Positive Temperature Coefficient Effect of Polymer Nanocomposites

Abstract

Certain conductive polymer nanocomposites as PTC materials have attracted significant attention due to the advantages of low cost, excellent formability, flexibility, and lightweight over the conventional inorganic ceramic PTC materials. Several conductive theories as well as their characteristics of polymer PTC conductive composites are reviewed. The key factors that influence the PTC properties such as matrix material, kinds of conductive fillers, constructural composition, and process technologies are analyzed in details. Issues regarding the influences of polymer crystallinity on PTC effect, polymer melting temperature on PTC critical temperature, and binary-polymer blends on percolation threshold are discussed. Moreover, it is discovered that the kinds, grain sizes, shape, and distribution of conductive fillers in nanocomposites have crucial influences on the PTC effects. Therefore, the morphological control of conductive network is also reviewed. Several methods have been shown to be able to improve the PTC properties of nanocomposites, such as surface modification of conductive filler, cross-linking and heat treatment of the nanocomposite, etc. Furthermore, many novel and exciting results have been extensively investigated for the preparation of high-performance PTC nanocomposites using large aspect ratio and multifunctional conductive fillers, such as carbon nanotubes, graphene nanoplates, etc. Some thoughts on the developing trend of this kind of materials are also presented in order to learn more about the intrinsical characteristics of them and improve their properties further.