In the textile industry, surface tension testing (DYNE) is critical in helping us where there are concerns of quality and consistency over bonding, film and material production. Bottom line, without proper testing and verification methods, you won’t discover there’s a problem in seam sealing tape or reflective tape until post production – often that happens at the consumer level and then it’s too late.
Not only do you wind up with unsatisfied customers, but botched production tends to be environmentally unfriendly.
Think about it from the perspective of car insurance. You don’t purchase car insurance to cover you because you’re a bad driver. It’s there to support you. Like automotive insurance, proper surface tension testing or DYNE testing simply insure that substrates are properly treated and produced to spec/standards.
These standards of testing textiles have been around for decades, it’s certainly nothing new. For some companies, it merely consisted of a contact angle measuring device with liquid. For example with a some material you likely would see a droplet supporting adhesion as the droplet is wetting outward. This creates a low contact angle.
With untreated textiles, the droplet would cling to itself rather than the surface, and would result in a taller droplet with a higher contact angle. Of course this type of testing isn’t practical anymore which is why we use more current DYNE testing solutions. The concept is that we test or pre-check surfaces to ensure that they will bind together and support adhesion, such as with our bonding films and their various applications.
Bonding of Seam Sealing Tape and Reflective Tapes – DYNE Testing
Surface tension is the property of a liquid arising from unbalancedmolecular forces at or near the surface. If it is higher than the surfaceenergy of a material, the liquid tends to form droplets rather thanspread out or “wet out” as some refer to it. Surface tension is normallymeasured in energy units called dynes/cm. A dyne is the amount offorce required to produce an acceleration of 1 cm/sec² on a mass of 1gram.
The DYNE level of material is known as its surface energy. If the liquid used for testing has a DYNE level lower than the material’s surface energy, then the liquid spreads over the surface in a uniform wetting layer.
If the ink’s DYNE level is equal to or higher than a material’s DYNE level, then the liquid becomes cohesive and remains in droplet format.
For quality assurance purposes, DYNE pens were developed – mainly because bottled testing liquids were never really “shop floor friendly”. The pens are similar to a felt tipped highlighter and contain the same solutions you find a lab test environment. When the tip is swiped across the surface of the textile, the results are interpreted in the same manner as a solution with a cotton swab in a lab. It really just boils down to a matter of convenience.
Testing Seam Sealing Tapes & Textiles – The Downside of Pens
One thing to note is that quick-drying pens used in some areas of the textile industry should be considered to be potentially inaccurate. This is because the liquid is alcohol based. Because of the fast-dry nature, older pains begin to dry out and as they do so, they may appear to give favorable results when in all actually the test is not entirely accurate.
Testing Tips – Solutions Conforming to ASTM standard-2578
• Spread the test fluid from the felt tip pen lightly over an area ofapproximately 7 cm of the test specimen, noting the time it takes forthe continuous film of ink to break into droplets.
• Breaking of the fluid into droplets in less than 2 seconds indicates alack of wetting and a lower numbered test fluid should be tried.
• If the fluid remains intact for longer than 2 seconds, a highernumbered test fluid should be tried.
• The aim is to establish the lowest reading at an optimum dwell timeof 2 seconds.
• Extreme care must be taken to ensure the film surface is not touchedor contaminated in the areas in which the tests are to be made.
• We recommend the replacement of the inks regularly if the bottledinks are frequently opened to atmosphere.