Inorganic flame retardants are mainly aluminum hydroxide and magnesium hydroxide. The consumption of inorganic flame retardants is the largest. Both aluminum hydroxide and magnesium hydroxide are white powders, the dehydration temperature of aluminum hydroxide is 200°C, and the dehydration temperature of magnesium hydroxide is 340°C. Magnesium hydroxide has a high thermal decomposition temperature, which is 140°C higher than that of aluminum hydroxide, which can make the synthetic material added with magnesium hydroxide withstand higher processing temperature, which is beneficial to speed up extrusion, shorten molding time, and also help Improve flame retardant efficiency. Magnesium hydroxide has a fine particle size and less wear on equipment, which is beneficial to prolong the service life of processing equipment. Since magnesium hydroxide has many advantages compared with aluminum hydroxide, the proportion of magnesium hydroxide is increasing. 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 acid and corrosive gases generated during combustion.
When aluminum hydroxide and magnesium hydroxide are used alone as flame retardants, the dosage is generally 40%-60%, which seriously affects the mechanical properties of the material. Uniform dispersion has become the most important issue in processing engineering. Selecting a surface modifier with excellent performance and modifying the surface of magnesium hydroxide is the primary work before using magnesium hydroxide. The purpose is to increase the surface activity of the particles, improve the dispersion, improve the flame retardant effect, improve the compatibility with polymer materials, and improve the impact resistance and thermal performance.
In non-halogen flame retardants, red phosphorus is a better flame retardant, with the advantages of less addition and wide application. Ordinary red phosphorus is easy to absorb moisture, has poor compatibility with polymer materials, and is particularly prone to spontaneous combustion, so it cannot be used in practice. Microencapsulated red phosphorus flame retardant reduces the activity of red phosphorus and solves the compatibility. The content of red phosphorus is about 85%, but the problem of spontaneous combustion has not been effectively solved, and the dust pollution is serious. Red phosphorus masterbatch is a dark red particle with matrix resin as the carrier, which is compounded with inorganic flame retardants such as aluminum hydroxide and expandable graphite, and the safety problem has been solved. It has low smoke, high flame retardant efficiency; no dust pollution, excellent processing performance; low density, good thermal stability, less decline in physical properties of products; no frost, no migration, no corrosion of molds during processing, especially products with high The leakage trace index (CTI) has obvious advantages in the application of electronic appliances.
The main disadvantage of red phosphorus masterbatch is the color tone. Except for dark red and black, it cannot give more color options to the product. Red phosphorus masterbatch is used for flame retardant of general-purpose plastics, rubber, polyethylene, polypropylene and other materials lacking oxygen elements, preferably compounded with magnesium hydroxide and aluminum hydroxide; used for PET, PC, PBT, PA, etc. Oxygen-rich materials can be used alone for flame retardancy; in the process of processing, in order to achieve the best dispersibility of red phosphorus, a certain amount of dispersant can be compounded.
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