One-step in situ synthesis of a novel α-zirconium phosphate/graphene oxide hybrid and its application in phenolic foam with enhanced mechanical strength, flame retardancy and thermal stability

A novel α-zirconium phosphate/graphene oxide hybrid (ZGO) with α-zirconium phosphate (α-ZrP) nanoparticles immobilized on the surface of graphene oxide (GO) sheets was successfully synthesized by a one-step in situ method, and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), FTIR spectroscopy and transmission electronic microscopy (TEM). TGA results showed that the modification of α-ZrP nanoparticles on the GO surface significantly improved the thermal stability of the GO. Subsequently, the ZGO was incorporated into phenolic (PF) foams for reducing their high brittleness and friability. At a ZGO dosage of 4 phr (parts per hundreds of resin), the flexural and compressive strengths of the ZGO-toughened PF foams increased by 33.8% and by 39.6%, respectively, and the pulverization ratio decreased by 57.5%, compared with the pure PF foam. Besides, the results of the TGA test, limiting oxygen index (LOI) and cone calorimetric test demonstrated that the addition of ZGO imparted excellent thermal stability and flame retardancy to the PF foam, which was mainly attributed to the synergistic effects between α-ZrP nanoparticles and GO.