Preparation and characterization of phosphoric acid composite membrane by radiation induced grafting of 4‐vinylpyridine onto poly(ethylene‐co‐tetrafluoroethylene) followed by phosphoric acid doping

Preparation of phosphoric acid composite membranes by radiation induced grafting of 4-vinylpyridine (4-VP) onto elec- tron beam irradiated poly(ethylene-co-tetrafluoroethylene) film followed by phosphoric acid doping was investigated. The effect of grafting parameters (monomer concentration, absorbed dose, reaction time, and temperature) on the degree of grafting (G%) in the membrane precursor and its relation with the amount of acid doped was studied. The proton conductivity of the obtained mem- branes was evaluated in correlation with G% and temperature using ac impedance. Fourier transform infrared, thermal gravimetric analysis, X-ray diffraction, and universal mechanical tester were used to investigate chemical composition, thermal resistance, struc- ture, and mechanical properties of the membranes, respectively. The membranes of 34 and 49% recorded high proton conductivity in the magnitude of 10 -2 Sc m -1 without humidification. The membranes were also found to have reasonable mechanical integrity to- gether with thermal stability up to 160 � C. The obtained membranes are suggested to be less-water dependent and have potential for testing in high temperature polymer electrolyte membrane fuel cell. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 549-557, 2013