PREPARATION AND CHARACTERISATION OF HEAT-TREATED AND UNTREATED RED

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PREPARATION AND CHARACTERISATION OF HEAT-TREATED AND UNTREATED RED

BALAU/LDPE COMPOSITES

RUTH ANAYIMI LAFIA-ARAGA

FACULTY OF SCIENCE UNIVERSITY OF MALAYA

KUALA LUMPUR

2013

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PREPARATION AND CHARACTERISATION OF HEAT-TREATED AND UNTREATED RED

BALAU/LDPE COMPOSITES

RUTH ANAYIMI LAFIA-ARAGA

THESIS SUBMITTED IN FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE

OF DOCTOR OF PHILOSOPHY

DEPARTMENT OF CHEMISTRY FACULTY OF SCIENCE UNIVERSITY OF MALAYA

KUALA LUMPUR

2013

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UNIVERSITI MALAYA

ORIGINAL LITERARY WORK DECLARATION

Name of Candidate: RUTH ANAYIMI LAFIA-ARAGA (Passport/I.C. No: A02761088) Registration/Matric No: SHC090009

Name of Degree: Doctor of Philosophy

Title of Project Paper/Research Report/Dissertation/Thesis (“this Work”):

PREPARATION AND CHARACTERISATION OF HEAT-TREATED AND UNTREATED RED BALAU/LDPE COMPOSITES

Field of Study: POLYMER CHEMISTRY I do solemnly and sincerely declare that:

(1) I am the sole author/writer of this Work;

(2) This Work is original;

(3) Any use of any work in which copyright exists was done by way of fair dealing and for permitted purposes and any excerpt or extract from, or reference to or reproduction of any copyright work has been disclosed expressly and sufficiently and the title of the Work and its authorship have been acknowledged in this Work;

(4) I do not have any actual knowledge nor do I ought reasonably to know that the making of this work constitutes an infringement of any copyright work;

(5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya (“UM”), who henceforth shall be owner of the copyright in this Work and that any reproduction or use in any form or by any means whatsoever is prohibited without the written consent of UM having been first had and obtained;

(6) I am fully aware that if in the course of making this Work I have infringed any copyright whether intentionally or otherwise, I may be subject to legal action or any other action as may be determined by UM.

Candidate’s Signature Date

Subscribed and solemnly declared before,

Witness’s Signature Date

Name:

Designation:

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ABSTRAK

Serbuk kayu Balau Merah dirawat pada suhu 180°C dan 200°C selama satu jam dan diadun dengan polietilena berketumpatan rendah (LDPE) menggunakan pensemperit pada peratusan berat 9, 20 dan 37%, seterusnya digunakan untuk menghasilkan spesimen ujian dengan mesin acuan suntikan. Spesimen komposit yang didedahkan kepada persekitaran yang berbeza kemudiannya dilakukan pencirian terhadap sifat termal, mekanik dan mekanik dinamik. Analisis termogravimetri menunjukkan rawatan haba dapat memperbaiki sifat termal serbuk kayu dan komposit. Melalui ujian pengimbasan kalorimetri, serbuk kayu tidak menunjukkan berubahan ketara ke atas takat lebur komposit. Walau bagaimanapun, darjah penghabluran komposit yang mengandungi serbuk kayu yang tidak dirawat meningkat dengan peningkatan komposisi serbuk kayu, manakala komposit serbuk kayu yang dirawat, berlaku penurunan apabila komposisi serbuk kayu meningkat. Analisis mekanikal dinamik menunjukkan komposit daripada serbuk kayu dirawat mempamerkan modulus penyimpanan dan modulus kehilangan yang lebih tinggi berbanding dengan serbuk kayu yang tidak dirawat. Nilai tan delta juga didapati lebih rendah bagi komposit sebuk kayu yang dirawat berbanding yang tidak dirawat. Penambahan serbuk kayu dirawat menunjukkan peningkatan modulus tegangan LDPE tulen sebanyak 400% lebih tinggi berbanding serbuk kayu tidak dirawat (309%) kerana rawatan haba pada serbuk kayu dapat meningkatkan pembasahan antara permukaan serbuk kayu dan matriks, yang membawa kepada lekatan antara muka yang lebih baik. Di samping itu, komposit yang mengandungi serbuk kayu dirawat pada 180°C menunjukkan nilai kekuatan tegangan lebih tinggi berbanding serbuk kayu tidak dirawat dan serbuk kayu yang dirawat pada 200°C. Sifat lenturan juga didapati meningkat dengan penambahan serbuk kayu dirawat

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berbanding dengan komposit serbuk kayu yang dirawat. Beban puncak dan faktor intensti tekanan kritikal meningkat dengan peningkatan komposisi serbuk kayu dan suhu rawatan. Tenaga kegagalan dan kadar lepas tenaga kritikal menurun dengan peningkatan komposisi serbuk kayu. Namun begitu, nilai yang tertinggi diperoleh daripada komposit serbuk kayu dirawat pada 180°C.

Penambahan polietilena maleik anhidrida (MAPE) ke dalam komposit yang menggandungi polietilena membawa kepada peningkatan dalam sifat termal dan mekanikal pada tahap yang berbeza. Dalam komposit yang mengandungi serbuk kayu dirawat, penambahan 8% MAPE menghasilkan komposit dengan modulus dan kekuatan tegangan tertinggi manakala 6% MAPE mencatatkan modulus lenturan maksimum. Semua komposit menyerap lembapan pada tahap yang berbeza dan mengakibatkan kemerosotan sifat mekanikal. Komposit daripada serbuk kayu dirawat menunjukkan penyerapan air yang lebih rendah sehingga 90% dan tidak mempamerkan perubahan ketara atas sifat bahan.

