Study On Surface Modification Of Nano-CaCO₃ And Its Mechanism

Nano-CaC03 is a new kind of inorganic filler,widely used in the industries of inks,rubber,plastics,paper,paint,pharmaceutical and so on.But two problems in actual application are really existed:(1)Because of high surface energy,nano-CaC03 particles aggregate easily,which limits the exertion of nanometer effects;(2)The hydrophilic surface makes it very difficult to disperse in the matrix.Therefore,it's of great importance to prepare hydrophobic and dispersive nano-CaC03 by surface modification.In this paper,fatty acids and phosphates were screened to modify nano-CaC03 by wet process,then the process conditions were optimized;in addition,modifying agents were adopted to modify nano-CaC03 in situ,which imitates the mechanism of biomineralization,then the additive amount modifying agents were optimized;finally,the mechanism was briefly discussed.The main research contents and results were as following:1.In the wet modification process,lauric acid and hexadecyl phosphate could effectively improve the hydrophobicity and dispersibility of nano-CaC03.By optimization of the process conditions,nano-CaC03 was prepared with the activation grade of 99.99%,the contact angle of 135.3°,the oil absorption value of 63.94g/100g and the activation grade of 99.99%.the contact angle of 135.8°,the oil absorption value of 68g/100g.2.Nano-CaCO3 was modified in situ.In this process,lauric acid could effectively improve the hydrophobicity and dispersibility of nano-CaC03.The optimal additive amount is 2.5%,under this condition,CaC03 was prepared with the activation grade of 99.99%,the contact angle of 130.9°and the oil absorption value of 70.24g/100g?3.The FT-IR and XRD characterization results showed that,lauric acid and hexadecyl phosphate were adsorbed on the surface of CaC03,the strong chemical bonds were formed between modifying agents and the surface of CaCO3.But the crystal of CaC03 had no change,was calcite.