Effect of Heat-Treatment on Self-healing and Processing Behavior of Thermally Reversible Polyurethanes

Given its thermal reversibility, high yield, and minimal side reactions, the Diels–Alder (DA) reaction is a particularly desirable technique for the preparation of polymeric materials with heat-stimulated self-healing properties. A linear self-healing polyurethane containing thermally reversible DA bonds (PU-DA) was developed in this study. Results revealed that the introduction of DA bonds conferred outstanding mechanical property and thermal reversibility to PU-DA films. Thus, the as-prepared PU-DA films demonstrated excellent self-healing performance. The self-healing behavior of the PU-DA films under various heat treatments was examined through qualitative observation and quantitative measurements. The PU-DA underwent self-repair through the combination of two healing actions, i.e., the thermal movement of molecular chains and the thermally reversible DA reaction. Moreover, the self-healing behavior of the PU-DA was repeatable, and the PU-DA continued to present high strength even after undergoing three damage–repair cycles at the same site. In addition, the as-prepared PU-DA exhibited excellent macro-scale self-healing behavior, and it endowed the PU-DA presented reprocessing performance. The PU-DA can be recycled given its excellent self-healing and outstanding reprocessing performances.