Synthetic Substrates

By Jack Kenny | July 20, 2005

Durable films that feel like paper are widely used in labels and tags, as well as in emerging applications.

They look like paper, and many of them feel like paper. They perform as films do, because most of them are film products. Since their introduction more than 30 years ago, synthetic papers have earned a lasting place in the catalogue of versatile substrates employed in the printing and packaging fields. Because of their appearance, durability, and resistance to tearing and outdoor elements, they are the material of choice in a wide range of applications, and continue to grow in popularity.

The history of synthetic paper is convoluted, and involves companies on both sides of the globe. The earliest incarnation, called Ucar, resulted from joint efforts by Union Carbide and Mead Paper Company. Manufacturing rights then went to Oji Yuka Paper Co. in Japan, which added titanium oxide to the product and named it Yupo. Kimberly-Clark received distribution rights back in the Western Hemisphere, re-tweaked the product, and called it Kimdura.

When Union Carbide was working on its synthetic paper formulas in the 1970s, it sold its UK division to BP Chemicals, which teamed up with Arjo Marie, a French company. That alliance led to the formation of Arjobex, which produces Polyart, a family of synthetic papers for the packaging and label (and other) markets. Polyart was introduced to the United States in about 1983, about 10 years after the arrival of Kimdura.

Valéron, an ITW company, also is a major player in the field, as are the products manufactured by Nanya Plastics in Taiwan.

Most synthetic papers are biaxially oriented polypropylene (BOPP) films that are produced in a couple of different ways and coated with proprietary formulas. Then there is DuPont Tyvek, a household word today, in many senses a synthetic paper but different from the others. Tyvek is a large family of tough, durable products of high density polyethylene fibers, formed by spinning continuous strands of very fine interconnected fibers, then bonding them together with heat and pressure. It's white, chemically inert, and contains no binders. Though there are many variations, Tyvek comes in two basic types: 10 and 14. The fibers in 10 are dense and the surface is smooth, highly opaque and white; it is this type that is used by packaging people. Type 14's fibers are not as densely bonded, and the resulting substrate has higher mobility and a fabric-like drape.

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Brands and hybrids
"Synthetic paper is a fancy name for plastic film with a coating on it, typically," says Steve Nimz, president of Protect-All Print Media, Darien, WI, USA. Nimz should know. His company markets many brands of the material, including Valéron, Yupo, and others. "There are so many different types out there today because there has been quite an increase in the size of the market. We carry five or six different brand names, and all serve different purposes."

Protect-All takes synthetic papers a step further by creating its own versions from existing brands, marketing them under the Printmaster and Packmaster names. "We take some brands and laminate them together to make hybrids," says Nimz. "For example, Valéron is extra tear resistant, but it lacks some other properties, so we'll laminate an Appleton direct thermal synthetic to give it strength and direct thermal capabilities.

"We also take our coatings here and do niche applications, such as for dot matrix or impact printing, a technology that has declined in the US but still is big in Southeast Asia and Australia, for the steel industry. Or we will put a synthetic between two layers of conventional paper, making a sandwich. It's common for price tickets, where the customer needs a durable tag for high value items, but doesn't want it to look different from other items in the store."

Synthetic substrates differ in appearance somewhat, more so in performance. "They differ relative to the manufacturing technique," says David Hoag, national converting sales manager for Arjobex, Charlotte, NC, USA. "Polyart is a BOPP, like most others, but what differentiates it is the way we orient the film. We stretch it in the machine direction (MD) and the cross direction (CD) at the same time. Other synthetics are stretched sequentially, first in the MD, then are put through another operation that stretches in the CD." The process involves the appropriate lining up of the molecules in the film, he notes.

Polyart is a single ply film (some others are laminates) with a clay coating. Before coatings were introduced, Hoag says, printers struggled with ink adherence, and would experience drying and offsetting problems. The coatings used today in synthetics contain calcium carbonate, which make the substrate much more printer friendly, but which offer challenges to cutting dies because they are abrasive.

Hop Industries, of Garfield, NJ, USA, is a distributor of Nanya synthetics. Vice President Jack Smith explains that some of the many varieties are extruded, while others are calendered. "With extruded films you have tensile strength, because they are biaxially oriented. Some are just corona treated, and others have a thin clay coating on top to make it more printer friendly. You can't use these for food applications because the clay could come off during the diecutting.

"The calendered films have flexibility and therefore better folding characteristics, because they have clay fillers (the clay is mixed into the substrate), and can withstand certain temperatures," Smith adds. "Clay filled materials also have properties that allow inks to absorb into the surface, making thermal transfer printing easier. These can be used for direct food contact."

Hop Industries' calendered product, Hop-Syn, is used primarily for tag applications. The extruded film is called Dura-Lite, is sold in thinner gauges, has a higher dyne level, and is used more for pressure sensitive labels and flexo printing.

Valéron Strength Films, based in Houston, TX, USA, produces two synthetic brands: Valéron and V-Max. The former is cross laminated and is known for its exceptionally high tear and wire-pull strength, says Rich Witmer, marketing communications manager. V-Max is not cross laminated, and is still strong but not as much as Valéron, he says. "The choice comes down to usage," says Witmer. "In most cases it's a characteristic that the end user needs." The base resin of the two is polyethylene, he adds.

