Synthesis of core–shell mesoporous hollow silica nanocomposite microspheres and their flame-retardant performance in epoxy resins

Epoxy resin (EP) is highly flammable and exhibits high heat and smoke release during combustion. In addition, Prussian blue analogue nanoparticles are prone to aggregation, which limits their flame-retardant efficiency. To address these issues, a hierarchical core–shell flame retardant, HMS@PDA@NiCo PBA, was prepared via an in situ growth strategy. In this system, polydopamine (PDA) and Ni–Co Prussian blue analogue (NiCo PBA) were coated onto mesoporous hollow silica (HMS). The material was incorporated into EP, and the properties of the resulting composites were investigated.The results show that NiCo PBA was successfully anchored on the surface of HMS@PDA, and the composite retained the mesoporous structural features. Compared with neat EP, the addition of 3wt% HMS@PDA@NiCo PBA reduced the maximum weight loss rate from 24.7%/min to 18.7%/min. The char yield at 700℃ increased from 21.5wt% to 28.7wt%. The peak heat release rate and total heat release decreased from 1142.10 kW/m² and 115.59 MJ/m² to 840.82 kW/m² and 75.27 MJ/m², corresponding to reductions of 26.4% and 34.9%, respectively. Meanwhile, the tensile strength and impact strength increased to 59.9 MPa and 17.5 kJ/m².This hierarchical structure integrates multiple functions. The combined effects of inorganic shielding, interfacial enhancement, and metal catalysis lead to simultaneous improvements in flame retardancy, smoke suppression, and mechanical properties of EP.