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Surface modification of Nano Calcium Carbonate

Surface modification of Nano Calcium Carbonate

Compared with the ordinary micron-scale calcium carbonate, nano calcium carbonate has a high surface energy, the surface hydrophilic oleophobic, easy to gather into the group characteristics, it is difficult in non-polar or weak polarity of the rubber / resin in the uniform dispersion, with the nano calcium carbonate filling increased, these shortcomings more obvious, excessive filling and even make the product can not be used. In order to reduce the high potential energy of nano calcium carbonate surface, improve the dispersion, and enhance its wetting and affinity with the polymer, usually make surface modification before use. 

At present, nano calcium carbonate surface modification is mainly modified by the modifier. Modifiers according to their structure and characteristics can be divided into surfactants, coupling agents, polymers and inorganic. There are many kinds of surfactants, large production capacity, low price, the effect of improving the compound is better than a single type of surfactant, the current application of more surfactants are fatty acids (salts), polymer compounds and phosphate (salt). A part of the molecule of the coupling agent can react with various functional groups on the surface of the mineral to form a strong chemical bond, and the other part may react chemically or physically entangle with the organic polymer material, thereby separating the mineral and the organism A large amount of material firmly combined, the current coupling agent for nano calcium carbonate mainly titanate coupling agent and aluminate coupling agent. The polymer can be adsorbed on the surface of calcium carbonate, sothat the calcium carbonate has the charge characteristics, and the formation of physical and chemical adsorption layer on its surface, to prevent the agglomeration of calcium carbonate particles agglomeration, improve the dispersion. Polymer modified nano-calcium carbonate in two cases: one is the monomer adsorption on the surface of nano calcium carbonate, by initiating polymerization in the surface grafting polymer chain; the other is the direct adsorption of polymer on the surface of nano calcium carbonate modification. Inorganic surface modification on the one hand can improve the dispersion of nano calcium carbonate, on the other hand can improve the acidity of nano calcium carbonate to expand its use. This type of organic matter has condensed phosphoric acid, sodium aluminate, sodium silicate, alum, etc. Although the existing modifier to a certain extent, improve the performance of nano calcium carbonate, but in the process of nano calcium carbonate drying secondary particles also exist in the phenomenon, a direct impact on product performance. 

High-energy surface treatment is a nano calcium carbonate surface modification technology, including surface irradiation modification and plasma surface modification. Surface irradiation modification method is in the high energy irradiation, the monomer in the nano calcium carbonate surface free polymerization, the formation of a layer of organic film or polymer film, thereby improving the filler surface and the compatibility of polymer materials. Plasma surface modification is the use of glow discharge and other plasma systems, the use of plasma treatment of gas, through the reaction in the nano-calcium carbonate surface to form an organic coating to modify. 

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