Key Engineering Materials Vols. 594-595

Abstract: Pultruded Kenaf Fiber Reinforced Unsaturated Polyester Composites (PKRC) was produced successfully using pultrusion technique at 70 wt% of fiber loading. Kenaf fiber 1400, 2200 and 3300 tex were used to produce PKRC with and without surfacing veil (SV). The aim of this study was to compare the properties of PKRC with and without SV after 200 days of natural weathering exposure. For natural weathering exposure study, PKRC 1400 specimen absorbed the least moisture followed by 2200 and the highest was 3300 tex. PKRC with SV showed lower moisture uptake than PKRC without SV in all the given environments.

Abstract: This research is focused on studying the density and mechanical properties of iron-chromium composites consolidated by innovative rapid microwave sintering technology against conventionally sintered counterparts using slow heating crucible furnace. Another aim of this study is to assess the viability of yttria (Y₂O₃) ceramic particulates as reinforcement to the iron-chromium composites. Fabrication of iron-chromium-yttria composites consolidated in microwave furnace and conventional crucible furnace was successfully accomplished. Improvement of density is evident in microwave sintered composites. The Y₂O₃ addition significantly increases the hardness of the composite (118 Hv for microwave specimens as opposed to 110Hv for conventional specimens). The study also successfully established the viability of microwave sintering technique for consolidating iron based powder metallurgy composites by up to 80% reduction of sintering time.

Abstract: Polymer blending provides an efficient way to develop new materials with improved properties while preserve the primary properties of the materials at lower cost. The blends recycled high density polyethylene (rHDPE) and recycled polypropylene (rPP) with and without maleic anhydride polypropylene (MAPP) have been investigated. The effect of different blend ratios on tensile properties, morphology and melt flow index were studied. The tensile strength and modulus of elasticity of both blends increased with increased of rPP in the blend ratios but the elongation at break decreased. It was found that the tensile strength and modulus of elasticity of compatibilized rHDPE/rPP blends higher than uncompatibilized blends. The SEM micrograph of tensile fractured surface of compatibilized blends showed better interfacial adhesion and interaction between rHDPE and rPP. The melt flow index of compatibilized blends showed better flowablity than uncompatibilized blends.

Abstract: In this study, a mold is designed in single and dual type of gate in order to investigate the deflection of warpage for thick component in injection molding process. Autodesk Moldflow Insight software was used as a medium for experimental tested. Nessei NEX 1000 injection molding machine and P20 mold material details were entered in this study to get more accurate data on top of Acrylonitrile Butadiene Styrene (ABS) as a molded thermoplastic material. Taguchi orthogonal array, analysis of Signal to Noise (S/N) ratio and Analysis of Variance (ANOVA) were implemented to get the best combination of parameter and significant factor that affect the warpage problem for both types of gates. Coolant inlet temperature, melt temperature, packing pressure and packing time are the selected parameter that used in this study. A conformation test is conducted to verify the combination parameters optimized. From the result, multi gates used was founded that can decrease the deflection of warpage for thick product. From ANOVA, the most significant factor is melt temperature for single gate, and coolant inlet temperature for multi gate. Packing pressure and packing time were slightly influence on warpage problem for both studies.

Abstract: The demand for advanced thermal management materials such as silicon carbide particles reinforced copper matrix (Cu-SiC_p) composites is increasing due to the stringent design requirement in the electronic packaging industries. High interest on Cu-SiC_p composites is highlighted by the high thermal conductivity and low coefficient of thermal expansion (CTE) properties. However, the thermal properties of the Cu-SiC_p composites are constrained by the bonding between the copper matrix and the silicon carbide particles (SiC_p) reinforcement. In the powder metallurgical (PM) methodology in particular, the bonding between the two constituents is weak, thus demoting the thermal properties of the Cu-SiC_p composites. In order to improve the interface bonding, the SiC_p were copper coated via electroless coating process. Based on the experimental results and findings, a continuous copper deposition on the SiC_p was obtained via the electroless plating process. The copper film was found to be high in purity and homogeneously deposited on the SiC_p surfaces. The CTE values of the Cu-Coated Cu-SiC_p composites were found significantly lower than those of the non-Coated Cu-SiC_p composites and were in agreement with Kernels model which accounts for both the shear and isostatic stresses developed in the component phases.

