Synthesis of multi‐element hybrid polyphosphonitrile microspheres and their flame retardant application in epoxy resins

Abstract In this paper, Salen‐Ni basis polyphosphazene microsphere (Salen‐PZN‐Ni), boric acid (BA), and 3‐aminopropyltriethoxysilane (KH‐550) were used as raw materials to prepare a new flame retardant Salen‐PZN‐Ni@BA@KH‐550 by surface modification. The thermal and flame retardant properties of epoxy resin (EP) composites were studied. The introduction of Salen‐PZN‐Ni@BA@KH‐550 refined the thermal stability of EP composites, as well as the amount of carbon residue at 800°C. At 5 wt% of Salen‐PZN‐Ni@BA@KH‐550, the limiting oxygen index (LOI) of EP composites is increased from 25.4% to 30.5% and UL‐94 has been achieved with a V‐1 rating. Meanwhile, the mechanical properties of Salen‐PZN‐Ni@BA@KH‐550/EP composites were also improved. In addition, the good char formation ability of Salen‐PZN‐Ni@BA@KH‐550 caused the reduction of peak heat release rate, total heat release rate, maximum average heat release rate and total smoke generation of the EP composites. All these results indicate that Salen‐PZN‐Ni@BA@KH‐550/EP composites have a wider range of applications.