dan
modu lus patahan bagi papan d i aseti l kan a da l ah l eb ih
tinggi be rband i n g d engan p a p a n t i d a k d i a s e t i l k an.
Kekuatan i katan dal aman bagi p apan d i aseti l kan te l ah
bertambah ba i k. Sete l ah direbus , hanya kekuatan ikatan
dal aman bagi papan tidak diasetil kan berkurangan dengan
be rma kna. P a p an-p apan d i as e t i l k a n b o l eh d i anggap
se ba g a i t a h a n t e rh a d a p sera ng a n ku l a t Pycn oporus
sanguineus, tetapi kurang tahan terhadap serangan ana i
ana i Coptotermes curvignathus. Secara bandingan, papan
dengan perol ehan berat 13 . 9 % tel ah menunjukkan prestrasi
yang terbaik .
Kajian-kaj i an l anjut sep e rti k e r i ntangan p apan
di asetil kan terhadap spesis kulat pereput kayu dan anai
a n a i y a n g l a i n p e r l u d i l a k u k a n b a g i m e n a m b a h
keberkesanan kos proses ini .
xvi i i
CHAPTER I
INTRODUCTION
The succe s s ful introduction of Acacia mangium into
Sabah , Malay sia f rom Au stralia in 19 6 6 , p romotes this
s pecie s to a maj or fas t-g rowing tree in fore s t
p la n t a t i o n p r og r a m m e s i n A s i a a n d t h e Pa ci f i c.
Currently , over 1 5 0 , 0 0 0 hectares of Acacia mangium have
b e e n p l a n t e d w o r l d w ide , and t h e a r e a cov e r e d i s
expanding rapidly ( Kamis and Taylor , 1993 ) .
However , early indication showed that due to its
inherent characteristics as a f ast g rowing tree , which
p r oduced wood o f in f e r ior quality has led to s om e
p rob le m s i n s o l i d wood u t i l i z ation . I t h a s b e e n
envisaged that e f fective utilization o f this species may
therefore lies in the production of composite wood
p roducts , particularly the Mediu m Den sity Fib reboard
(MDF) .
MDF was first commercially manu f actu red in the
United States in 1960s (Maloney , 1991) . I n 197 7 , MDF was
manufactured in Western Europe. Since its introduction ,
1
2
MDF h a s gained a f a st reputat i on a s a p a n e l produ ct
because o f its properties of being high i n i nternal bond
strength , good s crewholdi ng p ower , good machinab i l ity ,
a n d u n i f o rm i ty i n s tru c ture . The s e p r o p e rt i e s are
s i m i l a r to t h o s e o f s o l i d w o o d . C o mp a r e d w i t h
parti cl eboard , MDF shows excepti onal surf ace and form
stab i l ity ( Suchsland , 1 973) . The se properti e s a l s o make
MDF suitable f or furniture manufacturing .
MDF by de f inition i s a compos ite material which
c ons i sts o f dry wood f ibres bonded together i nto a sol id
panel w i th a re s i n b i nder under c ontro l l ed hea t and
pre s sure ( Ma l oney , 1 9 9 1 ) . As such , it i s sus c eptab l e to
b i o l ogi c a l degradati on and dimensi onally unstabl e when
in conta ct with water .
W o o d f i b r e s w h i c h c omp o s e d o f l i g n i n a n d
c a rb o hy d r a t e s a r e b i o l o g i c a l l y d e g r a d e d b e c a u s e
organi sms re cogn i z e these pol ymers and pos s e s s speci f i c
enzyme systems capable o f hyd ro l yz i n g t h e m i n to
digestab l e uni t s ( Rowe l l , 1 9 83) . Of the se polymers , the
hemi c e l l u l o s e s are probab ly the f i rst to b e atta cked
because they are the most acc e s s ibl e . The a c c e s s ib l e
port i on o f c e l lu l o s e i s atta cked next . Be c au s e the
hi gh -mol e cular-weight cel lulose i s primari ly respons ible
f or the s trength in w oo d , its b i o l og i c a l degradat i on
through oxidation , hydrolysis , and dehydrati on reactions
causes wood to l os e strength . Attack by brown- rot fungi,
3
f o r e x amp l e , g r e a t l y r e du c e s t h e d e g r e e o f
polymerization in the holocel lul ose f raction , even when
accompanied by very low wood weight l os s ( Rowell et al.,
1 9 8 8 ) .
