Importance of surface tension for a correct adherence
In the application of inks, varnishes and adhesives on plastic or metal surfaces, the surface tension of the adhesion surface is decisive.
In almost all cases, a higher surface energy value of the material that makes up the surface will result in greater adherence of the material applied to it, more wetting.
To increase adhesion on a material with low surface tension, chemical or physical pre-treatments are used (this is the case for many plastics). On some occasions, the material has only apparent low surface tension due to accumulated dirt (grease and oil residues, fingerprints, etc.)
It is advisable to determine the effective limit value for each application individually. Like so many other quality control parameters, it is difficult to determine the generic limiting value of surface tension for proper adhesion. On many occasions, the value of approximately 38 mN/m is taken as the threshold value. In the case of surface energy being less than, it is to be expected that there will be poor adhesion.
The test pens and inks ensure a fast and exact determination of the surface energy, thus allowing to assess the need for a pre-treatment to be planned or to check the quality of pre-treatment or cleaning processes already carried out.
Measuring the surface tension is as simple as making a line with the test pen on the surface of the material whose surface energy we want to know and seeing the appearance/behavior of the deposited ink line.
Available in bottles of 30, 60, 120, 240, 475, 950 ml. Same accuracy as test inks: +/- 1 dynes/cm.
Accuracy and speed in the measurement, impossible ink spillage, low consumption, long conservation of the test liquid if the caps are kept tightly closed.
Application similar to the marker but depositing the ink directly from the bottle, using a brush, pipette or cotton swab. The application of the test tip on the material to be verified allows its surface energy to be easily determined with an optimum degree of accuracy.
The accuracy of the measured value with the test inks is +/- 1 dyne/cm. They come in standard value sets or loose bottles. The application brushes are integrated in the closure of the bottles.
Accuracy and speed in the measurement, good reading regardless of the type of surface, difficult to contaminate in applications with a pipette or cotton swab.
Important! Since the test liquids are composed of substances of different volatility and are hygroscopic, the bottles and markers must be properly closed immediately after use.