XPS AND SIMS INVESTIGATION OF COVALENTLY BOUND LIPID ON THE WOOL FIBER SURFACE

Alcoholic alkali solutions, such as potassium t-butoxide in t-butanol and potassium hydroxide in ethanol, have been known to remove the cova lently bound Lipid from the wool fibre surface. In this study, x-ray p hotoelectron spectroscopy (XPS) and secondary ion mass spectrometry (S IMS) have been used to investigate the surface characteristics of unpr ocessed wool fibres (both base section and weathered tips), wool fabri c and the relative effects of potassium t-butoxide and potassium hydro xide treatments. Results comparing the fibre base and tip confirm that the weathering may result in partial loss of the covalently bound lip id from the tip. In addition, a loss of sulphur has been observed. Whi le the extent of sulphur oxidation on the surface of the base section is insignificant, the tip section may have up to 30% oxidized sulphur. There is no apparent difference between the fibres and the fabric use d in this study regarding the levels of carbon, sulphur and oxidation. Potassium t-butoxide is found to be less effective than potassium hyd roxide in removing the surface bound lipid. An explanation is given wh ich supports a hypothesis that the bound lipid is located not only at the outer most surface, but that it is also trapped within the underly ing protein layer. The potassium t-butoxide, due to its bulky molecula r structure, may not have easy access to the trapped lipid. While the extent of oxidation of surface sulphur after potassium t-butoxide trea tment is higher compared to that after potassium hydroxide treatment, the levels of sulphur loss caused by these two reagents are similar. T he removal of bound surface lipid for fabric is more effective than fo r fibres. It is suggested that fine-scale damage to the fibre, which h as been observed to occur during physical processing, is responsible f or this difference.