Hybrid conductive filler/polycarbonate composites with enhanced electrical and thermal conductivities for bipolar plate applications

Conductive polymer composites (CPCs) with high electrical and thermal conductivities are demanded for bipolar plates of fuel cells. In this work, CPCs of polycarbonate (PC) filled with carbon nanotube (CNT), carbon fiber (CF), graphite (G), and their double and triple hybrids were prepared using solution casting method followed by compression molding. The results showed that the electrical percolation thresholds for the PC-CNT and PC-CF were similar to 1 wt% and similar to 10 wt%, respectively, while no clear threshold was found for PC-G composites. Addition of 3-5 wt% CNT improved the electrical conductivity of PC-CF and PC-G systems up to 6 orders of magnitude and enhanced the thermal conductivity as much as 65%. The results of triple hybrid CPCs (with constant loading of 63 wt%) indicated that the combination of highest electrical and thermal conductivities is achieved when the CF and CNT loadings were near their percolation thresholds. Therefore, a triple filler system of 3 wt% CNT, 10 wt% CF, and 50 wt% G resulted in a composite with the through-plane and in-plane electrical conductivity, and thermal conductivity values of 12.8 S/cm, 8.3 S/cm, and 1.7 W/m center dot K, respectively. The results offer a combination of properties surpassing the existing values and suitable for high-conductivity applications such as bipolar plates. POLYM. COMPOS., 40:3189-3198, 2019. (c) 2018 Society of Plastics Engineers