Development of graphite-filled polymer blends for application in bipolar plates

In this study, the potential of conductive polymer composites based on graphite-filled polymer blend for achieving high-performance polymer electrolyte membrane fuel cell (PEMFC) bipolar plates (BPs) was investigated. Maleic anhydride grafted polypropylene-compatibilized polypropylene (PP)/epoxy blend was selected as the matrix due to its good combination of mechanical strength and ductility, and its potential to form a co-continuous morphology, which promotes the selective distribution of the filler in one of the polymer phases and formation of high electrical performance-CPCs. PP/epoxy/graphite composites, with varying amounts of graphite, were prepared by melt mixing followed by compression molding, and then characterized. The results obtained showed that in-plane and through-plane electrical conductivities increased with an increase in graphite content while the flexural strength increased with graphite content up to a maximum value of 54.36 MPa at 70 wt% graphite, and then decreased to 40.16 MPa at 80 wt% graphite. The PP/epoxy/80 wt% graphite composite has the most promising combination of properties for BP application. While the PP/epoxy/80 wt% graphite composite exhibited in-plane and through-plane conductivities (68.03 and 3.211 Scm(-1), respectively) that are still below the targets set by the United States Department of Energy (DOE), its flexural strength and modulus (40.16 and 11.47 GPa, respectively), density (1.77 gcm(-3)), and water absorption (0.098%) satisfy the DOE targets.