Synergetic Effects of Liquid Ammonia, Protease, and Polyurethane Nano-Emulsion on Improving Shrink Resistance of Wool

In order to enhance the shrink-resistant properties of wool to achieve a machine washable effect, the effect of water-soluble polyurethane polymer on a worsted wool fabric which was modified by liquid ammonia and protease was investigated. The worsted wool fabric was pretreated by a continuous liquid ammonia finishing machine and then treated by protease, followed by polyurethane nano-emulsion coating. The results showed that, after liquid ammonia and protease treatment, the surface scales of wool were seriously damaged, even partly peeling off, and the disulfide bond content of the wool decreased while the active group content of the wool increased. Furthermore, after polyurethane finishing, the surface scale and the gap between the scales were covered with a thin film, and the area shrinkage reached 3.1% when the concentration of polyurethane was 20 g/L, showing an effective improvement in the shrink resistance of the worsted fabric. As far as our knowledge goes, this is a systematic report on the synergistic effect of liquid ammonia, protease, and polyurethane on the shrink resistance of wool fiber, and provides a new method for the commercial application of shrink-resistant finishing of wool fabric.