Mechanical properties of kenaf fibre reinforced ...

Construction and Building Materials 76 (2015) 87–96

Contents lists available at ScienceDirect

Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

Review

Mechanical properties of kenaf fibre reinforced polymer composite: A review N. Saba a, M.T. Paridah a, M. Jawaid a,b,⇑ a b

Department of Biocomposite Technology, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia Chemical Engineering Department, College of Engineering, King Saud University, Riyadh, Saudi Arabia

h i g h l i g h t s Kenaf fibres regarded as potential materials for polymer composite based industries. Mechanical properties of kenaf fibre composite comparable to glass fibre composite. Kenaf composites nowadays used as construction materials for different buildings.

a r t i c l e

i n f o

Article history: Received 2 July 2014 Received in revised form 5 November 2014 Accepted 18 November 2014

Keywords: Kenaf fibre Thermoplastic polymer Thermoset polymer Mechanical properties Construction materials

a b s t r a c t Kenaf regarded as an industrial crop in Malaysia and also grown commercially in other part of world for different applications. It is certainly one of the important plants cultivated for natural fibres globally, next to cotton, which is endemic to ancient Africa. It has great potential to use as automotive and construction materials due its long fibres derived from outer fibrous bark, the bast. Natural fibres such as kenaf getting attention of researchers and industries to utilize it in different polymer composites based products due to environmental awareness of consumers and government regulation in some countries. In many research studies, kenaf fibres are reinforced with polymer matrix to form fibre reinforced polymeric composites which perfectly improve the features of the polymers. Mechanical properties of kenaf fibres is comparable to existing materials and it will play an important role to utilize as the material of choice for a varied range of structural and non-structural industrial products with polymer matrix. The innumerable properties of kenaf fibres in original and reprocessed plastics are demonstrated by many recent studies and research efforts make it suitable construction materials (such as boards of different densities, breadths, along with fire and insect resistance). In this review work, we try to explore and highlights the previous work involving mechanical properties of kenaf fibre reinforced polymer composites to provide a perfect source of literature for doing further research in this topic to explore it as construction and building materials. Ó 2014 Elsevier Ltd. All rights reserved.

Contents 1. 2. 3. 4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kenaf fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factors effecting mechanical properties of natural fibre and kenaf reinforced polymer composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanical properties of kenaf fibres composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Kenaf based thermoset composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Kenaf based thermoplastic composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Kenaf based biodegradable polymer composites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Effect of fibre treatment and coupling agents on mechanical properties of kenaf composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

88 88 89 90 91 92 92 92

⇑ Corresponding author at: Department of Biocomposite Technology, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. Tel.: +60 3 89466960; fax: +60 3 89471896. E-mail address: [email protected] (M. Jawaid). http://dx.doi.org/10.1016/j.conbuildmat.2014.11.043 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved.

88

5. 6.

N. Saba et al. / Construction and Building Materials 76 (2015) 87–96

Hybrid composites . Conclusion . . . . . . . Acknowledgments . References . . . . . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

1. Introduction FRP usually referred to as fibre reinforced polymer composite is a quite new material in the various applications such as construction and building industry compared to concrete and steel [1]. Composites possess the desired and preferred properties by coalescing dissimilar constituents in a cautious and judicious way. Generally they possess higher specific modulus and high specific strength enabling them as a valuable material in huge number of industrialized requests which requires such features [2]. Carbon fibres and glass fibres integrated in polyester resin are the traditional and conventional fibre reinforced composite materials. These composite materials have excellent mechanical properties but these materials cause environmental pollution due to the non-degradability of fibres [3]. Natural fibre reinforced composites found to be an alternative solution to the ever depleting petroleum sources thus they receive greater attention, attraction from research scientist and community. Manufacturer and scientists attracted towards natural fibre based composites due to its biodegradability, light in weight, nontoxic and relatively stronger and consider being virtuous products which can be use in construction industry, automotive industry and for furniture production [4]. Natural fibre composites have better formability, abundant, renewable, cost effective, possess tool wearing rates, thermal insulation properties, acoustic properties, sufficient energy requirements and safer towards health [5]. Many innumerable demerits such as hydrophilic in nature, poor fibre/matrix interfacial adhesion and poor thermal stability of natural fibres can be overcome by chemical treatment or compatibilizer which amended the adhesion between the fibre and matrix. Composite of polymers and kenaf fibre possess the variances and incomparability in terms of their polarity structures [6]. Based on the origin natural fibres are categorized as animal based and plant based. Animal-based fibres are wool, silk, etc. and natural fibres based on plant includes sisal, coir, ramie, jute, bamboo, pineapple and many more [2]. Lignocellulosic fibres possess many compensations of being financially reasonable to manufacture such as lightweight, eco-friendly, harmless to health, high stiffness and specific strength which provides a probable substitute to the synthetic or artificial fibre [7,8]. The reinforcing capability of the fibres mainly influenced by various aspects such as polarity of the fibre, mechanical strength of the fibres, surface appearances, and existence of reactive centres [9]. Moreover many of the natural fibres properties are governed by several factors such as climate, harvest, maturity, variety, decortications, retting degree, disintegration (steam explosion treatment, mechanical), fibre modification, technical and also textile processes (spinning and carding) [9]. In spite of these promising features shown by natural fibres certain major drawbacks are also underlined like water absorption, strength degradation, lack in thermal stability lowered impact properties [10,11] but it has been found that these can be improved and overcome by hybridization with either natural or synthetic fibre. Bast fibres derived from natural fibres such as hemp, flax, kenaf and jute have high specific strength, low density and are extremely concerned in several industrial applications [12]. Kenaf fibres are gratifying increasingly widespread throughout the world and even in Malaysia as the significant natural materials source contributing towards the development of eco-friendly assets for the automotive, sports industries, food packaging and furniture [13], textiles, paper pulp,

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

94 94 95 95

and fibreboards based industries [14]. Inferior thermal resistance are displayed by kenaf as compared to artificial or synthetic fibres such as (aramid, glass fibres) like all other natural fibres [1]. Kenaf is in an advantageous position when compared with other lignocellulosic fibre crops since it has a short plantation cycle, flexibility to environmental conditions and requires relatively lowered quantity of pesticides and herbicides [15]. Kenaf fibres receive much attention owing to its prospective probability as polymer reinforcements in the natural fibre composite industry. Researchers claimed that mechanical strength and thermal properties of kenaf composite are superior to other type of natural fibre polymer composites, thus regarded as a suitable applicant for high-performance natural fibre polymer composites [14]. The kenaf fibre as reinforcement materials are full-fledged noticeably from the past decade along with other products such as extruded plastic fencing, decking, and furniture padding [3]. Kenaf composites can eventually, supplement and substitute petroleum based composite materials in many of the known industrial applications, and thus proposing innovative environmental, agricultural, manufacturing and consumer profits formulation methods [16,17].

