A versatile ionic liquid enables epoxy resin with excellent fire safety and mechanical properties but ultra-low loading

The emergence of ionic liquids provides an effective way to construct new advanced multifunctional epoxy resin (EP) composites with excellent fire retardancy and mechanical properties. In this study, 1-butyl-3-methylimidazolium dibutyl phosphate (BDBP) was synthesized via a facile strategy and then incorporated into the EP matrix. The results showed that ultra-low loading of BDBP (1 wt%) enabled EP composite to achieve a V-0 rating (3.2 mm) in the UL-94 test. When increasing the loading to 4 wt%, the limiting oxygen index (LOI) of EP/BDBP4 composites was improved to 31.9 %. Meanwhile, the peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) significantly decreased by 48.1 %, 21.9 %, and 13.5 %, respectively, compared to neat EP. Moreover, the presence of BDBP increased the tensile strength of EP/BDBP2 by more than 7 %, while all EP/BDBP composites maintained high transparency. In summary, this work provides a feasible and low-cost idea for constructing multifunctional EP composites, paving the way for their applications in aerospace, wind turbines, and electronic and electrical fields.