Q
Effect of Particle Size of Powder Coatings on Properties
A
Relationship between particle size and powder quality:
The particle size distribution of plastic powder is closely related to the texture, smoothness, glossiness, particle size,  electrification effect, powder fluidization effect, storage stability, and powder recovery rate.

1, appearance, leveling and quality.
  In general, the smaller the particle size of the powder, the better the planarity of the coating when cured;  at the same spray thickness, particles with a smaller particle size are less prone to particles; and appearance is smoother.

2, charged effect and powder rate:
Increasing the charging ability of the powder particles will increase the powdering rate of the powder coating. 
The main adsorption force of  spraying is electrostatic force, and the powder on powder rate mainly 
depends on how much the powder particles are charged. The charge of the powder is proportional to the square of  the particle size of the powder. Increasing the particle size increases the amount of powder charge and increases the rate of dusting. 

However, the particle size of the powder particles can not be too large,otherwise, the gravity of the large particle powder exceeds the aerodynamic force and electrostatic force. In the flying process, the powder coating has fallen to the surface of the workpiece due to the effect of gravity, cause the rate is reduced. 
The powder is too thin and the chargeability is reduced, and the coating efficiency will be reduced. 
The ultra-fine powder (particle size <10 μm) is basically not charged, and the powder too fine also increases the difficulty of powder production.


3, Fluidization effect of powder:
When the powder is too fine, the fine powder will bind into the powder mass and will not spread when fluidized. 
When sprayed on the workpiece, it forms a sleek packet that affects the appearance of the coating. 
When the powder is too thick, the powder is not easily fluidized in the powder bucket.

4, The stability of Storage
Stability refers to the ability of the powder coating keep the size of powder particle, shape and hardness under the certain conditions, 
that is to say whether the powder absorbs moisture and clumps, and the stability is decreased. 

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