2. Kenaf fibre Kenaf is comparatively commercially available and economically cheap amongst other natural fibre reinforcing material. Customarily kenaf denoted as industrial kenaf due to of its great interest for the production of industrial raw materials. Kenaf fibre belongs to species of Hibiscus cannabinus where genus is Hibiscus and family Malvaceae obtained from stems of plants [18] which also includes cotton (Gossypium spp.) and okra (Abelmoschus esculentus L. Moench). Kenaf is wild dicotyledons plant of subtropical and tropical parts of Africa and Asia. The word kenaf is of Persian origin explaining the plant having short day, warm season and annually herbaceous plant, with the average diameter of fibre is 67.6 lm [19]. Kenaf is a hardy, strong and tough plant with a fibrous stalk, resistant to insect damage and requires relatively fewer amount of or no pesticides [20]. Fig. 1 showing the kenaf plantation and fibre. Kenaf is compliant to several types of soils and to grow effectively, need only nominal chemical treatment, characteristically some fertilizer and a single herbicide treatment [20]. The three types of fibre: bast, core, and pith constitutes the kenaf plant [21]. However, kenaf is characterized by two distinct fibres bast and core comprising 35% and 65% respectively [22]. The bark and core fibre, considered as two distinct types of raw material that can be distinguished by their chemical composition anatomical appearances [21]. The pith comprises entirely of parenchymatous cells, which are polygonal in shape not typically prismatic [23]. According to researchers, the kenaf bast fibres possess striking mechanical properties that make them as a replacements to glass fibres in polymer composites as reinforcing elements [23,24]. Fibre length, fibre content, and fibre orientation of kenaf fibre affects physical and mechanical properties of kenaf fibre reinforced soy based biocomposites [25]. Transmission electron microscopy is better tool to investigate cell wall ultrastructure and morphology of kenaf fibres [22]. Figs. 2 and 3 illustrate transverse sections of kenaf cell wall fibres composed of intercellular layers (primary and secondary wall-S1, S2, S3) and its core fibres


89

Fig. 1. Typical images of (A) kenaf plantation and (B) kenaf fibre.

Fig. 2. Transmission electron micrograph of ultra-thin section of kenaf fibres: (A) kenaf core fibres showing cell wall and lumen; (B) transverse section of core fibres; (C) transverse section of kenaf bast fibres. Cell wall structure stained with uranyl acetate and lead citrate. Scale bars = 5000 nm in (A and C); 2000 nm in (B): CW: cell wall; L: lumen; F: fibre; P: parenchyma, with permission [22].

showed great variability in size, shape, and structure of the cell wall fibres [22]. Table 1 shows the results of density and mechanical properties of kenaf fibres reported by different researcher [19]. It clears from Table 1 that they are not identical values obtained by different researchers because of the variation in types of kenaf fibres used in terms of the place of origin, initial retting method and many other related factors. Table 2 illustrates comparison of mechanical properties of kenaf with other natural fibre. Kenaf fibre extensively being used in engineering fields, as fibre in fibre reinforced polymer composite sector [19]. Kenaf exhibits many salient features like low feedstock, high biomass content, and negligible pesticides requirement along with low, crop rotation. The prime benefits of the crop rotation by the kenaf is the contribution towards the weeds control, resistant to drought and add diversity to the dry land, and the control of soybean nematode. Kenaf fibres displayed improved and attractive properties in polymeric composites as reinforcement materials beneath flexural loading circumstances in comparison to the related type of others natural fibres. Thereby generating a probability of substituting the artificial (synthetic)

fibres such as glass and aramid with kenaf fibres for flexural structural and non-structural applications [26].

3. Factors effecting mechanical properties of natural fibre and kenaf reinforced polymer composites The major constituents of natural fibres are cellulose and lignin. The cellulose content responsible to provide the mechanical properties which in turn depend on numerous aspects such as fibre length, fibre loading or volume fraction of fibres, fibre aspect ratio, fibre orientation or inter facial adhesion between fibre-matrix [6]. Natural fibre composites mechanical properties extremely influenced by the matrix-fibre adhesion property between the polymer matrix and fibres are been reported by many researchers [27–29]. In natural fibre composites, pretreatment frequently showed very fine perfection in mechanical and tensile properties due to the improved interfacial linkage or fibre-matrix adhesion. It reported that the effect of fibre loading on the biocomposite tensile and flexural properties (mechanical properties) are inten-

90


Fig. 3. Transmission electron micrograph of ultra-thin section of kenaf fibres: (A and B) transverse section of a multi-layered fibre wall at low and high magnification, respectively, in core fibres; (C) transverse section of bast fibres. Scale bars = 2000 nm in (A and C); 1000 nm in (B): ML: middle lamella; CML: compound middle lamella; P: primary wall; S1, S2, and S3: secondary wall sub-layers; L: lumen, with permission [22].

Table 1 Density and mechanical properties of kenaf fibre reported by researchers, with permission [19]. Density (g/ cm3)

Tensile strength (MPa)

Tensile modulus (GPa)

Elongation (%)

– – 1.45 1.4 1.5 0.75 0.6 0.749 1.2

692 930 930 284–800 350–600 400–550 – 223–624 295

10.94 53 53 21–60 40 – – 11–14.5 –

4.3 1.6 1.6 1.6 2.5–3.5 – – 2.7–5.7 3–10

Table 2 Mechanical properties of some natural and synthetic fibre, with permission [19]. Fibre

Density (g/cm3)

Tensile strength (MPa)

Elastic modulus (GPa)

Elongation at break (%)

Jute Sisal Flax Hemp Pineapple Cotton Kenaf E-glass Carbon

1.3 1.5 1.5 1.47 1.56 1.5–1.6 1.45 2.55 1.4

393–773 511–635 500–1500 690 170–1627 400 930 3400 4000

26.5 9.4–22 27.6 70 60–82 5.5–12 53 71 230–240

1.5–1.8 2.0–2.5 2.7–3.2 2.0–4.0 2.4 7.0–8.0 1.6 3.4 1.4–1.8

sely depended on the kenaf fibre loading [30]. Further, effects of fibre size, fibre loading and fibre/matrix adhesion on composite strength, toughness and stiffness of a variety of particulate composites having both nano-and micro-fillers with small aspect ratios are reasonably significant. The resulting composite toughness and strength are strongly determined by all three factors, chiefly by particle/matrix adhesion [31]. It’s because mechanical strength rest on effective stress transfer between filler and matrix, and brittleness/toughness is governed by adhesion [31]. Moreover aspect ratio significantly affects the mechanical properties of hybrid composites, because high aspect ratio effectively transfers stress to

