Why Should I Measure Dyne Levels?
When measuring dyne levels of a substrate for Flexo Printing you are measuring the substrates surface tension. If an ink is to spread over a substrates surface in a uniform layer, or wet out, the substrate must have a surface tension higher than that of the ink.
Polymer films have a non-porous surface with low surface tension making it less receptive to bonding with inks, coatings or adhesives. In-line treating aggravates the surface, raising the surface tension to make the substrate more receptive to the application of inks, adhesives or coatings. To insure bonding to the substrate through the printing, converting and packaging process consistent measurement of the surface tension or dyne level is required.
How Do I Measure Dyne Levels?
Three common methods are used to measure dyne levels. The dyne pen method, cotton swab applicator method and the draw down method. Each process certainly has its own pros and cons. We will focus on the dyne pen method since it is believed to be the easiest to conduct in a production environment. Dyne pens are typically available from 32-58 dynes.
For the results of the test to be considered meaningful the following guidelines should be observed:
- Do not use outdated dyne pens (replace every 6 months)
- Do not touch or contaminate the surface to be measured
- Place sample on a clean, level surface
- Test several areas across the web
- Test supplies and samples should be 20-25 degrees C. at the time of testing
- The first pass of a dyne pen should be ignored as it flushes contamination from the tip
The testing procedure is as follows:
- Choose a dyne pen you believe to be slightly below the level of treat of your sample
- Draw a sample in 3 different areas across the web
- If the fluid remains intact for more than 2 seconds without beading, perform the test again with the next highest level dyne pen
- Breaking of the fluid in less than 2 seconds indicates lack of treat or wetting for the selected dyne level
- Your treat level is the highest numbered dyne pen that the fluid remained intact for greater than 2 seconds
Where Should My Treat Level Be?
Recommended treatment ranges usually vary beyond material type, ink type or printing process. These ranges should be used as a general guideline to begin your own evaluation process.
Hi Dan, thank you for your informative article about measuring dyne levels of film. What about the dyne levels of the flexo printing plate and the anilox roller please?
Are there specific dyne levels applicable for these printing tools please?
Hello Peter,
I am no expert on both the plates and the rollers, but I have experience with both. I have found that water wash plate has a lower dyne level and therefore carries more ink, or picks up in and transfers ink better. Anilox rollers, really have no dyne concern, unless improperly cleaned or covered with chemistry. The shape, depth and size of the cells has all the importance in the world. With water based, using an open cell creates less air, less foaming, and so on.
What dyne level does BOPP film need to be treated to accept print and is this done in-line or off line?
Hi Brian,
Sometimes the material comes in pre-treated. You should certainly perform a test to see where it is at. It can be “bump” treated inline to raise the level of treat. As the above charts are just a guide you should always perform a test with your particular inks and substrates to be sure you have proper adhesion. Typically on films with solvent inks 38-40 is acceptable and films with water-based inks will require a higher level of treat, usually in the 42-44 range.
Hi Brian,
Can you tell me the range for the aluminum film? I’m doing flexo water base.