MAPE tidak menunjukkan kesan perubahan ketara ke atas penyerapan air bagi komposit serbuk kayu yang dirawat. Terhadap kesan penanaman di dalam tanah, komposit daripada kayu dirawat menunjukkan pertumbuhan kulat yang kurang pada permukaan dan ketahanan yang lebih baik terhadap penguraian.

Sifat termal dan mekanikal merosot akibat pendedahan kepada persekitaran luar. Walau bagaimanapun, komposit daripada kayu dirawat menunjukkan ketahanan yang lebih kepada persekitaran luar. Kesimpulan dapat dibuat bahawa rawatan haba serbuk kayu meningkatkan keupayaan komposit untuk mengekalkan sifat-sifat mekanikal selepas pendedahan kepada persekitaran luar.

Secara umum, sifat-sifat komposit tidak terjejas akibat pendedahan kepada persekitaran tertutup. Oleh itu, menggunakan produk ini sesuai digunakan dalam aplikasi domestik.

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ABSTRACT

Red balau saw dust was heat-treated at 180°C and 200°C for one hour and compounded with low density polyethylene (LDPE) at 9, 20 and 37 wt%, then injection moulded. The composites specimens were exposed to different environments and characterised for the thermal, dynamic mechanical and mechanical properties. Thermogravimetric analysis revealed that heat treatment improved the thermal properties of the wood flour and its LDPE composites.

Differential scanning calorimetric study showed that wood had no significant effect on the melting behaviour of the composites. However, the degree of crystallinity of composites containing untreated wood flour increased with increasing wood content, while the composites made from heat-treated wood flour, a decreasing trend was observed as the wood content increased. Dynamic mechanical analysis revealed that composites made from heat-treated wood flour exhibited higher storage and loss modulii than that of untreated wood.

Lower tan delta values were observed in the heat-treated wood composites.

The tensile modulus of the heat-treated wood flour/LDPE composites increased by 400% while the untreated wood flour/LDPE composites increased by 309%

over the neat LDPE. This is because of the improved wetting of the heat-treated wood particles by the matrix, leading to a better interfacial adhesion.

In addition, composites containing wood flour treated at 180°C showed higher tensile strength values than those made from untreated and 200°C treated wood flour. Furthermore, the flexural properties were found to increase with filler loading in the untreated wood composites, relative to those containing heat- treated wood flour. Peak load and critical stress intensity factor increased with wood content and treatment temperature. While the energy to failure and the critical strain energy release rate decreased with wood content, the values are

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highest in composites made from wood flour treated at 180°C. Incorporation of maleic anhydride grafted polyethylene (MAPE) into the composites led to improvements in the thermal and mechanical properties to various extents. In the composites containing untreated wood flour, incorporation of 8% MAPE provided the highest tensile strength and modulus, while 6% MAPE content recorded the maximum flexural modulus. All composites absorbed moisture to various extents with different levels of mechanical property deterioration.

Composites made from heat-treated wood flour showed a reduction in water absorption up to 90% and offered better resistance to decline in properties.

Heat-treated wood composites showed negligible effect of MAPE on the water absorption. For soil burial, composites made from heat-treated wood flour showed less fungal growth on the surface and better resistance to properties deterioration. Thermal and mechanical properties deteriorated with outdoor exposure. However, composites made from heat-treated wood flour showed better resistance to the elements of the outdoor environment than their untreated counterparts. It can be concluded that heat treatment of wood flour enhances the properties of wood thermoplastic composites with complementary ability to retain their mechanical properties following exposure to harsh outdoor environment. In general, the properties of the composites are not adversely affected on exposure to indoor environment. Therefore, using this product for domestic applications will be worthwhile.

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ACKNOWLEDGEMENTS

I wish to express my profound gratitude to the Lord God Almighty, who made the completion of this research a reality. God has proved, once again, that with Him all things are possible.

I want to appreciate my supervisors, Prof. Dr. Aziz Bin Hassan and Prof. Dr. Rosiyah Binti Yahaya for their untiring patience in guiding this research. I am indebted to all my teachers/advisors that, in one way or the other, have impacted my life throughout my academic career. I must thank Prof Taihyun Chang of the Chemistry Department, Pohang University of Science and Technology, Pohang, South Korea, for arousing in me the interest in academic research. Special thanks to Dr Noel F. Thomas and Mr Sunday Albert Lawal for their invaluable suggestions.

Thanks to Mr Zulkifli Bin Abu Hasan who provided the technical/logistic support for this research. I am also grateful to all the members of the Polymer and Composite research group for the many ways they have contributed to the completion of this study.

I am thankful to the University of Malaya for funding this research from grant numbers PS347/2009C and RG150/11AFR. I also want to show my gratitude to the Federal Ministry of Education, Nigeria and the Federal University of Technology Minna, for supporting my studies with grant from the Education Tax Fund. Thanks to Heseh Woow Sdh. Bhd, Klang, Selangor and Maltimber Industries, Kuala Lumpur for supplying the wood sawdust used in this research.

I must appreciate my friends, far and near who have kept in touch all these years. Your calls, SMS, emails and facebook posts came when they were most needed. I especially thank the Trinity Methodist Church, Petaling Jaya, particularly the SS two home fellowship group and the Children Sunday School unit, for making my stay in Malaysia worthwhile. I am grateful to the Chapel of Grace, Federal University of Technology,

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Minna and the Words of Eternal Life Ministries, Minna, for supporting my family in many ways throughout my stay away from home.

