Using Ultraviolet Radiation to Reduce Pilling of Knitted Wool and Cotton

Abstract

The Siroflash anti-pilling treatment for knitted fabrics is a process involving exposure of the fabric or garment surface to short wavelength ultraviolet radiation (UVC), fol lowed by a mild wet oxidation treatment using, for example, hydrogen peroxide or salts of permonosulphuric acid. UVC exposure is confined to the surface fibers and presensitizes them to the wet oxidation process, which selectively weakens them rel ative to the bulk fibers responsible for fabric strength. Because the surface fibers are much weaker after treatment, no anchor fibers are available to secure pills to the fabric surface. The treatment is a highly effective, chlorine-free method of preventing pilling in wool knitwear, which has now been demonstrated in wear trials. In addition. uv treatment of knitted garments prior to aqueous oxidation can effectively limit facing, up in wool knitwear during garment dyeing. A variation of the Siroflash process can also be used on cotton and cotton/wool blend fabrics by first padding hydrogen per oxide onto the fabric before UV exposure, then treating with continuous uv irradiation with a medium-pressure arc system similar to those used commercially for UV curing of polymer films. However, the continuous process is ineffective on pure wool knitted fabrics. The irradiation times necessary for effective treatment on wool using low power germicidal uv tubes vary depending on fabric or garment construction. Using these sources, however, irradiation times are too long for commercial use, and continuous exposure with a focused medium-pressure mercury arc is only partially effective. More powerful uv sources providing a high level of UVC radiation, for example noncoherent excimers or high-intensity low pressure arcs, or hybrid methods for weakening surface fibers (such as UV/H₂O₂ with a protease enzyme) may provide a rapid, effective, anti- pilling treatment for wool.