Effect of the compression molding parameters on the in-plane and through-plane conductivity of carbon nanotubes/graphite/epoxy nanocomposites as bipolar plate material for a polymer electrolyte membrane fuel cell

The main challenges for commercialization of a single-filler graphite (G) polymer-matrix composite as bipolar plates are its low electrical conductivity and flexural strength. The minimum requirements set by the US Department of Energy (DOE) are the electrical conductivity and flexural strength to be greater than 100 S/cm and 25 MPa, respectively. In this study, the electrical conductivity of a G/epoxy (EP) composite (single filler) is only 50 S/cm (in-plane conductivity) at 80 wt% G. However, flexural strength is greater than 25 MPa. Using carbon nanotubes (CNTs) as the second filler at a concentration of 5 wt% in a CNTs/G/EP nanocomposite resulted in the in-plane and through-plane electrical conductivity and flexural strength being 180 S/cm, 75 S/cm, and 45 MPa, respectively. The density of the CNTs/G/EP nanocomposite is also less than that of G/EP composite, which demonstrates that a total weight reduction is achievable.