Low-Temperature Curing of Cyanate Ester with High Thermal Stability via a Dual-Primary-Amine Catalyst

Reducing the curing temperature of cyanate ester (CE) is essential for its industrial adoption, yet conventional catalysts typically compromise the material’s high-temperature stability. Herein, 3,4-diaminobenzonitrile (DABN) is employed as a catalyst to lower the cure temperature of CE without compromising the thermal stability. Mechanistic investigation indicates that DABN functions via nucleophilic catalysis, markedly accelerating the cyclotrimerization of cyanate groups. Kinetic analysis demonstrates that DABN loadings of ≥2.5 wt % lower the apparent activation energy by >22.0% and promote ambient-temperature gelation. Crucially, the nitrile group of DABN reacts with CE, covalently incorporating it into the network and eliminating free catalyst residues. This integration suppresses high-temperature weight loss, lowering the mass loss at 300 °C from 11.7 to <1.5%. Cured networks with ≤7.5 wt % DABN retain mechanical and dielectric properties comparable to pristine BECE. The results position DABN as an efficient, integrated catalyst, offering a solvent-free, low-temperature route to curing CE.