Part I: Drying Behavior

Abstract

When apparel fabrics made of various natural and manmade fibers are dried under "drip-dry" conditions, the usual constant rate and falling rate periods of drying can be observed. The former is normally the longer, and its length is determined largely by the amount of water which is initially picked up by the fabric and must be evaporated. This depends primarily on the fiber content and the thickness of the fabric. With rayon and cotton fabrics it can be controlled to some extent by treatment with aminoplast resins. The critical moisture content, which is the water concentration at the end of the constant rate period, has been found in some cases to depend on the sample size and fabric construction when determined on vertically suspended samples. In these cases, it is not related in a simple way to the regain of the fibers in saturated air, as is sometimes proposed. For hydrophilic fabrics, the whole falling rate period may be characterized by a dry ing coefficient based on the assumption that the area of free surface evaporation is the rate controlling factor and that this is proportional to the water content. With hydro phobic fabrics, the latter half of the falling rate period is not consistent with this assump tion, and the rate becomes somewhat more rapid.