I lack words to express my gratitude to my family and in-laws for being solidly behind me throughout this program. I like to thank my father, Mr Samuel A. Oyibo, who instilled in me the love for education and who sacrificed his material comfort to give me a good beginning. I appreciate all my siblings for the different roles they played in my life in the course of this program. I am eternally grateful to my husband, Mr Joseph Lafia Araga, who made enormous sacrifices to give me the peace of mind needed for doctoral studies. I must say thank you to my children, Rahima, Simpa, Adavize and Ohiani for bearing with my absence while away on this program. May God bless you all.

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LIST OF FIGURES

Page

Figure 2.1: Structure of cellulose………16

Figure 2.2: Structure of hemicellulose………17

Figure 2.3: Structure of lignin ………...…….18

Figure 2.4: The reaction of cellulose fibres with hot MAPP………..28

Figure 3.1: Tensile testing specimen and set up……….48

Figure 3.2: Set up of flexural testing………..49

Figure 3.3: Single edge notch impact specimen and set up………51

Figure 4.1: TGA/DTG thermograms of untreated and heat-treated wood flour………...53

Figure 4.2: FTIR spectra of treated and untreated red balau saw dust……….…55

Figure 4.3: SEM micrograph of wood flour………...………58

Figure 4.4: TGA/DTG thermograms of LDPE, untreated and heat-treated WTC at different filler loadings………..………62

Figure 4.5: TGA/DTG thermograms of LDPE and composites containing 20 wt% and 37 wt% untreated and heat-treated wood f lour……..………63

Figure 4.6: TGA/DTG thermograms of 20 wt% and 37 wt% untreated wood composites with different MAPE contents………..………...66

Figure 4.7: TGA/DTG curves of 37 wt% composites made from heat-treated wood flour with varying MAPE contents………..………67

Figure 4.8: DSC thermograms of LDPE and composites containing varying amounts of untreated and heat-treated wood flour………..……70

Figure 4.9: DSC thermograms of 37 wt% untreated wood composites with varying MAPE content………..…..72

Figure 4.10: Stress and strain in dynamic mechanical analysis……….76

Figure 4.11: Storage modulus of LDPE and composites as a function of wood content……….78

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Figure 4.12: Storage modulus of LDPE and 37 wt% composites as a function

of heat treatment and MAPE content………..82 Figure 4.13: Loss modulus curves as a function of temperature of neat LDPE and

composites containing untreated wood flour at different loadings……...83 Figure 4.14: Loss modulus curves of LDPE and 37 wt% composites as a

function of heat treatment and MAPE content………86 Figure 4.15: Variation of tan δ with temperature for LDPE and untreated wood

composites at different filler loadings……….88 Figure 4.16: Tan δ curves of LDPE and 37 wt% composites as a function

of heat treatment and MAPE content……….91 Figure 4.17: Tensile modulus of composites as a function of wood content and

heat treatment………..…...93 Figure 4.18: SEM micrograph of tensile fractured surface of pure LDPE…………....94 Figure 4.19: SEM micrograph of tensile fractured surface of composites

containing 37 wt% untreated wood……….94 Figure 4.20: SEM micrograph of tensile fractured surface of 37 wt% composite

made from wood flour treated at 180°C ……….……….96 Figure 4.21: Tensile modulus of 20 wt% and 37 wt% composites containing

untreated wood flour and different MAPE content………...………97 Figure 4.22: Schematic representation of the chemical coupling

mechanism in wood flour-LDPE-MAPE interface……….97 Figure 4.23: Tensile modulus of composites made from 37 wt% untreated

and heat-treated wood flour with varying amounts of MAPE…………...98 Figure 4.24: Tensile strength of composites as a function of wood

content and heat treatment……….101 Figure 4.25: Tensile strength of 20 wt% and 37 wt% untreated wood

composites as a function of MAPE content………..…………..102 Figure 4.26: Schematic representation of wetting in compatibilised

bio-composites………...………..102

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Figure 4.27: Tensile strength of composites made from 37 wt% untreated and

heat-treated wood flour with varying amounts of MAPE………103 Figure 4.28: Tensile strain of composites at a function of wood content

and heat treatment………104 Figure 4.29: Tensile strain of 20 wt% and 37 wt% composites made from

untreated wood as a function of MAPE content………..…105 Figure 4.30: Tensile strain of 37 wt% untreated and heat-treated wood

composites with varying amounts of MAPE………..106 Figure 4.31: Flexural modulus of composites as a function of wood flour

content and treatment temperature………..……….108 Figure 4.32: Flexural modulus of composites from untreated wood

as a function of MAPE content………..………...111 Figure 4.33: Flexural modulus of 37 wt% composites as a function of MAPE

content and treatment temperature………...111 Figure 4.34: Flexural strength of composites as a function of wood flour

content and treatment temperature………...112 Figure 4.35: Flexural strength of composites from untreated wood as a

function of MAPE content………113 Figure 4.36: Flexural strength of 37 wt% composites as a function of

MAPE content and heat treatment………..…………..113 Figure 4.37: Flexural displacement of composites as a function of wood flour

content and treatment temperature………115 Figure 4.38: Flexural displacement of composites from untreated wood

as a function of MAPE content………...116 Figure 4.39: Flexural displacement of 37 wt% composites as a function of

MAPE content and treatment temperature....…...117 Figure 4.40: Peak load as a function of notch dept for different wood

content and heat treatments………..………...122 Figure 4.41: Impact fractured surface of neat LDPE showing signs of ductility…...123

