Epoxy resin/ethyl cellulose microcapsules prepared by solvent evaporation for repairing microcracks: Particle properties and slow-release performance

Slow-release and self-healing microcapsules were prepared by solvent evaporation with epoxy resin(ER) and ethyl cellulose(EC) as core material and wall material respectively. Particle properties, permeability of core materials and slow-release performance of microcapsules were characterized by environmental scanning electron microscope, laser particle analyzer, high performance liquid chromatography and ultraviolet-visible spectrophotometer. The results showed that ER/EC microcapsules possessed a spherical shape and uniform distribution. The particle size of microcapsules was generally distributed between 75∼175 μm. Compared with ER/EC(N14 and N25) microcapsules, ER/EC(N7) microcapsules had distinguished holes which had a favorable permeability on the surface. ER/EC(N7) microcapsules had a better slow-release performance, with the cumulative release rate of core material reaching 66.1 % for 48 h. In contrast with ER/EC(N7) microcapsules, the encapsulation efficiency and loading content of ER/EC(N25) microcapsules were improved by 5.4 % and 5 %, respectively. The formation of holes on the surface of microcapsules was related to the evaporation of organic solvent (Dichloromethane) passing through the wall material. Therefore, the size of holes on the surface of microcapsules was smaller and the amount of that was larger with the increase of EC viscosity grade. The release behavior of ER/EC microcapsules can be explained by First-order kinetic model, Higuchi model and Korsmeyer-peppas model.