4. How can a PWIS-free state be achieved?
Through paint-wetting impairment substances - or PWIS - clearly visible defects appear in the final product, since uniform wetting of the surface to be painted is prevented. Funnel-shaped defects and crater formations occur on the coating layer. Such substances may be silicones, fluorine-containing (PTFE) substances, certain oils and fats.
The plasma method permanently removes all paint-wetting impairment substances from the surface and from the elastomer itself.
Components from a very wide range of materials can be cleaned, such as PVC-U, PVC-C, PP, PE, ABS and PVDF, as well as metallic components.
After cleaning, the parts are treated for up to an hour with the plasma according to the degree of contamination present. To confirm the success of the treatment, and thus that it is PWIS-free, a PWIS test is carried out following plasma treatment in accordance with the Volkswagen inspection standard PV 3.10.7, which provides a rapid method for detecting silicon residues.
All that is needed is a clean glass plate, acetone and a commercially available spray paint, which must of course be free of silicone. The colour white has proven particularly suitable for this. For the test, the material to be tested is placed on the glass plate and washed with acetone. After evaporation of the acetone, the glass plate is sprayed with the spray paint in a cross shape. After the paint has dried, it can be clearly determined whether or not silicone residues are present on the surface. At these points the paint does not wet and forms a so-called crater.
Plasma cleaning can be used with special processes for the treatment of silicone materials. A PWIS-free surface can be achieved, even with silicone rubber.