The textile recycling field has long faced a technical pain point: polyester and spandex (i.e., elastane) blended fabrics are difficult to separate and recycle efficiently. Recently, a new achievement announced by a research team at Donghua University may offer a solution to this problem. The team developed a solvent-based chemical recycling process that can decompose polyester (PET) while retaining over 96% of cotton and spandex fibers, thereby enhancing the recycling value of blended materials. The related paper was published in the August issue of the Journal of Hazardous Materials.

The core breakthrough lies in selective decomposition. In the study, the team used a solvent system composed of ethylene glycol, potassium hydroxide, and sulfolane to completely depolymerize PET into high-purity terephthalic acid (TPA) at 80°C for 80 minutes, achieving a monomer recovery rate of about 99% and a purity of nearly 99%. Compared with traditional methods (which typically require temperatures above 120°C and may even decompose spandex simultaneously), this process achieves selective decomposition of polyester under mild conditions, avoiding damage to the fiber structure of cotton and spandex.

The team used infrared spectroscopy and density functional theory to elucidate the mechanism: sulfolane can alter the hydrogen-bonding environment around ethylene glycol, swelling the PET matrix and making it easier for active species to attack ester bonds. Under optimized experimental conditions, the cotton and spandex content in fabric samples remained above 96%, with their structures essentially intact. In addition, the process simultaneously achieves dye removal, preventing colorants from affecting the quality of recycled products.

The Donghua University team had previously developed a selective recycling technology for polyester/cotton blends (using a DMPU/ethylene glycol system). This new process further extends to elastic blended fabrics containing spandex, marking a step forward in the industrialization of blended fabric recycling. However, it should be noted that this is only validation under laboratory conditions. The research has not yet conducted commercial-scale demonstrations, nor has it verified whether the mechanical properties of the recycled fibers are sufficient for reuse in garment manufacturing. Even if the fiber structure remains intact, without considering performance loss, a true textile-to-textile closed loop cannot be achieved. This achievement from Donghua University is an exploration before oxidation, offering inspiration for regional cooperation on the "old" problem of blended fabrics that the industry is concerned about. But concerns have been raised about the later-stage comprehensive hidden costs and environmental burden of the solvent sulfolane. Although the study shows that the solvent can be reused while maintaining efficacy, the solvent recovery rate and loss rate at industrial scale have not yet been empirically verified, and the factory's energy consumption and environmental investment also need to be evaluated.

For the industry, this topic is like a catalyst. Blending has always been a "purity problem"; the spandex percentage is not high but it hinders complete recycling. The concern that polyester monomer production is premised on consumption has been dispelled; the premise is finding an economically viable process that does not "accidentally harm" spandex. The feasibility of Donghua's technical approach still has question marks to be answered. The concept of "retaining non-target waste" at the physical level while logically matching "selective dissolution" is a variable that inspires more collaborative innovation between manufacturing and research. Future experiments will indicate the realistic distance of chemical methods for restoring the grade of discarded blended products, as well as the actual industrial value enhancement brought by the removal function in the dyeing stage.

Source: Can Polyester Be Recycled Without Destroying the Spandex? · Originally published on 2026-08-26