The Performance of Color Paste and Its Influence on Coatings
1、 Coloring power
The coloring power of a pigment refers to the ability of one pigment to show the depth of its color when mixed with another pigment. By mixing the same color, the stronger the coloring power, the less amount of color paste is used, and the degree of reduction in water resistance of color paste coatings and the impact on film performance are smaller. So the quality of products from different manufacturers will vary greatly with the same color. The strength of pigment coloring power not only depends on its properties, but also has a certain relationship with its degree of dispersion. The greater the Dispersity, the stronger the coloring power.
2、 Light resistance and weather resistance
Under the action of light, color will change to varying degrees. Inorganic pigments will gradually darken in color under long-term sunlight exposure, and some pigments may also experience powdering under the action of ultraviolet rays in sunlight. The exterior wall coating should choose a color paste with good light and weather resistance. Generally, the light resistance is greater than 7-8 levels, with level 8 being the best, and the weather resistance is greater than 4-5 levels, with level 5 being the best. Inorganic pigments such as iron oxide series generally have good light resistance, and coatings with corresponding colors have good color retention; Organic pigments are relatively inferior to inorganic pigments, and their prices are much higher. The higher the light resistance of organic pigments, the higher their price. For every level of difference in light resistance, there will be a significant difference in price and weather resistance color retention. When the light resistance is ≤ 6 and the weather resistance is ≤ 3, the price will differ by more than 4 times. So, exterior wall coatings, especially organic color coatings, are priced and sold separately.
3、 Covering power
Covering power refers to the ability of pigments in a coating film to cover the surface of the object being coated, so that the substrate can no longer be exposed through the coating film when covered. The hiding power of pigments depends not only on the ability of the coating to reflect light, but also on its ability to absorb light shining on the surface of the coating. For example, carbon black can fully absorb the light shining on it, thus its hiding power is extremely strong. The hiding power of opaque colored pigments also depends on their selective absorption of light. The pigment is evenly dispersed in the base material, resulting in a smaller particle size and an increase in specific surface area, thus increasing its hiding ability. However, if the particle size of the pigment is equal to half of the wavelength of light, light will pass through the particles without refraction, making them transparent. The higher the crystallinity of pigments, the stronger their hiding power. The hiding power of mixed pigments cannot be calculated based on the additive law of the hiding power of each component in the mixture. In fact, the hiding power of most mixed pigments is greater than the calculated value. Therefore, mixing pigments and fillers in an appropriate proportion will not affect their coverage and is beneficial for reducing costs. The high covering power of the coating results in a high brushing area and low engineering cost. Covering power of common pigments: titanium white 50g/m2, Lithopone 120g/m2, iron oxide yellow 60g/m2, iron oxide red 60g/m2.
4、 Dispersion and adaptability
The dispersibility of pigments refers to the difficulty of dispersing pigment particles in an aggregated state in the coating base material and the dispersion state after dispersion. It is influenced by factors such as pigment performance, preparation method, particle size, and particle size distribution. The dispersibility of pigments has a significant impact on their covering power and coloring power, as well as on the physical and chemical properties of the coating film. The adaptability of pigments is particularly important for lotion architectural coatings. Due to the different types of pigments, the effects of pigments will also show a certain degree of variation, and this tendency is more evident in organic pigments. Pigments are poorly dispersed in coatings, resulting in poor compatibility with the coating and potential flocculation or even fading.
5、 Fineness
The fineness of the color paste is not necessarily the better, as pigments such as phthalocyanine blue and phthalocyanine green are inherently small molecule pigments, with small fineness, large particle size differences, poor dispersibility, poor compatibility with the coating, increased color mixing costs, and easy to cause floating and blooming.
6、 Acid and alkaline 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 exposed to alkali, and gray calcium powder and calcium carbonate will react when exposed to acid. Therefore, attention should be paid to the selection when using. If you choose yellow, blue, etc. produced by non professional manufacturers of color paste at very low prices, or if you do not know their pigment properties, the latex paint will quickly fade, powdery, and alkaline. Therefore, when choosing paint color paste, you must not only focus on low prices, as quality is the most favorable weapon to improve your own brand.
