Examples of the colors possible with free-radical 100% UV solids coatings.

When Roy Krohn sought to develop an ultraviolet (UV) curable conductive ink, he knew that he was ahead of his time. He just didn't know how far. Today the founder of Allied PhotoChemical, Inc. is starting to truly grasp just how much the entire UV industry has evolved since the company's founding in 1996.

Over the last few decades, regulatory, environmental and safety issues placed a myriad of restrictions on where, what, how, when, and who can manufacture and apply conventional solvent-based inks and coatings. While the early UV hybrid (thermal and UV) cationic cure systems offered promise, no single technology has been developed to address the variety of finishing needs. In reality, there probably will not ever be a single technological panacea to accomplish this daunting task.

However, recent advances in raw materials, product formulations and manufacturing techniques have enabled the development of several innovative products that address most of the environmental and safety concerns. One of the most significant developments to emerge within the last few years is the true 100% UV curable solids product pioneered by Krohn. With advantages such as improved economics, a broad range of colors and effects, compatibility with a variety of substrates and an environmentally friendly approach, the 100% UV curable solids product is opening new markets for today's finishing professionals.

The Pine River e-log uses free-radical 100% UV solids clear coatings.

What is "True 100% UV Curable Solids"?

One hundred percent UV curable solids paint is technically a non-Newtonian fluid, such as an emulsion or colloidal suspension, that consists completely of solids and reacts to polymerize upon exposure to specific spectrum of light. One hundred percent of what is applied as an ink or coating is cured as a print or film. Unlike solvent-based products, where as much as 50% of the product evaporates during the curing process, no evaporative losses are associated with 100% UV curable solids.

For a given 100% UV curable solids product, the physical appearance is similar to its solvent-based counterpart in terms of rheology, processing, application and aesthetics. The free-radical, "true 100% UV curable solids" technology varies from cationic 100% UV solids technologies by cure mechanism and volatile organic compound (VOC) content. Cationic 100% solids systems can possess up to 5% VOC and/or solvents to aid flow and adhesion, and most hybrid UV technologies evolve intermediate or decomposition products such as acetaldehyde, normal vinyl pyridines, vinyl-caprolactum or isocyranates at more stringent temperatures. The free-radical product contains zero VOCs, as well as zero hazardous air pollutants (HAPs) and zero normal vinyl pyridines (NVPs), even when tested at more stringent conditions, such as a 180°C bake test.

Several key benefits of the free-radical 100% UV solids products include:

  • Improved operating economy
  • Improved finish quality
  • Energy savings
  • Environmental friendliness
  • Easier regulatory compliance

The 100% UV solids coatings provide the e-log with strong weathering abilities and excellent wood preservation.

Economic Advantages

The first step in most polymeric finishing processes is pretreatment. For example, corrugated plastic board printing usually requires a corona or flame pretreatment step. The ability of small amounts of some typical petrochemicals to migrate through the true 100% UV curable solids product prior to cure improves the overall quality with these products. Consequently, true 100% UV curable solids products can potentially eliminate and generally reduce the initial step of pretreatment in the finishing process.

Additionally, no heat is needed to drive cure reactions to produce the final coating. For finishing operations that use solvent-based systems, drying or curing paint is usually the limiting factor to throughput and productivity. While other steps within the process can be accomplished in minutes or even seconds, curing often can take hours, and costs are significant in terms of time, as well as in the expense of floor space for large ovens, long conveyor runs, additional tooling, energy and other associated costs, such as work-in-process. With free-radical 100% UV solids, intense ultraviolet light activates a catalyst for the polymerization (curing) process. Curing occurs almost instantaneously, and the size of the UV oven is not a direct function of system line speed or capacity. As a result, companies using the free-radical 100% UV solids products can reduce conveyor costs, energy consumption and processing time, and can increase throughput without using large amounts of valuable floor space. In one particular analysis, the cost reduction from converting from 100% heating to 100% UV solids resulted in a savings of over $250,000 per year on electric energy alone.

The cost per pound of free-radical 100% UV solids is another important factor. Finishers already familiar with conventional solvent-based paints for metal have been accustomed to prices in the $55-85 per gallon range at 40 to 60% solids. The free-radical 100% UV solids product typically costs in the $70 to $120 per gallon range but can provide a coverage of 1,600 ft2 at 1 mil thickness (dry) - almost twice the coverage of an equivalent solvent-based paint. Additionally, the film thickness of free radical 100% UV solids can usually be reduced while providing the same performance as solvent-based paints. When considering the total process cost savings that can be achieved through increased productivity and reduced energy consumption, the free-radical 100% UV solids product can provide a significant economic advantage.

One application of the opaque color UV coatings is colored conduit for specific electrical code requirements.

Design Flexibility

The first technologies developed using the free-radical 100% UV solids technology were UV conductive inks and UV dielectrics. Today, these products are being used on membrane switches, batteries, medical devices and other products. A 100% UV curable Teflon®-based (type PTFE) dry film lubricant was also developed and has been used in applications ranging from the flutes of tooling bits to lubricants for specific medical products.

The next phase of development was a 100% UV solids clear coating, which has been used in applications ranging from architectural coatings to pre-fabricated wood log cabins. The clear coating also served as a base formulation for opaque color UV coatings, which were introduced in early 2002. Other advances have included unique colors and effects, such as silver inks and electrofluorescents.

While UV technology has been used for a number of years in applications such as clear coats on wood surfaces, automotive headlamps, and CD and DVD coatings, the added design flexibility possible with the free-radical 100% UV solids products is expanding UV technology into more traditional areas of the paint market, such as direct-to-metal and outdoor applications. The products are also being used in some non-traditional areas. For example, Oryon Technologies is using the free-radical 100% UV solids system in its new Elastolite™ flexible E-L display, which has been incorporated into a backpack by Lands' End under the Cool Blue™ trademark. The technology can be seen from 1,000 feet away and is targeted at kids walking to school during dawn or dusk. Other innovative applications based on the free-radical 100% UV solids system continue to be developed.

Lands' End's Cool Blue™ backpack uses Oryon Technologies' Elastolite™ flexible E-L display, which is based on the free-radical 100% UV solids system.

Expanding the UV Market

In addition to the growing capabilities of UV paint, several key global drivers are expanding the UV market. These drivers can be summed up by a concept that Allied PhotoChemical refers to as Roie - Return on investment and the environment. To remain competitive in today's market, line speeds must increase, while coating cure times must decrease. The amount of floor space required for the finishing process, along with the amount of work-in-process, must continually become smaller, and energy consumption must be reduced. Additionally, today's processes should release no VOCs, HAPs or NVPs, and should have minimal reporting requirements. Free-radical 100% UV solids systems can help finishing professionals achieve these goals.