What Causes Ink Adhesion Problems?

When screen printing polycarbonate film, learn what causes ink adhesion problems.

The $64 question is: what causes ink adhesion problems when screen printing polycarbonate film?  While some have suggested moisture absorption as the culprit, the most likely candidate is exposure  to UV light and oxygen.  As the polycarbonate absorbs UV light, it excites the photons of the atoms, which in turn creates free radicals. Free radicals are atoms with a few extra electrons. These extra electrons make free radicals highly reactive, or what I like to think of as being chemically promiscuous.   These free radicals chemically react with any impurities in the polycarbonate film,  such as sodium. The result of this reaction is degradation of the polycarbonate. This is why the film can yellow and become brittle.

Surface Degradation

Degradation can occur with or without oxygen. With it, though, the problem is much worse. Here’s why. The oxygen reacts with the polycarbonate breaking the molecular chain especially where one carbon atom bonds with another carbon atom or with an oxygen atom. Without oxygen, degradation still occurs because UV radiation initiates cross linking.  This process is called photo-oxidation.  The by-products of these chemical reactions are the creation of H2, H2O, CO and CO2. 

As  polycarbonate oxidizes, the surface breaks down.  As the outer layer or skin of the film degrades, it becomes very weak and molecular debris accumulates on the surface.  When older polycarbonate film is screen printed, the loose debris forms a barrier between the unaffected  part of the film and the ink.  Because the ink adheres to this debris, ink adhesion is poor.

Other Screen Printing Articles

Screen Making: The Direct Emulsion Method
Tips for Screen Printing on Polycarbonate Films
Screen Printing Acrylic Sheet

About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.

© 2015 Jim Hingst