Selection of Raw Materials for Thermosetting Powder Coatings

Thermosetting powder coating is composed of resin, curing agent, pigment, filler and other additives. It is very important to choose raw materials, which has little influence on the coating quality and film performance. How to choose the resin?

The structure and properties of resin are the main factors to determine the quality of powder coatings and film properties. The following basic technical requirements should be met
1) The resin used for thermosetting powder coatings must contain active functional groups to form a network structure during baking.
2) In the process of powder coating construction, if the synthesis temperature of resin is very close to the melting temperature, it is very difficult to control the heating temperature. Therefore, the temperature difference between the melting temperature and the synthesis temperature of the resin should be large.
3) The melt viscosity of the resin is low and the range is narrow. When it reaches the temperature above the melting point, the viscosity will drop rapidly. In this way, a better leveling film can be obtained by electrostatic spraying and fluidized bed dip coating.

4) The over sprayed coating in powder coating can be recycled. However, some powder particles contact with the air for a long time and change due to the influence of moisture and temperature, so the physical and chemical stability of the resin is better.
5) The consumption of powder coatings generally adopts mechanical crushing method, which can obtain the average particle size distribution and particle shape. The resin should have higher glass transition temperature and melting point for better comminution.
6) Resin plays a key role in the adhesion of powder coatings. If the separation of the coating is good, there is no need to apply primer, and the durability of the film is good. Thermoplastic resin adhesion is poor, so to precoat primer. The color of resin is light, transparent and nontoxic.