THE EFFECT OF SURFACE TREATMENT ON COMPOSITE INTERFACE,TENSILE PROPERTIES AND WATER ABSORPTION OF SUGAR PALM

FIBER/POLYPROPYLENE COMPOSITES

WAN ZUBAIDIE BIN WAN ZAHARI

A thesis submitted infulfillment of the requirement for the award of the

Degree of Master of Mechanical Engineering

Faculty of Mechanical and Manufacturing EngineeringUniversiti Tun Hussein Onn Malaysia

SEPTEMBER 2017

Dedicated specially to my parents and siblings;Wan Zahari & Wan Zainab, Zulhusmie, Zainal Asri, Athirah and Aqilah

To my special friends;Ahmad Fuad and Ahmad Afifi

To my supervisors;Dr Izzuddin Zaman, Dr Denni Kurniawan and Dr fethma Md Nor

And all those who have been a great help in the completion of this thesisMy love to all of you will remain forever. . .

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ACKNOWLEDGMENT

All the Praises and Thanks to Allah SWT and may peace be upon Prophet MuhammadSAW, the messenger of Allah. With blessing and generosity from Allah SWT, finallyI have the strength to complete this research successfully. I would like to expressmy most sincere gratitude to my supervisor, Dr. Izzuddin Zaman who has providedconsiderable invaluable insights, guidance and advice, and without any hesitate helpme to enhance the quality of my work. His intelligence and determination have been asource of inspiration, and his demands for quality and perfection give me a challenge inorder to accomplish my project. In addition, I would like to express my appreciation tomy co-supervisor, Dr. Denni Kurniawan who has helped and guided me in this study.His knowledge and advice help me complete my thesis.

Special thanks dedicated to all laboratory staff for their willingness to assist meduring the experiment session. Not to forget, special thanks to Prof. Byung Sung Kim,Prof. Jung Il Song and Korea Institute of Materials Science for helping me through theresearch.

Not to forget to my beloved parent, Hj Wan Zahari Hj Samat and Hjh WanZainab Hj Wan Nawan, for their endless support and encouragement through out mystudy. To all my siblings and others family members too that give a moral supportduring my study.

Finally, I dedicate this thesis to my beloved friends especially my researchgroup members for their encouragement, support and never lose hope in sending me aprayers for the success.

Wan Zubaidie Bin Wan Zahari, Kota Bharu, Kelantan

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ABSTRACT

The rising concern towards environmental issues besides the requirement for moreflexible polymer-based material has led to increasing of interest in studying aboutgreen composite. Sugar palm fiber (SPF) is a versatile fiber plant employed with widerange of application such as in automotive, packaging and buildings construction. Thisresearch was aimed to study the effect of surface treatment on composite interface,tensile properties and water absorption of sugar palm fiber/polypropylene (SPFPP)composite by using different surface treatments such as silane (Si), atmospheric glowdischarge plasma (Agd) and maleic anhydride (Ma). Silane treatment was carried outby using immersion method, the Agd plasma was conducted using polymerizationand lastly polypropylene grafted maleic anhydride by using melting approach. TheSPFPP composite was prepared by using injection moulding with fiber content var-ied from 10–30wt%. The effect of interface enhancement on morphology, mechanicalproperties and water uptakes of SPFPP composites were then investigated by usingFTIR, FESEM, tensile test and water absorption test. Overall, the outcome showsthat all types of surface treatments had improved the interface of SPFPP composite,thus improving its tensile properties compared to the benchmark untreated SPFPP (Ut-SPFPP) composites and polypropylene. The 30wt% Ma-SPFPP composite shows thehighest improvement in tensile properties with 58% and 27% increase in the respectiveYoung’s Modulus and tensile strength value compared to Ut-SPFPP composite, while10wt% Ma-SPFPP composite shows the smallest reduction in elongation compared toNeat PP. On the other hand, the 30wt% Si-SPFPP composite shows the lowest waterabsorption with 20% reduction respective to Ut-SPFPP composite. In conclusion, thesurface treatments have proven succesfull in enhancing the natural fiber-polymer in-terface and improve the tensile properties of SPFPP composite with Ma-SPFPP showsthe highest improvement, followed by Agd-SPFPP and Si-SPFPP composites.

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ABSTRAK

Peningkatan kebimbangan terhadap isu-isu berkaitan dengan alam sekitar disampingpermintaan terhadap bahan polimer yang lebih fleksibel telah membawa kepada pen-ingkatan minat dalam mengkaji komposit ‘hijau’ (mesra alam). Gentian gula kabungmerupakan gentian tumbuhan yang serba boleh dengan kepelbagaian aplikasi kegu-naan seperti dalam automotif, pembungkusan dan binaan bangunan. Kajian ini men-sasarkan pemahaman mengenai kesan rawatan permukaan ke atas perhubungan per-mukaan komposit, ciri-ciri tegangan (mekanikal) dan serapan air bagi komposit gen-tian gula kabung dan polimer polypropylene (SPFPP) dengan menggunakan rawatanpermukaan seperti rawatan silane (Si), pempolimeran plasma pelepasan cahaya atmos-fera (Agd) dan rawatan maleic anhydride (Ma). Rawatan silane dijalankan melaluikaedah rendaman, sementara rawatan Agd menggunakan kaedah pempolimeran, danakhir sekali pencantuman maleic anhydride dengan polypropylene melalui pendekatankaedah pencairan. Komposit SPFPP disediakan dengan kaedah suntikan acuan bersamakandungan gentian bermula dari 10-30wt%. Kesan penambahbaikan perhubungan per-mukaan komposit ke atas morfologi, ciri-ciri tegangan dan kadar resapan air pada kom-posit SPFPP dikaji menggunakan FTIR, FESEM, ujian ketegangan dan ujian penyer-apan air. Secara keseluruhannya, hasil menunjukkan bahawa kesemua rawatan per-mukaan telah menambah baik perhubungan permukaan komposit bagi komposit SPFPP,sekaligus meningkatkan ciri-ciri mekanikal berbanding komposit rujukan iaitu SPFPPkomposit tidak terawat (Ut-SPFPP) dan polypropylene. Komposit 30wt% Ma-SPFPPmenunjukkan penambahbaikkan paling tinggi dengan peningkatan ciri-ciri tegangansebanyak 58% dalam modulus keanjalan dan 27% peningkatan dalam nilai kekuatantegangan berbanding komposit Ut-SPFPP, manakala komposit 10wt% Ma-SPFPP me-nunjukkan perbezaan pengurangan paling kecil dalam nilai pemanjangan berbandingneat polypropylene. Sementara itu, komposit 30wt% Si-SPFPP menunjukkan kadarresapan air paling kurang dengan pengurangan sebanyak 20% berbanding kompositUt-SPFPP. Kesimpulannya, rawatan permukaan telah berjaya membuktikan penam-bahbaikan ke atas perhubungan permukaan bahan semula jadi dengan polimer sertameningkatkan ciri-ciri tegangan komposit SPFPP dimana komposit Ma-SPFPP me-nunjukkan peningkatan yang paling tinggi, diikuti oleh Agd-SPFPP dan Si-SPFPP.

