As a matting agent for coating applications, it has the following advantages
1, Storage stability (anti-precipitation): As one of the countermeasures to prevent precipitation in coatings, WAX-treated silica can perform very well.
2, Chemical resistance: Compared with untreated silica, GE/GK series shows very good chemical resistance. We recommend SS series for higher quality requirements.
3, Sliding performance (coefficient of friction): Silica with M-type coating has better sliding performance (low coefficient of friction). Untreated silica < F type < M type has better sliding performance in that order. Wet silica is used in various industries and fields, in addition to its porous nature and large specific surface area.
In the dispersion system, the particle size distribution is not uniform, the particles are somewhat soluble, and Ostwald ripening occurs during storage. In a fine particle dispersion system, the solubility of large particles is lower than that of small particles due to different particle diameters. Therefore, wax additive sanding aid the molecules eluted from small particles precipitate out and diffuse around the large particles. Due to the Austenite maturation, the small particles gradually disappear and the large particles continue. As it grows, the stability of the dispersion system deteriorates.
Using the interface charge and the adsorption layer between the particles can overcome the van der Waals gravitational force between the particles, prevent and slow down agglomeration, and stabilize the dispersion system. Its principle of action is basically the same in water systems and non-aqueous systems.
1. The generation of electric charge
The formation of the charge at the particle interface, the sign of the charge, and the amount of charge are related to the nature of the dispersion medium and the pH value.
Kitahara Yuan proposed b. In an aqueous dispersion medium, there are two main reasons for the generation of interface charges.
(1) Potential-determining the charge at the ion interface is determined by the potential in the solution, called potential-determining ions, such as oxygen ions (H+) and hydroxide ions (OH-) of oxide particles. The ions formed in the ionic crystalline particles (such as Ba+ and SO of barium sulfate) are called potential-determining ions. When the oxide particles are in the dispersion liquid, when the pH value is low, the hydroxyl groups on the particle surface (oxide and water contact, Due to hydration, a hydroxyl group will inevitably be generated on the interface) and it will be added to the protons that tend to it, and it will be positively charged.
When the pH is high, protons are given from the hydroxyl group, which is negatively charged. At a certain pH value, the apparent charge of the particle becomes zero, which is the isoelectric point. The acidity and alkalinity of the oxide are different, and the isoelectric point is also different. Even if it is the same oxide, the isoelectric point is different due to different manufacturing and other conditions.
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