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

Abstract

Epoxy resin (EP) is a high-performance polymer, 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) has been synthesized using porphyrin as the matrix and ZIF-8 as the shell layer. The uniform dispersion of ZIF-8@Co-PMF in EP matrix results in a blend exhibiting outstanding thermal stability, flame retardant, and smoke suppression performance. Specifically, the maximum thermal degradation rate (Rmax) of the EP blend containing 5 wt% ZIF-8@Co-PMF decreased by 39.3%, while the char residue increased by 24.8%. Additionally, flame retardant performance, compared to that for pure EP, the peak heat release rate (PHRR), total heat release (THR), production rates of carbon monoxide (COP) and carbon dioxide (CO₂P) for the EP/5%ZIF-8@Co-PMF blends are 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.