Effects of atmospheric pressure plasma on dye uptake by the surface of wool

Abstract

A woven pure wool fabric has been exposed to atmospheric pressure plasma for 30 seconds using a pilot-scale. commercial machine. X-ray photoelectron spectral data revealed large increases in oxygen and nitrogen. and a large reduction in carbon. on the surfaces of the plasma-treated fibres. A CIN ratio of 3.55 for plasma-treated wool was consistent with removal of the covalently-bound fatty acids from the surface of the cuticle cells. resulting in exposure of the proteinaceous epicuticle. Dye staining experiments revealed that the back of the fabric had received the same, uniform level of treatment as the face, despite the fact that only the face had been directly exposed to the plasma. Dyes (1 % oww) were applied to fabric at 50&deg;C (liquor ratio =40: 1) and pH values from 3 to 6. The relatively low temperature of 50&deg;C was selected in order to accentuate the effects of plasma on the rate of dye uptake. Under these conditions, dye was adsOibed onto the fibre surfaces, with very little penetration into the fibres. Effects of the plasma treatment on the rate of dyes adsorption were dyespecific. No significant effects of plasma on the rate of dye uptake were observed with relatively hydrophobic dyes, but hydrophilic dyes were adsorbed more rapidly by the plasmatreated fabric. It would appear that for more hydrophobic dyes, hydrophobic effects are more important for the adsorption of dyes by the plasma-treated fibres, even though these fibres were quite hydrophilic. On the other hand. it is concluded that for more hydrophilic dyes, electrostatic effects are more important for adsorption by the plasma-treated fibre.<br /