The conduction mechanism of carbon black-filled poly(vinylidene fluoride) composite

The positive temperature coefficient (PTC) effect of carbon black (CB)-filled poly(vinylidene fluoride) (PVDF) composite and the changes in resistivity under different conditions were studied. It was found that there were some coherence between the volume expansion and the crystallite melting of PVDF. It is believed that the homogenization diffusion of CB particles results in increasing resistivity during volume expansion and crystallite melting. At high temperature, the resistivity decrease is due to the agglomeration of CB particles or aggregates, which results in a new CB distribution of better conductivity. On the base of the experimental evidence, it is concluded that the PTC effect of PVDF/CB composite is dominated by the volume expansion of composite matrix, the diffusion of CB particles from amorphous region to melted crystalline region and the agglomeration of CB particles. (C) 2003 Elsevier Science B.V. All rights reserved.