Tips for printing on polyester by Tom Rittman, Technical Service Manager Email: rittman@plasticsuppliers.com

When done correctly, printing on plastic offers printers of all types a way to set themselves apart from their competition.  Polyester film is one of the most common and versatile plastics available to the printing industry.  These films are used for calendars, labels, membrane touch switches, and many other graphic art applications.  Here we will answer some of the most common questions you have when printing on polyester.

Q: What factors should I consider to make printing on polyester film more successful?
A:  Many things impact the success of a polyester film-printing job.  Two particularly important factors are 1) the surface energy of the ink and print surface and 2) getting the ink to adhere to the film.

Q:  How do I tell if the ink and the print surface are compatible for surface energy? 
A:  Test for the dyne level of the film surface to be printed.  The dyne level of the film should be higher than the dyne level of the ink.  If the dyne level of the ink is too high, the wet ink can reticulate or “bead up,” creating an uneven wet ink coating and eventually leading to an inconsistent color density in the dried ink.  If necessary, ink dyne levels can be raised or lowered by adding special liquids and solvents.  (The table below gives you the typical dyne levels for most polyester film types.)

Q: How can I get adhesion between the ink and the polyester film?
A: For ink to adhere to a surface, the wet ink must first soften the surface being printed.  Untreated polyester film has a very inert surface, but solvents found within polyester resin inks can soften it.  Adhesion pretreated films work well with acrylic, vinyl, and some UV ink systems while corona treated film works better with water based and acrylic inks.  Inks can also be modified with specific solvents that more aggressively soften the polyester film surface.

Q:  Where can I get more assistance?
A:  Your ink manufacturer is your best information source regarding compatible solvents with a particular ink system.  Each printing process is different and modifications vary greatly.  If needed, your Plastic Suppliers sales representative will provide you with the names of ink manufacturers that have ink systems for use with polyester films.