Using an eco-friendly deep eutectic solvent for waterless anti-felting of wool fibers

Anti-felting or felting resistance process is a major finishing process for woolen goods which guarantees the dimensional stability of the product in washing and cleaning procedures mainly by covering or removing the scales from the surface of the wool fibers. Today, about 90 percent of anti-felting operations are carried out in a water-based chlorination process which releases tons of chlorine-containing discharge into the environment. Here we introduced deep eutectic solvents (DESs) as green substitutes for non-environmentally friendly sodium hypochlorite for getting anti-felting properties on woolen goods. Response surface methodology (RSM) based on four factors and in three levels, using Box-Behnken design (BBD) was used for designing the experiments and optimizing effective parameters in the anti-felting process of wool fibers using DESs. It was found that a special DES called Reline which is a mixture of choline chloride and urea in a 1:2 M ratio can successfully work as a green anti-felting agent and non-aqueous reaction medium. The shrinkage percentage of the Reline (DES) treated wool was 10% and very close to the 8.56% shrinkage seen on the hypochlorite-treated wool sample compared to more than 32% shrinkage observed on untreated fibers. Reline exhibited better preservation of the physico-chemical and mechanical properties of the fibers causing only a 6.04% reduction in the breaking load of wool fibers compared to the hypochlorite-treated sample with a 24.86% reduction in breaking load of fibers. Anti -felted wool using the new Reline agent exhibit much better whiteness and lower yellowness compared to the chlorine-treated fibers. Microscopical observations, reflectance spectrophotometry, and tensile measurements all confirmed the superiority and numerous advantages of using Reline as a green anti-felting agent instead of polluting chlorinated chemicals. Reline usage as a green chemical encompasses other benefits such as reduced water consumption, reduced effluent, and more importantly DES recyclability and reuse.