Component: epoxy acrylic acid modified carboxylic acid ester
Appearance : colorless to light yellow transparent liquid
Solid content: 60%
Acid value: 60-90mgKOH/g
Viscosity (25℃): 810-1250mpa.s
From the cross section of the paint film, it can be found that the damage to the hollow structure of the covering polymer only occurs in the paint film between 2 to 4 pm from the surface, and a large amount of covering polymer structure in the paint film is intact, so the covering of the paint film Power will not be affected.
Effect on wet cover
As we mentioned earlier, the covering polymer is supplied in the form of an emulsion. The cavities of the covering polymer are filled with water. When drying, the water evaporates through the ptfe dispersion producers polymer shell, and the cavities are occupied by air with a much lower refractive index. , The light is effectively scattered, resulting in an increase in hiding power. Therefore, the covering polymer only provides covering power after the paint film is dried, which is not helpful for wet covering. However, for professional constructors, wet covering is usually an index to evaluate the performance level of the coating. The coating rate of the coating is closely related. In the drying process of traditional economical coatings, the so-called “dry coverage” is obtained as the paint film becomes porous. However, the increase in dry hiding power is often associated with inferior latex paint, because the appearance of voids in the paint film will lead to a decrease in resistance. However, with the introduction of covering polymers, we can obtain an increase in covering power without sacrificing the resistance of the paint film.
Therefore, new concepts need to be established when evaluating the quality of coatings and determining the requirements for construction thickness.
In order to better understand the effect of the hiding polymer on the change of color and hiding power, we conducted a study on the change of hiding power during the drying process of the paint film, and the results are shown in Figure 20-15. During the drying process of the coating, the contribution of titanium dioxide to the covering gradually decreases. This is because with the volatilization of water, the titanium dioxide particles become dense, which leads to the generation of over-aggregation, which causes the decrease of scattering efficiency. In addition, the medium around the titanium dioxide particles The increase in refractive index will further reduce the scattering efficiency of titanium dioxide. In the formula with PVC less than the critical pigment volume concentration (CPVC), the paint film will not produce holes during the drying process, so the dry film coverage is lower than the wet film, while in the formula with PVC greater than CPVC, due to air coverage during drying, This will increase the hiding power of the dry film and cause the color of the paint to fade.
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