Oxime-Urethane-Based Self-Healing Polyurethane for Achieving Complex Structures via 3D Printing

3D printing has emerged as a highly accurate, highly customizable, and low-cost fabrication method to realize structures with designed geometry. However, the integral printing of complex structures, such as suspended structures, still poses significant challenges in the most commonly used 3D printing technology-fused filament fabrication (FFF). Therefore, designing a self-healing material, segmenting the printing of complex structures, and finally assembling them into a whole by the self-healing capability are expected to resolve this issue. In this research, we successfully synthesized a self-healing polyurethane (LNPU-3) with the introduction of dynamic oxime-urethane bonds. Specifically, we employed polycaprolactone diol as the soft segment, 2,4-pentanedione dioxime as the chain extender, and 4,4′-methylenebis(phenyl isocyanate) as the hard segment. LNPU-3 exhibited outstanding mechanical properties, with a tensile stress of 8.5 MPa and a fracture toughness of 20.1 MJ/m3. Even after cyclic stretching five times at a strain of 30%, the specimen could still recover 95% of its original value. Furthermore, LNPU-3 could be fully self-healed at room temperature (25 °C) within 8 h, with a healing efficiency of 92.9%. Finally, LNPU-3 was successfully printed by using FFF and the self-healing capability of the printed samples was tested. The printing components were then assembled into a complex structure that was difficult to print as a whole. In summary, LNPU-3 is an ideal self-healing 3D printing material, demonstrating significant potential for the application of self-healing materials and the advancement of 3D printing technology.