Recyclable and Reprocessable Thermosetting Polyurea with High Performance Based on Diels-Alder Dynamic Covalent Crosslinking

The thermosetting polyurea possessed high tensile strength and elongations at break due to strong intermolecular interactions, but their recycling and reprocessing remains a great challenge, especially at a temperature below 100 °C. Herein, the novel crosslinked polyurea with excellent recycling and reprocessing properties has been prepared by introducing the Diels-Alder dynamic covalent bond. The chemical structure, thermal mechanical properties and reprocessing performance of the crosslinked polyurea were investigated. The prepared polyurea has low relaxation time of ∼4 min at 80 °C for facile reprocessing. The tensile strength and elongation at break of crosslinked polyurea could reach 15.24 MPa and 529.2%, respectively, and its mechanical properties remain almost unchanged even after repeated processing. This work has realized the recycling of crosslinked polyurea, which has huge potential applications in environmental protection and recycling of waste plastics.