6—the Mechanics of the Relaxation of Wool Carpet Yarns Part Ii: Experimental Evaluation of Theory

Abstract

A theoretical analysis has been developed in which it has been assumed that the two-stage process that occurs during the relaxation of wool yarns leads to the same change in structure as a single dry-relaxation process. In the present paper, a detailed experimental evaluation of the theory is reported whereby its predictions are compared with results obtained for wool semiworsted carpet yarns spun at various twist levels. INTRODUCTIONIn the preceding paper i, it was shown that the dry-relaxed state of a wool yarn can be calculated from the strain levels of the fibres in the yarn if the change in energy accompanying changes in bulk of the yarn are known. The wet relaxation of wool yarns was shown to be a two-stage process. The first step is the regeneration of cohesively set strains in the fibres by wetting. The cohesive strains in the unrelaxed yarn are those that correspond to the equilibrium structure of a stretched and fiattened yarn. The second stage occurs during drying, when the fibres shrink axially and attempt to regain their crimp. It is the purpose of this paper to show that the bulk changes occurring during wet relaxation of semi-worsted wool yarns can be predicted from the theoretically calculated bulk changes that would have occurred in a dry-relaxation process in which the fibres are not cohesively set.