Preparation of magnesium hydroxide
Preparation of magnesium hydroxide:
General requirements:
① The crystal shape is fibrous, which can increase the elongation and flexural strength of the material.
② The purity must be high. The higher the purity, the better the flame retardant effect.
③ The smaller the particles, the better. Experiments have shown that when nano magnesium hydroxide is filled into the material as a flame retardant, all aspects of performance, including flame retardant effect, smoke elimination and mechanical properties are superior to micron magnesium hydroxide.
④ Low surface polarity. Ordinary magnesium hydroxide affects the mechanical properties of the material when it is filled into the material as a flame retardant due to its high surface polarity and large microscopic internal stress. When the surface polarity is low, the aggregation of particles decreases, the dispersion and compatibility in the material increase, and the impact on the mechanical properties of the material is reduced. Therefore, it is necessary to use appropriate surfactants and dosages for surface treatment to improve compatibility with polymers.
⑤ The specific surface area is less than 20m2/g, the distortion value in the (101) orientation is less than 3.0×0.001, and the crystal size in the (101) orientation is greater than 80nm. Only magnesium hydroxide with the above characteristics can be well compatible with the material.
Surface modification of magnesium hydroxide The surface treatment of magnesium hydroxide can be carried out by chemical reaction between surfactant and the surface of magnesium hydroxide particles, and surfactant can also be used to coat the surface of magnesium hydroxide particles. Both of them change the surface state of particles, so that the particles have new properties, better compatibility with materials, and prevent the reduction of mechanical properties of materials. Commonly used magnesium hydroxide surface modifiers are coupling agents, sodium stearate, sodium oleate and titanate, etc., with an amount of 1% to 3%.
