Electrochemical properties of ion-exchange membranes based on sulfonated EPDM-polypropylene blends

The preparation of cation-exchange membranes by compression molding of sulfonated EPDM-polypropylene blends is described. Concentration potentials measured in a two-compartmental cell with configuration AgAgCl HCl solution (C1) membrane HCl solution (C2) AgClAg., are a linear function of log a2 (= C2 γ2, where C2 and γ2 are, respectively, the concentration and activity coefficient of the solution in compartment 2 keeping constant the concentration in compartment 1, C1. The values of the proton transport numbers, t- +, decrease from 0.99 to 0.94 when the ratio C2 C1 increases from 0.1 to 5, nearly the same decrease reported for Nafion 117 in the same variation of concentration ratios. Proton conductivities at 25°C are 9.84× 10-4 and 7.25× 10-4 Scm, respectively, for water-saturated membranes containing 20 and 10% of polypropylene, more than one decade below the value reported in the literature for the conductivity of Nafion membranes at the same temperature. These conductivities at 90°C amount to 8.35× 10-2 and 1.03× 10-2 Scm, respectively.