How to Powder Coat on Wood Products
Some woods and wood products such as MDF have sufficient and consistent moisture content to provide conductivity and can be coated directly.
To enhance electrostatic attraction, wood can be pretreated with a spray solution that provides a conductive surface.The part is then preheated to a desired coating temperature, which softens or partially melts the powder when it is applied and helps the powder adhere to the part where it melts a little on impact.A uniform board surface temperature allows for high transfer efficiency and a consistent appearance.For powder application, an electrostatic charge is applied from the spray gun to deposit powder on the MDF surface.
Powder materials for MDF can be either thermal cure products or UV-cured powders.UV powders are heated in a melt flow oven, then cured for a few seconds under UV lamps.Thermal cure powders rely on infrared ovens, convection ovens or hybrid ovens that combine infrared and convection heating. The thermal energy melts the powder so it will flow into a level film and eventually cure, or crosslink, into a finished film.
Wood powder coating protects MDF products from chips,stains, spills, and scratches,and at the same time to provide a beautiful, durable, seamless finish.Challenges to powder coating wood are related to moistureand sap content, low conductivity, variation in properties of different MDF and EWPs, and high heat sensitivity.Exposure to high temperatures causes off-gassing, raising of grain or fibers,distortion, and charring.Two newer, fast-cure powders, ultraviolet (UV) and thermosets,help address these challenges. Powder coatings of natural wood remains experimental, but it is likely that UV powders for natural wood, especially harder varieties, will be commercially available in 2003.