By Melissa Donovan
Raw film manufacturers play an important role in the creation of the vinyl materials used daily in the graphic arts. Typically, the manufacturer produces the vinyl and their customer—a converter—applies the adhesive, liner, or coating to create the final product. This is then sent to a print shop and eventually used in a vehicle wrap application, wallcovering, or something else.
Cast vinyl is the traditional popular choice for applications involving wrapping and stretching, but calendered vinyl has undergone manufacturing improvements that allow it to compete with cast vinyl. The additives that make up these materials on a molecular level are also changing, as more raw film consists of phthalate-free plasticizers.
Manufacturing advancements over the last few years have led to vinyl—both cast and calendered—being held to higher specification standards. Machinery and the technology that drives it are able to hone in on microscopic features and control them batch to batch to institute a high level of uniformity.
Above: Calendering line at OMNOVA.
At a basic level, there are two types of vinyl—cast and calendered. Both are used in wide format graphic arts applications. The difference between the two is best explained by looking at how they are produced.
Renaat Demeulemeester, president, American RENOLIT Corporation (ARC), takes us through the production of both calendered and cast vinyl. “Calendered vinyl is produced in a continuous process that enables high-volume, low-cost manufacturing. On the calendered line the raw materials are mixed together, extruded, and then flattened out into a thin film by passing through various heated calendered rolls. In cast manufacturing, a liquid is poured onto a carrier sheet, which is then heated in ovens. No stress is involved in the process, so the sheets feature no shrinkage.”
Some of the advantages of calendered film, according to Tammy Polovic, global marketing manager, OMNOVA Solutions, is that it can be manufactured in a wide range of thicknesses, with better thickness control.
Cast materials offer no shrinkage and are more conformable, which is why they’ve always been popular for use in vehicle wrapping. “However, calendered vinyl is typically much less expensive compared to cast. Recent improvements in manufacturing techniques allow calendered vinyl to compete with cast vinyl in certain applications,” explains Chad Turner, VP, Achilles USA, Inc.
A derivative of cast is high-performance thermoplastic polyurethane (TPU). “Cast polyurethane films use a resin that is melted and extruded through a flat die. This manufacturing method ensures the best gloss levels with consistent thickness and offers the ultimate control for all critical properties of the film. Unlike vinyl, polyurethane film extrusion does not require solvents in its manufacture, making it a ‘greener’ alternative,” shares Kevin Beckerdite, product manager – graphic films, SWM International.
TPU is commonly used in outdoor applications where resistance to UV radiation, chemicals, and physical abuse are required. It can be utilized as a primary substrate on which to print and because of superior optical quality, can be used as an overlaminate.
Vinyl consists of monomer or polymer plasticizers. A plasticizer’s purpose is to make the substrate flexible and improve durability. Monomer vinyls use low weight plasticizers, whereas polymer vinyls consist of higher weight plasticizers.
“Polymeric plasticizers are more robust in the structure and provide greater permeability, and are non-phthalate. They also generally result in higher surface energy. Monomeric plasticizers on the other hand have a lower molecular weight. Depending on type, they can offer a wider range of performance characteristics such as flame retardation, low temperature flexibility, and weatherability—and are not limited to phthalate chemistries,” shares Polovic.
One of the main reasons why calendered vinyl is on par with cast vinyl today more than ever is because of polymer plasticizer usage. “Polymeric films are comprised of more complex, higher molecular weight plasticizers, which leads to a higher viscosity and better stability. This polymeric quality combined with production improvements boost the performance of calendered vinyl. Even though calendered film is not made the same way as cast, it now features nearly the same performance,” says Demeulemeester.
There is also the question of sustainability. Traditional plasticizers are not the greenest additive, so many raw film manufacturers experiment with other options. For example, Achilles expanded its use of non-phthalate plasticizers in its vinyl manufacturing process.
ARC has done the same. In August 2017 it began offering sign and graphics customers phthalate-free films. “The move demonstrates a strong commitment to proactively maintaining a leading position in terms of response to market and customer needs as well as compliance with regulations,” explains Demeulemeester.
