Preparation and characterization of graphitized polyimide film/epoxy resin composites with high thermal conductivities

The graphitized polyimide films (GPF) and the graphitized polyimide tapes (GPT) were coated with epoxy resin (EP), then their composites were prepared by hot-pressing the laminated GPF and stacked GPT, respectively. The crystal structure, morphology and optical texture of GPF and GPT as well as their epoxy adhered composites were characterized by X-ray diffraction, scanning electron microscopy and polarized light microscopy. The effects of volume fraction and dimension of GPF and GPT on the thermal conductivity of their composites were investigated. The thermal conductivity and thermal diffusion coefficient of GPT/EP composites increase with GPT volume fraction. Owing to the gap among GPT, the thermal conductivity perpendicular to the hot-pressing direction of GPT/EP composite stacked with 80vol.% GPT is changeable from 453.02 W/(m·K) to 615.15 W/(m·K). The GPF/EP composite laminated with 80vol.% GPF, showing a highly oriented sandwich structure, possesses the thermal conductivity of 894.36 W/(m·K). However, the thermal conductivity along the hot-pressing direction of GPT/EP and GPF/EP composites with 80vol.% of GPT and GPF is 1.82 W/(m·K) and 1.15 W/(m·K) respectively. The obvious differentia in the thermal conductivity at perpendicular and parallel to hot-pressing directions further confirms that the two composites are highly oriented.