1. Judgment of carbon black blackness
After we have made the black paste, how to compare the blackness? The color pigment paste is easy to compare and observe, but the black is difficult to observe and judge. Sometimes the opposite happens. For example, add carbon black pulp A and B in the same proportion in the same emulsion, and compare it on the cardboard by scratching the cardboard. After the paint film dries, it is found that the blackness of the A color paste is better, but scratch the card on the glass plate and observe it against the light. , found that the blackness of B is higher. The main reason for this is that the former is reflected light entering the eye, while the latter is transmitted light. Scratch film observation is mainly to observe the dispersion of carbon black. The finer the fineness, the larger the total surface area of the dispersed pigment in general, the greater the ability to absorb light, and the higher the blackness, that is, the darker the color. When the rod wire of the wire rod is thick enough, the coating film is thick enough, and the observation results of the two will tend to be consistent. In practical applications, the observation method needs to be determined according to the products used in the industry. Usually, direct observation is used for coating, and the thickness of the coating film is about 150 μm; some transparent products need to be observed with a thin wire rod or a thin applicator coating film.
2. What are the factors affecting the blackness of carbon black paste
The previous article introduced that blackness has a great relationship with dispersion and primary particle size. For the same carbon black, the more fully the carbon black is dispersed, the better the blackness will be. The better the dispersion of carbon black, the greater the total surface area of the pigment, the greater the ability to absorb light, and the higher the blackness, that is, the darker the color.
The other is the carbon black particle size, here refers to the original particle size of carbon black. In many cases, the grinding is sufficient, but the blackness is still not good, which may be due to the original particle size of carbon black. The size of carbon black primary particles determines the blackness of carbon black. The primary particles of high-pigment carbon black are about 10 nanometers, and the ordinary carbon black is more than 50 nanometers. When the carbon black is fully dispersed, the finer the carbon black, the higher the blackness. Otherwise, the blackness of the high-pigment carbon black sample may not be as good as that of ordinary carbon black, which is also the situation encountered by many people.
Therefore, when we get the blackness of the black pulp is not enough, don't always think that there is a problem with carbon black itself, but indulge in the selection of carbon black pigments, the preparation of grinding process and equipment should also be considered, the best grinding process can be fully dispersed carbon black slurry.