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Abstract
T-peel strength of joints made with moisture-curable epoxy resin was determined using ketone based imines (ketimines) of different sizes as latent hardeners, and was compared to the amine (1,3-BAC) curing system. The strength was higher for the bulky ketimines (BAC-MIPK, BAC-MIBK) curing systems than the other systems. Both the chemical conversion of the epoxide and the gelfraction in case of the bulky ketimine curing systems showed higher values in the final stage, while the initial curing reaction proceeded faster for the amine and the small ketimine curing systems. The differences observed between the curing systems can be explained in terms of the hydrolysis rate of the ketimines and the diffusion rates of the epoxy resin and the ketimines. The initial curing reactions proceeded faster for the amine and small ketimine curing systems because hydrolysis of the ketimines occurs easily. However, the diffusion of them for the bulky ketimine curing systems would be easier in the final stage of curing because of the larger plasticizing effect with the bulky (large volume) ketones formed by hydrolysis of the ketimines in the systems. This indicates that the ketones formed by hydrolysis of the ketimines are very useful for increasing the crosslink network density of the cured resins, which would result in superior adhesion.