Surface energy is the energy that is invested to break molecular bindings between surface molecules of solids and liquids. While if the surface energy is high, it has a tendency to attract other molecules. However, liquids with high surface energy tend to form stable spheric shapes and liquids with low surface energy keep their surface less in shape and start to flow easier.
On the other hand, there are many different ways to measure surface energy like dyne test which uses the dyne test kit , contact angle test, and tape test. The most common of these test methods employ an indicator solution known as dyne solution that is applied to the surface of the treated substrate.
As the dyne level testing is subjective, it is not uncommon for the individual interpretations to vary beyond the typical accuracy of +/-2 dyne. In order to minimize this error, dyne level testing should be performed in accordance with the testing methods described by the American Society of Testing and Materials.
Generally, dyne is a solution that is made from ethyl cellosolve and formamide. The percent of the concentration of the two chemicals determines the wetting tension or energy of the solution. The solution usually contains a dye that allows better visibility when applied to the surface of the material. In the end, the dyne solution is a hazardous material that requires proper handling and disposal requirements.
The Dyne-Pen Method
The dyne pen method is the fastest and easiest method to determine the surface energy. Dyne pens should also be marked with dyne levels on them. In order to test the surface energy, the pen is drawn across the web and the operator looks to see that the solid line does not break up for more than two seconds.
These pens are designed to indicate surface treatment levels on polymer-based substrates. However, dyne test is not so accurate as other methods because of the possible contamination of the tip. The only advantage of the dyne test method is that it is quick and shows the operator which side is treated.
While the dyne pens have an expiry date of 6 months that must be dated upon the first use and the tip should be sealed immediately after use. While if you want dyne test markers then you can get it from ice-equipment.com.
Cotton Swab Applicator Method
In this method, a cotton swab is dipped in the solution from a calibrated dyne-level solution container. After that, the solution is spread lightly over approximately one square inch of the test material. If the wetting solutions stay intact for more than two seconds then the threat level is at least as high as the dyne level of that solution.
Repeat the procedure until a solution is used that will bead up on the surface of the material that is being tested. The film treat level would be identified as the last solution level that remains wetted out on the surface. While a clean cotton applicator must be used for each dyne solution to avoid contamination of the solutions that may distort the results.
The cotton swab applicator method is being used for many years but is still somewhat subjective and inconsistent because of the variables. Although this test should be performed in a lab environment because of the risk of spilling the contents.
The Draw-Down Test Method
This test is known as the most accurate one where a substrate sample which measures 8 1/2×11 inches is clamped to a clipboard. At the top of it, a single drop of three different level dyne solutions is placed horizontally from each other. Then a wire wrapped metering rod is placed just above the droplets and pulled down. When the film of liquid breaks within the two second period the tester knows that the treat level of the film.
The draw-down test method is more accurate because the metering rod lays the solution down at the same relative thickness.