Magnesium hydroxide is currently the most studied and the fastest growing green flame retardant, it has no secondary pollution, good thermal stability, non-volatile, no precipitation, no toxic gas, no corrosion of processing equipment, smoke abatement effect is significant, efficient substrate into carbon and many other advantages, and rich in magnesium resources. However, the magnesium hydroxide prepared by the regular method has strong polarity and hydrophilicity, the grain tends to be secondary coagulation, the dispersion is poor, the compatibility with the non-polar polymer material is very poor, and the interface is difficult to form a good combination and adhesion. Therefore, with the increase of the content of magnesium hydroxide in the polymer material, its processing performance and mechanical properties also drop sharply, so that its application is limited. In order to make magnesium hydroxide better used for flame retardant polymer materials, there are mainly the following methods:

1. Ultrafine particle size. At the processing temperature of polymer materials, magnesium hydroxide is present in the system as particles. Generally speaking, when the filling amount is the same, the finer the particles of magnesium hydroxide, the more uniform the dispersion, the more obvious the flame retardant effect, the smaller the negative impact on the physical and mechanical properties of the material, and even the effect of plasticizing and enhancing rigid particles.

2. Change the crystal structure of magnesium hydroxide to prepare special morphology (hexagonal flake). Usually, magnesium hydroxide mixed at room temperature is hydrothermally modified, and magnesium hydroxide is crystallized and reorganized in a specific high temperature and high pressure aqueous solution, and the structure and morphology of the crystal are changed through the process of dissolution-re-condensation-crystal growth. Hexagonal flake magnesium hydroxide has a unique advantage as a flame retardant because of its low surface polarity and surface energy and good miscibility with polymer materials. In addition, the hexagonal flake magnesium hydroxide is easy to be mixed with resin, and at the same time has reinforcing properties, so it has good mixing and processing properties.

3. Surface modification of magnesium hydroxide. Magnesium hydroxide is a highly polar inorganic compound with hydrophilicity. Even if magnesium hydroxide is very dry, there is water in the crystal that cannot be ignored, so magnesium hydroxide is very easy to agglomerate when mixing with polymer materials, and has poor compatibility with polymer materials, making the surface of the matrix defective, rough and dull. After the modification of magnesium hydroxide, the surface polarity of the grains is eliminated, so that its dispersion, compatibility and affinity in the polymer material are improved, and it has better flame retardant performance. At the same time, it plays the role of reinforcing agent and improves the mechanical strength of the polymer material.

4 development of magnesium hydroxide composite flame retardant. Select other flame retardants and magnesium hydroxide to compound, the use of flame retardant synergy, effectively improve the flame retardant performance. In the flame retardant technology, the synergistic effect can not only produce more effective flame retardant systems, but also make it possible to reduce the amount of chemical agents used in other flame retardants, and can improve the flame retardant efficiency of flame retardants.