A novel flame retardant consisting of functionalized Salen-Ni based polyphosphazene microspheres

A functionalized cross-linked polyphosphazenes microsphere (Salen-PZN-Ni@DHPP-PTS) was prepared by wrapping Salen-Ni basis polyphosphazenes (Salen-PZN-Ni) with a kind of hybrid flame retardant (DHPP-PTS) to improve the flame retardancy and smoke suppression properties of epoxy (EP) composites. Thermogravimetric analysis showed that the addition of Salen-PZN-Ni@DHPP-PTS greatly improved the thermal stability of the EP composites. The addition of 5 wt% Salen-PZN-Ni@DHPP-PTS remarkably improved the fire safety of EP, which was illustrated by the results of the cone calorimeter. For example, the peak heat release rate and total heat release rate of the EP composites were reduced by 44.2% and 33.1%, respectively. The limiting oxygen index value of 5% Salen-PZN-Ni@DHPP-PTS/EP composite reached 29.8% and UL-94 achieved V-1 rating. In addition, the introduction of Salen-PZN-Ni@DHPP-PTS effectively suppressed the production of toxic CO and other volatiles. Meantime, the synergistic effect between Salen-PZN-Ni and DHPP-PTS was found. The potential flame retardant mechanism of Salen-PZN-Ni@DHPP-PTS is regarded as the synergistic catalytic carbonization effect and the extremely thermally stable components forming. Enhanced fire safety of EP composites by synergistic interaction of various components (nickel and DHPP-PTS) with polyphosphazenes microspheres.