Magnesium hydroxide is a white solid powder with the molecular formula: Mg(OH)?, a relative molecular weight of 58.33. It belongs to the hexagonal crystal system or exists as amorphous flake crystals, with a density of 2.39 g/cm3, a refractive index of 1.561–1.581, a Mohs hardness of 2–3, and a volume resistivity of 10?–101? Ω·cm. It is poorly soluble in water (solubility at 18°C is 0.0009 g/100 mL) and insoluble in a 1 mol/L sodium hydroxide aqueous solution, but soluble in strongly acidic solutions. When 2 g of magnesium hydroxide is suspended in 50 mL of water, the pH of the system is 10.3. It can be widely used as a flame retardant and smoke suppressant in polymer materials such as polypropylene, polyvinyl chloride, and unsaturated resins. Magnesium hydroxide has a high thermal decomposition temperature, which helps accelerate extrusion speed, shorten molding time, and also improves flame retardant efficiency. It is widely applicable in fields such as polyesters, epoxy resins, coatings, fiber products, polypropylene, polyacrylonitrile, polyvinyl acetate, wires, cables, wood, rubber, paints, and polyvinyl chloride.