matrix [32]. Researcher work also finds that aspects resembling the processing conditions/techniques have remarkable consequence on the mechanical properties of fibre reinforced composites [33]. Chemical or pretreatment methods of the fibre chemically modify the surface, clean the fibre surface, reduced the moisture absorption process and upsurge the surface unevenness [34]. Some of the important industrial methods that are currently employed includes the mercerization, acetylation, etherification, peroxide treatment, benzoylation, graft copolymerization, acrylation, maleic anhydride, titanate treatment, permanganate treatment, sodium chlorite treatment, plasma, isocyanate treatment and use of coupling agent such as silane treatment used for natural fibres [9] to improve fibre/matrix interfacial bonding in composites. The effectiveness of the composites reinforced by natural fibres relies on the fibre-polymer matrix interface and its tendency of transferable stress to the fibre from the matrix. The foremost hindrances is the deficiency of perfect interfacial adhesion, inherently high moisture absorption or poor resistance to moisture absorption and low melting point leading to micro cracking of the composite. Thus leads to the deprivation of mechanical properties thereby making the less attractive use of natural fibre reinforced composites [34]. 4. Mechanical properties of kenaf fibres composites Few researchers reported review on kenaf fibres, its properties and mechanical properties of kenaf fibres reinforced polymer composites but these review paper deals very limited information on mechanical properties of kenaf fibres reinforced polymer composites until 2011 [35–37]. However, Present review covers more comprehensive details on mechanical properties of kenaf composites and concentrated it to cover latest work on mechanical properties of Kenaf fibre reinforced polymer composites with up to date information until 2014. Among other natural fibres, kenaf fibres displayed better and superior properties for reinforcement in composites of different polymeric matrix under varied flexural loading conditions. Table 3 illustrated list of recent work made by the different researcher on the kenaf fibre reinforced polymeric (thermoset or thermoplastic resin or biodegradable) composite

91

N. Saba et al. / Construction and Building Materials 76 (2015) 87–96 Table 3 Reported work on kenaf fibres based composites. Reinforcement

Matrix

Refs.

Kenaf fibre Treated and untreated kenaf Kenaf fibre Kenaf/fibre glass Short fibre non-woven kenaf Long kenaf/woven glass Kenaf bast fibre Kenaf-fibre Kenaf fibres Kenaf Kenaf–glass Kenaf fibre and corn husk flour Nonwoven kenaf Kenaf fibre Alkali treated kenaf fibre Kenaf fibre Kenaf fibres Kenaf/glass Kenaf/glass Kenaf sheets Kenaf fibre Woven kenaf fibre Pultruded treated and untreated kenaf fibre Kenaf fibre Kenaf fibre Chemically treated kenaf fibre Unidirectional kenaf fibre Treated and untreated kenaf fibre Kenaf fibres and exfoliated graphite nanoplatelets Kenaf fibre (KF) and bacterial cellulose Treated and untreated kenaf fibre Non woven kenaf fibre Kenaf fibre Kenaf fibre Kenaf fibre Kenaf fibre Kenaf fibre Kenaf fibre Kenaf fibre Kenaf fibres Pultruded kenaf fibre Treated banana/kenaf fibres PALF and kenaf fibre Kenaf fibre

HDPE Epoxy Poly(furfuryl alcohol) bioresin Polyester Polypropylene Unsaturated polyester (PP)blended with (TPNR) and (PP/EPDM) Polyurethane Polylactide Poly (lactic acid) Unsaturated polyester Poly (lactic acid) Polypropylene Polypropylene Poly (lactic acid) Waste polypropylene Cassava starch Epoxy polybutylene terephthalate (PBT) Epoxy PLLA Polypropylene Polyoxymethylene (POM) Polyester Natural rubber Polystyrene (PS) Thermoplastic polyurethane Epoxy Unsaturated polyester (UPE) Polylactic acid PLA resin Epoxy resin Polypropylene Poly (vinyl chloride)/thermoplastic polyurethane poly-blend Thermoplastic polyurethane HDPE Polypropylene (PP) Concrete Epoxy Polypropylene HDPE and PP Unsaturated polyester Polyester HDPE PHBV and PBAT

[38] [26] [39] [40] [41] [18] [13] [42] [43] [29] [44] [30] [45] [46] [47] [48] [49] [50] [5] [14] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [38] [65] [66] [67] [68] [69] [70] [3] [71] [72]

Note: Polypropylene (PP); thermoplastic natural rubber (TPNR); polypropylene/ethylene–propylene–diene–monomer (PP/EPDM); high density polyethylene (HDPE); poly-Llactic acid (PLLA); poly (lactic acid) (PLA); polystyrene (PS); polyoxymethylene (POM); thermoplastic polyurethane (TPU); polypropylene (PP) thermoplastic natural rubber (TPNR); polypropylene/ethylene–propylene–diene–monomer (PP/EPDM); poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV); poly (butylenes adipate-co-terephthalate) (PBAT); unsaturated polyester (UP).

and also its hybrid composite. Researcher reported that mechanical properties of kenaf fibre reinforced composites vary because of the different testing methods used and the samples tested [6].

Table 4 Effect of fibre loading on the tensile properties of kenaf fibre reinforced unsaturated polyester resin (UPR) composites [71]. Sample type

4.1. Kenaf based thermoset composites A lot of research work also been done with the kenaf reinforced thermoset composites. Researchers revealed that treated kenaf fibres reinforced in epoxy improved the flexural strength by about 36% of the composite while, without treated fibres shows only 20% enhancement [26]. Owing to strong adhesion at the interface of the fibres through chemical treatment and the permeability of the composites shows to inhibited the detachments, debonding or pull out of fibres [26]. In other interesting study made by researcher [71,29] also illustrates that with the increase in fibre volume of unidirectional kenaf fibres in kenaf/epoxy composite, manufactured through hand Lay-up process following the ASTM D-3039 standard. The tensile properties such as tensile strength and modulus of elasticity also show considerable increases. Table 4 illustrated tensile strength, tensile strain, and the modulus of elasticity which get improved as the volume fraction of the fibre

Tensile strength at break, MPa Tensile strain at break, % Modulus of elasticity, GPa

Kenaf fibre volume fraction Neat

15%

45%

32.19 3.40 1.78

57.95 2.11 3.96

100.53 1.90 7.76

increases. The tensile strength at the break for the neat epoxy composites scored around 30 MPa. By adding 15% fibre volume fraction, the strength of the composites almost hit 60 MPa. The trend continued to increase up to 100 MPa with a fibre content of 45% [73]. The unidirectional kenaf fibre reinforced epoxy composites are fabricated through hand-layout technique [57], showing higher disintegration rates and load carrying capacity by composites having higher fibre content without presenting any significant progress at very high number of cycles. Indicating that fibre content ratios affect fatigue life [57]. According to another study the loading rate and temperature also influenced the tensile (mechanical) properties of kenaf bast

