Summary
The Henkel company uses a powder coating plant to coat products from own production and furniture. After coating, the components are finally assembled together with externally procured add-on parts made of rigid PVC. These PVC parts are to be replaced by powder-coated MDF boards in order to achieve powder coating for the entire range of parts. Difficulties arise mainly from the low electrical conductivity of the MDF substrate as well as the high baking temperatures of the powder coating materials (generally > 140 °C), which can cause outgassing from the MDF material.
During the tests carried out on the application behaviour, the MDF boards are conditioned at 20 °C in order to achieve an optimum value of the surface resistance on the MDF parts with regard to electrostatic application and curing. This process for coating substances by means of compensating charges achieves application efficiencies comparable to those on metallic substrates. For powder coating curing, the thermopressing process was tested. The main advantages are the short curing times and the low thermal load on the substrate. The best results are achieved by pre-gelling the front side (IR emitter) before thermopressing.
The economic and ecological advantages of electrostatic powder coating in combination with the thermopressing process compared to the application of wet paint, e.g. spray painting, are the lower energy costs and a reduction in the number of process steps. Powder coatings, in contrast to wet coatings, have no solvent emissions. In addition, powder coating allows the powder that is not deposited on the workpiece to be recovered. As a result, the process is almost waste-free (approx. 10 g powder waste/m² MDF), while wet painting can be assumed with a paint sludge accumulation of approx. 150 g/m² MDF.
Source: Final report