S i mi l a r t o s o l i d wood , MDF i s hyg r o s c op i c i n
n a t u r e . I t s h r i nk s a n d s w e l l s i n r e s p o n s e t o
changing rel at ive humidi t i e s in the surrounding a i r .
Wood f i bre s change dimens i on becau s e t h e c e l l wa l l
polymers contain hydroxyl and oxygen- cont a ining groups
that attract moi s ture through hydrogen bonding . C ompared
to sol id wood , swell ing in MDF is compounded through the
o c currence o f reve r s ib l e and i rreve r s i b l e swe l l i ng
c au s ed by the release o f res idual c ompre s s ive s t r e s s
imparted t o the board during the pre s sing process . I t i s
general ly accepted that thicknes s swell ing in composite
wood product is a s s o c i a t ed with det e r i ora t i on o f t he
me c h a n i c al and p hy s i c a l p r op e r t i e s o f t h e b o a r d
( Suchsland and Woodson , 1 9 9 1 j Vital e t al . , 1 9 8 0 ) .
D e ve l opme n t o f M D F w i t h g r e a t e r d i me n s i on a l
stab i l i ty , improved physical and mechani cal properties
and enhanced b iodegradabil ity would be neces sary . Such
development would divers i fy its end uses , apart f rom the
ma i n s t ream interior furni ture mak ing and would al s o
widen the overall s i z e o f i t s market .
4
Earl i e r report sugge s t ed that i t i s p o s s ibl e t o
reduce the rate of bi odegradat i on and the dimens i onal
instabil ity through chemi cal modificat ion of individual
ce l l - wa l l polymer componen t s ( Youngqu i s t and Rowe l l ,
1 9 8 8 ) . Rowel l ( 1 9 8 3 ) def ines chemi cal modi f i cat ion as
any chemi cal reaction between s ome reactive part of a
wood cell wal l component and a s ingl e chemi cal reagent ,
w i t h o r w i t h ou t a c a t a l y s t , t h a t r e s u l t s i n t h e
f ormat i on of a coval ent bond be tween the componen t s .
The mo s t abundant react ive chemi cal s i t e s in wood
are t he fun c t i onal hydroxyl group s of c e l l u l o s e ,
hemicelluloses , and l ignin . Most of the research done in
the area of chemical modi fi cat ion involves the react ion
between chemi cal reagents w i t h the s e hydroxyl groups
( Rowe l l , 1 9 7 5 ) . Howeve r , c e r t a i n prob l ems a r i s ed i n
treat ing bigger wood dimens ion because react ion can only
take place when the reagent i s in contact with the
react ive s i te . Furthermore , to initiate the reaction , it
i s neces sary t o apply heat . S i nc e wood is not a good
thermal conductor , the rat e and extent of the reaction
may be l imi ted by heat flow factor s . But , when wood i s
i n f ibre f orm , these cons t raint s are minimi sed because
the wood f ibre cell wal l i s cons iderably thin and thi s
f a c i l i t a t e s t h e p e n e t r a t i o n o f r e a g e n t g a i n i n g
acces s ibil ity to cell wall polymers . Simi larly , heat has
t o f l ow onl y the same di s t ance f rom a hot l iqu id or
vapour envi ronment in order for act ivat i on to occur .
Thu s , c h em i c a l mod i f i c a t i on t e c h n o l ogy h a s t h e
5
p o t e n t i a l t o b e appl i e d i n t h e p rodu c t i on of
biol ogically res i stant and dimensionally stabl e MDF .
