Zainal Arifin Mohd Ishak

An investigation on the potential of rice husk ash as fillers for epoxidized natural rubber (ENR)

Abstract Burnt rice husk ash yields two grades of fillers, namely white rice husk ash, WRHA and black rice husk ash, BRHA. WRHA used in this study has been analysed to have about 96% silica content, while the BRHA has a lower silica content, typically about 54%, and a substantial carbon content, i.e. about 44%. These ashes were incorporated into epoxidized natural rubber, ENR (50 mol.% epoxidation grade) using a laboratory size two roll mixing mill. Curing using a semi-efficient vulcanization (semi-EV) was chosen and cure studies were carried out on a Monsanto rheometer. The physical testing of the ENR vulcanizates involves the determination of tensile, tear and hardness properties. The effect of the coupling agent on the curing and physical properties of the vulcanizates has been investigated using γ-mercapto-propyltrimethoxysilane. For comparison purpose, two commercial fillers, i.e. precipitated silica (grade Vulcasil-S) and carbon black (grade N330) were used. WRHA exhibits the best overall vulcanizates properties as compared to BRHA, though it is still inferior to commercial fillers especially with regard to tensile strength and tear strength. The present of the silane coupling agent has enhanced the cure times ( t 90 ), tensile and tear strengths of filled ENR vulcanizates.

Application of rice husk ash as fillers in polypropylene: Effect of titanate, zirconate and silane coupling agents

Abstract The effects of applying titanate (LICA 38), zirconate (NZ 44) and silanes (PROSIL 2020 and PROSIL 9234) coupling agents to rice husk ash (RHA) in polypropylene composites are described. RHA consists predominantly of silica. Polypropylene composites of 10–40 wt% filler loadings were compounded using a Brabender twin screw extruder. The melt flow index decreased with filler content but for the composite treated with the built-in peroxide generator (PROSIL 2020), the reverse was true. For most of the composites, the flexural modulus increased with filler content while tensile strength, elongation at break and Izod impact strength showed a decrease. PROSIL 2020 coupling agent improved the tensile strength of the composites most, while the impact properties were enhanced by the LICA 38 and the PROSIL 9234 coupling agents. None of the coupling agents increased the stiffness of the composites except for NZ 44 at maximum filler loading. The mechanical properties of the RHA composites were compared to polypropylene composites filled with commercial fumed silica and talc.

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.

An investigation of the potential of rice husk ash as a filler for epoxidized natural rubber—II. Fatigue behaviour

Abstract The fatigue behaviour of white rice husk ash (WRHA) filled ENR-50 vulcanisate was compared with those of silica and carbon black filled ENR-50. The effects of the silane coupling agent (δ-mercaptopropyltrimethoxysilane, vulcanisation systems, hysteresis and the failure mode of the vulcanisates were studied. It was found that the incorporation of fillers reduced the fatigue life of vulcanisates, while silica filled ENR vulcanisates showed the best fatigue life followed by WRHA, then carbon black filled vulcanisates. The coupling agent improved fatigue life with a simultaneous reduction in WRHA filler aggregates and improved filler dispersion for all vulcanisates. Conventional vulcanisation systems gave the highest fatigue life followed by semi-efficient and then efficeint vulcanisation systems. Carbon black filled ENR vulcanisates showed the highest hysteresis as indicated by the strain exponent. The failure mode was found to be of a dual nature.

The effects of a cationic surfactant (fatty diamine) and a commercial silane coupling agent on the properties of a silica filled natural rubber compound

The effects of a fatty diamine, termed a multifunctional additive (MFA), and a commercial silane coupling agent on the properties of a silica filled natural rubber compound have been studied. The MFA can function in its own right to improve mechanical properties. Together with the silane coupling agent, a greater improvement in properties can be obtained and their effects are, to some extent, additive. Swelling tests and dispersion measurements show that the use of the MFA and the silane coupling agent not only contributes to a better silica-elastomer adherence but also improves dispersion, which results in a lower hysteresis.

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.

Effect of Stitching Density of Nonwoven Fiber Mat towards Mechanical Properties of Kenaf Reinforced Epoxy Composites Produced by Resin Transfer Moulding (RTM)

This study will focus on the usage of kenaf as a natural fibre in producing a composite materials consists of epoxy resin by resin transfer moulding (RTM). The variation amount of fiber loading and nonwoven fibre mat condition seems can give significant changes in properties of polymer composite in terms of mechanical aspects. Optimization of stitching density of nonwoven kenaf fibre mat manages to increase the mechanical behaviour. At higher degree of fibre loading, these enhancement properties are more apparent. Depending upon the direction of stitching process in producing nonwoven kenaf fiber mat, the composite obtained exhibit anisotropy behaviour in which the mechanical properties are vary upon the stitching direction of nonwoven mat.

Effect of Polypropylene-Methyl Polyhedral Oligomeric Silsesquioxane Compatibilizer in Polypropylene/Silica Nanocomposites: Mechanical, Morphological and Thermal Studies

The Effect of 1 wt% and 3 wt% of polypropylene-methyl polyhedral oligomeric silsesquioxane (PP-POSS) as compatibilizer on polypropylene/silica (PP/SiO2) nanocomposites, prepared in the thermo Haake internal mixer was studied. The 3 wt% of PP-Methyl POSS added into PP/SiO2 system showed highest value of tensile strength. Moreover, nanocomposites with 3 wt% of PP-POSS compatibilizer showed the highest thermal stability among the nanocomposite systems in this study.

Effects of Alkali Treatment on the Properties of Kenaf Fiber-Unsaturated Polyester Composites Prepared by Resin Transfer Molding

Composites of untreated and 6% sodium hydroxide (NaOH) treated kenaf fiber mat and unsaturated polyester resin matrix were manufactured via a resin transfer molding (RTM) technique. The treated fibers were characterized with SEM and XRD. Contact angle measurements of the fibers were performed using a tensiometer. Alkali treated fiber-unsaturated polyester composites showed superior flexural properties than the composites with untreated fibers. The water absorption pattern of these composites was found to follow Fickian behavior. The tendency of the composites to absorb water decreased when alkali treated fiber mats were used.

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.