A. Khalina

Effect of alkali treatment on mechanical and thermal properties of Kenaf fiber-reinforced thermoplastic polyurethane composite

In this study, a composite of thermoplastic polyurethane reinforced with short Kenaf fiber (Hibiscus cannabinus) was prepared via melt-blending method using Haake Polydrive R600 internal mixer. Effect of various sodium hydroxide NaOH concentrations, namely 2, 4 and 6% on tensile, flexural and impact strength was studied. Mean values were determined for each composite according to ASTM standards. Tensile, flexural and impact strength negatively correlates with higher concentrations of NaOH. Scanning electron microscope (SEM) was used to examine the surface of both treated and untreated fibers as well as fracture surface of tensile specimens. Morphology of treated and untreated fibers showed a rougher surface of treated fibers. It also showed that some of high concentrations of NaOH treated fibers have NaOH residues on their surface. This was confirmed by energy dispersive X-ray point shooting performed on the same SEM machine. Morphology of surface of fracture indicated that untreated composite had a better adhesion. Treated and untreated fibers as well as composites were characterized using Fourier transform infrared spectroscopy (FTIR). FTIR of treated fibers showed that NaOH treatment resulted in removal of hemicelluloses and lignin. FTIR also showed that untreated composite has more H-bonding than all treated composites. Thermal characteristic studies using thermogravimetry analysis and differential scanning calorimetry showed that untreated composite was more thermally stable than treated composites.

Studying the effect of fiber size and fiber loading on the mechanical properties of hybridized kenaf/PALF-reinforced HDPE composite

Hybridization, especially where only variant natural lignocelluloses are combined, is fast receiving encouraging attention because it offers a range of properties that may be difficult to obtain with a single kind of reinforcement. In this study, tensile, flexural, and impact properties of hybridized kenaf/PALF-reinforced HDPE composite were studied. Sheets from which tensile, flexural, and impact specimens were cut out were produced from the compression molding of composite pellets and subsequently conditioned in an oven for 21 h at 103°C. The tensile and flexural specimens were tested according to ASTM D638 and ASTM D790 using a 5-kN INSTRON bluehill universal testing machine accordingly. While a notched Izoid impact test was conducted using a 1-J universal pendulum according to ASTM D256. All specimens were prepared at a fiber ratio of 1:1 kenaf:PALF and fiber lengths of 0.25, 0.5, 0.75, and 2 mm; fiber loadings of between 10% and 70% were utilized for the study. About 0.25 mm fiber showed the best tensile and flexural properties with a linear increase in properties up to 60% fiber loading while impact strength showed better property with 0.75 and 2 mm fiber lengths. At 0.25 mm fiber length, tensile strength of 32.24 MPa, flexural strength and modulus of 34.01 MPa and 4114.11 MPa, respectively, were observed at 60% fiber loading. Moduli results of all the composites formulated generally obeyed the ROM. SEM was used to examine the surface of composites produced. Tensile and impact strengths result showed inverse proportionality while flexural strength of the composite generally adhered to the ROM. However, a positive effect was observed in the case of composite’s impact strength in respect of increasing fiber length. Thus, reduction in some mechanical properties of the composite with respect to increasing fiber length is attributed more to fiber entanglement rather than attrition.

The tensile properties of single sugar palm (Arenga pinnata) fibre

This paper presents a brief description and characterization of the sugar palm fibres, still rare in the scientific community, compared to other natural fibres employed in polymeric composites. Sugar palm fibres are cellulose-based fibres extracted from the Arenga pinnata plant. The characterization consists of tensile test and the morphological examination. The average tensile properties results of fibres such as Youngs modulus is equal to 3.69 GPa, tensile strength is equal to 190.29 MPa, and strain at failure is equal to 19.6%.

Effects of Fiber Volume Fraction on Unidirectional Kenaf/Epoxy Composites: The Transition Region

This article presents the effects of fiber volume fraction on the existence of a transition region in unidirectional kenaf/epoxy composites. The composites were made from hand Lay-up techniques, with three formulations of fiber volume fraction employed: 0% (neat), 15% and 45%. The results showed that tensile properties such as tensile strength and modulus of elasticity increased as the fiber volume increased. The stress-strain curves showed that the kenaf/epoxy composites exhibited bi-linear responses with reductions in the modulus of elasticity. Surface morphology aided by a scanning electron microscope (SEM) revealed that the reduction in the modulus of elasticity was due to matrix cracking.

Development of Green Insulation Boards from Kenaf Fibres and Polyurethane

The purpose of this study was to develop effective green insulation boards fabricated from polyurethane (PU) reinforced with Kenaf fibres. Biocomposites having three different weight contents (40/60, 50/50 and 60/40 Kenaf/PU weight %) were manufactured. A fourth type was made from 60/40 NaOH-treated Kenaf/PU weight %. The results show that the elastic properties increased with Kenaf fibre content. The optimal performance was observed at a weight of 50% Kenaf fibres. Furthermore, the minimum water absorption percentage, thickness swelling, and changing in volume were recorded at a weight of 50% kenaf fibres.

