Powder Coatings are a blend of resins, curing agents and pigments, which are melt-mixed (extruded) and pulverized into finely divided particles. They are totally solvent free.
Typically applied to metal products by electrostatic spray, the coated item is then heated and the powder melts into a smooth, continuous and encapsulating film. When thermosetting resins are used, the coating changes chemically (crosslinking) during cure, resulting in a decorative / functional finish with superior performance characteristics.
There are two basic classifications of powder coating materials. They are "thermoplastic" and "thermoset" powders.
Thermoplastic powders are generally applied to a surface that has been pre-heated to a temperature significantly higher than the melting point of the powder. It melts and flows when heat is applied but continues to have the same chemical composition when it solidifies on cooling. Nylon powder coating materials are the most commonly used thermoplastic powders. Thermoplastic coatings are known for their wear and chemical resistance.
Thermoset powders are 100% solvent-less and are generally applied by means of electrostatic spray equipment that provides each powder particle with a small electric charge, which in turn sticks to the earthed substrate. Thermoset powder coating systems offer broad formulation flexibility. They are very durable and are widely used.