Studies in Wool Yellowing

Abstract

A study has been made of the photo-induced free radicals in thiourea/formaldehyde- treated wool and fluorescent-brightened wool after exposure to near uv radiation in the wavelength region 2900-4000 A, and the results are compared with the observed changes in the electronic absorption spectra. Thiourea/formaldehyde treatment of wool significantly protects cystyl residues from disulfide bond rupture which otherwise occurs on irradiation with uv light of wavelength 2900-3200 A, and there are characteristic changes in the reflectance spectra of treated wools, associated with the reduced concentration of R.CH2S. radicals. Fluorescent-brightened wool exhibits an almost identical electron spin resonance (ESR) spectrum to that of untreated wool, when irradiated in the region 2900-3200 A, but, when exposed to 3650 A radiation, a greatly increased yield of free radicals is ob served in the brightened wool. Photosensitization of the protein by the fluorescent brightener is suggested as the most likely mechanism.