Matting agents are substances that can reduce the glossiness of the surface of the coating film. In practical applications, people often don't need the paint to emit too much gloss. The production of this kind of paint requires the use of matting agents. The choice of matting agent, in addition to its own chemical and physical properties, dosage, particle size, particle size distribution, pore volume of silica matting agent, etc. are all important factors that determine the selection of matting agent. The more you use, the more the gloss will drop. The larger the particle size, the more effective the extinction. Of course, the particle size should be compatible with the thickness of the coating film.
Matting agents for water-based coatings, high-solid coatings, radiation-cured coatings, powder coatings, etc. are very different from traditional solvent-based coatings.
1. Selection of matting agent for traditional solvent-based coatings. Due to the presence of organic solvents, the film-forming shrinkage is large and matting is easy, although the use of matting agents is also different due to the difference in the resin system and film thickness of this type of coating. But the versatility is large, mainly to adjust the amount and particle size of the matting agent. Synthetic silica gels with high pore volume are effective. To prevent matting agents from settling in the clear coat, wax-treated silica matting agents are preferred.
2. Selection of matting agent for water-based coatings. Water-based paints rarely use volatile organic solvents. Dry hydrated silica is not very suitable, because the micron-sized synthetic silica matting agent is a porous substance with strong water absorption capacity and poor stability of base material particles, which will easily deteriorate the quality of the coating film. The syloid W300, W500, and W900 matting agents of Grace are hydrogel-type silica matting agents with a water content of 55% and a pore volume of 1.2mL/g after drying. The appearance is still fluid white powder. Easy to add, strong wettability, easy to disperse, no water absorption, no air bubbles, and the particle size release remains unchanged after drying. Although the pore volume of the W-type matting agent is small, because the volatilization of the water-based paint will shrink the surface of the coating film when it dries, the matting is relatively easy, so it is a more satisfactory matting agent for water-based paints.
3. Matting agent selection for high solid coatings. When the solid content of the coating exceeds 70%, it is difficult to extinction. Coarse silica matting agents are effective for matting high solids alkyd and polyurethane coatings. And to a higher dosage.
4. Selection of matting agent for UV light-curing coatings. Because UV light-curing coatings do not contain volatile organic solvents, the shrinkage of the wet film is very small after drying, and the drying time is short. Overall, matting is difficult. However, the coating with low reactivity is relatively easy to extinction, while the coating with high reactivity is difficult to extinction. The syloidRAD2005 and 2105 recently developed by Grace have small average particle size and small pore volume. The actual measured value is only 0.9ML/G, and the special organic treatment agent for the surface is as high as 20%, but it will not cause "cryptic bubbles" and has high extinction efficiency.
5. Matting agent selection for powder coatings. Commonly used matting agents include wax-type matting agents, non-wax-type matting agents and matting curing agents. The wax-type matting agent is non-reactive, and mainly produces matting through physical effects such as miscibility with the film-forming substance; the matting principle of the matting Curing Agent is to use two different reactive curing agents in the powder coating formula, one The reactivity is high and the reaction speed is fast, while the other kind of reactivity is low and the reaction speed is slow. Due to the difference in reaction speed and the compatibility between the reaction products, a microscopic rough surface is produced, which diffuses light and achieves extinction. By adjusting the amount of resin and matting curing agent, the gloss of the coating film can be controlled, which is more convenient to use.
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