The Tensile Behavior of Some Protein Fibers

Abstract

The tensile properties of wool, mohair, human hair, casein, Vicara, and silk, including their behavior when knotted, after repeated stresses (mechanical conditioning) and when swollen in water were investigated. The immediate elastic recovery, the delayed recovery, and the permanent set of these fibers were measured by means of a cycling technique using the Instron tensile tester and the Sookne-Harris fiber extensometer. Actual and relative values of elonga tion components under different testing conditions are demonstrated graphically from the be ginning of the stretching procedure up to rupture. Wool has an outstanding elastic recovery in the dry state, and its elastic behavior is improved after mechanical conditioning and when wet. Mohair and human hair, and to some extent casein and Vicara, have elastic properties similar to those of wool. The tensile behavior of silk is different, being characterized by considerable permanent set (dry and wet) and by high immediate elastic recovery after mechanical conditioning.