Investigation of the chemical and thermomechanical stability of poly(ethylene terephthalate) during chemical separation from elastane-containing textile waste

Poly(ethylene terephthalate) (PET) fibers dominate the textile market, accounting for 57% of global fiber production, yet its recycling is hindered by the presence of elastane in textile blends. This study investigates the stability of PET in the chemical separation process that selectively removes elastane using a solvent mixture of bio-based 2-methyltetrahydrofuran (2-MeTHF) and dimethyl sulfoxide (DMSO). Unlike traditional methods that often rely on harsh conditions and toxic solvents, this process is mild, achieving efficient separation at room temperature within 15–30 min. In a case study involving a textile blend containing ∼ 6% elastane, two cycles of treatment (1 g of textile in 20 mL of solvent blend) successfully removed elastane almost completely. Comprehensive analyses confirm the stability of the recovered PET fibers with no chemical alterations detected by Fourier-transform infrared spectroscopy (FTIR). Minimal changes in number- and weight-average molar masses were observed (M n decreased from 12.4 to 11.7 kg mol −1 , M w from 24.7 to 23.8 kg mol −1 ; Ð remained ≈ 2). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) reveal consistent thermal behavior (T m ≈ 255 °C; crystallinity ≈ 29%), while mechanical testing shows preserved tenacity (35 cN/tex) and elongation at break ( ≈ 26%). This method addresses a critical challenge in textile recycling by overcoming the barriers posed by elastane, ensuring the recovered PET meets quality requirements for respinning and offering a solution that contributes to the advancement of circular economy practices. • Elastane ( ∼ 6%) removed from textile blend in two 30-min cycles at room temperature. • Treated PET showed minimal decreases in (M w 24 . 7 → 23.8, M n 12 . 4 → 11.7 kg mol −1 ). • Thermal and mechanical properties preserved (T m ≈ 255 °C, X c ≈ 29%, tenacity ≈ 35 cN/tex). • Solvent of 70% 2-MeTHF and 30% DMSO enables sustainable fiber-to-fiber recycling.