Effect of Carbon Nanotubes Combined with Hexaphenoxycyclotriphosphazene on the Flame Retardancy of Epoxy Resin

Epoxy resin composites were prepared via in situ polymerization of diglycidyl ether of bisphenol a epoxy monomer and 4,4'-diaminodiphenyl methane, using multiwalled carbon nanotubes and hexaphenoxycyclotriphosphazene as additives. The morphologies of the specimens were investigated using scanning electron microscopy; thermogravimetric analysis was used to study thermal properties. The results showed that carbon nanotubes improved thermal stability of epoxy resin, but hexaphenoxycyclotriphosphazene decreased thermal stability of epoxy resin. Limit oxygen index, UL-94 vertical burning test and cone calorimeter measurements were used to study the flame retardancy of epoxy resin composites. The results indicated that epoxy resin composites containing hexaphenoxycyclotriphosphazene reached UL-94 V-0 rating, and combustion parameters obtained from cone calorimetry were improved.