Self-healable and stretchable polyurethane film
A simple strategy is reported for preparing self-healable cationic waterborne polyurethane (WPU/TAx), in which cross-links are formed via hydrogen bonds between tannic acid (TA) and the rigid domains of linear WPU.
The cut could be able to completely heal in air condition at room temperature in one week without any external stimulation. The healing time can be largely reduced to 3 h when the cut sample are treated at 50 °C.
The rigid domain’s containing multiple types of H-bonds classified as ordered H-bonds and disordered bonds is the main reason for the self-healing property, which is supported by Infrared spectrum.
Improved mechanical properties
These H-bonds are also responsible for greatly improved mechanical properties of WPU. The maximum tensile strength and elastic modulus of WPU/TA5.1 are twice and 2.5 times that of pure WPU respectively, up to 32 MPa and 2.44 MPa. The combination of enhanced mechanical properties and self-healing in moderate conditions is achieved by just simply mixing WPU dispersion and tannic acid aqueous solution.
The study has been published in Progress in Organic Coatings, Volume 151, February 2021.