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Figure 4.42: Impact fractured surface of composites containing

37 wt% untreated and 200°C treated wood flour………124 Figure 4.43: Peak load of different a/D as a function of MAPE

content and heat treatment………..……….125 Figure 4.44: K_c of composites as a function of wood content and

treatment temperature………...127 Figure 4.45: Kc of 37 wt% composites as a function of MAPE content and

treatment temperature………...128 Figure 4.46: energy to failure of composites as a function of wood content and

treatment temperature for different a/D ratios………..130 Figure 4.47: W of composites as a function of MAPE content and heat treatment

for different a/D ratios………..……...133 Figure 4.48: Gc of composites as a function of wood content and

treatment temperature………..………133 Figure 4.49: Variation of G_c of 37 wt% composites with MAPE content and

treatment emperature………134 Figure 4.50: Moisture absorption of composites as a function of wood

content and treatment temperature………138 Figure 4.51: Water absorption of 37 wt% composites as a function of

MAPE content and heat treatment………..………...141 Figure 4.52: Variation of thickness swelling of neat LDPE and different filler

loadings of untreated and heat-treated composites with time………....149 Figure 4.53: Variation of thickness swelling of uncompatibilised and

compatibilised composites made from 37 wt% untreated and

heat-treated wood flour with time………..………149 Figure 4.54: TGA thermograms of dry as-moulded and wet composites

made from 37 wt% untreated and heat-treated wood flour………..151 Figure 4.55: DSC thermograms of 37 wt% dry as-moulded and moisture

saturated composites containing 0% and 6% MAPE………..155

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Figure 4.56: Storage modulus curves of LDPE and 37 wt% dry as-moulded

and moisture saturated composites containing 0% and 6% MAPE……161 Figure 4.57: Loss modulus curves of LDPE and 37 wt% dry as-moulded

and moisture saturated composites containing 0% and 6% MAPE…….162 Figure 4.58: Tan delta curves of dry as-moulded and moisture saturated

LDPE and 37 wt% composites containing 0% and 6% MAPE……...…163 Figure 4.59: Tensile modulus of wet and dry composites as a function of wood

content heat treatment………..168 Figure 4.60: Tensile modulus of 37 wt% wet and dry composites

containing 6% MAPE………168 Figure 4.61: Tensile strength of wet and dry as-moulded composites as a

function of wood content and heat treatment………169 Figure 4.62: Tensile strength of 37 wt% wet and dry as-moulded composites

containing % MAPE………169 Figure 4.63: Tensile strain of wet and dry composites as function of wood

content and heat treatment………..170 Figure 4.64: Tensile strain of 37 wt% wet and dry composites

containing 6% MAP……….170 Figure 4.65: Flexural modulus of wet and dry composites as a function of wood

content and heat treatment………...……….172 Figure 4.66: Flexural modulus of 37 wt% wet and dry composites

containing 6% MAPE………..………173 Figure 4.67: Flexural strength of wet and dry composites as a function of wood

content and heat treatment……….………..173 Figure 4.68: Flexural strength of 37 wt% wet and dry composites

containing 6% MAPE………...………174 Figure 4.69: Flexural displacement of wet and dry composites as a function

of wood content and heat treatment……….174 Figure 4.70: Flexural displacement of 37 wt% wet and dry composites

containing 6% MAPE……… ………175

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Figure 4.71: Peak load of dry as-moulded and wet samples as a function of wood content and heat treatment………...……….177 Figure 4.72: Peak load of 37 wt% dry as-moulded and wet samples

containing 6% MAPE………...178 Figure 4.73: K_c of dry as-moulded and wet samples as a function of wood

content and heat treatment………...178 Figure 4.74: Kc of 37 wt% dry as-moulded and wet samples

with 6% MAPE……….………179 Figure 4.75: Energy to failure of dry as-moulded and wet samples as a

function of wood content and heat treatment………180 Figure 4.76: Energy to failure of 37 wt% dry as-moulded and wet samples

with 6% MAPE………181 Figure 4.77: Gc of dry as-moulded and wet samples as a function of wood

content and heat treatment……….181 Figure 4.78: Impact fractured surface of 37 wt% 200°C treated wood flour………...182 Figure 4.79: Impact fractured surface of 37 wt% untreated wood flour………..182 Figure 4.80: Gc of 37 wt% dry as-moulded and wet samples with 6% MAPE………183 Figure 4.81: SEM micrograph of the moulded surface of buried neat LDPE

showing no fungal growth……….185 Figure 4.82: SEM micrograph of the surfaces of buried 37 wt% WTC

containing untreated and 200°C treated wood flour……….186 Figure 4.83: TG/DTG curves of dry as-moulded and buried LDPE and

37 wt% composites containing 0% and 6% MAPE………..……..189 Figure 4.84: DSC curves of dry as-moulded and buried LDPE and

composites containing 37 wt% untreated and heat-treated

wood flour containing 0% and 6% MAPE………..….……...192 Figure 4.85: Storage modulus curves of dry as-moulded and buried

37 wt% untreated and heat-treated composites containing

0% and 6% MAPE………...195

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Figure 4.86: Loss modulus of dry as-moulded and buried LDPE and

37 wt% composites with 0% and 6% MAPE………..……..197 Figure 4.87: Tan delta of dry as-moulded and buried LDPE and

