P/N-containing SiO2 flame retardant particles formed by in-situ hydrolysis for significantly improve the flame retardancy and toughness of epoxy resins

To obtain flame retardants with more efficient and multidimensional flame retardant modes, this work formed P/N-containing silica flame retardants (PBPSi) by hydrolysis and used them in epoxy resins (EP) to give them good flame retardant properties. The hydrolyzed SiO 2 flame retardant builds an integrated flame-retardant structure and a concentrated stress-bearing point, the EP has good fire resistant properties and toughness. Allowing the addition of 7-PBPSi/EPPBPSi to enable EP to achieve a UL-94 rating of V-0, and the impact strength of 5-PBPSi/EP reached 52.9 kJ/m 2 . In addition, PBPSi has good performance in inhibiting heat release and toxic gas release, and the PHRR and THR of 7-PBPSi/EP were reduced by 54.6 % and 24.6 %, respectively, compared with pure EP, the content of CO and CO 2 also decreased. The analysis of the flame retardant mechanism indicated that PBPSi played a flame retardant role in the biphasic phase through the catalytic carbon formation in the condensed phase and the synergistic dilution of flammable gases and trapping of free radicals by P/N synergistic. • Silica flame retardants with P/N synergistic flame retardant system were formed by in situ hydrolysis process. • The polymerized silica structure can synergise with the organobenzene ring to create a better carbon layer. • The silica particles can increase toughness by extending the force to all points and dispersing the stress.