Multiple synergistic effects of silicon-containing flame retardants and DOPO derivative enhance the flame retardancy of epoxy resin

Presuming that the filler structure can regulate the flame retardancy of polymeric materials, this study investigates the flame-retardant properties of EP-containing phosphorus/silicon. Sepiolite (Sep) fibers and SiO2 nanoparticles are shown to synergistically enhance the flame retardancy of EP-based composites. The underlying retardant mechanisms of the synergistic effect are also discussed and the mechanical properties of EP-based composites are examined. Among the prepared composites, EP/DiDOPO/Sep5&SiO25 (DiDOPO = derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) achieved the maximum limiting oxygen index (29.4%) and a UL-94 V-0 rating. The EP/DiDOPO/Sep5&SiO25 composites also minimized the peak heat-release rate and total heat release and maximized the strength and modulus.