Future Trends

The success of conventional powder coatings is the result of their excellent properties and many economic and environmental advantages over traditional solvent based paints. Many of the disadvantages to the use of powders that had existed (see Table 1) have been eliminated or minimized through formulation and equipment development. These developments will help to assure that powder coatings market will continue to grow at an impressive pace.

New resin systems allow powder to meet the end-user's specification for almost any product. Many of these coatings can be cured at temperatures as low as 121°C. The advent of low curing temperature systems, such as IR cured powders, has significantly opened up the market to heat sensitive substrates such as wood, plastics, and assembled components with heat sensitive details. The coating of metal substrates also benefits from this technology, with lower energy and investment costs, shorter curing times, and higher lines speeds.

Powder coatings are also being developed for high temperature applications. Silicone-based powder coatings are often used on products that must retain their appearance, adhesion, and surface protection even after prolonged exposures to high heat (up to 538°C). Some of these products include gas and charcoal grills, fireplace inserts, engine exhaust components, and light fixtures.

Significant advancements are also being made in the weatherability of powders for use in automotive and architectural applications. Polyester TGIC based powders, for example, have been used on outdoor stadium seating and other exterior applications that were previously susceptible to degradation from UV. The use of TGIC, which has been labeled as toxic in certain regions, is now being replaced by other binders. Clear, corrosion resistant, and durable powder coatings are used for a wide range of applications including automotive parts. Auto manufacturers such as BMW and Volvo are using powder clearcoats over automotive exterior basecoats.

Equipment development will also contribute to the future advancement of powder coatings. Powder utilization rates of 95% or higher are common. This compares with a 30-80% utilization rate for most other spray coating processes. Advances in infrared and ultraviolet curing technologies are allowing increased production speed in powder coating facilities. IR ovens can sometimes cure a part in as little as 30 secs, and UV curing can be accomplished in a matter of seconds.

Thin films, 1-3 mils (25-75 µm), can be applied in a wide range of colors, glosses, and textures and ultra thin film, 0.8-1.2 mils (20 - 30 µm) powders are currently being developed. These powders offer better penetration into recesses, more film thickness control, and more effective first pass transfer efficiency.

Color and surface texture variety is almost limitless with new powder coating formulations. Properly designed powder systems can now change colors in minutes. High production powder systems apply over 20 different colors, with several color changes per day.

Coil coating applications for powder are also being developed. Coil coating is the process of coating one or both sides of flat metal sheets or strips on a continuous production line. Most powder coating facilities are laid-out in a vertical configuration. However, newly designed horizontal powder coating booths are enabling powder to compete more effectively in the extrusion and pultrusion finishing markets.

Radically different methods of application are also likely to open future markets. In-mold powder coating processes have been developed in which the powder coating material is sprayed onto a heated mold cavity before the molding cycle begins. During the molding operation, the powder coating chemically bonds to the molding compound and produces a product with a coating that is chip and impact proof. Processes have been developed for applying thermoplastic powder in the field, provided that the substrate is clean and can be preheated properly. Bridge support columns and steel sidewalks have been coated successfully. Also, pipe joints that are originally coated in the factory but must be welded in the field can be recoated with powder, thereby providing a continuous, corrosion resistant coating.

The impressive list of developments that are listed above do not solve all of the possible shortcomings associated with powder coating. Table 5 lists several material development challenges that remain for the powder coating industry. Solutions to these challenges would further open new finishing areas to powder coating economics.