Powder coating on MDF: a sustainable future?
Yesterday, Materia was invited to an event hosted by DSM about powder coating. While this technology in itself is not new, as powder coating is used on metal for thirty-some years, it is new to do so on wood. What are the challenges of powder coating on MDF, and why would you even want to use powder coating on wood? Today, Materia explains.
As the name implies, powder coating uses dry powder to coat materials. The main difference between powder coating and conventional liquid paint is that powder coating does not require a solvent to keep the binder and filler parts in a liquid form.
The powder coating is applied using electrostatics. The particles of the powder are drawn to the surface of the material that is to be coated. These particles can easily be wiped off at this stage. To make the coating stick, the powder is cured in an oven, creating a skin.
Why powder coating?
There are several advantages to powder coating. For instance, because powder coating does not have a liquid carrier, you can create thicker coatings without running or sagging.
In addition, this type of coating is generally more environmentally friendly than liquid coatings. Because no carrier fluid evaporates away, the coating process emits few volatile organic compounds (VOCs).
It also has advantages in design freedom, as the powder particles will reach any place, so you can cover objects in nearly any shape.
Powder coating on MDF
Until recently, powder coating was almost only used on metal, as this material is easy to make electrostatic and can handle high temperatures. The particles of powder coating are cured at temperatures reaching as high as 200 degrees Celsius (392 degrees Fahrenheit). Obviously, wood cannot handle such temperatures, nor is it as conductive as metal.
In the past years, companies have struggled with hurdles for powder coating on MDF, such as lowering the curing temperature, aesthetic properties and more. Most importantly, the to be coated material has to be electrostatic, or else the particles will not stick to it.
DSM developed a new technology (a resin, not the powder coating itself) that makes it possible to use powder coating on heat-sensitive surfaces, such as MDF. Using the moisture content in the engineered wood (which has to be about 8 per cent), the material can be made electrostatic enough to attract the particles.
The powder coating can be applied in one layer. A piece of MDF is hung on a rail, so a sample will always have holes in it. The panel then goes through an oven to draw the moisture to the surface and then goes through the coating process, covering the entire panel in one go. Finally, the powder is cured in a ultra-red oven, creating a smooth surface all the way around the coated object. The coating has to cure for 3 minutes at 130 degrees Celsius (266 degrees Fahrenheit) and afterwards needs about 20 minutes to cool off.
The surface of cured powder coating has a matte look and a bit of an orange peel texture. This texture can be polished until it is nearly high-gloss, though it is hard to get it as smooth as high-gloss liquid paint.
Powder coating is stain resistant, scratch resistant, colourfast, and UV-resistant, making it suitable for outside use. Objects coated with powder coating are water-resistant and suitable to be used in wet places, such as bathrooms and kitchens. It is available in transparent or any colour you desire. The coating created by powder coating looks almost as if the material is laminated, but does not leave any gaps in which water and dirt can make their way to the core.
Powder coating on MDF, a sustainable future?
Powder coating on MDF is only a recent development and not yet fully implemented in the coatings sector. A few companies are using powder coatings for MDF, such as IGP, Jotun, and Sherwin-Williams. These companies, partners of DSM, showed samples of their technologies at the event, varying from small samples of powder-coated cork, and powder-coatings with concrete or weathering steel look, to a powder coated toilet seat. Companies like IKEA are experimenting with the material, proving it can be cheap and durable.
Powder coating likes to establish itself as a sustainable alternative to liquid paint, as it contains no solvents, and powder that is not attached to the surface of the MDF can be reused. A lot of furniture nowadays is made from MDF and companies such as IGP are experimenting with surfaces made of cork, composites and raw wood to apply with powder coating.
Powder coating on non-metal materials is still in an early stage, but it definitely has potential. Will your next MDF product be covered in powder coating?
Photos: Sigrid Lussenburg