UNIVERSITI PUTRA MALAYSIA

OPTIMUM COMPRESSIVE PRESSURE AND THERMAL TREATMENT FOR EFFECTIVE MAHANG WOOD DENSIFICATION

WONG THYE SEANG

FH 2013 4

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OPTIMUM COMPRESSIVE PRESSURE AND THERMAL TREATMENT

FOR EFFECTIVE MAHANG WOOD DENSIFICATION

By

WONG THYE SEANG

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,

in Fulfillment of the Requirement for the Degree of Master of Science

May 2013

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment

of the requirement for the degree of Master of Science.

OPTIMUM COMPRESSIVE PRESSURE AND THERMAL TREATMENT

FOR EFFECTIVE MAHANG WOOD DENSIFICATION

By

WONG THYE SEANG

May 2013

Chair: Professor ParidahMd Tahir, PhD

Faculty: Forestry

Wood densification can be done by mechanical means involving heat and moisture.

However, mechanically densified wood is dimensionally unstable. Compressive

deformation could be fix by applying pressure above the elastic limit but lower than

the maximum compression load. Therefore, compressive pressure becomes an

important parameter and no stopper’s bars or molds are used to limit the

compression. Determination of the optimum compressive pressure for densification

provides a new innovative way in densifying wood without experiencing

compressive failure. Densified wood was successfully produced from ten-year-old

mahang wood (Macarangga gigantea) having initial density of 274±26 kg/m3.

Transverse compression strength in radial direction of steamed and unsteamed

mahang wood was determined prior to calculating the required compression

pressure. The steaming duration was 15, 30 and 45 min. After analysis using the

stress-strain curve, the compressive strength was converted into compressive

pressure. The After pre-steamed in a closed vessel at 130 °C for either 15, 30 or 45

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min, all the pre-steamed mahang woods were densified by compressing the wood at

a specific pressure that was pre-determined. After cooling and conditioning at dry

condition (under silica gel) for two weeks, the densified wood was tested for the

dimensional stability and strength properties. The wood was successfully

compressed at 75-78% compression ratio without any visual physical defects and

springback. Compressive pressures between 0.91 kgf/mm2 to 2.04 kgf/mm

2 were

using for compressing steamed mahang wood (15, 30 and 45 min steaming). The

densified mahang wood was tested for bending strength, shear modulus and

dimensional stability. The dimensional stability of densified mahang wood was

evaluated after conditioning at 45%, 65%, 85% and 100% RH at 25 °C. The

maximum thickness swelling was 43.49% after being conditioning in 100% RH at

25 °C until constant reading for 29 days. However, the thickness swelling was less

than 3% after conditioning at 45% and 65% RH. Therefore, all densified wood

specimens for bending strength and shear modulus were condition at 65% RH. The

results showed the bending strength of densified mahang was as high as 137.37

MPa, Modulus of Elasticity (MOE) was 16.80 GPa and shear modulus was 1.13

GPa. The result shows that the approach used in this study is effective for

densification of low density (<300 kg/m3) wood into about 300% of the original

density. Although the thickness recovery is still high, higher compressive pressure

improved dimensional stability. Thirty minutes steaming pre-treatment at 130 °C

provides an optimum condition for densification of mahang wood producing

densified mahang of high strength and dimensional stability.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai

memenuhi keperluan untuk ijazah Master Sains

TEKANAN MAMPATAN OPTIMUM DAN RAWATAN TERMA UNTUK

PENUMPATAN KAYU MAHANG YANG BERKESAN

Oleh

WONG THYE SEANG

Mei 2013

Pengerusi: Professor Paridah Md Tahir, PhD

Fakulti: Perhutanan

Penumpatan kayu dapat dihasilkan secara mekanikal dengan kehadiran haba dan

kelembapan. Walaubagaimanapun, kayu mampatan yang terhasil adalah tidak stabil

dari segi dimensinya. Untuk mencegah pengubahan bentuk dalam kayu, tekanan

mampatan semasa dimampat perlu dikenakan dengan syarat melebihi had elastic

kayu tetapi lebih rendah daripada daya mampatan maksima kayu tersebut. Oleh itu,

tekanan mampatan menjadi satu parameter yang penting dalam proses pemampatan

dimana tiada acuan dan ‘stopper’s bars’ digunakan dalam proses pemampatan.