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CONTENTS

DECLARATION ii

DEDICATION iii

ACKNOWLEDGMENT iv

ABSTRACT v

ABSTRAK vi

LIST OF FIGURES x

LIST OF TABLES xii

LIST OF APPENDICES xiii

LIST OF SYMBOLS AND ABBREVIATIONS xiv

CHAPTER 1 INTRODUCTION 11.1 Research Background 11.2 Problem Statement 41.3 Objectives of Study 51.4 Scopes of Study 51.5 Significant of Study 61.6 Thesis Outline 7

CHAPTER 2 LITERATURE REVIEW 82.1 Composite 82.2 Natural Fiber 10

2.2.1 Fibrous plants reinforcement 132.2.2 Bast fiber 142.2.3 Sugar palm tree 152.2.4 Sugar palm fiber 16

2.3 Polymer Matrix 182.3.1 Polypropylene 20

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2.4 Potential Applications of Natural Fiber/PP Composite 202.5 Constituents Characteristic 212.6 Surface Treatment 23

2.6.1 Chemical surface treatment 232.6.2 Physical surface treatment 29

2.7 Effect of Surface Treatment on Tensile Properties and Wa-ter Absorption 302.7.1 Summary of research gaps 36

CHAPTER 3 RESEARCH METHODOLOGY 393.1 Introduction 393.2 Materials Preparation 423.3 Instrumentations 433.4 Preparation of Surface Modification 48

3.4.1 Silane treatment 483.4.2 Atmospheric pressure glow discharge 493.4.3 Maleic anhydride grafted polypropylene 52

3.5 Composite Fabrication 533.6 Injection Process 553.7 Characterization of Composites 55

3.7.1 Material characterization 563.7.2 Tensile properties characterization 563.7.3 Surface morphology characterization 583.7.4 Water absorption 59

CHAPTER 4 RESULTS AND DISCUSSIONS 614.1 Material Structure Composition 614.2 Tensile Properties of SPFPP Composites 65

4.2.1 Young’s modulus 674.2.2 Tensile strength 694.2.3 Elongation at break 71

4.3 Surface Morphology of SPFPP Composite 724.3.1 Fiber pulling behaviour 734.3.2 Cross-sectional of SPFPP composite 76

4.4 Water Absorption Behaviour of Composite 784.5 Relationship between Surface Morphology, Tensile Prop-

erties and Water Absorption 81

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 835.1 Conclusion 83

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5.2 Recommendations 85

REFERENCES 87

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LIST OF FIGURES

FIGURE NO TITLE PAGE

2.1 Composites arrangement 102.2 Green composite concept 112.3 Percentage of natural fiber in plastic composite 122.4 Application of natural fiber composite 132.5 Classification of plant natural fiber 132.6 Hemp plant and bast fiber 142.7 Sugar palm tree and sugar palm fiber 152.8 Potential application of natural fiber / PP polymer composite 212.9 ’Hydrophilic’ vs. ’Hydrophobic’ contact angle 222.10 Surface treatment 232.11 Interaction of silane 262.12 MAPP grafting 282.13 Effect of fiber treatment on tensile strength of natural fiber com-

posite 28

3.1 Research flow chart 403.2 Materials 423.3 Surface Treatment Chemicals 433.4 Atmospheric glow discharge plasma chamber 453.5 Brabender plastograph mixer 453.6 Hot roll mill mixer 463.7 Plastic granular 463.8 Vacuum oven 473.9 Horizontal screw type injection 473.10 Auto fine coater machine 473.11 Field Emission Scanning Electron Microscope 483.12 Silane treatment process 493.13 Schematic of atmospheric glow discharge plasma system 503.14 Flow process of Agd plasma polymerization 513.15 Ma-PP mixing process 52

x

3.16 Composite pallet fabrication process 543.17 Injection process 553.18 Tensile test specimen dimension 573.19 Tensile test process 583.20 Water absorption testing process 60

4.1 FTIR spectra of SPFPP composite treated with silane treatment 624.2 Reaction of grafted vinyltrimethoxy silane with SPFPP 624.3 FTIR spectra of SPFPP composites treated with AGD plasma 634.4 FTIR spectra of SPFPP composites treated with maleic anhydride 644.5 Reaction of grafted Ma-PP with SPFPP composite 644.6 SPFPP composite sample 654.7 Stress-strain curve of SPFPP composite 664.8 Young’s modulus of neat PP and SPFPP composite 684.9 Tensile strength of neat PP and SPFPP 694.10 Elongation at break of neat PP and SPFPP composite 724.11 FESEM images of tensile fracture of Ut-SPFPP composite 734.12 FESEM images of tensile fracture of Si-SPFPP composite 744.13 FESEM images of tensile fracture Agd-SPFPP composite 754.14 FESEM images of tensile fracture of Ma-SPFPP composite 754.15 Cross-section view of Ut-SPFPP composite 764.16 Cross-section view of Si-SPFPP composite 764.17 Cross-section view of Agd-SPFPP composite 774.18 Cross-section view of Ma-SPFPP composite 784.19 Water absorption of SPFPP composite via fiber loading and sur-

face treatments 79

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LIST OF TABLES

TABLE NO TITLE PAGE

2.1 Types of composites 102.2 Classification of natural fiber 112.3 Uses of Arenga pinnata parts 162.4 Chemical composition of vegetable fiber 172.5 Physical-mechanical of natural fiber 182.6 Advantages and disadvantages of different natural fiber 182.7 Polymeric matrix 192.8 Chemical treatment on natural fiber 242.9 Comparison between surface treatment on matrix of composites 252.10 Silane treatments structure and functionality 262.11 Effect of silane treatment on coir fiber 272.12 Types of plasma treatment 302.13 Related previous studies 31

3.1 Surface treatment on fiber reinforcement and polymer matrix 413.2 Classification of specimens 413.3 Instrumentations 433.4 Sugar palm fiber/PP composite specimen geometry 57

4.1 Summary of Tensile Properties 67

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A FTIR Data 95

B Tensile Test Data 100

C FESEM Image Analysis 103

D Water Absorption Result 112

E List of Publications 117

F Appreciations 118

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LIST OF SYMBOLS AND ABBREVIATIONS

%T Percentage of transmittance

wt% Weight percentage

Mt% Percentage of water absorption

Wf Final weight

Wo Original weight

Agd Atmospheric glow discharge plasma

ASTM American Society of the International Association for Testing and Materials

FESEM Field emission scanning electron microscope

FTIR Fourier transform infrared spectroscopy

Ma Maleic anhydride

PP Polypropylene

Si Vinyltrimethoxy silane

SPF Sugar palm fiber

SPFPP Sugar palm fiber/polypropylene

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CHAPTER 1

INTRODUCTION

This chapter introduces research background, including problem statement, hypothesisand the significant of knowledge derived herein. It highlights aims of the project in thecontext of knowledge gaps identified in this field. The chapter ends with organizationof the whole thesis and a brief description for each chapter.

1.1 Research Background

In this modern world, the excitement works on natural fibers as reinforcement in poly-mer composite are triggered by modern vision on green technology. The term greentechnology, eco-friendly and sustainability are used to refer to the materials that givelower environmental impact in producing the products. The concept contains five im-portant elements which are renewing (product and resource), recycling design, reduc-ing resource, rethinking (overall product), and responsibility towards environments andothers (Bachtiar et al., 2009; Ashori, 2008; Azwa et al., 2013; Baillie, 2005). Theseconcerns have led the interest to use green composite which filled with natural organicfillers rather than common synthetic material. Besides, the availability of natural fiberin large amount, lowered market price and its degradation behaviour are able to ben-efit composite instantly such as low density, less machining process and low hazardstowards health, in which contrast to glass fiber that hazardous on health, brittle andcostly (Owen, 2014). One of the potential natural fibers that is extensively exploredand researched recently is sugar palm fiber.

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Sugar palm fiber which commonly known as ijuk fiber (Arenga pinnata), is thedark fibrous bark of sugar palm tree. For so many years, the fibers have been around formaking various of product such as roof top, rope and brush (Ali et al., 2010; Azman,2013; Bachtiar et al., 2008; Ishak et al., 2012, 2013; Mogea et al., 1991; Ticoalu et al.,2014). It is well known that sugar palm fiber has their advantages in tensile strengthproperties and can withstand longer life of degradation, which is less effected by heatand moisture compared to coir fiber; besides durable and having good resistance tosea water (Ishak et al., 2012). By having this unique properties, sugar palm a suitablematerial for making product that is water resistance such as rope, brooms, or used asfilters to clear the water (Mogea et al., 1991). As for composite application, sugar palmfiber is still an unfamiliar used natural fiber as potential green fiber filler.

Among the polymer material, the polypropylene (PP) is a type of thermoplasticthat has been applied in various composite applications as a binder and matrix (Kabiret al., 2012). By having good characteristics such as recyclable, formable and ductile,PP-based composites have been used extensively in packaging, manufacturing, andpiping system. Polypropylene is in many aspects similar to polyethylene, especiallyin solution behaviour and electrical properties. The properties of polypropylene aredepending on the molecular weight and molecular weight distribution, crystallinity,type and proportion of co-monomer and the isotacticity (Painter et al., 1977).

