Energy-Curable Coatings in the Metal and Coil Industries

When it comes to performance, the quality of the coating formulation is only half of the equation. Coatings must also be cured properly — with strict adherence to the specifications provided by the coatings manufacturer — for optimal protection performance and aesthetics.

Q: How do advanced curing techniques compare to traditional methods?

A: Conventional liquid and powder coatings typically cure with air or heat, but alternative solutions exist that use radiant energy sources to initiate the cross-linking process instead.

Energy-curable technologies, such as ultraviolet (UV) and electron beam (EB) curing, represent a significant advancement in the coating industry. These methods use specific wavelengths of energy to trigger the curing reaction, resulting in faster processing times and improved efficiency since they eliminate the need for substrate heating.

The use of energy-curable coatings for metal not only enhances the longevity and performance of the final product but also aligns with the industry’s push toward more sustainable and energy-efficient production practices.

Q: What are UV and EB energy-curable coatings and how are they used in applications?

A: While the curing mechanism varies between these two coatings, they both convert liquid paints to solids that fully cure and bond with the substrate in seconds to form a hard, durable finish.

Unlike thermal curing, which requires high heat and lengthy curing times, energy curing is performed at or near ambient temperature using photons of light or electrons to polymerize materials onto a substrate. This method, often called cold curing, is attractive to manufacturers that use wood, plastic and other heat-sensitive materials because these substrates can be damaged when exposed to the higher temperatures required to rapidly cure most conventional coatings.

UV formulations are comprised of liquid monomers (small molecules), oligomers (a molecular complex comprised of a few monomer units) and additives with a small percentage of photoinitiators that convert light energy to chemical energy. When UV-curable formulations are exposed to electromagnetic radiation from UV lamps, photochemical processes are initiated that result in the rapid polymerization of the monomers and oligomers.

EB formulations also use liquid monomers, oligomers and additives, but they do not require photoinitiators. These formulations are cured by an EB device, which emits electrons at a controlled rate that rapidly polymerize the monomers and oligomers in the formulation. Like UV coatings, the technology requires no heat source to cure.

Furthermore, these types of coatings are expected to produce changes in coil-centered industries such as building materials, appliances and HVAC. These advancements will raise the bar for more sustainable, energy-efficient, high-performance solutions, including formulations that offer durability for exterior applications and broader gloss ranges.

Q: What are the benefits of UV/EB-curable coatings from a sustainability perspective?

A: Most conventional liquid paints contain solvents that dissolve and disperse ingredients such as pigments, resins and additives. Energy-curable solutions enable manufacturers to use 100% solid content solutions that contain no solvents, which leads to low, or even no, volatile organic compound (VOC) emissions and lower flammability risks.

This class of coatings is also considered to be more energy efficient since curing is almost instantaneous. Less energy is needed for drying from UV lamps or EBs than conventional thermal drying ovens.

Q: What is the outlook or growth trajectory of energy-curable coatings in the coming years? Are there any particular segments you anticipate higher adoption within?

A: Through investments in research and development, including pioneering work done by PPG and its Duranext portfolio of EB/UV-curable backers, primers, basecoats and clearcoats, these advanced coatings are now available for a broader range of applications and industries.

Historically, the shape or design of the substrate was a major consideration in whether UV/EB technology was an option, as it was more suitable for flat, linear shapes. Today, new curing formulations, equipment and processes are making the technology more applicable for complex 3D shapes, creating new opportunities in industries such as automotive and general finishing.

Interest among coil applicators is growing primarily because of energy-efficiency advantages, low VOC content and a lower carbon footprint via the elimination of high-temperature, gas-fired curing ovens. With energy curing, manufacturers of coil-coated products can expect to lower their processing costs significantly.