Graphite bipolar plates for PEM fuel cells

Bipolar plates for polymer membrane fuel cells can be produced by compression moulding of graphite filled thermoset compounds. Especially epoxy-type polymers are proved for a good combination of mouldability, mechanical properties and chemical compatibility in the fuel cell environment. Suitable electrical and thermal properties can be achieved by a blend of graphite powders with different particle sizes and a total filler content in the range of 80...90%. The processing of such compounds with very high melt viscosity by compression moulding is still applicable. The moulded plates can be installed directly in fuel cell stacks without removing polymer rich surface skins, which are frequently observed on injection moulded thermoplastic plates. The very good temperature stability of thermosets enables the injection moulding of elastomer seals directly onto the compression moulded plates. This combination of plates with integrated seals reduces the number of components, eases the stack assembly, compensates the thickness tolerances of the moulded plate and offers by that a technically good and cost effective solution for fuel cell stack manufacturers.