Capillary sorption in fibrous assemblies

Abstract

Sorption of a liquid drop on fabric or paper was measured as a function of time by photographing simultaneously the spreading liquid and a timer. The area depicting the spreading liquid was cut from the photograph and weighed. The method was calibrated by photographing a standard area. The area A covered by the spreading liquid was found to be A = K( γ η)uVmtn, where K is a coefficient dependent on the advancing contact angle of the liquid on the fibers, the permeability and thickness of the fabric, and the saturation concentration of the liquid in the fabric. t denotes the spreading time, γ the surface tension, η the viscosity, and V the volume of the liquid. The exponents u, m, and n were found to be 0.3, 0.7, and 0.3, respectively, for n-alkanes spreading on polyethylene terephthalate/cotton, polyethylene terephthalate, and cotton fabrics. The equation holds when the fibers are impermeable to the spreading liquid. When the liquid diffuses into the fibers, e.g., water into cotton fibers, the exponent n depends on the drop volume. © 1981.