Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) films. I. Effect of grafting conditions

The simultaneous radiation grafting of styrene onto poly(tetrafluoroethylen e-co-hexafluoropropylene) (FEP) films was studied at room temperature. The effects of grafting conditions (type of solvent, irradiation dose, dose rat e, and monomer concentration) were investigated. The degree of grafting was found to be dependent on the investigated grafting conditions. The depende nce of the initial rate of grafting on the dose rate and the monomer concen tration was found to be of 0.5 and 1.3 orders, respectively. The results su ggest that grafting proceeds by the so-called front mechanism in which the grafting front starts at the surface of the film and moves internally towar d the middle of the film by successive diffusion of styrene through the gra fted layers. Some selected properties of the grafted films were evaluated i n correlation with the degree of grafting. We found that the grafted FEP fi lms possess good mechanical stability, which encourages their use for the p reparation of proton exchange membranes. (C) 2000 John Wiley & Sons, Inc.