Preparation and properties of polyurethane filaments recycled by polyethylene terephthalate via alcoholysis reaction with dry spinning

To solve the problem of environmental protection, the alcoholysis by-products of waste polyethylene terephthalate bottles were utilized, in a two-step process, to create a spinning solution, which was then employed to produce polyurethane filament (PUF) through dry spinning. The chemical composition of the recycled PUF (rPUF) was analyzed using Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Additionally, the mechanical properties and dyeability of rPUF were characterized. The heat setting and heat resistance of rPUF were also studied. The results indicate that rPUF exhibited lower crystallinity than conventional PUF. The rPUF incorporated a higher proportion of small molecular components. As a result, compared with PUF, when stretched to 300% for a fifth cycle, the tensile strength of rPUF was significantly improved, with a maximum increase of 39.2%. Conversely, the breaking strength and elongation at breakage of rPUF decreased, with the breaking strength showing a reduction of 24.8%. The dye uptake of rPUF was better than that of PUF, but the heat resistance under alkaline conditions was poor. These rPUFs have enhanced tensile strength and excellent dyeing properties, indicating their potential use in various applications.