Penentuan tekanan mampatan optimum terhadap proses pemampatan ini telah

memberi satu cara inovatif yang baru dalam menghasilkan kayu mampatan tanpa

masalah atau pengubahan bentuk semasa proses pemampatan, Dalam kajian ini,

kayu mampatan telah berjaya dihasilkan daripada kayu mahang (Maccarangga

gigantea) yang berumur sepuluh tahun ke atas dengan densiti 274±26 kg/m3.

Specimen kayu mahang yang telah kukus dan tanpa kukus telah ditentukan kekuatan

mampatan melintang pada arah radial sebelum proses pemampatan untuk mengira

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tekanan yang diperlukan untuk memampatkan spesimen kayu mahang. Jangka masa

untuk pengukusan spesimen ialah 15, 30 dan 45 minit. Selepas mengaplikasikan

teori lengkung tegasan-terikan untuk analisasi, kekuatan mampatan telah ditukar

kepada tekanan mampatan. Semua specimen kayu mahang yang telah dikukus di

bawah suhu 130 ºC selang janka masa 15, 30 atau 45 minit telah dimampat dengan

tekanan yang spesifik yang telah ditentukan. Selepas itu, spesimen kayu mampatan

yang telah dihasilkan dibiar sejuk dan dimasukkan ke dalam bekas tertutup yang

mengandungi gel silika selama dua minggu untuk tujuan kondisi sebelum ujian

kestabilan dimensi dan kekuatan fizikal. Hasil kajian menunjukkan spesimen kayu

berjaya dimampat di bawah nisbah mampatan75-78% tanpa kecacatan dan

pembidasan di bawah pemerhatian mata kasar. Tekanan mampatan di antara 0.91

kgf/m2 hingga 2.04 kgf/m

2 telah digunakan untuk memampatkan kayu mahang yang

dikukus (dengan masa pengukusan 15, 30 dan 45 minit). Kayu mampatan yang

dihasilkan telah diuji kekuatan tegasan, modulus ricihan dan kestabilan dimensinya.

Kestabilan dimensi kayu mampatan telah dinilai selepas dikondisi pada RH 45%,

65%, 85% dan 100% pada suhu 25 ºC. Maksimum ketebalan bengkak ialah 43.49%

selepas spesimen dikondisi pada RH 100% pada suhu 25 ºC dan mencapai bacaan

konstan dalam 29 hari. Walaubagaimanapun, ketebalan bengkak adalah kurang

daripada 3% selepas spesimen dikondisi pada RH 45% dan 65%. Sehubungan

dengan itu, semua spesimen kayu mampatan yang digunakan dalam ujian kekuatan

tegangan dan modulus ricihan adalah spesimen yang dikondisi pada RH 65%. Hasil

kajian menunjukkan bahawa kayu mampatan yang dihasilkan mencapai kekuatan

tegangan setinggi 137.37 MPa manakala modulus elastisiti (MOE) ialah 16.80 GPa

danmodulus ricihan ialah 1.13 GPa. Ini telah menunjukkan bahawa pendekatan yang

diaplikasi dalam kajian ini adalah efektif untuk memampatkan kayu yang

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mempunyai densiti rendah (<300 kg/m3) kepada densiti yang lebih tinggi sebanyak

300% daripada densiti asalnya. Walaupun pemulihan ketebalan selepas proses

pemampatan masih tinggi, tetapi tekanan mampatan yang tinggi telah menambah

baik kestabilan dimensi. Pra-rawatan pengukusan selama 30 minit pada suhu 130 ºC

adalah kondisi yang optimum untuk menghasilkan kayu mampatan dari kayu

mahang dengan kekuatan dan kestabilan dimensi yang lebih tinggi.

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ACKNOWLEDGEMENTS

During this period, I received guidance, assistance and encouragement from my

families, friends, supervisory committee and staff of Faculty of Forestry and

Institute of Tropical Forestry and Forest Products (INTROP). I would like to express

my gratitude to all those who gave me the possibility to complete this thesis. The list

of all contributors is much too long to be included here. However, I wish to

acknowledge several people. I would want to thank Prof. Dr. Paridah Md Tahir,

Assoc. Prof. Dr. Edi Suhaimi Bakar and Prof. Dr. Azmi Ibrahim for their tireless

supervision and encouragement. I also would like to express my sincere appreciation

to my wife Ng Sim Hong for her never-ending support, encouragement and patience

throughout my study period. Lastly I would like to dedicate my deepest gratitude to

all my family members for their support and encouragement and thank you Su God

for all the arrangement, blessing and guidance.

