Silicone seal for bipolar plates in a pem fuel cell

Seal means (40) for sealing a bipolar plate (18,18') to a membrane (14) in a PEM fuel cell stack (10',10"). The seal (40) includes a thin layer of a cross-linkable silicone composition disposed between the bipolar plate and the membrane. The layer is applied as a liquid to either the plate (18) or the membrane (14) and preferably is polymerized prior to assembly of the stack. A preferred means for applying the composition to the bipolar plate is screen printing. Preferably, the layer has a thickness between .001 and .005 inch. The resulting fuel cell stack (10',10") exhibits superior leak resistance. In a currently preferred embodiment, a layer (40,40') of the silicone composition is provided at interfaces between a membrane (14) and both an anode side and a cathode side of a bipolar plate (18,18').