Effect of cooling rate after polymer melting on electrical properties of high-density polyethylene/Ni composites

Abstract

We investigated the effects of cooling rate after polymer melting on the room temperature resistivity (PL) and on the positive temperature coefficient (PTC) effect of resistivity of high-density polyethylene (HDPE)/Ni conductive polymer composites. The L of slowly cooled samples was lower than that of quenched samples. It was hypothesized that slow cooling increases the crystallinity of HDPE, forming conductive paths as Ni particles localize in the amorphous matrix of HDPE. In the PTC effect, the inflection-point temperature of the PTC curve rose to the melting point of the HDPE with increasing Ni content. We speculated that the PTC effect of HDPE/Ni composites might occur by two mechanisms: cubical expansion of HDPE, and the diffusion of localized Ni particles into the amorphous matrix of HDPE as a result of the change from a crystalline matrix to an amorphous matrix on melting of HDPE. © 2010 The Society of Polymer Science, Japan (SPSJ) All rights reserved.