Functionalized graphene with DOPO based organic/inorganic flame retardants: Preparation and its reinforcements on the flame retardancy of polyurea composites

Graphene (rGO) is a promising nano‐filler for reinforcing the properties of polymer nanocomposites, but the aggregation in polymer nanocomposites limits its application. To solve this problems, rGO was functionalized with silicon‐based organic/inorganic flame retardants through sol–gel process with controllable thicknesses (1.9 nm thick and 4.9 nm thick). The functionalized graphenes, noted as FGO‐1 (1.9 nm thick) and FGO‐2 (4.9 nm thick), are then incorporated into polyurea (PUA) at the loadings of 1 wt% and the property reinforcement are compared and investigated. After surface modification, covalent attachment of organic/inorganic flame retardants to the surface of rGO can prevent the agglomeration effectively and greatly improve the dispersion of rGO in the PUA matrix. Since those silicon‐based flame retardants can act as a good compatibilizer during in situ polymerization process, and all the PUA/FGO composites have good dispersion at the loading of 1 wt%, as evinced by transmission electron microscopy result. When 1 wt% of FGO‐2 is incorporated into PUA matrix, thermal and flame retardant properties of the composites are enhanced significantly compared with those of PUA/FGO‐1 composites in air atmosphere. Moreover, the introduction of FGO‐1 results in a 17.7% increase in tensile strength, while the PUA/FGO‐2 results in 31.4% increase. The good dispersion and organic/inorganic flame retardants on the surface of rGO are believed to be key factors for the improvement of mechanical properties of PUA/FGO‐2 composites. POLYM. COMPOS., 39:4637–4645, 2018. © 2017 Society of Plastics Engineers