SiO2/MOFs-based synergistic flame retardants provide enhanced fire safety for epoxy resins

To improve the inherent flammability of epoxy resin (EP), a new synergistic flame retardant (SiO2/PANI/ZIF-67) with silica, polyaniline (PANI) and zeolitic imidazolate framework-67 (ZIF-67) was synthesized successfully via an electrostatic interaction and chemical bonding technique. With the addition of 6% SiO2/PANI/ZIF-67, the limiting oxygen index (LOI) of as-obtained EP composite reaches up to 28.0%. The total heat release (THR), total smoke production (TSP) and total CO production (TCOP) of the composite are significantly decreased to 44.06%, 45.05% and 44.05% respectively. The synergistic role of SiO2, PANI and ZIF-67 induces formation of a dense SiO2-C layer, which greatly reduces emission of smoke gas and heat, and subsequently increases the fire safety of EP. Furthermore, the presence of organic-inorganic hybrid ZIF-67 on surface of flame retardant leads to its strong interface adhesion and well dispersibility in EP matrix. This work provides a simple route for designing and preparation of SiO2/MOFs-based synergistic flame retardants, which is of great significance to improve fire safety of epoxy resins.