Magnesium hydroxide as a halogen-free flame retardant attracts increasing attention due to environmental regulations and its unique physical properties such as non-toxicity and smoke suppressant ability during combustion. Low-density polyethylene/ethylene vinyl acetate(LDPE/EVA) blends are one of the polyolefins of which the flame retardance is enhanced by compositions containing magnesium hydroxide. Natural magnesium hydroxide flame retardant is available from the mineral brucite by the adjusting size distribution and surface treatment. A synthetic magnesium hydroxide is usually prepared by precipitation and hydrothermal treatment from magnesium salts or hydrolysis of MgO mineral(periclase). Natural and synthetic magnesium hydroxide have been prepared and mixed with LDPE/EVA by melt compounding. The dependence of the particle size and purity of the magnesium hydroxide and various additives for the synergistic effect on the flame retardance of LDPE/EVA has been studied through combustion tests of the polymer composites. The combustion behavior has been tested by limited oxygen index tests and the vertical burning tests of UL-94.

Keywords: Magnesium hydroxide, Flame retardant, LDPE/EVA, Composite, LOI, UL-94.