37 wt% composites containing 0% and 6% MAPE……….199 Figure 4.88: Tensile modulus of dry as-moulded and buried composites

as a function of wood content and heat treatment……….204 Figure 4.89: Tensile modulus of 37 wt% buried and dry as-moulded

composites with 6% MAPE……….205 Figure 4.90: Tensile strength of dry as-moulded and buried composites

as a function of wood content and heat treatment………205 Figure 4.91: Tensile strength of 37 wt% buried and dry as-moulded

composites with 6% MAPE………..206 Figure 4.92: SEM micrograph of surface of buries 37 wt% untreated wood

composite containing 6% MAPE showing sparse fungal growth…..…206 Figure 4.93: Tensile strain of dry as-moulded and buried composites as a

function of wood content and heat treatment………..…207 Figure 4.94: Tensile strain of 37 wt% buried and dry as-moulded

composites with 6% MAPE………207 Figure 4.95: Flexural modulus of dry as-moulded and buried composites

as a function of wood content and heat treatment………..……….209 Figure 4.96: Flexural modulus of 37 wt% dry as-moulded and buried

composites with 6% MAPE……….210 Figure 4.97: Flexural strength of dry as-moulded and buried composites

as a function of wood content and heat treatment………..210 Figure 4.98: Flexural strength of 37 wt% dry as-moulded and buried

composites with 6% MAPE………...………..211 Figure 4.99: Flexural displacement of dry as-moulded and buried

composites as a function of wood content and heat treatment…..……...211 Figure 4.100: Flexural displacement of 37 wt% dry as-moulded and buried

composites with 6% MAPE………...………212

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Figure 4.101: Peak load of dry as-moulded and buried samples as a

function of wood content and heat treatment………..……...216 Figure 4.102: Peak load of 37 wt% dry as-moulded and buried samples

containing 6% MAPE……….216 Figure 4.103: K_c of dry as-moulded and buried samples as a function of

wood content and heat treatment………...217 Figure 4.104: Kc of 37 wt% dry as-moulded and buried samples

containing 6% MAPE……….217 Figure 4.105: energy to failure of dry as-moulded and buried samples

as a function of wood content and heat treatment…………..………..218 Figure 4.106: energy to failure of 37 wt% dry as-moulded and buried

composites with 6% MAPE………...………218 Figure 4.107: Gc of dry as-moulded and buried samples as a function of

wood content and heat treatment………219 Figure 4.108: G_c of 37 wt% dry as-moulded and buried samples with

6% MAPE………...………...219 Figure 4.109: FTIR of the surface of 37 wt% composites made from

untreated and heat-treated wood flour exposed to the

outdoor environment………...224 Figure 4.110: Visual appearance of dry as-moulded and outdoor weathered

untreated and 200°C treated composites………...……….225 Figure 4.111: SEM micrograph of the surfaces of unaged LDPE

and outdoor aged LDPE………..…………..227 Figure 4.112: SEM micrograph of the surfaces of unaged WTC, untreated

and 200°C treated WTC exposed to outdoor aging…………..……..229 Figure 4.113: TGA/DTG of outdoor aged and unaged LDPE and 37 wt%

untreated and heat-treated WTC containing 0% and 6% MAPE…...231 Figure 4.114: DSC thermograms of LDPE and 37 wt% untreated and heat

treated outdoor aged WTC containing 0% and 6% MAPE………235 Figure 4.115: Storage modulus curves of dry as-moulded and outdoor

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exposed LDPE and composites containing 37 wt% wood flour.

and 0% and 6% MAPE………...240 Figure 4.116: Loss modulus curves of dry as-moulded and outdoor

exposed LDPE and composites containing 37 wt% wood flour

with 0% MAPE and 6% MAPE………241 Figure 4.117: Tan delta curves of dry as-moulded and outdoor exposed

LDPE and composites containing 37 wt% wood flour and

0% and 6% MAPE………242 Figure 4.118: Tensile modulus of outdoor and dry as-moulded composites

as a function of wood content and treatment temperature………248 Figure 4.119: Tensile modulus of 37 wt% outdoor and dry as-moulded

composites with 6% MAPE………...248 Figure 4.120: Tensile strength of outdoor and dry as-moulded composites

as a function of wood content and treatment temperature…….…..….249 Figure 4.121: Tensile strength of 37 wt% outdoor and dry as-moulded

composites with 6% MAPE………..………249 Figure 4.122: Tensile strain of outdoor and dry as-moulded composites

as a function of wood content and treatment temperature………250 Figure 4.123: Tensile strain of 37 wt% outdoor and dry as-moulded

composites with 6% MAPE………..250 Figure 4.124: Flexural modulus of dry as-moulded and outdoor exposed samples

as a function of wood content and treatment temperature………252 Figure 4.125: Flexural modulus of 37 wt% dry as-moulded and outdoor

exposed samples with 6% MAPE………...253 Figure 4.126: Flexural strength of dry as-moulded and outdoor exposed

samples as a function of wood content and treatment temperature……253 Figure 4.127: Flexural strength of 37 wt% dry as-moulded and outdoor

exposed samples with 6% MAPE………..……...254 Figure 4.128: Flexural displacement of dry as-moulded and outdoor exposed

samples as a function of wood content and treatment temperature……254

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Figure 4.129: Flexural displacement of 37 wt% dry as-moulded and outdoor.

