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Vinyl in the Making

Characteristics of Cast and Calendered Vinyl

By Amber E. Watson

 

The durability, affordability, and versatility of vinyl make it a popular material for common applications such as vehicle wraps, signs, and displays. The choice between cast and calendered vinyl is often determined by the physical differences between the two, and this process begins with the way each is manufactured.

 

Cast vinyl is typically thinner and features low-shrinkage characteristics. It offers flexibility and conformability, but comes with a higher price tag. Ideal for shorter runs of custom products, it is available in a variety of finishes.

 

Calendered produces a stiffer product at a lower cost. No solvents are involved in the processing and calendered runs faster in the manufacturing process.

 

Despite differences, it is important to note that the gap between vinyl is closing. Calendered rivals cast in that it is now thinner, glossier, easier to conform, and often provides cost savings.

 

The Raw Materials

The difference between cast and calendered vinyl begins in the manufacturing process and carries through to end use.

 

“Cast and calendered vinyl is more or less made of the same raw materials,” explains Laura Schied, marketing manager, American Renolit Corporation. “To create vinyl, polyvinyl chloride (PVC) is mixed with plasticizer along with other additives such as UV and heat stabilizers, pigments, and processing aids. Although PVC is the primary ingredient, each additive plays a specific and vital role in changing the properties of the vinyl.”

 

The difference between cast and calendered in terms of raw materials is that in the production of cast a diluent is used, which is not necessary for calendered vinyl. In turn, calendered vinyl requires additives to reduce the adhesion to the calender cylinders.

 

Cast vinyl manufacturers use more costly, automotive-grade pigments and heavy, stable plasticizing oil. “It retains the weightier oil throughout its life, which keeps it flexible. By comparison, calendered is lighter, more volatile oil can eventually leech out, leaving it brittle,” shares Jim Hingst, business development manager, RTape.

 

During the process of manufacturing cast vinyl the raw materials start as a liquid, and are mixed and poured onto the cast roller and processed onto the casting paper. “Cast vinyl is made from a solvent dispersion of the vinyl resin and plasticizer. The liquid is cast onto a controlled gloss or matte carrier sheet and then dried in an oven,” says Robert Rundle, viscom market manager, Ritrama. “Calendered vinyl is a 100 percent solid blend of the vinyl resin and plasticizer. The blend is heated so that it flows and is extruded onto the calendering rolls.”

 

Cast Vinyl in the Making

During the casting process, the plasticizer bonds with the PVC resin and provides the cast vinyl with its low tensile strength, durability, stretchability, and conformability. This allows it to better cover substrates with rivets, corrugations, and textures.

 

Because cast vinyl is placed onto a casting sheet, which bears the tension during the process, it experiences less stress, making it more dimensionally stable. “Because cast vinyl is not stretched during the manufacturing process it is not oriented; as a result, it is softer and more conformable,” notes Jodi Sawyer, market development specialist, FLEXcon.

 

Chad Russell, director of business development, Arlon Graphics, LLC, agrees that cast vinyl is typically more conformable, durable, and consistent. “Casting vinyl allows the manufacturer to control more variables, which means it is formulated for the exact application in question,” shares Russell. “It goes from a highly engineered formula of liquid PVC directly to the finished vinyl rolls.” This means better stability and more performance.

 

Cast vinyl is also thinner than calendered, and according to Molly Waters, technical specialist, Avery Dennison Graphics Solutions, the cast process provides more of a paint-like finish when applied, while calendered is thicker and stiffer, she continues.

 

There are other characteristics to consider as well. Marcel Medved, business development director, Americas, ATP Adhesive Systems, believes that cast vinyl offers greater stretchability, uniform shrinkage in both directions, and is more weather resistant while calendered vinyl—due to the extrusion/calendering process—features a more bi-directional behavior in shrinkage.

 

Manufacturing wise, however, calendered vinyl is more economic and ecological because cast is coated out of a solvent solution of PVC, where the solvents have to evaporate.

 

“A cast vinyl produced from a liquid dispersion requires a carrier on which to be produced. This carrier, either a specially coated paper or polyester, is removed prior to packaging. The paper is re-used several times but the polyester is thrown away,” says Schied. “A second reason for higher cast vinyl cost lies in the manufacturing speed—for calendered, the production speed can be a few times higher than with cast.”

 

Calendered Vinyl in the Making

Calendered vinyl, which gets its name from the large steel rolls on which it is processed, is made in higher quantities and used across many different brands and industries. Because it is extruded, it is more likely to have shrinkage and shorter life, but this also makes it an affordable option.

 

Robert Hinsch, VP, Top Value Fabrics, outlines the manufacturing process. “Calendered vinyl starts as a mixture of various solutions including soft resins, plasticizers, and stabilizers. This mixture is blended, heated, and pressed through a series of calendering rolls and then laminated onto a scrim to make a calendered vinyl laminate.”

 

Throughout manufacturing, the large series of calendering rolls determine the smoothness of the finish, as well as the gloss or matte capabilities achieved.

 

“The manufacturing process for calendered vinyl works from a 100 percent solids format, meaning no solvents or casting sheets are involved,” states Jeffrey Stadelman, technical marketing manager, MACtac Graphic Products. “The basic ingredients, as with cast, are mixed together at a moderately high temperature into a dough-like consistency and then fed into a series of calendering rollers, which further processes the PVC to the right width and thickness. Finally, the ingredients go through another series of rollers that use a heat and cooling process to set the vinyl into its final form before being rolled up for further processing.”

 

Calendered vinyl is thicker due to limitations of the manufacturing process, which imparts improved stiffness to the material. “It can be processed at higher speeds than cast vinyl and is designed for longer runs, which provides an economic advantage,” notes Sawyer.

