Reaction of Wool with Permonosulfate and Related Oxidants

Abstract

As part of a program directed at zero-AOX shrinkproofing treatments, we have compared the reactivity of different oxidants with wool by following their disappearance under similar conditions. The reactivity series was as follows: aqueous chlorine > DCCA ~ permonosulfate > permanganate / salt > peracetic acid > permanganate > persulfate ~ hydrogen peroxide. This series was not related to redox potentials but generally followed the level of shrink resistance imparted by the oxidant. Fourier transform infrared spectroscopy using the attenuated total reflectance technique showed significant differences in the amounts of cystine oxidation products formed in the oxidations above. One new finding was the direct formation of low concentrations of Bunte salts by the oxidation of wool with persulfate. We further studied the surface of permonosulfate-treated fibers with scanning electron microscopy and frictional measurements. Permonosulfate treated wool fibers produce Allwörden sacs with chlo rine water, whereas aqueous chlorinated fibers do not. We suggest that the most likely mechanism for shrink resistance in permonosulfate treatments is the removal of de graded protein from below the exocuticle, producing a modified surface with a reduced differential friction between the "for" and "against" scale directions.