exposed samples with 6% MAPE………...…………...255 Figure 4.130: Peak load of dry as-moulded and outdoor exposed samples

as a function of wood content and heat treatment………...258 Figure 4.131: Peak load of 37 wt% dry as-moulded and outdoor exposed

samples containing 6% MAPE………..258 Figure 4.132: Kc of dry as-moulded and outdoor exposed samples as a function

of wood content and heat treatment temperature………..…259 Figure 4.133: K_c of 37 wt% dry as-moulded and outdoor exposed samples

containing 6% MAPE………..……….259 Figure 4.134: energy to failure of dry as-moulded and outdoor exposed

samples as a function of wood content and heat treatment…………...260 Figure 4.135: energy to failure of 37 wt% dry as-moulded and outdoor

exposed samples with 6% MAPE……….260 Figure 4.136: G_c of dry as-moulded and outdoor exposed samples as a

function of wood content and heat treatment…...……….261 Figure 4.137: Gc of 37 wt% dry as-moulded and outdoor exposed samples

containing 6% MAPE………...…………261 Figure 4.138: SEM micrograph of indoor exposed LDPE………...………262 Figure 4.139: SEM micrograph of surfaces of indoor exposed composites

containing untreated and 200°C treated wood flour…………..……...263 Figure 4.140: TGA/DTG curves of dry as-moulded and indoor

exposed LDPE and 37 wt% untreated and heat-treated WTC

containing 0% and 6% MAPE ………...…...265 Figure 4.141: DSC thermograms of dry as-moulded and indoor exposed

LDPE and 37 wt% untreated and heat-treated WTC containing

0% and 6% MAPE………..………..268 Figure 4.142: Storage modulus curves of dry as-moulded and indoor

exposed LDPE and 37 wt% untreated and heat-treated

WTC containing 0% and 6% MAPE……….273

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Figure 4.143: Loss modulus curves of dry as-moulded and indoor exposed LDPE and 37 wt% untreated and heat-treated WTC containing

0% and 6% MAPE………274 Figure 4.144: Tan delta curves of dry as-moulded and indoor exposed LDPE

and 37 wt% untreated and heat-treated WTC containing

0% and 6% MAPE………..……….275 Figure 4.145: Tensile modulus of dry as-moulded and indoor exposed composites

as a function of wood content and treatment temperature………279 Figure 4.146: Tensile modulus of 37 wt% dry as-moulded and indoor exposed

composites containing 6% MAPE……….279 Figure 4.147: Tensile strength of indoor and dry as-moulded composites as a

function of wood content and treatment temperature………....280 Figure 4.148: Tensile strength of 37 wt% dry as-moulded and indoor exposed

composites containing 6% MAPE………...……….280 Figure 4.149: Tensile strain of dry as-moulded and indoor exposed composites

as a function of wood content and treatment temperature………281 Figure 4.150: Tensile strain of 37 wt% dry as-moulded and indoor exposed

composites containing 6% MAPE………..……….281 Figure 5.151: Flexural modulus of dry as-moulded and indoor exposed samples

as a function of wood content and treatment temperature…..……….283 Figure 4.152: Flexural modulus of 37 wt% dry as-moulded and indoor exposed

samples containing 6% MAPE………...283 Figure 4.153: Flexural strength of dry as-moulded and indoor exposed samples

as a function of wood content and treatment temperature…………...284 Figure 4.154: Flexural strength of 37 wt% dry as-moulded and indoor exposed

samples containing 6% MAPE………284 Figure 4.155: Flexural displacement of dry as-moulded and indoor exposed samples

as a function of wood content and treatment temperature………..…..285 Figure 4.156: Flexural displacement of 37 wt% dry as-moulded and indoor

exposed composites containing 6% MAPE………...……...285

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Figure 4.157: Peak load of dry as-moulded and indoor exposed samples as a

function of wood content and heat treatment………..…….……287 Figure 4.158: Peak load of 37 wt% dry as-moulded and indoor exposed

samples containing 6% MAPE………...…………..287 Figure 4.159: K_c of dry as-moulded and indoor exposed samples as a

function of wood content and heat treatment………..…288 Figure 4.160: Kc of 37 wt% dry as-moulded and indoor exposed samples

containing 6% MAPE………...………288 Figure 4.161: energy to failure of dry as-moulded and indoor exposed

samples as a function of wood content and heat treatment……..…….289 Figure 4.162: energy to failure of 37 wt% dry as-moulded and indoor

exposed samples with 6% MAPE………..………...289 Figure 4.163: Gc of dry as-moulded and indoor exposed samples as a

function of wood content and heat treatment………290 Figure 4.164: G_c of 37 wt% dry as-moulded and indoor exposed samples

with 6% MAPE………..…290

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LIST OF TABLES

Page

Table 2.1: Mechanical properties of some natural and man-made fibres……...………34

Table 3.1: Properties of LDPE and MAPE……….39

Table 3.2: Formulations of composites………...………...43

Table 3.3: University of Malaya weather data from April 1^st to December 31^st 2011………..46

Table 4.1: Chemical composition of red balau saw dust………..…………..53

Table 4.2: TGA parameters of wood flour, LDPE and composites………....57

Table 4.3:DSC data of dry as-moulded samples………..……..71

Table 4.4: DMA data of dry as-moulded samples………..………....80

Table 4.5: Water absorption data of wood flour/LDPE composites……….147

Table 4.6: TGA data of moisture saturated samples……….152

Table 4.7: DSC data of moisture saturated samples………..…………...156

Table 4.8: DMA data of moisture saturated samples………..………164

Table 4.9: TGA/DTG data of buried composites………..………..190

Table 4.10: DSC data of buried samples………..………...193

Table 4.11: DMA data of buried samples………200

Table 4.12: TGA data of samples exposed to outdoor weathering………..232

Table 4.13: DSC data of outdoor weathered samples………..236

Table 4.14: DMA data of outdoor weathered samples………..………..243

Table 4.15: TGA/DTG data of indoor exposed samples…………..………...266

Table 4.16: DSC data of exposed indoors samples…………..………...269

Table 4.17: DMA data of indoor exposed samples……….276

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LIST OF SYMBOLS

a/D Notch-to-depth ratio

ASTM American Society for Testing and Materials ATR Attenuated total reflectance

DA Apparent diffusion coefficient DMA Dynamic mechanical analysis DSC Differential scanning calorimetry D_T True diffusion coefficient

