Powder coating paint can be divided into two main categories; thermoplastic powder and thermoset polymer. Both types of powder coating paint require heat in order to flow and form a uniform film. Each type of paint has its own unique chemical properties and method of application.
Thermoplastic powder is generally applied with a fluidized bed process. No electrostatic charge is required. This type of paint is usually applied to a part that is heated to a temperature well above the powder’s melting point. The heat causes the powder to melt, adhere to the part and form a scratch-resistant, uniform film of paint. Unlike thermoset polymers, thermoplastic powders remain chemically unchanged throughout the process, which means that they can be re-melted and reused.
Polyester-based thermoset polymers are often used on items that are continuously exposed to the elements.
Thermoset powder coating paint differs from thermoplastic powder in that it undergoes a chemical change, called crosslinking, as it cures. After it has been heat cured, this type of finish cannot be re-melted or reused. Thermosetting polymers tend to be more durable than thermoplastics and offer a wider variety of finishes.
There are four categories of thermoset powders that are based on the type of resin used as their base. The four basic resins used for thermoset powders are epoxy, acrylic, polyester and fluoropolymer. In manufacturing thermoset polymers, the resins typically are first ground into a fine powder to make them suitable for spray gun application.
Epoxy-based powder coating is resistant to both impact and scratching. Its inability to stand up to bad weather and ultraviolet rays generally limits its use to indoor applications. Epoxy powder coating paint is generally used for coating home appliances, automotive underbody parts and industrial equipment. It also is a popular choice for painting metal furniture, such as bed frames and futons.