Effects of particle size on the properties of Mg(OH)2-filled polypropylene with high filler content

Magnesium hydroxide is an environmental friendly inorganic flame retardant filled in the polymer materials, its morphology and size can have a great influence on the properties of the doped polymer material. Four kinds of magnesium hydroxide particles with the same crystal phase and different particle sizes were prepared by coprecipitation method, and were doped in polypropylene (PP) with filling level of 50%(wt), respectively. Results reveal that the four kinds of magnesium hydroxide particles are highly dispersed in PP, and improve the flame retardancy of the PP. The Mg(OH)2 with particle size of ≤150 nm or ≥800 nm shows better flame-retardant effect on PP material. However, magnesium hydroxide doping will destroy the mechanical properties of PP. The Mg(OH)2 with the particle size of 800~1500 nm has a relatively better compatibility with PP, and the MH/PP composite shows the best mechanical properties.