Effect of Processing Routes on Electrical Properties of Polymer/Iron Composites

Abstract

Electrical properties of the polypropylene/iron (PP/Fe) composites containing unmodified and modified-Fe powder were studied. The composites prepared by twin screw extruder followed by hot compaction showed percolation threshold at 4.7 vol.% Fe. The treatment of Fe powder does not affect the percolation threshold value. However, above percolation for a given volume fraction (i.e., 10 vol.%) the electrical conductivity of the PP/modified-Fe composites is two orders of magnitude higher than those of PP/unmodified-Fe composites. The electrical conductivity of the 10 vol.% composites increased by more than 12 orders of magnitude compared to pure PP. The percolation threshold of the composites prepared by a simple ball mill followed by hot compaction is about 7.1 vol.% Fe, and the highest conductivity of these composites is 100 S/cm, i.e., three orders of magnitude higher than the composites prepared by the former route. This discrepancy was attributed to a non-uniform dispersion of Fe-clusters in the composites prepared by ball milling followed by hot compaction. In contrast, the extrusion route resulted in better dispersion of Fe particles in the PP matrix.