There are many kinds of pigments with different performances, not all pigments can be used in powder coatings. Due to the particularity of its own process, powder coatings should pay attention to the following points when choosing pigments.
Pigment dispersion is better, the best dispersion particle size is 0.2 ~ 0.9μm, not easy to agglomerate.
Pigment hiding power and coloring power are stronger.
The thermal stability is better, and the temperature must be at least 160 ℃.
Pigments must have certain light and weather resistance, such as not easy to fade, anti-powdering, and long-lasting physical properties.
The oil absorption of the pigment is moderate, and the bleeding resistance is better.
Filler selection
Adding a certain amount of filler to the powder coating can increase the hardness and other mechanical properties of the coating, and can reduce the cost, which is an effective way to adjust the cost of the powder coating.
The fillers used in powder coatings are mainly calcium carbonate and barium sulfate, and like bentonite, talc, quartz powder, etc. can be regarded as functional fillers, the overall amount is very small.
According to factors such as production process and raw materials, calcium carbonate can be divided into two types: light calcium carbonate and heavy calcium carbonate. Both types of calcium carbonate have applications in powders.
There are also two types of barium sulfate: precipitation type and barite type. The former is made by chemical reaction, and the latter is made by grinding natural barite.
The issues to be noted when selecting fillers are:
The whiteness of the filler should be high, which can reduce the amount of titanium dioxide.
Less impurities, considering the particularity of the powder coating process, more impurities in the filler will affect the surface decoration of the coating film (there are many particles on the coating surface and poor leveling).
Do not choose fillers with too coarse particle size, because they are not easy to disperse and wear on the screw.
The filler should be loose, not caking, and the water content should be low.