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Microencapsulation of imidazole curing agents by spray-drying method



An epoxy resin–imidazole system was used to form the adhesives for the anisotropic conducting film (ACF), and a latent curing system was necessary for the ACF. In this study, imidazoles were microencapsulated for the latent curing system. Polycaprolactone (PCL) was used as the wall material, and the spray-drying method was used to form the microcapsule. The imidazoles used in this study were imidazole, 2-methylimidazole, and 2-phenylimidazole. The effect of the ratio of PCL to imidazoles, and the effect of PCL molecular weight were investigated during the microcapsule formation. The amount of imidazoles in the microcapsule was measured using thermogravimetric analyzer and elemental analysis. The permeability of the microcapsules was measured in ethanol, and the shelf life of the microcapsules was studied for the epoxy resin. The curing behavior of these microcapsules to epoxy resin was examined using differential scanning calorimeter. In the curing reaction, the microcapsule of imidazoles exhibited delayed kinetic behaviors compared to pure imidazoles. And the curing times were estimated at 150 and 180°C using an indentation method. These microcapsules of imidazoles exhibited a long shelf life, and the curing did not occur in some of the microcapsule–epoxy resin systems at 20°C for 15 days. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011