Effect of mechanical properties on the self‐healing behavior of waterborne polyurethane coatings

Abstract The effect of structural parameters such as hard segment content and cross‐linking degree on the mechanical properties of waterborne self‐healing polyurethane and the effect of tensile strength, self‐healing conditions (temperature, time) on the self‐healing properties were investigated. These results demonstrated that as the increasing of the content of hard segments/the cross‐linking agent, the tensile strength of the sample increased and the self‐healing performance exhibited a downward trend. When the tensile strength reached 40 MPa, it could hardly healed, even if prolonging the self‐healing time or increasing the self‐healing temperature. Mechanism study demonstrated that the self‐healing ability was attributed to the dynamic exchange of disulfide bonds and the thermal reversibility of hydrogen bonds in the system. Hydrogen bonding could provide the initial self‐healing force and promote the dynamic exchange reaction of disulfide bonds, while high hydrogen bonding is not conducive to the movement of macromolecular segments, causing a decrease in the self‐healing efficiency.