Construction of a novel halogen-free and phosphorus-free and synergistic flame retardant system with low addition in simultaneously improving the flame retardancy, water resistance and mechanical properties for silicone rubber

To solve the bottleneck problems of flame-retarding silicone rubber (SR), a halogen-free, phosphorus-free and synergistic flame retardant system was prepared by introducing hydrophobic natural product (Gum Arabic, GA) intercalated layered double hydroxide (H-GA@LDH) and multi-walled carbon nanotubes (MWCNT). Promi-nently, when the total amount of flame retardant is only 7 phr, SR/H-GA@LDH6.0/MWCNT1.0 can reach the limiting oxygen index (LOI) value of 29.4% and UL-94 V-0 rating with the flame retardant index of 2.06. And the LOI value of SR/H-GA@LDH6.0/MWCNT1.0 is decreased by only 1.3% compared with that of SR by 6.9% after water resistance tests. In addition, the peak heat release rate (pHRR) and total heat release rate (THR) of SR composites are decreased by 22.14% and 12.43%. Compared with pure SR, the tensile strength and elongation at break of SR-8 are increased by 115.63% and 23.85%. In this condition, an excellent balance for simultaneously improving flame retardancy, water resistance and mechanical properties has been achieved. Therefore, this paper has provided an effective strategy with halogen-free and phosphorus-free materials for achieving the goal of flame-retarding SR with high performance and breaking the limitation of traditional contaminative and toxic phosphorus-based or halogen-based flame retardants.