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Electric charge is the key to the "aggregation and dispersion" of nanometer calcium carbonate

Electric charge is the key to the "aggregation and dispersion" of nanometer calcium carbonate

Nanometer calcium carbonate is a kind of functional filling material, widely used in rubber, plastic, papermaking, adhesives and other industries, not only can play a filling role, reduce costs, but also have the role of semi-reinforcing or reinforcing, and give the matrix some special function.



If there is one of the biggest obstacles limiting the use of nano-calcium carbonate, it should be "agglomeration". As for the "reunion", I don't think it's the Mid-Autumn Festival...



1 nanometer calcium carbonate "gather and disperse" mystery



When the particle size decreases to a certain extent, the number of atoms occupied by the surface of the particle will be significantly increased compared with the product of the large particle, and the surface charge of the particle is not balanced, so that the surface of the particle can rise rapidly. Nano-sized calcium carbonate particles have small particle size and high surface energy, which seriously tend to coalesce to reduce their surface energy and form secondary particles, resulting in the instability and easy aggregation of nano-sized calcium carbonate.



At present, it is commonly used to improve the dispersion of nanometer calcium carbonate by modification technology. In principle, by surface modification, the modifier can be orientated on the surface of calcium carbonate, so that the surface has charge characteristics. Due to the repulsion of the same charge, calcium carbonate is not easy to agglomerate, so as to achieve good dispersion in the matrix.



Summary: Charge is the key to the aggregation and dispersion of nanometer calcium carbonate.



2 Control the surface potential to prepare nano-sized calcium carbonate



Recently, the editor of Powder.com found that Zhejiang University had publicized a preparation method of nano-sized calcium carbonate based on surface potential control, in which the key is charge balance.



It IS SHOWN THAT CARBONIZATION OF CALCIUM CARBONATE WILL CONSUME CALCIUM IONS IN SLURRY, RESULTING IN SURFACE POTENTIAL REDUCTION, SYSTEM INSTABILITY AND AGGLOMERATION. The technique stabilizes the system by introducing additional calcium ions (such as calcium chloride) to immediately replenish the consumed calcium ions. The characteristic is that salt solution containing calcium ions is added to the saturated calcium hydroxide system after treatment to control the surface potential, and carbon dioxide is injected into the water bath reaction to produce nano-calcium carbonate.
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