92


fibre-reinforced epoxy strands or composites and kenaf bast fibre bundles (KBFB). Nearly 50 wt.% epoxy and 50 wt.% of KBFB comprised the KBFB epoxy composite strand [67]. The tensile strength, elastic modulus as well as failure strains of KBFBs, showed large distribution statistically ranging from 10% to 30% [67]. As the loading rate increases tensile strength increases gradually, while the tensile modulus virtually remains unchanged. Research also clarify that during fibre treating or handling and fabricating composite technique executing at high temperatures (170–180 °C), with the duration less than 1-h, does not impose noteworthy changes on the tensile properties of KBFBs [67]. Researcher evaluated effect of polybutylene terephthalate (PBT) on impact property of kenaf/ glass epoxy hybrid composites and obtained results indicated that there is no effect of PBT on impact properties of developed materials [50]. 4.2. Kenaf based thermoplastic composites According to another interesting work, the effect of fabrication technique or conditions on the mechanical properties are studied for the kenaf/polypropylene nonwoven composites (KPNCs), with 50/50 blend ratio by weight [45]. Researchers found that flexural modulus of the kenaf and polypropylene (PP) composite influenced by number of kenaf layers, heating time and kenaf weight fraction prepared by pressing [46]. The maximum flexural modulus of the composite optimized kenaf weight fraction, which increased with increase of the bulk density [46]. Another study elaborated that higher porous composites can be achieved through lesser kenaf loading and results lower shear resistance this also influenced the density in the case of kenaf-fibre polyurethane composite [42]. Research work shows that only 30% fibre loading are sufficient for the kenaf–PP composite having mechanical properties favorably similar to most widely used 40% fibre by weight flax and hemp reinforced polypropylene composites prepared by same compression moulded technique [68]. Researcher studied the effects of extrusion processing temperature on the various properties of kenaf fibre/high-density polyethylene (HDPE) composites to conclude its best performance of thermo-mechanical and tensile properties for low (LPT) and (HPT) high processing temperatures [38]. Processing at high temperature improved the tensile modulus of composites but displayed diminished properties when processed at low processing temperature especially at high fibre content. At both low and high processing temperatures, the tensile strain and strength of the composite increased with decreasing fibre content [38]. According to researchers [54] elongation at break and tensile strength progressively decreases with an increase in the fibre loadings. Further this work also realized that 10 phr is the requirement for the finest enactment of the optimum fibre loading in composite. It reported that at higher temperature (230 °C) for shorter time (60 s) possess the best mechanical properties of nonwoven kenaf/PP composites produced by carding and needle-punching techniques with 50/50 blend ratio by weight [62]. Researchers demonstrated the influence of fibre content on mechanical properties of kenaf fibres reinforced poly (vinyl chloride)/thermoplastic polyurethane poly-blend (PVC/TPU/KF) composites [63]. The tensile strength, impact strength and tensile strain decrease while tensile modulus increases with upsurge in fibre content. Furthermore high impact strength observed with 40% fibre content. Another study found that tensile strength of kenaf fibre thermoplastic polyurethane (TPU) composite dropped to 16.14 MPa after 80 days of soil burial test [64]. Moreover this soil buried composite also shows no visible variation in flexural properties. Researchers [38] demonstrated that kenaf fibre/HDPE composite on processing at low temperature shows reduced tensile properties while processing at high temperature displayed improved tensile properties of composites [42]. While at both high

and low processing temperatures, the strain and tensile strength of the composite reduces by amplifying fibre content [38]. Another work found that processing parameters, comprising speed and temperature, possess a pronounced effect on the mechanical properties of kenaf fibre polypropylene (PP) plastic composite fabricated by compression moulding [65] Research result cleared that tensile properties of PP/kenaf composite get amplified by 10% subsequently by the adding unidirectional kenaf fibre (UKF). Researchers experimental research shows that mechanical properties of a natural fibre reinforced concrete (FRC) comprised of kenaf bast fibres [66]. Results indicating that the mechanical properties including compressive modulus and strength, modulus of rupture and splitting tensile strength of plain concrete control specimens are quite similar and analogous to kenaf fibre reinforced concrete (KFRC). 4.3. Kenaf based biodegradable polymer composites The researcher observed large mechanical anisotropies displayed by kenaf sheets using poly-L-lactic acid (PLLA) resin providing high mechanical performance in Young’s modulus and tensile strength [14]. Another research work concluded that tensile, elastic moduli and flexural strength of the kenaf fibre-reinforced composites amplified smoothly and linearly with the fibre content of 50% at the 160 °C and found to possess highest fabrication temperature without affecting fibre strength [29]. In other research work, found that extrusion process of kenaf fibre and corn husk flour poly (lactic acid) composite preliminary values of aspect ratio before and after extrusion did not shows considerable difference between theoretical and experimental values of the tensile modulus [30]. According to researchers, 25–30% micro-size reinforcements of kenaf fibres and 5 wt.% exfoliated graphite nano platelets (xGnP) in poly (lactic acid) based composites prepared by injection moulding shows increased in the mechanical properties [59]. In other study, bacterial cellulose (BC) when employed to reinforce Kenaf fibre (KF) in the PLA resin matrix greatly enhanced the mechanical property by increasing interfacial area using low amount of nanocellulose prepared through extrusion method thus generate the sustainable biocomposites [60]. Manufactured all green composite involving only 20% kenaf fibre and poly (furfuryl alcohol) bioresin as shown in Fig. 4 and found a considerable improvement in the mechanical properties. Results shows the significant increase in storage modulus (123%), tensile strength (310%) and flexural strength (48%) in poly (furfuryl alcohol)/kenaf composite mainly because of void-free compact structure and superior matrix interfacial fibre interactions [39]. 4.4. Effect of fibre treatment and coupling agents on mechanical properties of kenaf composites Several studies and research work established that the chemically treated kenaf fibre significantly has improved mechanical properties with respect to untreated kenaf fibre. Researcher also suggested an improvement in impact strength, flexural, tensile and also on the stiffness of the kenaf fibres reinforced composites by using several types of polymers [13]. Research study suggested, the mechanisms that enhanced the interfacial adhesion between kenaf-UPE composites by employing 1,6-diisocyanato-hexane (DIH) and 2-hydroxylethyl acrylate (HEA) treated kenaf fibre in kenaf-UPE composites [58]. Thus, chemically surface treatments considerably improved the modulus of elasticity, modulus of rupture, tensile strength of the formulated kenaf-UPE composites [58]. The pronounced effects of alkali treatment of the fibre on the composite properties are explored fabricated by hand layup method. The highest impact strength shown by 40% kenaf fibre


