Pyroresistive response of percolating conductive polymer composites

TL;DR

This paper investigates the microscopic mechanisms behind the pyroresistive response in conductive polymer composites, emphasizing the role of thermal expansion and electrical connectivity through simulations.

Contribution

It introduces a meshless simulation approach to study how thermal mismatch affects electrical connectivity in CPCs, providing new theoretical insights.

Findings

Electrical conductivity responds to local strains caused by thermal mismatch.

Conductor-insulator transition results from a sudden disconnection of the percolating network.

Thermoelastic response influences the pyroresistive behavior of CPCs.

Abstract

The pyroresistive response of conductive polymer composites (CPCs) has attracted much interest because of its potential applications in many electronic devices requiring a significant responsiveness to changes in external physical parameters such as temperature or electric fields. Although extensive research has been conducted to study how the properties of the polymeric matrix and conductive fillers affect the positive temperature coefficient pyroresistive effect, the understanding of the microscopic mechanism governing such a phenomenon is still incomplete. In particular, to date, there is little body of theoretical research devoted to investigating the effect of the polymer thermal expansion on the electrical connectivity of the conductive phase. Here, we present the results of simulations of model CPCs in which rigid conductive fillers are dispersed in an insulating amorphous matrix. By employing a meshless algorithm to analyze the thermoelastic response of the system, we couple the computed strain field to the electrical connectedness of the percolating conductive particles. We show that the electrical conductivity responds to the local strains that are generated by the mismatch between the thermal expansion of the polymeric and conductive phases and that the conductor-insulator transition is caused by a sudden and global disconnection of the electrical contacts forming the percolating network.