Catalyst‐ and Solvent‐Free Upcycling of Poly(Ethylene Terephthalate) Waste to Biodegradable Plastics

Poly(ethylene terephthalate) (PET) is an important polymer with annual output second only to polyethylene. Due to its low biodegradability, a large amount of PET is recycled for sustainable development. However, current strategies for PET recycling are limited by low added value or small product scale. It is urgent to make a breakthrough on the principle of PET macromolecular reaction and efficiently prepare products with high added value and wide applications. Here, the catalyst‐ and solvent‐free synthesis of biodegradable plastics are reported through novel carboxyl‐ester transesterification between PET waste and bio‐based hydrogenated dimer acid (HDA), which can directly substitute some terephthalic acid (TPA) units in PET chain by HDA unit. This macromolecular reaction can be facilely carried out on current equipment in the polyester industry without any additional catalyst and solvent, thus enabling low‐cost and large‐scale production. Furthermore, the product semi‐bio‐based copolyester shows excellent mechanical properties, regulable flexibility and good biodegradability, which is expected to substitute poly(butylene adipate‐co‐terephthalate) (PBAT) plastic as high value‐added biodegradable materials. This work provides an environmental‐friendly and economic strategy for the large‐scale upcycling of PET waste. An optimal approach without the need for additional catalysts or solvents for the upcycling of poly(ethylene terephthalate) (PET) waste is reported. Specifically, bio‐based hydrogenated dimer acids are found to directly convert PET bottles into biodegradable copolyesters suitable for agricultural mulch films. This work provides an environmentally friendly and cost‐effective strategy for the large‐scale upgrading and reprocessing of PET waste.