Basically, PP polymer and natural fiber filler are not compatible to form asgreat composite. In order to enhance the compatibility between natural fibrous fillerand matrix of PP, coupling agents which refer to surface treatments have been used.Previously, there are several surface treatments that were employed to improve thecomparability of natural fiber (Li et al., 2007). The surface treatment is divided intothree types which are: (i) chemical surface treatment, (ii) physical surface treatmentand (iii) physic-chemical surface treatment (Fuqua et al., 2012). These treatmentseither can be carried out on the reinforcement filler or even the matrix of the compositesin order to improve the surface contact.

Silane which can be categorized under chemical treatment, is recognized asa common coupling agent for adherence the fibers to polymer matrix by stabiliz-ing the composite filler material. Generally, silane coupling agent is used to reducenumber of cellulose hydroxyl groups in fiber matrix interfaces. In presence of mois-ture, hydrolysable alkoxy group leads to the formation of silanols, which then reactwith hydroxyl group of the fibers forming stable covalent bonds to cell wall that arechemisorbed onto the fiber surface (Xie et al., 2010). Silane coupling agent is alsofound to be effective in modifying natural fiber-polymer matrix interface and increas-

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ing the interfacial strength. It was verified that the interaction between silane couplingagent modified fiber and matrix was much stronger than alkaline treatment, thus led tocomposites with higher tensile strength (Redzuan, 2012).

Other types of surface treatment that usually applied on the fiber type filler isplasma polymerization. By focusing on the physical treatment, plasma sources areused to generate a discharge gas that provide energy to activate liquid monomer, con-tains a vinyl group, for initiating polymerization. The fibrous filler produced from thistechnique is generally a highly branched and cross-linked (Kurniawan et al., 2012).The biggest advantage of this process is that filler reinforcement can be directly at-tached to a desired surface while the chains are growing which reduces step necessaryfor other coating process such as grafting. This is very useful for coatings of 100picometers to 1 micrometers thickness (Ha et al., 2011).

In the previous study by El-Sabbagh (2014) stated that a lot of method was em-ployed to enhance the adhesion between matrix and reinforcement including physicaltreatment and chemical treatment. As for matrix surface treatment, maleic anhydride(Ma) is a common coupling agent that providing efficient interaction on functional be-tween matrix and surface of fiber (Cantero et al., 2003). The Ma grafted to PP knownas treated polymer is a well-known treatment used to enhance the interfacial for poly-mer matrix. During the grafting process, Ma reacts with hydroxyl group in fiber whilePP co-crystallizes with unmodified fiber and form the bridge between fiber and treatedPP (Li et al., 2007). In this experiment, the weight percentage instead of volume per-centage is applied since it is the most common equation used in the calculation of fiberweight during mixing with polymer matrix. According to Gibeop et al. (2013) andKurniawan et al. (2013), the reinforcement fibers cannot being determined by volumefraction due to a large error of volume determination from hydrostatic methods. Thus,the detail research on mechanical and chemical properties of sugar palm fiber weresuggested in recommendation section.

In this study, the interface of sugar palm fiber/polypropylene composites (SPFPP)were enhanced using three approaches: (i) silane treatment, (ii) atmospheric glow dis-charge plasma (Agd) polymerization treatment and (iii) maleic anhydride treatment.The study aims to investigate the effect of these surface treatments on composite inter-face, the mechanical properties of SPFPP composite such as increase tensile strengthand Young’s modulus, and water absorption of composites.

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1.2 Problem Statement

Nowadays, the application of composites play an important parts as substitution ma-terials for others in various fields of application such as construction and automotive.However, the dependencies towards synthetic fibers, for example fiber glass is notenough, in addition of disadvantages of these fiber which highly in cost, hazardousmaterial and non-renewable materials (Ashori, 2008; Azwa et al., 2013; Furqan et al.,2015). Therefore, natural fiber reinforcement is suitable replacement for synthetic fiberin composite application. The fibers are emerging as low-cost, light weight, recyclableand eco-friendly material with low density and renewable resources (Baillie, 2005).

In spite of these advantages, most of natural fibers has a tendency to form ag-gregates during process due to poor heat resistance and low moisture resistance (Sahariet al., 2012; Ticoalu et al., 2014). As the alternative, sugar palm fiber, which is goodin heat and moisture resistant, can be consided as a potential natural fiber for rein-forcement in composite based polymer. In addition to research study, sugar palm fiberis still considered new and much to be explored as reinforcement in polymer basedcomposite.

As for polymer, the thermoplastic material is consider as the best option interm of “green technology” due to five elements concept which prefer the recyclablematerial rather than thermoset material (Azwa et al., 2013; Bavan & Kumar, 2011;Coutinho & Costa, 1999). Nevertheless, the thermoplastic typically performed poorlyin long-term loading because linear polymer molecule exhibit strong time and temper-ature dependent response. Of thermoplastic, Polypropylene (PP) is a low cost indus-trial material, light weight, recyclable, eco-friendly and easy to process (Baillie, 2005;Coutinho & Costa, 1999). Besides, the properties have district features dependingupon cellulose content which varies from fiber to fiber.

As the constituents in composite, the interface between reinforcement sugarpalm fiber and matrix PP is weak due to its low compatibility. This is because the char-acteristics of most natural fiber act as water storage and attract to water (hydrophilic)which contrast to hydrophobic materials of PP (Ashori, 2008; Coutinho & Costa, 1999;El-Sabbagh, 2014). The poor interface between reinforcement and matrix has leads todegradation of mechanical properties of PP composites because of increment numberof voids and appearance of moisture in sugar palm fibers. In order to overcome theseweaknesses commonly faced by natural fiber polymer based composite, the surfacetreatment is introduced to improve the mechanical properties of composite. Based onthe past literature review, however the sugar palm fiber reinforced polypropylene com-

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posites lack being exposed to various surface treatments and commonly being treatedonly with alkaline treatment (Bachtiar et al., 2008, 2009).

Lastly, being the natural fiber composites had reduced the individual character-istic of material such as mechanical and physical properties. Thus, the green compos-ites cannot achieve higher mechanical properties as synthetic composites such as fiberglass. Due to these, the use of natural fiber or green composite as the replacement tosynthetic fiber composites seems doable by improving the structure and interface ofnatural fiber (Fuqua et al., 2012; Furqan et al., 2015; La Mantia & Morreale, 2011).As physical properties, the characteristics of natural fiber that tend to absorb and con-tain the moisture lead to disadvantages of composite. Therefore, the characteristic ofcomposite must be improvized to overcome the deficiency (Kabir et al., 2012; Li et al.,2007; Xie et al., 2010).

1.3 Objectives of Study

In order to address the above aforementioned problems, the objectives of the study areto be designed as follows:

i. To determine the effect of different surface treatments such as silane, atmo-spheric glow discharge polymerization and maleic anhydride on the interfaceand tensile properties of sugar palm fiber/polypropylene composite.

ii. To minimize the water absorption of sugar palm fiber/polypropylene compositesby treated with surface treatments.

iii. To determine the surface morphology-tensile properties-water absorption rela-tionships of sugar palm fiber/polypropylene composites.

1.4 Scopes of Study

In this research, polypropylene (PP) was used as the matrix, while sugar palm fiberas reinforcement in the composites. The vinyltrimethoxy silane (Si) and AtmosphericGlow Discharge (Agd) plasma were both used for treatment of fiber surface, whilemaleic anhydride (Ma) was employed for chemical treatment of the matrix. The im-mersion method was implemented for silane treatment, polymerization method was

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for Agd, and melting method for Ma and PP. The untreated sugar palm fiber was pre-pared by cutting the raw SPF in required sizes and immersed in distil water to removedirt and other substance. The cut-off size for sugar palm fiber was 2 mm with theweight percentages of sugar palm fiber used in composites were 10, 20 and 30wt%(both treated and untreated samples). In order to characterize the effect of surfacetreatment on SPFPP composite, Fourier Transform Infrared spectroscopy (FTIR) wasemployed for material structure evaluation, while tensile test refer to ASTM D 638 fortensile properties, field emission scanning electron microscope (FESEM) for morphol-ogy structure and fiber pull-out behaviour analysis, and finally water absorption testwas performed for physical properties evaluation. Five specimens were averaged fortensile test and water absorption, while three sample used for FESEM.