Over the last 20 years, Polovic points out that regulatory and environmental stipulations and laws such as PROP 65, REACH, and RoHS, have influenced the manufacturing process and ingredients used in a film recipe. “There is a move to non-heavy metal color pigments and new plasticizer chemistries providing alternatives to traditional phthalate plasticizers.”
Polyurethane graphic films do not need or contain plasticizers to keep them flexible, according to Beckerdite. “TPU maintains excellent elasticity throughout the working life of the film without the need for environmentally risky plasticizers, halogens, or phthalates,” he continues.
Dialing in on Control
Equipment advancements allow for a more reliable manufacturing process. Quality and material properties are more controlled than ever.
Turner cites modern electronics and computer controls as two factors. “They have allowed the process to become much more precise, greatly improving the overall quality of calendered films. Manufacturers can hold a much tighter tolerance than what was possible two decades ago,” he shares.
Demeulemeester agrees, explaining that intelligent control systems monitor and measure parameters related to both the machine setup and the material itself—both crucial to overall quality. “For example, film properties like thickness, color, width, and gloss level are constantly controlled. As a result, the whole manufacturing process has gained much greater uniformity. The films can be specified even tighter and overall quality is more consistent,” he continues.
“The improvements made in the quality control and monitoring equipment in the manufacturing process allows for better gauge consistency, roll profile, and higher gloss levels and greater depth of color achieved if desired,” adds Polovic.
The manufacture of TPU in the graphic arts is relatively new, according to Beckerdite. Available only over the last few years, the production of this cast vinyl product is in its infancy compared to more traditional methods.
Here, raw film manufacturers define their companies’ position in the overall manufacturing process of vinyl/films used in graphic arts applications.
The Achilles Corporation is home to nine manufacturing facilities in China, Japan, Southeast Asia, and the U.S. The main company is 75 years old and the U.S. branch celebrates 45 years in business. Achilles USA—with main headquarters in Everett, WA—is a supplier of vinyl films to a variety of different industries, including graphics, medical products, industrial fabrics, and specialty fabrics. For the graphic arts, it manufactures static cling vinyl, pressure-sensitive films, and overlaminate films.
Achilles also produces polyolefin graphic films such as polypropylene and polyethylene using a cast extrusion process. The company’s cast line is designed for high output and according to Turner outperforms many calendered lines. It extrudes multiple layers at a time, which creates a film that is white on one side and black on the other—all in one process.
OMNOVA, in business as an independent, publicly traded company since 1999, is a calendered vinyl manufacturer of film made in various thicknesses, colors, print patterns, and textures that can be printed through traditional or digital printing methods. Both flexible and rigid, monomer or polymer plasticizer calendered films are created in thicknesses from three- to 40-mil. Features include printability, antimicrobial, fire retardant, UV resistance, low shrinkage, skin contact, and non-skid surfaces. The film is manufactured in three different plants—Auburn, PA; Jeanette, PA; and Thailand.
RENOLIT manages over 30 locations and 4,500 employees on four continents. It is an independent family-owned business celebrating 70 years in the manufacture of high-quality plastic films and related products for technical applications. In the U.S., ARC is based in La Porte, IN. ARC’s calendered film is used as the face stock for numerous pressure-sensitive applications. These products are used for indoor and outdoor advertising and branding, vehicle graphics and architectural graphics, as well as product identification.
SWM’s headquarters is based out of Greenfield, MA and comprised of four separate facilities. Originally known as Argotec, the company was established in 1988 and acquired by SWM in 2015. It mainly offers blown and flat die cast extruded TPU films for use in graphics, automotive, industrial, defense, and medical applications.
According the company, TPU film augments vinyl portfolios to help maintain customers’ brand messages in the most demanding outdoor applications. SWM’s polyurethane film system is manufactured in MA in an 8,000 square foot, hard-walled white room. Each individual extrusion line is housed in its own ISO Class 7 soft-walled clean room.
On the Manufacturing Floor
While the behind the scenes study of raw film manufacturing may not be glamorous, it is a pivotal part in the creation of the material that ultimately goes on to become a wall, floor, or window graphic. The raw film manufacturers mentioned in here—in addition to others—are experts on the most intricate details of a piece of vinyl. It is their knowledge of the science behind the material that creates some of the more durable and high-quality mediums print service providers work with daily.
Feb2018, Digital Output