Study On The Preparation, Modification And Application Of Calcium Carbonate With Different Morphologies

In this dissertation, nano-calcium carbonate (NCC) with square, rod-like andneedle-like morphology was synthesized by carbonization method. The structure andmorphology of calcium carbonate were characterized by TEM, SEM and XRD. Theresults showed that three kinds of morphologies of calcium carbonate were all calcitewith monocrystalline, mixed crystalline and polycrystalline structure respectively. Theoil-absorption value of them could reach43.63mL/100g,44.58mL/100g, and46.02mL/100g respectively, which can reach the national standard on the industrialcalcium carbonate product. Taking the morphology as main index, the synthesisconditions were optimized as follow. Square NCC: carbonization temperature50oC,stirring speed800r/min, crystal controlling agent1.5%(m/m), calcium hydroxidesuspension concentration7%(m/v), carbon dioxide flow rate60mL/min. Rod-like NCC:carbonization temperature60oC, stirring speed600r/min, crystal controlling agent1.5%(m/m), calcium hydroxide suspension concentration7%(m/v), carbon dioxide flowrate60mL/min；Needle-like NCC: carbonization temperature60oC, stirring speed400r/min, crystal controlling agent1.5%(m/m), calcium hydroxide suspensionconcentration8%(m/v), carbon dioxide flow rate60mL/min. Taking oil-absorptionvalue as main index, the modification conditions of nano-calcium carbonate wereinvestigated via single-factor and orthogonal experiments, using sodium dodecylbenzene sulfonate (SDBS) as modifier. The optimized modification conditions resultwere as follow: the modifier dosage3.5%, the modification temperature70℃,and themodification time55min. The modified need-like NCC was added to polypropylene toprepare the polypropylene/calcium carbonate composite and then the influence of thecalcium carbonate content on the mechanical properties of the obtained composite wasstudied. The results showed that when6%(m/m) calcium carbonate was added, thetensile strength, flexural strength and impact strength of polypropylene/calciumcarbonate composites can increase by11.53%,44.28%and20.63%respectively.