Challenges and solutions for recovering mixed fiber waste from knitted used textiles

Pure new wool is rarely found as a quality in German used clothing sorting plants. On the other hand, large quantities of synthetic fiber-wool blends are produced as a waste product of the fast fashion industry. The multiple blends in particular lead to a high loss of value. Previous studies have shown that fiber blends with up to seven different fibers are in circulation within one piece of clothing. Better qualities find their second use in second-hand stores, while lower qualities are categorized and sorted in sorting plants according to their material composition and have so far mostly been processed as filling and insulating materials. In order to recycle these fibers for the clothing sector, two areas of mechanical recycling are being analyzed and modified within my PhD research. The finer sorting, as well as the subsequent cutting and tearing process, have a significant influence on the fiber dissolution of the textile surface, as well as on a process-stable yarn production. Varying fiber blends from used clothing need to be prepared in a process-stable manner so that they can be used as standard raw materials in the future.