93

Fig. 4. Preparation of all green composite from kenaf fibre and poly (furfuryl alcohol) bioresin, with permission [37]. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

reinforced epoxy composites by weight fraction which get further increased by 14.3% after alkali treatment [61]. Another study illustrated that interfacial adhesion between the fibres and matrix directly affects the tensile properties of natural fibre reinforce polymers (both thermoplastics and thermosets) [74]. Moreover, increasing the fibre content also leads to increase in Young’s modulus and tensile properties up to certain maximum value of the natural fibre polymer composites. Treatment of kenaf fibres with chemical like 6% NaOH (alkalization), Sodium Laulryl Sulfate (SLS) treatment for both the woven hybrid and random mix composite improved the mechanical properties because the permeability of the treated kenaf fibres/epoxy composite [3]. Researchers found that the alkalization treatment with sodium hydroxide improved the mechanical properties of the kenaf fibre knowingly compared to untreated kenaf fibre with optimum value of concentration only 6% NaOH showing good results for the chemical treatment methods [34]. Moreover, the tensile strength of kenaf fibre increased by decreasing the NaOH solution immersion time and concentration rate [19]. Treatment of kenaf fibres with 6% NaOH, splitted the kenaf fibre bundles into fine fibres resulting in the permissible entrance of the epoxy resin which pierce in the fibre bundles causing to high intertwining of the fibres in the matrix thus leads to greater interfacial adhesion [26]. Researchers reported that flexural and viscoelastic properties of kenaf/PP composites enhanced by modification of kenaf nonwoven by zein coating(coupling agent) [51]. The nonwovens treated kenaf–polypropylene composites has favourable and better properties compared to untreated composite prepared by same compression moulding. Further Researcher revealed the effect of coupling agent-acrylic acid (AA), and cross-linker divinylbenzene (DVB) on the mechanical properties of kenaf fibre (KF) reinforced waste polypropylene (rPP) biocomposite [48]. Moreover, the addition of coupling agent MAPP (maleic anhydride polypropylene) to the kenaf–PP composite yields higher specific modulus than coir, sisal and even E-glass [68]. Another work reveals that substantial improvement observed in the flexural and tensile properties of short fibre nonwoven kenaf polypropylene composites by alkali– silane treatment as compared to treated one only with sodium

hydroxide solution and the untreated [41]. Moreover, the flexural strengths and specific tensile of alkali–silane treated kenaf composites with 30% fibre mass fraction are, respectively, only 11% and 4% lesser than glass fibre composites [41]. Some researcher revealed that tensile strength of the PP/EPDM composite significantly increased by approximately 81% while only 55% increment attained in TPNR–KF–MAPP by the kenaf fibre (KF) and MAPP with respect to unreinforced TPNR [13]. The impact strength and flexural properties also shows considerably improvement for treated kenaf fibre composite. Thus, kenaf fibre has conveyed its tensile strength to the PP/EPDM system through worthy interaction supported by the compatibilizer agent. The fibre and matrix surface get compatibilized by the presence of maleic anhydride thus amplifying the value of mechanical properties very significantly [13]. Work reported that kenaf fibres compounded with high-density polyethylene (PE) and polypropylene (PP) polymers along with the MAPP (maleated polypropylenes) and maleated polyethylene (MAPE) as coupling agent on alkalization with only 6% NaOH shows increment in properties [69]. The treatment and MAPP and MAPE contribute towards the increment of untreated and treated composites tensile strength, elastic modulus also shows considerable improvement in the matrix-filler adhesion. Explored that the weaker transference of load between fibre and matrix occurred due to the poor interfacial adhesion causing lowering in the mechanical properties [52]. In other work, researchers reported that untreated pultruded kenaf reinforced composites (UTPKRC) possess lesser flexural and tensile properties compared to those of 6% concentration NaOH treated pultruded kenaf reinforced composites (TPKRC) [53]. In another study, Researchers concluded that impact and flexural tests shows accentuated benefits by chemical modifications as a consequence of an improved interface at the fibre-matrix which is reliant on the polymeric matrix nature [72]. In another research work, it also found that the reinforced composites utilizing modified kenaf fibre by polymeric silane coupling agent (CA) exhibited superior mechanical properties equated with unmodified Kenaf fibre reinforced polystyrene (PS) composites [55]. Thus, the process ability and the properties of kenaf fibre (KF)/polystyrene (PS) composites, can be increased significantly

94


by polymeric silane as a coupling agent [55]. Study reported on the chemical treated kenaf (Hibiscus cannabinus) reinforced thermoplastic polyurethane (TPU/KF) by Methylene Diphenyl Diisocyanate (pMDI) [56]. The FTIR results depicted that the treatment of the composite with 2% NaOH + 4% pMDI shows ominously influence on its tensile properties, while the treatment with 4% pMDI does not shows considerable effect on the tensile properties of the composite bonding. Researchers fabricated bio-composites by carding comprised of kenaf fibre polylactide on treatment with a 3-glycidoxypropyl trimethoxy silane followed by hot-pressing. The bio-composites mechanical properties at temperatures beyond the glass transition get enhanced compared to the base PLA polymer [43]. According to researchers, tensile moduli and strengths of the kenaf/ cassava starch biocomposites films prepared by casting method, increased after alkali, bleached, hydrolysis treatment with the optimum filler content 6% [49]. Researcher [47] perfectly elaborated the effect of ammonium polyphosphate (APP) alkali and polyethylene glycol (PEG) on the mechanical properties of kenaf fibre reinforced polylactic acid (PLA) biocomposites. The accumulation of APP reduces the compatibility between kenaf fibre and PLA causing reduction in the mechanical properties of PLA biocomposites [47].

ural, impact and tensile strength for both the woven hybrid and random mix composite. Thus, SLS treatment can provide better mechanical properties as it improved the adhesion between fibre and matrix which in turn improved the mechanical strength than the alkali treated. Moreover SLS treatment also scrubbed fibre surface and decreased the lignin level in fibres by SLS in a better way compared to alkali [3]. Researchers also explored the mechanical properties of woven kenaf fibre reinforced polyoxymethylene (POM) composite after hybridization with polyethylene terephthalate fibre (PET) [52]. Considerable improvement in the impact and tensile properties of the woven kenaf-POM composites by the hybridization with polyethylene terephthalate fibre (PET) fibre observed. In another study, pineapple leaf fibre (PALF) and kenaf fibre at a ratio of 1:1 reinforced with high-density polyethylene (HDPE) does not show comparable improvement in flexural and tensile properties due to fibre accumulation by increasing the fibre length [71]. The fibre agglomeration appeared to be more relevant cause than the slow destruction of fibre responsible for the decline in mechanical properties during internal mixing. Research acquiesced that the mechanical properties of glass mat thermoplastic (GMT) such as Young’s modulus, tensile strength, flexural modulus and flexural strength are similar to hybrid kenaf/glass fibre epoxy composite [5].

