Radiation Grafting of Styrene Onto PFA Film for the Development of a Proton Exchange Membrane (PEM) for a Fuel Cell

摘要

PFA(poly(tetrafluoroethylene-perfluoropropylvinylether) grafted polystyrene sulfonic acid (PFA-g-PSSA) membranes were prepared by simultaneous irradiation method, using gamma-radiation from a ~60Co source at room temperature in air. The absorbed dose and dose rate ranged from 50-200 kGy and 10kGy/h, respectively. The effect of grafting conditions such as the types of diluent solvent, the irradiation dose and dose rate, as well as the styrene concentration in the grafting solution on the degree of grafting was investigated. The pysico-chemical properties of the PFA-g-PSSA membranes such as the degree of grafting(DOG), ion exchange capacity(IEC), water up take and tensile strength were evaluated. The structure variations after grafting and sulfonation were investigated using FTIR-ATR. Thermogravimetric analysis(TGA) has been used to study the thermal decomposition of the grafted PFA films. The membrane electrode assemblies(MEA) based on PFA-g-PSSA membrane bonded carbon supported catalyst; platinium for the anode and cathode were prepared. The MEAs were evaluated with a fuel cell system and a single cell test rig with 4 x 4 cm active area by using hydrogen as a fuel. The results showed that the degree of grafting was strongly dependent upon the dose rate and the type of solvent as well as the styrene concentration. The irradiation dose was also important grafting condition to mechanical strength of the grafted membrane. Some of the grafted membranes have a considerably lower resistance and higher power density than the most widely used membrane Nafion. The radiation-grafting technique is considered as one of the processes to synthesize the proton-exchange membrane (PEMs) for a fuel cell.