Azhar Abu Bakar

Effect of water absorption on pultruded jute/glass fiber-reinforced unsaturated polyester hybrid composites

The use of natural fibers in polymer composites has given renewed interest to the development of green composites today. However, the moisture absorption of natural fibers gives serious concern, especially for their potential outdoor applications. This article reports the study results on the water absorption of pultruded jute/glass fiber-reinforced unsaturated polyester hybrid composites, which was subjected to various water conditions and their effects on its mechanical properties. Water absorption tests were performed by immersing composite specimens into three different water conditions, namely: distilled water, sea water, and acidic water, which were at room temperature, for a period of 3 weeks. The characteristic parameter of diffusion coefficient (D) and maximum moisture content (Mm) were determined from the obtained water absorption curves. The water absorption behavior of the glass/jute fiber-reinforced unsaturated polyester hybrid composite was found to follow a non-Fickian behavior. The effects of the various aqueous environments on the flexural and compression characteristics were investigated in this study. The flexural and compression properties were found to decrease with an increasing percentage of water uptakes.

A Comparative Study on Processing, Mechanical Properties, Thermo-oxidative Aging, Water Absorption, and Morphology of Rice Husk Powder and Silica Fillers in Polystyrene/Styrene Butadiene Rubber Blends

Rice husk powder (RHP) and silica-filled polystyrene (PS)/styrene butadiene rubber (SBR) composites were prepared by using the laboratory size internal mixer (Brabender Plasti-corder). The torque development, morphology, and mechanical properties such as tensile strength, elongation at break, Young modulus, and impact strength were studied. Water absorption and the effect of thermo-oxidative aging on tensile properties of composites were also examined. Filler loading and filler type influence the processibility of the composites in which RHP offers better processing advantage over silica. Tensile strength reduces with increasing filler loading for both RHP and silica composites. However, at 15 wt% the fillers act as reinforced materials to the composites. Young modulus also increases with increasing filler loading, whereas elongation at break shows no significant changes. Aging test results show that the tensile strength and elongation at break decrease and Young modulus increases with aging for RHP composites. However, for silica composites, there were no significant changes in Young modulus and elongation at break except reduction of tensile strength. The water uptake in RHP composites is higher than silica composites. Scanning electron microscopy on fracture surface shows poor filler matrix adhesion with the increasing of filler loading in the composite. This explains the reduction of tensile strength before and after aging with increasing filler loading.

Properties of ferrite-filled natural rubber composites

Nickel zinc ferrite (Ni-ZnFe2O4)-filled natural rubber (NR) composite was prepared at various loading of ferrite. The tensile properties included in this study were tensile strength, tensile modulus and elongation at break. The tensile strength and elongation at break of the composites increased up to 40 parts per hundred rubber (phr) of ferrite and then decreased at higher loading whereas the tensile modulus was increased gradually with increasing of ferrite loading. Scanning electron microscopy (SEM) was used to determine the wettability of filler in rubber matrix. From the observation, the increase of filler loading reduced the wettability of the filler. Thermal stability of the composites was conducted by using a thermogravimetry analyser (TGA). The incorporation of ferrite in NR composites enhanced the thermal stability of NR composites. The swelling test results indicate that the swelling percentage of the composites decreased by increasing of ferrite loading. The initial permeability, μi and quality factor, Q of magnetic properties of NR composites achieved maximum value at 60 phr of ferrite loading for frequency range between 5000–40,000 kHz. The maximum impedance, Z max of the NR composites was at the highest value at 80 phr ferrite loading for frequency range between 200–800 MHz.

Properties of Pultruded Jute Fiber Reinforced Unsaturated Polyester Composites

This paper deals with an experimental study on the properties of pultruded jute fiber reinforced unsaturated polyester composite (PJFRC). The ratio of fiber to matrix is approximately 70:30 by volume. Compression and flexural testing were performed in order to study the mechanical properties while TMA and DMTA were used to study the thermal properties of the composites. Morphological aspects of the composites were also evaluated using an optical and scanning electron microscope. Compression and flexural stress–strain curves showed a linear portion at initial loading phase followed by yield and plastic deformation. For the DMTA evaluation it was found that the storage modulus is strongly dependent on temperature and degrades with increasing temperature. The TMA result showed a contraction of composite upon heating instead of expansion. The acid digestion test result confirmed that the fiber content was approximately 70% by volume.

Predicting the Coefficient of Thermal Expansion of Pultruded Composites with a Natural-Fiber Reinforcement

Thermal expansion problems for unidirectional pultruded composite samples were studied. The composite materials were subjected to temperatures ranging from 0 to 200°C in order to simulate service conditions. A thermal-mechanical analyzer was employed for gathering experimental data, and the results were compared with those generated using the ANSYS software and micromechanical models. A finite-element analysis (FEA) by utilizing ANSYS was also carried out. The thermal behavior of pultruded jute-fiber-reinforced unsaturated polyester composites was simulated, and the results obtained were then compared with experimental data and predictions provided by several micromechanical models. It is found that the Schapery and Chamis micromechanical models are more efficient in predicting the value of CTE in the longitudinal and transverse directions, respectively.

