Comparative Dissolution–Precipitation Recycling of PET from Packaging and Textile Waste Using Natural Terpene Solvents

The recycling of synthetic polymers is a topic of global concern, as these materials are present in a wide range of applications under different forms. Some polymers can be used in flexible films, but also in rigid materials, and even in the form of fibers, in textiles, but their recycling is challenging in all scenarios. PET, in particular, is a common constituent of multilayer films, in combination with polyolefins, for example, but also in textiles, namely in cotton-containing blends. Dissolution-precipitation is a promising technology to handle these multipolymer materials, as it allows to selectively dissolve and recover a target polymer while leaving the remaining unchanged. While this technology has been demonstrated independently for films and for textiles, the challenges involved in transferring the process from one type of sample to another have not been addressed.

Here, we present a comparative study on the dissolution-precipitation of PET from packaging materials and from textiles, using a solvent mixture composed of Thymol and Carvacrol, both natural terpenes. We observed that the operating conditions that were reported for PET packaging could not be directly transferred to textiles. To better understand these differences, the kinetics of the dissolution of each material were analyzed through FTIR and TGA, which allow to infer that molecular weight is not the main limiting factor of the process. The impact of the antisolvent and its amount on the polymer’s precipitation was assessed, and all recyclates were characterized regarding their chemical integrity (FTIR), thermal properties (DSC), degradation behavior (TGA), and molecular weight (GPC). It was possible to achieve high recoveries of the materials, while maintaining their pristine quality.