The pulverization of pigments

Some pigments, such as titanium dioxide, are exposed to the sun for a certain time after being made into the paint film, and the film-forming substances in the paint film are damaged, so the pigments on the surface cannot remain firmly in the paint film, but fall off from the paint film to form a powder layer It can be wiped off or washed off with water This phenomenon is called chalking There are many reasons for the damage of the surface of the paint film, and the pigment contained in it has a great influence on the effect of light In the color paint, the pigment is surrounded by film-forming materials Under the action of light and the photosensitivity of pigment, the destructive effect of light is accelerated, and the paint film is destroyed, thus forming a powder This is a view Pigment is immersed in paint, and its particles are surrounded by multi-molecular layer paint For the paint with strong wettability, the pigment is completely covered, and there is no such interstice as adsorbed air bubble The pigment particles will remain firmly in the paint film without pulverization If the paint can not completely wet the pigment particles, there are flaws in the paint film surrounding the pigment particles, then this kind of pigment in the paint film is prone to pulverization, which is another view Because there are different opinions on the causes of pulverization, the methods to prevent pulverization are different It is considered that the sensitization of pigment is the main reason for the pulverization of pigment How to reduce the sensitization of pigment is studied Salt used It is considered that the wettability of the paint is the main reason for pigment pulverization, so the paint with good wettability should be selected It has been tested that linseed oil with high polymerization degree is used to replace linseed oil with low polymerization degree to make Qinbai powder paint, and the pulverization is obviously weakened Based on this point of view, it has been tested that the paint paste is kept in vacuum to remove the air bubbles hidden in the paint paste, so as to improve the wettability of the paint to the pigment and reduce the degree of pulverization In order to improve its resistance to powdering and reduce its yellow denaturation, we should try our best to reduce the photosensitivity of pigments, such as the surface treatment of pigments It is also a common measure to improve the wettability of pigments by using additives in the production of paints or pigments The influence of this measure on the pulverization should be further investigated.