The Comparison Effect of Sorbitol and Glycerol as Plasticizing Agents on the Properties of Biodegradable Polyvinyl Alcohol/Rambutan Skin Waste Flour Blends

The comparison effect of glycerol and soritol as plasticizing agents on properties of biodegradable polyvinyl alcohol (PVOH)/rambutan skin waste flour (RWF) films were studied. Results showed that the glycerol-plasticized films exhibited higher elongation at break, but lower tensile strength and Youngs modulus than sorbitol-plasticized films. Water vapor transmission rate (WVTR) was increased with the addition of plasticizing agents. The glycerol-plasticized films showed higher WVTR which indicated that glycerol had more positive contribution to water affinity compared to sorbitol. Biodegradability test revealed that the weight loss of unplasticized PVOH/RWF films was lower than glycerol- and sorbitol-plasticized PVOH/RWF films.

Preparation and Properties of Biodegradable Polymer Film Based on Polyvinyl Alcohol and Tropical Fruit Waste Flour

In this study, two different types of tropical fruit waste flour, rambutan waste flour (RWF) and banana waste flour (BWF), were blended with polyvinyl alcohol (PVOH) by solution casting method. The structure of the blend film was characterised by Fourier Transform Infrared Spectroscopy. The tensile strength and elongation at break of tropical fruit waste flour-filled polyvinyl alcohol were lower, but the tensile modulus was higher, than that of PVOH film. At a similar blend ratio, the tensile properties of the PVOH/RWF film were higher than the PVOH/BWF film, but the PVOH/BWF film showed higher water uptake than PVOH/RWF film.

Effect of Chemical Treatment on the Mechanical Properties of Pultruded Kenaf Fibre Reinforced Polyester Composites

In this study, Pultruded Kenaf Reinforced Composites (PKRC) has been successfully produced using pultrusion technique. The chemical treatment using sodium hydroxide (NaOH) at different concentration (3%, 6% and 9% M) were carried out to modify the fibre properties. After successfully characterized, it was found that kenaf fibre treated with 6% NaOH recorded the best improvement in term of mechanical properties. In particular, treated pultruded kenaf reinforced composites (TPKRC) shows better tensile and flexural properties compared to those of untreated pultruded kenaf reinforced composites (UTPKRC). It was found that NaOH at 6% concentration give the best composite properties in term of mechanical properties over the range of NaOH concentration studied.

Eco-friendly coupling agent-treated kenaf/linear low-density polyethylene/poly (vinyl alcohol) composites

Untreated kenaf (KNF) and eco-friendly coupling agent (EFCA)-treated kenaf were used as filler to prepare natural fiber-reinforced polymer composites (NFPCs) using linear low-density polyethylene (LLDPE) and poly(vinyl alcohol) (PVOH) as polymer matrices. The composites containing various loadings of untreated and EFCA-treated KNF (0, 10, 20, and 40 phr) were melt-blended in an internal mixer. The effect of treatment on the behavior of processing torque, mechanical properties, morphology, functional groups, water absorption, and thermal stability of KNF/LLDPE/PVOH composites were investigated. The results revealed that EFCA-treated KNF composites exhibited higher equilibrium torque, indicating that the viscosity of molten composites increased in the presence of EFCA. The tensile strength and tensile modulus of KNF/LLDPE/PVOH composites were improved with the addition of EFCA-treated KNF attributed to the enhancement of the interfacial adhesion between KNF and LLDPE/PVOH matrices, as confirmed by field-emission scanning electron microscopy. Fourier transform infrared spectroscopy indicated the presence of ester bond in EFCA-treated KNF composites. Furthermore, EFCA-treated KNF composites possessed a lower water absorption and greater thermal stability as compared to untreated KNF composites. Therefore, EFCA could be suggested as an effective coupling agent to enhance the performance of KNF/LLDPE/PVOH composites.

Degradation of linear low-density polyethylene/poly(vinyl alcohol)/kenaf composites

The interest of this study was to examine various kenaf (KNF) loadings and burial time, and their effects on degradability behavior of linear low-density polyethylene/poly(vinyl alcohol)/kenaf (LLDPE/PVOH/KNF) composites in soil. The LLDPE/PVOH/KNF composites with various KNF loadings were melt-mixed in a Thermo Haake internal mixer. The composites were buried in soil and their extent of degradability was assessed by tensile properties, morphological study, and weight loss and crystallinity measurements of the degraded composites. Fourier transform infrared spectroscopy was utilized to monitor the changes in chemical structure of the composites before and after degradation in soil. The results showed that with increase in KNF loading, the tensile modulus increased; meanwhile, the tensile strength and elongation-at-break of the degraded composites were dropped. Tensile properties of the degraded composites were decreased with prolonging soil burial time. The formation of cracks and pores was observed in field emission scanning electron microscope micrographs. By measuring the weight loss in LLDPE/PVOH/KNF composite samples before and after the soil burial testing and differential scanning calorimetry measurements, it was found that the weight loss and crystallinity of the composites increased with soil burial time. The degradation of the composites was confirmed by the formation of a strong absorption band assigned to carbonyl groups.