Dual microcapsules based epoxy/polyethyleneimine autonomous self‐healing system for photo‐curable coating

Self‐healing coatings were fabricated by adding two different epoxy and polyethyleneimine microcapsules to epoxy‐polyester acrylate resin. The first capsule contained polyethyleneimine and the second capsule contained a commercial epoxy resin. Polyethyleneimine (PEI) microcapsules were prepared by filling PEI into hollow poly(melamine‐urea‐formaldehyde) (PMUF)‐shelled polymeric microcapsules. Epoxy microcapsules were prepared by coating with a poly(urea‐formaldehyde) (PUF)‐shelled material using in‐situ polymerization. Using thermogravimetric analysis (TGA), the healing agent contents of the microcapsules for epoxy and PEI were determined to be 55% and 49%, respectively. Moreover, using a zeta‐sizer, the mean sizes of the microcapsules for epoxy/PUF and PEI/PMUF were determined to be 185 nm and 377 nm, respectively. Both capsule types were added to the epoxy‐polyester acrylate‐based photo‐curable coating formulation in the amount of 2% by weight. The coating formulation was applied to plexiglass surface, then cured with UV light and artificial scratches were made on the coating surface. At the end of day two, the SEM images revealed that coating successfully self‐healed the scratch.