The water vapor diffusion resistance of the hydrophilic component of Gore-Tex™ II is measured at temperatures down to -24°C. The experiment is designed to simulate diffusion of water vapor through a clothing shell from a coating of ice on its inner surface. The permeability of the samples decreases exponentially with decreasing tem perature; this variation is a combined effect of temperature and relative humidity. At subzero temperatures, water vapor transfer through this material is only a few percent of its room temperature value. Other hydrophilic films used in outdoor clothing are likely to be similarly affected.
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