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