Magnesium hydroxide is a promising inorganic flame retardant filler for polymer matrix composites. Like aluminum hydroxide, magnesium hydroxide flame retardant is to rely on the heat when the chemical decomposition of heat absorption and release of water and play a flame retardant effect, so it has the advantages of non-toxic, low smoke and decomposition of magnesium oxide chemical stability, does not produce secondary pollution and so on. However, compared with halogen-containing organic flame retardants, to achieve a considerable flame retardant effect, the filling amount is generally more than 50%. Because magnesium hydroxide is an inorganic substance, the compatibility of the surface and the high polymer base material is poor, such a high filling amount, if it is not surface modified, filled into the high polymer material, will lead to the decline of the mechanical properties of the composite material. Therefore, it must be surface modified to improve its compatibility with the polymer base material, so that the mechanical properties of the filling material will not decrease, and even some of the mechanical properties of the material will be improved.

Experiments show that the unmodified magnesium hydroxide exists in the form of agglomerates in PP. Although the powder itself is very fine, due to the incompatibility between the surface of the particles and the PP matrix, there are obvious boundaries and even voids between the particle agglomerates and the PP matrix. Due to the brittle fracture of magnesium hydroxide particles after the escape of the formation of the hollow, indicating that the unmodified magnesium hydroxide in PP only play a role in filling flame retardant, but not with PP chemical bonding. After surface modification of magnesium hydroxide in the PP matrix dispersed evenly, the particles are mostly in the form of primary particles or small agglomerated particles dispersed in the material.