An introduction to the performance indexes of color pastes that you don’t want to miss!
Color strength of color paste (coloring power)
For the comparison of water-based color paste, color strength is an important index, which reflects the color concentration, color spreading performance and pigment dispersion flocculation of the paste.
The data is measured by the number of parts of pigment paste required for the color to reach 1/25 of the International Standard Depth (ISD), the smaller the value, the higher the color strength. The value represents the number of grams of pigment paste to be added to the white base coat: in emulsion paints – 25% titanium dioxide content in the white base coat (1/25ST).
2 Compatibility of color pastes (color spreading properties – finger method)
The compatibility of the color paste and the use of the system is the key to affect the color of the color paint floating color bloom, flocculation and some surface defects of the paint film. Before using the color paste to match the color, must do the compatibility test, additives can often be used to solve the compatibility of the color paste and paint.
Add the color paste to the white paint, generally formulated into medium and light colors, applied to the surface of the coated material or imitation of the surface of the coated material, to be about to condense, use your fingers to grind the surface part of the coating film, after drying, observe whether there is a clear color difference (visual inspection). If the fineness of the color paste is not enough, the dispersing performance is not good all lead to the color paste color spreading is not good, will affect the reproducibility of the color paint.
3 Dispersing performance of color paste (degree of flocculation)
The degree of unflocculation of pigment particles by additives determines the size and stability of the dispersion of color paste. Generally speaking, it is impossible to achieve complete unflocculation (i.e. the pigment in the system into the original level of particles of uniform and stable existence), just in the form of pigment particles of the appendage uniformly distributed in the system. A good color paste has a rather high degree of deflocculation, that is to say, the agglomerates are as small as possible, so that it has good coloring power, excellent color development and storage stability. Because the dispersion performance of the color paste is not good, the pigment flocculent in the color paste and the white pigment in the base material, filler particles in the migration difference is easier to reflect, this difference often makes the pigment flocculent is no longer uniform distribution, when the film due to the film in the temperature, density and surface tension of the tiny differences in the film, the pigment flocculent and the paint base to participate in this movement naturally, pigment flocculent and then separated, resulting in floating color and hair flower. If the dispersion performance of the color paste is good, the occurrence of floating and blooming can be avoided.
The good or bad dispersibility of the paint itself also directly affects the floating and blooming of the color paint.
4 One of the structural properties of the color paste (light resistance, weatherability)
Color paste light resistance and weathering test is through outdoor exposure, but the actual outdoor exposure time is too long, the general color paste performance testing is mostly through the instrumentation simulation test.
Light resistance: Use outdoor acrylic emulsion paint to make 1/3ISD and 1/25ISD standard color samples for exposure. Xenon lamp light source (1000W) exposure of 72 hours, the use of 1-8 grade blue wool ruler and the standard color samples at the same time exposure, resulting in color difference to the rating, 1 grade is the worst, 8 grade is the best, (has been assessed by the color measurement software)
Weatherability: Use outdoor acrylic emulsion paint to make 1/3ISD and 1/25ISD standard color samples for exposure. Using ATLAS artificial aging instrument exposure 500 hours, using ISD gray card for color difference rating, 1 level for the worst, 5 levels for the best. (Has been evaluated by the color measurement software)
5 Pigment content of color paste
The pigment content is only for reference, and cannot be used as the index for evaluating the performance of color paste. The coloring power of color paste is not simply proportional to the pigment content. For the same pigment content, there is a big difference in coloring power with different fineness.
In order to ensure the stability of the coloring power of the color paste, the pigment content of the color paste is within a certain range of changes in the value of the color paste information provided by the value is a typical reference value.
6 Fineness of color paste
Fineness is an intuitive index reflecting the coloring power dispersion effect and storage stability of the color paste. Generally for the same pigment color paste, the smaller the particle size, the larger the specific surface area, and thus the covering ability is also increased, the higher the coloring power; the finer the fineness, the higher the luster, the better the dispersion effect and storage stability.
Of course, the fineness of the color paste is not the finer the better, because when the particles become smaller, its specific surface area increases, the absorbed light energy increases, the degree of destruction also increases, resulting in a decrease in weather resistance; and particle size is too small in the paint film drying, along with the precipitation of water, the color paste together with the migration of the surface, easy to cause the color is not allowed to match the color and the wall color difference.
7 Compatibility between color paste and paint
Finger research method to take 100 grams of white paint, add 2-3 grams of color paste to be tested, fully stirred, coated on the surface of the coated object, to be about to condense, with a finger to grind the surface layer of the film part of the paint film to be dry, observe the finger research and rubbing and not rubbing the place whether there is a difference in color, such as the difference between the larger, then the color paste is not good with the compatibility of the test paint, the color paste of this paint mixing out of the paint is prone to produce floating color phenomenon. If the color is the same, generally does not produce floating color phenomenon.
8 color paste structural properties of the second (chemical resistance)
The chemical medium resistance of water-based color paste is mainly acid resistance, alkali resistance, that is, chemical migration resistance. The performance basically depends on the pigment itself, and this factor must be considered in the color paste for outdoor use. Generally water-based paints are also required to be acid and alkali resistant, not organic solvents and other chemicals.
Acid and alkali resistance: According to DIN16524 standard, the acid and alkali resistance of the color pastes are determined by drying (105℃) and placing them in 1% sulfuric acid and 2.5% sodium hydroxide solution for 24 hours respectively, and then removing them and washing them. According to the color bleeding and color change, it is evaluated according to the 5-level standard, and the 5-level indicates excellent acid and alkali resistance, and the 1-level indicates very poor acid and alkali resistance.
9 Other physical and chemical parameters of color paste
(Density, viscosity, PH value, pigment content, solids and fineness and gloss)
Density: the unit is grams / cubic centimeter, measured according to the provisions of GB/T1756.
Viscosity: Important index to reflect the storage stability of color paste. (STM- Ⅲ Stormer viscometer)
PH value: PHB-2 portable PH meter to determine the water-based high-quality color paste system of acidity and alkalinity (PH value) is generally between 7-10, so the color paste in the PH value of 7-10 paint system in the color retention, coloring power and color spreading and other performance is excellent.
Fineness and gloss: a visual index reflecting the dispersion effect and storage stability of color paste. Generally for the same pigment color paste, the smaller the fineness, the higher the gloss, the better the dispersion effect and storage stability.
10 Quality stability of color paste
Generally through the strict control of the production formula – raw materials – production process – finished products, to ensure the consistency of the color paste’s solid fraction, fineness, viscosity, coloring power, color spreading, light resistance and weather resistance. (Evaluation with color matching software, Lab value and color difference control DE< 1.0)
General storage stability of water-based color paste at room temperature of about 25 ℃ when stored for a year without obvious delamination, caking, back to the coarse, precipitation and other defects, and coloring power, color spreading and other physical and chemical properties have not been significantly reduced. Usually can be accelerated by hot storage and freezing experiments to determine the aging, through the opening of the can to assess the effect of evaluation and color measurement software assessment
