One-pot depolymerization–repolymerization of PET waste into sustainable photocurable liquid copolyesters for high-performance additive manufacturing

In this work, we present a sustainable one-pot two-step approach for the depolymerization and repolymerization of post-consumer poly(ethylene terephthalate) (PET) into high-performance photocurable liquid polyesters suitable for vat photopolymerization (VP) additive manufacturing. By coupling PET waste alcoholysis with biobased diols and polytransesterification with dimethyl itaconate (DMI), novel poly(diyl itaconate-co-terephthalate) copolyesters were synthesized under solvent-free conditions using dibutyltin dilaurate as a catalyst. The resulting polyesters were formulated with reactive diluents and photoinitiators to yield printable resins with up to 22 wt% recycled PET. Mechanical and thermal analysis of 3D printed parts revealed that the incorporation of PET-derived aromatic structures enhanced stiffness, strength, and thermal stability, while the presence of itaconate units enabled high crosslink density and tunable flexibility. The optimal formulation, containing 75 wt% photocurable polyester containing 15.3% recycled PET, achieved a Young’s modulus of 1.4 GPa and flexural strength of 54 MPa, representing the highest performance reported to date for itaconic acid-based 3D printable resins. This integrated approach represents a significant green advance by combining solvent-free processing, renewable feedstocks, and post-consumer PET valorisation. The sustainability of the materials was further validated using the Sustainable Formulation Score (SFS), placing the top-performing resins in the top 10% of benchmarked systems.