Superior flame retardancy and smoke suppression of epoxy resins with zinc ferrite@polyphosphazene nanocomposites

To impart epoxy resin (EP) with excellent flame retardancy and smoke suppression, we prepared a novel inorgianic-organic nanocomposite flame retardant, zinc ferrite@polyphosphazene (ZF@PZS). The inorganic zinc ferrite plays a role in catalytic carbonization, improving char yields. The organic polyphosphazene helps zinc ferrite improve its compatibility and flame retardancy. Through synergistic effects, ZF@PZS exhibited excellent flame-retardant and smoke-suppression properties in the EP matrix. Compared to neat EP, the limiting oxygen index of the epoxy with 5 phr ZF@PZS increased from 24.6 % to 32.1 % and reached UL94 V-0 rating; the peak heat release rate, peak smoke production rate, and carbon monoxide production of EP composites also decreased by 37 %, 50 %, and 39 %, respectively. Condensed and gas phase analysis indicated that ZF@PZS helps epoxy generate more dense, stable, rigid residues and less pyrolysis volatile products, improving flame retardancy compared to ZF and PZS alone. Besides, the storage modulus of the composite was increased.

Automated summary

In order to enhance the flame retardancy and smoke suppression of epoxy resin (EP), a novel inorganic-organic nanocomposite flame retardant, zinc ferrite@polyphosphazene (ZF@PZS) was developed. The combination of inorganic zinc ferrite and organic polyphosphazene improved the compatibility and flame retardant performance. The synergistic effects of ZF@PZS showed excellent flame retardant and smoke suppression properties in the EP matrix. Compared to neat EP, the EP with 5 phr ZF@PZS exhibited higher limiting oxygen index, lower heat release rate, smoke production rate, and carbon monoxide production. Furthermore, the addition of ZF@PZS resulted in the generation of denser, more stable, and rigid residues, leading to improved flame retardancy.