Magnesium hydroxide is a white amorphous powder or colorless hexagonal columnar crystal. Soluble in dilute acid and ammonium salt solutions, almost insoluble in water and alcohol. Easily absorbs carbon dioxide in humid environments. When heated to above 200°C in an alkaline solution, it becomes hexagonal crystal. Decomposes into magnesium oxide and water at 230°C. When the temperature is higher than 500℃, it loses water and turns into magnesium oxide. The aqueous solution is alkaline, pH 9.5~10.5.
Magnesium hydroxide is an excellent flame retardant in the rubber and plastics industry:
It is understood that magnesium hydroxide is a new type of filled Flame retardants release bound water when decomposed by heat and absorb a large amount of latent heat to reduce the surface temperature of the synthetic materials they are filled with in the flame. They have the function of inhibiting polymer decomposition and cooling the generated flammable gases. The magnesium oxide generated 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 it releases can also be used as a smoke suppressant.
Magnesium hydroxide is recognized as an excellent flame retardant in the rubber and plastics industry with the triple functions of flame retardant, smoke suppression and filling. It is widely used in rubber, chemicals, building materials, plastics and electronics, unsaturated polyester and paints, coatings and other polymer materials. Especially for the flame-retardant, smoke-eliminating and anti-static coating of mining air duct coatings, PVC whole-core conveyor belts, flame-retardant aluminum-plastic panels, flame-retardant tarpaulins, PVC wire and cable materials, mining cable sheaths, and cable accessories. , can replace aluminum hydroxide and has excellent flame retardant effect.
Compared with similar inorganic flame retardants, magnesium hydroxide has better smoke suppression effect. Magnesium hydroxide does not emit harmful substances during production, use and disposal, and it can also neutralize acidic and corrosive gases produced during combustion. When used alone, the dosage is generally 40% to 60%.
It has good compatibility with base resin and is an excellent flame retardant for thermoplastic resins and rubber products. It is often used as an additive flame retardant or flame retardant filler in adhesives. The reference dosage is 40 ~200 copies.
It should be noted that: like aluminum hydroxide, magnesium hydroxide flame retardant relies on chemical decomposition to absorb heat and release water when heated to play a flame retardant effect, so it is non-toxic and low-smoke And the magnesium oxide generated after decomposition has the advantages of stable chemical properties and no secondary pollution. However, compared with halogen-containing organic flame retardants, to achieve considerable flame retardant effects, the filling amount generally needs to reach more than 50%. Since magnesium hydroxide is an inorganic substance, its surface has poor compatibility with the polymer base material. With such a high filling amount, if it is not surface modified, it will lead to composite materials after being filled into the polymer material. The mechanical properties decrease. Therefore, it must be surface modified to improve its compatibility with the polymer base material so that the mechanical properties of the filling material do not decrease, and even some of the mechanical properties of the material are improved.
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