Microwave-Assisted Closed-Loop Chemical Recycling of Multiblock Poly(ethylene terephthalate)-Based Copolyesters

Abstract

Thermoplastic copolyesters (TPCs) are segmented multiblock materials widely used in high-performance applications due to their excellent mechanical strength, thermal stability, and processability. Poly(ethylene terephthalate) (PET) can serve as the rigid semicrystalline segment, enabling injection molding and large-scale industrial production, reaching hundreds of kilotons annually. The growing volume of postconsumer TPC waste highlights the urgent need for efficient recycling strategies. This work demonstrates a rapid and straightforward chemical recycling route using microwave-assisted methanolysis and glycolysis to depolymerize TPCs. The recovered products were subsequently repolymerized via sequential one-pot transesterification and polycondensation on both small (similar to 3 g) and large (similar to 40 g) scales to produce recycled PET-based copolyesters. Molecular, thermal, and mechanical properties were evaluated using 1H and 13C NMR spectroscopy, size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), and tensile testing. The recycled materials exhibited properties nearly identical to those of the original copolyesters, demonstrating a promising pathway for the circular reuse of complex polymer waste.