Powder coating now also for wood
Achieving a smooth, even surface on wood may be difficult due to the fact that liquid coatings tend to run, sag or dry unevenly in unfavourable circumstances. Additionally, governments are pushing towards lower VOC limits and more environmentally friendly products and processes. Therefore, powder coating wood is an option to consider for replacing the traditional liquid coating applications.
Powder coating has traditionally been available only for metal surfaces as an alternative for liquid paints. Now it is however, possible to powder coat wood! Applying powder coatings remarkably improves efficiency allowing maximum production in minimum time.
Powder coating wood is the latest breakthrough in the wood working industry and it is possible depending on the wood type and pre-treatment.
The most success has been reached coating middle density fiberboard, MDF which is a board combining wood particles and resins.
The 2 reasons to powder coat wood
Powder coating wood surfaces is especially beneficial for the wood working industry including joinery & furniture sectors.
The main difference between the traditional liquid coatings and dry powders is that powder coatings do not require a solvent, which makes them more environmentally friendly. The solvents in liquid coatings ensure fluidity of the product and eases application. The solvent however, evaporates in to the atmosphere after application.
It’s not only about reducing emissions but also about making it more beneficial for you as a manufacture. Powder coating wood brings along for instance the following advantages.
- Shorter application and curing time
- Allows full process automation
By switching to powder coatings you make sure your wooden products comply to allowed emission limits AND you can maximise production!
Powder coating MDF furniture and other wood surfaces
Not only do wood powders improve the process but they also contribute to the durability of the finished products. Applying powder coating on wood and MDF surfaces results in a hard-wearing coating layer which has at least the following properties.
- Guarantees seamless coating on MDF surfaces making it abrasion and scratch resistant
- Applicable on any shape of object in different thicknesses
- Allows design freedom regarding colour and shape
- Stain resistant, UV, chemical and damp resistant
- Available in every colour of the rainbow
- Cost efficient
- Eco friendly
Powder coating MDF is also done in the UK. For example a Sheffield based company MDF Specialised Coaters Ltd. who next to traditional powder coating finishes offer specialty coatings such as antibacterial systems for MDF. MDF Specialised Coaters is a part of Batchglow, the only wood powder coating supplier in the UK. Next to Sheffield, powder coating MDF is possible in Rotherham, Nottingham, Leeds, Manchester and Worksop.
Quick introduction to powder coating wood
The process of powder coating MDF and other wood types is differs from the metal coating process. In general the process is more complex due to the fact that wood is heat sensitive and less conductive than metals. The powders are thus also different; powder coating for wood melts and cures in temperatures which does not damage the wood.
There are several different types of powders for wood such as polyester, epoxies and acrylic. The resin type should be chosen based on the application. For example epoxies are extremely durable in presence of chemicals but do not resist UV radiation.
Wood suitable for powder coating
In theory any wood type that meets the following requirements can be powder coated:
- Low porousity
- Surface resistance of less than 1101 Ω
- Homogeneous surface
- Consistent moisture content (humidity must be above 6%)
These four factors make it possible to directly apply powder coating on MDF without first applying a primer; the moisture content is sufficient to make the surface conductive. However, to enhance electrostatic attraction, wood can be pre-treated with a spray solution that provides a conductive surface.
The process that results in powder coated MDF
Medium density fiber board (MDF) complies to the requirements with homogeneous surface, low resistance and acceptable humidity (6-9 %). If the humidity level is higher than 9%, there is risk for surface bubbles and lowered surface quality. A high quality finish is dependent on the MDF panel. The surface and all the edges require thorough sanding and sometimes a primer to increase conductivity.
MDF manufacturers throughout the world are working on panels with improved conductivity, uniformity and the overall quality to make them even more suitable for powder coating. Bear in mind that the quality and properties of MDF panels can vary from producer to another.
Curing methods for MDF and wood powder coatings
Powder coating for wood surfaces exists in two kinds: thermally curing and UV curing products. The curing differs from the curing of powder coating on metals due to the fact that wood is a heat sensitive material and cannot withstand the usual curing temperatures.
The two wood powder curing methods are as follows.
|UV-curing||Requires minimum heat for curing, thus it is suitable especially for substrates sensitive to heat such as wood. After the objects entre an infrared or convection oven, where the coating melts and flows for 2 to 10 minutes, the substrate is put under exposure of UV rays for a few seconds for final curing and hardening of the finish. Then the parts cool naturally or in a cooling tunnel before unloading them from the coating line.|
|Thermal curing||Powders rely on infrared ovens, convection ovens or hybrid ovens that combine infrared and convection heating and guarantee uniform heating of the object. The thermal energy melts the powder allowing it to flow into a level film and eventually cure, or crosslink, into a finished film. Equal temperature of the object is crucial!|