The Relation Between Longitudinal Swelling and Water Sorption by Keratin Fibers

Abstract

Longitudinal swelling of keratin fibers has been measured as a function of time following abrupt humidity changes in the environment of the fibers. The equilibrium length change and the shape of the longitudinal swelling vs. relative humidity isotherm for horse hair and Corriedale and Lincoln wool fibers is dependent on the fiber type. The increase of length is associated with the disruption of the fiber microfibrils. At high humidities there is an overshoot in the length swelling accompanying the water absorption. For interval absorption at high humidities, the entire length increase for Corriedale fibers is transient, and the length returns to the value before the step was applied. For horse hair, only a part of the length increase is transient. The corresponding interval desorp tion causes no change of length. An effect on the longitudinal swelling due to the load on the fiber is observed for loads sufficiently large to extend the fiber into its yield region , in water. The observed relationship between longitudinal swelling and water content during sorption steps is discussed.