Synthesis of a novel dicyclic silicon-/phosphorus hybrid and its performance on flame retardancy of epoxy resin

A novel silicon-/phosphorus hybrid (SDPS) was synthesized by a condensation polymerization of diphenylhydroxysilane and spirocyclic pentaerythritol di(phosphate monochloride). The use of SDPS and the cooperative use of SDPS with P–N hybrid in flame retardant epoxy resin (EP) were investigated. Limiting oxygen index and cone calorimeter tests showed that the loading of SDPS and the cooperative use of SDPS and P–N hybrid in EP provided enhanced fire resistance. TGA, TG-FTIR and SEM measurements revealed that the enhancement in fire resistance was arising from the formation of a compact honeycomb carbonaceous structure hybridized by silica, the good char forming ability and the inhibition of flammable gas release. Further analysis from Raman spectra revealed that the compact carbonaceous layer may be originated from an increase in ordering of amorphous carbonaceous layer.