Excellent role of Cu2O on fire safety of epoxy resin with ammonium polyphosphate based on the construction of self‐intumescent flame retardant system

Abstract This work reports an effective self‐intumescent flame retardant system for epoxy resin (EP) based on the remarkable synergistic effect between Cu2O and ammonium polyphosphate (APP). The effect of Cu2O/APP on improving EP's fire performance was evaluated by limited oxygen index (LOI), UL‐94, and cone calorimeter test. The optimal mass ratio of Cu2O: APP was shown to be 2:8. With 15 wt% total flame retardant loading, the EP with optimum Cu2O/APP formulation reached V‐0 classification and high LOI (33.5%), while the EP with APP only got NR and low LOI (26.5%). Additionally, the pHRR, total heat release, total smoke production, CO production of the EP with optimum Cu2O/APP formulation were primarily decreased. All the improvements were ascribed to the formation of the self‐intumescent char layer of EP resulted from the catalyzing effect of Cu2O for char formation and CO to CO2 conversion. These findings will consolidate approaches for conferring flame retardancy to flammable polymers or their blends.