Chemical recycling of poly(butylene terephthalate) into value-added biodegradable poly(butylene adipate-co-terephthalate)

Abstract

We present here a high value-added strategy for the chemical recycling of the engineering plastic poly(butylene terephthalate) (PBT) into biodegradable poly(butylene adipate-co-terephthalate) (PBAT) copolyesters. Cyclodepolymerization of postconsumer PBT in dilute solutions affords cyclic oligo(butylene terephthalate)s (COBTs), which can be further used as monomers together with poly(butylene adipate) (PBA) diols for the synthesis of PBAT via a cascade polycondensation-coupling ring-opening polymerization (PROP) method. Due to the adequate transesterifications during PROP, the adipate and terephthalate units are randomly distributed in the polyester main chains, similar to PBATs synthesized via typical condensation polymerization. The properties of the obtained PBAT can be flexibly tuned by adjusting the feeding ratio of COBTs and PBA diols. The subtle combination of the cyclodepolymerization method with PROP provides a new avenue for the chemical recycling of aromatic polyesters into value-added biodegradable copolyesters.