Mechanisms of Transient Moisture Transport Between Fabrics

Abstract

A technique was developed to study moisture transport and to determine the mechanism by which moisture is transported between fabrics under transient conditions at low moisture contents. A variety of fabrics were tested and experiments were performed at various levels of moisture content from 3% to over 100% above regain. Vapor diffusion was the major mechanism of moisture transport between two layers of fabric at low moisture levels for all fabrics. Wicking did not begin until the moisture content was high, more than 30% above regain for the woven samples. The knitted samples did not wick at all. Hydrophilic finished polyester samples had markedly improved transport rates at high moisture contents but showed no improvements at low levels of moisture where vapor diffusion prevails. Moisture transport appears to be closely related to comfort. At low moisture levels, fabrics rated as comfortable transported more moisture than fabrics rated as uncom fortable. Polyester fabric to which a hydrophilic finish was applied to improve moisture transport by wicking was judged similar in comfort to the unfinished polyester. Both transport little moisture at low levels of moisture content, perhaps because at low levels of moisture content, wicking cannot occur, since there is an insufficient amount of moisture to fill the capillaries to permit wicking.