Special electrical conductivity of carbon black-filled two-phased thermoplastic vulcanizates

Abstract

The electrical properties of carbon black (CB)-filled two-phased thermoplastic vulcanizates (based on ethylene-propylene-diene copolymer and polypropylene, TPV) were investigated in this article. The results showed that the composites had a singularity in electrical conductivity compared with CB-filled polypropylene composites. Both the loading of CB and the concentration of rubber phase in TPV had the remarkable effect on electrical property of composites. The rubber particles in TPV presented unique and competitive effects in constructing CB electrical conducting network, namely exclusion and block effects. The percolation threshold value of composites apparently decreased with rubber phase content. However, percolation behavior of composites was weakened when rubber phase content was very high. The percolation behavior of composites with loading of CB is weakened apparently by rubber particles. When annealing the composites in the melt state, the resistance-time dependence of composites was strongly affected by the pressure of mold annealing. Although air aging had a negligible effect on the electrical properties, the microstructure of the CB/TPV composites had changed during air aging. CB/TPV composite only exhibited the negative temperature coefficient behavior even though the temperature was in the melting region of polypropylene, which was mainly attributed to the exclusive effect brought by the thermal expansion of rubber particles. The special electrical properties of CB/TPV can find potential application in many fields. © 2010 Wiley Periodicals, Inc.