Wool Shrinkproofing Studies

Abstract

Potassium permanganate in water confers shrink resistance on wool fabric, the degree of initial shrink resistance increasing with addition of inorganic salts. On extended severe washing, fabrics treated in higher salt concentrations felt at a greater rate, once the initial period of shrink resistance has passed, than do fabrics treated in low salt concentrations. On the basis of these observations a theory of felting shrinkage is proposed which defines felting behavior of treated wool in terms of cuticle and cortex modification. Cortex modification need only be in the outer layers. Shrink resistance conferred by cuticle modification is characterized by an initial period during which no felting shrinkage takes place, followed by felting at a rate similar to that of untreated wool. Permanganate in saturated salt is an example of such a cuticle treatment. Shrink resistance conferred by outer cortex modification is not achieved by a shrink resist induction period, but by a reduced rate of felting shrinkage. Examples of shrinkproofing treatments resulting in outer cortex modification are: permanganate in water; dry, acid, and alkaline chlorinations; and the additional shrink resistance, following permanganate oxidation, conferred by residue times in bisulfite beyond that necessary to clear manganese dioxide. In permanganate treatments followed by reductive clearing, the major portion of shrink resistance is imparted during the oxidation stage for treatments in saturated salt, and during the clearing stage for treaments in water.