An epoxy latent curing agent with outstanding storage stability and processing convenience

Abstract

The latent curing of epoxy resins has long been constrained by the inherent dilemma between easy deactivation at room temperature and the demand for rapid curing at elevated temperatures, severely limiting their large-scale applications. Herein, we innovatively constructed a Mn 2+ -based metal–organic framework (Mn-NPA) using sodium nitroterephthalate as the organic ligand, and utilized it as a host matrix to encapsulate 2-methylimidazole (2MI) with a loading ratio of 35 wt%, yielding a latent curing agent denoted as 2MI@Mn-NPA. This material demonstrated excellent thermal stability, releasing the curing agent at 170°C. Remarkably, the epoxy system exhibited a shelf life of 78 days at ambient temperature, compared to only 3.33 h for the pristine E-51 resin. The exceptional storage stability stems from the spatial confinement effect of the Mn-NPA framework, which suppresses the room-temperature activity of 2 MI; upon heating, the active species are liberated, thereby realizing an “ambient-inert, thermally activated” characteristic. Combining excellent storage stability with superior processing convenience.