Valéron products tend to be a little more expensive, but carry the cache of extreme strength. "What's the value of losing a tag?" Witmer asks. "On a piece of furniture it's one thing, but on a load of steel it gets pretty expensive. Our product has found its niche — it stays attached."

Granwell Products, based in West Caldwell, NJ, also distributes Nanya synthetics under the Polylith brand name. "Polylith has two major grade families: the G series, a mono-layered, calendered material; and the P series, a multi-ply extruded BOPP available in either clay coated or non clay coated versions," says John Giblin, director of marketing. "Our philosophy is to be 'application specific', meaning we have the right material for the application rather than a 'one size fits all' approach."

Yupo America, of Chesapeake, VA, USA, manufactures a wide range of synthetics known for their smooth surfaces. As with other manufacturers, Yupo's products are used in PS, direct thermal, cut and stack and many other applications, including in-mold label (IML). The company introduced two new IML substrates in November.

"The IML products feature improved anti-static properties and an especially smooth surface," says Paul Mitcham, national marketing manager. "We developed these grades in response to a growing demand for sophisticated packaging. The superior anti-static properties will result in increased 'pick and place' efficiencies and higher press speeds. And the smooth surface will improve bottle and label texture matching", which is the ultimate aim in IML packaging.

In general, synthetic papers perform on press the same way films do, though they can benefit from "more sophisticated printing and converting techniques," says Giblin of Granwell Products. The products can handle press temperatures, but they don't work in laser printers because of the high degree of heat produced in those machines.

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New markets
Uses for synthetic substrates are legion. They are big in airline baggage tags, in tags for steel and reinforcing bars, in the lumber industry, in food, in the garment industry, for ski lift tickets, wrist bands. New synthetics are being launched for the security products market, including destructible products for tamper evidence.

"Our hybrid products," says Nimz of Protect-All Print Media, "are used in a million different applications, including rocket launcher manuals for the United States military."

RFID is the hot topic of the day in this and many other industries, and the synthetic paper people see their products playing a major role.

"In RFID there are durability issues," says Nimz. "You need to keep that chip dry, prevent moisture absorption. And there are significant static issues."

"We're keeping our eyes on RFID," says Witmer of Valéron. "There's a niche in protecting that inlay, that chip. When RFID prices get really low it won't matter what substrate you use, but right now if you want to protect that chip you need a durable substrate on the outside."

There's a significant DOA factor in RFID," says Hoag of Arjobex, referring to radio frequency chips that are dead on arrival at the end of the converting process. "We're seeing 20 to 30 percent loss today, and that's huge. There are three reasons: One is mechanical damage to the chip itself; two is electrostatic discharge, which will fry the chip; and three is that the chip didn't work from the get-go".

"Every month a dozen new end uses come along. By and large, there's more and more information being put onto a tag or label, whether bar codes or RFID or anything else. It becomes important that the identification stay with the label. Synthetics will outlast conventional paper, and generally will give a higher quality image. All in all, tags and labels these days are a lot more than just a couple of numbers on a piece of paper."

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Not synthetic at all: Organic film takes off
And now for something completely different — different from synthetics. One of the more recent introductions in the catalog of films has nothing at all to do with petroleum based materials. This one is organic, and is made entirely from corn.

NatureWorks PLA is a plastic derived from corn — PLA is polylactic acid — that was developed over the past several years by Cargill Dow, of Minnetonka, MN. Not a drop of fossil fuel is used to make the material, and therefore it is fully compostable.

The product has been attracting attention in a world of extremely high oil prices and concern over future petroleum supplies. Unlike oil, corn is renewable. The Wall Street Journal reported in October that sales of NatureWorks PLA by Cargill Dow rose 60 percent in the first nine months of 2004 from the same period a year earlier.

A few companies who supply the narrow web industry now use Natureworks PLA films manufactured from NatureWorks, among them Green Bay Packaging and Plastic Suppliers.

"We're the only company that uses the NatureWorks resin to produce blown film plastic," says Scott Cordial, marketing manager for Plastic Suppliers, based in Columbus, OH. "The others are cast and tentered. And we're one of the few that are actually manufacturing. Most others are distributors."

Plastic Suppliers calls its film EarthFirst PLA, and it is available in clear and matte versions. The company is targeting the envelope window, label and folding carton markets, Cordial says.

Mike Bower, director of research and development at Plastic Suppliers, says EarthFirst has a natural dyne level between 38 and 40. "It's very breathable, adhesive-friendly, and gives a good no-label look."

As for performance on press, the PLA film has an upper temperature limit of between 140° and 150° F, Bower says, "and we are working currently on improving that." The company is looking ahead to developing PLA films for shrink and other applications.

The film has "excellent scratch resistance," notes Bower, "and excellent odor and taste barrier properties." PLA film one mil in thickness breaks down completely in about three weeks in a municipal landfill, he adds.