Using a powder coating on products made from wood has been successfully accomplished for over 20 years. However, many people may not be aware that powder coatings have been used on a variety of wooden products such as toys, furniture, cabinets, grill handles, and other items. While the primary application, then and today, is applying powder coatings onto products made from engineered wood such as medium density fiberboard (MDF), other wood products like hardwoods and particleboard can now also take advantage of the benefits of powder coatings. Numerous technological improvements in materials and process equipment are bringing new opportunities and excitement into the marketplace.
The Root of the Matter While “wood” is a general term used by many people to describe all kinds of wood or wood-like products, all are non-conductive and sensitive to heat and moisture. Therefore, the premise of using electrostatic energy and heat to apply the powder may seem unrealistic. However, powder coatings have been applied for many years using these methods, producing long-lasting finishes with excellent appearance qualities.
Traditionally, wood products would be finished with one of the following: vinyl, melamine, paper laminate, or liquid coating. Regardless, powder coatings have proven to be an attractive coating alternative offering economical, ecological and performance advantages. The application of powder coatings onto MDF provides a seamless finish to curvilinear shapes, rounded or ogee edges, concave and convex surfaces, cabinet doors, drawers and multiple sides simultaneously.
Early adopters of using powder coatings on wood found major advantages in coating performance, operational costs, and environmental friendliness. For example, being able to design without limits is a big factor. Powder coatings help users avoid having to design around the limitations of laminates or pay the cost of liquid paint coatings.
Reduction in labor and simplified application processes are achieved by using powder coatings. Gone are the days of excessive sanding, priming and sealing for paint, or even the gluing and edge banding of laminates. Additionally, volatile solvents traditionally required by both are eliminated. Users are able to hang their products from an overhead conveyor and coat all sides of the object at once. No drying time or awkward handling is required.
Over the last decade, powder coatings have proven to be an excellent coating method for wood products offering advantages in economy, excellence of finish, and ecology (see Table 1). Considering the high cost of energy, labor and materials, users are looking to powder coatings as a more cost-effective and less wasteful process. Furthermore, consumers and other end-users are demanding newer designs and appearances, and higher quality and durable finishes, all of which fit with the value proposition offered when choosing to use powder coatings. As for our environment, many companies are faced with progressively more stringent regulations that are being aggressively enforced in an effort to control air pollution and hazardous waste disposal. Powder coatings evade these obstacles as an ecologically-friendly coating choice.
Branching Out for the Future
The growth within this market segment has been spurred by several important innovations. To get a better understanding of the innovation, I spoke with several leading companies within the industry. Sjoerd de Jong and Bob Cregg of DSM Coating Resins, Scott Persyn of IGP North America LLC, Jeno Muthiah of Alpha Coating Technologies, Lee McWhorter and Gerald Plush of Heraeus Noblelight America LLC, and Troy Greenberg of RedLine Garagegear.
From a materials perspective, Sjoerd de Jong, Scott Persyn, and Jeno Muthiah all spoke about the advancements in raw materials and new powder formulations that are offering lower curing temperatures, faster curing time, and more flexibility within the coating process. As stated by Sjoerd de Jong, “Our new technology is designed to work at 265 degrees Fahrenheit for three minutes for curing in a single layer coating.” He continued, “Our expectations are to continue lowering the curing temperature and make the [materials cure] even faster.” All three materials suppliers are working on formulations that will continue to push the envelope for lower curing temperatures of 250 degrees Fahrenheit and lower.
Today there are more choices for wood substrates, both engineered wood and hardwoods, as well as more choices for colors, textures and gloss for those who want to consider powder coatings. Scott Persyn adds, “People are more willing to look at [powder coatings] and embrace [powder coatings]…with the lower temperature and the shorter cure cycles, the [substrates] we can coat such as MDF, particle board, or natural wood have opened up and are not restricted.” Echoing these statements is Jeno Muthiah: “Users should be aware that no one chemistry will meet all the requirements, and formulators continue to expand our products by offering more powder formulations meeting a broader range of end-use performance requirements.”