Flexural and impact properties of chemically treated sugar palm fiber reinforced high impact polystyrene composites

The effects of chemical treatment on the flexural and impact properties of sugar palm fiber reinforced high impact polystyrene (HIPS) composites were studied. Two types of concentration of alkali solution (4 % and 6 %) and also two types of percentage of compatibilizing agent (2 % and 3 %) have been used in this study. The alkaline treatment is carried out by immersing the fibers in 4 % and 6 % of alkali solution for 1 hour. A 40 wt. % of alkali treated sugar palm fiber (SPF) was blended with HIPS using Brabender machine at temperature of 165 °C. The second treatment was employed by compounding mixture of sugar palm fibers and HIPS with 2 and 3 % of compatibilizing agent using the same procedure. The composites plate with dimensions of 150×150×3 mm was produced by using the hot press machine. The flexural strength, flexural modulus and impact strength of composites were measured and the values were compared to the untreated composites. Improvement of the mechanical properties of the composites has been shown successfully. Alkali treatment using 6 % NaOH solution improve the flexural strength, flexural modulus and impact strength of the composites as amount 12 %, 19 % and 34 % respectively, whereas compatibilizing agent treatment only showed the improvement on the impact strength, i.e. 6 % and 16 % improvement for 2 % and 3 % MAH respectively.

Development of Anti-Ballistic Board from Ramie Fiber

A laminate of a composite was developed from Kevlar 29-ramie fiber reinforced by polyester resin for hard body armor. The focused given to the ballistic limit, maximum energy absorption, composite failure mode, lifetime rupture, target geometry and environmental effects. The results indicated that the maximum ballistic limit at impact speed is 623.97 m/s for a 15-mm target thickness and 837 m/s for a target thickness of 25 mm. The targets were improved in terms of the impact response with increasing relative humidity in the range of 50% ± 20% but were relatively decreased in terms of resistance with increasing temperature.

Cutting Tests of Kenaf Stems

We developed a new harvesting machine with a rotary impact cutting system for cutting kenaf stems. The design of the machine was based on effective cutting knife angles and cutting speed. In this research, specific cutting force (SCF) and specific cutting energy (SCE) were measured by considering the following factors: knife edge angle (ANE), knife shear angle (SA), knife approach angle (ANA), knife rake angle (ANR), and the cross-sectional area of plant stems. In addition, an experimental impact cutting machine was manufactured and tested in the field. The rotational speed obtained with this machine had the lowest cutting torque. Kenaf stems of the V36 variety were used as the experimental material. An analysis of variance of the SCF and SCE values of the kenaf stems showed that the effects of all the above-mentioned angles (considering a broad range) on SCF and SCE were significant. Moreover, the preferred values of ANE, SA, ANA, and ANR were 25°, 40°, 40°, and 40°, respectively, according to Duncans multiple range test. Based on the impact cutting test, the rotational cutting speed had a significant effect on the specific cutting torque. Increasing the rotational speed from 308 to 788 rpm decreased the cutting torque by 26.3%. This experimental impact cutting machine had an estimated capacity of 0.07 ha h-1. The average moisture content of cut samples from the lower area of the stems was 70.78% (dry basis).

Effects of Simple Abrasive Combing and Pretreatments on the Properties of Pineapple Leaf Fibers (Palf) and Palf-Vinyl Ester Composite Adhesion

Despite being mechanically and environmentally sound, pineapple leaf fibers (PALF) are of little use in Malaysia and the least studied for composite applications. In this study effects of abrasive combing and simple pretreatments on PALF and their adhesion to vinyl ester were investigated. In pineapple leaves, PALF are present in top lamina as large vascular bundles and bottom lamina as fine strands. Tensile strength and modulus of fine PALF strands are 155% and 134% higher than those of vascular bundles respectively. Abrasive combing reduced PALF diameters by 50.3% resulting in finer bundles with 48.6% higher modulus and 51.5% greater strength without much negative effects on fiber integrity. Water-soak did not change PALF tensile properties significantly, while dilute sodium hypochlorite (NaOCl) solution improved PALF modulus and strength by as much as 123% and 35% respectively while reducing elongation at break by 47%. Dilute solution of NaOCl changed PALF structurally through higher crystallinity and closer packing resulting in increased tensile strength and modulus. PALF thermal stability was also enhanced. PALF-vinyl ester adhesion improved due to bleach pretreatment indicated by significantly reduced fiber pull-out length of broken PALF-vinyl ester composites. Morphological study using scanning electron microscope was used to confirm the findings. This study indicated that abrasive combing and simple pretreatment of dilute sodium hypochlorite are potential techniques to produce cost-effective PALF for reinforcing plastics.

Effect of Triacetin on Tensile Properties of Oil Palm Empty Fruit Bunch Fiber-Reinforced Polylactic Acid Composites

The effects of triacetin as a plasticizer on the tensile properties and morphology of oil palm empty fruit bunch (EFB) fiber-reinforced polylactic acid (PLA) composites were studied. In this research, pulverized oil palm EFB fiber size from 0.25–0.50 mm were weighted with different fiber loadings and mixed with 5% triacetin. The obtained results indicated that the tensile strength and the Youngs modulus of PLA/EFB composites with the addition of triacetin were enhanced at an 80% PLA and 20% EFB fiber loading. The interfacial properties between PLA and the EFB fiber were improved after the addition of triacetin.