1.5 Significant of Study

Recently, the use of natural fiber composites compared to synthetic fiber compositesare extensively researched due to harmful and disadvantages aspect of synthetic fiber.Thus, “green” technology natural fiber composite now have been common adaptationin many field of work such automotive, industrial manufacturing or even in buildingconstruction. As for sugar palm fiber, its natural resource that plenty in local area,reasonable in price with addition of good mechanical properties has created its fullpotentials as new “green” fiber composite to be developed. To improve the mechanicalproperties of natural fiber composite, several surface treatments are being introduced,either chemical surface treatment or physical surface treatment.

The surface treatment such as silane treatment and AGD polymerization changethe characteristic of fiber, enhance the interface with the matrix and improves the ten-sile properties of composites. The treatment also reduces the water absorption of thecomposite by changing hydrophilic characteristic of the reinforcement. On the otherword, the treatments increase the surface of fiber and modified the characteristic whichallow more surface contact with the matrix and enhance the interface; thus improvingthe mechanical properties of composite.

Besides treatment on the fiber, the research study also focusing on the treatmenton the matrix. The Ma treatment modify the characteristic of the polymer to have betterinterface with natural fiber in the composites. The treatment improves the mechanicalproperties of the composites such strain elongation compared to other treatments whichminimize the reduction of elongation at break. The water absorption can be slightlyreduced by minimizing the void between the reinforcement and matrix. As the result,

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the enhancement of interface and improvement in mechanical properties of the naturalfiber composites can create more opportunity for the replacement of synthetic fibersuch as fiber glass.

Several contributions are also presented in the research study such as: (i) var-ious of possible treatment to enhance the interface and its posibility to improve thetensile properties of green composites, (ii) various of significant testing to identifythe enhancement of interface strength and tensile properties of composites, and (iii)guidelines for preparation of optimum surface treatment of green composites.

1.6 Thesis Outline

This thesis is organized into five chapters. A brief outline of the thesis contents is asfollows:

• Chapter 1 presents general information about overall research study. It involvesthe research background, problem statement, objective, scope and significant ofstudy well as the hypothesis of study.

• Chapter 2 focuses on a fundamental theory of the composites, “green” compos-ites, understanding of natural fiber composites, and different surface treatmentdone on composites component. Apart of that, previous study related to thisresearch in particular the improvement of the mechanical properties of naturalfiber composites were also presented in the chapter.

• Chapter 3 describes the specification of materials and surface treatments used inthe research. This chapter serves the research methodology carried out in thisstudy, including the used instrumentation, step by step procedure of compositespecimens’ fabrication, procedure of composites testing.

• Chapter 4 begins by laying out the results and an in-depth discussion of modifica-tion sugar palm fiber/polypropylene composites (SPFPP), material characteriza-tion analysis, tensile properties, water absorption, and also surface morphologyof composites.

• Chapter 5 is the last chapter that summarises finding of the research project, aswell as the directions for future research works.

CHAPTER 2

LITERATURE REVIEW

This chapter provides readers with a general review on the theory of composite, “green”composites, understanding of natural fiber composites, and surface treatments. It alsocovers details on reinforcement and matrix of the composite used in this study. The lastpart of this section reviews previous surface treatment and its surface target, as well asthe knowledge of its mechanical properties. This section aims to acquire important in-formation related to the area of study, in order to give more idea and identified researchgaps before the project is implemented. All information was gathered mostly from thetext books, journals and internet.

2.1 Composite

The composite can be defined as combination of material either two or more materi-als with significantly different physical or chemical properties, produced new materialwith characteristics that different from individual components and give unique prop-erties. The main material is the matrix or binder of the composites, which purposelysurrounds and binds together fragments of the other materials, called as the reinforce-ment. The reinforcements impart their special mechanical and physical properties toenhance the matrix properties (Baillie, 2005). A synergism produces material prop-erties unavailable from the individual constituent materials, while the wide variety ofmatrix and strengthening materials allows the designer of the product or structure tochoose an optimum combination (La Mantia & Morreale, 2011).

The first modern composite material was made from fiberglass and plastic,which is still widely used for various of product that need precise tolerance, supe-rior strength to weight ratio, corrosion resistance and durable in time besides havinggood in mechanical properties (Ashori, 2008). On its own, the glass is very strong

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but brittle and it will break if bent sharply. The plastic matrix holds the glass fiberstogether and also protects them from damage by sharing out the forces acting on them.Some advanced composites are now made using carbon fibers instead of glass, whichare lighter and stronger than fiberglass but more expensive to produce (Baillie, 2005;Bavan & Kumar, 2011). A composites also can be classified based on the reinforce-ment for the example particulate composite, flake composite, random fiber composite,continuous fiber laminar composite, woven laminar composite and braided composite(Wambua et al., 2003).

The development of new composites and its application is now accelerating,thus the future application of composites will be limited only by the lack of ingenu-ity and unwillingness of individual and the society to explore. Since new ideology intechnology, the word “Green” play a new role in producing new phase of early com-posites to new era comparable with advance composites. Green composites which alsoknown as bio-composites or natural composites are the term used for new studies ofearly composites; mostly from nature such animal, plant and mud (Baillie, 2005).

There are different types of composites that have been studied in Table 2.1.Typical engineered composite materials include:

• Composite building materials such as cement, concrete.

• Reinforced plastics, such as fiber-reinforced polymer.

• Metal composites.

• Ceramic composites (composite ceramic and metal matrices).

In fiber reinforced polymer, polymeric materials were usually used as the matrix of thecomposite. As the fiber reinforced polymer, it can be varies from synthetic to naturalfiber. Figure 2.1 shows the arrangement of fiber-reinforced in the composites structure.In this research, the type of composite was fiber-reinforced and randomly oriented withshort fiber composites arrangement.

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Table 2.1: Types of composites

CompositesParticle-reinforced

Large particleDispersion-strengthened

Fiber-reinforcedContinuous

DiscontinuousAligned

Randomly oriented

StructuralLaminates

Sandwich panels

Figure 2.1: Composites arrangement (Ashori, 2008)

2.2 Natural Fiber

Global awareness of environmental issues has resulted in the emergence of sustainableand environmentally friendly green materials, which are renewable resources based,recyclable, and biodegradable. To develop green composite materials, natural fibershave been used to replace conventional synthetic fibers. In addition, matrix materi-als in the form of biopolymers or bio-resins have been derived from starch, vegetableoils, and protein. Green composites are the next generation of sustainable compos-ite materials and combine natural fibers with natural resins to make light and strongcomposites that are recyclable or biodegradable by trigger as Figure 2.2. Despite thegreat advantages of green composite materials, the green composites are lightweight,decreased wearing on machines, low abrasiveness, absence of health hazardless duringprocessing, application and upon disposal (Saheb et al., 1999; Ashori, 2008; Baillie,2005).

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Figure 2.2: Green composite concept

For natural fibers, they are less homogeneous than glass or carbon, tend to ab-sorb moisture, and are less compatible with conventional resin systems (Ashori, 2008).Pre-processing and treatment are thus required to enhance the performance of the com-posite solution. Generally, natural fiber can be found naturally on many places on earthand can be classified into several types based on their physical form and backgroundas shown in Table 2.2.

Table 2.2: Classification of natural fiber (Ha et al., 2011)

NATURAL FIBER

Vegetable /Plant

Seed Fiber Cotton, Kapok, Risk huskBast Fiber Flex, Hemp, Jute, Kenaf, RamieLeaf Fiber Sisal, Pineapple, Abaca

Animal Wool Agrora, HairSilk

Mineral AsbestosFibrous

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Natural fiber is simply defined as fibrous plant material produced as a result ofphotosynthesis (Azwa et al., 2013; Baillie, 2005; Cheung et al., 2009). These fibersare sometimes being referred as vegetable, biomass, photomass, solarmass or photo-synthetic fibers. The general term used is lignocellulosic fibers, however, the termmeaning ‘lignin and cellulose containing’ where some fiber might only have few or nolignin (Eichhorn et al., 2001).

The use of natural fiber started back in history about 8000 BC, which fiber ofdate, ramie even papyrus play important part during Egypt period, and being noticedas the starter of the early composites during that times. Grass and straw have beenused as reinforcing fiber in mud block (adobe) and pharaoh mummies were wrappedin linen cloth impregnated with salt, resins and honey to reinforce them, proven theearly composite fabrication (Baillie, 2005).

