Moisture sorption/desorption behavior of various manmade cellulosic fibers

The kinetics of dynamic water vapor sorption and desorption on viscose, modal, cotton, wool, down, and polyester fibers and lyocell knit fabrics were investigated according to the parallel exponential kinetics (PEK) model. The total equilibrium moisture regain (Minf(total)) in all the materials decreased with increasing temperature. However, the partial equilibrium fast sorption, determined by PEK simulation at 60% relative humidity (RH) and 36 (degree) C, was larger than that at 20 (degree) C, whereas the partial equilibrium slow sorption was smaller. The characteristic times in fast sorption ((tau)1) and in slow sorption ((tau)2) for lyocell were reduced when the conditions were changed from 60% RH and 20 (degree) C to 36 (degree) C, whereas those for the other fibers increased. Lyocell exhibited the highest Minf(total) value and the lowest (tau)1 and (tau)2 values, and this suggested high equilibrium moisture content and fast moisture uptake/release, that is, high moisture accessibility for lyocell. The relationships between the moisture regain, hysteresis, water retention capacity, and BrunauerEmmett-Teller surface volume in the materials were also examined.