Corona treatment

Corona treatment generates a high voltage electrical discharge that is applied to the surface to be treated (plastics, paper, metallized surfaces, sheets...).

Corona treatment is mainly used by packaging companies: extrusion processes, converting, laminating, printing and all flexible packaging processing lines in general. It also has other applications: treatment of tubes, sheets, refrigerator panels.

Corona treatment is mainly used on plastics: polyethylene, polypropylene, polystyrene, PET and PVC, but it can also be applied to metals and plastic-coated paper.

Corona treatment is a faster and easier process than chemical treatments. It is also more environmentally friendly as it does not involve the use of harmful chemicals.

The effectiveness of corona treatment is measured using the Dyne kit in the form of liquid mixtures, pens or markers by measuring the surface tension of the substrate with the appropriate solution.

• Type of substrate treated: each substrate reacts differently to corona treatment.
• Discharge intensity: the intensity and duration of the treatment will affect its effectiveness.
• Environmental conditions: factors such as dust, moisture, and contaminants can reduce the effectiveness of treatment.
• Line speed: higher speeds require more power and surface area.

Yes, corona treatment is a safe and user-friendly treatment as long as the safety regulations, the instructions in the supplied user manual and the provider's instructions are followed. Proper handling of the systems and regular maintenance are key to avoid risks.

Corona treatment consists of an electrical discharge generated in a confined, linear space between an electrode and an insulated, grounded counter-electrode. Corona discharge treats large substrates such as plastic films, foils, sheets, metallized films, and plastic-coated paper.

Plasma treatment consists of an in air plasma discharge that removes contaminating particles from surfaces by increasing their surface energy. Plasma treatment acts on small areas (treatment area between 10 and 140 mm) of plastic objects, small flat surfaces, tubes and pipes, electrical and special cables.

Yes, from the control panel on the generator.

Corona treatment works on paper (e.g. to help anchor PE in the extrusion coating process). However, it is not possible to measure the level of surface treatment achieved using the Dyne test kit. This problem does not exist when treating plastic-coated paper.

Aspects to consider in determining whether your substrate should be treated are:

• Difficulty of the substrate to hold inks, adhesives and coatings
• The final quality you want to achieve (good adhesion of labels, printing, coatings)
• Adhesion tests that may have been performed on the substrate, indicating it has a low surface tension.

The air gap in corona treatment refers to the distance between the electrode and the surface of the substrate to be treated. The air gap affects the intensity of treatment: too much distance could reduce the effectiveness of treatment.

If the material is not receiving adequate corona treatment, check the following:

• Electrode-to-roller gap (air gap): Check that the distance between the electrode and the roller is correctly set. An excessive air gap reduces treatment effectiveness. The recommended gap is 1.5 mm for silicone-covered rollers and 1.3 mm for ceramic electrodes and ceramic rollers.
• Slip agent (or other additive) content: Check that the concentration of slip agents or other additives in the material is not too high, as excessive additive levels can reduce the effectiveness of the corona treatment.
• Treatment measurement: Ensure that the treatment level is measured immediately after treatment using the Dyne Test Inks.

Corona treatment occurs when high voltage electrical discharges are applied to the surface of the substrate. These discharges ionize the surrounding air and break up oxygen molecules in the air. Oxygen atoms can then combine with other oxygen molecules to form ozone.

Ozone poses a risk to human health when present in high concentrations in the air. Therefore, ozone must be removed from the work environment, an ozone destruction equipment must be used, and ozone levels in treatment areas must be controlled to ensure operator safety.

The effect of corona treatment on the surface of a substrate is temporary and its duration varies depending on the substrate type, environment and storage conditions. For this reason, it is recommended that the treatment be performed in-line, i.e. immediately prior to the application of inks, adhesives or coatings. In particular, surface migration of lubricants and additives may rapidly reduce the effectiveness of the treatment and a treatment reinstatement may be required to restore the surface tension.

The data to be provided are: type of application requiring corona treatment, type of substrate, width and thickness of substrate, number of sides to be treated, and line speed. It is also advisable to provide the surface tension level that the substrate must achieve to be considered suitable for adhesion.

Yes, corona treatment is used in the furniture and interior design industry to treat the surfaces of panels and profiles coated with decorative thermoplastic films through lamination and bonding processes.

Decorative thermoplastic films are widely used to achieve aesthetic and functional surfaces, but adhesion effectiveness depends on proper surface preparation.

Always refer to the user manual provided with the corona treater. The following are some general guidelines.

Ceramic electrodes: Clean the ceramic surface using soap and water. For stubborn residues, use a non-abrasive scrubbing sponge. Once all residues have been removed, allow the electrodes to dry completely before use.

Metal electrodes: Follow the procedure described in the user manual to remove and reposition the electrode assembly correctly for maintenance. Clean the electrodes using a high-pressure washer, then dry them thoroughly. Apply a PTFE-based spray lubricant and allow it to dry completely before operating the equipment to prevent any lubricant from dripping onto the material being treated.

Clean the ceramic roller using a soft, clean cloth lightly dampened with ethyl alcohol, methyl alcohol, or ethyl acetate.
Always handle these cleaning agents in accordance with the applicable safety guidelines and wear appropriate personal protective equipment (PPE).

Over time, the corona treatment process causes normal wear to the silicone sleeve coating the treatment roller. Under standard operating conditions, the sleeve should be replaced every two years. However, if signs of excessive wear are evident, it should be replaced before the recommended replacement interval.

A short-circuit alarm may be triggered by one or more of the following conditions:

• Incorrect wiring of the high-voltage transformer (HVT) cable.
• A damaged or burned-out high-voltage transformer (HVT) winding.
• Excessive water or contamination inside the treater.
• Cracked or punctured ceramic electrodes (if fitted).
• A punctured silicone sleeve (if fitted).
• Moisture inside the treater.

A temperature alarm may be caused by one or more of the following conditions:

• Clogged air filters on the cooling fans.
• Cooling air temperature exceeding 40°C (104°F).
• Failure or malfunction of one or more cooling fans.