Thermal Decomposition Kinetics And Drying Kinetics Of Magnesium Hydroxide Nanorods

Magnesium hydroxide is one of the widely used inorganic materials in many industrial fields, such as catalysis, medical products, foodstuff, water treating and desulphurization, and also is the precursor in the preparation of magnesium oxide nanorods. Recently, much interest has been attracted into its applications as a flame retardant due to its unique properties, including nontoxic, smoke inhibition, high decomposition temperature and environmentally friendly material. According to reports, magnesium hydroxide nanorods as a new inorganic retardant which can not only reduce the filling amount but also improve the mechanical performance of the polymer materials, have more excellent properties than other nanoscale magnesium hydroxide, such as magnesium hydroxide nano-partacles and magnesium hydroxide nano-sheets. Magnesium hydroxide nanorods with a diameter range of 100-200nm and average length of 6-10μm were synthesized by liquid method using basic magnesium chloride nanorods as precursor and sodium hydroxide as precipitation conversion reagent. TG experiments and drying kinetics experiments of magnesium hydroxide nanorods were made, and TG curves and drying characteristic curves of magnesium hydroxide nanorods were obtained.The research of thermal decomposition kinetics of magnesium hydroxide nanorods is found that the rate-controlling mechanism is random nucleation and its subsequent growth, integral function g(a) is-ln(1-a), apparent activation energy is 261.610kJ/mol.The drying kinetics results indicate that drying medium temperatures and bed-layer thicknesses of the wet material have the same impact rules on the drying curves and drying rate curves of magnesium hydroxide nanorods. When the drying medium temperatures are lower and the bed-layer thicknesses of the wet material are thicker, the drying rate curves of Mg(OH)2 nanorods exhibit three stages of a setup period, a constant rate drying period and a falling rate drying period; and with increasing drying medium temperatures and decreasing bed-layer thicknesses of the wet material, the constant rate drying period ranges become gradually smaller until they disappear, and the drying rate curves of Mg(OH)2 nanorods exhibit only two stages of a setup period and a falling rate drying period. The experimental data of drying kinetics were simulated by means of thermal analysis kinetics method, and the drying differential mechanism function the drying integral mechanism function the drying equation MR=exp[-(kt)2], the drying rate equation as well as the drying rate constant were achieved, The pre-exponential factor A is 10.741min-1, the activation energy of interface evaporation Ev is 10.671kJ/mol, and the experimental constant cL is 100.000m-1. The experimental data of drying kinetics were simulated by means of the thin layer-drying models, and the drying equation and the drying rate equation are derived. The drying time index n is 1.551, the pre-exponential factor A is 10.905min-1, the activation energy of interface evaporation Ev is 10.527kJ/mol and empirical factor cL is 104.434m-1.