5. Hybrid composites Hybrid composites can be prepared by combination of two fibres with one matrix or one fibre with two polymer blends [75]. Hybrid composites behave like unique material which did not exist in nature and weighed sum of the individual components. The properties of hybrid composites governed by the fibre length, orientation, fibre/matrix interfacial bonding, fibre content, extent of intermingling of fibres, and arrangement of both of the fibres. Several researchers developed hybrid composite by combining natural fibres with polymeric matrices [75]. According to researchers [44], in the case of kenaf–glass (KG) fibres unsaturated polyester hybrid composite fabricated through sheet moulding compound process display higher tensile, flexural and impact strength obtained from treated kenaf fibre. The kenaf with 15/15 v/v kenaf–glass fibres on treatment with 6% sodium hydroxide using mercerization method for 3 h yields better mechanical strength to the composite. Researchers concluded that kenaf fibre alone (30% volume fraction) or higher percentage (22.5% volume fraction) cannot withstand higher impact load leading to brittleness and less toughness in hybrid composite. According to researchers, unlikable effects to the dimensional stability and mechanical properties of composites also caused by humidity aging [40]. Moreover, research also been done depicting the kenaf fibre mechanical properties which get depreciated by the moisture penetration into the kenaf/fibre glass polyester hybrid composite even under dissimilar environmental situations including distilled water, rain water and sea water (acidic solutions) at room temperature from starting day to the 4th week [40]. In other research work, long kenaf/woven glass hybrid composite has been effectively explored by researchers [18] to study the pronounced effect of water absorption on mechanical properties. The fracture toughness shows decrement due to the water absorption displayed that it is been influenced by the fibre orientation, fibre content, exposed surface area, hydrophilicity of the individual component, void content and fibre permeability [18]. Furthermore, humidity aging also originated the unwanted effects to the dimensional stability and fracture toughness properties of composites. The research works on hybrid composite with banana also bring some important reports by treating the fibres (banana/kenaf) with 10% Sodium Laulryl Sulfate (SLS) and 10% of sodium hydroxide (NaOH) for 30 min [3]. The SLS treatment has enhanced the flex-

6. Conclusion Kenaf bast fibre has excellent tensile strength combined with superior flexural strength verified by several mechanical testing and research work enabling it to utilize in variety of application such as auto-industrial, light weight constructional applications, customary products like yarns, fabrics, and ropes. We concluded from the this work that there is no clear trend how much fibre loading give better mechanical properties but 40% fibre loading consider as optimum condition in polymer composites which give better mechanical properties. Similarly mechanical properties of kenaf fibre reinforced thermoset and thermoplastic polymers also display variation reported by different researchers but over all kenaf/epoxy composites display better mechanical properties as compared to other polymeric matrix. Furthermore, kenaf fibre has great probability of substituting the synthetic fibres (glass) for flexural and tensile applications are well evaluated. However, its impact strength is still higher, depicting a great probability of the utilization of kenaf fibre in hybrid natural fibre composites in many of the structural and nonstructural components in locomotive, construction and housing industries. Construction and building materials are the most interesting application area, which relates to enhancing the functional properties of concrete, steel, wood, and glass, as the primary construction materials. Existing materials such as solid wood and wood plastic composites based products can be replaced by kenaf reinforced polymer composites which are moulded into lightweight panels in several applications. This is the first and economically priced plastic lumber for use as constructing materials in housing industry as a engineered materials. Moreover, it is also used to make a strong, light weight, cement block with great insulation and effectively fireproof properties. Kenaf core blocks nowadays used to construct multi-story and solitary family homes, deprived of power tools. This review paper hopefully provide valuable information for further investigations and in the elaborative study of mechanical properties of kenaf fibre reinforced in polymeric composites compared to jute, oil palm, sugarcane fibres, etc. The future work would be the production of green composite materials and nanocomposite from kenaf fibre with biodegradable resin polymeric matrix with improved mechanical properties.


