MEASURING THE CORONA TREATMENT
Date: 12 September 2011
In order to detect the corona treatment level, Mag data Spa suggests to use specific liquid as the TEST INK from Ferrarini & Benelli. The producer of this liquid certifies that the values of dynes/cm correspond exactly to the mixture of Formamide and Cellosolve performed according to the ASTM D 2578-84 standard. This certification is supported by testing and sampling performed using a superior grade unit called “contact angle measuring equipment”
Wettability: is the capacity of a liquid to completely cover a flat horizontal surface of a solid. It is measured in dynes/cm.
Angle of contact: angle that is formed on the line delimiting the adhesion surface between a drop of liquid and a solid surface.
Complete wettability is present when the angle of contact is near 0° and the liquid completely cover the surface. Poor wettability is when the angle of contact is near 180° and the liquid breaks into droplets. With this method a series of liquid mixtures is used whose wetting tension values are known and the mixture at the limit of the formatioin of the drops indicating the wetting tension value of the solid is searched for.
Angle of contact near 180° – Angle of contact near 0°
Lightly spread a layer of liquid over a surface of 5 – 7 cm of treated side of film. Note the time taken for the liquid to break into droplets. If the surface of the liquid has changed after two seconds the wetting tension of the specimen is higher than that of the liquid used. To determine the exact value of the wettability a mixture with a higher value should be used until it remains intact for two seconds. In this case the wettability of the film corresponds to the value given for the liquid used for the test. On the contrary if the liquid breaks into droplets in less than two seconds, a liquid with a lower value should be used.
NOTE: all the measurements must be carried out on virgin specimens, that have not been previously tested. The test carried out by a skilled operator obtains a precision of ±0.5dyne/cm. Environmental conditions: 23° ± 2°C and Relative Humidity: 50% ± 5%.
The above mentioned products cause skin irritation, therefore it is necessary to avoid any direct contact and to protect the eyes. Always keep the container of cellosolve closed as it tends to evaporate, with the consequent modification of the composition of the mixture.
It is recommended to keep detecting liquids away from heat sources and protect by the direct light of the sun. Keep the liquid’s box in a dry and cold place and closed the bottles immediately after the spreading of the liquid.
The expiry date of the liquids is not easy to quantify because it depends on how long the bottles are left open. It is however advisable to replace the TEST INK every six months so as to guarantee perfect measurement.
SOURCE: Ferrarini & Benelli Srl.