Complexes of imidazole with poly(ethylene glycol)s as the thermal latency catalysts for epoxy–phenolic resins

Analysis of the reaction mechanism of the thiol–epoxy addition initiated by nucleophilic tertiary amines

“…40 A similar consequence could be expected for the initiation step between the imidazole and the epoxy ring. The initiation step in epoxy-imidazole systems is highly sensitive to the chemical environment, not only due to the presence of catalytic species 17,21 but also to the formation of unreactive complexes in the presence of polyethers, 45 like in epoxy-amine systems. 40 Nevertheless, in the absence of more detailed experimental information (i.e.…”

Green and Facile Synthesis of Bio-Based, Flame-Retardant, Latent Imidazole Curing Agent for Single-Component Epoxy Resin

“…Nevertheless, the unmodified imidazoles display poor thermal latency due to their extremely high reactivity. Many works have confirmed that introducing functional groups to the 1-position or 3-position nitrogen atom of imidazole ring can passivate its reactivity. − These functional groups, such as epoxy groups, acyl chlorides, and olefins, possess an electron-withdrawing or steric-hindrance effect, thus enhancing the thermal latency of imidazole curing agents. − Recently, to achieve the latency and flame retardancy, a series of phosphorus-containing imidazole curing agents have been synthesized for EPs. For instance, Xu et al prepared two kinds of phosphorus-containing imidazoles (DPPIO and DPIPP) for EP.…”

“…Our groups also reported some flame-retardant single-component epoxy resins based on P-containing imidazoles. However, these EPs suffer from a high curing temperature, and some of them require postcuring at above 200 °C, leading to high energy consumption. − As a Lewis base, the 3-position nitrogen atom of imidazole can be neutralized by different Lewis acids, and the formed ionic bond can be easily broken under heating. ,, Meanwhile, the neutralization reaction is convenient and fast. Obviously, the phytic acid can be used to neutralize the imidazole.…”

A Modified Imidazole as a Novel Latent Curing Agent with Toughening Effect for Epoxy

“…Based on this principle, many kinds of latent curing agents have been developed, such as imidazole derivatives, dicyandiamide, boron-amine complexes and others. [7][8][9] 10,11 12,13 [14][15][16] Imidazole derivatives account for most of latent curing agents, because they can provide polymers with better heat resistance, lower tensile elongation, higher modulus and wider range of cure temperature than amine-cured system. They play an important role in electronic integrated circuit encapsulation industry.…”