The difference between thin coating powder and conventional powder is because it can be sprayed thin?

The advantage of powder coating is that a coating can obtain a thick coating film (50~150μm), high production efficiency, resource saving, reduce VOC emissions, in line with the requirements of
modern environmental protection concepts.

Therefore, powder coatings have been greatly developed
.
However, the coating film of some products does not need to be too thick, such as the thickness of the coating film for household appliances has caused the user's material cost to increase, the composition performance of the coating parts is not good, and even the problem of unstable mechanical properties of the coating The coating coatingol.
com
online.

In order to reduce the coating cost and the pass rate of one spray, thin powder coatings have a special application area, and thin and uniform coating film is a very important performance
of thin powder coating film.

The coating thickness of conventional powder coating is 60~80μm, and only by reaching the film thickness can the coating workpiece be completely covered, and the flatness of the coating film and various performance indicators meet the requirements
.

If the film thickness of conventional powder coatings is reduced to 45~60μm, it is very difficult
to achieve the above properties and ensure the uniformity of the powder on the first powder and the corners.

Therefore, improving the particle size distribution, hiding power, leveling, and charging efficiency of conventional powder coatings is a problem
that must be solved in the development of thin-coated powder coatings.

According to the requirements of thin-coated powder coatings and coatings, by optimizing the formula, adjusting the production process, combined with the user's various spraying process parameters, the development of the user's existing production equipment, curing conditions, only the spraying air pressure slightly adjusted, you can achieve uniform thin-coated thin-coated powder coating
.

Comparison of particle size distributions

The particle size distribution of thin coatings and conventional powder coatings is shown in Table 1 and Figure 1, Figure 2
, respectively.

From the comparison of the data in Table 1, it can be seen that the particle size distribution of thin coating type and conventional powder coating is significantly different, and the average particle size is 21.
1μm and 29.
28μm
, respectively.

From the perspective of coating film thickness, the thickness of thin coating film is 45~60μm to achieve satisfactory coating covering power, and the flatness and appearance effect are basically consistent with conventional powder coatings; The conventional type requires 60 to 80 μm to meet the requirements
.

Thin-coated powder film thickness, hiding power decreases, by increasing the amount of pigment, adding dispersion additives and other methods can improve the dispersion of pigment fillers, improve the hiding power; The leveling of the powder coating film is achieved by adjusting the particle size distribution, that is, the adjustment of the average particle size
.

The average particle size of thin-coated powder coatings is small, and the properties of dry powder fluidity, storage stability, and powder rate are deteriorated, but by adjusting the powder coating formula, moderate addition of electrants, loose additives, etc.
can be improved to meet user requirements
.

The coating effect of thin-coat powder coatings

Spray testing is carried out on the refrigerator spraying line with a thin-coated powder coating
.
The process conditions of the first powder electrostatic spraying test are shown in Table 2, 10 refrigerator test boards are extracted, and the coating film thickness of 10 points is determined on each plate, and the measurement results are shown in Table 3
.

Film thickness: the maximum value is 66.
2μm, the minimum value is 51.
8μm, and the total average value is 56.
9μm
.

The process conditions for the second thin-coat powder coating electrostatic spraying refrigerator breadboard are shown in Table 4, and the 10 refrigerator breadboards sprayed are extracted and the coating film thickness of 10 points is determined for each plate (Table 5).

The results of the coating thickness determination are: the maximum value is 65.
5 μm, the minimum value is 53.
9 μm, and the average value is 58.
1 μm
.
The average thickness of the powder coating film in the two tests was 57.
5 μm, and the coating thickness was lower than the low limit of 60 μm
for conventional powder coating film.

Some of the process conditions and the area of the quality powder coating that can be sprayed by the thin-coated powder coating in the test are shown in
Table 6.

The above test results illustrate:

(1) The powder coating area per kilogram of the two tests was above 10.
0m2/kg, and the average value was 10.
28 m2/kg;

(2) The defective rate of plate is stable at about 5%;

(3) The coating film thickness is relatively stable, the maximum film thickness of the first test is 76μm, the minimum value is 37 μm, and the maximum film thickness of the second test is 87μm, the minimum value is 42μm;

(4) The process parameters of the spraying line are basically stable, and the coating film has good leveling and hiding power
.

It should be noted that compared with conventional powder coatings, although thin coating powder coatings can obtain thinner coating films, from the results of coating thickness determination, film thickness uniformity needs to be improved, and the key problem is that the powder supply stability of the powder supply system needs to be improved
.

Comparison of spray characteristics

Thin coating powder coating and conventional powder coating electrostatic spray refrigerator are used respectively, and the coating film thickness is compared with the spray area per kilogram of powder, and the test results are as shown in Table 7
.

The test results show that:

(1) After switching to the thin-coated powder coating spraying model, the thinly coated powder per kilogram can be sprayed 2.
63 m2 more than conventional powder, saving 34.
38% of the powder coating dosage;

(2) Compared with conventional powder coatings, the average film thickness of thin-coated powder coatings is reduced by 25μm; The difference between the maximum and minimum film thickness values was reduced from about 120μm to 50μm for conventional powder coatings, and the defective rate of coated products decreased by 6.
04%;

(3) The penetration of thin-coated powder coatings is strong, which significantly improves the powder rate in dead angles, and the film thickness is uniform compared with conventional powder coatings, which greatly reduces the coating cost and improves the coating efficiency
.

epilogue

From the above test results, the following conclusions can be drawn:

(1) Through the adjustment of powder coating formula, especially the regulation of particle size distribution of powder coatings, thin coating powder coatings can be prepared;

(2) Through the adjustment of the coating process, a thin coating film with an average thickness of 60μm or less can be obtained by using a thin-coated powder coating, which not only saves the amount of powder coating, but also reduces the coating cost
.