The Internal Dynamic Mechanical Loss in α-Keratin Fibers during Moisture Sorption

The dynamic mechanical loss in α-keratin fibers such as wool and horse hair can be measured by the phase difference “φ” between the oscillating extension applied to the fiber and the resultant oscillatory force. When the environment of a fiber is changed from dry to more moist conditions, the value of φ has a maximum at the point in time when the swelling of the fiber reaches a maximum. This phenomenon parallels others already observed and confirms the general picture that during sorption the molecular structure of a keratin fiber has a maximum mobility. It follows that any applied deformation at this stage will reach structural equilibrium in the shortest time.