Textile grade long natural cellulose fibers from bark of cotton stalks using steam explosion as a pretreatment

Textile grade long natural cellulose fibers with fineness of 27 dtex have been extracted from bark of cotton stalks by a combination of steam explosion, potassium hydroxide and peroxide treatments (explosion–KOH–H₂O₂). It was reported that natural cellulose fibers from bark of cotton stalks had significantly better mechanical properties than those from other lignocellulosic agricultural byproducts such as rice and wheat straws. Fibers from bark of cotton stalks were used to reinforce thermoplastic composites but could not be spun into yarns for textile applications due to their high fineness value (around 50 dtex) and/or low aspect ratio (around 660). In this research, barks of cotton stalks were treated using three methods, including steam explosion, a combination of steam explosion and potassium hydroxide treatments (explosion–KOH) and explosion–KOH–H₂O₂. The morphology, composition, carding yield, crystalline structures and tensile properties of three different cotton stalk fibers were analyzed. Results showed that cotton stalk fibers extracted by explosion–KOH–H₂O₂ had the lowest fineness value of 27 dtex and moderate aspect ratio of 1,150 in three kinds of fibers. The fibers also had most clean and smooth surfaces, highest carding yield of 68.6 %, and highest cellulose content of 82.1 wt% due to effective removal of non-cellulose impurities. Moreover, the fibers had tensile properties close to cotton fibers. Overall, the cotton stalk fibers presented a better potential to be used as textile fibers than those reported by previous researches. explosion–KOH–H₂O₂ could be an efficient method for exploring textile applications of bark of cotton stalks.