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Why can aluminum hydroxide be used as a flame retardant?

  • 2020-03-30

Why can aluminum hydroxide be used as a flame retardant? Application performance of aluminum hydroxide in the market

Aluminum hydroxide has high chemical stability at normal temperature. After being heated up to 200 degrees, it will endothermically decompose and release three crystal waters. The heat absorption of aluminum hydroxide reaches 878J per gram. When the temperature is 300 ° C, two crystal waters are lost and transformed into boehmite. The endothermic dehydration process delays the combustion of the polymer. Aluminum hydroxide is equivalent to a radiator, which slows the combustion rate. At the same time, the water vapor released not only dilutes the combustion gas, but also participates in the reaction of the condensed phase. The endothermic decomposition is based on hydrogen. Alumina absorbs a large amount of heat when it decomposes, and only emits steam when it is decomposed by heat without generating toxic, flammable or corrosive gases. Therefore, aluminum hydroxide is used as a flame retardant filler.

Aluminum hydroxide flame retardant is an important additive, which can make the material flame-retardant, self-extinguishing and smoke-suppressing, and can effectively improve the material's safety performance. Aluminum hydroxide inorganic flame retardant has the advantages of relatively good thermal stability, no corrosive gas, non-volatile, long-lasting effect, no toxicity, low price, etc., and has little harm to the environment. Therefore, it is based on the requirements of environmental protection and fire safety Inorganic flame retardants that are good for the environment will gradually replace halogen-containing organic flame retardants.

The main varieties of inorganic flame retardants are aluminum hydroxide, magnesium hydroxide, magnesium oxide, zinc borate, antimony trioxide, and the like. Aluminum hydroxide has abundant sources, and its price is much cheaper than bromine-based flame retardants. It has stable physical and chemical properties at room temperature, is non-toxic, and does not cause secondary pollution during combustion. It is known as a pollution-free flame retardant at home and abroad. It not only has high whiteness value, but also has excellent chromaticity index. Aluminum hydroxide overview: Aluminum hydroxide (Aluminiumhydroxide), chemical formula Al (OH) 3, is a hydroxide of aluminum. It is a kind of base. Because it has a certain acidity, it can also be called aluminate (H3AlO3), but it actually generates meta-aluminate when it reacts with the base, so it is usually regarded as monohydrate meta-aluminate. (HAlO2? H2O). Molecular formula: Al (OH) 3, Al2O3? 3H2O or H3AlO3 molecular weight: 78. The relative density is 2.42 and the Mohs hardness is 3.0.

It has the characteristics of non-toxic, odorless, good dispersibility, high whiteness and low iron content, referred to as ATH. ATH is dehydrated and decomposed by heat. The heat absorption is 1967.2J / KJ, which can effectively inhibit the temperature rise and thermal degradation of the polymer. The thermal decomposition of aluminum hydroxide releases a large amount of water vapor to dilute the flammable gas and suppress the combustion spread. At the same time, the produced high temperature resistant Al2O3 forms a dense protective layer on the polymer surface, blocking the air and preventing the flame from further spreading. High temperature resistant Al2O3 can promote polymer carbonization, adsorb solid particles, and inhibit dense smoke generation.

Aluminum hydroxide use: Aluminum hydroxide is one of the world's largest non-polar flame retardants. It has triple functions of flame retardant, smoke elimination and anti-melt droplet. It has no secondary pollution during combustion, and does not produce toxic and corrosion during pyrolysis. A gas that absorbs heat and releases water vapor, so that the polymer material has flame retardant self-extinguishing performance. It not only has good dispersion properties, but also can interact with flame retardants such as magnesium hydroxide to exert flame retardant synergies. Because of its low polarity, aluminum hydroxide has good compatibility with high-molecular materials such as polymers. Therefore, aluminum hydroxide has been widely used, and its amount of use has also increased year by year.

Scope of application: thermosetting plastics, thermoplastics, synthetic rubber, coatings and building materials industries.

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