Application of different fillers in powder coatings
The filler in the coating can not only reduce its cost, but also play a great role in improving the performance of the coating product. Such as improving the wear resistance of the coating film, reducing the sagging of the coating during melting and leveling, improving the corrosion resistance, and improving the moisture resistance.
When selecting fillers for powder coatings, factors such as density, dispersion performance, particle size distribution, purity and other factors need to be considered. Generally speaking, the higher the density, the lower the coverage of the powder coating; the dispersibility of large particles is better than that of small particles; the filler is chemically inert and can avoid reaction with certain components of the powder formulation such as pigments; The color of the filler should be as white as possible. The powder materials commonly used in powder coatings mainly include calcium carbonate, barium sulfate, talc, mica powder, kaolin, silica, wollastonite, etc.
1. Application of calcium carbonate in powder coatings
Calcium carbonate is divided into light calcium carbonate (precipitated calcium carbonate) and heavy calcium carbonate. No matter what kind of calcium carbonate is produced and what method is used, different particle sizes strongly affect the gloss of the coating. Calcium carbonate is generally not recommended for outdoor use.
In addition to being used for increments, heavy calcium is mainly used to partially replace titanium dioxide and color pigments, replace light calcium and precipitated barium sulfate, prevent corrosion and partially replace anti-rust pigments.
When heavy calcium is used in interior architectural paint, it can be used alone or in combination with talc. Compared with talcum powder, calcium carbonate can reduce the pulverization rate, improve the color retention of light-colored paints and increase the resistance to mold. However, due to poor acid resistance, it hinders its application in exterior coatings.
Compared with heavy calcium, light calcium has a small particle size and narrow particle size distribution range, high oil absorption and brightness. Light calcium can be used where the greatest matting effect is required.
2. Application of barium sulfate in powder coatings
There are two types of barium sulfate used as paint extender pigment: natural and synthetic. The natural product is called barite powder, and the synthetic product is called precipitated barium sulfate.
In powder coatings, precipitated barium sulfate can enhance the leveling and gloss retention of powder coatings, and has better compatibility with all pigments. The powder coating can reach the ideal coating film thickness in the spraying process, and the powder coating rate is high.
Barite powder filler is mainly used in industrial primers and automotive intermediate coatings that require high film strength, high filling power and high chemical inertness, and also used in topcoats that require higher gloss. In latex paint, due to the high refractive index of barite (1.637), fine barite powder can have the function of translucent white pigment and can replace part of titanium dioxide in paint.
3. Application of mica powder in powder coating
Mica powder is a complex silicate composition, with scaly particles, excellent heat resistance, acid and alkali resistance, and has an impact on the melt fluidity of powder coatings. It is generally used in temperature resistant and insulating powder coatings and can be used as texture powder For packing.