Corona test inks in Detail
The adhesion of a surface is usually directly dependent on its surface energy. If the surface energy of a surface is significantly lower than that of the printing ink used, wetting is disrupted, resulting in poor adhesion.
For this reason, plastic surfaces to be printed must have certain surface tensions, depending on the type of ink used:
- Solvent-based inks => 38 to 42 mN/m (=dyne/cm)
- Water-soluble inks => 40 to 44 mN/m
- UV inks => 44 to 46 mN/m
AFS Corona test inks
Unlike the Quick Test pen, which only indicates the printability of a film with solvent-based inks, our test inks allow you to determine the exact dyn values on the film. This test ink has a different chemical composition and is not smudge-proof.
Application of the test: Place the material to be tested on a flat, clean surface and draw a line.
There are now two possibilities:
- The ink line remains on the surface for longer than 2 seconds before it contracts into droplets: The film has at least the surface tension of the dyn value printed on the test pen or ink. Repeat this test with the next higher values until the line does not remain for 2 seconds. The dyn value of the surface is then equal to the value of the ink that remained last.
- The ink line does not remain. Repeat the test with the lower values until the line remains for 2 seconds. This is then the dyn value of the surface.
Application
The measurements should be carried out at an air temperature of 23°C and a relative humidity of approx. 50%. When measuring on non-polyolefin surfaces, an increase in surface tension does not always indicate an increase in adhesion. In this case, we recommend using our contact angle measuring device or other measuring methods. The test inks we use are based on DIN ISO 8296 (corresponds to the Union Carbide test).
Shelf life: 6 months after opening and 12 months unopened.
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