The manufacture of powder coatings requires the assistance of suitable raw materials – curing agents, synthetic resins, pigments, fillers, and coating additives in reasonable proportions. The proper choice of raw materials will have a significant impact on the performance of the finished powder coating.
The curing agent plays a supporting role in powder coatings’ performance (coating film). In powder coating manufacturing, the curing agent added should be powder or granular. At the same time, the curing agent must be non-toxic and odorless in order to ensure the environmental friendliness of powder coatings. The curing agent should also be colorless so that it will not change the appearance of the powder coating film or have any negative impact on its usage.
The properties and structure of synthetic resins for powder coatings can improve the physical and chemical properties of powder coatings. During the manufacturing process of powder coatings, the melting temperature and decomposition temperature of the added synthetic resin must be effectively controlled. After the powder is sprayed onto the material, the resin needs to be heated above the melting temperature in order for the powder coating to melt into a film. If the melting temperature of the resin is very close to the decomposition temperature, then it will be very difficult to control the heating temperature. Therefore, as a raw material for powder coating, the temperature difference between the melting temperature and the decomposition temperature of the synthetic resin should be large.
The stability of the synthetic resin is also a key consideration. Generally, the over-sprayed powder coating should be recycled. However, some powder coating particles exposed to the air may deteriorate because of moisture and extreme temperature. Therefore, the physical and chemical stability of the synthetic resin must be good.
Pigments and Fillers
The pigments and fillers added in the manufacturing process of powder coatings are highly demanding. They should not be chemically active and will not react with other components in powder coating production. The pigments commonly used in powder coatings are titanium white, iron red, iron black, mica iron oxide, cadmium yellow, carbon black, phthalocyanine blue, phthalocyanine green, ultramarine, etc.
Adding additives can improve the edge coverage of powder coatings and the leveling of the coating film. It should be noted that the selection of additives as raw materials for powder coatings should exclude those used for solvent-based or water-based coatings.
The additives must be solid, which ensures the storage stability of the powder coating. The amount of additives should also be strictly controlled. Excessive amounts can cause damage to the coating film properties. Additives for powder coatings generally include matting agents, film edge coverage improvers, gloss stabilizers, film property modifiers, etc.