Polyphosphazene-wrapped Fe–MOF for improving flame retardancy and smoke suppression of epoxy resins

A novel polyphosphazene (PZS)-wrapped iron 2-methylimidazole metal–organic framework (PZS–Fe–MOF) hybrid with rich N, P, and Fe elements is synthesized, which is incorporated into epoxy resin (EP) to prepare EP/PZS–Fe–MOF composites for improving flame retardancy and smoke suppression of EP via synergistic effect. The results indicate that PZS–Fe–MOF significantly enhances the flame retardant and smoke suppression performances of EP composites. Compared with pure EP, with the addition of 1 mass% PZS–Fe–MOF, the LOI value is increased from 32.3 to 25.8% and EP/1 mass% PZS–Fe–MOF composites pass V-1 rating. Compared with pure EP, the peak heat release rate, total heat release, smoke production rate, and total smoke production of EP/3 mass% PZS–Fe–MOF composites are decreased by 30.2%, 36.9%, 36.6%, and 41.4%, respectively. The results indicate that the improved flame retardancy and smoke suppression are mainly attributed to that the synergistic effect between PZS and Fe-MOF, promoting the formation of compact carbonaceous ceramic layer, which can restrain heat and mass transfer between EP composites and flame zone.