Why does the product have dots after adding black masterbatch? Because carbon black is the main pigment in black masterbatch!

Among all pigments, white masterbatch (titanium dioxide) is the most easily dispersed, while black masterbatch (carbon black) is the most difficult to disperse.

The particle size of pigment carbon black is nanoscale and invisible to the eye. Under natural conditions, carbon black will cluster between molecules, requiring greater mechanical force to separate them. At the same time, more and better carriers are needed to wrap each molecule together, so that molecules no longer cluster.

Therefore, when designing the formula of black masterbatch, it is necessary to fully consider the characteristics of carbon black. The formula must contain sufficient carriers. If the percentage of carbon black in the black masterbatch is too high, the percentage of carriers will correspondingly decrease, so the encapsulation effect of pigment carbon black molecules will be slightly poor.

As a black masterbatch for dyeing and granulation, the content of carbon black can be appropriately increased, which can reduce the amount of black masterbatch, reduce costs, and do not change the physical properties of the material. Moreover, during the granulation process, the screw of the granulation machine will disperse and shear the black masterbatch again. As for injection molding, film blowing, sheet material, sheet metal, extrusion and other processing processes, the screw in the processing machine usually only has a push function and almost no mechanical shear force. Therefore, it is required that the dispersion of the black matrix is particularly good, so as to make the product surface smooth.

In summary, the content of pigment carbon black in black masterbatches used in injection molding, film blowing, sheet materials, extrusion and other processes should not be too high, but to ensure the blackness and sufficient covering effect of the product, it is recommended to choose carbon black varieties with good dispersibility in the black masterbatch, and the content is recommended to be around 40%, not more than 50%! The carbon black content of the color masterbatch used for dyeing and granulation direction can be selected to be around 50% or above.

Precautions for using black masterbatch

  • 1. Choosing the most suitable one may not necessarily mean that the more expensive the better, for example, some color masterbatches may be very black on ABS, but not necessarily black on PP.
  • 2. The most important performance of black masterbatch is dispersibility. It is better to choose a well dispersed masterbatch and add an extra portion, rather than choosing a so-called high blackness and lack of dispersion, especially in the field of film blowing, unless you are using it for granulation.
  • 3. Compatibility with raw materials, the use of color masterbatches with different substrates in incompatible plastics can lead to delamination and peeling of the product.
  • 4. The addition proportion is appropriate, and if the amount is small, the dyeing will not be uniform. If the amount is large, it may affect the physical properties and also increase the cost.
  • 5. Stir evenly with the raw materials, it is best to choose a color masterbatch that is equivalent in size to the raw material particles, otherwise some parts will arrive and some parts will still be the original color.
  • 6. The processing temperature should not be too high or too low, otherwise it may lead to poor plasticizing effect of the color masterbatch. Affects the surface smoothness and shrinkage ratio of the product.

The most important point: It’s better to directly use carbon black in the PVC industry. The price is good, the amount added is small, and the effect is good.