Surface modification

Magnesium hydroxide is not conducive to the preparation of composite materials because of its physical surface characteristics. Therefore, improving the physical, chemical and mechanical properties of magnesium hydroxide by surface modification is the current direction of many scholars. 1. Dry modification. Dry modification means that magnesium hydroxide is in a dry state during the modification process. Ye Hong et al. used silane as the research method of dry modification of magnesium hydroxide, and then added it into EVA to make composite material, which obviously improved the dispersion and compatibility of products. Teng Mouyong and others have proved that the modification effect of rare earth coupling agent is the most significant compared with other coupling agents. Li Sanxi et al. have proved that there is adsorption phenomenon in the process of modifying magnesium hydroxide with modifier by dry method. 2. Wet modification. Wet modification refers to dispersing magnesium hydroxide with solvent before modification. Zhou Weiping et al. chose composite modifier to modify magnesium hydroxide by wet method, which proved that magnesium hydroxide modified by wet method is easier to be compatible with polymer. Luo Shiping and others respectively compared the modification effects of sodium dodecyl benzene sulfonate, sodium oleate, sodium undecylenate and sodium stearate on Mg(OH)2. The results showed that the modification effect of sodium undecylenate was better. Anjing et al. modified with sodium stearate by wet method, and found that the flame retardant property of the composite was obviously improved with proper addition of magnesium hydroxide, accompanied by self-extinguishing. Chen first modified magnesium hydroxide by wet method with sodium oleate. After analyzing the data, it was proved that the particle size of magnesium hydroxide would not change obviously with the modification. 3. Hydrothermal method. Hydrothermal method is a way to change the system environment by heating in water environment. YU et al. were hydrothermally treated with magnesium oxide to prepare porous flaky magnesium hydroxide. Zheng Xiaogang et al. added compound modifier and magnesium chloride into the reaction system, and added some small steel balls in the water bath, thus obtaining the modified ultrafine Mg(OH)2. The method has mild conditions and is a new preparation idea. Zhao Zhuoya and others successfully changed their appearance into hexagonal flake by hydrothermal treatment of magnesium hydroxide. After purification, the magnesium hydroxide in Li Jinping hydrothermal treatment industry has a rod-like or flake-like morphology, and the product purity can reach 91% under the optimized conditions. Hydrothermal modification has a good effect, and it is a good method to reduce energy consumption. 4. Microencapsulation coating method. The zinc hydroxystannate prepared by Liu Jianzhou and others by homogeneous precipitation method was successfully coated on the surface of magnesium hydroxide, and the flame retardancy of the material prepared by adding it to polymer was improved. Chen Xu successfully modified magnesium hydroxide with melamine resin as modifier, and confirmed that the modified magnesium hydroxide can improve the performance of composite flame retardant materials. 5. Surface grafting modification. Zhang Yongzhao and others explored the influence of PMMA coating amount in in-situ graft modification. With the increase of coating amount, the sedimentation rate of magnesium hydroxide showed a downward trend. Hu Yong et al. successfully realized the grafting modification of magnesium hydroxide with polyacrylate, and proved that the dispersion of magnesium hydroxide and LDPE composites was significantly improved after modification. At present, the modification technology of magnesium hydroxide is still in full bloom, and it is still a hot spot in the industry to seek a better and more effective modification method.