Adhesive Applications Hints and tips for using Dyne Pens
Getting the best out of surface energy measurement - Alison Fox, sales manager, Dyne Testing
I
f you are printing, painting, bonding or sealing, good adhesion is an essential issue. If you do not understand the surface energy of the adhesive material and the substrate, and the diff erence between them, you risk issues with wetting, the quality of adhesion and complete coating coverage. This applies in material and substrate specifi cation phase, where you might want quantitative data. In the production phase, checking surface energy can help you determine process failures or other unintended surface changes.
Dyne pens are handheld surface energy analysis tools that can be used in any environment on solid substrates. They are available in diff erent “Dyne” levels. When a Dyne test pen is applied to the surface, the ink will either form a continuous fi lm on the surface or pull back into small droplets. If the liquid remains a fi lm for three seconds, the surface energy of the substrate has a minimum value of that Dyne pen ink value. If the ink draws back, then the surface energy of the substrate is lower than that of the ink. To help get the best results from Dyne pens, here are some hints and tips:
AVOIDING CONTAMINATION
Common mistakes when using the pens include testing on a contaminated area of the material. It is important that tests take place on areas that have not been handled. If users test on areas contaminated by fi ngerprints, the results will likely be inaccurate and
inconsistent across the material. This leads to rejections, wasted resources and reduced productivity. Visual checks are usually enough to identify contamination like grease marks, dust or fi ngerprints. Testing in these areas will not give a true analysis of the underlying substrate’s surface energy. It is good practice to test in three areas of the substrate sample; inconsistent results will indicate some form of localised problem, like contamination, surface treatment failure, etcetera, whereas identical results will give confi dence in the validity of the measurements.
We recommend that tests are conducted at room temperature and humid environments are avoided. Evaporation, water vapour and airborne contaminants can all aff ect the Dyne level result. For the same reasons, we recommend that Dyne pens are stored at ambient temperatures with the caps on to ensure complete shelf life.
PEN CHOICE
It is a good idea to use Dyne pens with a “valve tip” applicator, a type of pen that has a non-return valve. When pressing the tip fi rmly down, the valve is opened and fresh ink fl oods the applicator tip. The valve protects the testing ink inside the pen from humidity and from substrate contaminants which could otherwise wick up into the ink reservoir. It also means low levels of evaporation of volatiles from the ink and prevents ink leakage. Unlike those based on
a normal felt-tip marker pen, the valve tip applicator protects the ink and its integrity, keeping the results accurate for the lifetime of the pen and ensuring the best shelf life.
MATERIAL USE
While Dyne Pens are suitable for most non-absorbent materials, including on polyethylene and polypropylene fi lms, it is important for users to initially test on scrap substrate. This is to check the ink from the pens does not adversely react with the material being tested, soak into the material or cause it to swell. On soft grades of PVC, the ink from the pen can react with the polymer and cause inaccurate results. A chemical reaction between the test fl uid and the substrate invalidates results altogether. It is important that the test fl uid does not alter the substrate’s surface properties. For example, if the test fl uid permeates a fi bre substrate, such as paper, and causes swelling, results will indicate unrealistically easy wetting.
TIMING IS EVERYTHING
The standard procedure entails applying the test ink and watching to see if it wets the substrate and for how long. An accurate test result will be with an ink that stays in a continuous fi lm for between one and three seconds. If the ink stays wetted for more than three seconds, using a higher Dyne level test pen is indicated to narrow down the actual surface energy.
24
March 2025
www.convertermag.com
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