How to Choose Thermosetting Powder Coating

Thermosetting powder coatings are composed of resins, curing agents, pigments, fillers and other additives. It is very important to choose these raw materials, because it has a significant impact on the quality of the coating and the performance of the film.

1. The choice of resin: The structure and performance of the resin are the main factors that determine the quality and film performance of the powder coating. The following basic technical requirements should be met:
1) Resins for thermosetting powder coatings must contain active functional groups to ensure the formation of a network structure when baking to form a film.
2) During the construction of thermosetting powder coatings, if the decomposition temperature of the resin is close to the melting temperature, it is very difficult to control the heating temperature. Therefore, the temperature difference between the melting temperature and the decomposition temperature of the resin is required to be large.
3) The melt viscosity of the resin is required to be low and narrow. When the temperature is above the melting point, the viscosity should drop rapidly. In this way, powder coating electrostatic spraying, fluidized bed dip coating and other methods can be coated on the substrate to obtain a coating film with good leveling properties.
4) The oversprayed paint in powder paint can be recycled and reused. However, some powder particles have been in contact with air for a long time, and they change due to the influence of moisture and temperature, so the physical and chemical stability of the resin is better.
5) The adhesion of powder coatings depends on the resin to play a key role. If the adhesion of the coated object is good, there is no need to apply primer, and the durability of the coating film is also good. The adhesion of thermoplastic resin is poor, so primer should be pre-coated.
6) The color of the resin is required to be light, transparent and non-toxic.
2. The choice of curing agent
Curing agent is an important factor in resin modification and film formation, and it directly affects the quality and film performance of powder coatings. Therefore, it is very important to select a suitable curing agent, it should have the following conditions:
1) It is in powder, granular or flake form at room temperature.
2) It has chemical and physical stability: no chemical reaction with resin or other components during production or storage, no agglomeration or agglomeration. When spraying, it can be cured quickly after baking to a given temperature, and the coating film is flat, smooth and plump.
3) The curing agent should be non-toxic (low toxicity) and non-irritating. It is better not to release peculiar smell and harmful odor during the baking process.
4) The curing agent is colorless and can not color the coating film and affect the appearance of the coating film.
3. The choice of pigments
The pigments and fillers in the powder coating components cannot chemically react with other components during the production and storage process, and have good stability to heat and light. Pigments for powder coatings should meet the following conditions:
1) It can be uniformly dispersed in the resin; 2) The thermal stability of the coating film is good when it is cured. 3) Good light stability, chemical resistance and solvent resistance. 4) No bleeding, no frost and no migration in the coating film. 5) The color does not change due to other components. 6) Does not promote resin aging. 7) In the hot melt state of the resin, the dispersibility is good. 8) Good tinting power and hiding power.

4. Filler selection: Adding fillers to the powder coating formulation also has a modification effect, such as adjusting the flatness, gloss and physical and mechanical properties of the coating film. The selection requirements for fillers are:
1) It is easy to disperse in the formula components and has good fluidity. 2) It does not contain foreign matter and impurities that affect the quality of the coating film. 3) No harmful chemical reaction with other components. 4) Does not reduce the physical and mechanical properties of the coating film. 5) Does not reduce the physical and mechanical properties of the coating film.