Phosphor nitrile functionalized UiO-66-NH2/graphene hybrid flame retardants for fire safety of epoxy

Abstract

Phosphor nitrile functionalized UiO-66-NH2/graphene (G-U-H) was prepared combined a green mechanochemical method and microwave-assisted rapid method to improve the fire safety of epoxy resin (EP). The scanning electronic microscopy, transmission electron microscope and X-ray diffraction results indicated that the G-U-H exhibited sandwich-like hybrid structure. And the -OH from graphene nanoplatelets and -NH2 from UiO-66-NH2 were grafted with hexachlorocyclotriphosphazene to form covalent bonds. The obtained flame retardant was added to the EP at a different content. The flame retardancy index and cure index of EP composites were calculated, and those of EP-3 were both good. The cone calorimetry test showed that the flame retardancy of EP was improved and the flame retardant mechanism is the combination of condensed phase and gas phase with the synergistic of P, N and other elements. The physical barrier of graphene nanoplatelets and the generated more stable and denser residual char in condensed phase can effectively cut off the heat and mass transmission. In gas phase, the non-flammable gases were generated to help reduce the heat released.