An eco-friendly, bio-inspired and synergistic flame retardant system with outstanding water tolerance and ultra-low addition for silicone rubber

To address the bottleneck problem for flame-retarding silicone rubber (SR) in poor water resistance and low efficiency, a halogen-free and synergistic system was fabricated by the introduction of hydrophobic melamine polyphosphate (MPP) modified by layered double hydroxide (P-MPP@LDH) and expandable graphite (EG) in this paper. Dramatically, the limited oxygen index (LOI) of composites (SR/P-MPP@LDH2.5/EG2.5) can reach as high as 36.4 % with UL-94V-0 rating when the total flame retardant loadings is only 5 phr, revealing the superior efficiency of novel system. Compared with neat SR, the fire risk of SR composites is observably decreased by conducting cone calorimeter tests. Significantly, bio-inspired hydrophobic modification is feasible for the excellent balance in simultaneously improving the flame retardancy, water resistance, and mechanical properties of SR in one system. Based on the analysis for residue and thermal degradation process, the effective flame retardant mechanism for SR composites can be attributed to the joint effect of LDH-catalyzed char-formation and physicochemical synergistic intumescence barrier. Therefore, this paper has provided a new and effective strategy to achieve the goal of flame retardancy with high performance in SR, which offers a new choice for designing and applying rubber composite materials in buildings.