Synthesis of a novel organic–inorganic hybrid flame retardant based on porphyrin and MOFs for enhancing the fire safety of an epoxy resin

Abstract

Epoxy resin (EP) is a high-performance polymer that is widely applied and in great demand. However, its inherent flammability severely restricts its practical application and further development. A novel organic–inorganic hybrid flame retardant (ZIF-8@Co-PMF) is synthesized using porphyrin as the matrix and ZIF-8 as the shell layer. The uniform dispersion of ZIF-8@Co-PMF in the EP matrix results in a blend exhibiting outstanding thermal stability, flame retardant property, and smoke suppression performance. Specifically, the maximum thermal degradation rate (R_max) of the EP blend containing 5 wt% ZIF-8@Co-PMF decreased by 39.3%, while that of the char residue increased by 24.8%. Additionally, in the case of flame retardant performance, compared with those for pure EP, the peak heat release rate (PHRR), total heat release (THR), and production rates of carbon monoxide (COP) and carbon dioxide (CO₂P) for the EP/5%ZIF-8@Co-PMF blend decreased by 31.2%, 17.6%, 80.1% and 41.8%, respectively. This may be attributed to the uniform dispersion of ZIF-8@Co-PMF in the EP matrix, enabling effective cooperation among the flame retardant constituents. Transition metals, in the presence of phosphates, promote the formation of a compact, stable char layer. While achieving the phosphorus compound, a radical trapping effect and non-flammable gas dilution process may also occur.