Meanwhile, technological advancements in process equipment have also led to greater success. The use of infrared curing technology, both electric and gas catalytic, is working in concert with the newer materials to produce high quality finishes with less energy and lower operational cost. Referring to the use of IR curing technology, Scott Persyn commented, “Edge-cracking and outgassing are virtually eliminated.” Lee McWhorter added, “The curing technology available today is very functional for all sizes of businesses, and very affordable for even small-to-medium businesses considering a conversion to using powder coatings.”
Likewise, the spray application and recovery equipment have transformed in several areas, most notably in powder delivery and electrostatic control technology. Each advancement offers greater accuracy and repeatability in uniformly applying the correct amount of powder onto the desired object. The use of a counter-electrostatic device in conjunction with the traditional electrostatic powder coating gun is an innovation that controls the coating process to avoid excessive coating thickness on the edges of the product, thus avoiding outgassing and “orange peel” due to heavily coated edges. Advancements in production application equipment have also yielded greater flexibility, efficiency and speed as it relates to changing between powder coatings with different color, texture and/or gloss. Users of powder coatings can have production line color changes in one to five minutes for spray-to-waste processes, and as little as ten to fifteen minutes for processes choosing to reclaim and reuse the over-sprayed powder.
In speaking with Troy Greenberg, owner of RedLine Garagegear, who has been using powder coatings on his wood products for more than a decade, he notes he has seen and experienced numerous positive changes in the industry. “The coating performance we get from the powder coated finish on our products is outstanding. Our garage products are exposed to a wide range of environmental conditions, both hot and cold, humid and dry, as well as physical abuse and a variety of chemicals. Our powder coated finish offers great protection, colorfastness and holds up over time. This gives our customers a great value!”
Value is a critical part of the equation when considering switching or adding powder coatings as a finishing alternative. Because powder coatings offer many advantages over other finishes, companies will find an excellent return on their investment. New materials offered today can greatly expand the market acceptance of powder coatings. Coupled with new equipment technologies making application more operationally efficient and simple, it is easy to see how the wood market or “the old tree” is sprouting new growth!
How is Wood Powder Coated?
Objects made of MDF or hardwood are cut into the desired shape. This process may include routing or profiling the surfaces and edges, as well as some light sanding. Using compressed air or a vacuum, wood fibers are removed to ensure defect-free finishes. The objects are then arranged on a fixture (aka hanger) that allows for transportation to and from the pre-heat and/ or curing oven and coating booth. For objects made of MDF, they first proceed to the preheat oven where the surface of the object is heated to a specific temperature and then quickly transported to the coating area. Objects made from hardwood would bypass this step and go directly to the coating area.
Once in the powder coating booth, the spray guns atomize the powder and electrostatically charge the powder particles, while directing them towards the product. The powder coating is applied until the required film thickness for coating performance is achieved. Once coated, the object is transported into a curing oven, where the final heating step is performed. The powder that has been applied is now held on the surface until it is completely melted and cured into a smooth continuous coating. Upon cooling enough to touch, the object is immediately ready for further assembly or packaging for shipping.
Advantages of Powder Coating:
- Seamless coating.
- Suitable for curvilinear shapes and surfaces.
- Less labor required.
- Virtually free of volatile organic compounds (VOC).
- Fast cure time.
- Quicker post-cure handling.
- High process efficiency.
- More productivity.
- Greater yield rates.
- Lower rejects.
- Reduced carbon footprint.
- Excellence of finish appearance (colors, gloss, texture).
- Clears and tinted clears.
- Usable on MDF, hardwood, and particle board.
Industry Contributors:
Sjoerd de Jong, DSM Coating Resins
Bob Cregg, DSM Coating Resins
Scott Persyn, IGP North America, LLC
Lee McWhorter, Heraeus Noblelight America, LLC
Gerald Plush, Heraeus Noblelight America, LLC
Jeno Muthiah, Alpha Coating Technologies
Troy Greenberg, RedLine Garagegear
- by Jeff Hale, director of marketing for Gema USA Inc.