The Design of Waterproof, Water Vapour-Permeable Fabrics

This paper reviews some current developments in fabrics which are both water proof and water vapour-permeable. Outer garments manufactured from these materials can improve wearer comfort by reducing the buildup of perspiration in side the clothing. Tightly-woven fabrics and microporous polymer membranes transmit water vapour predominantly by a diffusion-controlled mechanism similar to air permeability. Apparently solid (i.e. non-microporous) polymer films and fabric coatings which have much lower air permeability can also be designed with good water vapour permeability. The hydrophilic mechanism involved is a com bination of (1) a physical process involving permanent or transient pores in the molecular structure, and (2) an absorption-diffusion-desorption process which depends on the chemical composition of the polymer and is specific for water vapour.