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfilment of the requirement for the degree of Master of Science. The

members of the Supervisory Committee were as follows:

Paridah Md. Tahir, PhD

Proffesor

Faculty of Forestry

Universiti Putra Malaysia

(Chairman)

Edi Suhaimi Bakar, PhD

Associate Professor

Faculty of Forestry

Universiti Putra Malaysia

(Member)

Azmi Ibrahim, PhD

Professor

Faculty of Civil Engineering

Universiti Teknologi MARA

(Member)

BUJANG BIN KIM HUAT, PhD

Professor and Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

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DECLARATION

I declare that the thesis is my original work except for quotations and citations

which have been duly acknowledged. I also declare that it has not been previously,

and is not concurrently, submitted for any other degree at Universiti Putra Malaysia

or at any other institution.

____________________

WONG THYE SEANG

Date: 21 May 2013

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TABLE OF CONTENTS

Page

ABSTRACT ii

ABSTRAK iv

ACKNOWLEDGEMENT vii

APPROVAL viii

DECLARATION x

LIST OF TABLES xiii

LIST OF FIGURES xiv

CHAPTER

1. INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 3

1.3 Justification 4

1.4 Objectives 6

2. LITERATURE REVIEW 7

2.1 Low Density Wood 7

2.1.1 Macrostructure of Low Density Wood 8

2.1.2 Wood Density 10

2.1.3 Mechanical Properties 11

2.2 Methods of Wood Densification 14

2.2.1 Densification Using Chemicals 15

2.2.1.1 Impreg 15

2.2.1.2 Compreg 16

2.2.1.3 Impregnation Using Other Polymers 17

2.2.2 Mechanical Densification 18

2.2.2.1 Stable Untreated Compressed Wood (Staypak) 19

2.2.2.2 Steaming Treatments (Hydro-thermo-treatment) 20

2.2.2.2.1 Effects on Microstructure 20

2.2.2.2.2 Effects on Wood Stabilization 21

2.3 Summary of Study 23

3. DETERMINATION OF OPTIMUM COMPRESSIVE 24

PRESSURE AND THE EFFECTS OF STEAMING ON THE

COMPRESSIBILITY OF MAHANG

3.1 Introduction 24

3.2 Materials and Methods 26

3.2.1 Materials 26

3.2.2 Experimental Parameters 27

3.2.3 Methods 28

3.2.3.1 Preparation of Materials 28

3.2.3.2 Determination of Optimum Compressive 29

Pressures

3.2.3.3 Pre-steaming of Wood Species 31

3.2.3.4 Hot-pressing (Densification) 31

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3.2.3.5 Conditioning and Springback Measurement 32

3.2.3.6 Statistical Analysis 32

3.3 Result and Discussion 33

3.3.1 Effect of Pre-steaming on Wood Compression 33

3.3.2 Effect of Steaming and Calculated Compressive 37

Pressure on Compression Ratio

3.3.3 Effect of Steaming and Calculated Compressive 40

Pressure on Density

3.4 Conclusions 41

4. DIMENSIONAL STABILITY AND STRENGTH 43

PROPERTIES OF DENSIFIED MAHANG WOOD

4.1 Introduction 43

4.2 Materials and Methods 44

4.2.1 Materials 44

4.2.2 Determination of Dimensional Stability 45

4.2.2.1 Materials 45

4.2.2.2 Measurements 45

4.2.3 Determination of Strength Properties 46

4.2.3.1 Materials 46

4.2.3.2 Bending Strength 47

4.2.3.3 Modulus of Elasticity (MOE) 47

4.2.3.4 Shear Modulus 48

4.3 Results and Discussion 49

4.3.1 Dimensional Stability of DensifiedMahang 49

4.3.1.1 Water Absorption 49

4.3.1.2 Thickness Swelling 53

4.3.2 Strength Properties of DensifiedMahang 55

4.3.2.1 Bending Strength 55

4.3.2.2 Modulus of Elasticity (MOE) 58

4.3.2.3 Shear Modulus 60

4.4 Conclusions 63

5. CONCLUSIONS AND RECOMMENDATIONS 64

5.1 Conclusions 64

5.2 Recommendations 66

REFERENCES 67

APPENDICES 73

BIODATA OF STUDENT 79