Prof. Dr. Viöls working group has been developing patented industrial methods for plasma treatment of wood and derived timber products in cooperation with partners from industry and scientific research institutes (Georg-August-Universität, Prof. Dr. Holger Militz) for 10 years. The methods are based on a system used for the treatment of plastics (dielectric barrier discharge, Corona discharge); they are advanced for a large-area treatment of wood and derived timber products. Plasma treatment is an industrial proven technology and can be integrated without further problems in established production lines (picture no 1)

Picture no 1: Plasma treatment of wood

The method:
The plasma used for the surface modification of wood and derived timber products is based on the dielectric barrier discharge (DBD), also called “silent discharge”. There, metallic electrodes are separated by a dielectric, e. g. ceramics. In generating a high voltage to the electrodes, the plasma is ignited in the gap for gas (picture no 2). The material chosen for the treatment is placed directly in the discharge zone. The treatment is considered as very environmental friendly and economic, for only compressed air and electric current are needed. The device for the treatment needs just little space and can be integrated without further problems in established production lines.

Results:
It was shown that a plasma treatment activates the surfaces of fiberboards and chipboards and shortens the drying times of water based glues (picture no 3), so that process times can be reduced and adhesion can be improved.

Another significantly increased adhesion could be proved for a plasma treatment of wood-plastic composites (WPCs). In picture no 4 one can see the results of experiments about the influence of plasma treatment on the adherence; the adhesion of lacquer on WPC surfaces can be increased so much that it exceeds the cohesive power inside of the WPC.