As nowadays, the dependence on renewable resources growing intensely result-ing from the awareness about non-renewable resources that becoming scarce. The 21st

century may be the cellulosic century as research look more and more to renewableplant resources for manufacturing (Pickering, 2008). Thus, the uses of fiber-reinforcedpolymer composite as the replacement in various fields of application become pop-ular. The natural fiber thermoplastic composite as example shows the increased de-mand years by years since 2000. It has been major markets for natural fiber in plasticcomposites, as Figure 2.3, on weight basic (Monteiro et al., 2010). The were severalapplication of natural composite being used as displayed in Figure 2.4.

Figure 2.3: Percentage of natural fiber in plastic composite(Monteiro et al., 2010)

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Figure 2.4: Application of natural fiber composite; a) Interior automotive parts, b) Cas-ing, and c) Roof panel (Monteiro et al., 2010)

2.2.1 Fibrous plants reinforcement

In term of utilization, there are two general classifications of plants producing naturalfibers, which is primary and secondary. The primary plant are those grown for theirfiber content such jute, hemp, sisal and cotton, while the secondary are those where thefiber come as by-product from other primary utilization such palm oil, pineapple, stalkand husk. The common classification for natural fiber is by their botanical type. Usingthis classification, there are six types of natural fibers as shown in Figure 2.5. As sugarpalm fiber, its been consider as secondary plant which the fiber come as by-productfrom other utilization and being classified as bast fiber.

Figure 2.5: Classification of plant natural fiber (Rowell, 2005)

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2.2.2 Bast fiber

Bast fiber as shown as Figure 2.6 is plant fiber that been collected from the phloem ofdicotyledonous plant or "inner bark” sometimes called "skin" which provide structuralstrength and rigidity to the plant stem. These fibers lay under thin bark and exist asfiber bundles or strands and run parallel to the length of stem. Since the valuablefibers are located in the phloem, they must often be separated from the xylem material,and sometimes also from epidermis. The clear and most common bast fiber is hempfiber.

Hemp is the common name for plant from family of Cannabis. Cannabis sativaL.subsp. sativa var. sativa is the variety grown for industrial fiber in Europe, Canada,China and elsewhere, while C. sativa subsp. Indica wth poor fiber quality is primarilygrown for production of recreational and medicinal drugs. It is consider as oldestcultivated fiber plant in world, grown up to 4.5m in height in approximately 140-145day with stem diameter of 4-20mm (Baillie, 2005).

Figure 2.6: Hemp plant and bast fiber (Baillie, 2005)

Differently compare to the hemp, the sugar palm fiber also had consider as thebast fiber since the fiber collected from the “inner bark” or external skin that wrappedaround the sugar palm trunk near to the frond (Sahari et al., 2012). Even though thefiber from the bast fiber, the sugar palms fiber do not need to extract such as mostnatural fiber because it is already in the threaded or filament condition. These alsoone of the reasons the sugar palm fiber being chosen as reinforcement in the researchstudy.

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2.2.3 Sugar palm tree

The sugar palm tree is a member of the Palmae family and naturally a forest species.There has been reported that sugar palm has around 150 local names, indicating itsmultiple uses by the villagers. These names include Arenga pinnata, Areng palm,black fiber palm, gomuti palm, aren, irok, bagot, and kaong (Ticoalu et al., 2014;Sahari et al., 2012).

Sugar palm fiber, which known by local as ijuk fiber, is the fibers producedfrom a part of sugar palm tree, and one of the oldest cultivated plants in Asia shown inFigure 2.7. Geographically, the palm tree distributed in all of tropical South and South-east Asia countries, basically at humid area from India to Guam and from Myanmarto Nusa Tenggara Timur in Indonesia. Typically, it grows close to human settlementswhere anthropochoric breeding plays a major role.

Sugar palm is one of the most diverse multipurpose tree species in culture,which had widest range of use involving all part from root to the leaf (Sahari et al.,2012). Table 2.3 shows list the utilization of sugar palm as traditional source of income.The tree usually can reach the height of 15-20 m and 30-40 cm in diameter. Thelifespan of this tree around 12 to 20 years and the maturity of tree can be seen fromappearance of two short leaves at the top of stem. First flowering of the tree is at 10 to20 years but it can be early than that like 5 to 6 years (Ishak et al., 2012).

Figure 2.7: Sugar palm tree and sugar palm fiber (Sahari et al., 2012)

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Table 2.3: Uses of Arenga pinnata parts (Mogea et al., 1991; Ticoalu et al., 2014)

Part of Sugarpalm

Utilization

Root Tea to bladder stone, insectrepellent, post for pepper, board,

tool handles, water pipes, musicalinstrument like drum, and erosion

controlStem core Sago, fibers

Pitch of leafsrachis

Drinking cup

Young leaves Cigarette paper, saladsLeaflet midrib Broom, basket, meat skewers

Fruit Sap, wine, vinegar, palm sugarEndosperm of

unripeKalong kaling (cocktail)

Flower Source of nectarOld woody leaf

basesBiofuel

Timber Barrel, flooring and furnitureHair of base ofthe leaf sheaths

Fire ignition

2.2.4 Sugar palm fiber

One of the important parts of sugar palm tree is the fibers. Ijuk fiber, which is theother name of sugar palm fiber, can easily being obtained from the tree trunk sincethe fibers surround the trunk. The sugar palm fiber is strong, rigid, tough, waterproof,and high durability. Sugar palm is natural fibers of plant origin that consists of 51.54% celluloses, 15.88 % hemicelluloses, 43.09 % lignin, 8.9% water, and 2.54 % ash(Ticoalu et al., 2014) as shown in Table 2.4. For the application, it been used forfilters, component in road construction, basement of sport course and as shelters forfish breeding. The fibers is conventionally used for roofing material, as can be seen atsome Indonesian traditional houses, e.g. Batak, Toraja, Minahasa, Minangkabau, andBali temples (Ticoalu et al., 2011), which having good strength and durability whenexposed to certain environmental condition. The fibers also known to be seawater-resistant and can stand long as expose to either fresh or salt water.

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Table 2.4: Chemical composition of vegetable fiber (Ticoalu et al., 2014)

Fiber Alpha-cellulose

(%)

Hemi-cellulose

(%)

Lignin (%) Ash (%) Extracts(%)

Coir 36-43 0.2 41-45 - -Cotton 92-75 6 0.7-1.6 0.8-2 0.4Flax 62-71 16-18 2-2.5 1.5 6.0

Hemp 67-75 16-18 2.8-3.3 0.7 0.8Jute 49-71 12-13 11.8-12.9 0.7 0.5-2

Palmyra 41-52 11 42-43 4.1 -Sisal 60-57 10-15 8-12 0.55 -

Sugar-palm

50 7 45 9.5 3-7

Sugar-palm

(cellu-lose)

53.41 7.45 24.92 4.27 8.7

The characterization of single fibers from different morphological parts of thesugar palm tree has been done in research before (Sahari et al., 2012; Ticoalu et al.,2014). From the investigation it was found that the tensile strength of sugar palmwas 276.64 MPa, and the tensile modulus was 5.86 GPa. The elongation at break ofsugar palm was 22.3%, which was approximately the same as that of oil palm and coirfibers. For the chemical analysis it was shown that sugar palm has a high cellulosecontent of 52.29%. Cellulose was the main structural component, providing strengthand stability to the plant cell walls and the fibers. Generally, sugar palm can be used asreinforcement in composites owing to its higher tensile strength and cellulose contentin comparison with other established natural fibers such as kenaf, pineapple leaf, coir,and oil palm bunch as shown in Table 2.5. Table 2.6 shows the comparison betweenseveral natural fiber in their advantages and disadvantages for composite manufactur-ing.

