Per-fluorinated sulfonic acid/PTFE copolymer studied by positron annihilation lifetime and gas permeation techniques

[摘要] The mechanism of gas permeation in per-fluorinated sulfonic acid/PTFE copolymer Fumapem® membranes for polymer electrolyte fuel cells has been investigated from the viewpoint of free volume. Three different samples, Fumapem® F-950, F-1050 and F-14100 membranes with ion exchange capacity (IEC) = 1.05, 0.95 and 0.71 meq/g, respectively were used after drying. Free volume was quantified using the positron annihilation lifetime (PAL) technique and gas permeabilities were measured for O2and H2as function of temperature. Good linear correlation between the logarithm of the permeabilities at different temperatures and reciprocal free volume indicate that gas permeation in dry Fumapem® is governed by the free volume. Nevertheless permeabilities are much smaller than the corresponding flexible chain polymer with a similar free volume size due to stiff chains of the perfluoroethylene backbone.

[发布机构] Physics Department, Faculty of Science, Minia University, Minia; B.O.61519, Egypt^1;Fuel Cell Cutting-Edge Center (FC-Cubic), Technology Research Association, 2-3-26 Aomi, Koto-ku, Tokyo; 135-0064, Japan^2

[效力级别] 化学

[关键词] Flexible chains;Gas permeation;Ion exchange capacity;Linear correlation;Polymer electrolyte fuel cells;Positron annihilation lifetimes;Stiff chains;Sulfonic acid