Diffusion and Reaction Phenomena in Solution-Based Healing of Polymer Coatings Using the Diels-Alder Reaction

The healing of a furan-functional epoxy coating using bismaleimide (BMI) solutions is demonstrated. Corrosion studies of scratched coated carbon steel show that solution healing of damaged coatings inhibits corrosion. The healing relies on (i) the diffusion of solution components into the polymer, causing the system to swell, thus bringing crack surfaces into contact, and (ii) DielsAlder adduct formation between furan moieties of the polymer network and the maleimide, resulting in covalent bonding across the crack interface. For the system investigated, crack healing is reaction-limited for small crack widths. The results provide a guideline for the design and implementation of self-healing systems based on BMI solution encapsulation.