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Abstract In this study, the milled carbon fibre (MCF), multi-walled carbon nanotubes (MWCNT), synthetic graphite (SG) and polypropylene (PP) were fabricated using the compression moulding technique to produce a bipolar plate. The electrical conductivity and mechanical properties of the composite materials were also investigated based on different applied compositions. The studies indicated that compositions of 5PP/11MCF/1xGNP/3SG obtained the highest mechanical performance; 30 HD at 1.3 g/cm3 due to the homogenous filler dispersion within the polymer resin. These were attributed to good electrical conductivity (3.32 S/cm) compared to 5PP/13MCF/1xGNP/2SG at 1.3 S/cm. The addition of primary filler (MCF) addition onto the composite mixture was investigated, although the electrical conductivity appeared to deteriorate. The studies also reported that the composite mixture was able to withstand high-temperature application (~ 400 °C). The results obtained from this study revealed that the different filler geometry would results in different material performance. Therefore, it is important to be discussed especially in high-temperature bipolar plate applications. [ABSTRACT FROM AUTHOR]

A milled carbon fibre and polypropylene polymer composite at high filler loading was developed to produce conductive polymer composites for high conductive applications. Current research of conductive polymer composite material has reported about in-plane conductivity that was often higher than through-plane conductivity, which contradicted with the target of applications that required higher electrical conductivity in the through-plane direction. Therefore, electrical conductivity in parallel and transverse to extrusion directions were investigated. The general-effective media and modified fibre contact model were adapted to predict the electrical conductivity of the composite material. The experimental conductivity data of polypropylene/milled carbon fibre composites for transverse and parallel directions were not correlated with the general-effective media model with 2.009 and 0.663 S/cm, respectively, at the highest filler loading of 80 wt.%. This disagreement was due to various critical exponential, t values (2–3.25) that were obtained in this study. However, the modified fibre contact model seemed to have good agreement with the experimental data in the parallel to extrusion direction. This model was unable to predict electrical conductivity in the transverse direction due to lack of orientation occurring in that direction. The electrical conductivity increased as the filler loading increased as explained in percolation theory. Predicting the electrical conductivity of conductive polymer composites material is still in the preliminary stages where the researcher often obtains fluctuating agreement with the experimental values. Thus, contact between filler and orientation is considered as the main factor that influences the electrical conductivity and mechanical strength of the conductive polymer composites material. [ABSTRACT FROM AUTHOR]

Automotive parts, including dashboards and trunk covers, are now fabricated through a compression-molding process in order to produce lightweight products and optimize fuel consumption. However, their mechanical strength is not compromised to avoid safety issues. Therefore, this study investigates kenaf-fiber-reinforced polypropylene composites using a simple combing approach to unidirectionally align kenaf fibers at 0°. The kenaf composite was found to withstand a maximal temperature of 120 °C. The tensile and flexural strengths of the aligned kenaf composites (50 and 90 MPa, respectively) were three times higher than those of the commercialized Product T (between 39 and 30.5 MPa, respectively) at a temperature range of 90 to 120 °C. These findings clearly showed that the mechanical properties of aligned kenaf fibers fabricated through the combing technique were able to withstand high operating temperatures (120 °C), and could be used as an alternative to other commercial natural-fiber products. [ABSTRACT FROM AUTHOR]

The micro-scale joining of two different materials using two-component micro-powder injection molding (2C-µPIM) is an intriguing technique. The formation of defects in bi-materials at different processing stages makes this technique challenging. This study presents the fabrication of defect-free bi-material micro-parts containing hydroxyapatite (HA) and 3 mol% yttria-stabilized zirconia (3YSZ) via 2C-µPIM. Critical powder volume concentrations (CPVCs) of 61.7 vol% and 47.1 vol% were obtained for the HA and 3YSZ powders, respectively. Based on the CPVCs, the optimal loadings for the HA and 3YSZ powders were selected as 60 vol% and 45 vol%, respectively. The HA and 3YSZ feedstocks were prepared by separately mixing the optimal powder contents with low-density polyethylene (LDPE) and palm stearin binders. The feedstocks displayed pseudoplastic behavior, and the lowest ranges of viscosity for the HA and 3YSZ at a temperature of 180 °C were 157.1–1392.5 Pa·s and 726.2–985.5 Pa·s, respectively. The feedstocks were injected to produce green HA/3YSZ micro-sized components. It was found that a solvent debinding temperature of 70 °C removed 60.6% of the palm stearin binder from the sample. In the thermal debinding stage, the open channels that formed in the bi-material sample's solvent debound at 70 °C and contributed to the removal of 93 to 95% of the binder system. When the debound bi-materials were sintered at 1300 °C, the highest relative density of 96.3% was obtained. The sintering operation revealed a linear shrinkage between 13 and 17% in the sintered HA/3YSZ micro-parts. [ABSTRACT FROM AUTHOR]