In-situ growth of boron nitride for the effect of layer-by-layer assembly modified magnesium hydroxide on flame retardancy, smoke suppression, toxicity and char formation in EVA

Abstract

This work investigates the application of polyphosphazene (PZN) modified magnesium hydroxide (MH) crosslinked by boric acid (BA) (MH-PZPI-BA) for simultaneous flame retardant, smoke suppression and mechanical properties enhancement of ethylene-vinyl acetate (EVA) nanocomposites. The MH-PZPI-BA was prepared by a PZN nano-coating made from hexachlorocyclotriphosphazene and branched polyethyleneimine (bPEI) was deposited onto the MH followed by BA cross-linking bPEI. Then MH-PZPI-BA was incorporated into EVA, and the properties were examined. Compared with pure EVA, the peak heat release rate and total heat released decreased by 82.7% and 44.2%, respectively. The MH-PZPI-BA has an excellent performance in reducing the smoke, CO, and CO2 production rates. The "tortuous path" effect of the boron nitride of in-situ growth hindered the transfer of volatile products, and led to the formation of a compact and robust char layer in condensed phase during combustion, in the combustion process of EVA/MH-PZPI-BA. The tensile strength and elongation at break are improved by 26.1% and 33.5%, respectively.