Effect of Al‐based metal‐organic frameworks/halloysite nanotubes on the flame retardancy of silicone rubber foam

Abstract Two kinds of Al‐based metal‐organic frameworks (Al‐MOFs), MIL‐53(Al), and MIL‐96(Al), were synthesized by the solvothermal method and then characterized using SEM, XRD, and FTIR. The Al‐MOFs and halloysite nanotubes (HNTs) were blended and added to silicone rubber foams (SiFs). The mechanical properties and flame retardancy of the composites were tested and analyzed using universal tensile tester, limiting oxygen index (LOI), vertical combustion tester, cone calorimeter, TG, SEM, EDS, and FTIR. The results show that Al‐MOFs synthesized by the solvothermal method have high crystallinity and purity. Compared with pure SiFs, the LOI of SiFs with 2 wt% MIL‐53(Al) and 2 wt% HNTs increased to 29.4%, while total heat release and total smoke release decreased by 36.9% and 32.4%. The flame retardant mechanism of the composites is mainly reflected in the condensed phase. MIL‐53(Al) and HNTs can synergistically promote the formation of a dense carbon layer, blocking heat and oxygen from entering the SiFs matrix.