Functionalized Mesoporous Silica Fire Retardant via Hierarchical Assembly for Improved Fire Retardancy of Unsaturated Polyester

Unsaturated polyester (UP) has many important industrial applications, including transportation, building materials, and electrical insulation. However, UP resins are extremely flammable, thus restricting their real-world applications. Herein, we report a mesoporous silica-based ternary flame retardant (NF@SiO 2 -D) for UP by loading nickel ferrite and dimethyl methylphosphonate (DMMP) via hierarchical assembly. NF@SiO 2 -D acts as a fire extinguisher of UP through the combined effect of mesoporous silica, nickel ferrite, and DMMP. The peak and total heat release rates of the UP matrix decreased by 36.3% and 36.9%, respectively, after the incorporation of 10 phr NF@SiO 2 -D. More importantly, when NF nanoparticles were present, the smoke production of the UP matrix was reduced by 41.5% compared to the control samples without NF nanoparticles. In addition, 20 phr of NF@SiO 2 -D enabled the UP to achieve a self-extinguishing ability and a desired V-0 grade in the UL 94 test. The flame-retarding UP composites with NF nanoparticles also exhibited better thermal stability and T g than the control samples. The resultant fire-retardant UP composites are anticipated to find more industrial applications.