Flame retardancy and smoke suppression effect of zinc borate-graphite intercalation compound/Fe2O3 on silicone rubber foams

To enhance the flame retardancy and smoke suppression of silicone rubber foams (SRFs), a novel flame retardant, zinc borate-graphite intercalation compound (ZB-GIC), was synthesized and used in conjunction with Fe2O3. The results showed that ZB-GIC markedly improved the flame retardancy and smoke suppression of SRFs, and Fe2O3 significantly improved the smoke suppression of SRFs. ZB-GIC and Fe2O3 had an excellent synergistic effect on flame retardant and smoke suppression. 5 wt% ZB-GIC synergistically with 5 wt% Fe2O3 resulted in SRFs passing the UL-94 V-0 rating, whose limiting oxygen index (LOI) value reached up to 43.7%. Its peak heat release rate (PHRR), total heat release (THR), peak smoke production rate (PSPR), and total smoke production (TSP) decreased by 67.42%, 89.55%, 76.86%, and 91.67% compared to pure SRF. The ZB-GIC produced incombustible gas and a large amount of H2O when heated, which reduced the intensity of gas-phase combustion. The ZB filled the interlayer gaps formed after the expansion of GIC to enhance the strength of the char layer, and Fe2O3 further strengthened the char layer. Our work has greatly reduced the fire hazards of SRFs and provided a promising flame retardant for the large-scale production of high-performance SRFs.