Hebei Messi Biology Co., Ltd. stated that compared with aluminum hydroxide, the flame retardant and smoke elimination mechanisms of active magnesium hydroxide are very similar to those of aluminum hydroxide, but active magnesium hydroxide has many outstanding advantages that aluminum hydroxide does not have.
First of all, the decomposition temperature of magnesium hydroxide is relatively high, and it does not start to decompose into water and magnesium oxide until it is heated to 340°C. It not only has a good flame retardant effect, but can also meet the market’s demand for flame-retardant FRP with higher temperature resistance.
Secondly, the activated magnesium oxide generated by the decomposition of magnesium hydroxide can easily absorb free radicals and carbon, which can delay the ignition of the material. Its catalytic oxidation function can reduce the generation and escape rate of smoke.
In addition, the smoke suppression ability of magnesium hydroxide is twice that of aluminum hydroxide, which can better prevent environmental pollution during combustion. Moreover, magnesium hydroxide has a short processing flow and low production cost. The market price is only half of that of aluminum hydroxide, but its flame retardant effect is equivalent to adding the same amount of aluminum hydroxide.
In addition, the magnesium hydroxide modified by the coupling agent can increase the amount of magnesium hydroxide in the polyester FRP, which helps to increase the oxygen index value and further reduce costs. It is also feasible to use magnesium hydroxide alone as a flame retardant for polyester FRP.
High-purity magnesium hydroxide is a white amorphous powder, and its aqueous solution is alkaline. Soluble in dilute acid and ammonium salt solutions, almost insoluble in water and ethanol. It is characterized by large particle size, high purity, good whiteness, and easy absorption of carbon dioxide in the air. It is a commonly used raw material in industry. The preparation methods of magnesium hydroxide are:
1. Physical crushing method
The physical crushing method refers to directly crushing the ore, and then through dry coarse grinding and wet ultra-fine grinding to obtain magnesium hydroxide products of the required particle size grade. The more commonly used ore is brucite.
2. Ore calcination hydration method
In this method, the ore is calcined, and the prepared magnesium oxide is hydrated to prepare magnesium hydroxide, which is a process of dissolving magnesium oxide and precipitating magnesium hydroxide, in which the dissolution of magnesium oxide is the control step. Due to different ore compositions, magnesite is more commonly used.
3. Liquid phase precipitation method
There are two sources of raw materials for this method. One is that magnesite, dolomite, serpentine, etc. are treated with acid hydrolysis or other methods to obtain magnesium salts, which are precipitated with alkali to prepare magnesium hydroxide. One is to precipitate magnesium salts obtained from seawater, salt lake water and well brine with alkali to prepare magnesium hydroxide.