Fabrication of layered double hydroxide@ferric decorated polyphosphazene hybrid architecture towards simultaneously improved fire safety, smoke suppression and mechanical strength of epoxy resin

The requirement of high-efficiency flame retardants for epoxy (EP) resin is urgent due to its high flammability. Herein, a hybrid architecture (LDH@PZE-Fe) was synthesized via intercalation by surfactant and interfacial modification by ferric decorated and amino groups-containing polyphosphazene (PZE) to enhance the fire safety and smoke suppression of EP. With the introduction of 2.5 wt% LDH@PZE-Fe, EP/LDH@PZE-Fe achieved UL-94 V-0 rating with a LOI value of 27.5%. Moreover, EP/LDH@PZE-Fe performed superiorly in inhibiting the release of heat and smoke. Such high-efficiency flame-retardancy was ascribed to the combined action both in condensed and gaseous phases, which was verified by analyzing the morphology and structure of the char layer and the composition of pyrolysis gases. Additionally, EP/LDH@PZE-Fe exhibited satisfactory impact strength and enhanced glass transition temperature due to the good compatibility of LDH@PZE-Fe with EP matrix. Therefore, the flame-retardant EP composites had potential applications as highly flame-retardant materials.