Synthesis of Fe2O3/ZnFe2O4/g-C3N4@ZIF-8 composites: Enhancing thermal stability and flame retardancy in polyurea

Metal–organic frameworks (MOFs) have garnered significant attention in recent years due to their potential application in flame-retardant polymeric materials. In this work, Fe₂O₃/ZnFe₂O₄/g-C₃N₄@ZIF-8 flame retardants were synthesized via solvothermal and calcination techniques, and their elemental composition and morphologies were thoroughly characterized. The flame retardancy of polyurea (PUA) composites incorporating varying dosages of these flame retardants was evaluated using cone calorimetry tests (CCT). The findings demonstrate that the incorporation of Fe₂O₃/ZnFe₂O₄/g-C₃N₄@ZIF-8 significantly enhanced the flame retardant properties of PUA composites. With the addition of 3 wt% of the flame retardant, the peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP), and total CO yield (TCO) of the PUA composites decreased to 890.82 kW/m², 131.34 MJ/m², 12.30 m², and 2.39 g, respectively, reflecting reductions of 33.59%, 18.59%, 29.40%, and 47.93% compared with pure PUA. The flame-retardant mechanism was systematically analyzed in both the condensed and gas phases. This study provides a robust experimental foundation and novel insights that contribute to the development of advanced flame-retardant coating materials.