Better Adhesion Through Plasma Treatment
Using the "Open-Air Plasma" process developed and patented by Plasmatreat GmbH, Steinhagen, a plasma at atmospheric pressure is applied to a material’s surface by means of special nozzles. The nozzles are operated with air or a process gas and at a high voltage. Depending on the nozzle geometry, the exiting plasma is available with an effective working width of up to 50mm at a treatment distance 40mm. The exiting plasma beam is electrically neutral, greatly simplifying and expanding the range of application. The temperature of the exiting plasma may be as high as 300°C. This helps to achieve very high processing rates and optimum results.
Gira, Radevormwald, uses the Open-Air Plasma technique to economically and reliably manufacture complex fittings for use in heart-lung machines. Inside the fitting is a metal insert that is placed in the mould and then overmoulded with polycarbonate in order to avoid post-moulding assembly. The bond between the metal and polycarbonate must be absolutely leak-free. Extensive testing has shown that pre-treatment with atmospheric plasma is the only technique that meets this requirement. Use of adhesion-modifying compounds or an additional layer of adhesion promoter is not allowed according to medical guidelines.
In the plasma treatment station, the rotating part and activated and cleaned with a pulsed plasma beam. Following this, the inserts are placed into the mould. In this application, the plasma functions as a complete inline solution for surface cleaning and activation. By using the atmospheric plasma, organic contaminants on the surface are removed through oxidation. This increases the surface tension, so that the melt can wet the metal surface.