It is well known that magnesium hydroxide can be used as flame retardant, which can limit the fire potential. Magnesium hydroxide decomposes water by heating and absorbs a large amount of latent heat at the same time, thus inhibiting the rise of polymer temperature, continuing its thermal decomposition and reducing the burning speed. This reduces the actual temperature of resin in the flame, and has the cooling effect of inhibiting the decomposition of polymer and the generation of flammable gas.

Magnesium hydroxide produced after decomposition is a good refractory. It can cut off oxygen supply, prevent the flow of flammable gas, and help improve the flame resistance of resin. Moreover, the thermal decomposition temperature of magnesium hydroxide is up to 340 C. Therefore, as a flame retardant, magnesium hydroxide has excellent flame retardancy.

Magnesium hydroxide can form a thicker carbon oxide layer in medium filling. The formation of carbonization layer prevents the entry of heat and oxygen and the escape of flammable gases, which makes the dehydration dilution and endothermic cooling play a greater role. Adding magnesium hydroxide reduces the initial oxidation decomposition temperature, and decreases with the increase of the amount of magnesium hydroxide. In addition, the magnesia produced enables excellent refractories to cover the surface of polymers and improves the flame resistance of polymers.