Particle size distribution is an essential element for successful powder coating performance, the best size for particles depends on the object you want to coat and the thickness you intend for it, for example, if you want to cover a relatively simple object with a thickness of about 50 micron, it is sufficient to use particles with an average grain size of 35 to 40 micron, not only the average size of the particles, but also the distribution of the particles is very important, a lot of accumulation in fine granulations should be avoided. Particles with a diameter of less than 10 micron are fine granulations, in general, it is better that the amount of sub-fine particles is less than 8% of powder coating particles.
The presence of fine granules causes problems such as reducing the fluidity of the powder coating inside the hoses of the spraying machine. They also cause double chargeability. The ratio of electric charge to the mass of these particles is high, which prevents the formation of a coating film, especially in the inner corners. Fine granules also tend to stick together and absorb moisture due to their large surface area.
Particles larger than 100 micron also cause problems. Due to their high mass, larger particles hardly reach the surface of the object. Gravity pulls these particles to the bottom of the coating chamber, and it reduces the efficiency of color transfer, the particles that reach the surface of the object cause the final surface to become rough.
If you are using texture powder coating, you will need very coarse particles, depending on the desired texture, the average particle size may be around 70 to 80 micron, powder coating with such an average size will not have many fine particles, however, you should pay attention to large particles. In fact, particles larger than 200 micron may cause a disproportionate and uneven texture.
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