• DK: +45 76 300 333
  • US: (312) 803-3691
  • [email protected]
Search
  • Careers
  • Contact Us
  • Products
    • Subitem
      • Products
      • Converting
      • Narrow Web
      • Extrusion
    • Subitem
      • Coating
      • iPlasma
      • Generators
      • Web Cleaner
    • Subitem
      • Accessories
        • Dyne Pens
        • Ozone Eliminator
        • Ozone Removal
  • Corona
    • Corona
    • HD Precision Corona
  • Plasma
  • KNOWLEDGE HUB
    • Knowledge Centre
    • Technical Whitepapers
    • FAQs
    • Knowledge Sharing
  • Test Lab
  • Showroom
  • Support & Spares
    • Support
    • Contact Support
    • Spare Parts & Returns
    • Request Spare Parts
    • Request Dyne Pens
  • About
    • About Us
    • Why Choose Us?
    • Meet the Team
    • Sustainability – ESG
    • History
  • News
  • Global Network
  • Careers
  • Contact Us
Home About Us FAQs

FAQs

CORONA TREATMENT IN GENERAL

What is Corona treatment?

Corona is a high frequency electric discharge directed at a surface. It results in an improvement in the chemical connection (dyne/cm) between the molecules in the surface and the applied media/liquid. This surface treatment neither reduces nor changes the strength or appearance of the material.

What does Corona treatment change in my material?

Plastic is a man-made synthetic material, which contains long homogeneous molecular chains that form a strong and uniform product. The chains of molecules are normally joined end to end forming even longer chains, leaving only a few open chain ends, and providing only a small amount of bonding points at the surface.

During Corona discharge treatment, electrons are accelerated into the surface of the plastic causing the long chains to rupture, producing a multiplicity of open ends, and the formation of free valences. The free valences are then able to form carbonyl groups with the atoms from the ozone created by the electric discharge, which gives improved adhesion.

The adhesion is further enhanced by the cleaning effect of the ozone, by oxidation on the surface of the material.

What causes adhesion problems?

Whether a liquid wets a material well or poorly depends primarily on the chemical nature of both the liquid and the substrate. Wetting is defined as the ratio between the surface energies of the liquid and substrate.

In general, the following rule is true: ‘A material will be wetted, if its surface energy (dyne/cm) is higher than that of the liquid, and if it is not, there will be an adhesion problem.’

How can I avoid adhesion problems?

To obtain sufficient wetting and adhesion on plastic films or metallic foils inline, pre-treatment just before the printing, laminating, or coating unit is necessary. The way to optimise wetting and adhesion is to use a Corona discharge unit because this technique has proved to be highly efficient, cost effective, and can take place inline.

How long does treatment last?

The increase in surface energy (dyne/cm) that is induced into a film begins to decay immediately following treatment, with the additional considerations of storage conditions and ambient temperature. Generally speaking, the more difficult a material is to treat, the quicker it is likely to decay. It has been established that film with very high slip additives (over 1200 ppm) can be totally resistant to printing just 24 hours after treatment, and it may be necessary to process the film immediately following treatment, or boost the treatment inline with the printer. Ageing of such films can render them impossible to treat if they are not treated during production.

What are dyne levels and how do I test them?

Dyne is a unit of measurement used to determine the surface energy of a film or foil. Use the test method described by DIN 53364 and ASTM D2578-67, which is a liquid test, to carry out the measurement of the surface energy of a film. The liquid is applied as a broad line in a thin layer with either a brush or a pen.

The surface tension is then determined visually by estimating how the liquid reacts within the first two seconds following application. The test liquid can shrink and/or form itself into globules (individual droplets) or it can remain unchanged.

When a test liquid shrinks or forms into droplets it indicates that the film has a lower surface energy than the liquid applied. The test should be repeated as many times as necessary with a liquid of a lower surface tension until it remains unchanged for a period of two seconds or more. Once this has been achieved, the film can be said to have a level of surface energy at least equal to that of the liquid applied. Further applications should be made until shrinkage or droplets occur within two seconds. This last measurement should be taken as failure, and the surface energy of the liquid used for the previous measurement should be taken to be the surface energy of the film.

