Kinetics-Guided Controlled Oligomeric Depolymerization of PET for Tailored High-Performance Polymer Upcycling

Growing concerns over polyethylene terephthalate (PET) waste have underscored the urgent necessity for scalable and sustainable recycling strategies. This study proposes a kinetics-guided depolymerization and repolymerization strategy to upcycle PET into high-performance thermoplastics. PET depolymerization was conducted using 1,4-cyclohexanedimethanol (CHDM) as both solvent and reagent, without external catalysts, leveraging the unique structure of CHDM to facilitate effective transesterification under mild conditions. A population balance equation-based kinetic model was employed to precisely control the oligomer molecular weight distribution. The depolymerization proceeded via a predominantly random chain scission mechanism with an activation energy of 76.08 kJ∙mol −1 . The CHDM-derived well-defined oligomers were directly repolymerized into recycled thermoplastic polyester elastomers and recycled glycol-modified PET, which achieved mechanical properties comparable to or surpassing those of commercial virgin materials. Furthermore, the kinetic model was validated in a 15 L reactor, demonstrating its efficacy in guiding scalable process design. By eliminating the esterification and pre-polycondensation steps, the process simplified operation and reduced energy consumption, aligning with existing polycondensation infrastructure. This catalyst-free streamlined route offers both molecular-level tunability and industrial scalability, representing a viable pathway for sustainable PET upcycling for a circular polymer economy.