Coatings have been UV cured in industrial settings since the 1960s. The graphics industry was one of the first to adopt this technology, with a high-gloss coating on cards. Today, there are numerous industrial applications that utilize UV curing as the method of drying or polymerizing the coatings or inks, including the wood coating industry.
The wood coating industry initially embraced UV-curing technology as a way to increase both productivity and performance, and more recently as a means to save energy and meet environmental regulations. Initially, all applications were based on 100% solids UV-curable products, coating mainly flat panels by roller coater.
During the 1990s, UV-curable polyurethane dispersions in water (UV-PUD) were developed. PVC floor coating was the first industrial application. The flexibility, adhesion and stain resistance of these coatings made this new technology very successful. The low viscosity and the very low VOC of these dispersions also made them very attractive for spray, curtain and vacuum applications onto wood.
In recent years, commercial UV curing has moved out of the factory and into the field, with numerous improvements in UV-curing equipment enabling this transformation. Floor coatings are one of the main applications for field-applied UV-cured coatings. Today, field-applied or on-site floor coatings for wood are in several stages of commercialization.
The benefits of UV-cured field-applied wood coatings are similar to factory-applied wood coatings: increased productivity and performance. In addition, the immediate cure aspect provides (1) an added benefit of quality, since the finish will not be damaged once it is cured, and (2) cost savings to the end user through immediate use.
In this article, the performance of water-based field-applied UV-cured wood floor coatings is compared to that of conventionally cured wood floor coatings. The benefits and detriments of each curing technology are also reviewed. Additionally, several UV-cure processing and formulating variables are evaluated regarding their effect on coating performance.