Synergistic Aspects of the Combination of Magnesium Hydroxide and Ammonium Polyphosphate in Flame Retardancy of Ethylene-Vinyl Acetate Copolymer

In this work, flame retardancy of ethylene-vinyl acetate copolymer (EVA) is investigated incorporating Mg(OH)2 (MDH) as flame retardant combined with ammonium polyphosphate (APP) as potential synergist. It is shown that APP is a synergistic agent in EVA-MDH formulations in terms of LOI and cone calorimetry. The interactions between APP and MDH are studied using 25Mg and 31P solid state NMR. The formation of magnesium phosphate stabilizing phosphorus in the system and it is proposed that the combination APP/MDH provides a physical/thermal barrier protecting the substrate; this barrier is constituted of magnesium phosphate glass and MgO-like ceramic. The degradation of the polymeric matrix is slowed and the flow of flammable molecules which issue from the degradation of the polymer is reduced.