One stone kills two birds: Novel recycled fiber spinning engineering for one-step yarn reinforcement and clean dyeing.

Low recycling rates of textile waste and high dyeing energy consumption are two significant challenges for the textile industry in response to the call for Carbon Neutrality. In view of this, we propose a "one stone kills two birds" strategy by developing novel nanofiber composite spinning engineering for the simultaneous reinforcement and dyeing of recycled poor-fiber yarns. Adhesive beaded polyvinylpyrrolidone (PVP) nanofibers were introduced onto the recycled fiber surface to enhance fiber welding friction and modulate the fiber interfacial slippage effect at the carding stage. The coefficients of dynamic/static friction of the recycled fibers were enhanced by 133.33%/84.21%, while the strength of recycled yarns increased by 67.02%. Meanwhile, dye-loaded polyacrylonitrile (PAN) nanofibers were concurrently introduced into recycled yarns for one-step water-free coloring, with the average dyeing energy consumption of the yarn reduced by 93.20% and the dyeing cost decreased by 43.76%. Furthermore, general models for the reinforcement and clean dyeing of recycled yarns were proposed in this work. Colored recycled cotton fabrics were manufactured on spinning and fabricating lines, demonstrating that our composite spinning system eliminates the need for separate dye baths and harsh conditions and has considerable potential for scalable green waste cotton recycling engineering.