Acknowledgments The authors thankful to the Universiti Putra Malaysia-Malaysia for supporting this research through Research Grant: GP-IBT/2013/ 9420700. References [1] Azwa ZN, Yousif BF. Characteristics of kenaf fibre/epoxy composites subjected to thermal degradation. Polym Degrad Stab 2013;98:2752–9. [2] Nunna S, Chandra PR, Shrivastava S, Jalan A. A review on mechanical behavior of natural fiber based hybrid composites. J Reinf Plast Compos 2012;31:759–69. [3] Thiruchitrambalam M, Alavudeen A, Athijayamani A, Venkateshwaran N, Elaya Perumal A. Improving mechanical properties of banana/kenaf polyester hybrid composites using sodium laulryl sulfate treatment. Mater Phys Mech 2009;8:165–73. [4] Paukszta D, Borysiak S. The influence of processing and the polymorphism of lignocellulosic fillers on the structure and properties of composite materials—A review. Materials (Basel) 2013;6:2747–67. [5] Davoodi MM, Sapuan SM, Ahmad D, Ali A, Khalina A, Jonoobi M. Mechanical properties of hybrid kenaf/glass reinforced epoxy composite for passenger car bumper beam. Mater Des 2010;31:4927–32. [6] Rassiah K, Ahmad MMHM. A review on mechanical properties of bamboo fiber reinforced polymer composite. Aust J Basic Appl Sci 2013;7:247–53. [7] Athijayamani A, Thiruchitrambalam M, Manikandan V, et al. Mechanical properties of natural fiber reinforced polyester hybrid composites. Int J Plast Technol 2010;14:104–16. [8] Kumar NM, Reddy GV, Naidu SV, Rani TS, Subha MCS. Mechanical properties of coir/glass fiber phenolic resin based composites. J Reinf Plast Compos 2009;28:2605–13. [9] Kalia S, Kaith B, Kaur I. Pretreatments of natural fibers and their application as reinforcing material in polymer composites—a review. Polym Eng Sci 2009. [10] Adekunle K, Cho S-W, Patzelt C, Blomfeldt T, Skrifvars M. Impact and flexural properties of flax fabrics and Lyocell fiber-reinforced bio-based thermoset. J Reinf Plast Compos 2011;30:685–97. [11] Alawar A, Hamed AM, Al-Kaabi K. Characterization of treated date palm tree fiber as composite reinforcement. Compos Part B Eng 2009;40:601–6. [12] Zhu J, Zhu H, Njuguna J, Abhyankar H. Recent development of flax fibres and their reinforced composites based on different polymeric matrices. Materials (Basel) 2013;6:5171–98. [13] Anuar H, Zuraida A. Improvement in mechanical properties of reinforced thermoplastic elastomer composite with kenaf bast fibre. Compos Part B Eng 2011;42:462–5. [14] Nishino T, Hirao K, Kotera M, Nakamae K, Inagaki H. Kenaf reinforced biodegradable composite. Compos Sci Technol 2003;63:1281–6. [15] Wang Jinhua, Ramaswamy GN. One-step processing and bleaching of mechanically separated kenaf fibers: effects on physical and chemical properties. Text Res J 2003;73:339–44. [16] Krishnaprasad R, Veena NR, Maria HJ, Rajan R, Skrifvars M, Joseph K. Mechanical and thermal properties of bamboo microfibril reinforced polyhydroxybutyrate biocomposites. J Polym Environ 2009;17:109–14. [17] Han G, Lei Y, Wu Q, Kojima Y, Suzuki S. Bamboo-fiber filled high density polyethylene composites: effect of coupling treatment and nanoclay. J Polym Environ 2008;16:123–30. [18] Salleh Z, Taib YM, Hyie KM, Mihat M, Berhan MN, Ghani MAA. Fracture toughness investigation on long kenaf/woven glass hybrid composite due to water absorption effect. Procedia Eng 2012;41:1667–73. [19] Mahjoub R, Yatim JM, Mohd Sam AR, Hashemi SH. Tensile properties of kenaf fiber due to various conditions of chemical fiber surface modifications. Constr Build Mater 2014;55:103–13. [20] Elsaid A, Dawood M, Seracino R, Bobko C. Mechanical properties of kenaf fiber reinforced concrete. Constr Build Mater 2011;25:1991–2001. [21] Karimi S, Tahir PM, Karimi A, Dufresne A, Abdulkhani A. Kenaf bast cellulosic fibers hierarchy: a comprehensive approach from micro to nano. Carbohydr Polym 2014;101:878–85. [22] Abdul Khalil HPS, Yusra AFI, Bhat AH, Jawaid M. Cell wall ultrastructure, anatomy, lignin distribution, and chemical composition of Malaysian cultivated kenaf fiber. Ind Crops Prod 2010;31:113–21. [23] Paridah MT, Basher AB, SaifulAzry S, Ahmed Z. Retting process of some bast plant fibers and its effect on fiber quality: a review. Bio Resour 2011;6:5260–81. [24] Faruk O, Bledzki AK, Fink HP, Sain M. Biocomposites reinforced with natural fibers: 2000–2010. Prog Polym Sci 2012;37:1552–96. [25] Liu W, Drzal LT, Mohanty AK, Misra M. Influence of processing methods and fiber length on physical properties of kenaf fiber reinforced soy based biocomposites. Compos Part B Eng 2007;38:352–9. [26] Yousif BF, Shalwan A, Chin CW, Ming KC. Flexural properties of treated and untreated kenaf/epoxy composites. Mater Des 2012;40:378–85. [27] Herrera-Franco PJ, Valadez-Gonzalez A. Mechanical properties of continuous natural fibre-reinforced polymer composites. Compos Part A Appl Sci Manuf 2004;35:339–45. [28] Sapuan SM, Leenie A, Harimi M, Beng YK. Mechanical properties of woven banana fibre reinforced epoxy composites. Mater Des 2006;27:689–93.

95

[29] Ochi S. Mechanical properties of kenaf fibers and kenaf/PLA composites. Mech Mater 2008;40:446–52. [30] Kwon H-J, Sunthornvarabhas J, Park J-W, Lee J-H, Kim H-J, Piyachomkwan K, et al. Tensile properties of kenaf fiber and corn husk flour reinforced poly(lactic acid) hybrid bio-composites: role of aspect ratio of natural fibers. Compos Part B Eng 2014;56:232–7. [31] Fu SY, Feng XQ, Lauke B, Mai YW. Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate-polymer composites. Compos Part B Eng 2008;39:933–61. [32] Ding XD, Jiang ZH, Sun J, Lian JS, Xiao L. Stress–strain behavior in initial yield stage of short fiber reinforced metal matrix composite. Compos Sci Technol 2002;62:841–50. [33] George J, Sreekala MS, Thomas Sabu. Polym Eng Sci 2001;41:1471. [34] Edeerozey AMM, Akil HM, Azhar AB, Ariffin MIZ. Chemical modification of kenaf fibers. Mater Lett 2007;61:2023–5. [35] Akil HM, Omar MF, Mazuki AAM, Safiee S, Ishak ZAM, Abu Bakar A. Kenaf fiber reinforced composites: a review. Mater Des 2011;32:4107–21. [36] Aji IS, Sapuan SM, Zainudin ES, Abdan K. Kenaf fibres as reinforcement for polymeric composites: a review. Int J Mech Mater Eng 2009;4:239–48. [37] Thiruchitrambalam M, Alavudeen A, Venkateshwaran N. Review on kenaf fiber composites. Rev Adv Mater S Sci 2012;32:106–11. [38] Salleh FM, Hassan A, Yahya R, Azzahari AD. Effects of extrusion temperature on the rheological, dynamic mechanical and tensile properties of kenaf fiber/ HDPE composites. Compos Part B Eng 2014;58:259–66. [39] Deka H, Misra M, Mohanty A. Renewable resource based ‘‘all green composites’’ from kenaf biofiber and poly(furfuryl alcohol) bioresin. Ind Crops Prod 2013;41:94–101. [40] Ghani MAA, Salleh Z, Hyie KM, Berhan MN, Taib YMD, Bakri MAI. Mechanical properties of kenaf/fiberglass polyester hybrid composite. Procedia Eng 2012;41:1654–9. [41] Asumani OML, Reid RG, Paskaramoorthy R. The effects of alkali-silane treatment on the tensile and flexural properties of short fibre non-woven kenaf reinforced polypropylene composites. Compos Part A Appl Sci Manuf 2012;43:1431–40. [42] Batouli SM, Zhu Y, Nar M, D’Souza NA. Environmental performance of kenaffiber reinforced polyurethane: a life cycle assessment approach. J Clean Prod 2014;66:164–73. [43] Lee BH, Kim HS, Lee S, Kim HJ, Dorgan JR. Bio-composites of kenaf fibers in polylactide: Role of improved interfacial adhesion in the carding process. Compos Sci Technol 2009;69:2573–9. [44] Atiqah A, Maleque MA, Jawaid M, Iqbal M. Development of kenaf–glass reinforced unsaturated polyester hybrid composite for structural applications. Compos Part B Eng 2014;56:68–73. [45] Hao A, Zhao H, Chen JY. Kenaf/polypropylene nonwoven composites: the influence of manufacturing conditions on mechanical, thermal, and acoustical performance. Compos Part B Eng 2013;54:44–51. [46] Shibata Shinichi, Yong Cao IF. Lightweight laminate composites made from kenaf and polypropylene fibres. Polym Test 2006;25:142–8. [47] Shukor Faseha, Hassan Azman, Saiful Islam M, Mokhtar Munirah, Hassan M. Effect of ammonium polyphosphate on flame retardancy, thermal stability and mechanical properties of alkali treated kenaf fiber filled PLA biocomposites. Mater Des 2014;54:425–9. [48] Suharty NS, Almanar IP, Dihardjo K, Astasari N. Flammability, biodegradability and mechanical properties of bio-composites waste polypropylene/kenaf fiber containing nano CaCO3 with diammonium phosphate. Procedia Chem 2012;4:282–7. [49] Zainuddin SYZ, Ahmad I, Kargarzadeh H, Abdullah I, Dufresne A. Potential of using multiscale kenaf fibers as reinforcing filler in cassava starch-kenaf biocomposites. Carbohydr Polym 2013;92:2299–305. [50] Davoodi MM, Sapuan SM, Ahmad D, Aidy A, Khalina A, Jonoobi M. Effect of polybutylene terephthalate (PBT) on impact property improvement of hybrid kenaf/glass epoxy composite. Mater Lett 2012;67:5–7. [51] John MJ, Bellmann C, Anandjiwala RD. Kenaf-polypropylene composites: Effect of amphiphilic coupling agent on surface properties of fibres and composites. Carbohydr Polym 2010;82:549–54. [52] Yakubu Dan-Mallam, Mohamad Zaki Abdullah, Puteri Sri Melor Megat Yusoff. The effect of hybridization on mechanical properties of woven kenaf fiber reinforced polyoxymethylene composite. Polym Compos 2014:8. [53] Osman MR, Mazuki AAM, Akil HMd, Ishak ZAM, Bakar AA. Effect of chemical treatment on the mechanical properties of pultruded kenaf fibre reinforced polyester composites. Key Eng Mater 2014;594–595:691–5. [54] Nurul Aizan MZ, Zainathul Akhmar SAS, Mohd Muhiddin A, Nor Hazwani Z, Siti Sarah J. Study on cure characteristics and mechanical behaviours of kenaf fibre reinforced natural rubber composites. Adv Mater Res 2013;812:66–72. [55] Zheng C, Xu Y, Kawai T, Kuroda S. Effect of polymeric coupling agent on mechanical properties of kenaf fiber/polystyrene composites. Appl Mech Mater 2013;268:127–33. [56] El-Shekeil YA, Sapuan SM, Khalina A, Zainudin ES, Al-Shuja’ a O. Influence of chemical treatment on the tensile properties of kenaf fiber reinforced thermoplastic polyurethane composite. Express Polym Lett 2012;6: 1032–40. [57] Abdullah AH, Alias SK, Jenal N, Abdan K, Ali A. Fatigue behavior of kenaf fibre reinforced epoxy composites. Eng J 2012;16:105–14. [58] Ren X, Qiu R, Fifield LS, Simmons KL, Li K. Effects of surface treatments on mechanical properties and water resistance of kenaf fiber-reinforced unsaturated polyester composites. J Adhes Sci Technol 2012;26:2277–89.

