Triple Roles of Thermoplastic Polyurethane in Toughening, Accelerating and Enhancing Self-healing Performance of Thermo-reversible Epoxy Resins

Abstract Cracks in polymers can be healed by endowing materials with self-healing performance. Cracks in epoxy resins containing thermo-reversible Diels–Alder bonds (EP-DA) can be self-healed via different heat treatments. However, EP-DA exhibits the disadvantages of brittleness and poor impact resistance yet as that existed in the common epoxy resins, and which limits the application of thermo-reversible self-healing epoxy resins. Herein, thermoplastic polyurethane (TPU) was introduced into EP-DA for the purpose of reducing the brittleness and improving the impact resistance of EP-DA. Meanwhile, it was expected that the self-healing performance of EP-DA could not be affected evidently. Results showed that the impact resistance of EP-DA had been improved greatly as expected upon TPU modification. More importantly, instead of affecting the self-healing performance of EP-DA, the self-healing speed of EP-DA was accelerated evidently by the incorporation of TPU. On the other hand, the healing efficiency of EP-DA was also enhanced markedly. In fact, TPU-modified EP-DA was repaired by dual actions of thermo-reversible DA reaction and thermal movement of thermoplastic polymer chains. In addition, TPU-modified EP-DA could also be healed for many damage-repair cycles. Therefore, thermoplastic polyurethane played a triple role as toughening, accelerating and enhancing self-healing performance of thermo-reversible epoxy resins. Graphic Abstract Thermoplastic polyurethane (TPU) was introduced into thermo-reversible self-healing epoxy resins (EP-DA) successfully. As a result, the brittleness was reduced and the impact resistance of EP-DA was improved greatly. What’s more, instead of affecting the self-healing performance of EP-DA, the self-healing speed of EP-DA was accelerated evidently while the self-healing efficiency of EP-DA was enhanced markedly. Therefore, TPU played a triple role as toughening, accelerating and enhancing self-healing performance of thermo-reversible epoxy resins.