High-performance, intrinsically fire-safe, single-component epoxy resins and carbon fiber reinforced epoxy composites based on two phosphorus-derived imidazoliums

Carbon fiber reinforced polymer (CFRP) composite is a kind of lightweight material with excellent comprehensive properties, but low production efficiency and inherent flammability have become two crucial limitations for its further application. Herein, two phosphorus-derived imidazoliums (CEPM-1 and CEPM-2) were synthesized by aqueous self-assembly, and applied to flame-retardant, one-component epoxy resins (EPs). Moreover, the well-designed EPs (EP/CEPM-1–25 and EP/CEPM-2–20) were used as resin matrixes for CFRP. Both EPs featured superior latency and modest-temperature fast curing, especially EP/CEPM-1-25, which had a long shelf life of 30 days and can gel within 20 min at 150 °C. The limiting oxygen index (LOI) and UL-94 classification of EP/CEPM-1-25 were 33.0% and V-0, indicative of superior flame retardancy. The total smoke production and maximum smoke density of EP/CEPM-1-25 displayed 37.7 and 72.1% reductions relative to those of the control EP sample cured by imidazole, demonstrating improved smoke suppression. EP/CEPM-2-20 also displayed satisfactory fire safety, but slightly inferior to EP/CEPM-1-25. As expected, the CFRP composites based on EP/CEPM-1-25 and EP/CEPM-2-20 showed high LOIs (42.5 and 39.0%) and UL-94 V-0 classification due to the inhibition of P-containing groups in CEPM-1 and CEPM-2 on the wick effect. Therefore, this work proposes a facile and ‘green’ methodology to create high-performance, intrinsically fire-safe single-component EPs and CFRP composites.