96


[59] Han SO, Karevan M, Bhuiyan MA, Park JH, Kalaitzidou K. Effect of exfoliated graphite nanoplatelets on the mechanical and viscoelastic properties of poly (lactic acid) biocomposites reinforced with kenaf fibers. J Mater Sci 2012;47:3535–43. [60] Sukyai P, Sriroth K, Lee B-H, Kim HJ. The effect of bacterial cellulose on the mechanical and thermal expansion properties of kenaf/polylactic acid composites. Appl Mech Mater 2012;117–119:1343–51. [61] Mutasher SA, Poh A, Than AM, Law J. The effect of alkali treatment mechanical properties of kenaf fiber epoxy composite. Key Eng Mater 2011;471– 472:191–6. [62] Hao A, Zhao H, Jiang W, Yuan L, Chen J. Mechanical properties of kenaf/ polypropylene nonwoven composites. J Polym Environ 2012;20:959–66. [63] El-Shekeil YA, Sapuan SM, Jawaid M, Al-Shuja’a OM. Influence of fiber content on mechanical, morphological and thermal properties of kenaf fibers reinforced poly (vinyl chloride)/thermoplastic polyurethane poly-blend composites. Mater Des 2014;58:130–5. [64] Sapuan SM, Pua Fei-ling, El-Shekeil YA, AL-Oqla FM. Mechanical properties of soil buried kenaf fibre reinforced thermoplastic polyurethane composites. Mater Des 2013;50:467–70. [65] Bernard M, Khalina A, Ali Aidy, Janius R, Faizal M, Hasnah KS, et al. The effect of processing parameters on the mechanical properties of kenaf fibre plastic composite. Mater Des 2011;32:1039–43. [66] Elsaida A, Dawood M, Seracino R, Bobko C. Mechanical properties of kenaf fiber reinforced concrete. Constr Build Mater 2011;25:1991–2001. [67] Xue Y, Du Y, Elder S, Wang K, Zhang J. Temperature and loading rate effects on tensile properties of kenaf bast fiber bundles and composites. Compos Part B Eng 2009;40:189–96.

[68] Zampaloni M, Pourboghrat F, Yankovich SA, Rodgers BN, Moore J, Drzal LT, et al. Kenaf natural fiber reinforced polypropylene composites: a discussion on manufacturing problems and solutions. Compos Part A Appl Sci Manuf 2007;38:1569–80. [69] Meon MS, Othman MF, Husain H, Remeli MF, Syawal MSM. Improving tensile properties of kenaf fibers treated with sodium hydroxide. Procedia Eng 2012;41:1587–92. [70] Adlan Akram Mohamad Mazuki, Hazizan Md Akil, Sahnizam Safiee, Zainal Arifin Mohd Ishak, Azhar Abu Bakar. Degradation of dynamic mechanical properties of pultruded kenaf fiber reinforced composites after immersion in various solutions. Compos Part B 2011:42. [71] Aji IS, Zainudin ES, Khalina A, Sapuan SM, Khairul MD. Studying the effect of fiber size and fiber loading on the mechanical properties of hybridized kenaf/ PALF-reinforced HDPE composite. J Reinf Plast Compos 2011;30:546–53. [72] Russo P, Carfagna C, Cimino F, Acierno D, Persico P. Biodegradable composites reinforced with kenaf fibers: thermal, mechanical, and morphological issues. Adv Polym Technol 2013;32:E313–22. [73] Abdullah AH, Khalina A, Ali A. Effects of fiber volume fraction on unidirectional kenaf/epoxy composites: the transition region. Polym Plast Technol Eng 2011;50:1362–6. [74] Ku H, Wang H, Pattarachaiyakoop N, Trada M. A review on the tensile properties of natural fiber reinforced polymer composites. Compos Part B Eng 2011;42:856–73. [75] Saba N, Tahir P, Jawaid M. A review on potentiality of nano filler/natural fiber filled polymer hybrid composites. Polymers (Basel) 2014;6:2247–73.