Upcycling PET waste: a sustainable path to closed-loop recyclable polymers

A new study introduces an innovative method to address polymer waste and advance sustainability. Researchers Sourabh Singh and Ramkrishna Sarkar developed a closed-loop recycling strategy that upcycles polyethylene terephthalate (PET) waste into poly(ester-amide) polymers with excellent material properties. By integrating chemically recycled PET and bio-based resources, this approach offers significant potential for the plastics industry.

The process involves synthesising a diol monomer, bis(2-(2-hydroxyethoxy)ethyl)terephthalamide (BHEETA), from PET waste. This monomer is then combined with renewable fatty acid-derived diesters under solvent-free melt transesterification conditions. The chain length of the diesters, ranging from fourteen to eighteen backbone carbons, controls polymer properties such as crystallinity, thermal stability, melting temperature, and crystallisation temperature.

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Learn more about current approaches to produce coatings in a more environmentally friendly way and to give coated products a longer service life in the EC Tech Report Sustainability. In addition, its handpicked content dives deeply into the European Green Deal, its key points and main purpose as well as consequences for the coatings industry.

Closed-loop Recycling: A Milestone in Polymer Sustainability

What sets this research apart is its focus on achieving a circular polymer economy. The poly(ester-amide) can be chemically degraded back into its monomers, which are easily purified and recovered at a yield exceeding 90 %. These recovered monomers can be reused to regenerate polymers with nearly identical material characteristics, closing the recycling loop.

This study marks the first successful attempt to create closed-loop recyclable poly(ester-amide) derived from PET waste and bio-based feedstocks, paving the way for sustainable polymer production and waste management strategies.

Source: Singh, S. & Sarkar, R. Upcycling of polymer waste to closed-loop recyclable polymers. Polym. Chem., 2025.

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