Synthesis of aluminum phosphate–coated silica: effect on mechanical properties and flame retardancy of epoxy resin

The designability of the morphology and composition of inorganic particles plays a vital role in controlling the flame retardancy of polymers, an arena in which inorganic fillers have become a hot spot in the research field of halogen-free flame retardants. Here, aluminum phosphate (AlPO 4 )-coated silica (SiO 2 ) (SiO 2 @AlPO 4 ) particles were prepared via a facile one-pot heterogeneous precipitation strategy. The effect of the AlPO 4 content on the morphology of SiO 2 @AlPO 4 was systematically studied to regulate the dispersion of AlPO 4 nanoparticles. Moreover, the effect of SiO 2 @AlPO 4 on the flame retardancy of epoxy (EP) resin was further investigated. Results show that SiO 2 @AlPO 4 simultaneously strengthens the mechanical properties and improves the flame retardancy of EP and that this phenomenon may be attributed to the synergistic effect of the AlPO 4 nanoparticles and SiO 2 microparticles. This work details a facile yet effective strategy to engineer the morphology and composition of inorganic particles to control the properties of polymers.