The flame retardancy of blob-like multi-walled carbon nanotubes/silica nanospheres hybrids in poly (methyl methacrylate)

Multi-walled carbon nanotubes (MWNTs) were grafted with poly (acrylic acid), and subsequently coated with a close-packed layer of silica nanospheres, namely SiO2-g-MWNTs. Such blob-like MWNTs/silica nanospheres hybrids were introduced into poly (methyl methacrylate) (PMMA) as a kind of flame retardant. From determinations of thermogravimetric analysis and cone calorimeter tests, it was indicated that the SiO2-g-MWNTs not only increased the initial degradation temperature and the maximum weight loss rate temperature of PMMA, but also decreased the peak of heat release rate. Observation using scanning electron microscopy revealed that the silica nanospheres on the surface of MWNTs strengthened the protective network layer during combustion.