• Whenever feasible, test with supplies, samples, and ambient
temperature at 20o to 25oC. 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.
• 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 a full-size drawdown. 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 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.
• Cleaning systems can be monitored by the dyne test. The
surface energy of metals is much higher than that of surface contaminants;
thus, the higher the dyne level, the cleaner the part is. Always
use test fluids to measure cleanliness — even our spring-loaded
valve tip markers will eventually be overwhelmed by repeated exposure
to contamination.
• The presence of mold release on many plastic parts can be
similarly identified. Again, test fluids are indicated for this application.
