DENSITY AND SOLUBILITY OF NAFION - RECAST, ANNEALED, AND COMMERCIAL FILMS

The density of Nafion membranes wetted in water and acetonitrile and t he solubility of Nafion in a 50:50 ethanol/water mixture are reported, Commercially available membranes, solution recast membranes, and reca st membranes thermally processed for varying lengths of time were exam ined. Unheated recast membranes were found to be similar to 20% less d ense in water than both commercial membranes and recast membranes heat ed at 140 degrees C for 40, 50, and 60 min. For heating times of great er than or equal to 40 min, the density of recast membranes in water w as invariant and equal to the density of commercial films. Similarly, in acetonitrile, commercial membranes and films heated for 1 h had the same density; unheated recast films were similar to 25% less dense. N afion density in acetonitrile was similar to 15% less than that in wat er. Acid pretreatment reduced Nafion film density by similar to 15%. U nheated recast films were 22-100% soluble in a sonicated ethanol/water mixture. Commercial membranes and recast films heated for as little a s 10 min were insoluble under the same conditions.