Thermal Stability and Flame Retardancy Propertiesof Epoxy Resin Modified with Functionalized Graphene Oxide ContainingPhosphorus and Silicon Elements

摘要

Phosphorus- and silicon-modified graphene oxide was prepared to improve the thermal stability and flame retardancy properties of epoxy resin. 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and vinyltriethoxysilane (VTES) were successfully grafted onto the surface of graphene oxide (GO) through solvothermal synthesis and hydrolysis–condensation reaction, respectively. Subsequently, the functionalized graphene oxide grafted by DOPO and VTES (DOPO–VTES–GO) was incorporated into the epoxy resin by the solution blending method. The effect of DOPO–VTES–GO on the thermal stability and flame-retardant properties of epoxy resin was systematically studied. Thermogravimetric analysis showed that the thermal stability and char residue yield of DOPO–VTES–GO/epoxy were increased obviously compared with those of pure epoxy resin and DOPO–GO/epoxy. Cone calorimeter test results showed that DOPO–VTES–GO/epoxy had better flame retardancy than pure epoxy resin and DOPO–GO/epoxy on reducing the peak of heat release rate, total heat release, and totalsmoke production. Furthermore, the char residue after the cone calorimetertests was investigated by scanning electron microscopy–energy-dispersiveX-ray spectrometry, Raman spectroscopy, and Fourier transform infraredmeasurements. These results demonstrated that the DOPO–VTES–GOcan enhance the graphitization degree of char residues and promotethe formation of the thermally stable char. In addition, the mechanismof flame retardancy was proposed, and DOPO–VTES–GO exertsthe synergistic effect mainly by means of catalytic charring in thecondensed phase and capturing hydroxyl or hydrogen radicals from thermaldecomposition of epoxy resin in the gas phase. This work providesnovel insights into the preparation of phosphorus–silicon–grapheneoxide ternary synergistic flame retardants for thermosetting polymermaterials.