Effect of forming temperature on electrical and mechanical properties of PC/VGCF formed by powder metallurgy

Pressure-sensitive conductive materials are composed of vapor-grown carbon fiber (VGCF) and polymer nanocomposites and are used in a variety of pressure sensors. VGCF has attracted attention in recent years as a filler that imparts various functional properties, including electrical ones, to resins. Polycarbonate (PC) composites containing uniformly dispersed VGCF fabricated by injection molding (IM-PC/VGCF) exhibit a decreasing resistance with increasing load. IM-PC/VGCF is conductive when the VCGF content is at least approximately 12.5 vol.%. By actively forming conductive paths within composite material, VCGF makes it possible for electricity to flow with a small amount of conductive material. In this study, the conduction mechanism in PC/VGCF formed by powder metallurgy (PM-PC/VGCF) was clarified. PM-PC/VGCF samples were fabricated at varying temperatures, and their electrical and mechanical properties were measured. The results demonstrate that increasing the molding temperature improves the material’s mechanical properties but decreases its electrical resistance. Furthermore, microstructural observations using focused ion beam scanning electron microscopy revealed that low forming temperatures produced a large amount of localized VGCF; however, the VGCF was also accompanied by voids, resulting in poor mechanical properties.