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Table 2.5: Physical-mechanical of natural fiber (Bachtiar et al., 2010)

Naturalfiber

Density,g/cm3

Tensilestrength,

MPa

Youngmodulus,

GPa

Strain, % Diameter,µm

Bamboo 0.6-0.8 200.5 - 10.2 -Coir 1.25 138.7 6 10.5 396.98

Hemp 1.48 50-900 73 1.6 -Kenaf 1.4 215.4 13-17 1.18-1.31 -Jute 1.18 393-773 26.5 1.8 200

A. Pinnata 1.29 190.29 3.69 19.6 99-311*E-glass 2.55 1800-3000 72-83 3 8-14

Table 2.6: Advantages and disadvantages of different natural fiber

Types offiber

Advantages Disadvantages

Kenaf • Superior flexural strength• Excellent tensile strength• E = 8.12 Gpa(Ribot et al., 2011)

• Difficult to process(A.M Mohd Edeerazey et al.,2006)

Rise husk • Highly resistant to moisturepenetration and fungaldecomposition• E= 1.78-2.32 Gpa(Rahman et al., 2010)

• Handling of rice husk isdifficult because it is bulkyand dusty(Haefele et al., 2008)

Sugarpalm fiber

• durability and goodresistance to sea water• unaffected by heat andmoisture• E= 4421.8MPa(Sastra et al., 2005)

• Tree age effect themechanical properties offiber• sugar palm fiber havingmost moisture content ratherthan others part(J. Sahari et al., 2012)

Abacafiber

• More sustainable material• May control erosion inrainforest areas (planted withcoconut palm)• E = 8-20 Gpa(A.A.Mamun et al., 2013)

• Rapid moisture uptake,which can lead todimensional instability androtting.(A.A.Mamun et al., 2011)

2.3 Polymer Matrix

A matrix is a binder material that is used to hold fibers in position and transfer loads toan internal reinforcement, acts as medium for transmitting and distributing externally

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stress to reinforcement, protection from surface damage and acting as barrier to crackpropagation. It also can be defined as material that in a bulk and continuous phase thatsurrounds the reinforcement. A matrix material can be within all the materials classeslike polymer, metal and ceramic (Park & Seo, 2011). Each material that been use formatrix has its own advantages as shown in Table 2.7 (Kabir et al., 2012). For this study,polymeric matrices will be used together with natural fiber filler. The thermoplasticmaterials that currently dominate as matrices for natural fibers are polypropylene andpolyethylene, while thermoset, such as phenolics, epoxy and polyesters, are commonmatrices.

Table 2.7: Polymeric matrix (Kabir et al., 2012)

Polymer Advantages DisadvantagesThermoset -Low resin viscosity

-Good fiber wetting-Excellent thermalstability oncepolymerized-Chemical resistant

-Brittle-Non-recyclable viastandard technique-Not post-formable

Thermoplastic -Recyclable-Easy to repair bysolvent bonding-Post formable-Tough-Ductile

-Poor melt flow-Need to heated abovemelting point forprocessing purposes

A thermoplastic is from polymer materials that can be melted when heatedabove a specific temperature and solidify upon cooling time. In another words, it isrecyclable. Thermoplastic matrices might have few or no chemical crosslinks. Pro-cessing thermoplastic involved a heating to increase the temperature until solid statebecomes high viscosity liquids. Thus, the thermoplastic is more suitable polymers thatcan be used to reinforce with fiber due their form transformation phase during extru-sion process. Despite the disadvantages of thermoplastic compared to thermoset inmechanical properties, the material is recyclable, easy process, non-hazardous duringhandling process, effective in cost and provide better interfacial with cellulose fiber..In this research, poly-propylene had been chosen as the matrix for bind with the naturalfiber reinforcement.

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2.3.1 Polypropylene

Polypropylene (PP), which one of the polymer materials, is monomer unit in termsof molecules that been produced by polymerizing propylene. PP has the chemicalformula of C3H6. The polypropylene material known as economical material that offera combination of outstanding physical, chemical, mechanical, thermal and electricalproperties that cannot be found in another thermoplastic materials.

Generally, PP provides excellent resistant to organic solvent, decreasing agentand electrolysis effect. Evan the polymer has lower impact strength, it has superiorworking temperature and tensile strength. The PP comes with great advantages inproperties such as low density, high stiffness, heat resistance, chemical inertness, goodtransparency, good impact, stretchability, good hinge properties and recyclability. Be-sides that, it also an elastic and formable material which easy to process and high waterresistance.

Through the application, the PP were well known in various product which ap-plicable with properties provide by the polymer such as lightweight material, excellentdielectric properties, chemical resistant product, low moisture absorption, non-toxicand easy to fabricate.

Due to these advantages, many industries have chosen PP as their material suchas automotive, household goods, electrical application and even the aircraft compart-ment.

2.4 Potential Applications of Natural Fiber/PP Composite

As technology reaching the new era, the application of composite became more attrac-tive and new trend where the replacement for other’s materials (e.g. metal and ceramic)become common and the applications not only focusing on one field only. As for fiberreinforced polymer(FRP) composite, by having fiber such as glass, carbon and aramidwhich came with great material properties, the FRP composite was commonly used inaerospace, automotive, marine and construction industries (Joshi et al., 2004).

When natural fibers being introduce as reinforcement in polymer composite,the uses of synthetic fibers were getting slowly replace with natural fiber reinforcedpolymer (NFRP) composite. This was due to availability of the natural fiber besidesdisadvantages of synthetic fiber that high in cost, hazardous towards health and unsus-

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tainable (Fuqua et al., 2012; Wambua et al., 2003). In term of “green technology”, thethermoplastic polymer was getting more attention rather than thermoset since the char-acteristic of polymer which can be recycle thus implement one of element in “greentechnology”; recycling design. Therefore, natural fiber polypropylene based compos-ite has highest demand especially in application in automotive (finishing and interiordesign), building construction (panel), packaging and component with details as illus-trated in Figure 2.8 (Furqan et al., 2015; La Mantia & Morreale, 2011).

The demand on natural fiber PP based composite has been increase hence thePP based polymer can be processed into complex shaped component which give cleanand smooth finishing to the product. Moreover, the polymer has advantages to produceproduct that require precision and detail on each aspect of product; finishing product.Therefore, as for natural fiber, the most important parameter was the sizes of fiberwhich requires to has flexibility during process of composite, thus short fiber has per-form all the condition for the process. Besides that, the short fiber and PP polymerhave archived the requirement for standard thermo-plastic injection moulding equip-ment (Ibnabdeljalil & Curtin, 1997; Lin et al., 2008; Phoenix et al., 1997).

Figure 2.8: Potential application of natural fiber / PP polymer composite

2.5 Constituents Characteristic

In natural fiber-reinforced polymer, by having different chemical characteristics, thecomposites have a problem in the poor bonding between the cellulose fiber and thepolymer matrix (Pickering, 2008; Park & Seo, 2011; Nechwatal et al., 2003). This isdue to an opposite chemical nature between the highly hydrophilic property of cellu-

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lose fibers (on most of natural fiber) and the hydrophobic property of polymer matrix,which is associated with poor surface properties for association within the polymermatrix, and a degradation of mechanical properties.

The word ‘hydro’ comes from Greek meaning the water, while the ‘-philic’,from root of philia can be define as attraction or affinity to something, and the ‘-phobic’, from root of phobia meaning repelled or tendency to aggregate. Thus, thehydrophilic mean the material (refer to natural fiber) are attracted to water and tends toabsorb the moisture molecule, as the hydrophobic means the materials (refer to poly-mer) are seemingly repelled from the water and does not absorb the moisture. Fig-ure 2.9 show the differences between hydrophilic and hydrophobic material throughthe contact angle.

Figure 2.9: ’Hydrophilic’ vs. ’Hydrophobic’ contact angle

In the composite, the combination between hydrophilic and hydrophobic ma-terial contribute to poor mechanical properties of the composite. These due to poorinterface and bonding cause by different characteristic of material and create gaps(known as voids) in between of the interface. Besides, the hydrophilic materials havethe tendency to absorb moisture thus degrade the bonding and reduce the mechanicalproperties of the material.

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2.6 Surface Treatment

The surface treatment that can be done on the green composites can be divided intothree types which are the surface treatment by using chemical treatment, physical treat-ment and physic-chemical as shown in Figure 2.10. The main disadvantage with usingnatural fibers as the reinforcement is the week interfacial adhesion between the matrixand the fibers (Fuqua et al., 2012). The hydrophilicity of natural fiber makes weakbonding with hydrophobic material like polymers. Then, the treatment comes handyin helping to modify either matrix or reinforcement surface structure, and make themsuitable to having good bonding against each other.

By using the treatment, the properties of the composite also be enhance and in-crease compare to untreated composites. The example of chemical technique are silaneand alkaline treatment, which basically done on the reinforcement, while MAPP usu-ally used for the matrix treatment. For physical techniques there are corona dischargetreatment and solvent extraction, and for the physic-chemical treatment are hydrother-mal treatment and steam explosion.

