Study On Salt-Shrinking Treatment And Anti-Felting Finishing Of Wool Yarns By Potassium Permanganate

As one kind of high-quality natural protein fiber, wool plays an important role in textile industry. Nowadays people pay more and more attention to the R&D of the functionalization of wool fibers with an aim to create a new range of differential products and environment-friendly processes in order to compete with the emerging synthetic fibers and other textiles.The netural salts such as calcium nitrate, calcium chloride, etc. are commonly used in salt-shrinking treatment. Because of their strong hydratability, the metal ions (e.g. Ca2+) in this kind of natural salts are accompanied with a large number of water molecules when they enter into the amorphous region of fibers. As a result, fibers swell and shrink severely. Although there are so many reports on salt-shrinking treatment of silk fibers, few can be found in its application on wool. Salt-shrinking treatment of wool yarns and its mechanism were systematically investigated in this paper. The optimal conditions for salt-shrinking treatment were obtained by analyzing the effect of temperature, time, pH value and the concentration of calcium nitrate on shrinkage and mechanical properties of wool yarns. Scanning electron microscopy (SEM), wide-angle X diffraction (WAXD), Fourier transform infrared spectroscopy with attenuated total internal reflectance mode measurement (FTIR-ATR), FT-Raman spectroscopy, thermogravimetry (TG), differential thermal gravimetry (DTG) and differential scanning calorimetry (DSC) were explored to clarify the mechanism of salt-shrinking. The results indicated the scale of wool fiber was damaged during salt-shrinking treatment, and a-crystallinity decreased accompanied with conformational changing from a-helix to random coil after salt-shrinking treatment.Potassium permanganate KMnO4,a strong oxidant, can impart anti-felting effect to wool fibers by denuding the scales of wool fibers. Potassium permanganate is now mainly used in anti-felting finishing of wool fabrics and wool tops. The application of potassium permanganate in anti-felting finishing of wool yarns was investigated in this study. The conditions for anti-felting finishing were optimized by analyzing the effect of concentration of potassium permanganate, pH, and temperature on the directional frictional effect (D.F.E.) and mechanical properties of wool yarns. Allworden reaction and scanning electron microscopy (SEM) were used to analyze the surface morphology of wool fibers. The results showed the scales of wool fibers were peeled off during the treatment using KMnO4. The blurred scale edges led to the reduction of directional frictional effect (D.F.E.), which limited the relative movement of wool fiber. The shrinkage of woven wool fabric treated with the optimal conditions decreased from 13.15%to 3.31%.