Self-standing cuprous oxide nanoparticles on silica@ polyphosphazene nanospheres: 3D nanostructure for enhancing the flame retardancy and toxic effluents elimination of epoxy resins via synergistic catalytic effect

A novel strategy was developed for the preparation of 3D nanostructure to improve the flame retardancy and toxic effluents elimination of epoxy resins (EP) via synergistic catalytic effect. Herein, the synthesis of cross-linked organic-inorganic polyphosphazene nanoshells (PZM) with amino-rich groups was reported via a facile condensation polymerization of hexachlorocyclotriphosphazene (HCCP) and 4,4′-diaminodiphenyl ether (ODA) on silica (SiO2) nanospheres as templates. Then cuprous oxide nanoparticles (Cu2O NPs) were synthesized by simultaneous chemical reduction method on the surface of polyphosphazene nanoshells. Subsequently, the obtained SiO2@PZM@Cu spheres were incorporated into the EP to prepare samples for investigation of their flame-retardant and toxicity suppression performance. Herein, cone results indicated that the incorporation of 2 wt% SiO2@PZM@Cu obviously improved the flame-retardant performance of EP, such as 37.9% reduction in peak heat release rate and 31.3% decrease in total heat release. On the other hand, the amount of toxic CO and other volatile gas products from the EP decomposition significantly suppressed after incorporating the SiO2@PZM@Cu, implying a reduced toxicity. In addition, a mechanism for the flame retardancy and toxicity elimination was proposed. It is reasonable to believe that the enhanced flame retardancy and toxic effluents elimination for nanocomposites are attributed to synergistic effect from respective components (Cu2O NPs and PZM) plus the SiO2 spheres.