Electrical conduction phenomena between adjacent stainless steel fibres in a thermoplastic matrix

Abstract

In a programme designed to elucidate the fundamental mechanisms involved in electrical conduction through a polypropylene matrix filled with non-contacting stainless steel fibres, the current flow between two individual fibres orientated perpendicularly in a polypropylene bead has been studied. The fibre diameter was 22 μm and the gap length was 100 μm. The resistance at low voltages was five orders of magnitude lower than could be accounted for by assuming that homogeneous conduction had taken place with tabulated values of the volume resistivity of the matrix obtaining. Transmission optical microscopy revealed that during current flow, the greatest heating and degradation of the polymer did not take place along the shortest path between the fibres. It is argued that this heterogeneous conduction process may be preferentially located at the boundaries of spherulites and that low molecular weight residues, additives etc., are at least partially responsible for the enhanced conductivity levels.[/p]