Synthesis and self‐healing investigation of waterborne polyurethane based on reversible covalent bond

A series of self-healing waterborne polyurethane (WPU) films utilizing reversible covalent bond acylhydrazones diol (PA) as chain extender were successfully synthesized. The self-healing performance of WPU with different content of chain extender PA has been systemically characterized via cut-and-healing tests and mechanical quantitative evaluation. The film can repair cracks through acylhydrazone exchange reactions within 12 h. When the content of PA is 1.5 wt%, the WPU has the highest self-healing efficiency of 90.5%. Meanwhile, the effect of PA mass fraction on the particle size distribution, mechanical ability, crystallization, water resistance properties, and thermal stability of WPU were evaluated. With the introduction of acylhydrazone bonds, the hydrophobicity of the WPU material was enhanced, while achieving self-healing performance, which solves the problem of aging and replacement of materials. These results indicated that the self-healing WPU exhibited great application prospect as a versatile material.