Magnesium hydroxide belongs to the strong alkali, the solubility of magnesium hydroxide is very small, the alkaline of the solution is very weak, and sometimes it is treated as a weak base. Heating to 623K (I .e. 350 ℃) will carry out dehydration decomposition: Mg(OH)2 → MgO H2O, soluble in acid or ammonium salt solution.

Like magnesium oxide, it easily absorbs carbon dioxide in the air and gradually forms a basic carbonate with a composition of 5MgO · 4CO2 · xH2O. It decomposes into magnesium oxide and water at temperatures above 350°C, but only when the temperature reaches above 1800°C can it be completely dehydrated.

Application of Magnesium Hydroxide

(I) magnesium hydroxide reaction activity, buffer performance, thermal decomposition performance, adsorption force, etc. are relatively good, not only can be used as chemical materials and intermediates, or a can be used for rubber, plastics, resins and fibers and other polymer materials in the industry of green flame retardants and additives.

In the field of environmental protection, magnesium hydroxide is mainly used as flame retardant, heavy metal removal agent, acid wastewater treatment agent, flue gas desulfurization agent and so on.

(II) magnesium hydroxide is an excellent flame retardant for plastics and rubber products. In terms of environmental protection, as a flue gas desulfurization agent, it can replace lime and caustic soda as a neutralizing agent for acid-containing wastewater. It can also be used as an oil additive to play the role of desulfurization and corrosion protection.

In addition, magnesium hydroxide can also be used in the electronics industry, medicine, refined sugar, as well as used as insulation materials and the manufacture of other magnesium salt products.

(III) magnesium hydroxide is a new type of filled flame retardant, through the thermal decomposition is released by the binding water, absorb a large amount of latent heat, reduce the surface temperature of the filled synthetic material in the flame, with the effect of cooling the combustible gas and inhibiting the decomposition of the polymer. The magnesium oxide produced by decomposition is a good refractory material and can also help improve the fire resistance of synthetic materials. At the same time, the water vapor released by magnesium oxide can also be used as a smoke suppression agent.

In the rubber and plastic industry, magnesium hydroxide is recognized as an excellent flame retardant with flame retardant, filling and smoke suppression. Widely used in chemical, building materials, rubber, plastics and electronics, unsaturated polyester and paint, paint and other polymer materials. Especially for mine air guide coated cloth, flame retardant tarpaulin, flame retardant aluminum-plastic board, PVC core conveyor belt, PVC wire and cable material, mine cable sheath, cable accessories flame retardant, smoke, antistatic, can replace aluminum hydroxide, with excellent flame retardant effect. Compared with similar inorganic flame retardants, magnesium hydroxide has better smoke suppression effect.

In the process of production, use and waste, magnesium hydroxide does not produce harmful substances, but also can neutralize the acidic and corrosive gases generated in the combustion process. When magnesium hydroxide is used alone, the dosage is generally 40%-60%. Magnesium hydroxide and substrate resin has a good compatibility, is an ideal flame retardant thermoplastic resin and rubber products, in the adhesive is often used as an additive type flame retardant filler or flame retardant. Industrially used in the manufacture of magnesium salt, active magnesium oxide, fine ceramics, thermal insulation materials, color TV picture tube cone glass coating, acid wastewater neutralizer, oil anti-corrosion additives, flue gas desulfurization agent, drugs, refined sugar, etc.

(IV) magnesium hydroxide can be used as a flame retardant or flame retardant filler added to polypropylene, polyethylene, polystyrene and ABS resin, has good smoke and flame retardant effect, usually added 40-20 parts (due to the differences in the indicators of various industries, depending on the specific circumstances of each industry). However, it is necessary to treat the particle surface with an anionic surfactant, and an inexpensive anionic surfactant such as an alkali metal salt of a fatty acid or an alkyl sulfate and a sulfonated succinate may be used in an amount of about 3%. Can also be used for sugar refining, magnesium salt manufacturing, pharmaceutical industry, daily chemical industry, etc.

(V) milky suspensions of magnesium hydroxide are used medically as antacids and laxatives.