Overview of pigment additives and introduction of performance effects (3)

10. Opacity or hiding power

Covering ability is one of the important properties of pigments, and it is closely related to the refractive index of pigments, but it is also affected by the particle size of the pigment, the PVC concentration, the degree of dispersion, and the difference between the refractive index of the pigment and the binder or the coating liquid. Impact.

There are many methods for measuring hiding power. The method that is commonly used in the industry and is relatively simple and convenient is the contrast ratio method. In most of the hiding test, it has a contrast ratio of >98% which can be referred to as complete hiding.

The so-called contrast ratio refers to the ratio between the reflectivity of a white object and the reflectivity of a black object. In the paint field, whiteboards with a reflectance of about 80% are usually used as the standard for the contrast ratio.

11. Mould and bacterial resistance

Molds and fungi can be fed from a variety of organic materials. Some bacteria grow in the paint film, making the film black, green, or other forms of discoloration. Some bacteria grow in the paint film or enter the film. In fact, the paint film is destroyed and even the wood substrate is destroyed and invaded.

Anti-mold agents or fungicides can generally prevent the growth of mold on the surface of the paint. The growth of mold is related to the climate. Moistness is a necessary condition for the growth of molds, so the humid climate is beneficial to the growth of molds. Using zinc oxide as a fungicide can effectively control mold. However, the most effective, fungicidal agent that can be used in various situations is phenylmercury, typically in the form of oleic acid, succinic acid, naphthenic acid and acetate. The main problem with the use of amalgam is the handling of the paint and the problems of environmental pollution. Therefore, it is necessary to limit the amount of such anti-mould agents and to minimize handling procedures and reduce the chance of skin contact.

12. Tank stability

Some anti-mold agents can effectively increase the stability of tanks. This problem is most serious in latex or water-based systems. If no effective measures are taken, it will cause paint spoilage, bad smell and gas, and swelling of the tank; In one case, the paint is not spoiled, but the viscosity is reduced and becomes very thin.

All latex paints contain water and fiber, which can cause the growth of bacteria, thereby reducing the quality of certain components, especially thickeners. The result is the loss of viscosity, the generation of odors and the formation of gases. Adding additives to kill microorganisms can produce a disinfection system, but this method can not remove yeast, they will invade the thickener to reduce the viscosity, then you can add thickener and increase the amount of anti-mold agent. Organic compounds and aluminum compounds are effective anti-mold agents where no toxicity is required.

13. Liquidity and Leveling

The smooth advection film must be independent of the coating application method, so the brush coating must have no obvious brush marks, the spray paint should have no orange peel effect, the roller coated roller marks, and the impregnation coating should avoid coating streaks and filaments. Phenomenon. However, not all coatings need to have good flowability and leveling. The use of slow-evaporating solvents, good base materials, and specially treated pigments can improve flow and leveling. Most leveling modifiers improve the wetting properties of the base material, allowing the base material to wet the pigment better.

14. Flowing and sagging

The wet film may tend to excessively advection so that it flows on the vertical surface, making the bottom of the film thicker than the top; or the coating is not uniform, and the uneven flow of paint of various thicknesses results in thick portions. There is a little more downflow, so-called peaks occur, and the thinner ones become thinner and become “valleys”.

In fact, the relationship between drooling and drooping and paint application is large. Paints with very good flow properties do not show signs of brushing. When applied carefully, there is no sagging phenomenon. On the other hand, if the application is improper, there will be poor drooling or sagging. In general, "structure" or "viscous-fluidity" can be introduced into the coating to prevent sagging of the coating.