Abstract
The composites, electrical conductive fillers are dispersed into polymeric materials, are used in various industrial fields. And some materials show positive temperature coefficient resistivity (PTC). By applying PTC effect, it is possible to use these electrical conductive materials as a self-temperature control plane heater. In this study, conductive composites are prepared by epoxy resign dispersed with short nickel-coated carbon fiber and cured, First, various factors such as fiber content, its length, temperature, processing, curing conditions and expansion coefficient of matrix polymer influenced on electrical conductivity of the composites were investigated experimentally. And heating behaviors of these materials were also characterized by surface temperature measurements. As a result, it was found that the volume resistivity decreased exponentially with an increase of fiber content, whereas the critical volume to be shown gradually leveled off at high fiber content. The relation between reciprocal number of aspect ratio and critical volume loading were shown to be in a good correlation. The temperature dependence of resistivity of the composites and expansion of matrix polymer were shown to be in a good correlation. And both the composites heated with an environment temperature and those under supplied voltage showed PTC effect, i.e., the resistivity of the materials increased with an increase of temperature.
