Common problems in thermosetting powder coating construction (1)

Powder coated particles:

The so-called coating particles refer to powder coatings that contain large infusible particles, which still stand on the surface of the film after the coating is cured into a film. We can analyze the source of the particles from the following aspects.

1. The environmental sanitation status of the production workshop: If the workshop is very dusty, on the one hand, it is easy to enter the finished product through the air inlet of the ACM; on the other hand, the finished product is easy to fall into dust before being packaged and sealed.

2. The influence of filler content, particle size and wettability in the formula: filler is an inorganic infusible substance, and if the proportion is too large, the filler cannot be fully wetted and wrapped by the resin. The greater the chance of particle generation; if the proportion is too small, the extrusion The output shearing force is low, it is easy to stay in the tightly matched parts and gel into particles. The thinner the filler is, the easier it is to be wrapped into a film by organic matter. However, although some fillers are very thin, they are mixed with a small amount of large-particle impurities during drying or other production processes, which is also detrimental to the coating.

3. Uneven mixing of ingredients: Although some pigments and fillers are very fine, they are easy to form agglomerates. If they are not sufficiently stirred, the agglomerates are not easy to disperse, and it is difficult for organic resins to wrap them.

4. Equipment cleaning: if the bottom of the batching pot has not been cleaned for a long time, glue will be produced, and the extruder will easily produce residual glue due to the problem of mechanical clearance. For the extruder with direct electric heating, the time required for heating and cooling is very long, and the residue is particularly easy to gel. Especially when the color is adjusted, heating and cooling are usually repeated many times a day, and the problem of gelled particles is more prominent.

5. Iron filings and other metal impurities: Iron filings are mainly introduced in the following ways: raw materials are contained; the abrasion between the bottom of the batching pot and the mixing blade; the abrasion in the extruder, and the extruder with single-screw damping reciprocating motion is the most prominent. The damping nails are easy to wear; the feed screw of the ACM mill is worn; the grading blade in the ACM mill is broken or worn with the cover plate; the abrasion of the impeller of the powder outlet of the ACM mill.

6. The influence of the screening machinery: the screen is broken or the vibrating screen is not firmly fixed, the edge of the screen generates rotating friction and heats to produce gelatinous material.