Simple process for separation and recycling of nylon 6 and polyurethane components from waste nylon 6/polyurethane debris

Abstract

The nylon 6 (PA6)/polyurethane (PU) debris produced during the sanding process would result in a serious resource waste and environmental hazard if disposed of inappropriately. Therefore, this study proposed a simple process for separating and recycling PA6 and PU components of PA6/PU debris. Results revealed that the instantaneous dissolution of PU in N,N-dimethylformamide was independent of temperature and time but related to the quantity of the solvent. Further investigation showed that 43.2% of waste PA6/PU debris was dissolved at room temperature, with pulp density of 10% and within 10 minutes, indicating that PA6 and PU could be quickly separated from the waste PA6/PU debris. In addition, proton nuclear magnetic resonance indicated that the dissolved PU could be recovered by selective precipitation-stripping using an equal amount of deionized water. Moreover, the chemical structure analysis disclosed that the PU in PA6/PU debris should be polyether PU synthesized by reacting with methylene diphenyl diisocyanate and polyether polyols. Besides, the stable chemical structure and thermal properties of separated samples observed from differential scanning calorimetry and thermogravimetry results confirmed that the recycling products could be reused as recycled plastic materials.

Self-assembled bio-based coatings for flame-retardant and antibacterial polyester–cotton fabrics

“…In the ATR-FTIR spectra of the coated CT fabric, three characteristic peaks were observed at 1406, 1708, and 1248 cm −1 , which can be attributed to the C=N, C=O, and P=O groups, respectively. 22–25 In addition, the additional peak observed at 3306 cm −1 can be attributed to the N-H bending and O-H stretching vibrations, and that observed at 2912 cm −1 can be ascribed to the stretching vibration of –CH3 groups, while the peaks observed at 866 and 708 cm −1 can be attributed to the stretching vibration of the benzene ring. 26,27 Furthermore, the peak observed at 1096 cm −1 can be ascribed to the Si-O stretching vibration of KH550, which indicates that the KH550 was successfully deposited on the coated CT fabrics.…”

Selective chemical disassembly of elastane fibres and polyurethane coatings in textiles

“…Next, dissolution of elastane from pieces cut from black nylon tights (73% PA, 27% elastane) obtained at a local shop was performed. 41–43 From 5.10 g of the tights, 61 wt% of polyamide leftover fabric and 33 wt% of elastane extract were recovered (Scheme 2b). FTIR analysis suggested that the elastane had been effectively removed from the polyamide matrix (see ESI-9† for full details).…”

“…38–40 Elastane can accordingly be removed from either nylon or cotton fabrics by applying high-boiling polar amide solvents such as DMF (Scheme 1b, right). 41–43 This technology represents a useful operation for the removal of elastane from major fibre components, which can subsequently be spun into new yarns and reused in fabrics. However, the removal of the generally undesirable DMF is energy intensive and the quality of the remaining fibre is often compromised as judged by the degree of depolymerisation and highly dependent on the choice of solvent.…”

Recent advances in recycling technologies for waste textile fabrics: a review

“…The technology focuses on using a subcritical water reactor as a medium to break down the textile waste at temperatures between 105 C and 190 C. Palme et al 135 investigated the separation of cotton and PET from mixed textiles using a straightforward process of 5-15 wt.% NaOH in water and temperature between 70 C and 90 C for the hydrolysis of PET, resulting in TPA and EG and recovered cotton fibers. Gong et al 141 developed a simple method to dissolve PU in N,N-dimethylformamide in a study to remove PU from polyamide 6 66/PU blended fabrics. The recycling products could be reused as recycled plastic materials.…”