Fillers of coatings (paintwork materials)
Fillers of paints and varnishes are highly dispersed substances of inorganic origin, which are introduced into opaque paints and varnishes. Like pigments they are not soluble in varnishes, water, lacquers and other dispersion media. As opposite to pigments, fillers are characterized by low refraction index: from 1,4 to 1,75. Most of the filler materials are white or slightly colored.
The purpose of incorporating fillers into a paint material is twofold:
- giving special properties to the paintwork material itself and to the finished coating;
- cheapening (decreasing the prime cost) of the paintwork material by means of replacing the expensive pigment with cheaper fillers.
In combination with organic film-forming substances fillers cannot produce opaque coatings. This is due to their low refractive index. In such cases fillers are used in tandem with pigments, or rather, as additives to pigments, and their quantity can be up to 80% of the total pigment mass of the paintwork. The amount of filler that can be introduced into the system, oddly enough, is determined by the performance of the pigments. Namely, hiding power and intensity. The higher these values, the more filler you can add to the paint system.
Fillers have a great influence on the properties of paints, fillers and other coatings in which they are used. In particular, they influence their rheological properties. They increase thixotropy, stability and viscosity (acting as thickeners) and specific gravity.
For effective use of fillers in tandem with pigments, they should have high dispersibility, even higher than the pigments themselves. In addition, they should have low hardness and density, low oil capacity and high whiteness. We should not forget about the availability of the material and its cheapness.
The filler in most cases is a target additive. Adding a filler to a paint material can make it opaque, flame-retardant, acid-resistant and slip-resistant. Thanks to fillers paintwork material increases water and weather resistance of the protective coating, increases its adhesion to the main surface.
In water-based paintwork materials fillers are used as white pigments. During the water evaporation process, the space between the individual fractions of the pigment fills with air, which has a refractive index of one. As a result, an opaque, i.e. hiding protective layer is formed.
A distinction is made between fillers of synthetic and natural origin.
Classification of fillers for paint and varnish industry:
- salts (silicates, carbonates, sulfates);
Basic properties of fillers: brightness, whiteness, size of fractions.