Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) Analysis of the Bleaching of Cashmere Fibres, and the Application of Cationic Alkyl Protein Softeners

ToF-SIMS studies have demonstrated that the 18-methyleicosanoic acid (18-MEA) bound to the cashmere fibre surface via a thioester linkage, is removed by hydrogen peroxide bleaching. The level of 18-MEA loss was related to the severity of oxidative attack. The adsorption of a wetting agent, nonyl phenol ethoxylate (NPEO-8), onto the fibre occurs during bleaching, with preferential adsorption of the more hydrophobic, short ethoxymer species observed. Characterization of a protein softener indicated a complex ToF-SIMS spectrum, with the surface analysis data agreeing with the wet 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 occurred. A distribution model for the cationic protein softener over the anionic fibre surface has been proposed.