PROPERTIES AND APPLICATIONS OF FILLED CONDUCTIVE POLYMER COMPOSITES

The electrical properties of polymers filled with different types of c onducting particles are reviewed. Following a theoretical description of a general effective media (GEM) equation, the experimental conducti vity-volume fraction data for thermoplastic filled with vanadium oxide particles as well as thermosetting polymer composites, are fitted to the equation. The calculated property-related parameters in the equati on are discussed. The electrical conductivity of the composites is com bined with an extremely large positive temperature coefficient (PTC) e ffect, depending on the filler type (V2O3 or carbon black), as well as on its distribution and volume fraction. Both melting and recrystalli zation behaviour are responsible for the PTC effect. Due to a conducti ve filamentary network across the medium, a localized thermal effect c omes into existence, leading to self-heating of the body. This gives t he composites potential application, for example, in plastic welding. Preliminary experimental results are reported.