Degradable Waterborne Polyurethane with Flame Retardancy and High Mechanical Strength via Synergy of Hydrogen Bonds

Waterborne polyurethane (WPU) with degradability is critical to the environment. Especially, degradable WPU with high mechanical strength and flame retardancy features various important industrial applications, while the increased flame retardancy often leads to reduced mechanical strength. Herein, we report the simultaneous realization of degradability, flame retardancy, and high mechanical strength into one design. The tensile strength of degradable WPU is up to 39 MPa and can be tuned by the ratio of soft segments. The strong synergistic hydrogen bond interactions of different components confirmed by FTIR and XPS as well as molecular dynamics simulation are responsible for the excellent mechanical strength. Moreover, WPU achieves the highest "V0" level of flame retardancy. The simultaneous realization of the stress of 35 MPa and a limiting oxygen index of 27.55% is obtained by changing the flame retardant contents. Importantly, WPU possesses degradability with a mass loss rate of 37% after natural burial in soil for 3 months. The dense WPU coatings can be adhered to different substrates and also have good anticorrosion ability. This work provides a promising strategy for high-performance biodegradable materials and expands the industrial application of polyurethane.