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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