Effect of failure modes on healing behavior and multiple healing capability of self-healing polyurethanes

Materials can suffer from different damages in actual application. Consequently, diversified failure modes can be caused, while different failures may have unalike repairing effect. Thereupon, it is quite important of exploring the effect of failure modes on the repairing behavior of self-healing materials. Herein, a kind of thermoplastic polyurethane containing Diels-Alder bonds (PU-DA) has been synthesized successfully. Based on the dual actions of thermo-reversible Diels-Alder reaction and molecular movement, the as-prepared polyurethane exhibits excellent self-healing performance. The repairing behavior of polyurethanes with different failure modes has been investigated both qualitatively and quantitatively. Results show that polyurethanes with various cracks can be repaired. However, PU-DA film with shallower crack exhibits a high healing efficiency as compared to that with deeper crack at the similar heat treatment. Meanwhile, polyurethane has multiple healing capability and cracks can be caused and repaired repeatedly. Additionally, PU-DA fragments can recombine together as a whole even after destroyed by tearing, indicating PU-DA also exhibits outstanding reprocessing capability. The research can lay foundation for realizing the favorable repairing of various failure modes, and further promote self-healing materials and technology applied into practice.