The flame retardant mechanism of magnesium hydroxide as flame retardant is: when magnesium hydroxide is decomposed by heat, it releases water and absorbs a large amount of latent heat at the same time, which reduces the actual temperature that the resin bears in the flame and has the cooling effect of inhibiting the decomposition of polymer and the generation of flammable gas. The magnesium oxide generated after decomposition is a good refractory material, which can also help improve the resin\’s ability to resist the flame, and the thermal decomposition temperature of magnesium hydroxide is as high as 340℃, so its flame retardant performance is very superior. However, the main drawback of common magnesium hydroxide for polymer flame retardant is the low flame retardant efficiency as well as the poor compatibility with the substrate, to make the flame retardant performance of the material to meet certain requirements, the addition of magnesium hydroxide is usually up to 50% or more, which will have a great impact on the mechanical properties and processing properties of the material, it is difficult to meet the use requirements. In order to make magnesium hydroxide can be better used for plastic flame retardant, many research institutions at home and abroad have successfully developed different properties of magnesium hydroxide.
The United States company developed a good dispersion, processing temperature up to 332 ℃ of high-quality magnesium hydroxide. Japan started to research special large grain, low specific surface area of magnesium hydroxide since 1973, and the research was successful in 1975. The institution has recently developed magnesium hydroxide flake particles and fibrous crystals, but the technology is not publicly available. Dalian University of Technology has also developed a new type of magnesium hydroxide with large grain size, small specific surface area and excellent flame retardant properties. Jiangsu Institute of Comprehensive Utilization of Seawater, Lanzhou Company Research Institute and the Chinese Academy of Sciences Qinghai Salt Lake Research Institute have been committed to the development of special crystalline magnesium hydroxide flame retardant.
The application research of Hebei Messi Biology Co., Ltd. shows that when the particle size of added magnesium hydroxide is reduced to 1µm, the oxygen index of its flame retardant polymer system is significantly increased. Many literature reported that with the reduction of particle size, the inorganic particles have enhanced toughening effect on polymer materials. Therefore, ultrafineralization has become an important development direction for magnesium hydroxide flame retardants. Inside materials science, people call ultrafine microparticles as nanoparticles, which is a kind of sub-stable intermediate state material between solid and molecule.
Nanometer magnesium hydroxide refers to the particle size between 1 ~ 100nm magnesium hydroxide, as a nano-material, it has the common characteristics of nano-materials, namely small size effect, quantum size effect, surface effect, macroscopic quantum effect, etc., with it filled in the composite material can greatly improve the flame retardant properties, mechanical properties and other properties of the material. Ltd. has shown that the flame retardant properties of plastics with nano magnesium hydroxide are better than those of ordinary magnesium hydroxide filled plastics, with better machinability, compared with organic flame retardants containing phosphorus and halogens, nano magnesium hydroxide is non-toxic, tasteless, and has a triple function of flame retardant, filling, smoke suppression, is the ideal additive for the development of flame retardant polymers, has received wide attention.
Messi Biology studied the flame retardant properties, flowability and mechanical properties of nano-magnesium hydroxide and micron magnesium hydroxide filled polypropylene (PP) system. The experimental results show that the flame retardant performance of the nano-magnesium hydroxide filled system is better than that of the micron magnesium hydroxide filled system when the same mass fraction of magnesium hydroxide is added, and it reaches the V-0 level when the filling amount is 60%, and the smoke emission is less, and the flowability and mechanical properties are also better than that of the micron magnesium hydroxide filled system.