The flow of bed original and spring
Fluidized bed coating process is one of the early implementation methods in powder coating. China began to study thermosetting epoxy powder by fluidized bed coating early in the early 60s, and achieved success. At that time, it was mainly used in mechanical and electrical products, such as insulation coating and anticorrosion coating for motor. In recent years, with the development of powder and coating technology, it has been widely used in household appliances, daily necessities, steel structural parts and so on. The application of raw materials also developed from the original epoxy powder coating to nylon, polyester, polyethylene, polyvinyl chloride and other varieties of powder.
The characteristics of fluidized bed
The method of fluidized bed coating process is to inhale air or some kind of inert gas to the bottom of the container to make the powder coating move up to the "fluidized state". The air passes through the porous air permeable plate and becomes a uniform distribution of fine airflow that makes the powder turn over, and each powder rises first and then drops. The property of this liquid powder is like a liquid. The object placed in it is like a submerged liquid, surrounded by a powder of fluidization. The fluidization of the powder is still very different from that of the liquid. For example, when a tube is placed horizontally into the liquid, its inner wall will instantly be wetted, but in the fluidized powder, the powder in the lumen will become stationary. This is because the action of the particle is mainly in the upper and lower directions, and the movement in the horizontal direction is very little.
The fluidized bed coating principle
The working principle of fluidized bed by way of coating with fine powder uniform air flow, the powder particles stirred fluidization. When the air and powder are balanced, the height of the interface is maintained. When the coated workpiece is preheated, it is put into the powder, that is, the uniform coating can be obtained, and the film is heated and solidified at the end.
Fluidized bed is second stage solid flow theory, is more complicated and difficult to control the stage. The process of solid state flow state is divided into three stages: fixed bed stage, fluidized bed stage, and airflow transport stage. It is very important to know the characteristics and mutual relations of these three stages in a rational way for mastering the technology of fluidized bed coating.
After fluidized bed coating, though the powder is melted and covered on the surface of the workpiece, the process of heating and plasticization must be done to complete the whole fluidized bed painting process. The heating and plasticizing process is beneficial to the further leveling of the powder. This can make the film have better mechanical strength, electrical performance, surface leveling and gloss performance.