Rad-cured plastic coatings move up acceptance ladder

Better, faster, and cleaner may sound like the selling points of a new car, but these words are often used to describe radiation curing. Consequently, the technology is gaining acceptance in the plastics industry and is expected to grow significantly over the next five years, according to RadTech International North America.

"UV curing is a ''cool'' process that can be used on heat-sensitive substrates such as plastics," says David Harbourne, president of Fusion UV Systems Inc. (Gaithersburg, MD), a supplier of UV curing systems and services. "Secondary reasons include speed of process and production efficiency gains."

Radiation curing remains a small application for the industry, used on about 10% of plastic parts produced in the U.S. Nonetheless, the use of the technology grew by 16% in 2002 and double-digit growth is forecast through 2008, according to RadTech, a trade association that promotes the technology.

"There''s definitely intense interest and developments taking place within the last year and a half," says Jim Kassner, co-chairman of RadTech''s Plastics Focus Group and VP of Bayer Polymers, Pittsburgh. "I''m not sure how much of that potential is going to come to fruition. But even if a small percentage of it does, there''s going to be fairly large growth."

Radiation-cured plastic coatings are used in myriad applications, including flooring, eyeglasses, CDs and DVDs, credit cards, cosmetic packaging, flexible film, cell phone covers, automotive lenses, reflectors, and trim. Automotive is one of the fastest growing uses for UV/EB, RadTech officials say, as carmakers and Tier 1 component suppliers show increasing interest in the technologies to achieve scratch/mar-resistant coatings with faster processing, and lower energy and floor space costs. "Automotive is expected to rapidly gain share," says John K. Braddock, technical marketing manager, UV/EB curing chemicals, Akzo Nobel Resins (New Brunswick, NJ). "The primary end users are printers and suppliers to the automotive companies."

Two of the most publicized forms of radiation curing are ultraviolet light (UV) and electron beam (EB), or visible light, used to polymerize a combination of monomers and oligomers onto a substrate. UV and EB material may be formulated into a plastic coating or other product. The spectrum of light in a UV lamp and the focused electrons in EB curing interact with specially formulated chemistries to cure plastic coatings.

Radiation-cured plastic parts offer many advantages over competitive technologies, such as in-mold coating. According to industry members, this includes elimination of VOCs, rapid manufacturing throughput, energy savings, and outstanding properties. "UV coatings can provide improved functionality [properties] to the finished plastic product," Harbourne says. "A typical example is a very hard coating that has good flexibility. This is often not possible with other types of plastic finishes."

The most commonly used plastics in radiation curing include ABS, polystyrene, nylon, PC, acrylic, PP, and BMC. According to RadTech, before using radiation curable coatings on plastics, the types of plastics and their properties, proper molding parameters, surface conditions, coating choices, application parameters, end-term quality, safety, and handling must be scrutinized before a piece is manufactured. "When coating plastics substrates, the greatest challenge is obtaining consistent adhesion to the substrate," Harbourne notes. "Pre-treatment of the substrate is a significant factor in achieving success."

There are other challenges, such as the high cost of radiation-curable products and the fact that end users are not always willing to try a different technology. "Cost is a factor," acknowledges Latoska N. Price, group leader, undercoats, Akzo Nobel (Troy, MI). "UV-cured coatings tend to be higher in price than conventional solvent-borne [products.]"

Gary Cohen, RadTech''s executive director, says he believes once the industry has a better understanding of the expertise and equipment needed for radiation curing, the time it saves as well as the quality of the products mean it will be widely used.

Greg Valero [email protected]