Choosing the right vinyl product for the application can be difficult. Starting with the basics of manufacturing and product differences, we’ll explain when you should use a cast vinyl or a calendered vinyl, highlight the risks you introduce in mixing vinyl types and the results of mixing.
Cast Vinyl
The term “cast refers to the manufacturing process of the vinyl film. Cast film is made by pouring a liquid mixture of solvents, colour pigments, plasticisers and resin, known as ‘organosol’ onto a web or ‘casting sheet’ and baked, like a cake, in an oven. During the baking process, the solvents evaporate leaving behind a consistently thin film that remains stable with no molecular memory. The casting sheet is then separated from the film before the adhesive coating is applied. If a gloss, matte or satin finish is required, the casting sheet used will have that finish.
Features of cast films include:
Very high gloss levels
Consistent paint-like finish
Broad colour pallet with high performance pigments
Able to produce custom colours in small production quantities
Excellent conformability
Excellent dimensional stability
Outstanding UV protection
Long outdoor durabilities
Perfect for application on compound curves, rivets and deep channels
Calendered Vinyl
Calendered vinyl is made by extruding a molten paste of PVC, plasticisers and resin through rollers or ‘calenders’ that squeeze and stretch the mixture out to the desired thickness, thus affecting the molecular memory of the PVC. PVC in its “natural” form is a rigid material, so additives known as plasticisers are added to the mix to make it pliable. Other additives included in the mix are pigments to add colour and stabilisers to reduce the effects of heat and UV. If a gloss, matte or stain finish is required, the rollers used will have that finish. The output of this manufacturing process results in a thicker, easier to handle film with unstable molecular memory, i.e. the shape has changed during the manufacturing process. There are two types of plasticisers used to make calendered vinyl – polymeric and monomeric.
1. Polymeric plasticisers have a longer, more complex chain-like molecular structure than monomeric plasticisers. Polymeric plasticisers integrate better with the vinyl molecules and are less vulnerable to extreme usage conditions.
Features of polymeric calendered films include:
High gloss levels
Large colour selection
Slight conformability
Moderate dimensional stability
Moderate UV protection
Durabilities up to 3 years outdoor
Perfect for applications on flat surfaces and simple curves
2. Monomeric plasticisers have a simple, linear-type molecular structure that mix with the vinyl molecules for a limited period before migration out of the PVC.
Features of monomeric calendered films include:
Medium to high gloss levels
Smaller colour selection
Little or no conformability
Low dimensional stability
Low UV protection
Perfect for applications on flat surfaces only
Durabilities up to 2 years
Now you know a little bit about how vinyl is made and their characteristics, it is important to know what that means when choosing the right product for your job an why you shouldn’t mix different film constructions.
Cast films are know as premium or high performance films, They are more stable, with no molecular memory. When installed with heat their molecular memory is set, meaning the film will stay in place even in the most complex curves. This dimensional stability makes cast films ideal for challenging applications on boats, passenger and transit vehicles, while the durability of these films make them perfect for applications where the graphic is expected to last a long time.
Calendered films are know as intermediate, short term or economic films. They are less stable and have a built in molecular memory. They are more prone to shrinkage, cracking and peeling especially when exposed to heat and UV, and is intensified when stretched. With this limited dimensional stability, calendered films are suitable for applications on flat surfaces, or on simple curved for polymeric films, while the durabilities affect the longevity of the sign and the application environment.
The three film constructions (cast, polymeric calendered and monomeric calendered) are extremely different, as such the mixing of film types is not recommended. Due to different rates of shrinkage and product conformability, combining the constructions is likely to result in shrinkage, edge curl and layer separation or delamination. Most manufacturers have developed matching overlaminates for their face films, meaning the physical properties of both components are compatible.
Most manufacturers warranties will be void if the film constructions are mixed, particularly when pairing a lower grade film and higher grade film.
What should we do to reduce the risk? As a rule, a cast film should be paired with a cast film or overlaminate; a polymeric film should be paired with a polymeric film overlaminate and a monomeric film should be paired with a monomeric film or overlaminate.