Technology Transfer Network - Air Toxics Web Site
UV-Cured Wood Coatings
Installation of a UV-cured coating line typically requires a large capital investment, often millions of dollars. This large initial cost limits many smaller facilities from implementing a UV-cured coating system. However, once the system is in place, it is generally a very cost-effective method of production because transfer efficiency can be up to 100 percent and the lines are typically automated, requiring few operators.
The finishing line can be a flat line or a spray line. Coatings applied on a flat line, using roll coaters or curtain coaters, can contain up to 100 percent solids (meaning that all of the coating components cure to form the final film) and produce little or no emissions. Sprayable UV-cured coatings often contain water or solvent to reduce the viscosity of the coating for easier application. Spray booths for UV-curable coatings generally are enclosed and automated.
Another advantage of UV coating lines is the decrease in the amount of floor space required. A curing oven follows the coating applicator and contains UV lamps that cure the coating in a matter of seconds. Since the cure time is so short, pieces can be assembled and stacked immediately after they are coated. Additional floor space for large ovens or areas for drying the product is not needed with this type of coating system.
Equipment used to apply UV-curable coatings can be difficult to clean. The coatings typically are viscous and sticky. In addition, they must be kept away from direct light to prevent them from curing in or on the equipment. Many facilities allow the coating to remain in the supply lines and coating reservoirs when not in use, and they cover the equipment to prevent the coating from curing. This practice reduces cleaning solvent usage and cleaning emissions.
The appearance of a UV-cured finish is typically aesthetically pleasing and very durable. High-gloss finishes can be easily achieved by applying either multiple coats or thicker coats. The clarity and depth of the finish is comparable to that of traditional nitrocellulose-based coatings.
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