Optimization of Cu doping in BNNF: A new strategy to enhance the flame retardancy, mechanical properties and smoke toxicity suppression of epoxy resin

Boron nitride nanofibres (Cu@BNNF) flame retardants different copper doping was successfully synthesized by calcination. It was then applied to epoxy resin (EP), where uniform dispersion of Cu could be achieved by BN loading, and good flame retardant, mechanical and smoke toxicity inhibition properties were achieved at a low addition amount. Dense residual char was obtained from EP/0.6 Cu–BNNF (4 phr) composites, which could decrease the PHRR and PSPR by 63.45 % and 43.75 %, respectively, indicating that EP/Cu–BNNF composites have excellent fire protection properties. DSC analysis results showed that BNNF and Cu had a synergistic effect on the thermo-mechanical properties of EP composites, and the appropriate amount of Cu played a catalytic role in the cross-linking of EP. Thermogravimetric infrared (TG-FTIR) results showed that by controlling the doping amount of Cu, the generation of gas-phase hazardous products such as CO, aromatic compounds and flammable small molecule alkenes was significantly reduced, and the flame-retardant and smoke-eliminating properties of EP were improved. The analysis of the residual char after combustion shows that the incorporation of Cu–BNNF improves the densification. Based on the analysis of the gaseous and condensed phases to illustrate how BNNF and Cu play a role in burning EP nanocomposites.