Effects of branched carbon nanotubes and graphene nanoplatelets on dielectric properties of thermoplastic polyurethane at different temperatures

Elastomers with high dielectric constant and low loss have potential applications in energy storage and conversion devices, and the study of dielectric-temperature dependence for dielectric elastomers is of great significance. Here, we report on a strategy to tune dielectric constant and loss of thermoplastic polyurethane (TPU) composites by using hybrids of carbon nanostructures (CNS, also known as branched carbon nanotubes) and graphene nanoplatelets (GNP). At the same filler content, CNS have a greater contribution to the total dielectric constant than GNP, however it is accompanied by a larger loss tangent. By contrast, using a CNS-GNP hybrid results in improved dielectric properties, i.e. high dielectric constant and low loss tangent for a wide temperature range, as well as the same elongation at break as neat TPU. Additionally, the dielectric-temperature dependence for TPU/CNS composites enables the potential applications for temperature sensors by correlating temperature with dielectric constant. This study enhances understanding of the effect of filler type and temperature on dielectric properties of TPU composites, as well as their mechanical properties, introducing an effective strategy for the property optimization of dielectric elastomers as functional materials for sensor and actuator applications.