Novel organic–inorganic flame retardants containing exfoliated graphene: preparation and their performance on the flame retardancy of epoxy resins

Abstract

In this work, a simple and efficient approach for the preparation of organic–inorganic hybrids flame retardants (FRs-rGO), aiming at improving the flame retardant efficiency was presented. The reduced graphite oxide (rGO) was incorporated into the flame retardants matrix by in situ sol–gel process, resulting in the formation of organic–inorganic hybrids flame retardants containing exfoliated rGO. The TEM results of FRs-rGO hybrids revealed that the rGO was previously exfoliated in the phosphorus and silicon containing FRs. Subsequently, the flame retardant (FRs-rGO) was incorporated into epoxy resins (EP). The previous exfoliation of rGO in the FRs allows rGO to be intimately mixed with epoxy resins, which can be confirmed by the TEM results of FRs-rGO/EP nanocomposites. With the incorporation of 5 wt% of FRs-rGO into EP, satisfied flame retardant grade (V0) and the LOI as high as 29.5 were obtained. The char residues of the FRs-rGO/EP nanocomposites were significantly increased in air as well as nitrogen atmosphere. Moreover, the peak heat release rate (pHRR) value of FRs-rGO/EP was significantly reduced by 35%, and the glass transition temperature (T_g) of FRs-rGO/EP nanocomposites shifted to higher temperature, compared to those of neat EP. The flame retardancy strategy of FRs-rGO combines condensed phase and gas phase flame retardant strategies such as the nanocomposites technique, phosphorus–silicon synergism systems in the condensed phase and DOPO flame retardant systems in the gas phase. Moreover, the flame retardants containing exfoliated graphene (FRs-rGO) provided a novel method to prepare organic–inorganic hybrids flame retardants and the as-prepared flame retardants exhibited high flame retardant efficiency.