At present, the requirements for flame retardant properties of flame retardant materials are getting higher and higher

2022-08-19 15:41:01

Magnesium hydroxide is a kind of inorganic flame retardant and smoke suppressant with high filling amount and additive. The flame retardant mechanism is as follows: when magnesium hydroxide is heated at 340-490 ℃, it decomposes and absorbs the heat on the surface of the combustor to achieve the flame retardant effect; At the same time, a large amount of water is released to dilute the oxygen on the surface of the combustibles, and the decomposed active magnesium oxide will adhere to the surface of the combustibles, further preventing the combustion. In the whole flame retardant process, magnesium hydroxide does not produce any harmful substances, and the decomposed products can absorb a large amount of harmful gases and smoke generated by the combustion of plastics, rubber and other polymers while being flame retardant. Active magnesium oxide continuously absorbs the melting residue of incomplete combustion, and at the same time, it can quickly prevent combustion, eliminate smoke and prevent molten droplets. It is a new environmental friendly inorganic flame retardant.

Active magnesium hydroxide flame retardant does not contain halogen elements such as bromine (BR) and chlorine (CL), and has good flame retardancy and smoke suppression. It is an ideal low smoke halogen-free filled flame retardant for polymer materials such as plastics and rubber. As the decomposition temperature of magnesium hydroxide reaches 340 ℃, it is very suitable for PP, PE, ABS, EVA and other products with high molding temperature. It is widely used in flame retardant insulation materials and sheath materials of wires and cables, fire-proof fillers, injection molding color masterbatch, etc.

The hydrothermal treatment of magnesium hydroxide is a method in which water is used as a solvent to carry out a chemical reaction at a certain pressure and time between the boiling point of water and the supercritical temperature. In high-temperature and high-pressure aqueous solution, the intensification of molecular motion will lead to the acceleration of reaction speed, improve the solubility of magnesium hydroxide solid synthesized under normal temperature and pressure, and realize some reactions that are difficult to be carried out under normal temperature and pressure.

By controlling the pressure and temperature of hydrothermal reaction, the size, morphology, nucleation and growth rate of magnesium hydroxide particles are controlled. The higher the temperature, the faster the diffusion rate of ions, and the dissolution of small crystals. Ions will be accelerated in the process of migration and deposition to large crystals, accelerating the growth rate of crystals and contributing to the formation of crystal products with large particle size and low water content. At the same time, the specific surface area of magnesium hydroxide has a great relationship with the pressure. The higher the pressure, the smaller the specific surface area of magnesium hydroxide. Therefore, under certain pressure and temperature conditions, an appropriate specific surface area can be obtained.

Although the development of crystalline flame-retardant magnesium hydroxide is still in the initial stage in China, it can be found by scanning electron microscope that the particles of magnesium hydroxide after hydrothermal reaction are regular flakes, the average particle size is increased, and it has good dispersibility. It can be used as a flame retardant additive for organic polymers.

As the application of high molecular polymer materials is more and more extensive, the requirements for flame retardant properties of flame retardant materials are also higher and higher. Inorganic flame retardant magnesium hydroxide has been paid more and more attention because of its multi flame retardant, non-toxic and low smoke characteristics. However, magnesium hydroxide synthesized under normal temperature and pressure generally presents irregular structure, large specific surface area, wide particle size distribution and strong agglomeration among particles, which not only limits the dispersion of magnesium hydroxide in polymer, but also has poor compatibility and is not suitable for use as flame retardant material.