Synergistic improvement of thermal conductivity in polymer composites filled with pitch based carbon fiber and graphene nanoplatelets

We found that the thermal conductivity of composite materials was synergistically enhanced by the simultaneous incorporation of well-dispersed pitch-based carbon fibers (PCFs) and graphene nanoplatelets (GNPs) into the matrix. Accordingly, this study investigated the causes of such enhancement and attempted to optimize the thermal conductivity. The solvent-free composites fabrication method based on powder mixing and in-situ polymerization proposed recently was employed to achieve a uniform dispersion of fillers of different sizes and shapes. The isotropic and in-plane thermal conductivity of the composite containing both uniformly dispersed 5 wt% of PCF and 15wt% of GNP achieved improvements of 82% and 183% when compared to those containing 20 wt% of GNP, and improvements of 65% and 74% when compared to those containing 20 wt% of PCF, respectively. The synergistic improvement of the thermal conductivity was maximized at the optimized composition due to the most efficient formation of thermally-conductive pathways and internal structures favorable for phonon transport.