Plastic is an amazing material with many wonderful properties and varied uses but it can be really tricky to print or label on because of its low surface energy.
One thing that has not changed is the fact that printing on plastic substrates is different than printing on paper. Plastic substrates do not absorb as paper does. Therefore inks, varnishes, and coatings will lie on the surface of these nonabsorbent substrates, and not be absorbed. Furthermore, the surface of plastic materials lacks in bond sites for printed/coated products and foil stamping adherence.
The need to print on plastics is becoming increasingly necessary for many businesses. See our successful applications here.
SURFACE PRE-TREATMENT IS CRITICAL
Most likely the most critical factor in printing on plastic substrates is its surface energy. Surface tension is measured in terms of the dyne level. When printing on plastic substrates, it is critical that one understand this property and its implications at different levels. The surface energy of plastic is the ability of its’ surface to attract a liquid and allow it to wet out the surface.
Experienced printers of plastic substrates understand that the dyne level must be between 38 and 50, with 40 thought of as ideal in order to expect acceptable printing results. If the dyne level is below 38 the inks will not adhere. On the other end, if the dyne level is over 50 there will be handling problems relating to static electricity. Plastic substrates with a dyne level measured below 38 may be printed acceptably, but only after adequate surface treatment.
