Cast vs Calendared Films, What's the Difference?

Buyer beware!!! Let's face it, Wraps n Signs isn't the only choice out there for vinyl wraps and decals. We've been all over the internet looking at what other sites offer in their wrap materials. In most every case the sites or listings either do not mention at all what kind of film they use or mention that they use calendared films. That's a huge problem if you have no idea what cast or calendared films are. Since this industry is still fairly new it's very easy to offer less quality products since the client has no idea about grades of the film and how they perform in the long run. Yes, you can put a high performance calendared film down and it will look fine for a time, but WILL eventually start shrinking and not look as good in the long run as a high performance cast film will. So when you are talking about one of your most expensive investments, your ride, isn't it a good idea to know that you are putting the best materials possible on it so that is will perform for the long haul? Of course the answer is yes!

As with anything else, the finished product is only as good as what you put into it. This begins with choosing the right vinyl for the job. If you are doing a full vehicle wrap where you want the graphic to conform so that it looks and performs similar to paint you should choose a material with these characteristics, which would be cast film. Calendared films are ideal for applications that do not require the film to stretch or conform around complex contours. Examples of calendared film uses would be floor graphics, wall murals, window graphics, partial wraps and point-of-purchase displays.

Cast Films
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 precisely metered 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 12 years depending on how the film is processed.

Calendared Films

Like cast, calendared film also gets its name from the manufacturing process. The production of calendared film is similar to mixing and rolling out a pie dough. It is formulated with similar raw materials as cast. These 'ingredients' are mixed and later 'kneaded' in the extruder. Instead of grandma's rolling pin, gigantic heated, steel rollers form the vinyl into a thin sheet. This process is called 'calendaring'.

The first step is 'paste mixing' and 'extrusion': here all raw materials (e.g. PVC powder, liquid softener, colors) are mixed together based on the formulation. Improved formulations and the use of new pigments lead to increased color options for calendared film. In the extrusion process the prepared fine powder mix ('dry blend') will fuse together into a homogenous mass, called the melt. The next step - the mill - consists of two counter rotating rolls, which can be heated up to 350 °F. The melt is continuously pulled into the gap and flattens out due to the pressure and temperature that is applied by the mill rolls. When the strip reaches the calendar rolls, it passes between multiple gaps which increase the temperature and uniformity. After each gap the film becomes thinner and wider according to the specifications. The film is still heated when it reaches the embossing station where different pattern and gloss levels are applied to the film. Each surface structure requires a different embossing roll - e.g. to produce a high gloss film a different embossing roll is required but also a special setting of the whole calendar line. Now that the film has received its final dimensions and surface it needs to be cooled down and transported to the last process stage of winding.

From the extruder to the winder a calendar machine can be 90 feet long. Due to improvements made in the manufacturing process, calendered film can be produced as thin as 2.0 mil.

The quality of calendared films can range from economy, which use a monomeric plasticizer, to a high-grade which would use a polymeric plasticizer. The durability of calendared films can range from one year up to seven years.