The mode of operation of the plasma is changed by varying the process parameters such as pressure, power, process time, gas flow and gas composition. Thus, several effects can be achieved in a single process step.
Plasma removes release agents (also silicones and oils) from the surface. They are chemically attacked for example by oxygen and converted into volatile compounds. Under-pressure and surface heating cause the release agents or their residues to evaporate in part. The high-energy particles in the plasma disintegrate the molecules of the release agent into smaller molecule fragments which can now be extracted. Furthermore, a "micro-blasting effect" is generated on the atomic level. UV radiation can disintegrate release agents.
Usually, invisible deposits such as greases, oils, silicones, moisture or oxidation layers are found on freshly produced as well as stored products. To ensure perfect coating of these surfaces, they must be PWIS-free (PWIS = contaminated with Paint Wetting Impairment Substances), which can be achieved with plasma cleaning.
Flow rate: 500 Watt, process chamber volume: 100 litre, process gas: air or oxygen, pressure: 0.2 - 0.6 mbar, duration: 1 – 5 minutes
A wide range of process gases (e.g. air, oxygen, argon, argon-hydrogen, tetrafluormethane-oxygen) andchemicals (e.g. hexamethydisiloxane, vinyl acetate, acetone, fluorinated chemicals) are available.
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However, there is the following basic rule: The process know-how is the decisive factor. The plasma must match the material so that all desired effects can be achieved in a directly targeted manner.
In essence, any form of plasma surface treatment serves one function – to modify the chemical and physical properties of the top layer of a material’s surface, modifying the surface’s wettability (bonding characteristics). It’s most commonly used to process plastics such as ETFE, PVC, PET, and similar plastics. Typically, applications include medical device manufacturing and wire or cable processing. But what is the difference between atmospheric and low-pressure plasma treatments?
If you’re unfamiliar with “plasma,” it is basically another state of matter, the same as solids, liquids, and gases. More specifically, you create plasma when you energize and ionize matter within a gaseous state. But how does plasma benefit surface manipulation? When exposed to the material, the plasma transfers energy to a solid, creating reactions that modify wettability and other surface characteristics. The best part about using plasma for processing purposes is that it doesn’t damage the material, making it ideal for industrial applications.
Atmospheric plasma treatment involves directly exposing a material’s surface to a stream of partially ionized gas. These plasma devices ionize this gas in real-time and produce a plasma arc, which treats the surface. Atmospheric plasma treatment is highly compatible with other processes, including bonding, striping, and marking. There are many advantages to choosing this treatment system, as they are easy to automate and integrate into extrusion lines and produce highly accurate results. As such, aerospace, defense, and other regulated industries often use atmospheric plasma treatment.
Low-pressure plasma treatment requires completely different equipment. Mainly, these systems use a vacuum chamber filled with partially ionized gas – instead of direct application, technicians expose the surface to the gas by inserting it into the chamber. A pump mechanism slowly removes the ionized gas, replacing it with a process gas. This process releases gas in a plasma state at a monitored pressure. The gas exchange repeats over time, which is better for applications requiring extremely clean surfaces. Unlike atmospheric plasma treatment machines, these systems don’t require localized ventilation.
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