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A Device for Characterizing Water Vapor Permeability of Polymer Membranes

Abstract The ability of polymer membranes to transport moisture vapor plays a major role in the applications of waterproof breathable clothing materials. There is a couple of test methods available for measuring water vapor permeability of polymer membranes or laminated fabrics. They are either time-consuming or require large samples. A new test device was developed for determining the water vapor permeability of polymer membranes. It utilizes PTFE film and potassium acetate to generate a moisture permeation cup. Saturated nitrogen gas was used to yield a water vapor source. This test method offers short test time and calls for small sample size. The test results from the new method correlated well with those obtained from the ASTM E96-BW method. The subsequent measurements indicated that the water vapor diffusion resistance of one layer of microporous PTFE membrane was approximately 4.4 s/m and that the moisture vapor transport behavior of the PTFE membrane did not change as a function of water content in the membrane.