Robust, self-healing, anti-corrosive waterborne polyurethane urea composite coatings enabled by dynamic hindered urea bonds

To meet the increasing concerns for health, safety, and the environment, traditional solvent coatings are gradually replaced by their waterborne counterparts and the development of robust and self-healing waterborne polymers is showing important application significance. Herein, waterborne polyurethane urea composite coatings (WPUU) with dynamic hindered urea bonds are reported. The dispersion of WPUU synthesized with hindered amine as the chain extender has a smaller particle size. The mussel-inspired polydopamine modification was applied to improve the dispersion and interfacial interactions of carbon nanotubes (CNTs) in the WPUU matrix. Due to the dynamic reversibility of the hindered urea and abundant hydrogen bonding, the resulting WPUU-2T2B can achieve self-healing at 70 °C, also showing good mechanical toughness, the tensile strength of 34.0 MPa and elongation at break of 530 %. After adding the modified CNTs, 10%PDA@CNTs/WPUU demonstrates the tensile strength of 22.4 MPa, elongation at break of 251 % and yield strength of 13.1 M Pa. The self-healing properties of nanocomposites are still retained. The maximum electrical conductivity of the composite coating reaches 56.8 S m−1. The composite coating can recover excellent corrosion resistance in the electrolyte environment after healing, which could ensure its safety and sustainability in the long-term service. We envisage this work offers an idea for the fabrication of environmentally friendly, self-healing, corrosion resistant and electrically conductive coatings with good thermal stability and robust mechanical properties.