While cast vinyl films remain popular for printed graphic applications, less-expensive calendered vinyl is now overtaking them in much of the market, according to research by vinyl wholesaler Instant One Media.
Many signmakers and other professionals still consider cast film the best choice for vinyl applications, but new manufacturing technology has helped improve the quality of calendered films. In the past, calender-based vinyl film production tended to result in thick materials that could only be applied to flat surfaces. Now, calendered films are thinner, shinier and more shrink-resistant, such that signmakers are using them in a wider range of graphic applications.
The process of manufacturing a calendered film involves mixing polyvinyl chloride (PVC) with a plasticizer to create a flexible material, then mixing in other additives—such as oils, stabilizers, dyes and processing aids—to add the desired physical attributes. As such, the raw materials chosen for the production process depend on the purpose of the film to be formulated.
Once mixed, all of the necessary raw materials are fed into an extruder, which blends them further into a liquid. This is transported via convey belts to a ‘refinery,’ comprising two rolls rotating in opposite directions to generate sufficient heat and pressure to flatten the liquid mixture into a more uniform configuration.
After this uniform mixture is scanned with a metal detector, to find and remove any metallic impurities, it is sent through calendered rolls to flatten it to form the film. As it passes through several more gaps, the temperature and uniformity increase, making the film thinner and wider. The exact number of gaps the mixture passes through is dictated, again, by the specifications for the intended application.
Once the desired size is achieved, the film is passed along to an embossing station, where it is decorated by rolls to add patterns and sheen. The film is allowed to cool before the last stage, ‘winding.’ During this stage, the film’s thick edges are trimmed to ensure true uniformity of depth for cutting, quality control and shipping.
Calendered vinyl manufacturers have continued to improve their production procedures, incorporating better basic additives to enhance the performance, lifespan and colour consistency of their films. New control systems have helped improve uniformity of thickness, gloss and colour.
While the resulting calendered films cannot completely substitute for cast films in all cases, they have made progress in some areas that were previously dominated solely by cast films, including highly demanding applications like vehicle graphics.
