Three-dimensional graphene foam/micro-diamond/PDMS composites with good thermal conductivity, electrical insulation and flexibility

With the increasing power density and integration of electronic devices, there is a growing demand for polymer composites with excellent thermal conductivity, electrical insulation and flexibility. Although the addition of thermally conductive fillers is a common strategy to improve the thermal conductivity of composites, it is often at the expense of other properties. Three-dimensional graphene/graphite foam (GF) and synthetic diamond have excellent mechanical, thermal and electrical properties, and have great application potential as reinforcing fillers in the field of composite materials. However, the exploration of using them as binary fillers to prepare thermally conductive polymer composites (TCPCs) is still very limited. In this paper, PDMS-based composites filled with compressed graphene foam (c-GF) and synthetic micro-diamond (MD) were prepared, and the effects of different fillers on the thermal conductivity, electrical insulation and mechanical properties of the composites were revealed. It is confirmed that the rational addition of c-GF and MD binary fillers can make the prepared composite materials have good thermal conductivity, electrical insulation and flexibility at the same time. When the mass fractions of MD and c-GF are 48.7 wt% and 3.6 wt%, the MD/c-GF/PDMS composite exhibits excellent insulation and flexibility. Its in-plane and through-plane thermal conductivity are 3.42 Wm- 1K- 1 and 1.37 Wm- 1K- 1, respectively, which are 661.1 % and 1800 % higher than that of pure PDMS (0.18 Wm- 1K- 1). The good thermal, mechanical and insulating performances make MD/c-GF/PDMS composites have potential applications in thermal management of flexible electronics devices. This work provides useful inspiration for achieving TCPCs with good comprehensive performance from the filler chosen of view.