Mechanism of photoprotection of wool with formaldehyde and thiol derivatives
Version 2 2024-06-17, 21:35Version 2 2024-06-17, 21:35
Version 1 2017-05-09, 14:52Version 1 2017-05-09, 14:52
journal contribution
posted on 2024-06-17, 21:35authored byKR Millington, G Maurdev, MJ Jones
The application of thiourea and formaldehyde offers significant reductions in photoyellowing for natural, bleached and fluorescent-brightened wools. We have examined the use of alternative thiol derivates to thiourea and shown that a mixture of N-acetylcysteine and formaldehyde is similarly effective. Photo-induced chemiluminescence studies on treated wool fabrics show that the intensity of chemiluminescence following a brief exposure to ultraviolet A radiation is reduced for wool treated with thiourea and formaldehyde, N-acetylcysteine–formaldehyde and thiourea dioxide–formaldehyde, but not for formaldehyde alone. This demonstrates that a lower population of free radicals is formed in irradiated thiol-derivative formaldehyde-treated wools because of free radical scavenging by the sulphur-containing species. This free radical scavenging results in reduced photoyellowing. The effect of thiourea and formaldehyde treatment on the intrinsic fluorescence of wool is significantly different to N-acetylcysteine–formaldehyde. Thiourea and formaldehyde quenches tryptophan fluorescence relative to untreated wool, whereas N-acetylcysteine–formaldehyde treatment results in an increase in intensity probably because of a reduction in disulphide quenching.