A synergistic strategy with phosphorus-based compound and ionic liquid VIPA for simultaneously enhanced flame retardancy, mechanical properties, and chemical resistance of epoxy resin

Epoxy resins (EP) are widely used in construction and electronic packaging， however, their flammability and the substantial smoke generation during combustion remain critical issues that need to be addressed. In this study, a novel ionic liquid, VIPA, was synthesized via a one-step method and co-introduced into the EP system along with DOPO. When 3 wt% DOPO and 1 wt% VIPA were added, the composite achieved a V-0 rating in the UL-94 test, with the LOI increasing to 32.3 %. The fire hazard of the EP-3DOPO/1VIPA composite significantly decreased, with a 36.3 % reduction in pHRR, while maintaining excellent mechanical properties: the tensile strength increased by 44.2 %, and the impact strength improved by 65.9 %. The synergistic effect of DOPO and VIPA also endowed the material with high transparency, UV resistance, acid and alkali stability, and significant fluorescence properties. The multifunctional enhancement mechanisms under the synergistic action of multiple components were revealed, providing experimental evidence for the development of multi-component thermosetting composites with both high safety and multifunctionality.