Tailored pyroresistive performance and flexibility by introducing a secondary thermoplastic elastomeric phase into graphene nanoplatelet (GNP) filled polymer composites for self-regulating heating devices

Abstract

Flexible and controllable self-regulating heating devices have great potential for use in applications such as healthcare devices, soft robotics, artificial skins and wearable electronics. Conventional self-regulating heating devices are often limited by the rigid nature of the polymer matrices, particularly at high conductive filler concentrations. In this paper, this limitation has been successfully tackled by using binary polymer blends that can achieve a desirable combination of mechanical, electrical and pyroresistive properties. The addition of a suitable secondary thermoplastic elastomeric polymeric phase did not only improve material flexibility, but did also tune the positive temperature coefficient (PTC) behaviour. For the first time, we systematically explore the effect of different blend morphologies as well as the selective localization of conductive fillers like graphene nanoplatelets (GNPs) on the overall mechanical and pyroresistive performance of self-regulating conductive polymer composites (CPCs). The effect of different blend morphologies was studied using different thermoplastic elastomers (TPEs) as secondary phases, and various blend compositions, into a GNP filled high density polyethylene (HDPE) nanocomposite. Blend morphologies included immiscible binary blends with a fine and coarse droplet morphology and a co-continuous morphology. In doing so, this study serves as a guideline for the selection of a secondary elastomeric phase in polymer blend based CPCs for optimised device flexibility and self-regulating heating functions.