Membranes hydrophiles non-ionisables obtenues par le greffage radiochimique de la n-vinylpyrrolidone dans des films de polytetrafluoroethylene

Non-ionizable, hydrophilic membranes were prepared by radiation grafting of vinylpyrrolidone into polytetrafluoroethylene films. The conditions under which grafting proceeds into the depth of the films were determined. It was found necessary to use aromatic solvents such as pyridine or benzene. The kinetics of the reaction were examined considering the following parameters: temperature, dose, dose-rate and concentration of monomer. The rate of grafting was found highest for monomer concentrations of 60–70 per cent. The results show that the grafting process is complicated by the high viscosity of the reaction medium and by the fact that the rate of diffusion of monomer into the films may become the controlling factor. The rate of homopolymerization of vinylpyrrolidone was also determined. The swelling of the resulting membranes was studied in various solvents. It was found that the limiting swelling ratio depended on the composition of the film but for given composition the swelling ration in water also depends on the grafting conditions. These various results are discussed.