 

A Place for Each

Cast and calendered vinyl are each ideal for particular applications and ink sets.

 

The conformability and durability of cast makes it well suited for longer term applications with compound curves and riveted surfaces. “Traditionally, these are applications such as fleet graphics, vehicle wraps, and bus and train wraps with corrugation. Today, however, new buses, trains, and fleets have fewer rivets and corrugation, reducing the need for a cast vinyl solution,” notes Sawyer.

 

Russell recommends cast for any application that demands long outdoor life or one with curved or three-dimensional surfaces. This is attributed to the lack of memory in the media from the manufacturing process.

 

According to Waters, newer cast vinyl lasts longer, some up to 12 years, and conforms easily to curves, rivets, and indentations, while calendered vinyl’s thicker and stiffer properties are most commonly used for temporary projects or projects with a flat surface and shorter lifespan.

 

Depending on the grade of calendered vinyl it can have a relatively short life of up to one year, or a durability of five to six years.

 

Calendered vinyl is well suited for short- to medium-term applications such as bus posters and wraps, taxi tops, subway posters, graphics on windows, point of purchase signage, counters, floors, and walls. “With advertising changing more frequently to attract today’s mobile consumers, the cost advantages of calendered vinyl make it the ideal choice for brand promotion,” says Sawyer.

 

Calendered vinyl is also available in a wider range of mil thickness ranging from 2.8- up to 12-mil, and with film laminations up to 25-mil.

 

While calendered vinyl is not intended for permanent applications, laminates can be tough and durable for long-term advertising campaigns. “Depending on the finishing, during the manufacturing process, calendered vinyl can have a smooth finish and superior printing capabilities for viewing at close distances,” says Hinsch.

 

Cast vinyl, according to Craig Campbell, graphic products market manager, Orafol Americas, can usually withstand solvent penetration better for higher production runs and typically offers an improved printing surface to accept any ink type. This is primarily due to the better raw materials used in production.

 

“Both mediums work well with most solvent, UV-curable, latex inks, and thermal inks, but this depends on the plasticizers, which are used for both cast and calendered,” agrees Medved.

 

Tim Roche, product developer, Griff Paper & Film adds, “ink adhesion and overall performance typically comes down to the softening agents, or plasticizers, used in the formulation of the vinyl resin. Monomeric plasticizers are usually cheaper and offer standard performance while polymeric plasticizers perform much better under environmental and chemical exposure.”

 

According to Schied, calendered vinyl experiences fewer problems in the solvent digital printing process. “One reason is the difference in surface structure between cast and calendered. Another reason is the thickness of the calendered and the resulting lower amount of solvents from printing inks that migrate to the adhesive.”

 

Regarding color choice, there is a larger selection for cast vinyl. “This is because different pigments can be added throughout the mixing process fairly easily,” notes Waters.

 

Closing the Gap

In the past, cast vinyl was only considered for use in high-end or long-term applications in the graphic market, but as Stadelman notes, the improvements in media quality and stability continue to advance with the introduction of new and creative manufacturing processes, improved chemical ingredients, and polymer advancements.

 

“This leads to a significantly better vinyl with long-term outdoor durability, improved flexibility, and dimensional stability rivaling most cast products on the market today,” he says.

 

Campbell agrees, citing that the gap between calendered and cast is shrinking especially in the intermediate application range. “This would include outdoor signage, vehicle graphics, and wall murals where the typical life range is between five and seven years and where a premium product is not needed.”

 

“With the level of quality and advancements in continuous processing, the juxtaposition between the two products has narrowed,” adds Roche. “Calendered vinyl has raised the bar and typically competes well in most cast applications today, especially since it is more cost effective. The calendering process is more precise; people now typically find calendered material in the 1- to 3-mil thickness range—something only attainable from the casting process not long ago.”

 

“20 years ago, calendered was classified as either monomeric or polymeric,” shares Hingst. “Today, a broader selection of resin grades and plasticizers expand that range. The new list includes monomeric calendered—3-mil thick, blends—3- to 3.2-mil thick, standard polymeric calendered—3- to 3.2-mil thick, and high-performance polymeric calendered—2.4-mil thick.”

 

Schied highlights the differences between monomeric and polymeric. “Calendered vinyl using low molecular weight plasticizers are ideal for low-cost indoor or short-term outdoor applications. Polymeric and high-grade vinyl is comprised of more complex, higher molecular weight plasticizers, which leads to a better durability.”

 

Polymeric quality combined with production improvements boost the performance of calendered vinyl. However, Rundle cautions that calendered vinyl with monomeric plasticizers can experience print problems if the plasticizer migrates to the surface of the vinyl.

 

“Polymeric calendered vinyl has come a long way in recent years in regards to flexibility and longevity,” agrees Medved. “New products are more stable, which means users can rely on them for many applications where cast vinyl was previously required. Furthermore, many manufacturers are switching to water-based coaters, which are more ecological and work well with calendered vinyl.”

 

When comparing polymeric calendered vinyl with cast vinyl there are not many differences left today. “The decision is often a matter of personal preference. However, a high-performance calendered vinyl can satisfy sign makers’ needs for a wide range of applications,” says Schied.

 

Due to improving processing capabilities and improvements with vinyl formulations, there are very little differences between a high-quality cast and calendered vinyl, as proven by many of the vendors mentioned in this piece.

 

Bigger Options

While calendered and cast still maintain their appropriate places in the market, calendered in particular is making great strides, allowing print service providers to challenge traditional notions about what can be accomplished.

 

The differences between cast and calendered are decreasing due to the types of plasticizers and development processes of the vinyl, as well as the advancements in printing technology. The end result is the ability to print thinner, more conformable, sharp images for both cast and calendered vinyl applications. Providing end users with more choices at all different price levels.

 

Sep2013, Digital Output

 
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