What causes the adhesion problems?
How can I avoid adhesion problems?
What is corona treatment?
How do I determinate the treatment level?
What is Automatic Power Regulation?
How long does my treatment last?
How do I perform maintenance?

What causes the 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 not there will be an adhesion problem.” First figure is shown what’s the basic dyne-level of a material and what’s required in the different applications.

How can I avoid adhesion problems?
To obtain sufficient wetting and adhesion on plastic films or metallic foils in-line, pre-treatment just before the printing, laminating or coating unit is necessary. The solution to optimise the wetting and adhesion is by using a corona discharge unit since this technique has proved to be highly effective, cost effective and can take place in-line.

What is corona treatment?
Corona is in short a high frequency electric discharge towards a surface. The result from this is an improvement of the chemical connection (dyne/cm) between the molecules in the plastic and the applied media/liquid. This surface treatment neither reduces nor changes the strength and appearance of the material.

How do I determinate the treatment level?
The effectiveness of corona treatment depends on the material being used. There are no limits with regard to the materials that can be corona treated, although the required treatment/intensity level (watt/min/m2) may vary within a wide range.

The treatment level depends on the material being used, the required dyne-level, the machine speed and the number of sides to be treated.
Regarding the material the following has to be taken into consideration: the age and width of the material and whether the material has been pre-treated.

The treatment level can be calculated by using the following formula:

Power (watt) = T x S x W x M
P = Total Power (Watt) required
T = Number of sides to Treat (single/double sided)
S = Line Speed  (in metres per minute)
W = Film Width (in metres)
M = Material factor (required Watt per m² per minute)

The exact value is best determined by testing a sample of the actual film that is used for a specific application.

What is Automatic Power Regulation?
Vetaphone’s Corona-Plus treaters are equipped with automatic power regulation. When the needed treatment level (watt/min/m2) has been determined, the Corona-Plus unit is set and due to the automatic power regulation the film is now influenced by the same energy irrespective of the speed or the width of the film.

How long does my treatment last?
Over time the obtained dyne-level will fall and it can be necessary to corona treat the material again just before use (if the material contains slip the dyne-level will fall faster.)

Thicker and older film stocks are more difficult to treat as slip agents may have migrated to the surface. Material which has not been treated under extrusion can be difficult to treat afterwards, it is recommended to use pre-treated film that just needs a corona refreshment.

How do I perform maintenance?
To obtain the desired dyne-level it’s important that the insolaters are kept clean. The latest major innovation to optimise set-up of electrodes and maintenance is the unique Quick Change (QC) system. The complete Corona electrode is mounted in a specially designed pull-out / push-in cartridge.

The operator can easily perform daily maintenance without removal of the treatment material – this has proven very popular with our many customers.

The Corona-Plus treater station also has the advantage of working in extremely moist environments.