Effects of Graphene and Graphite on Properties of Highly Filled Polybenzoxazine Bipolar Plate for Proton Exchange Membrane Fuel Cell: A Comparative Study

Highly filled graphite and graphene polybenzoxazine (PBA) composites as bipolar plate materials for polymer electrolyte membrane fuel cell (PEMFC) are developed in this work. For graphite-filled PBA, the maximum graphite loading in the PBA composite was observed to be as high as 80 wt% which is significantly higher than that of graphene-filled PBA, i.e., 65 wt%. Mechanical properties, i.e., flexural modulus and flexural strength of both types of composites at their maximum contents, were much greater than the requirements of Department of Energy targets for bipolar plate materials. Electrical conductivity of the highly filled PBA composites was 255 S/cm for graphite composite and 357 S/cm for graphene composite. Furthermore, the graphite-filled PBA composite provides a thermal conductivity value up to 10.2 W/mK. Interestingly, thermal conductivity value of the PBA composite having 75.5 wt% of graphite in combination with 7.5 wt% of graphene loadings was found to be as high as 14.5 W/mK. The obtained properties of the graphite- and graphene-filled PBA composites exhibit various characteristics suitable for PEMFC applications.