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:
plasticizers 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
plasticizers 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
plasticizers 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 plasticizers. The combination of these factors
greatly determines the durability of vinyl 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 conform-ability 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 conform-ability 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.
Advantages of cast films:
• Shrinkage is the lowest of all vinyl films because the
"casting sheet," not the film itself, is pulled through the
machine. Since the film has not had any stress applied
during the manufacturing process it does not try to
resume or shrink back to its original form.
• Durability of cast films is generally higher than that of
other vinyl films due to the manufacturing method and
the raw materials used.
• Cast films can be made very thin which produces a
conformable product that allows application over
substrates with rivets, corrugations, and complex
curves. Also, once applied, this low caliper makes the
graphic less vulnerable to abrasive forces.
• Cast films also maintain their color and other properties
better than other vinyl films. This results in better
performance of pigments and UV absorbers.
• The manufacturing process of cast films makes it easy
to run small productions of special colors to match. It is
relatively easy to change color during production
making color matching in small batches possible.
Like cast, calendered film also
gets its name from the
manufacturing process. These
films may also be referred to
as intermediate, 4 mil, short term
or economy. Calendered
vinyl is formulated with similar
raw materials as cast, except
that no solvents are used. The
batch is mixed and heated to a molten state that resembles
pizza dough. Once the film reaches this molten state it is
extruded through a die and is then fed through a series of
calendering rolls. These polished steel rolls progressively
squeeze and stretch the vinyl into a flat sheet (similar to
flattening out dough with a rolling pin). Because the film is
stretched into shape, it has some degree of memory and
therefore is less dimensionally stable than cast vinyl films.
This means that when a calendered film is exposed to heat
the film will have a tendency to shrink or pull back towards
its original form. Calendered films also tend to be thicker
(usually 3.2 to 3.4 mils) than cast films because of the
limitations of the calendering process. Unlike casting where
a textured or smooth casting sheet is used to produce the
film finish, calendering implements a special finish cylinder at
the end of the process while the film is still warm. This
process is extremely fast and is ideal for bulk production
runs. Therefore, color matching is very unattractive on these
machines. However, due to its bulk production with high
yields, calendered films are relatively inexpensive.
The quality of calendered films can range from economy to
intermediate with durability of one to five years. These films
generally are not recommended for vehicle applications
because they are thicker, less conformable and less durable
than cast films.
Advantages of calendered films:
• Greater production yields equals less cost
• Stiffer/thicker film equals easier handling
• Thickness of film increases resistance to abrasion
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. Calendered films
are ideal for applications that do not require the film to
stretch or conform around contours. Examples of calendered
film uses would be floor graphics, wall murals, and point-of purchase