DTG Derivative thermogravimetry DT_p Derivative peak temperature

Eʺ Loss modulus

Eʹ Storage modulus

FTIR Fourier transform infrared Gc Critical strain energy release rate

GPa Giga pascal

HDPE High density polyethylene

ICTAC International Confederation of Thermal Analysis and Calorimetry

ILSS Interlamina shear stress K_c Critical stress intensity factor

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Kg Kilogram

LDPE Low density polyethylene

M Mass

MAPE Maleic anhydride polyethylene MFI Melt flow index

MPa Mega Pascal

P Peak load

PE Polyethylene

PMMA Polymethylmethacrylate

PP Polypropylene

PRF Permanent reserved forest

PS Polystyrene

PVC Polyvinyl chloride

RM Ringgit Malaysia

S/D Span to depth ratio

SEM Scanning electron microscopy SEN Single edge notch

T_E^ Temperature at maximum Eʺ

T_50% Temperature at 50% degradation

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Tan δ Tan delta

Tc Crystallisation temperature TGA Thermogravimetric analysis Tm Melting temperature

Tonset Onset temperature

Tp Degradation peak temperature UV Ultra violet radiation

V Volume

W energy to failure

W√2 Tan delta transition region width

wt% Weight percent

WTC Wood thermoplastic composites X_c Degree of crystallinity

ΔHc Enthalpy of crystallization ΔHm Enthalpy of fusion

ρ Density

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LIST OF APPENDIX

Page Appendix A: TGA thermograms showing the amount of moisture

absorbed by the composites made from 37 wt% untreated

and heat-treated at different conditionings………..………..315 Appendix B: Gc calculations of dry as-moulded and conditioned samples………….320 Appendix C: Kc calculations of dry as-moulded and conditioned samples………….323 Appendix D: Publications and conference presentations………326

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TABLE OF CONTENTS

Page

TITLE PAGE………..i

LITERARY WORK DECLARATION………..……..ii

ABSTRAK………..………..…...iii

ABSRACT………...v

ACKNOWLEDGEMENTS……….vii

LIST OF IGURES……….ix

LIST OF TABLES……….………..xxi

LIST OF SYMBOLS……….xxii

LIST OF APPENDIX……….xxv

TABLE OF CONTENTS………..xxvi

CHAPTER ONE: INTRODUCTION 1 Introduction………... ……....…………..1

1.1 Background………….……… ……...…...1

1.2 Justification………...…...5

1.3 Research objectives…………...………..……….12

1.4 Scope of work………..………...…....…..12

1.5 Thesis outline………...….13

CHAPTER TWO: LITERATURE REVIEW 2 Literature review………..….15

2.1 Preamble………..…15

2.2 Wood components………..…..15

2.2.1 Cellulose………..….15

2.2.2 Hemicellulose………..….17

2.2.3 Lignin………..….18

2.2.4 Extractives and inorganics………..….19

2.3 Wood modification methods………..….20

2.3.1 Chemical treatment………..….21

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2.3.1.1 Alkaline treatment…..………....21

2.3.1.2 Acetylation……….….23

2.3.1.3 Silane treatment……….……….……24

2.3.1.4 Benzoylation………..….25

2.3.1.5 Peroxide treatment…...……….…………..26

2.3.1.6 Maleated coupling………...27

2.3.2 Physical modification………...……….29

2.3.2.1 Plasma treatment……….29

2.3.2.2 Thermal treatment………...……...………….30

2.4 Wood thermoplastic composites………...32

2.4.1 Natural/manmade fibre/fillers/hybrid composites………….…....32

2.4.2 Processing wood thermoplastic composites………...……...34

2.4.2.1 Extrusion/compounding……….……….34

2.4.2 Moulding………...……….37

Compression/injection moulding……….……….…..37

Chapter three: Experimental 3 Experimental………..39

3.1 Materials………...39

3.2 Chemical characterisation………....40

3.2.1 Chemical constituents of wood flour ……….……...40

3.2.2 Fourier transform infrared spectroscopic analysis………...40

3.3 Determination of wood flour density………...….40

3.4 Processing……….41

3.4.1 Wood pre-treatment………...41

3.4.2 Compounding………....42

3.4.3 Injection moulding……….………....42

3.5 Conditioning………44

3.5.1 Water absorption tests……….………..44

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3.5.2 Thickness swelling………..…...44

3.5.3 Out door exposure……….…44

3.5.4 Indoor exposure……….…45

3.5.5 Burial tests……….…45

3.6 Thermal analysis……….…..46

3.6.1Thermogravinetric analysis………..…………...46

3.6.2 Differential scanning calorimetry………..47

3.7 Dynamic mechanical analysis………..47

3.8 Mechanical testing………47

3.8.1Tensile testing………47

3.8.2 Flexural testing……….49

3.8.3 Impact testing……….50

3.9 Scanning electron microscopy………..51

Chapter four: Results and discussion 4 Results and discussion………..………....52

4.1 Wood flour characterisation………...…..….52

4.1.1 Thermal treatment of wood flour………...52

4.1.2 Chemical composition………...52

4.1.3 FTIR analysis of wood flour………..54

4.1.4 Thermal stability………....55

4.2 Dry as-moulded composites………...…..58

4.2.1 Processing………...58

4.2.2 Thermal properties……….59

4.2.2.1 Thermogravimetric analysis (TGA)………...59

Effect of wood content………60

Effect of heat treatment……….60

Effect of MAPE content………...64

4.2.2.2 Differential scanning calorimetry DSC)….…………...68

Melting behaviour………..68

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Effect of heat treatment………..69