Abstract: The introduction of the metal matrix composites as the advanced electronic packaging materials is highly anticipated because their thermal properties can be engineered to match those of semiconductors, ceramics substrates and optical fibers. Among these advanced packaging materials, silicon carbide particles reinforced copper matrix (Cu-SiC_p) composites are highly rated due to the high thermal conductivity of copper and low coefficient of thermal expansion (CTE) of silicon carbide. However, the Cu-SiC_p composites fabricated via the conventional powder metallurgy (PM) technique usually have immature thermophysical properties due to the weak bonding between the copper matrix and the SiC_p reinforcement. In order to improve the bonding between the two constituents, the SiC_p were coated with copper via electroless coating process prior to PM fabrication processes. Based on the experimental results, The CTE and porosity of the Cu-SiC_p composites were significantly affected by the volume fraction of SiC_p. Furthermore, the CTE and porosity of the Cu-Coated Cu-SiC_p composites were significantly lower than the non-Coated Cu-SiC_p composites. These differences were mainly contributed by the nature of the bonding between the copper matrix and SiC_p reinforcement.

Abstract: Elastomer blends are widely used in rubber products for a variety of reasons, which include improved physical properties, improved service life, easier processing, and reduced production cost [. Butadiene and chloroprene (2-chloro-1,3 butadiene) are related monomers [. Blending of SBR with CR has been done to obtain better crystallisation resistance, better compression set resistance, lower brittleness temperature and enhanced resistance to sunlight deterioration as compared with CR alone. Other important properties, such as oil, heat, flame and ozone resistance, decrease as the amount of SBR increases [. It is possible to improve the phase morphology of SBR/CR blend by incorporating 5±10 phr of a modified copolymer that has segments chemically identical to SBR and CR phases. Addition of halocarbenes to polymers has been reported since a long time; however, available information on the commercial application on such modified polymers is limited [.

Abstract: Filler are compounding ingredients added to a rubber compound for the purpose of iether reinforcing or cheapening the compound. Despite that, fillers can also be used to modify the physical properties of both unvulcanized and vulcanized rubbers. Typically filler materials include carbon black, calcium silicate, calcium carbonate and clay [. The mechanism of reinforcement of elastomers by fillers has been reviewed by several workers. They considered that the effect of filler is to increase the number of chains, which share the load of a broken polymer chain. It is known that in the case of filled vulcanizates, the efficiency of reinforcement depends on a complex interaction of several filler related parameters. They include particle size, particle shape, particle dispersion, surface area, surface reactivity, structure of the filler and the bonding quality between the filler and the rubber matrix [.

Abstract: The performance of nanocomposites semiconducting material used as a sensor is very much depending upon physical and chemical properties of the material. In this paper we address sensitivity of ZnSnO₃ thin film deposited by hydrothermal deposition in terms of its behavior towards humidity variations. The electrical, optical and structural properties of ZnSnO₃ thin film deposit at different volume of solvent (50 ml and 70 ml) grown by novel deposition of ZnSnO₃hydrothermal with low temperature 95°C are also reviewed. The sensor performance of ZnSnO₃ thin film prepared at 50 ml volume show high sensitivity towards humidity. Using FESEM it was noted that the nanocube of ZnSnO₃ thin films growth on ZnO template with the size of nanocube is 100 to 140nm by varying the volume of the solvent.

Abstract: This paper focuses on performance of polyethersulfone (PES) ultrafiltration membrane coated with titanium dioxide (TiO₂) nanoparticles and irradiated with UV light. The flat sheet membrane was prepared via phase inversion method, with two types of membrane; TiO₂ coated PES membrane and UV irradiated TiO₂ coated PES membrane. TiO₂ suspension with concentration of 0.01, 0.03 and 0.05 wt.% were prepared and coated on the PES surface via dip coating. Membrane was immersed in all suspension for 15 minutes and 30 minutes. Then, prepared coated membranes were irradiated by 184 Watts UV lamp for 15 minutes. The performance of membranes was examined by permeation of humic acid. The morphology of membranes was analyzed by scanning electron microscopy (SEM). It was revealed that the pure water flux and humic acid permeation of UV irradiated TiO₂ coated membrane was higher than TiO₂ coated membrane. It can be concluded that TiO₂ coated with 0.03 wt.% of suspension, 30 minutes and 15 minutes UV irradiation with 184 Watt light were determined as the optimum conditions for preparation ultrafiltration PES membrane.