PTFE/Polyphosphazene Composite Fuel Cell Membranes

摘要

Polyphosphazene-based cation-exchange membranes were fabricated and evaluated for possible use in proton exchange membrane (PEM), direct liquid methanol fuel cells. Two types of membranes were prepared: (1) A composite PTFE/ sulfonated-polyphosphazene membrane; and (2) homogeneous membranes composed of either a single sulfonated phosphazene polymer or blends of a sulfonated polyphosphazene and a non-sulfonated polymer. The phosphazene polymer used for all membranes was polyBIS(3-METHYLPHENOXY) PHOSPHAZENE, which was sulfonated with SO3. To control water/methanol swelling and methanol crossover, the polymer was either chemically crosslinked (using UV light and a photo-initiator or electron beam radiation) or blended with a hydrophobic polymer. Methanol crossover was high in membrane-electrode-assemblies with PTFE/polyphosphazene composite membranes (that were fabricated at W. L. Gore and Associates, Inc.) due to pore impregnation of the polyphosphazene in the PTFE matrix. Homogeneous crosslinked and blended membranes with sulfonated polyphosphazene exhibited an acceptably.