Crystallisation behaviour………....72

Effect of wood content………..73

4.2.3 Dynamic mechanical analysis………...…….75

4.2.3.1 Theoretical considerations………...75

4.2.3.2 Storage modulus………….………....77

Effect of MAPE content………79

4.3.2.3 Loss modulus………..83

Effect of MAPE content………85

4.3.2.4 Tan delta, Tan δ……….…….87

Effect of heat treatment……….…88

Effect of MAPE content………..…………..89

4.2.4 Mechanical properties……..……….……...…..92

4.2.4.1 Tensile properties…..……….92

Tensile modulus………..………92

Effect of MAPE content……….95

Tensile strength………..………99

Effect of heat treatment………100

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Effect of MAPE content………..100

Tensile strain…..………...103

Effect of wood content………...103

Effect of heat treatment………….…………...105

Effect of MAPE content………..105

4.2.4.2 Flexural properties……….…...107

Flexural modulus……….…….107

Effect of wood content………….……….……107

Effect of heat treatment…….…………..……108

Effect of MAPE content…….………...109

Flexural strength………...110

Effect of wood content……….110

Effect of MAPE content………..………112

Flexural displacement………...114

4.2.4.3 Impact properties…….……….117

Peak load, P………..……121

Effect of heat treatment…….……….…..122

Effect of MAPE content……….…..124

Critical stress intensity factor or fracture toughness, Kc ………126

Effect of wood content……….………...126

Effect of heat treatment……….…..127

Effect of MAPE content……...128

Energy to failure, W……….129

Effect of wood content……….………129

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Effect of heat treatment…….………...………130

Effect of MAPE content….………..131

Critical energy release rate, Gc………….…………....132

Effect of wood content……….…132

Effect of heat treatment…….………...132

4.3 Effect of different environmental conditioning………..……..136

4.3.1 Water absorption behaviour………...……...…...136

Effect of MAPE content………..……….…140

4.3.1.1 Kinetics of water absorption……….141

4.3.1.2 Kinetic parameters n and k………..……….143

4.3.1.3 Diffusion coefficients………..….145

4.3.1.4 Thickness swelling behaviour………..………….…146

4.3.1.5 Thermal properties………150

Thermogravimetric analysis………...………...150

Differential scanning calorimetry………....……..153

4.3.1.6 Dynamic mechanical properties……...………157

Storage modulus………..……….157

Loss modulus………...158

Tan delta………..…….159

4.3.1.7 Mechanical properties………...165

Tensile properties………...165

Tensile modulus………....165

Tensile strength……….166

Tensile strain……….167

Flexural properties………....171

Flexural modulus………..171

Flexural strength………...…………171

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Flexural displacement………...172

Impact properties………..…175

Peak load………..175

Critical stress intensity factor………...176

energy to failure………...179

Critical energy release rate………...180

4.3.2 Effect of outdoor soil burial……….………....184

4.3.2.1 Physical appearance………...185

Thermogravimetric analysis………...…...187

Differential scanning calorimetry………...…..191

4.3.2.3 Dynamic mechanical analysis………...………194

Storage modulus………...194

Loss modulus………196

Tan delta………...198

Tensile properties………..202

Tensile modulus………...……….202

Tensile strength………...203

Tensile strain………...………..203

Flexural properties………208

Flexural modulus…………...………...……208

Flexural strength………..……….208

Flexural displacement………..209

Impact properties……….……….212

Peak load………..……….212

Critical stress intensity factor………...213

energy to failure………..213

Critical strain energy release rate………….…………214

4.3.3 Outdoor weathering………...220

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4.3.3.1 Chemistry of outdoor weathering……….221

4.3.3.2 Physical appearance………..224

Thermogravimetric analysis………...…..229

Differential scanning calorimetry………...………..233

4.3.3.4 Dynamic mechanical properties………...………237

Storage modulus………...237

Loss modulus………238

Tan delta………..……….…239

4.3.3.5 Mechanical properties………..….244

Tensile modulus………....244

Tensile strength………...246

Flexural properties………...….251

Flexural modulus………...251

Flexural strength………...……....251

Flexural displacement………..….252

Impact properties……….……….256

Peak load………...256

Critical stress intensity factor………...………256

energy to failure………..257

Critical strain energy release rate……..………...257

4.3.4 Effect of the indoor environment………..………..262

4.3.4.1 Physical appearance………..262

Thermogravimetric analysis………...………..264

Differential scanning calorimetry………..……..267

4.3.4.3 Dynamic mechanical properties…………...…...……….270

Storage modulus………..……….270

Loss modulus…………..………..270

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Tan delta………...………...……….271

Tensile modulus………...277

Tensile strength……….277

Flexural properties………...……….282

Impact properties………..286

Peak load, P and critical stress intensity factor, Kc ……….286

energy to failure, W and critical strain energy release rate, G_c……….286

CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS FOR FURTHER WORK 5.1 Conclusion………...…...291

5.2 Recommendations for further work……….………..295

REFERENCES……….……...297

APPENDIX………..315