A curing agent for epoxy resin based on microencapsulation of 1-butylimidazole

An efficient and economical strategy for rapid microencapsulation of 1-butylimidazole (1-BMI) was developed. The strategy is based on the thiol-yne click reaction of trimethylolpropane tris(3-mercaptopropionate) and 1,7-octadiyne in oil-in-water emulsion. The thiol-yne click reaction is not only green and efficient, but also improves the cross-linking density of shell. Thus, the obtained shell prevents the leakage of curing agent and prolongs the storage period of EP/MCs system. The whole process of preparing 1BMI-MCs only took 40 min. Moreover, the effects of stirring speed and the ratio of 1BMI on the size and core content of microcapsules (MCs) were investigated. Results demonstrated that the optimal particle size was about 10.8 μm, and the maximum content of 1BMI in MCs was 33% corresponding to 60% 1BMI in oil phase. Afterward, the 1BMI MCs were used as latent curing agent (LCA) for epoxy resin (EP). In the curing reaction of the epoxy resin, the 1BMI-MCs exhibited a delayed kinetic behavior compared to pure 1BMI. Furthermore, the E-51/MCs system had a storage term of 16 weeks. The shell material not only had no effect on curing effect of E-51, but also toughen the cured EP systems. This paper provided a promising method for long-term storage of LCA.