Microencapsulation of self-healing agents containing a fluorescent dye

Two different self-healing agent candidates, endo-dicyclopentadiene (endo-DCPD) and 5-ethylidene-2-norbornene (ENB), containing a fluorescent dye surrounded by a melamine-urea-formaldehyde (MUF) shell were microencapsulated by in-situ polymerization and the resulting microcapsules were characterized in this work.The microcapsules showed a narrow size distribution with a spherical shape and rough outer and smooth inner surfaces for both healing agent systems.Shell thicknesses of the microcapsules were ~880±80 nm for endo-DCPD and ~620±60 nm for ENB.The incorporation of a fluorescent dye as tracer into self-healing agents did not disturb the formation of microcapsules.The release of self-healing liquid into the induced crack from ruptured microcapsules in an epoxy coating layer was observed using a fluorescence microscopy.The use of a fluorescent dye is very effective in the observation of a damage site.