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 Ag/AgCl HCl solution ( C-1 )/membrane/HCl solution ( C-2 ) AgCl/Ag., are a linear function of log a(2) ( = C-2 gamma(2), where C-2 and gamma(2) are, respectively, the concentration and activity coefficient of the solution in compartment 2 keeping constant the concentration in compartment 1, C-1. The values of the proton transport numbers, t(+), decrease from 0.99 to 0.94 when the ratio C-2/C-1 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 degrees C are 9.84 + 10(-4) and 7.25 x 10(-4) S/cm, 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 degrees C amount to 8.35 x 10(-2) and 1.03 x 10(-2) S/cm, respectively