Flame-Retardant Performance of Epoxy Resin Composites with SiO₂ Nanoparticles and Phenethyl-Bridged DOPO Derivative

Flame retardancy of epoxy resin (EP) plays a vital role in its applications. When inorganic nanomaterials form inorganic/organic nanocomposites, they exhibit special flame-retardant effects. In this study, EP nanocomposites were prepared by the incorporation of SiO₂ nanoparticles and phenethyl-bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative (DiDOPO), and the synergistic effects of SiO₂ nanoparticles and DiDOPO on the flame-retardant performance of EP were discussed. Results indicated that the introduction of only 15 wt % SiO₂ and 5 wt % DiDOPO in EP leads to the increase in the limiting oxygen index from 21.8 to 30.2%, and the nanocomposites achieve the UL-94 V-0 rating. Thermogravimetric analysis revealed that char yield increases with the increase in the SiO₂ content of the nanocomposites and that an increased amount of thermally stable carbonaceous char is formed. SiO₂ nanoparticles can improve the thermal stability and mechanical performance of EP; hence, the nanoparticles can serve as an efficient adjuvant for the DiDOPO/EP flame-retardant system.