In recent years, the application scope of powder coatings, mainly epoxy resin powder coatings, has been continuously expanding in China, and people’s requirements for powder coatings and coating equipment are also getting higher and higher; with the rapid development of applications, the spraying process has gradually matured, and in turn, New requirements for the performance of epoxy powder coatings themselves.

At present, the powder coating types continue to innovate. In addition to epoxy powder coatings, a large number of polyester-modified epoxy powders and polyester powders have appeared on the market. The new varieties have greatly improved the outdoor durability of powder coatings. The color variety of powder coatings has been continuously increasing. The powder coatings have developed from the past high-performance thick coating and anti-corrosion applications to the current ultra-thin coating and decorative applications. This is a leap forward for China's powder coatings. According to reports, most of powder coatings use electrostatic spraying technology—cold coating of powders and film formation after heat curing. The electrostatic spraying process of powder coatings essentially consists of two major parts: performance of powder coatings and electrostatic spraying equipment including spraying. Processes, they are interdependent, mutual promotion, ideal for electrostatic spraying powder coating and good electrostatic spraying equipment, in order to obtain high quality powder coating film, lack of one of the good performance can not get high quality coating film This has been confirmed by the practice of powder coating spraying for many years.

The in-depth research of powder coatings and electrostatic spraying equipment has become the direction of the industry. A large number of electrostatic spraying tests have shown that in addition to the exploration and improvement of electrostatic spraying guns and powder feeders for spraying equipment, powder coatings suitable for electrostatic spraying are also carried out. With the analysis, the conclusion is obvious: with the same spraying equipment under the same process conditions, using different powder coatings, the obtained powder coating deposition rate is not the same, reflecting the difference in the quality of the coating film. Experts from the China Epoxy Resin Industry Association said that people often do not pay attention to their characteristics during the electrostatic spraying process of powders, so that when the coating film has some defects such as bubbles, pits, depressions, shrinkage holes, spotted spots, and even not painted. When powder is nowhere to be solved, it is difficult to analyze the existing problems.

In essence, electrostatic coating powder coatings should pay attention to the following several parameters, in order to ensure the smooth construction of electrostatic spraying process, to obtain high-performance coating: First, the particle size of powder coatings, solvent-based coatings using organic solvents as dispersion media, powder coating Using purified compressed air as the dispersion medium, the powder coating is in a dispersed state during spraying and cannot adjust the particle size of the coating. Therefore, the powder size suitable for electrostatic spraying is a very important technical parameter, and the particle size of the powder coating suitable for electrostatic spraying is preferably 10 to Between 90um and >170 mesh, the powder with a particle size of less than 10um is called ultra-fine powder, and it is easy to carry away with the air and cause losses; second, the resistivity and dielectric constant of the powder coating, and the key point in the powder electrostatic spraying process It is the ability of the powder coating particle to accept charge, maintain charge, and charge distribution. More importantly, the uncured powder coating must withstand the mechanical vibration of the transfer mechanism without falling out of powder, actually affecting the powder particle's acceptance of charge and retention. The main factor of the charge is the dielectric constant of the powder coating. The lower the dielectric constant is, the smaller the particle size is. The easier the electricity is, the easier it is to lose the charge. That is, if the powder on the workpiece is not strong enough to absorb the powder, it will fall off. Therefore, if high-dielectric powder coating is used as far as possible, it will greatly increase the electrostatic adsorption force. The coating is more uniform, but the powder coating with high dielectric constant is more difficult to be charged. It is necessary to improve the structure of the electrostatic powder gun and adopt a forced-charged structure with multiple electrodes. The third is the moisture content of the powder and the moisture content of the powder coating itself. Moisture content directly affects the resistivity and dielectric constant of the powder itself. Powders with severe hygroscopic agglomeration will not be electrostatically sprayed. The powder will absorb moisture to a certain extent, which will deteriorate powder flowability and film formation, in addition to affecting its charging performance. The coating film is not smooth or even difficult to adsorb on the workpiece, and there are disadvantages such as coating film bubbles and pinholes. The moisture absorption of the powder coating is not only related to the storage conditions but also related to the degree of purification of the compressed air during spraying, and the condensed water in the compressed air needs to be filtered. The moisture absorber removes the moisture in the air leading to the powder feeder to a minimum, and people often add some help to the powder coating. To enhance the stability of the powder coating, so that in humid air at temperatures up to or 70 ~ 75 ℃ will not agglomerate.

Tests have proved that the performance of epoxy powder-based powder coatings as two major components of the powder electrostatic spraying process cannot be ignored. Attention has been paid to the technical requirements of powder coatings while developing and exploring electrostatic spraying equipment.

Only a lot of common research can achieve the purpose of high quality powder coating. Powder coating should meet the requirements of electrostatic spraying process, and special attention should be paid to technical parameters such as powder particle size, powder resistivity and dielectric constant, powder hygroscopicity, and powder stability, which directly affect the charging efficiency and adsorption power of the powder, and the quality of the coating film. . If the designed electrostatic dust gun has a good charging mechanism and a diffusion mechanism, the quality of the powder coating is still not good and a high quality product is not obtained.