Flame-retardant synergistic effect of hydroquinone bis(diphenyl phosphate) and tris(2-hydroxyethyl) isocyanurate on epoxy resin

In this study, epoxy resin (EP) composites were prepared by the incorporation of hydroquinone bis(diphenyl phosphate) (HDP) and tris(2-hydroxyethyl) isocyanurate (THEIC), and the synergistic effects of HDP and THEIC on the flame retardancy of EP were investigated. The flame retardancy of EP composites was systematically evaluated by measuring limiting oxygen index (LOI), UL-94 vertical burning tests and a cone calorimeter. The results indicate that the synergistic effect of the addition of 15% HDP and 15% THEIC in the composite EP-4 is the best. Compared with neat EP, the LOI of EP-4 has increased from 21.7 to 27.5%, and UL-94 reached V-0. The heat release rate (HRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP) of EP-4 in the cone calorimeter test decreased by 81.14, 41.42, 72.57 and 53.61%, respectively. The release rates of CO 2 and CO were also significantly reduced, indicating a good synergistic effect between HDP and THEIC. Furthermore, the synergistic flame-retardant mechanism between HDP and THEIC has been thoroughly studied by scanning electron microscopy (SEM) and thermogravimetric analysis/infrared analysis (TG-IR). The results show that HDP/THEIC can effectively strengthen the carbon layer structure resulted from the composite after combustion and increase the flame retardancy of the condensed phase. Meanwhile, PO, PO 2 radicals and NH 3 produced by the degradation of HDP and THEIC are also beneficial to improve the flame retardancy of the gas phase.