Hydrogenating Polyethylene Terephthalate into Degradable Polyesters

Abstract

The recycling and upcycling of polyethylene terephthalate (PET), the most widely used polyester plastic globally, has attracted growing attention concerning its disposal as non-degradable waste in the natural environment. Transforming end-of-life PET into (bio)degradable polyester offers a novel approach to managing its waste. In this study, we introduce a simple process capable of converting waste PET into degradable polyester, polyethylene terephthalate-polyethylene-1,4-cyclohexanedicarboxylate (PET-PECHD), by partly hydrogenating the aromatic rings (x) into aliphatic ones (y). The polyesters with variable x/y compositions ranging from 100/0 to 0/100 can be achieved, and the molecular weight (Mw) can be maintained when x/y >87/13 due to the nonobvious depolymerization. Pronounced depolymerization would occur with deeper hydrogenation, which generates a blend of PET-PECHD and polyethylene-1,4-cyclohexanedicarboxylate (PECHD) with lower Mw, and finally a single-type polymer PECHD. The PET-PECHD demonstrates comparable thermal stability and mechanical strength compared to PET, along with superior extensibility, barrier properties, and (bio)degradability in acidic, alkaline solutions, and moist soil. This research highlights the potential for cost-effective, large-scale production of degradable polyester from real-life plastic waste.