Low Pressure Cold Gas Plasma
Cold gas plasma, also termed “Low Pressure Cold Gas Plasma,” is conducted in an enclosed evacuated chamber, in comparison to atmospheric (air) surface pretreatment methods. Industrial-grade, 100 percent oxygen gas (O2) commonly is used, as well as other gases and combinations of gases. Gas is released into the chamber under a partial vacuum and subjected to an RF electrical field. It is the response of the highly reactive species generated with the polymers placed in the plasma field, on inner conductive electrode aluminum shelves or cage, breaking molecular bonds that results in cleaning and chemical/physical modifications (including an increase in surface roughness, which improves mechanical bonding). A significant benefit of cold gas plasma processes is the removal of hydrocarbons, thereby eliminating solvent cleaning. Atmospheric pretreatments do not remove/clean all poly-aromatic hydrocarbons, so solvent cleaning (prior to pretreatment) may be necessary.
Myth: Cold gas plasma batch processing is too slow compared to inline treatment methods.
Fact: Large volumes of parts often can be pretreated (batch) and fed into automated assembly operations, thereby no additional processing is needed. Cold gas plasma-treated parts tend to demonstrate the highest quality treatment and longest shelf life. Criticism arises from competitive equipment manufacturers.
Frequently Asked Questions
What is low pressure cold gas plasma?
Cold gas plasma is carried out in an enclosed evacuated chamber rather than in open air. Industrial-grade oxygen is commonly used, as are other gases and gas combinations. Gas is released into the chamber under partial vacuum and subjected to an RF electrical field; the highly reactive species generated then break molecular bonds on the polymer surface, cleaning it and modifying it chemically and physically.
Is batch cold gas plasma too slow for production?
This is a criticism that tends to originate with competitive equipment manufacturers. In practice large volumes of parts can be pretreated in batch and fed directly into automated assembly, so no additional processing is needed. Cold gas plasma-treated parts also tend to show the highest quality treatment and the longest shelf life of the available processes.
Does cold gas plasma remove contamination as well as activate the surface?
Yes -- and this is one of its main benefits. It removes hydrocarbons, which can eliminate a separate solvent cleaning step altogether. Atmospheric pretreatments do not remove all poly-aromatic hydrocarbons, so with those a solvent clean beforehand may still be required.
Does cold gas plasma improve mechanical bonding as well as chemical bonding?
It does both. Alongside the chemical modification, the process increases surface roughness, and that added topography improves mechanical bonding independently of the chemistry.