What is ozone and is it dangerous to my operators?

Ozone is a gas that is formed during the process of Corona discharge, and plays an important part in the chemical and molecular changes that take place in the surface of the plastic. Ozone is hazardous to health and has an unpleasant smell, even at relatively low levels. The average human can smell ozone at 0.01 ppm.

The safety threshold in an area occupied by personnel is 0.1 ppm. All Vetaphone equipment is designed to remove ozone effectively from the treater station by means of an ozone-protected blower/fan, and a specially designed exhaust system.

What is the effect of Corona treatment on paper? How long does it last? How can we measure it?

When treating paper with Corona you will get the benefits of cleaning the surface and removing any unwanted paper fibres that could create pin holes during the coating process.

The treatment level lasts for a minimum of six months. The only way to measure the dyne level is by using a water drop measurement.

Does Vetaphone offer equipment for ATEX environments?

Vetaphone is able to offer equipment for ATEX environments; however this must be designed and calculated according to customer requirements. Normally, Vetaphone offers pressurised units which also prevent solvents from reaching the Corona discharge.

TREATER STATION

Why use Ceramic Electrodes?

The ceramic electrode is used for treatment of both electrically conductive (aluminium foil and metallised film) and non-conductive substrates (PE, PP, etc.) in widths of 0.1 m to 3 m. Each individual ceramic bar can take a load of approximately 1.25 kW/meter, and with a maximum of six tubes in one electrode cassette, the total output can be 7.5 kW/m. The electrodes consist of square section ceramic tubes, with metal inner conductors. They are mounted in special insulators, and each tube can be changed individually, with provision for expansion, ensuring uniform treatment of the film.

Unlike metallic electrodes, a ceramic electrode does not need a dielectric covering on the backing roller. This eliminates downtime associated with changing defective sleeves or coverings.

How can I clean the station?

For correct maintenance of the station it is important that it is cleaned thoroughly once a month. When an insulator or other part applied to high voltage is covered with dirt, there is a big risk of an electrical flash-over in the station, which results in a breakdown. It is necessary to change the insulator after a flash-over has occurred.

How can we clean ceramic electrodes?

Before start-up, it is necessary to check that the ceramic electrode bars and electrode holders (insulators) are clean and free from grease and dirt. Cleaning of the electrodes should be given special attention, especially cleaning between the ceramic bars. An accumulation of dirt will prevent an effective cooling of the bars, resulting in overheating, which again causes the ceramic surface to crack. This leads to machine
stop, and the defective ceramic bars will have to be replaced before production can start again.

Electrodes covered with dirt will result in an uneven Corona treatment of the film.
It is very important to keep bars and insulators clean. Cleaning can be done with spirits/alcohol.

Check out this quick video guide on how to clean the cartridge and electrodes:

What is a NIP pressure roller?

The NIP is a pressure roller that is intended for use at speeds above 350m/min or with low web tension. The NIP roller will add pressure to the material passing though the treater station preventing pin holes or backside treatment. Remember that you cannot add a NIP roller on a silicone sleeve backing roller as this will be torn off.

What is Tendency Drive?

The purpose of Tendency Drive is to help the film turn the backing roller and to avoid stretching or wrinkling a thin film when passing through the station. An AC-motor is mounted on the endplate of the station and a toothed timing belt drives the backing roller. The supplied control box is equipped with a main switch and a potentiometer for adjusting the torque for the motor. The film controls the rotation of the backing roller while the Tendency Drive motor helps the film to overcome the inertia of the roller and ball bearings.

What is Synchronised Drive?

The purpose of Synchronised Drive is to match the backing roller’s speed exactly to the speed of the rest of the production line to avoid stretching or wrinkling a thin film when passing through the Corona treater station.

A DC-motor is mounted on the endplate of the station and a toothed timing belt, between the pulley on the motor shaft and the roller shaft, drives the backing roller.

A tacho-generator is integrated on the motor which supplies the electronic controller with information about actual speed. From an external tacho-generator, which is driven by another roll in the production line, the signals are fed to the controller and compared with signals from the motor-tacho, which allows the motor speed and the backing roller to be synchronised with the main machine.

