Activation with atmospheric-pressure plasma

1. Is activation of metals possible?

The activation of metals is possible in principle, however, the activation of metal is very unstable and therefore short-lived. If metal is activated, it must be further processed (glued, painted ...) within a few minutes or hours, since surfaces bond quickly and permanently with contamination from the surrounding air.

Activation of metals is only possible with the PlasmaBeam technology. The Plasma APC500 may not be used for conductive materials (e.g. metals, semiconductors). Metal activation makes sense before processes such as soldering or bonding.

2. Is activation of plastics possible?

Plastics such as polypropylene or PE are non-polar. This means that the plastics have to be pretreated before printing, painting and gluing. The process gas usually dry and oil-free compressed air is used.

The activation can be demonstrated very impressively by dipping a treated and an untreated workpiece in water (polar solution). Drops form on the untreated part as usual. The treated part is completely wetted with water at the treatment site.

3. Is activation of glass and ceramics possible?

Glass and ceramics behave like metals and have a short lifetime of activation. Compressed air is used as process gas.

4. How can the quality of the activation be tested?

The quality of the activation can be tested quickly and easily by two different methods:

Contact angle measurement

In this method, the wetting angle of a water drop to the activated surface is measured. The better the activation, the flatter the drop of water lies on the surface. This method is rarely used because the instrument is relatively expensive and the measurement can generally not be made immediately on site. In particular, large or complex shaped parts can be difficult or impossible to measure with most wetting angle measuring instruments, without first cutting them up.

Test inks

The treatment materials may be associated with a specific surface energy depending on how the test inks flow. The unit is mN/m [formerly dyn/cm]. Water has a surface energy of 72.6 mN/m. Test inks are available from 28 - 105 mN/m in 10 steps.

5. How wide is the activation track in the PlasmaBeam and PlasmaAPC 500 treatment?

The PlasmaBeam technique can ensure a treatment width of approx. 8-12 mm with compressed air as the process gas. The treatment width can be increased through the use of pure oxygen (O₂) or pure nitrogen (N₂).

The treatment width of PlasmaAPC 500 is approximately 60 mm. However, treatment is significantly more inhomogeneous than with PlasmaBeam or low-pressure plasma. Multiple treatment increases the homogeneity of the treatment.

The treatment width depends very much on the speed.

6. What is the speed of treatment?

PlasmaBeam: The treatment speed varies from a few cm per minute in the activation of ceramics or metals, up to several metres per second in the activation of plastics (e.g. carton activation prior to bonding).

PlasmaAPC 500: The maximum speed is approx. 100-150 mm/s. Further speed increase leads to an uneven treatment of the surface.

7. Are exhaust gases formed during plasma activation?

In plasma activation, mainly nitrogen oxides (NONO₂) are formed which need to be transported away from the workplace.

PlasmaAPC 500: Ozone(O₃) formation must be expected here.

8. What media are required for the installation of the PlasmaBeam or PlasmaAPC 500?

• Dry and oil-free compressed air – approx. 2000 NL/hr.
• Power supply 230 V/6 A
• Extraction for the nitrogen oxides

Suction is not required when testing devices. Maximum usage without extraction must not be more than a few minutes every hour.

Workplaces must be regularly and thoroughly ventilated.

9. Where is atmospheric-pressure plasma activation mainly used? 

This technique is well suited for the following processes:

• Local plasma activation of plastics prior to bonding
• Plasma activation of elastomers before bonding, flocking, printing (e.g. rubber profiles in the automotive industry)
• Local plasma activation of metal and ceramic surfaces before gluing or bonding

The PlasmaAPC 500 is very well suited to the treatment of plastic parts in pad printing directly in pad printing machines.

10. What are the main benefits for us of activation using atmospheric-pressure plasma?

PlasmaBeam technology can be used for in-line processes such as the plasma activation of endless rubber profiles, hoses before pressing, gluing, flock coating or painting.

This technique can be used with robots, i.e. the 2- or 3-dimensional surfaces can be scanned with the plasma jet with the help of robots.

11. Are there any wearing parts with atmospheric-pressure plasma?

Yes, the plasma nozzle must be replaced regularly.

12. Which applications are possible?

You can find more information under Applications.