Rowel l ( 1 9 8 3 ) stated that chemi cal reagent s u s ed
i n the mod i f i c a t i on of wood mu s t c ontain func t i onal
groups that can react with hydroxyl groups of the wood
c omp o n e n t s . R o w e l l ( 1 9 8 4 ) f u r t h e r r e v i e w e d many
different types of reagents that have been used to react
wi th many species of wood and non wood material s .
The chemical s used in these studies include anhydrides ,
epox ide s , i s ocyanat e s , l a c t one s , acetal s , and alkyl
chloride s . Catalyst s were al s o used whi ch among others
i n c l ud e z i n c c h l o r i d e , d ime t hy l f o rmami d e , s od i um
acetat e , urea ammonium sul fate and pyridine . However ,
pyridine and dimethyl formamide were not ed t o cause 2 0
to 2 5 % more swell ing to wood ( Ri s i and Arseneau , 1957 ;
Ashton , 1 9 7 3 ) . Thi s would further facilitate penetration
of reac t ing chemi cal s . Al though cons iderable research
has been condu c t ed on epoxides ( Rowe l l and E l l i s ,
1 9 84 ) and i socyanates ( Rowel l and E l l i s , 1 9 8 1 ) , the
mo s t e c onomi c a l l y promi s ing chemi cal modi f i c a t i on
technique at present i s acetylat ion of wood with acetic
anhydride (Rowel l , 19 8 2 ) . Thi s procedure only involves a
s ingle dip in acetic anhydride and requires no solvent s
or catalysts . The react ion t ime i s greatly shortened and
the recove ry of reusable and by - pr odu c t chemi cal s
s impl i f ied . Nonetheless , di f ferent wood species behaved
di f f erently to acetylat i on a s i ndica t ed by Imamura and
6
Ni shimot o, 1 9 87; R owe l l, 1 9 91; Hadi and Febrianto , 1 9 9 1 ;
Jal aluddin, 1 9 93 . Thi s s tudy i s theref ore condu c t ed to
produce chemi cal ly modi f ied medium dens i ty f ibreboard
with enhanced propert ies f rom pl anta t i on grown Aca cia
mangi um wood f ibres .
Objectives
The s p e c i f i c obj e c t ive s o f t h i s s t u dy a r e a s
follows:
1 . To determine the major chemical cons t ituents of
Acaci a mangi um wood .
2 . To determine the rate of acetylat ion of Acacia
mangi um wood f ibres with ace t i c anhydride .
3 . To fabricate Medium Density Fibreboard us ing
acetylated and untreated ( control ) Acacia mangi um
wood f ibres us ing phenol formaldehyde (PF ) re s i n as
binder .
4 . To investigate the dimensional stabil ity ,
physi cal , mechanical and biodegradation properties
of acetylated and untreated Acacia mangi um
Density Fibreboard .
Medium
CHAPTER II
LITERATURE REVIEW
A Short Note on Acacia mangium
Acacia mangium Willd. is a leguminous tree species
that belongs to the Leguminosae family, Mimosoidae
Sub-family. The genus Acacia includes about 1200 species
of trees and shrubs which occur in Africa, The Americas,
Asia, and Australia, with the majority of s pecies
found in Australia, Papua New Guinea, and Indonesia
(National Reseach Council, 1 9B 3) .
Acacia ma n g ium was introd u c ed into Sabah,
Malaysia in 1 9 6 6 (Tha m, 1 9 7 6) . This int rod u c t ion
consisted of a small quantity of seed collected from a
single tree standing beside a bridge over Lacey's Creek,
on the road between Mission Beach and EI Arish in
Qu e e n s l a nd, Au s tra l ia. The ini t i a l s e ed l ings w ere
planted as a firebreak around trial plots of pines in
Ulu Kukut in Jalan Madu and as trial plots in Gum -Gum
and Sibu ga in Sabah. The trees grew very well and
out-performed Eucalyptus deglupta and Gmelia arborea in
7