Hydrothermal Synthesis and Characterization of Hexagonal Mg(OH)2 Flame Retardant with Bischofite and NH3

Abstract

Regular hexagonal plates of magnesium hydroxide with high slurry concentration were prepared by hydrothermal reaction without any organic additive or catalyst using bischofite and ammonia as raw materials. The effects of hydrothermal temperature, stirring speed, hydrothermal duration, and dilution multiple on the preparation of Mg(OH)2 flame retardant were investigated. Scanning electron microscopy, X-ray diffraction, and laser particle analysis were performed to characterize the product morphologies, structures, and size distributions. Results indicated that the growth direction of Mg(OH)2 crystal changed, and the regular hexagonal plates of Mg(OH)2 with uniform particle size and high dispersion characteristic formed after hydrothermal modification treatment. A mass fraction of 15.50% Mg(OH)2 of magnesium hydroxide slurry was obtained by high-concentration (4.30mol/L) magnesium chloride and ammonia as the raw materials.