Magnesium oxide 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.
As an inorganic flame retardant, magnesium oxide has the following excellent properties:
1. It has a very good smoke suppression effect and its smoke elimination ability is excellent. in aluminum hydroxide. Experiments show that when the addition amount of magnesium hydroxide reaches 9%, it has obvious smoke suppression effect, and its maximum relative smoke density drops from 2556 to 375.
2. It does not produce harmful gases, does not affect the electrical insulation of the resin, and is a green product. Its non-toxicity is reflected in preparation, use and waste disposal. There is no emission of harmful substances during the preparation process, and the main raw material can be the salt-making mother liquor or its product, carnallite, to realize the comprehensive utilization of the salt-making mother liquor, and at the same time promote the comprehensive utilization of marine resources and solve the zero-emission problem of sun-salted bitter brine. , so that the pollution problem can be completely solved. The decomposition product of magnesium hydroxide flame retardant is magnesium oxide, which itself is non-toxic and can also neutralize acidic and corrosive gases (such as sulfur dioxide, nitrogen dioxide, carbon dioxide, etc.) produced during the combustion process.
3. The thermal decomposition temperature is 330C, which is 100C higher than that of aluminum hydroxide, allowing plastics added with magnesium hydroxide to withstand higher processing temperatures, which is beneficial to speeding up the extrusion speed and shortening the molding time. At the same time, its decomposition energy (1.37 kJ/g) is higher than that of aluminum hydroxide (1.17 kJ/g), and its heat capacity is also 17% higher, which helps to improve flame retardant efficiency.
4. The particle size is smaller than that of aluminum hydroxide, which causes less wear on equipment and is beneficial to extending the service life of processing equipment.
5. Magnesium hydroxide is a hexagonal crystal or amorphous crystal with small grain size, large specific surface area, strong cohesion between particles and is not easy to disperse. This makes it less dispersible in polymer materials. Adding ordinary magnesium hydroxide to some polymer materials as a flame retardant will greatly affect the mechanical strength and impact resistance of the material.
6. Raw materials are easy to obtain, low cost, and strong market competitiveness.
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