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Plasma Surface Treatment

overview

The most important plasma applications are:

  • Cleaning
  • Activation
  • Coating

Surface cleaning

Ultra-violet light generated in the plasma is very effective in the breaking most organic bonds of surface contaminants.

This helps to break apart oils and grease. A second cleaning action is carried out by the energetic oxygen species created in the plasma. These species react with organic contaminants to form mainly water and carbon dioxide which are continuously removed (pumped away) from the chamber during processing.

The plasma activated atoms and ions behave like a molecular sandblast and can break down organic contaminants. These contaminants are again vaporised and evacuated from the chamber during processing.


Surface activation

Activating the surface of the material means raising its surface energy.

To ensure that the adhesion of paint, glue or other liquid to the substrate is satisfactory, the surface energy of the material must be higher than the surface tension of the fluid used.

This problem occurs particularly often when we operate with such materials as plastics, glass, metal and ceramics.

And that is why – beside other purposes – plasma technology is used: to increase surface energy. Thanks to plasma activation the surface of the material remains active from a few minutes to even several months (depending on the particular material).

Plasma coatings

In plasma coating a nano-scale polymer layer is formed over the entire surface area of an object placed in the plasma. The plasma coating process takes just a few minutes. The coating produced is typically less than 1/100th thickness of a human hair, colourless, odourless and doesn’t effect the look or feel of the material in any way. It is a permanent coating too, being bound to the material surface on an atomic scale.

Plasma coatings are one of the most exciting areas of plasma technology, offering enormous potential to enhance a material’s function and value over a wide range of applications. They deliver two main categories of surface property: totally liquid (water & oil) repellent, or totally wettable.

HOW PLASMA COATING WORKS
Liquid monomers are introduced with the plasma feed gas. Monomers are small molecules which will, under the correct conditions, bond together to form polymers. Plasmas create the right conditions at the surface of the material for this to happen both quickly and efficiently. Different monomers are used to produce permanently hydrophobic and hydrophilic surfaces.