# Opportunities and Limitations in Recycling Fossil Polymers from Textiles
## Recycling Fossil Polymers
### The Case of Elastan in Mixed Polymer Fabrics Recycling  
Natural fabrics have good moisture absorbency and heat isolation but also have poor wrinkle resistance and elasticity. Therefore, synthetic fibres are usually mixed with natural fibres to obtain proper garment properties. Among them, elastane (also known as spandex) is a typical synthetic elastic fibre that exhibits a highly reversible extension of 400-800% [118]. This capacity has become the prerequisite for fashionable or functional apparel such as leisurewear, underwear, outer clothing, and sportswear. The worldwide consumption of Elastane has grown by 30-40% per year. It is present in fabric mixed with cotton as a component in 2-5%, but in combination with PET or PA it can reach up to 20% by weight of the fabric. Generally, it is used in knitted fabrics, in particular in plated plain knitted fabric [20]. Thus, the presence of elastane can make difficult the recycling phase of several fabrics. The necessity of revealing and quantifying elastane in fabric was considered by different authors. [PERSON] et al. [119] identified the thermogravimetry coupled with the infrared analysis of evolved gases as a good methodology to quantify elastane in a sample. Very recently, [PERSON] et al. [120] deepened the use of thermal methodologies for elastane quantification, considering several samples of fabric including PA, PET, cotton, wool and elastane, and proposed a methodology based on DSC analysis that they suggest as an alternative to the use of the EN ISO 1833-20:2018, based on extraction of elastane with solvent. The use of near-infrared detection is generally considered fundamental not only for quantification but also for automatic on-line sorting of fabrics scraps [68]. Regarding the recycling of fabric containing elastane, mechanical recycling was attempted by [PERSON] et al. [121], who adopted for PA/elastane fabrics a simple process using only heat and ethanol, which involved heat treatment at 220 \({}^{\circ}\)C for 2 h under atmospheric pressure followed by washing with ethanol. The authors stated that the process was able to remove essentially all the spandex component from the blended fabric, resulting in a fabric consisting mainly of PA yarns. [PERSON] et al. [122] removed in a preliminary step the elastane by extraction with DMF solvent (solvent ratio 50:1 in mass) at 70 \({}^{\circ}\)C for 4 h, then carried out a thermal treatment at 220 \({}^{\circ}\)C followed by washing. The obtained material was successively compounded in a Brabender discontinuous mixer and characterized. Rheological measurements showed that viscosity of treated fabric samples was lower than that of untreated fabric composites, as an effect of the spandex removal after treatment. The recycled plastics from treated fabrics exhibited good mechanical properties with a tensile strength of 46.6 MPa and a Young's modulus exceeding 2.4 GPa, but with a decreased elongation at break. However, the addition of 20% of recycled material to pure polyamide resulted in a material with a very similar mechanical behavior with respect to pure PA.  
T-shirts with 95% cotton and 5% elastane were selected to be dissolved in H\({}_{2}\)SO\({}_{4}\) aqueous solution, NaOH/urea aqueous solution, or LiCl/DMAc solution. Regenerated cellulose films were obtained from these three solvent systems, and their structures were studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). All three solvent systems could effectively dissolve the cellulose fibres, while resulting in different elastane components. The film obtained in NaOH/urea aqueous solution contained large undissolved elastane fibres, and its mechanical properties were weaker than the other two samples.