Electrical Conductivity of Polymer Composites Filled with Metal

Abstract

Conductive polymer composites filled with conductive filler particles exhibit a positive temperature coefficient (PTC) effect. It is desirable to develop these composites with a low resistivity at room temperature and a high resistivity after polymer melting. We evaluated the relationships between the PTC properties of the composites and the type of the metal, the particle size of the metal, and the metal content. Among metals containing composites evaluated in this study, the composite consisting of tungsten (W) showed the best PTC properties. Then we compared the PTC properties between the composites consisting of W and of CB. The composite consisting of W has a lower resistivity at room temperature and a higher resistivity after polymer melting than that consisting of CB. Generally, the composite which has a low resistivity at room temperature has a low resistivity after polymer melting. We developed the composite consisting of high-density polyethylene (HDPE)/W = 59/41 vol% (7/93 wt%), which showed a 0.01 Ω cm resistivity at room temperature, and a 10⁵ Ω cm resistivity after polymer melting. This composite has no negative temperature coefficient effect after polymer melting.