The Age of Plastic: Synthetic Substrates Have Evolved with New Printing Technologies

“Synthetic paper”—a substrate made from polymers rather than wood pulp—has been available for decades, but is now being utilized for new applications as printing systems evolve that are more capable of printing on them. In turn, synthetics are being formulated to be more compatible with today’s digital printing systems.

First, a quick note on terminology. Can these substrates legitimately be called “paper”? Some would argue that unless they are made from wood pulp, using the term “paper” is a misnomer. Some instead call them “durables,” “synthetics,” or even just “plastics.”  (Take a look at Sappi's "The Environmental Quotient" blog post here.)

No More Tears

The term durables is used to describe these materials because their killer app is that they are hard to rip or tear, which makes them well-suited to applications that require a high resistance to manhandling. Labels, envelopes, ID cards, maps, and other such items are top uses for synthetics. Synthetics are also being used in the wide- and grand-format space, especially as UV printers remove the traditional challenges of printing on plastics, such as proper ink adhesion.

Synthetics are also proving to be more appealing than laminated natural paper in certain applications.

“One we tend to focus on is printed menus,” said Garth Geist, director of sourcing, paper, for xpedx, which has been carrying synthetic grades for the past couple of years. “I think all of us have been in restaurants where you get a laminated menu and food and drinks have been spilled on it. The edges start to delaminate and come apart. It’s not very appealing. A lot of printers and customers are having great success with something as simple as menus.”

Poly Exclusion Principles

There is a tendency to lump synthetics into one category, but different grades use different types of plastics, ranging from polyvinyl chloride (PVC), to polystyrene, polyethylene, polypropylene, and, at the high end, polyester. That’s a lot of polys. But these different plastics have different surface and performance characteristics. “Polypropylene has the look and feel of a satin-coated paper,” said Geist. “But other synthetics like polyesters will have a ‘snap’ or ‘rattle’ to the sheet because it’s more of a rigid material.”

Synthetics aren’t designed to be a one-to-one replacement for natural paper. For one thing, they have different tactile properties, and thus are better suited for certain applications like the aforementioned menus, labels, and other products. For another, synthetics can also be more expensive than paper—often up to four times as much. “If you would traditionally print on [natural] paper you could be paying 4X for the substrate compared to paper,” said Geist. But, he added, “All synthetics are not created equal.” PVC is the lowest cost option, and synthetics based on different polymers are increasingly expensive, with polyester being at the top of the price pyramid.

Paper Meets Presses

As with paper, durable substrates need to be selected based on the output device and printing/ink technology to be utilized. Synthetics don’t go straight from the extrusion process directly to the end user; they are often coated or otherwise pretreated so that the sheet will print and cure properly. So a synthetic designed for a toner-based system like an iGen, HP Indigo, or Nexpress will differ from one designed for an aqueous inkjet wide-format printer, which will differ from one for a solvent inkjet printer, and so on. Xpedx recently added two new digital synthetics to its portfolio—PoliPrint is a polyester-based paper that is compatible with a wide range of toner-based digital presses, while YUPO’s YUPOBlue is polypropylene-based and has been certified by the Rochester Institute of Technology (RIT) to run on the HP Indigo.

Thus far, synthetic grades for high-speed, high-volume production inkjet have yet to emerge—but that’s not surprising when you consider that vendors are still struggling to get paper grades to work flawlessly with inkjet equipment. Still, synthetic grades are available for wide-format inkjet equipment. And UV wide-format is especially compatible with plastic substrates.

Other vendors and suppliers also make a variety of synthetic grades. Agfa Synaps, for example, is a polyester-based substrate that aims to recreate the proverbial “look and feel” of natural paper while also retaining the durability and longevity of a synthetic.

Best of Both Worlds

Some users require the strength and durability of a plastic-based substrate while at the same time require the printability and tactile qualities of natural paper. As a result, there are so-called hybrid blends. One is a product from Neenah Paper called Paper Tyger, which is a three-layer sandwich comprising a plastic film between two layers of natural paper. As a result, it feels and performs on press like an uncoated paper, but has the tear-resistance and other durability characteristics of a synthetic.

End-of-Life

At end of life, synthetics—being plastics—can be recycled (YUPO’s synthetic grades, for example, are Category 5 recyclable products), but users should be careful not to add the plastic substrates into the paper recycling stream. “‘Synthetic papers’ should go in the plastics waste stream,” advised Martine Padilla, executive director of the Sustainable Green Printing (SGP) Partnership. “If they end up in a paper stream, the plastic could contaminate the [paper pulp] or at minimum get skimmed off the top during pulping and end up in a landfill.”

Blurring the Lines

Particularly in the wide-format space, the number and variety of substrates both natural and synthetic are proliferating wildly, such that synthetics are not thought of in the same way as they are in the small-format space. Vehicle wraps, floor graphics, specialty items—all these applications and more are printed on what would be considered “synthetic” substrates.

As with natural paper, choosing the right grade is a function of the desired end-use product, and the printing and ink technology that will be used—and synthetic grades exist for all of the above.

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