MDF powder coating

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MDF powder coating is a process for surface finishing of MDF boards . The proportion of the process is very small in both powder coating (<3%) and MDF (2%), but the process is seen as one of the future markets for powder coating. Like all powder coatings, the paints are produced entirely without solvents , which is why there are no adverse effects on the environment or users from solvents. The process was therefore included in a funding program by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety and ultimately adopted as the best available technology .

development

The first powder coating formulations for coating wood and wood-based materials were developed in the early 1990s. The first industrial application of the technology takes place in 1994 in the company Hali Büromöbel in Austria. In Germany , a southern German supplier and a well-known office furniture manufacturer worked intensively on establishing powder-coated MDF panels for the first time in 2002. In addition to the pioneers of the process, several contract coaters are now working on market penetration. The surface is only slowly gaining acceptance in the market. This is primarily due to the fact that not all difficulties with regard to the process have been eliminated, especially the hygroscopicity of all wood-based materials.

process

The coating process is basically comparable to classic powder coating. The substrate plates are suspended from a circular conveyor and guided through the individual process steps. In contrast to classic powder coating, powder coating systems for wood-based materials use a preheating zone that is used to heat the surface evenly.

Since MDF is an electrical non-conductor , the requirements for the application are higher than for metallic materials. The conductivity of the substrate is controlled not only by equipping the panels with conductivity additives but also by setting the panel humidity exactly. The layer thickness is another challenge during application, as the thermosensitive wood-based material can only be heated for a limited time.

For the powder coating of wood substrates, low-temperature powder coatings are usually used, which crosslink at 110 to around 150 degrees Celsius . Melting is done by infrared radiation or gas catalytic ovens. In particular, a homogeneous temperature distribution on the surface and the substrate edges is necessary so that the powder melts evenly and as simultaneously as possible. The curing process takes place after thermal melting. The powder is cured with UV radiation or thermally, preferably using gas-fired ovens. The advantage of gas catalytic converter technology lies in the better controllability compared to hot air and UV ovens. The advantage of UV curing is that the melting and curing processes take place separately from one another.

Difficulties of the procedure

The greatest difficulty is seen as the risk of cracking during later use. Changes in the air humidity lead to changes in the moisture content in the material, which causes a change in thickness that can lead to cracks in the paint. The application as a single layer of paint (i.e. without a primer) requires a very smooth substrate that cannot be achieved with conventional methods such as sawing or milling . Another challenge is controlling the moisture in the material itself. A minimum moisture content of around 8% is required for application. Since this water escapes again during hardening, surface defects such as craters can occur there. For this reason, no high-gloss systems are currently used for coating wood-based materials.

properties

The powder coating of MDF enables a form-fitting substrate coating without edges or foil / laminate joints . MDF powder coating is particularly advantageous for constructions with cutouts, undercuts or complex edge geometries.

literature

  • J. Pietschmann: Industrial powder coating . 3. Edition. Vieweg & Sohn Verlag, Wiesbaden 2010, ISBN 978-3-8348-0463-1 .

Web links

Individual evidence

  1. ^ Jim Ridge: The European Powder Coating Market . In: European Coatings Directory 2008 - Special Issue: Powder Coatings . Vincentz Network, Hanover 2007, p. 24 f . (English).
  2. ↑ Fund recipient: Sauter GmbH in Überlingen / Baden-Württemberg - Project: Introduction of a new type of powder coating process for temperature-sensitive wood-based materials and plastics. In: bmu.de. Archived from the original on October 9, 2007 ; accessed on April 30, 2019 .
  3. ↑ Environmental innovation program - a balance sheet of the effects. (No longer available online.) In: Federal Ministry for the Environment, Nature Conservation and Nuclear Safety. Archived from the original on December 1, 2011 ; Retrieved September 5, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.bmu.de
  4. ↑ Best available techniques for surface treatment using organic solvents. (PDF; 3.7 MB) Retrieved September 5, 2010 .