Thermal Properties of Carbon Nanofiber Sheet for Thermal Interface Materials under High Temperature and Humidity

In this study, polyvinyl alcohol (PVA) -polytetrafluoroethylene (PTFE) -vapor grown carbon fiber (VGCF) sheets are fabricated as a new paper-like thermal interface material (TIM), which is a potential substitute for traditional TIMs. Two types of PVA-PTFE-VGCF sheets were fabricated by using 120nm and 300nm PTFE particles. The microstructure shows that the VGCFs were arranged in random directions inside the sheet and interconnected via the aggregate of PVA. 300nm PTFE particles were well distributed within the sheet, while 120nm PTFE particles aggregated partially and formed pores nearby. The fabricated sheets have a low thickness of 31.2um and 28.2um, and lightweight properties with a density of 0.79 x 106 g center dot m-3 and 0.91 x 106 g center dot m-3, respectively. With the addition of 300nm PTFE particles, the fabricated sheet has higher thermal conductivities of 9.81 W center dot m-1 center dot k-1 in the in-plane direction and 2.11 W center dot m-1 center dot k-1 in the through-plane direction. In the high temperature and humidity test, the thermal conductivities of the fabricated sheet were increased due to the rearrangement of PVA and PTFE particles.