Synthesis of isocyanurate‐based imidazole carboxylate as thermal latent curing accelerator for thermosetting epoxy resins

Abstract

A novel thermal latent curing accelerator, 1‐(2‐cyanoethyl)‐2‐methylimidazole/tris (2‐carboxyethyl) isocyanurate adduct (2MICN‐T), was successfully synthesized through an acid–base neutralization of tris(2‐carboxyethyl)isocyanurate (TCEIC) and 1‐(2‐cyanoethyl)‐2‐methylimidazole (2MICN). It was further added into diglycidylether of bisphenol A based epoxy resin/methylhexahydrophthalic anhydride mixture to form one‐component curing systems. With the addition of 2 wt% of 2MICN‐T, the one‐component system could be steadily stored for more than 1 month at room temperature, while the shelf life of 2MICN curing system was only 2 days. Nonisothermal differential scanning calorimeter also demonstrated the excellent thermal latency of 2MICN‐T in low‐temperature region and rapid initiation of the curing reaction when raising temperature. Compared to the cured resins with original 2MICN as accelerator, the resulted thermosets exhibited enhanced glassy storage modulus, glass transition temperature, and thermal stability when 2 wt% of 2MICN‐T was applied. It was attributed to the chemical incorporation of the isocyanurate moieties with multi carboxyl groups and nitrogen‐contained heterocyclic ring, effectively increasing the crosslinking density, chain rigidity, and heat resistance of the cured resin. Thus, it is suggested that 2MICN‐T can play both roles as latent curing accelerator and modifier for one‐component epoxy compounds, and is particularly recommended for application in electronic packaging fields.

Imidazole substituted benzothiadiazole derivatives as latent curing agent for epoxy thermosetting resin

“…This is because the electron‐absorbing group BTD inhibits the activity of imidazole and increases the activation energy of the curing reaction 38 . At the same time, the n value of EP/17.5 wt% BTD‐MZ 2 curing system is more approximately equal to 1, indicating that the curing reaction of the system can be regarded as a first‐order reaction 39,40 . This is because only N atom at position 3 of BTD‐MZ 2 can react with EP, while position 1 and position 3 N atoms of 2E4MMZ can react with epoxy group, which is a relatively complex reaction process 38,41 …”

Thermally Controlled Acceleration of Epoxy Resin Curing through Polymer-Bound Imidazole Derivatives with High Latency

“…Various attempts have been carried out to attain improved storage stability for imidazole derivatives. For example, encapsulation of imidazole derivatives in different polymeric or inorganic materials, as well as incorporation into inorganic networks, was described. − Also, imidazole complexes exhibiting controlled initial nucleophilicity have been reported. , Furthermore, imidazole-releasing compounds like carbonyldiimidazole or thermally sensitive Michael adducts of imidazole have been investigated. , Unfortunately, most of the accelerators known from the literature either do not show sufficient storage stability or their reactivity is highly compromised.…”

“…9−13 Also, imidazole complexes exhibiting controlled initial nucleophilicity have been reported. 14,15 Furthermore, imidazole-releasing compounds like carbonyldiimidazole 16 or thermally sensitive Michael adducts of imidazole have been investigated. 17,18 Unfortunately, most of the accelerators known from the literature either do not show sufficient storage stability or their reactivity is highly compromised.…”

A Study on Temperature Distribution within HVDC Bushing Influenced by Accelerator Content during the Curing Process

“…During the curing process of the bushing capacitor core, the accelerator is an economical and easy means for speeding up the reaction process, which plays a vital role in the curing conditions and the performance of the cured products. So far, for accelerators, scholars have focused more on the gel time and the rheological properties of the reaction system [13][14][15], as well as the glass transition temperature, tensile modulus, elongation at break, elastic modulus, dielectric loss, and other properties of the cured products [16][17][18][19][20]. However, less research has been carried out to analyze the effect of the accelerator contents on the internal temperature distribution of large-size bushing with different length-to-diameter ratios during the curing process, which is important for the regulation of the curing conditions and the performance of the bushings.…”