Preparation of a silica nanospheres/graphene oxide hybrid and its application in phenolic foams with improved mechanical strengths, friability and flame retardancy

A silica nanospheres/graphene oxide (SGO) hybrid was successfully synthesized through immobilization of silica (SiO2) nanospheres on the surface of graphene oxide (GO) sheets, and characterized by X-ray diffraction (XRD), field emission scan electronic microscopy (FESEM) and transmission electronic microscopy (TEM). It has been found that the incorporation of the SGO into the phenolic (PF) foams not only obviously increases the mechanical strengths and flame retardancy, but also reduces the pulverization ratio. Specifically, the flexural and compressive strengths of the PF foam modified by 1.5 phr SGO increases by 31.6% and by 36.2%, respectively, compared with pure PF foam. The Cone calorimetric results indicate that the addition of SGO into PF foam leads to a reduction in peak heat release rate and total heat release. Moreover, the thermal stability of the PF foams containing SGO is enhanced compared with the pure PF foam.