With the continuous development progress of the economy, the application of polymer materials is becoming more more extensive. In recent years, fire accidents caused by polymers have attracted great attention all walks of life, the research development of flame retardant polymers has become a hot spot. At present, the use of organic flame retardants on the market, such as large smoke, toxic smoke other hazards, has been restricted by laws in Europe, the United States, Japan my country. Therefore, inorganic flame retardants have received great attention. Magnesium hydroxide flame retardant has a high decomposition temperature (340 ℃~450 ℃), the thermal decomposition products are MgO H2O, it does release any toxic harmful substances, does cause any harm to the environment human health. Therefore, magnesium hydroxide flame retardant is At present, one of the most concerned inorganic flame retardants has broad application prospects.

At present, the magnesium hydroxide flame retardants produced on the market are basically in the micron level (d>5 μm), with a wide particle size distribution, a large amount of filling is required in the application; the magnesium hydroxide products prepared in addition are easy to agglomerate have strong hydrophobicity 2. Incompatible with high molecular polymers. In practical applications, magnesium hydroxide has caused severe damage to the mechanical properties of high molecular polymer materials, which greatly limits the application of magnesium hydroxide flame retardants. Through certain physical chemical methods, it has low surface polarity strong hydrophilicity. The magnesium hydroxide flame retardant with small particle size, narrow distribution good compatibility with macromolecule polymers has become a hotspot of current scientific research.

On the one hand, the use of organic functional groups to modify the surface of magnesium hydroxide can reduce the polarity of the surface of magnesium hydroxide improve its compatibility with high-molecular polymers; the micro-nano-scale ultra-fine magnesium hydroxide has a low loading is prepared using it The composite material has good performance. On the other hand, the flame retardant performance of micro-nano-magnesium hydroxide of the same quality is several times higher than that of micro-magnesium hydroxide, the effect on polymer polymer materials is also low. The micro-nano magnesium hydroxide with low polarity can be evenly dispersed in the polymer material, so that the flame retardant performance mechanical performance of the entire material are kept consistent. Therefore, the surface modification ultra-fineness of the magnesium hydroxide flame retardant can solve the shortcomings in the application of magnesium hydroxide flame retardant.

Domestic foreign scientists technicians have mainly carried out the following three aspects of the modification of magnesium hydroxide: (1) Research on the surface modification of magnesium hydroxide by organic compounds to reduce the polarity of magnesium hydroxide surface reduce hydrogen The hydrophobicity of magnesium oxide solves the problem of incompatibility with high-molecular polymers; (2) The research on the preparation of ultrafine magnesium hydroxide modified to solve the shortcomings of magnesium hydroxide, such as easy agglomeration, poor dispersion, large filling amount; ( 3) Analysis research on the mechanism of additives on the formation of ultra-fine magnesium hydroxide.

Application requirements of magnesium hydroxide flame retardant materials

Magnesium hydroxide as a flame retardant has the following requirements:

(1) Must have extremely high purity (Mg(OH)2>93%), high purity magnesium hydroxide only has high flame retardant performance, but also can reduce the amount of its addition in the material;

(2) The particle size is small, the composite materials prepared with micro-nano-magnesium hydroxide are far superior to micron-level magnesium hydroxide in all aspects (including flame retardant effect, smoke suppression mechanical properties, etc.);

(3) The surface polarity is low. When the surface polarity of magnesium hydroxide is reduced, the degree of agglomeration will be reduced, the dispersibility compatibility will increase. Adding it to the polymer as a flame retardant material will have better compatibility with the polymer. To reduce the impact on the mechanical properties of the material.

Reasons for modification of magnesium hydroxide flame retardant materials

At present, the particle size of magnesium hydroxide produced in the market is relatively large, some products have a particle size of up to tens of microns, which is directly added as a flame retardant. The dispersibility is poor, which has a great influence on the mechanical properties of the material. Industry usually uses physical methods to grind to reduce the particle size to a few microns. Magnesium hydroxide prepared by physical methods has a high polarity surface is easy to agglomerate. It is compatible with the polymer matrix as a flame retardant material, which only reduces its resistance Flammability, caused serious damage to the mechanical properties of the material. Compared with organic flame retardants, inorganic flame retardants are filled in a larger amount, resulting in reduced efficiency of inorganic flame retardants. In order to achieve better flame retardant effect of magnesium hydroxide flame retardant in practical applications, it must be used in a large amount in the polymer matrix, a large amount of magnesium hydroxide will reduce the mechanical properties of the composite material. The preparation of industrial-grade magnesium hydroxide into micro-nano scale ordered micro-structured magnesium hydroxide can greatly reduce the amount of magnesium hydroxide added in the polymer matrix. The anion cation vacancies exposed on the surface of the micro-nano scale magnesium hydroxide material Many, strong polarity, high surface free energy, easy to agglomerate, poor dispersion, as a flame retardant material is difficult to be well compatible with the polymer matrix. Using the functionality of specific compounds can make the "free" sites regions on the surface of the material have different structures. At the same time, these regions are used as attachment points for modifying molecules metal atoms. This has a wide range of applications in the field of materials. By using specific compounds to modify the surface of magnesium hydroxide, the shortcomings of high surface free energy, strong polarity easy agglomeration can be solved. The modified magnesium hydroxide has excellent compatibility with the polymer matrix, so The preparation of surface modification ultra-fine refinement of magnesium hydroxide has attracted wide attention domestic foreign scientists.

Magnesium hydroxide as a flame retardant for high molecular polymers, the most important thing is to be well compatible with high molecular polymers, to achieve uniform dispersion, ultimately achieve the purpose of flame retardant. Using specific compounds to modify the surface of magnesium hydroxide can reduce the surface polarity of magnesium hydroxide, make its surface hydrophobic, improve the compatibility of magnesium hydroxide with polymers. The chemical modification of the surface of magnesium hydroxide is to use chemical methods to selectively adsorb specifically adsorb the functional groups in the organic molecules the inorganic gel molecules on the surface of the magnesium hydroxide powder, to chemically react to coat the surface of the particles so that The surface of the particles is organicized the polarity is changed, finally the surface is modified. Commonly used surface modifiers are mainly coupling agent silane coupling agent titanate, aluminate coupling agent higher fatty acids their derivatives. The modification of magnesium hydroxide can also achieve other functions, such as changing the particle morphology of magnesium hydroxide expanding its application range.