Analyzing the effect of polydopamine cross-linked serine protease on anti-shrinkage finishing of wool using response surface methodology design

The polydopamine-cross-linked serine protease anti-felting process of wool fibers was optimized by response surface methodology to prepare wool fabrics with a low tendency to shrink and high strength. The effects of dopamine substrate concentration, serine protease substrate concentration, and reaction time on the physical properties and surface color of wool were investigated. The experimental data were fitted and analyzed by the polynomial regression model, and the predicted area shrinkage and breaking strength response of wool fabric were obtained. The results were analyzed by variance analysis to determine the important parameters for optimization. Wool fabrics were prepared under the conditions of dopamine substrate concentration of 0.834 g/l, serine protease substrate concentration of 2.5 g/l, and reaction world of 127 min. Scanning electron microscopy images showed that the surface of wool fibers was covered with a large amount of polydopamine and some edge scales were passivated. After 20 cycles of washing, the shrinkage area of wool fabric is from 1.49–7.25%, with good durability. In addition, X-ray photoelectron spectroscopy, and X-ray diffraction analysis results showed that the behavior of polydopamine-coated fibers prevented the excessive hydrolysis of scales by serine protease, and the crystallization index and solubility in alkaline solution increased.