A novel flexible phase change composite with electro-driven shape memory, energy conversion/storage and motion sensing properties

Abstract

In addition to their lower thermal conductivity, leakage during the melting phase and poor energy conversion ability, the fragility of phase change materials is an issue that is worth addressing to widen their application scope. Herein, we propose a low-cost and facile method to develop a flexible electro-driven phase change composite with unidirectional shape memory effects and motion detection properties. The phase change composite is composed of carbonized cotton cloth as a conductive supporting structure, paraffin wax as a latent heat storage material and thermoplastic polyurethane as a protective layer. The woven framework of carbonized cloth endowed the paraffin wax with the ability to generate Joule heating at a lower voltage due to its high electrical conductivity (374 S m⁻¹). The multifunctional layer of thermoplastic polyurethane wrapped the carbon cloth/paraffin and greatly improved the form-stability, flexibility and mechanical strength of the composite. Shape fixity and shape recovery properties of the composite were achieved by the synergic effect of the phase transition in paraffin and the elasticity of thermoplastic polyurethane. Moreover, the presence of conductive carbon cloth enabled the composite to achieve good electrothermal conversion efficiency and motion sensing properties. The fabricated flexible phase change composite may serve as a smart material for versatile thermal management applications.