Thermally Curable One-Component Epoxy Based on Tetraethylenepentamine Microcapsules

One-component epoxies are highly attractive for industrial applications due to their simplicity and stable performance, but their development is constrained by the trade-off between storage stability and curing activity. Herein, using TEPA microcapsules (TEPA-MCs) consisting of a dense polyurea shell and a highly reactive TEPA core, thermally curable one-component epoxies were successfully developed. The storage stability at room temperature (25 °C), thermal-responsive curing behavior, and the bulk tensile properties of cured products were systematically evaluated for the formulated one-component epoxies. It shows good storage stability at room temperature. After 30-day storage, it maintains uniformity and TEPA-MCs in it keep their initial morphology. Its rheological stability decreases with the increased TEPA-MCs content. However, even the E51(6%)/MCs-2:1 epoxy with the lowest stability exhibits a markedly extended rheological stability over 20 days. The thermal-response mechanisms of TEPA release for TEPA-MCs upon heating were revealed. Attributed to both the overall uniform diffusion and the localized rupture of microcapsules, TEPA can be rapidly released to cure the epoxy mixture. Due to the high intrinsic reactivity of TEPA, the majority of curing occurred within 5–25 min at 100–120 °C. For the bulk tensile properties, although the one-component epoxy based on TEPA-MCs has a reduced tensile strength, the E51(6%)/MCs-2:1 epoxy still retains a relatively high strength of 32 ± 1.4 MPa, only an 11.6% strength reduction compared to that cured by pure TEPA. These findings provide a feasible strategy for the development of one-component epoxies with both good storage stability and efficient curing under moderate thermal conditions.