Figure 2.10: Surface treatment (Fuqua et al., 2012)

In this research study, there were two types of surface treatment being approachwith three different mechanisms, which is the chemical surface treatment and physicalsurface treatment. These treatments were approached both constituents, either sugarpalm fiber reinforcement or PP polymer matrix.

2.6.1 Chemical surface treatment

To improve the properties of green composites, many researches had been done abouttreatment on composite. The chemical surface is the treatment that has been used in

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order to improve the bonding interface between natural fiber and matrix compositesand always had interest in research.

The examples of chemical treatment are alkalization, silane and permanganate(Li et al., 2007) as shown in Table 2.8. Besides that, there are several chemical treat-ment can be done for fiber-matrix composites such as acetylation treatment, benzoyla-tion treatment and the MAPP treatment (Kabir et al., 2012) as tabulated in Table 2.9.For this study, silane treatment and maleic anhydride (MA) treatment being applied toincrease the adhesion between matrix and reinforcement, thus enhance the interface ofcomposite.

Table 2.8: Chemical treatment on natural fiber (Li et al., 2007)

Treatment DescriptionsAlkaline treatment • Disruption of hydrogen bonding

in the network structure, increasingsurface roughness.• removes a certain amount oflignin, wax and oils covering theexternal surface, depolymerizescellulose and exposes short lengthcrystallite

Silane treatment • may reduce the number ofcellulose hydroxyl groups in thefiber– matrix interface• hydrocarbon chains restrain theswelling of the fiber by creating across-linked network due tocovalent bonding

Permanganatetreatment

• leads to the formation of celluloseradical through MnO3 – ionformation• hydrophilic tendency of fiberdecreased as the KMnO4concentrations increased

REFERENCES

Ali, A., Sanuddin, A. & Ezzeddin, S. (2010). The effect of aging on arenga pinnatafiber-reinforced epoxy composite. Materials & Design, 31(7), pp. 3550–3554.

Andic Cakir, o., Sarikanat, M., Tufekci, H.B., Demirci, C. & Erdogan, U.H.(2014). Physical and mechanical properties of randomly oriented coir fiber–cementitious composites. Composites Part B: Engineering, 61, pp. 49–54.

Arbelaiz, A., Fernandez, B., Ramos, J., Retegi, A., Llano-Ponte, R. & Mondragon,I. (2005). Mechanical properties of short flax fibre bundle/polypropylene com-posites: Influence of matrix/fibre modification, fibre content, water uptake andrecycling. Composites Science and Technology, 65(10), pp. 1582–1592.

Ashori, A. (2008). Wood–plastic composites as promising green-composites for auto-motive industries. Bioresource Technology, 99(11), pp. 4661–4667.

Azman, S.S. (2013). Influence of fiber volume fraction and vacuum pressure on flex-ural properties of sugar palm frond fiber reinforced polyester composites. Aus-tralian journal of basic and applied sciences, 7(4), pp. 318–322.

Azwa, Z., Yousif, B., Manalo, A. & Karunasena, W. (2013). A review on the degrad-ability of polymeric composites based on natural fibres. Materials & Design,47, pp. 424–442.

Bachtiar, D., Sapuan, S. & Hamdan, M. (2009). The influence of alkaline surface fibretreatment on the impact properties of sugar palm fibre-reinforced epoxy com-posites. Polymer-Plastics Technology and Engineering, 48(4), pp. 379–383.

Bachtiar, D., Sapuan, S., Zainudin, E.S., Khalina, A. & Dahlan, K. (2010). The ten-sile properties of single sugar palm (arenga pinnata) fibre. In: IOP ConferenceSeries: Materials Science and Engineering, volume 11, IOP Publishing, p.012012.

Bachtiar, D., Sapuan, S. & Hamdan, M.M. (2008). The effect of alkaline treatment on

87

88

tensile properties of sugar palm fibre reinforced epoxy composites. Materials& Design, 29(7), pp. 1285–1290.

Baillie, C. (2005). Green Composites: Polymer Composites and the Environment.Green Composites: Polymer Composites and the Environment, Taylor & Fran-cis, ISBN 9780849325762.

Bavan, S. & Kumar, M. (2011). Conceptual design features and eco-methods. In:ICORD 11: Proceedings of the 3rd International Conference on Research into

Design Engineering, Bangalore, India, 10.-12.01. 2011.

Bozaci, E., Sever, K., Demir, A., Seki, Y., Sarikanat, M. & Ozdogan, E. (2009). Effectof the atmospheric plasma treatment parameters on surface and mechanicalproperties of jute fabric. Fibers and Polymers, 10(6), pp. 781–786.

Cantero, G., Arbelaiz, A., Llano-Ponte, R. & Mondragon, I. (2003). Effects of fibretreatment on wettability and mechanical behaviour of flax/polypropylene com-posites. Composites science and technology, 63(9), pp. 1247–1254.

Chandramohan, D. & Marimuthu, D.K. (2011). Tensile and hardness tests on naturalfiber reinforced polymer composite material.

Cheung, H.Y., Ho, M.P., Lau, K.T., Cardona, F. & Hui, D. (2009). Natural fibre-reinforced composites for bioengineering and environmental engineering ap-plications. Composites Part B: Engineering, 40(7), pp. 655–663.

Coutinho, F.M. & Costa, T.H. (1999). Performance of polypropylene–wood fiber com-posites. Polymer Testing, 18(8), pp. 581–587.

Demir, H., Atikler, U., Balköse, D. & Tıhmınlıoğlu, F. (2006). The effect of fiber sur-face treatments on the tensile and water sorption properties of polypropylene–luffa fiber composites. Composites Part A: Applied Science and Manufactur-ing, 37(3), pp. 447–456.

Eichhorn, S., Baillie, C., Zafeiropoulos, N., Mwaikambo, L., Ansell, M., Dufresne,A., Entwistle, K., Herrera-Franco, P., Escamilla, G., Groom, L. et al. (2001).Review: current international research into cellulosic fibres and composites.Journal of materials Science, 36(9), pp. 2107–2131.

El-Sabbagh, A. (2014). Effect of coupling agent on natural fibre in natural fi-

89

bre/polypropylene composites on mechanical and thermal behaviour. Compos-ites Part B: Engineering, 57, pp. 126–135.

Fuqua, M.A., Huo, S. & Ulven, C.A. (2012). Natural fiber reinforced composites.Polymer Reviews, 52(3), pp. 259–320.

Furqan, A., Choi, H.S. & Park, M.K. (2015). A review: Natural fiber composites selec-tion in view of mechanical, light weight, and economic properties. Macromol.Mater. Eng., 300, pp. 10–24.

Gao, H., Xie, Y., Ou, R. & Wang, Q. (2012). Grafting effects of polypropy-lene/polyethylene blends with maleic anhydride on the properties of the result-ing wood–plastic composites. Composites Part A: Applied Science and Manu-facturing, 43(1), pp. 150–157.

Gibeop, N., Lee, D., Prasad, C.V., Toru, F., Kim, B.S. & Song, J.I. (2013). Effectof plasma treatment on mechanical properties of jute fiber/poly (lactic acid)biodegradable composites. Advanced Composite Materials, 22(6), pp. 389–399.

Ha, J., Kurniawan, D., Kim, B. & Song, J. (2011). Mechanical properties of plasmapolymerized cellulose fabric/polylactic acid. Korean Soc. Compos. Mater, 2,pp. 29–31.

Herrera-Franco, P. & Valadez-Gonzalez, A. (2005). A study of the mechanical proper-ties of short natural-fiber reinforced composites. Composites Part B: Engineer-ing, 36(8), pp. 597–608.

Ibnabdeljalil, M. & Curtin, W. (1997). Strength and reliability of fiber-reinforced com-posites: localized load-sharing and associated size effects. International Jour-nal of Solids and Structures, 34(21), pp. 2649–2668.

Ichazo, M., Albano, C., Gonzalez, J., Perera, R. & Candal, M. (2001). Polypropy-lene/wood flour composites: treatments and properties. Composite structures,54(2), pp. 207–214.

Ishak, M., Sapuan, S., Leman, Z., Rahman, M. & Anwar, U. (2012). Characteriza-tion of sugar palm (arenga pinnata) fibres. Journal of thermal analysis andcalorimetry, 109(2), pp. 981–989.

