Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of the bleaching of keratin fibres and the application of cationic alkyl protein softeners to bleached cashmere

Studies using ToF-SIMS have demonstrated that the 18-methyleicosanoic acid (18-MEA) bound to the fibre, via a thioester linkage, is the major Lipid pr esent at keratin fibre surfaces, Relatively higher levels of eicosanoic aci d were detected by ToF-SIMS than has been observed by wet chemical analysis . Hydrogen peroxide bleaching of keratin fibres cleaves the 18-MEA, the lev el of loss being related to the severity of oxidative attack. The adsorptio n of a wetting agent, nonyl phenol ethoxylate (NPE-8), onto the fibre occur s during bleaching with preferential adsorption of the more hydrophobic sho rt ethoxymer species observed. Characterization of protein softeners indica ted complex ToF-SIMS spectra, with the surface analysis data agreeing with the net chemical bulk analysis. Surface analysis of the 'softened' cashmere indicated that the cationic alkyl protein softeners are highly substantive and that enrichment of the more hydrophobic softener components has occurr ed, A distribution model for the cationic protein softener over the anionic fibre surface has been proposed, Copyright (C) 2000 John Wiley & Sons, Ltd .