Electrical Air Plasma
Key Takeaways
- Ambient air is the working gas, so no specialty gas supply or cylinders are needed.
- It runs in open air with no vacuum chamber, suiting continuous production lines.
- Three system types: corona discharge, atmospheric pressure plasma, and plasma jet configurations.
- Activation decays over time. Surface energy gains degrade unless the part is bonded or coated promptly.
Electrical Air Plasma
Electrical air plasma is an atmospheric-pressure surface pretreatment that uses ambient compressed air as the process gas, ionising it electrically to oxidise and activate polymer surfaces immediately before bonding, printing or coating. It requires no vacuum, no bottled gas and no combustible fuel — clean dry compressed air and electrical power are the only inputs, which makes it one of the simplest pretreatments to integrate into an existing production cell.
Mechanism
An electrical discharge within the treatment head ionises the air stream, generating oxygen radicals, ozone, excited nitrogen species and UV. Directed at a polymer surface, these species break carbon–hydrogen bonds in the top few molecular layers and graft oxygen-containing polar groups in their place. Surface energy rises immediately, contact angle falls, and adhesives, inks and coatings wet the surface instead of beading on it.
The same discharge simultaneously ablates the weak boundary layer of mould release agents, slip additives and airborne oils that otherwise dominate adhesion failure. In practice this cleaning contribution is often as important as the chemical activation itself — a point examined in Sabreen’s discussion of adhesion failures.
Key Process Parameters
| Parameter | Practical guidance |
|---|---|
| Standoff distance | Usually 5–20 mm. The single most sensitive variable; reactive species recombine quickly in open air. |
| Dwell / traverse speed | Set to give consistent exposure. Under-treatment gives no bond; gross over-treatment degrades and weakens the surface layer. |
| Air quality | Must be clean, dry and oil-free. Compressor carry-over deposits oil on the very surface being cleaned. |
| Part fixturing | Repeatable presentation matters more than raw power — varying standoff produces varying dyne level across the part. |
Strengths and Limits
- Inline and robot-compatible. Heads are readily mounted on a robot arm or conveyor for treatment of moulded three-dimensional parts.
- Selective treatment. Only the bond area need be activated, which preserves the untreated appearance and printability of the remainder of the part.
- No open flame. Where a combustion process is unacceptable on safety or facility grounds, electrical air plasma is the practical substitute for flame plasma.
- Line-of-sight limited. Recesses, undercuts and internal surfaces are shadowed; those geometries point toward low-pressure cold gas plasma.
- Ozone generation. Local extraction is normally required.
- Treatment decays. Surface energy falls over hours to days as polymer chains reorient, so bonding should follow treatment promptly.
Confirming the Result
Treatment level should be verified rather than assumed. Wetting tension solutions to ASTM D2578 give a rapid dyne reading at the workstation; contact angle goniometry provides the quantitative value for process validation. Establish the required dyne level empirically for the specific adhesive or ink system, then monitor it — nozzle wear, air quality drift and fixture wander all move the result over time.
Related Terms and Reading
- Electrical air plasma treatment services
- Atmospheric plasma surface pretreatment
- Plasma surface pretreatments of polymers for improved adhesion
- Measuring adhesion and abrasion durability of coatings and inks
Applying this in production
The Sabreen Group provides independent engineering support for electrical air plasma and inline surface activation. If you are specifying a process, qualifying a material or troubleshooting a production problem, our engineering services team can help. Contact us to discuss your application.
Frequently Asked Questions
What is electrical air plasma?
A plasma treatment using ambient air as the working gas, energised by high-voltage electrical discharge to create a reactive plasma field. It modifies surface properties to improve adhesion, without requiring specialty gases or a vacuum environment.
How is the plasma generated?
A strong electrical field — via arc, corona, or dielectric barrier discharge — ionises the ambient air between electrodes or near a nozzle. The ionised air forms a cold reactive plasma containing the species that oxidise and activate the surface.
What can air plasma be used for?
Surface cleaning to remove oils, residues and organic contaminants before coating, painting or bonding; surface activation to raise surface energy for better ink, adhesive and coating adhesion; and micro-etching to lightly roughen the surface for mechanical keying.
How deep does the treatment go?
Not deep. Modifications are superficial, typically confined to the top few nanometres or micrometres of the surface. That is sufficient for adhesion, since bonding is an interfacial phenomenon, but it means the effect is fragile.
Why does treated surface energy fade?
Because polymer chain mobility lets the oxidised functional groups reorient away from the surface, and low molecular weight additives migrate back to it. The effect is time-sensitive, so parts should be bonded or coated quickly after treatment.