Ishak, M., Sapuan, S., Leman, Z., Rahman, M., Anwar, U. & Siregar, J. (2013).

90

Sugar palm (arenga pinnata): Its fibres, polymers and composites. Carbohy-drate polymers, 91(2), pp. 699–710.

Izani, M.N., Paridah, M., Anwar, U., Nor, M.M. & Hng, P. (2013). Effects of fibertreatment on morphology, tensile and thermogravimetric analysis of oil palmempty fruit bunches fibers. Composites Part B: Engineering, 45(1), pp. 1251–1257.

Joshi, S.V., Drzal, L., Mohanty, A. & Arora, S. (2004). Are natural fiber composites en-vironmentally superior to glass fiber reinforced composites? Composites PartA: Applied science and manufacturing, 35(3), pp. 371–376.

Kabir, M., Wang, H., Lau, K. & Cardona, F. (2012). Chemical treatments on plant-based natural fibre reinforced polymer composites: An overview. CompositesPart B: Engineering, 43(7), pp. 2883–2892.

Kafi, A.A., Magniez, K. & Fox, B.L. (2011). A surface-property relationship of atmo-spheric plasma treated jute composites. Composites science and technology,71(15), pp. 1692–1698.

Keener, T., Stuart, R. & Brown, T. (2004). Maleated coupling agents for natural fibrecomposites. Composites part A: applied science and manufacturing, 35(3), pp.357–362.

Khalid, M., Ali, S., Abdullah, L., Ratnam, C. & Choong, S.T. (2006). Effect of mappas coupling agent on the mechanical properties of palm fiber empty fruit bunchand cellulose polypropylene biocomposites. International Journal of Engineer-ing and Technology, 3(1), pp. 79–84.

Ku, H., Wang, H., Pattarachaiyakoop, N. & Trada, M. (2011). A review on the tensileproperties of natural fiber reinforced polymer composites. Composites Part B:Engineering, 42(4), pp. 856–873.

Kurniawan, D., Kim, B.S., Lee, H.Y. & Lim, J.Y. (2012). Atmospheric pressureglow discharge plasma polymerization for surface treatment on sized basaltfiber/polylactic acid composites. Composites Part B: Engineering, 43(3), pp.1010–1014.

Kurniawan, D., Kim, B.S., Lee, H.Y. & Lim, J.Y. (2013). Effects of repetitive pro-cessing, wood content, and coupling agent on the mechanical, thermal, and

91

water absorption properties of wood/polypropylene green composites. Journalof Adhesion Science and Technology, 27(12), pp. 1301–1312.

La Mantia, F. & Morreale, M. (2011). Green composites: A brief review. CompositesPart A: Applied Science and Manufacturing, 42(6), pp. 579–588.

Lee, S.G., Choi, S.S., Park, W.H. & Cho, D. (2003). Characterization of surface mod-ified flax fibers and their biocomposites with phb. In: Macromolecular sym-posia, volume 197, Wiley Online Library, pp. 089–100.

Leman, Z., Sapuan, S., Saifol, A., Maleque, M.A. & Ahmad, M. (2008). Moisture ab-sorption behavior of sugar palm fiber reinforced epoxy composites. Materials& Design, 29(8), pp. 1666–1670.

Li, X., Tabil, L.G. & Panigrahi, S. (2007). Chemical treatments of natural fiber for usein natural fiber-reinforced composites: a review. Journal of Polymers and theEnvironment, 15(1), pp. 25–33.

Lin, T., Jia, D., He, P., Wang, M. & Liang, D. (2008). Effects of fiber length on mechan-ical properties and fracture behavior of short carbon fiber reinforced geopoly-mer matrix composites. Materials Science and Engineering: A, 497(1), pp.181–185.

Mogea, J., Seibert, B. & Smits, W. (1991). Multipurpose palms: the sugar palm (arengapinnata (wurmb) merr.). Agroforestry Systems, 13(2), pp. 111–129.

Monteiro, S., Satyanarayana, K., Ferreira, A., Nascimento, D., Lopes, F., Silva, I.,Bevitori, A., Inacio, W., Bravo Neto, J. & Portela, T. (2010). Selection of highstrength natural fibers. Matéria (Rio de Janeiro), 15(4), pp. 488–505.

Nechwatal, A., Mieck, K.P. & Reußmann, T. (2003). Developments in the characteri-zation of natural fibre properties and in the use of natural fibres for composites.Composites Science and Technology, 63(9), pp. 1273–1279.

Owen, M.M. (2014). The effects of alkali treatment on he mechanical properties of jutefabric reinforced epoxy composites. International Jurnol of Fiber and textileResearch, 4(2), pp. 32–40.

Painter, P., Watzek, M. & Koenig, J. (1977). Fourier transform infra-red study ofpolypropylene. Polymer, 18(11), pp. 1169–1172.

92

Park, S. & Seo, M. (2011). Interface Science and Composites. Interface science andtechnology, Elsevier Academic Press, ISBN 9780123750495.

Phoenix, S., Ibnabdeljalil, M. & Hui, C.Y. (1997). Size effects in the distribution forstrength of brittle matrix fibrous composites. International Journal of Solidsand Structures, 34(5), pp. 545–568.

Pickering, K. (2008). Properties and Performance of Natural-Fibre Composites.Woodhead Publishing Series in Composites Science and Engineering, ElsevierScience, ISBN 9781845694593.

Qiu, W., Zhang, F., Endo, T. & Hirotsu, T. (2003). Preparation and characteristicsof composites of high-crystalline cellulose with polypropylene: Effects ofmaleated polypropylene and cellulose content. Journal of Applied Polymer Sci-ence, 87(2), pp. 337–345.

Redzuan, N. (2012). Mechanical properties of cellulose fabric/polylactic acid compos-ites: effect of silane coupling agent and atmospheric plasma polymerization.

Rowell, R. (2005). Handbook of Wood Chemistry and Wood Composites. CRC Press,ISBN 9780203492437.

Sahari, J., Sapuan, S., Zainudin, E., Maleque, M. et al. (2012). Sugar palm tree: aversatile plant and novel source for biofibres, biomatrices, and biocomposites.Polymers from Renewable Resources, 3(2), p. 61.

Saheb, D.N., Jog, J. et al. (1999). Natural fiber polymer composites: a review. Ad-vances in polymer technology, 18(4), pp. 351–363.

Seki, Y., Sarikanat, M., Sever, K., Erden, S. & Gulec, H.A. (2010). Effect of the lowand radio frequency oxygen plasma treatment of jute fiber on mechanical prop-erties of jute fiber/polyester composite. Fibers and Polymers, 11(8), pp. 1159–1164.

Ticoalu, A., Aravinthan, T. & Cardona, F. (2011). Experimental investigation intogomuti fibres/polyester composites. Incorporating sustainable practice in me-chanics of structures and materials.

Ticoalu, A., Aravinthan, T. & Cardona, F. (2014). A study into the characteristics ofgomuti (arenga pinnata) fibre for usage as natural fibre composites. Journal ofReinforced Plastics and Composites, 33(2), pp. 179–192.

93

Wambua, P., Ivens, J. & Verpoest, I. (2003). Natural fibres: can they replace glass infibre reinforced plastics? composites science and technology, 63(9), pp. 1259–1264.

Xie, Y., Hill, C.A., Xiao, Z., Militz, H. & Mai, C. (2010). Silane coupling agents usedfor natural fiber/polymer composites: A reviewxie2010. Composites Part A:Applied Science and Manufacturing, 41(7), pp. 806–819.

Yuan, X., Jayaraman, K. & Bhattacharyya, D. (2004). Effects of plasma treatment inenhancing the performance of woodfibre-polypropylene composites. Compos-ites Part A: Applied Science and Manufacturing, 35(12), pp. 1363–1374.

Zaman, I., Ismail, A.E., Awang, M.K. et al. (2011). Influence of fiber volume fractionon the tensile properties and dynamic characteristics of coconut fiber reinforcedcomposite. Journal of Science and Technology, 1(1).

Zaman, I., Manshoor, B., Khalid, A., Meng, Q. & Araby, S. (2014). Interface mod-ification of clay and graphene platelets reinforced epoxy nanocomposites: acomparative study. Journal of Materials Science, 49(17), pp. 5856–5865.