Upcycling of thermoplastic polyurethane into covalent adaptable networks via chain breaking‐crosslinking strategy

Abstract

AbstractThermoplastic polyurethane (TPU), as one of the most widely used elastomers, has received rapid development, and its recycling becomes increasingly urgent. In this work, a TPU is upcycled to PU covalent adaptable networks (CANs) via chain breaking‐crosslinking strategy of being extruded with polyol and isophorone diisocyanate (IPDI) on a micro twin‐screw extruder. The carbamate exchange between the polyol and TPU breaks the chain of TPU and introduces plenty of reactive hydroxyl groups, which activates the TPU chain. Long‐chain‐branched TPU with hydroxyl groups is obtained during the chain‐breaking step and then crosslinked with IPDI to obtain highly crosslinked networks. PU‐CANs exhibit improved mechanical properties and elastic recovery rate, which is propitious to elastomers. Moreover, the crosslinked network greatly enhances the creep resistance and solvent resistance of the material. PU‐CANs maintain favorable reprocessability, suitable for screw extrusion and hot‐press processing. This work provides a simple and efficient method to upcycle TPU into reprocessable highly‐crosslinked polymers and improve the properties of polymers.