PERFORMANCE OF DIFFERENTLY CROSS-LINKED, PARTIALLY FLUORINATED PROTON-EXCHANGE MEMBRANES IN POLYMER ELECTROLYTE FUEL-CELLS

A series of differently cross-linked FEP-g-polystyrene proton exchange membranes has been synthesized by the preirradiation grafting method [FEP: poly(tetrafluoroethylene-co-hexafluoropropylene)]. Divinylbenzen e (DVB) and/or triallyl cyanurate (TAG) were used as cross-linkers in the membranes. It was found that the physical properties of the membra nes, such as water-uptake and specific resistance, are strongly influe nced by the nature of the cross-linker. Generally it can be stated tha t DVB decreases water-uptake and increases specific resistance; on the other hand TAC increases swelling and decreases specific resistance t o values as low as 5.0 Omega cm at 60 degrees C. The membranes were te sted in H-2/O-2 fuel cells for stability and performance. It was found that thick (170 mu m) DVB cross-linked membranes showed stable operat ion for 1400 h at temperatures up to 80 degrees C. The highest power d ensity in the fuel cell was found for the DVB and TAC double-cross-lin ked membrane; it exceeded the value of a cell with a Nafion(R) 117 mem brane by more than 60%.