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It is safe to say that most people may not know the actual ingredients or manufacturing processes for these films. They do, however, know that a short-term or economy film should not be used for a vehicle wrap and that a cast or high-performance film is overkill for a point-of-purchase (POP) display that will only be used for six months to one year. This article will explain the differences between cast and calendered films as well as give examples of where each type of film would be used.
What Makes Vinyl Vinyl
Let's begin with a few of the basics on vinyl films. Most vinyl films are made from the same basic raw materials. We begin with polyvinylchloride (PVC) polymer, which is simply basic plastic, and is, by nature, relatively rigid. Other ingredients are then added to the PVC. These ingredients include: plasticizer to make the film flexible, pigment to make the desired color, and additives to help achieve specific properties such as UV absorbers to improve resistance to UV radiation, heat stabilizers, fillers and processing aids. These raw materials can be chosen from a wide range of quality levels. Of course, for a film with limited durability, often the least expensive raw materials are chosen.
Apart from the type of raw materials that are used at manufacturing, the manufacturing process and the type of plasticizer used create the main differences of vinyl films. Vinyl films can either be made by calendering or by casting. Each of these processes renders different qualities of films. Casting generally results in better quality films. The grade of plasticizer that is used to make the film flexible also greatly affects the grade of the film. Generally for pressure-sensitive adhesive films a choice is made between polymeric and monomeric plasticizers. We won't go into detail on the plasticizers in this article, but for simplicity's sake consider polymeric to be the higher grade and monomeric to be the economy grade plasticizer. The combination of these factors greatly determines the durability of vinyl films.
Cast Films
Cast films, also known in the industry as premium, high-performance or 2 mil are considered to be a premium product with excellent durability and conformability characteristics. The term "cast" refers to the manufacturing process of this type of vinyl. Making a cast vinyl film is a lot like baking a cake. The vinyl begins with a "recipe" calling for a list of ingredients known as the formulation. These materials are added to a "bowl" or mixing churn in a predetermined order while mixing at specific speed and for a set amount of time to ensure a complete and consistent mixture. This liquid mixture, known as organosol, is then "poured" or cast onto a moving web known as the casting sheet and is then processed through a series of ovens which allows for the evaporation of solvents. When the solvents are evaporated, a solid "film" is left behind. The film is then wound up in large-diameter rolls for subsequent adhesive coating. The casting sheet determines the texture of the film.
Because the vinyl is cast on the casting sheet in a relaxed state, this material offers very good dimensional stability. This process also allows the film to be very thin (most cast films are 2 mil), which helps with the conformability of the product. Material manufacturers recommend the use of cast films on substrates such as fleets, vehicles, recreational vehicles or boats where the customer wants a "paint-like" finish that will last a long time, usually five to eight years depending on how the film is processed.
Michael White
DFR Sales
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