Enzymatic recycling of heat and intellige mixture

Polyester plastics, commonly found in synthetic textiles and plastic components of domestic devices, are notoriously difficult to recycle. In a study recently published in the Proceedings of the National Academy of SciencesResearchers from France have unveiled an intelligent method to decompose polyester waste into reusable construction blocks using heat and taking advantage of residual catalysts integrated in plastic during the manufacturing process, eliminating the need for tedious sorting.

The sorting of plastic waste is recommended before elimination to facilitate the recycling process. The recycling of Pet or Polyethylene Téréphtaplate, which is widely used in bottles, textiles, packaging and engineering plastics, considerably benefits from this practice. Recyclers simply need to collect, separate it from other waste and decompose it via a depolymerization catalyzed by monomers enzymes, which can then be used for the next batch of pet products.

This form of recycling becomes particularly difficult with polyesters, such as terephththylene terephthylene (PTT) and polybutylene Téréphtalatus (PBT), as well as PET fibers. When used in consumer products, these plastics often contain a mixture of different monomers and additives such as dyes or plasticizers, which makes waste difficult to sort and separate. In addition, their rigid crystalline structures prevent enzymes used in recycling from decomposing plastic, because polymer chains are packed too closely and are not accessible.

In this study, the researchers reported a new technique to degrade this plastic waste, which intentionally includes the mixture of various types of polyester waste in controlled proportions, then melt by increasing the temperature to 270 ° C. Residual catalysts, such as antimony trioxide, left from the polyester manufacturing process, allowed transesterification – a chemical reaction in which the alcoholic group Replaced by an alcohol – by perforating copolymers by random network structures.

For polyester waste rich in rapid crystallization polymers such as PBT, the melting transesterification failed to provide the desired results. To counter this, the researchers introduced vitimony – the addition of an epoxy reticulation agent to the mixture – to slow the crystallization time. These processes gave a reactive mixture that crystallized at a slower rate when cooled in ice baths, resulting in a polymer structure with enzymatic attack.

The solid material obtained after the cooling process was blurred and treated with the same enzymes used to recycle semi-cristal PET bottles. The result was high -quality monomers construction blocks adapted to the manufacture of new polyester products.

The researchers stressed that the mixture of non -woven TEP waste with PBT increased the 20% enzymatic depolymerization yield for PET and 1% for 90% PBT as a mixture. Although counter-intuitive, this study establishes that mixture rather than sorting could be a more viable and less tedious approach to recycle polyester waste.

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