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Ask the Expert: Innovations on the Horizon for Decorative Coatings

A resource sponsored by SPE’s Decorating & Assembly Division

by Karen Kukla, account manager

AkzoNobel

Photo courtesy of AkzoNobel

Decorative coatings, particularly UV coatings and applications, have undergone significant changes in recent years. Everything from environmental concerns to customer demands for higher quality at lower costs have had an impact on how the decorating industry has evolved over time – and will continue to do so. Plastics Decorating sat down with Karen Kukla, AkzoNobel’s account manager for specialty coatings, to discuss some of the challenges and innovations facing the industry.

What changes have you witnessed in decorative coatings in the past few years, and how have they impacted the industry?

By far, the biggest change in decorative coatings over the past few years has come as a result of manufacturers trying to reduce their carbon footprint. There has been a big push to develop waterborne coatings with the same performance as their solvent-borne counterparts. While waterborne coatings still contain a percentage of volatile organic compounds (VOCs), overall, they tend to have lower levels of VOCs than other coatings. In addition, waterborne coatings tend to have shorter shelf lives, fewer options for on-site adjustments for application optimization and are highly sensitive to temperature/humidity conditions.

Furthermore, waterborne coatings also present their own set of challenges regarding application techniques and rheology control, especially regarding metallic flake coatings. Changes in temperature and humidity often will lead to yield fluctuations. As a result, most manufacturers have found that, to produce parts efficiently with waterborne coatings, climate-controlled facilities are highly recommended to keep fluctuations to a minimum. Many manufacturing facilities can be up to tens of thousands of square feet in size, so the cost associated with implementing climate control can become a very real concern – because of this, many have tried to lessen this cost by sealing off the paint line and only requiring climate control in this area.

Another change, mainly in the automotive area, is the use of new and different plastic substrates, as well as aluminum and new alloys. With each new substrate, however, comes new obstacles. Carbon fiber is all the rage right now, yet processing this substrate is difficult, as the film thickness must be built up in several coats to obtain full UV protection and wet-sanded in between each layer for adhesion. Pin-holing is very much an issue. Aluminum is also a preferred choice right now due to weight factor; however, coatings must be designed specifically for different grades of aluminum to obtain full corrosion resistance.

Finally, another important aspect regarding industry changes has been the drive for renewable and sustainable coatings. AkzoNobel’s global company goal is to utilize renewable raw materials for multiple markets wherever possible, including automotive, to continue to strive to make this world a better place through reduction in overall waste. As a result of its efforts, AkzoNobel has been ranked in the top two in the Dow Jones Sustainable Index for the past several years.

As the market for UV-curable paints continues to grow, what advantages do they offer, and what are the best applications for these coatings?

UV-curable paints offer many advantages, including the ability to deliver optimal scratch and mar resistance at room temperature at a fraction of the time, meaning the paints do not have to reach temperatures up to 300°F. This allows for optimal paint line footprints, greatly improved energy efficiencies and higher throughput numbers. Additionally, rejections due to dirt are vastly reduced as a result of rapid cure times. The material is sealed over quickly, such that dirt particles in flash zones and ovens have a much lesser chance of adhering to the parts prior to cross-linking.

Given that UV light is what initiates the cross-linking process, the best applications for UV-cured coating are part configurations that allow for direct line-of-sight to all coated areas of the part. On the other hand, if area footprint and energy costs are not the main focus – but rather superior scratch and mar resistance – parts with intricate, shaded areas that would not be directly exposed to the UV light would benefit from a dual cure system in which UV curing is paired with a traditional bake to fully cure the shaded areas not exposed to the UV light.

UV formulations are designed for many different light intensities; however, higher intensity light provides more options for formulation. High-intensity light formulations are best utilized in industrial areas where the light source is isolated due to potential exposure. For this reason, UV formulations designed for smaller systems and body shops utilize formulations designed for cures with lower light intensities.

How has application equipment for painting/coating evolved to keep up with advances in the industry?

