Repolymerize

Plastic pollution has become an increasingly pressing global concern, with large amounts of plastic waste reaching landfills, oceans, and ecosystems. A diverse range of plastic polymers used for the production of textiles, bottles, packaging, and numerous other sectors end up accumulating in the environment, due to the still prevalent linear economy model – “take-make-dispose”.
Polycotton, a blend of polyethylene terephthalate (PET) and cotton, exacerbates this pollution dilemma. Not only is the polycotton industry largely responsible for the increase in global greenhouse gas emissions, but also polycotton clothings shed microplastics during laundering, contributing to water pollution and marine ecosystem degradation. Thus, addressing the issues of PET waste and polycotton pollution requires innovative recycling strategies. While mechanical recycling has been the most common approach in plastic waste management, its efficiency is often limited by the contamination and loss of the end material. Chemical recycling offers a promising alternative, capable of breaking down complex polymers into their constituent monomers for subsequent reuse. This approach not only mitigates the loss of material quality inherent in mechanical recycling but also enables the recovery of high-purity components.
Considering these challenges, the objective of this project was to explore an efficient method to recover the fundamental building blocks of PET polymers – dimethyl terephthalate (DMT) and ethylene glycol (EG) – by vacuum distillation and recrystallization processes. This was done after a chemical recycling depolymerization reaction (methanolysis) was applied in the samples by an external partner from Groningen Rijksuniversiteit. The resulting products were analyzed by diverse techniques to assess their respective purities. Results for DSC, IR and H-NMR spectroscopy of the DMT recovered showed close proximity to what was expected based on literature, indicating a good purity of the recovered chemical. Furthermore, the EG reclaimed from the samples, although with a very low yield/recovery, presented an acceptable purity ranging from 74-83%, based on RI analysis results.

Polycotton textiles are fabrics made from cotton and polyester. It is used in many textile applications such as sporting cloths, nursery uniforms and bed sheets. As cotton and polyester are quite different in their polymer nature, polycotton textiles are hard to recycle and therefore mostly incinerated. Incineration of discarded polycotton, and substitution by virgin polycotton, create a significant environmental impact. However, textile manufacturers and brand owners will become obliged to apply recycled content in clothing from 2023 onwards. Therefore, the development of more sustainable recycling alternatives for the separation and purification of polycotton into its monomers and cellulose is vital. In a recently approved GoChem project, it has been shown that cotton can be separated from polyester successfully, using a chemical recycling process. The generated solution is a mixture of suspended and partially decolorized cotton (cellulose) and a liquid fraction produced from the depolymerization of the polyester (monomers). A necessary further step of this work is the investigation of possible separation methods to recover the cotton and purify the obtained polyester monomers into polymer-grade pure products suitable for repolymerization. Repolymerize is a new consortium, composed of the first project members, plus a separation and purification process group, to investigate efficient and high yield purification steps to recover these products. The project will focus on possible steps to separate the suspended fraction (cotton) and further recover of high purity ethylene glycol from the rest fraction (polyester depolymerization solution). The main objective is to create essential knowledge so the private partners can evaluate whether such process is technologically and economically feasible.