The regulating effect of silica on the gloss of coatings is mainly reflected in its application as a matting agent. The following is a detailed analysis of how silica adjusts the gloss of coatings:

1. The principle of silica as a matting agent

Silica, especially fumed silica, has a refractive index that is relatively close to that of the film-forming resin (about 1.46), which makes it an effective matting agent in coatings. When silica is evenly dispersed in the coating, its fine particles can form an uneven structure on the surface of the coating. When light shines on this uneven coating surface, diffuse reflection occurs, that is, the light is scattered, thereby reducing the gloss of the coating.

2. Factors affecting the matting effect of silica

Particle size and its distribution:

The particle size of silica is one of the key factors affecting its matting effect. Generally speaking, silica with a larger particle size has a higher matting effect when used in a paint film.

The narrower the range of particle size distribution, that is, the more uniform the particle size, the higher its matting efficiency.

Pore volume: For a given particle size of silica matting agent, its matting efficiency will increase with the increase of pore volume. This is because the increase of pore volume increases the roughness of the coating surface, thereby enhancing the diffuse reflection effect.

Surface treatment:

The surface treatment of silica will also affect its matting effect. Silica with proper surface treatment can be more easily dispersed in the coating to form a more uniform coating film, thereby improving the matting efficiency.

3. Application examples of silica in coatings

Silica is widely used as a matting agent in various coatings, including water-based and solvent-based transparent wood coatings (such as wood varnishes), high solids coatings, architectural coatings, wallpaper coatings, etc. In these coatings, silica can effectively reduce the gloss of the coating film and make the coating present a soft matte effect. This effect not only improves the decorativeness of the coating, but also increases the weather resistance and scratch resistance of the coating.

4. Precautions

When using silica as a coating matting agent, you need to pay attention to the following points:

Dispersion: Make sure that silica can be evenly dispersed in the coating to avoid agglomeration. This can be achieved by selecting the right dispersant and dispersion process.

Dosage control: According to the formulation and performance requirements of the coating, the amount of Silica should be reasonably controlled. Excessive use may cause the coating to become too rough, affecting the appearance and feel.

Coordination with other additives: Silica is often used in combination with other additives such as rheological additives, dispersants, etc. It is necessary to ensure that there is no adverse reaction between these additives and that they can synergistically improve the performance and glossiness adjustment effect of the coating.

In summary, as an effective matting agent, Silica can significantly reduce the gloss of the coating film in the coating, improve the decorativeness and weather resistance of the coating. When using it, it is necessary to pay attention to its dispersibility, dosage control and coordination with other additives.