Modified magnesium hydroxide nanoparticles with 98% yield were synthesized by an easy-to-industrialize liquid-phase precipitation method with the synergistic effect of sodium dodecyl sulfate (SDS) and sodium polyacrylate (PA-Na) compound modifiers. The optimum amount of modifier was determined by the settling volume experiment to be 0.2% (mass fraction of the compound modifier to the synthesized sample), and the optimum mass ratio of SDS to PA-Na was 1:1.
The samples before and after modification were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption and apparent density analysis, and the results showed that the modified samples had good dispersion and high crystallinity. Infrared spectroscopy and sedimentation volume experiments showed that the method can make the modifier adsorbed on the surface of magnesium hydroxide particles, which changed the surface of magnesium hydroxide from hydrophilic to lipophilic, and improved the dispersion stability of magnesium hydroxide in organic media. It was found that SDS and PA-Na might be adsorbed onto the sample surface in the form of unilamellar or bilamellar layer, and mainly rely on the spatial site resistance effect of long carbon chains and the electrostatic stabilization effect of dissociation to generate a large number of charges to influence the agglomeration of nucleated particles, so as to obtain the flake sample with excellent dispersion.
The modified nano-magnesium hydroxide was synthesized by direct precipitation method using magnesium nitrate hexahydrate, sodium hydroxide as raw material and sodium fatty alcohol ethoxylate carboxylate as modifier, and the optimum amount of modifier was determined by sedimentation volume experiment as 0.2% of the mass of magnesium hydroxide. The results show that the method can be used to characterize the samples before and after modification. The results showed that the method can make the modifier adsorbed on the surface of magnesium hydroxide particles and change the surface of magnesium hydroxide from hydrophilic to lipophilic.