Study On The Preparation And Dispersion Of The Monodisperse Magnesium Sulfate Whisker

Magnesium sulfate whisker is a kind of prospective inorganic flame-retardant andreinforcing materials. But its application has been limited for the serious aggregationduring the preparation. In this thesis, monodispersed magnesium sulfate whisker wasprepared taking magensite as raw material by means of calcination and hydrothermalsynthesis, of which surface energy was decreased by the addition of polyacrylamide.The dispersity and slenderness ratio of magnesium sulfate whisker were researched.Through continuous optimization of preparation parameters, the optimal preparationconditions were obtained by the single-factor method studied on the concentration ofreactant, hydrothermal times and temperature, agitation intensity, mole ratios ofH₂SO₄/MgO and additive. The SEM, EDS and FT-IR were used to analyze the surfacemorphology, elemental composition and functional groups of whisker surface,respectively. The phase analysis and thermal stability of the product were detected byXRD and TG-DSC. The dispersion of whisker was characterized by the percentage ofsingle whisker in a certain amount of total content.The magnesium sulfate whisker was prepared by the method of hydrothermalsynthesis with the magnesium oxide being obtained by taking magnesite as raw material,which was calcinated at750℃for3.5h. The optimal preparation conditions ofmagnesium sulfate whisker were that, the stirring speed for600r/min, the reactiontemperature for180℃, the reaction time for4h, the mole ratio of H₂SO₄/MgO for1:4,the reactant concentration for1%, the content of polyacrylamide for10%of magnesiumoxide and the detected sample for being sieved, air pump filtration, ethanol immersionand oscillator dispersion.The product prepared at the optimal conditions had good dispersivity with diameterless than500nm, average length of50μm, the ratio of length to diameter more than100, the content of single whisker90%and the composition of the magnesium sulfatewhisker. TG-DSC curves showed that, there were two endothermic peaks at270³80℃and395⁶33℃. The magnesium sulfate whisker, which did not decompose until270℃with good thermal stability, was a good kind of flame-retardant materials. FT-IR results showed agglomeration behavior was decreased after the addition ofpolyacrylamide for the reducing of surface energy and dissociating hydroxyl groups.The achievements above had a certain guiding significance for the large-scaleproduction of magnesium sulfate whisker, which had a certain reference value for thestudy on the dispersion of inorganic whisker.