Preparation and characterization of a novel microcapsule-type latent curing agent for epoxy resin

Abstract A novel spherical latent curing agent microcapsule with the diameter ranging from 6 to 30 μm has been prepared by encapsulating butyl glycidyl ether modified 2-ethyl-4-methyl imidazole (BGE-M-2E4MZ) with polyetherimide (PEI) as the shell material through emulsion/solvent evaporation method. The microcapsule-type latent curing agent was characterized by a Fourier transformation infrared spectrometer, an optical microscope, and an environmental scanning electron microscope. The optimal parameters were obtained through experiments, and the influences of different process parameters on the formation of microcapsules were studied. When the prepared microcapsule-type latent curing agent was mixed with epoxy resin, there were few curing reactions occurred after storage for 100 days at 25 °C, however this latent curing agent could be released and curing reaction of the epoxy resin could be finished within 3 h at 100 °C. In the process of curing, this agent could not be released uniformly in the resin due to the restriction of microcapsule shell, so the resin could not be cured 100%, causing a sharp decrease of mechanical properties of E-51/Mic-2E4MZ casting.