Effects of imposing a temperature gradient on moisture vapor transfer through water resistant breathable fabrics

Very often outerwear apparel is made of water resistant yet breathable fabr ics, and normally these fabrics have multilayer structures of various polym eric materials. The working mechanisms of water vapor transmission through these fabrics are not well understood. The rate at which these breathable f abrics are able to transmit water vapor is most often measured under standa rd textile testing conditions of 20 degrees C and 65% relative humidity, bu t these tests are often little better than useless in predicting a fabric's performance under "real" conditions. The experiments described in this pap er are designed to test breathable fabrics under more realistic conditions. Water is heated to 33 degrees C in order to simulate a sweating body, and the rate at which the vapor is transmitted through various breathable fabri cs is measured. Experiments involve ambient temperatures of 6, 10, 15, and 20 degrees C, with the relative humidity held at a constant 65% throughout.