Powder coatings: “A renewed interest in new technology”
What is the current focus of research and development in powder coatings?
Kevin Biller: After a fairly long drought in research and development in the powder coating industry, we are seeing a renewed interest in new technology. Of course, the large multi-national coatings companies are investing a little more in innovation now; however, some of the most interesting work is coming from advanced material people and research groups. A big push is evident in formulating powder coatings for heat-sensitive substrates and this is nothing new. Resin companies have offered novel binders that help powder formulators create products that melt and cure around 135° C in as little as five minutes.
The coolest technology seems to be emanating from smaller enterprises. Most notable is self-healing technology. Most self-healing coating products have addressed the issue of repairing minor scratches in automotive clearcoats; however, emerging technology not only fixes scratches but bridges gaps in a cured powder coating film. This mechanism has proven to significantly retard the advancement of corrosion. Lab tests indicate that the salt spray resistance of an epoxy powder coating can be improved from around 1500 h to over 3500 h with the incorporation of these additives.
What are the latest developments in lowering curing temperatures of powder coatings?
Powder Coating Research Group
Biller: Powder coating medium density fiberboard is becoming more prevalent because of some hard work by a few select powder manufacturers. One of the major resin companies has repackaged some previously UV-curable binder technology into a low-temperature cure system and has offered it to a handful of key powder producers. The main target is coatings for the furniture and cabinetry of a major household goods supplier. This binder technology is being married with a precision gas catalytic infrared curing process with promising results. The coating is still somewhat textured, which can be an attribute or shortcoming depending on the furniture designer’s perspective.
An exciting new development has emerged on the low temp cure powder front. Scientists at a research institute have developed bio-based polymers that provide excellent UV resistance combined with very good flow and leveling characteristics. These resins have been formulated into powder coatings that cure around 135° C and provide excellent smoothness and appearance.
Which industries have you observed increasing use of powder coatings?
Biller: Europeans have embraced powder coatings for architectural applications for decades, whereas Americans have lagged behind in market penetration. Some of this has been due to the reluctance of liquid paint makers to relinquish their grip on the architectural industry. In reality, the situation is a little more complex than that. European latitudes experience a significantly lower exposure of destructive UV energy than most of the United States. It’s this solar energy that degrades the finishes on building façades, window frames and architectural hardware. For instance the average daily solar radiation in Amsterdam is 2.67 kWh/m2, whereas in Atlanta it is 4.42 kWh/m2 and 5.78 in Phoenix. Because of this difference, higher durability products are required in much of the continental United States. Hence, powders based on fluoropolymer resins are used to conform to AAMA 2605 and Qualicoat Class 3 specifications that capture these regions.
Historically, only liquid coating technologies were used to meet these requirements; however, both thermosetting and thermoplastic fluoropolymer powders are slowly treading into this market space. Resins companies have made solid grade fluoropolymers available to powder coating formulators for over 20 years and, therefore, many powder companies have adequate data to prove compliance with AAMA 2605 and Qualicoat Class 3 specifications. Only in the past few years have architects been specifying fluoropolymer-based powders for high durability building components. This growth is coming at the expense of the liquid paint business and only time will tell as to how widespread the market penetration will be.
To get a comprehensive overview on powder coatings the 3rd revised edition of Powder Coatings – Chemistry and Technology is the right reference book. It will provide you with an insight into the key aspects and theories behind the production, properties and application of powder coatings.