Hydrogen Permeation in PFSA Membranes with Different Side Chains and ePTFE Fiber Fraction

Hydrogen permeation was measured at 80 °C and four humidities for a series of membranes fabricated from the three most common perfluorosulfonic acid (PFSA) ionomers. In addition, membranes were made with different thicknesses and types of expanded PTFE (ePTFE) reinforcements. A picture has emerged where the permeation constant is lowest for the shortest side chain and decreases with decreasing ion exchange capacity (IEC). A relationship quantifying the impact of ePTFE on reducing hydrogen permeation was developed showing lower cross over with higher fiber content. For both the IEC study and the reinforcement study, the permeability is trending towards the published value for pure poly(tetrafluoroethylene) when the ionomer CF 2 content or fiber fraction of the membrane increases. In all cases, the hydrogen permeation was greatest at the highest humidities.