Toward Green Manufacturing of Low-Cost, Robust Unsaturated Polyester Resin from Waste PET Glycolysis Products

Recycling of plastics is an effective solution to address solid waste pollution. Developing environmentally friendly pathways and more efficient product recycling solutions is crucial. Here, we proposed a method for the full process of upcycling of poly(ethylene terephthalate) (PET) glycolysis products into unsaturated polyester resin (UPR). Specifically, the PET glycolysis employed tetrabutyl titanate (TBT) as a catalyst and with a low catalyst dosage (0.25 wt %), achieving a 97.3% PET conversion at 190 °C for 2.5 h. The generated monomers and oligomers, together with excess alcoholysis agents, were used as raw materials for preparing UPR without purification. Furthermore, by adjustment of the formulation of UPR, its viscosity, gel time, exothermic peak, and mechanical properties were regulated. The final product exhibited a tensile strength of 41.5 MPa and a Young’s modulus of 17.1 GPa as well as satisfactory acid–base resistance. Moreover, techno-economic analysis confirmed that the upgraded PET recycling strategy demonstrated certain economic benefits and industrial application prospects.