As the automotive industry continues to focus on higher quality at lower costs, paint suppliers in conjunction with automation/robotics suppliers have had to get creative in finding new ways to achieve not only equal but better results than in the past and do so more efficiently.

Two primary examples of this effort come to mind. The first is the development of bells and micro-bells in the robotic sector, both for solvent and water technologies. Bells were developed to apply paint electrostatically with a much higher transfer efficiency than traditional guns, obtaining transfer efficiencies up into the 90s in percentage compared to traditional and HVLP guns, which range anywhere from 50 to 65 percent efficiency. When bells were first introduced, they were either stationary or on simple reciprocators, giving them a very small operating window. Now, bells and micro-bells are on robotic arms, giving them almost endless possibilities for opening up process windows and zeroing in on intricate part configurations.

It is important to note that there are significant differences in the qualities of paint applied with a traditional gun and paint applied with a bell. Bells tend to bury aluminum and mica flake, resulting in a much darker, richer final color than the same paint applied with a gun. Because of this, formulations designed for a full bell application must be designed with significantly higher flake levels, which could potentially drive the costs on the material higher.

The second example is the implementation of a wet-on-wet process from primer to clear to reduce energy costs, overall plant space footprint and CO2 emissions and to increase the number of units per shift. Formulation for a wet-on-wet process requires changes in resin composition, as well as solvent packages to ensure the final product meets the same specifications as traditionally processed materials.

What innovations in painting/coatings can consumers expect to see in the near future?

Paint companies are in constant competition to not only come out with new innovations in coatings but to develop the innovation that will take the industry by storm and make their name as well known as that of any of the global auto companies. Today there are UV-cured coatings, vacuum metallized coatings, films and the list goes on – but some of the coatings coming in the very near future will be quite amazing.

Color was, is and will forever be a driver in the innovation process as new pigments, micas and aluminums are always being designed and combined to create that new, trendy look. Candy colors, which are a base/mid-coat/clearcoat system, have really been taking off recently. They make it possible to design new and unique colors through utilizing nano-pigments and dyes in the mid-layer of this process. Nano-pigments and dyes make it possible for this mid-layer to be transparent while still providing depth and color variances not obtainable through traditional base/clear systems.

In addition to new and eye-catching colors every year, development chemists are forever researching ways to enhance the coatings of today to serve multiple uses for the future beyond just looks and basic protection. Imagine this common scenario: a shopping cart slides along the side of a car, leaving a long scratch the length of the door. This would instantly take the joy out of what might have been a fabulous day – that is, unless, by the time the driver arrived back home, the scratch was gone. Self-healing paint – coatings containing new compositions and compounds – are currently being developed to accomplish this. The UV rays from the sun react with these compounds, and the coating actually heals itself, leaving no memory of the scratch.

Or, who has ever had a car with beautiful, high-gloss, black interior parts? Most consumers love this look – until they find themselves spending 90 percent of their time trying to wipe away pesky fingerprints. What if there was a high-gloss black that was fingerprint-proof? Or a radio touchscreen? Well, customers should keep their eyes peeled, as that is on the way as well. Formulations utilizing ultra-low surface energies are currently in development to all but eliminate fingerprints as well as reflection and glare.

And, how many people search for the shadiest spot to park their cars in the summertime because they know if they don't, they’ll be getting into an oven at the end of the day? Chemists and designers are working on formulations incorporating reflective pigments that would cause the sun’s UV rays to reflect rather than absorb into the coatings, resulting in a much more comfortable experience for everyone.

Karen Kukla has been in the automotive paint industry for 24 years. She studied chemistry and natural science at Eastern Michigan University and has a BA in professional business studies from Davenport University. Her career began in technical service and formulation of acrylic/melamine basecoat/clearcoat systems for steel applications, followed by years on the front lines as a lead technical service rep. She is now an account manager with AkzoNobel, focusing on technical sales. AkzoNobel is a global paint company, focusing on decorative paints, performance coatings and specialty chemicals. Kukla can be contacted by email at karen.kukla@akzonobel.com.