Wool Shrinkproofing Studies: Part III: Fiber Modification in Neutral Potassium Permanganate–Salt Treatments

Reaction of wool with potassium permanganate in water is shown by electron microscopy to extend into the outer cortex, whereas reaction with potassium permanganate in saturated salt solution takes place at the cuticle. Deductions based on relative reaction and clearing rates (in Part I [37]) are therefore confirmed. Attack by the reagent on the fiber is preferential in the region of the scale edges. The most dense deposition of manganese dioxide is found in the outer layer of the exocuticle. Staining of cross sections of wool with permanganate suggests that the cuticle reacts faster initially than the cortex. Amino acid analyses of wool fabrics treated with permanganate in water and different concentrations of salt show no significant variation and are similar to those obtained after dry chlorination of the same fabric. All treatments produce significant increases in cysteic acid content and decreases in serine, cystine, and tryptophan residues. Treatment with permanganate in high salt concentration appears to reduce the differential friction effect of the fiber by reducing the against-scale friction.