Magnesium hydroxide is a kind of inorganic flame retardant filler with good application prospect. Like aluminum hydroxide, magnesium hydroxide flame retardant plays a role of flame retardancy by absorbing heat and releasing water when heated. Therefore, it has the advantages of non-toxic, low smoke, stable chemical properties of magnesium oxide generated after decomposition and no secondary pollution. However, compared with halogen-containing organic flame retardants, to achieve a considerable fire-retardant effect, the filling amount is generally more than 50%. Due to the inorganic magnesium hydroxide, the compatibility between the surface and the polymer base material is poor. Such a high filling amount, if it is not treated by surface modification, will lead to the decline of the mechanical properties of the composite material after filling into the polymer material. Therefore, it is necessary to modify its surface to improve its compatibility with polymer based materials, so that the mechanical properties of the filling materials do not decline, or even improve some of the mechanical properties of the materials.

The results show that the unmodified magnesium hydroxide exists in the form of aggregate in PP. although the powder itself is very fine, there are obvious boundaries or even cavities between the particle aggregate and PP matrix due to the incompatibility between the particle surface and PP matrix. Because of the voids formed after the magnesium hydroxide particles escape during brittle fracture, it shows that the unmodified magnesium hydroxide only plays a role of filling and flame retardant in PP, and does not chemically bond with PP. After surface modification, magnesium hydroxide is dispersed uniformly in PP matrix, and most particles are dispersed in the material in the form of primary particles or small agglomerated particles.