Effect of urethane functionality and number of epoxide groups on cure and mechanical behaviors of epoxy resins

We report the synthesis of the novel bi- and tetrafunctional epoxy resins, 2-ECI and 4-ECI, containing urethane functionality. Their chemical structures were characterized by Fourier transform infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. The effects of urethane functionality and the number of epoxide groups on the curing behavior and physical and mechanical properties of the epoxy resins were investigated. Compared to 4-ECI, 2-ECI was more reactive with the curing agent methyl hexahydrophthalic anhydride. However, the shear strength and critical stress intensity factor values of the cured 4-ECI resin were significantly higher than those of the cured bisphenol-A diglycidylether and 2-ECI resin, which was attributed to the synergistic effects of urethane functionality and high cross-linking density in the cured 4-ECI resin.

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