Influence of Cuprous Oxide on Enhancing the Flame Retardancy and Smoke Suppression of Epoxy Resins Containing Microencapsulated Ammonium Polyphosphate

In this work, Cu 2 O exhibited better synergistic effect with microencapsulated ammonium polyphosphate (MAPP) than other metal oxides, such as CuO, ZnO, SnO, Fe 2 O 3, Ni 2 O 3, and Co 2 O 3, on improving the flame retardancy of epoxy resins (EP). Moreover, the addition of cuprous oxide (Cu 2 O) could further decrease the total smoke production and carbon monoxide production. The analysis of char residues and evolved gases indicated that Cu 2 O was beneficial to enhance the formation amount, intumescent degree, and compactness of char. The protective layer of intumescent char residue could hinder the decomposition of EP and diffusion of gaseous products, such as hydrocarbons, aromatic compounds and carbon monoxide (CO). In addition, Cu 2 O also played a role in conversion of CO to CO 2 through a redox cycle, involving the reduction of Cu 2+ —Cu + —Cu 0 by CO and the oxidation of Cu 0 —Cu + —Cu 2+ by O 2 . The possible flame retardant, smoke suppression, and CO oxidation mechanisms were proposed.