Mechanical performance and sustainability of plied silk-waste yarns for outerwear

The mechanical performance and sustainability of plied yarns produced from degummed silk waste were evaluated, with particular attention to their suitability for outerwear applications. Among the three silk waste types examined, Sample 1 (cocoon unwinding waste) possessed the finest and most uniform fibers (diameter 11.5–12 μm, fineness less than 1 dtex), establishing it as the preferred material for yarn production. Mechanical testing of machine-spun single, two-ply, and four-ply yarns indicated that two-ply yarns achieved a breaking stress approximately 40% higher than that of four-ply yarns. Additionally, two-ply yarns exhibited a higher modulus of elasticity and lower extension. The optimal yarn structure was identified as a two-ply yarn (component count: 34.2 tex; 638 turns per meter), which demonstrated the highest elastic recovery under cyclic loading up to 5% extension. Thermal shrinkage tests revealed that higher twist levels produced greater shrinkage, which is significant for post-processing stability. Scanning electron microscopy confirmed the smoothness and uniformity of Sample 1 fibers, correlating with the enhanced mechanical properties observed in the yarns. In summary, two-ply silk-waste yarns derived from cocoon unwinding waste represent an effective and sustainable alternative for high-performance outerwear. Further research is recommended to assess the scalability of this process and the potential of other silk waste types for similar applications.