Abstract: Ammonium polyphosphate (APP) was treated with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTOS) by a sol-gel method leading to vinyl modified APP (VMAPP), which was introduced into an epoxy resin (EP). The surface vinyl groups could be used as reaction sites for further modification. Fourier transform infrared spectrum (FTIR) analysis confirmed the presence of the vinyl in the epoxy coating film. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) analysis indicated that a dense protective film was present on the surface of APP. On the film, the content of P, N elements was significantly decreased, and the content of C element increased significantly. The water resistance of VMAPP was better than unmodified APP. The Si element present on the surface of APP synergized with APP to generate more compact and stable char layer and thus promoted the flame retardant performance of EP.

Key words: epoxy resin, polysiloxane, ammonium polyphosphate, surface-modification, flame retardancy