Eco-friendly fabrication of self-healing robust waterborne polyurethane based on dual dynamic networks for metal corrosion protection

In the face of ubiquitous corrosion threats, self-healing coatings have drawn much attention due to their potential to prolong material lifespan and environmental benefit. However, it is a significant challenge to balance their mechanical, self-healing and anti-corrosion capacity. Herein, we present a self-healing WPU (WPUSS) coating by combination of reversible disulfide bond, acylhyrazone bond and thermosensitive hydrogen bond together. The dual dynamic networks are constructed by the chemical crosslinking of acylhydrazone and the physical Hbonding network between acylhydrazone, urethane and urea bonds, which contribute efficient self-healing, ultrahigh strength and remarkable anti-corrosion performance. The prepared WPUSS-P4 polymer exhibits the high yield stress of 14.6 MPa and high stress at break of 20.9 MPa, as well as 93 % self-healing efficiency. Furthermore, WPUSS-P4 coating displays a high and durable corrosion protection effect after 240 h of EIS test in 3.5 wt % NaCl solution and 120 h of salt spray test in 5 wt% NaCl solution. The intact and self-healing WPUSS-P4 coatings have almost the same characteristics during EIS test, exhibiting a nearly 100 % corrosion resistance recovery. This highly reliable self-healing WPU provides a promising strategy for developing the sustainable and environmentally friendly anti-corrosion materials.