Improvement of Mechanical Properties of Elastomer-Plastic Conductive Composites for Bipolar Plates in Proton Exchange Membrane Fuel Cells

Bipolar plates account for about 80% of the fuel cell stack weight. The use of low density and high strength conductive composites for making bipolar plates will result in a lighter and more compact fuel cell stack assembly. Light weight composites were developed based on a two component elastomeric silicone RTV matrix. However, two shortcomings of this composite material are low mechanical strength and relatively high permeability to gases. The purpose of this paper is to develop a new composite material which will overcome high permeability and low strength issues through the use of elastomer-plastic blends as the composite matrix. The elastomer-plastic blends consist of vinyl ester with either urethane elastomer or ethylene-propylene-diene (EPDM) rubber. The chosen elastomers have higher tensile strength and lower gas permeability than silicone rubber. The elastomers will be blended with vinyl ester thermoset plastic to further enhance these characteristics. Synergistic conductive filler system developed in previous work will be used for the new composites to make them conductive. Compatibility of blends ranging in concentration from pure plastic to pure elastomeric composition will be presented along with in-plane electrical resistivity and mechanical properties.