How to select a proper powder for your products
Choice of resin system, hardener, and pigment is just the beginning in selection the properties that one may require of the finish. Control of gloss, smoothness, flow rate, cure rate, ultra violet resistance, chemical resistance, heat resistance, flexibility, adhesion, corrosion resistance, exterior durability, ability to be reclaimed and reused, total first time transfer efficiency, and more, are some of the factors that must be considered when any new material is manufactured.
Thermosetting powder coating are classified into five basic chemical groups Epoxy, Epoxy-polyester,commonly referred to as Hybird, Polyester Urethanes, Polyester-TGIC, and Acrylic.
Urethane-Polyester coatings are best utilized in thin film (1.0-3.0 mil) applications. Above this range, Urethanes may tend to haze, outgas or pinhole due to the small amount of volatiles coming off the curing agent in the system. However, if thickness parameters are controlled, Urethanes provide a tough, durable film surface with excellent surface smoothness, flexibility, and exterior weathering characteristics.
Epoxy series powders are noted for their excellent chemical and corrosion resistance. These coatings have a wide range of formulation latitude in that they can be customized to meet thick film functional or thin film decorative end uses. Known as being a flexible but tough coating, the only drawback to Epoxies is their lack of ultra violet tolerance.
Epoxy Polyester chemistries, or Hybrid, exhibit some of the best transfer efficiencies of all thermoset powder coatings.In some cases, they may be as flexible as Epoxy types, but lose some hardness and chemical resistance because of the Polyester component.
Acrylics represent the smallest share of the thermoset market possibly because of the number of resin suppliers and acrylic powder producers, and the incompatibility problems sometimes encountered when using these systems interchangeably with the other thermoset chemistries. However, pure Acrylic powders are characterized by excellent film appearance, flexibility, and hardness. They are also classified as weatherable systems.
Polyester TGIC represent the fastest growing area in thermoset technology. This growth may be attributed to the chemistry’s overall performance ratings in physical and chemical properties, application or transfer efficiency, and excellent Ultraviolet resistance. Also, TGIC-Polyesters can be applied at relatively thick films (6+ mils) without volatile entrapment or out-gassing.