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What is the effect of the performance index of the pigment on the coating?

Mar 06, 2019

What is the effect of the performance index of the pigment on the coating?

Tint strength
The tinting strength of a pigment refers to the ability of a pigment to appear in color shades after mixing with another pigment. To adjust the same color, the stronger the tinting strength, the less the amount of color paste used, and the less the degree of water resistance reduction of the color paste coating and the film properties. Therefore, the quality of the products of the same color and different manufacturers will be very different. The strength of pigment tinting strength depends not only on its nature, but also on its degree of dispersion. The greater the dispersion, the stronger the tinting strength.

Lightfastness and weather resistance
The color of the pigment will change to some extent under the action of light. Inorganic pigments will gradually darken under the sun for a long time, and some pigments will also cause pulverization under the action of ultraviolet rays in sunlight. Exterior wall coatings should use pigments with good light and weather resistance. Generally, the light resistance is greater than 7~8, 8 is best, weather resistance is greater than 4~5, and 5 is best. The higher the light resistance of organic pigments, the higher the price, the difference in light resistance, the price and weather resistance, the light resistance is ≤6, and the weather resistance is ≤3, the price will differ by more than 4 times. Therefore, the exterior wall paint, especially the organic paint, is a price tag.

The pigment in the coating film can cover the surface of the object to be coated, so that the substrate can be covered and no longer can be exposed through the coating film. The strength of the pigment hiding power depends mainly on factors such as refractive index, ability to absorb light, crystal structure, and degree of dispersion. The hiding power of the pigment depends not only on the ability of the coating to reflect light, but also on its ability to absorb light that is incident on the surface of the coating. For example, carbon black completely absorbs the light that shines on it, and thus its hiding power is extremely strong. The strength of the opaque color pigments is also dependent on their selective absorption of light. The pigment is uniformly dispersed in the base material, the particle size is small, the specific surface area is increased, and the hiding power is increased. However, if the particle size of the pigment particle is equal to half the wavelength of the light, the light will be The particles are transparent by advancing through the particles without refraction. The higher the crystallinity of the pigment, the stronger the hiding power. The hiding power of the mixed pigment cannot be calculated according to the addition rule of the opacity of each component of the mixture. In fact, the hiding power of most mixed pigments is larger than the calculated value. Therefore, mixing the pigment and the filler in an appropriate ratio does not affect the hiding power, and is advantageous in reducing the cost. The hiding power of the coating is high, the painting area is high, and the construction cost is low.

Dispersibility and adaptability
The dispersibility of the pigment refers to the ease with which the pigment particles in the aggregate state are dispersed in the coating base and the dispersion state after dispersion, which are affected by factors such as pigment properties, preparation methods, particle size and particle size distribution. . The dispersibility of the pigment has a significant influence on the hiding power of the pigment and the strength of the coloring power, and also affects the physical and chemical properties of the coating film. The adaptability of pigments is particularly important for emulsion architectural coatings. Due to the different types of pigments, the effect of the pigments will also show a certain degree of difference, and this tendency of organic pigments is more obvious. The pigments are poorly dispersed in the coating, and the matching with the coating is poor, and the coating may have potential flocculation or even fading.

The fineness of the color paste is not as fine as possible, because pigments such as phthalocyanine blue and phthalocyanine are themselves small molecule pigments, the fineness is too small, the particle size difference is large, the dispersibility is poor, and the compatibility with the coating is not Well, the cost of coloring increases, and it also evokes floating colors.

Acid and alkali resistance
The acid and alkali resistance of pigments is also an important performance indicator for their use in architectural coatings. For example, iron blue or chrome yellow will decompose when it is alkali, and gray calcium powder and calcium carbonate will react with acid, so you should pay attention to the choice when using. If the price is very low, the yellow, blue, etc. produced by the non-professional manufacturer of latex paint, because of the low price or the pigment performance, the latex paint will soon have faded powdered efflorescence, so the customer chooses the paint. And the color of the latex paint must pay attention to the choice.

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