Learn the basics for printing on two popular plastic materials used in display applications.
By Omer Shoham
Most plastic sheets perform superbly in a wide range of graphics applications and can be used to create weather-resistant signs, displays, or P-O-P materials. Their smooth surface is ideal for all types of graphics, and they require little surface preparation or treatment. This article focuses on polycarbonate (PC) and polyvinyl chloride (PVC), both of which are commonly used for signage and graphics.
The surface of PC or PVC sheets should be cleaned before printing. Isopropyl alcohol and a clean cloth can be used to clean the surface and remove static electricity. Depending
on the specific application, certain pre-treatments may also be required.
The screen-printing process is relatively simple when working with PC or PVC. The surface of PVC has a closed-cell, matte finish that allows mistakes to wipe off easily with the appropriate thinner. Vinyl and vinyl/acrylic, solvent-based inks are compatible with foam PVC. Only acrylic-based ink may be used with PC. The use of water-based screen has also had some success with PC/PVC material, but you must follow directions from ink manufacturers very carefully. Surface preparation of PC/PVC for screen printing is similar to those of painting.
The surface to be screen printed must remain dry, clean, and grease free. Any surface scratches on the PC/PVC will have a tendency to show as a shadow through the ink.
It is highly recommended that the surface be cleaned with a white cloth moistened with isopropyl alcohol prior to printing. All screen-printing inks should be tested in a manner that duplicates your printing process before initiating production, especially when using PC. It is strongly recommended to consult the appropriate ink manufacturer regarding any required ink additives, such as a catalyst, for proper adhesion and exterior usage.
Screen-printing ink should air dry, rather than be heat dried. Temperatures in excess of 150°F may cause warping or bowing of foam PVC material; PC is suitable for high temperatures. All UV screen-printing inks that are compatible with rigid PVC will work on foam PVC. The most important factor to be considered when using UV systems is the curing oven. Low-wattage bulbs should be used to keep the temperature below 150°F. UV curing systems that have variable-speed conveyors are considered the best type to use with foam PVC.
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