Development of Water Vapor Transport Resistance Protocol and Analysis

Methodology for a robust water vapor transport protocol is discussed. Transport across the membrane was driven by a water activity gradient for a range of relative humidity conditions at 95°C. An Evaluating the Measurement Process study demonstrated the ability to detect a difference in total resistance greater than 0.003 ±0.0001 cm2-s/µmol, with 90% power and 95% confidence. Electrodes used in this study increased transport resistance when applied to ePTFE reinforced membranes 10 µm or less. The resistance of a series of cast films of varying thickness were measured under hydrogen and nitrogen to isolate the interfacial and gas-phase contributions to the total resistance. The interfacial effect is not statistically significant as measured in this study.