Relationship Between Anti-Felting Properties and Physicochemical Properties of Wool Treated with Low-Temperature Plasma

Low-temperature plasma treatment, which offers an alternative to the existing treatment using chlorine, has been drawing worldwide attention as an eco-friendly technology for the anti-felting of wool. However, the reason why that plasma-treated wool does not shrink even after repeated aqueous laundry has still not been elucidated, though a number of related papers have been published. The aim of this study is to explore the reason by analyzing the surface of Ar-plasma treat wool using FT-IR and also XPS and by examining the changes of physicochemical properties of plasma-treated wool. It is suggested that intermediate cystine oxides(i.e., -S(O)-S- and -S(O)₂-S- groups generated on the wool fiber surface) have a strong affinity with water. Subsequently, cohesive force is exerted between fiber surfaces and this results in a decrease of the flexibility of the individual fiber in assembly. Therefore, any entanglements between fibers are suppressed, and the felting is controlled. This is an important anti-felting property plasma treatment provided. In addition, carboxyl and sulphonic acid groups produced on the fiber surface play some part in the felting behavior of wool probably due to an increase in the hydration of the fiber surface.