Yuan Lei's Little Knowledge | Seven Ways to Improve Powder Coating Rate

Release time:

2024-01-29 09:34

Powder coating on the powder rate, can be understood as the coverage of the powder spraying workpiece, powder coating on the powder rate is the most specific performance of its utilization.

Ideally, it is desirable that 100 percent of the sprayed paint be adsorbed on the workpiece without any paint entering the recovery system. The reality is that due to the influence of spraying system, powder characteristics, workpiece shape and other factors, the powder coating on a normal powder rate is below 60%.



Factors affecting the rate of powder

★Chargeability of Powder Coatings

There are many factors that affect the powder rate. From the perspective of spraying, the powder coating is subjected to compressed air driving force, air resistance, powder gravity and electrostatic force after coming out of the spraying system;

The ideal state is that when the powder is close to the workpiece to be sprayed, the force of compressed air, air resistance and gravity is 0, and the powder paint particles are adsorbed to the surface of the workpiece only under the action of electrostatic force.

Therefore, the main factor that conventionally affects the powder rate is the charging of powder coatings.

★Other influencing factors

In addition to the characteristics of the powder coating itself, in addition to the factors affecting the powder rate of the powder coating is also related to the type of spray gun, process parameters, workpiece shape, workpiece hanger density, spray gun location settings.


Method of improving powder coating rate

① Control the particle size and distribution of powder coating

Since the particle size of the powder coating is related to the charging amount, the larger the particle size, the greater the charging amount. If the particle size distribution of the powder coating is uneven, the particle size of the powder coating will reach the surface of the sprayed object first, and the particle size of the powder coating will reach or cannot reach the surface first, thus reducing the primary powder loading rate and easily causing the appearance quality problem of the paint film.

② Improve the charging of powder coatings

An appropriate amount of conductive additives are added to the formula to give the powder particles more charge. There is a strong electric field in the area from the high-voltage electrostatic spray gun to the workpiece, and the air is ionized to produce hundreds of millions of ions. When the powder particles of the electric booster pass through this area, they are polarized, which can trap more negative ions and carry more charge. For the groove dead angle and other parts due to the weak power line of the Faraday effect, the powder particles with more charge can reach the surface of the workpiece by their own strength, thus improving the powder on these parts.

③ Increase the resin content

In the composition of the powder coating, the resin as a polymer compound has the highest dielectric constant, and the dielectric constant of the pigment and filler is low. If there are more substances in the powder coating with a higher dielectric constant, it will increase the powder rate at one time during spraying, but it will also increase the cost.

④ Reasonable selection of filler

Filler fineness and dispersion are closely related to the powder. Precipitation on the powder is higher than the general ultrafine heavy barium, barium sulfate is better than calcium carbonate.

⑤ Control of physical properties such as powder fluidity/moisture

The moisture content and powder fluidity of powder coatings in the manufacturing process are also closely related to the powder rate. Under the influence of equipment cleaning or weather and condensed water, the powder will contain more or less part of water, which will directly affect the fluidity of the powder and the surface of the coating film, and also reduce the powder rate. Therefore, it is necessary to reduce the water entering the powder by reducing the water washing equipment and controlling the humidity of the air inlet.

Choosing the appropriate spray gun

The size of the first powder rate of the spray gun is related to the type of spray gun, process parameters, the shape of the workpiece and the spraying method. A good spray gun can reach 80% of the rated powder rate.

⑦ Reasonable spraying distance

In the case of static voltage determination, the electric field strength is inversely proportional to the interelectrode distance. When the distance between the spray gun and the workpiece is too short, spark discharge will occur; the distance is too far, the powder on the powder rate will be reduced.

Method, powder coating, workpiece, powder, spray, spray gun, influence, particle size, improve, once

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