Dynamic surface wetness of fabric and the amount of moisture vapor in the air next to the body are known to be important factors for the comfort of worn clothing. Recently, several micro-porous films and coating materials have been developed and used in conjunction with conventional fabrics for the purpose of improving moisture vapor permeability and water proofing characteristics in functional clothing.;Effects on moisture vapor transmission rate of fiber type, and film variables such as thickness, pore size and porosity were explored to understand the mechanisms of moisture transfer of fabric/porous film assemblies. Double knits of 100% cotton and 100% polyester fabric were chosen as representative hydrophilic and hydrophobic textiles, respectively. Commercially produced micro-porous films used included poly(propylene), poly(tetrafluoroethylene)(PTFE), and a poly(urethane copolymer) monolithic coating.;Findings showed that fiber type significantly influences changes of surface temperature and moisture vapor pressure at the inner fabric surface. Cotton assemblies with a film between the two layers of fabric showed the highest peaks of inner surface temperature, and the slowest rate of vapor pressure build-up at the inner surface. Polyester samples exhibited the lowest inner surface temperatures, but much higher concentration of moisture vapor at the initial stage. Mixed assemblies of cotton and polyester fabric with films revealed moderate inner surface temperature peaks and moderate vapor pressure changes. Fabric arrangements using an outer fabric of cotton and inner layer of polyester with films in between showed relatively slower rates of vapor pressure change, with lower inner surface peak temperatures than the reversed arrangement. In general, the presence of the films in assemblies was associated with higher inner surface temperature and more rapid build-up of vapor pressure. The physical constitution of the films, rather than the hydrophilicity, was more responsible for changes of heat and moisture vapor transfer through the fabric/micro-porous film assemblies.;This study involves measurement of surface temperature changes and moisture vapor transfer through fabric and porous film assemblies under simulated body conditions. It uses a sweating hot plate device, modified from the cobaltous chloride moisture vapor transmission method. Microhygrometry and miniature thermistors were used to dynamically measure vapor pressure and temperature on both sides of a fabric-film assembly. This was accomplished by sampling local air continuously, using a pump and hypodermic needles, without disturbing the whole system of the sweating device.
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