Due to the strong polarity of magnesium hydroxide, the surface of the particles is positively charged, which is easy to form secondary agglomerations, and its hydrophilicity makes the dried product still contain water. Adding directly to the polymer is not conducive to dispersion in the polymer material, and it is easy to produce gaps with the polymer interface, and the compatibility is poor. In order to increase the surface activity of the particles, thereby improving the dispersibility of the powder, improving the compatibility with polymer materials, and improving the flame retardancy of magnesium hydroxide, it needs to be modified.
Coupling agent modification.
The commonly used surface modifier of magnesium hydroxide flame retardant is a coupling agent. The coupling agent is a kind of substance with an amphoteric structure. Part of the groups in their molecules have an affinity with organic polymers, and the other part has an affinity with magnesium hydroxide. These affinities are provided by intermolecular forces and chemical bonds. In the production and processing of polymer materials, the hydrophilic magnesium hydroxide is difficult to be compatible with the polymer, and the bridging effect of the coupling agent can make them tightly united.
Commonly used coupling agents mainly include silanes, titanates, chromium, zirconium compounds, higher fatty acids, alcohols, and esters.
Mechanism of coupling agent: The silane coupling agent is a kind of low-molecular-weight organosilicon compound with a special structure. It has a prominent effect on improving the strength and heat resistance of polymer materials. Therefore, different polymers need to choose different coupling agents to encapsulate magnesium hydroxide.
Anionic surfactant modification
Anionic surfactants are mainly higher fatty acids and their derivatives. On the one hand, they contain hydrophilic groups that can interact with the hydrocarbon groups on the surface of magnesium hydroxide. Multiple hydrophilic groups are linked to the surface of magnesium hydroxide to improve the fastness of adsorption; On the other hand, high molecular polymers are long-chain molecules, and their high molecular chains can play a steric hindrance, reduce the agglomeration of magnesium hydroxide, and form particles with smaller particle size. Compatible with organic resin matrix, long time use, not easy to desorb.