Effects of silicon additive as synergists of Mg(OH)₂ on the flammability of ethylene vinyl acetate copolymer

The present work dealt with the effects of nine kinds of silicon additives on flame retardancy of ethylene-vinyl acetate copolymer (EVA)/magnesium hydroxide [Mg(OH)₂] composites, as well as mechanical properties. The limiting oxygen index (LOI) test, horizontal fire test, vertical fire test, and cone calorimeter test were employed to evaluate flame retardancy of the composites. It was found that different silicon additives had different synergistic effects with Mg(OH)₂ on flame retardancy of the EVA matrix and exerted different influences on mechanical properties of the composites. The incorporation of organic montmorillonite (MMT) clay or silicone rubber not only made the composite reach FH-1 rating in the horizontal fire test and FV-1rating in the vertical fire test, respectively, but also dramatically reduced the peak rate of heat release (Peak RHR) and increased the fire performance index (FPI) and ignition time (IT). The composites filled with precipitated SiO₂ exhibited the longest IT, the highest FPI, and FV-1 rating. However, only the composites filled with silicone rubber could attain a balance between mechanical properties and flame retardancy.