APR Techtips


For the results of this test to be meaningful, the following four points are absolutely essential and must be followed:

  1. Do not touch or in any way contaminate the surface to be tested. Dirty surfaces lose their wettability.
  2. Do not use contaminated or outdated ACCU DYNE TEST™ marker pens.
  3. Never retest the same location on a sample; move along the sample, or pull a new one.
  4. Be sure to pull a good test sample; surface aberrations cause poor results. For extruded film, one entire web cross-section should suffice. Do not touch the surface.

Testing the sample

Place the sample on a clean, level surface. If necessary, anchor the edges to avoid curling or other deformation.

Test at least three points across the sample; 1/4, 1/2, and 3/4 across the film section. It is good practice to test the outer edges as well. For non-film materials, test locations must be determined in-house.

Whenever feasible, test with supplies, samples, and ambient temperature at 20° to 25°C. If this is impossible, it is advised that a test study be run to relate temperature variations to numerical results. Keep test supplies at ambient temperature at all times. Record ambient temperature and relative humidity. If sample temperature differs from ambient, allow it to stabilize.

Choose an ACCU DYNE TEST™ marker pen of a dyne level you believe is slightly lower than that of the test sample.

Press applicator tip firmly down on subject material until the tip is saturated with ink.

Use a light touch to draw the pen across the test sample in two or three parallel passes. Disregard the first pass(es); to flush any contamination from the tip, and to ensure that the test fluid layer is thin enough for accurate measurement, evaluate only the last pass.

Other things to remember

  • Film extruders should test extensively — every roll from every machine without fail. Potential product liability and customer satisfaction losses far exceed the cost of an effective QC program. We strongly recommend using test fluids, preferably with the ACCU DYNE Applicator™ or a #3 metering rod. Alternatively, ACCU DYNE TEST™ Marker Pens can be used, with laboratory contact angle tests used as a backup audit.
  • Remember that dyne level decay is extremely rapid directly after corona treatment. A virtually immediate loss of 10 dynes/cm is possible! This is due to contact with process rolls (especially heated metal ones), surface blooming of additives, and interfacial transfers between treated and untreated surfaces within the finished, wound roll. If you are a slitter, rewinder, or extruder, either test far downstream in the process, or increase your specification to account for greater losses before your customer tests at incoming inspection.
  • It is often possible to identify patterns of treatment variation on a sample piece by doing drawdown tests. Methodical troubleshooting analysis will often lead back to the specific cause. For example, increasing treatment across the roll suggests the treater electrode is misaligned to the roll; periodic variations along the web may relate to non-concentricity.
  • An easy test for back-treat on PE or PP is to use a 34 dyne/cm ACCU DYNE TEST™ Marker Pen. Any wetting — even for less than two seconds — indicates some treatment.
  • Test fluids or markers which have turned green or seriously lose their color density are no longer reliable. We guarantee against this up to the expiration date (five months for fluids, six months for test markers).
  • Never leave bottles or markers uncapped! Evaporation, water vapor, and airborne contaminants all affect dyne level, and can invalidate them long before expiration.
  • Printers, coaters, and laminators should pull samples and perform the test as soon before the print station (or similar) as possible. It may be worthwhile to dyne test the roll before it goes on the machine, and compare these results to material which has run through the web handling process to the print station. This will indicate the treat loss attributable to process roll contact and web handling.
  • Polyester film which reads consistently below 42 dynes/cm is almost certainly "print primed." This chemical process actually decreases the surface energy a bit, but makes the surface attractive to a far broader range of compounds used in inks and coatings.
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