Transport properties of polymer-vapour grown carbon fibre composites

DC electrical resistivity and thermal conductivity of polypropylene (PP) fi lled with vapour grown carbon fibre (VGCF) was studied. This was done for a wide range of fibre content and compared to systems produced under the sam e conditions in which a conventional carbon fibre was used as filler. The c omposites studied exhibit characteristic percolating behaviour. Because of the low degree of graphite perfection in the VGCF used in this work, the fr action of VGCF required to achieve percolation was higher than expected. No n-linear I-V characteristics and time dependent electrical resistivity effe cts are only observed in PP filled with VGCF. Several mechanisms must be ca lled upon to explain the observed electrical behaviour of the PP/VGCF compo site. The thermal conductivity of the composites is in agreement with the e ffective medium theories. (C) 2000 Elsevier Science B.V. All rights reserve d.