Upcycling of Polyethylene Terephthalate to Continuously Reprocessable Vitrimers through Reactive Extrusion

Vitrimers are expected to combine features of thermosets and thermoplastics but their continuous reprocessing is still a challenge; poly(ethylene terephthalate) (PET) has been widely used in our daily life, while its cross-linking upcycle contradicts with processability. Herein, we combined polyol with a tertiary amine structure and diepoxy to transform PET to continuously reprocessable vitrimers through an industrial twin-screw extruder. The cross-linking of PET was determined by swelling and rheology experiments, and the vitrimer feature was characterized by stress relaxation and oscillatory frequency sweep experiments. Creep resistance and mechanical properties of PET vitrimers were improved greatly relative to neat PET. Meanwhile, PET vitrimers exhibited excellent reprocessability via compression, extrusion, and injection molding suitable for industrial production. According to this work, any thermoplastics containing ester bonds should be able to be upgraded to vitrimers for additional advantages such as creep resistance, dimensional stability, insolubility, etc., without sacrificing the original processability.