BYK-405 is used as a wetting and dispersing agent to facilitate the incorporation of fumed silica into coating systems. The thixotropic properties of fumed silica are increased and stabilized with BYK-405.
The increase in rheological efficiency is significantly higher in varnishes than in color systems at the same shear.
The additive reduces and prevents precipitation of fumed silica from the coating.
BYK-405 is most suitable for solvent-borne coating systems based on polyesters, acrylics and alkyds containing fumed silica. The fumed silica must be at least partially hydrophilic. If BYK-405 is added later, the base material will have better thixotropy and the thixotropic resin system will exhibit better thixotropy.
The thickness of the adsorption layer is related to the adsorption morphology. The tail-shaped stretched links are better than the ring-shaped ones, and the large ring-shaped ones are better than the small ring-shaped ones.
Thicker adsorption layer is better, but it is also limited. Too long is easy to twist, hs code pe wax relatively thin, and it is easy to be entangled with other chain links, causing flocculation, and desorption caused by external force (stirring), so it is not The thicker the better. Generally speaking, for a particle of 0.1~1μm, it is better to have a steric shielding layer with a thickness of not less than 5~20nm.
For example, pigment particles are dispersed in alkyd resin. The average molecular weight of the alkyd resin is 2500. When the particle size of the pigment is lum, the relationship between the thickness of the adsorption layer and the particle size is: pigment particle size 1pm10m (10000A)
200:1 alkyd resin (average relative molecular weight) 5×10-m (about 50A)
If the pigment particle size is pulverized to 0.1 μm, the ratio is 20:1, the particle size becomes smaller, the attraction force is weakened, and the adsorption layer becomes thicker. Entropy repulsion increases and stability improves. There are many research reports on the thickness of the adsorption layer. For example, TiO, and copper phthalocyanine are dispersed in alkyd resin solution, the thickness of the adsorption layer is (1~2)×10-8m (100~200A); lead chromate is dispersed in butyl acetate of alkyd nitrocellulose In the solution, the thickness of the adsorption layer is 4×10~*m (400A); TiO, dispersed in a benzene solution of polymethyl acrylate with a molecular weight of 8400, the thickness of the adsorption layer is 4.38×10-10m (438A); if it is reduced When the relative molecular mass of the resin is 2600, the thickness of the adsorption layer will also decrease, becoming 1.05×10-m (105A). It is not difficult to see that the thickness of the adsorption layer is determined by the properties of the solvent, resin, and pigment. of.
The fastness of the adsorption layer The fastness of the adsorption layer is determined by the properties of the pigment surface and the structure and characteristics of the dispersant.
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