From Deconstruction to Fiber-Grade Polymers: Closed-Loop Recycling of Mixed Textile Waste

The environmental burden of textile waste has increased with rising consumption and widespread use of blended synthetic fabrics. Most post- consumer textiles are landfilled or incinerated, leading to loss of valuable polymeric resources and greenhouse gas emissions. PET, Nylon 6, and Nylon 66 form a significant portion of this waste stream, yet their recovery is hindered by fiber blending, contamination, and degradation. This work presents a closed loop recycling approach for mixed textile waste through polymer segregation, chemical depolymerization, monomer purification, and repolymerization into high-quality fibers. Polyester- and polyamide-rich fractions are isolated and depolymerized into monomers including terephthalic acid (TPA), ethylene glycol (EG), caprolactam, and hexamethylenediamine/adipic acid. Achieving polymerization-grade monomers purity is critical, as residual dyes and undesired degradation products impact polymerization and final polymer properties. Purification strategies including recrystallization, adsorption, and distillation are evaluated to obtain monomers with sufficient purity. Recovered monomers are benchmarked against model counterparts using compositional and spectroscopic analysis to quantify impurity effects. After purification, recovered monomers are repolymerized into PET, Nylon 6, and Nylon 66, and compared to model polymers. Data shows that optimized purification results in polymers with properties comparable to model polymer systems. Specially, regenerated polymers achieve similar molecular weights, thermal stability, and tensile performance after fiber spinning if critical monomer purity thresholds are met. Techno-economic analysis (TEA) and life cycle assessment (LCA) inform the influence of monomer purification as a cost driver while demonstrating reduced greenhouse gas emissions and energy demand relative to virgin production. This work demonstrates a scalable pathway for converting mixed textile waste into valuable, high-performance polymer fibers, emphasizing the central role of monomer purity in achieving circularity for synthetic textiles.