Encapsulation of maleimide-based healing agent and reversible diels-alder chemistry for selfhealing and corrosion prevention

Protective epoxy coatings for metal substrates are used for wear resistance and physical protection against environmental conditions that may result in physical or chemical changes, such as corrosion. Previous work done by Pratama et al. [1] investigated the use of encapsulated solutions containing maleimide-based healing agents for self-healing of furan functionalized epoxy networks through reversible Diels-Alder chemistry. Results from these studies show that the use of phenyl acetate (PA) as a solvent, and the concentration and structure of maleimide healing agent affects the degree of physical and chemical bonding across the crack surface. In those studies a urea-formaldehyde (UF) encapsulation technique was used to create capsules with a diameter of ≤ 300 μm. Such capsules are too large for incorporation into protective coatings that generally have thickness of 30-40 μm. Thus capsules with an approximate diameter of ≤ 20 μm are desired. This was achieved by increasing shear rate and by incorporating ultrasonication processing to the UF encapsulation procedure. The purpose of this work is to study the effect of capsule size on the protective electrochemical properties in thin films representative of coatings.