What is SKIP treatment?

In order to leave untreated areas at welding points, it is essential that the Corona system is able to make intermittent treatment on printing lines. Vetaphone Skip Control is designed for this purpose.

The Vetaphone Skip Control operates with input from a roto pulse sensor connected to the printing cylinder. Using impulses from the sensor as a reference, the position and the length of the treated area can easily be adjusted even during production.

Adjustment can be made for one or two generators (A+B) and is done by setting four parameters in steps from 1 to 360 degrees of the circumference of the print cylinder, or alternatively in millimetre steps.

What type of segmented electrodes does Vetaphone offer?

2.5mm, 5mm and 10mm width in aluminium.

What is the recommended Air Gap setting?

Between 1.5–1.8mm, depending on the application and material.

What is backside treatment and how can I avoid this?

Backside treatment occurs when both sides of the material are Corona treated instead of just the one side intended.

Unwanted treatment on the ‘wrong’ side can result in blocking problems, making it impossible to unwind the material, or creating pin holes in the material. In addition, unintentional treatment of the ‘wrong side’ can cause poorer efficiency on the correct side as a result of lower dyne levels.

The most common reason for backside treatment is build-up of dirt on the backing roller. To avoid this, simply clean the roller according the maintenance plan.

Another cause could be an increase in line speed. As the line speed increases (above 350m/min) there will be more air travelling with the material which can result in small air bubbles being created between the material and the roller. The air in this gap ionises and produces backside treatment. The use of a NIP roller can prevent this problem occurring because it ensures the film is wrapped perfectly around the roller and does not leave any spots with air bubbles.

The last major problem of backside treatment is the creation of wrinkles.

How can my dyne levels vary from batch to batch?

This depends on your raw material supplier. If they change the recipe then they also change the composition of the material. Each time you change your raw material supplier, remember to check the dyne level and adjust the material factor accordingly.

We have a Test Lab at our Kolding HQ, if you would like to arrange a material test, you can click here for sheet testing, or if you would like roll to roll testing of your material please drop us an email at [email protected] where one of our expert team can help you further.

How do I adjust the Air Gap?

Keeping the correct air gap is a very important factor in obtaining the best performance. With the wrong air gap you risk having lower dyne levels or even different dyne levels across the web.

In general, Vetaphone has three types of treater station designs, each with its own way of adjusting the air gap settings. Please refer to the manual supplied with your equipment for further explanation.

Get in touch

Get in touch

If you wish to contact us with a support request then please go to our support page and contact us from there.

  • (Please provide index no. for quicker and better support)
  • Max. file size: 50 MB.
  • Max. file size: 50 MB.
  • (Please provide index no. for quicker and better support)
  • (Please provide serial no. for quicker and better support. You will find the 5 digit serial no. on the front of the Corona station)
  • This field is for validation purposes and should be left unchanged.

Members of

MEMBERS OF

  • FTA
  • TLMI
  • DANSK FLEXO FORUM
  • DFTA
  • DFTA

Newsletter Sign Up Modal

CSR

Quick Links

  • Products
  • Our Offering
  • Case Studies
  • Support
  • About Us
  • Global Network

Useful Information

  • Request a quote
  • Request Spare Parts

Follow us

Contact Us

Vetaphone A/S
Fabriksvej 11,
DK-6000 Kolding,
Denmark

Vetaphone North America
155 North Wacker Drive, Suite 4250
Chicago, IL 60606
USA

 

DK: +45 76 300 333
US: (312) 803-3691
[email protected]

© 2025 Vetaphone A/S

  • Privacy policy
  • Quality Policy
  • The Eisby Trust
  • Payment Details
  • Terms
  • Whistleblower
Manage Consent
To provide the best experiences, we use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us to process data such as browsing behaviour or unique IDs on this site. Not consenting or withdrawing consent, may adversely affect certain features and functions.
Functional Always active
The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.
Preferences
The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.
Statistics
The technical storage or access that is used exclusively for statistical purposes. The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.
Marketing
The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.
Manage options Manage services Manage {vendor_count} vendors Read more about these purposes
View preferences
{title} {title} {title}

Support