The Quest for the Bulletproof Pouch

The latest material combinations improve both the barrier and the strength of bags and pouches.

By Christina Elston

 

Photograph of Ultimate Gamma Packaging Courtesy Alcan Packaging Medical Flexibles Americas.

Tough applications such as packaging large surgical kits and vacuum forming to encapsulate sharp orthopedic implants demand tough materials. And while flexible packaging isn’t likely to find itself in the line of fire, many medical device manufacturers would like to find “bulletproof” materials—especially for pouches.

Defining Bulletproof

The first challenge, of course, comes in defining bulletproof. And this can depend on the application. “From what type of bullet do you need protection?” asks Leslie Love, vice president of sales and marketing at Tolas Healthcare Packaging (Feasterville, PA). “I think the reason people talk about ‘bulletproof’ is because the ramifications of failure are so great. It’s really important that we communicate well to come up with the most cost-effective package possible.”

Even defining bulletproof in terms of abrasion and puncture resistance is difficult. “Because there is no ASTM standard abrasion-resistance test,” says Jeff Murak, director of sales and marketing at Oliver Products (Grand Rapids, MI), “the industry is left to evaluate film using puncture-resistance testing that doesn’t do a good enough job of recreating real-world scenarios.”

Puncture resistance presents its own complexities. “There are several different kinds of puncture—including blunt, sharp, and cutting. The solutions for dealing with the various types of puncture are different,” explains Dhuanne Dodrill, president and COO of Rollprint Packaging (Addison, IL).

Nylon

One of the toughest materials currently used in pouches is nylon. It has been shown to be about four times stronger, gauge for gauge, than polyester, according to John Ozcomert, technical director at Beacon Converters (Saddle Brook, NJ). “For people who want a very tough barrier pouch, we give them nylon,” Ozcomert says.

While EVA/Surlyn had been the industry standard for toughness, nylons have replaced it because of their superior strength, says Murak. “End-users can thus drop thickness for thinner, better-performing nylon and get a better yield per pound, saving them money,” he says.

Multilayer films created by blending nylon with polyethylene and its derivatives are much stronger than monolayer polyethylene films, says Edward Haedt, marketing director at Perfecseal (Oshkosh, WI). “In many cases, a multilayer nylon/polyethylene film can be stronger at 60% of the thickness than a comparable monolayer polyethylene film, while the cost per unit area of film is lower for the nylon/polyethylene film,” Haedt says.

Sometimes the film orientation can add an extra degree of toughness, such as in a Perfecseal product called Ice film, says Haedt. The material features multiple layers of nylon separated by softer energy-absorbing layers. “An exterior layer of nylon offers excellent abrasion resistance, while the internal layers add strength and puncture resistance,” he explains. The arrangement of layers creates an I-beam effect similar to the strengthening effect of multiple wood layers in plywood, explains Haedt.

Perfecseal also markets a high-density polyethylene film with a nylon core and easy-peel sealant, and just began using it in pouch applications last year, says converted-products marketing manager Mary Czarnopys. The material often allows customers to downgauge. “Any films that contain nylon will immediately enhance puncture resistance, and in some cases, abrasion resistance,” Czarnopys says. “Customers who previously had to purchase 4-mil material from other companies can now purchase 3-mil HP-EZ Peel from us.”

Alcan Packaging Medical Flexibles Americas (Chicago, IL) also manufactures numerous nylon coextrusions, forming films, and nylon laminate materials that meet a variety of abuse-resistant applications, says senior research associate Brent Thompson. These, he says, offer resistance to puncture, impact, and tearing, and maintain a clarity that allows product visibility.

Polymer Blends

While nylon continues to advance, polymer blends and resins have also come a long way, says Dodrill. “Some of the polymer blends provide a lot more strength than some of the common nylon constructions being used today,” she says. “There are a lot of new technologies out there that give us more options than we had just a few years ago. By blending the right resins together, you can achieve some outstanding properties.”

These materials can be designed to offer good abrasion resistance and to stand up better to e-beam or gamma radiation sterilization than nylon does, adds Dodrill. Rollprint’s FlexForm and ClearForm lines, for instance, can be used to make bags and pouches, as well as in form-fill-seal applications, and they often cost less than nylon. “You can get the same performance out of the polymer materials as you can from multiple layers of nylon,” Dodrill says. “And we often can offer a nice cost advantage over nylon.”

Packaging Large Kits

For large surgical kits, abrasion is a special problem. “The biggest issue for hospitals is that they put these up on metal racks, and then nurses come by and grab them and the material abrades on the rack,” says Mike Oberkirch, marketing and operations director for pouches and bags at Amcor Flexibles (Mundelein, IL). Header bags made of a tough material—especially one with an outer layer of nylon—stand up to this well, he says.

As a nylon alternative for the same applications, Alcan offers Ultimate Header Film (UHF), a multilayer coextruded film that costs less than nylon. The material, available for approximately a year, has been saving customers money by eliminating nylon from the structure. “We’ve provided something that’s not a nylon film and provides four attributes for medical customers—exceptional puncture and impact resistance, a high degree of clarity, and ultimate tear resistance. Essentially, UHF provides many of the attributes of nylon, but at a lower cost,” says Thompson. “We have completed many substitutions with this film, and it has performed very well for our customers.” Metal trays and devices won’t puncture the clear film, which is compatible with EtO, gamma, and e-beam sterilization.

Some customers, however, find header bags difficult to open, according to Oberkirch. “To me, header bags are tougher to get into,” he explains. One alternative is to use a bag created from a film with linear tear properties, such as Amcor’s Unitear bag. This offers improved access, but at a cost. “What you give up, when you do that, is some level of toughness,” says Oberkirch. The bags are generally strong enough to do the job but certainly not as strong as nylon header bags.

“Typically, if we get a complaint, it will often be because of abrasion,” Oberkirch says. Device manufacturers, he explains, have to choose where they prefer to compromise. “A significant portion of the market,” he says, “is moving to form-fill-seal for kits.”

Vacuum Packing

Other challenging items to package are orthopedic implants—especially those that are vacuum packed. Perfecseal began making pouches from its Ice film in 2001 for just such an application, says Czarnopys, who adds that they’ve developed a significant customer base for the product. They’re now working to develop a version with a longer shelf life, she says.

Unfortunately, says Oberkirch, it is difficult to find materials pliable enough to vacuum around the product, yet with the barrier properties to hold a vacuum during several years of shelf life. Many of the materials with these properties are subject to stress cracking, he says.

Films originally intended for form-fill-seal applications, however, can often be made into a bag or pouch pliable enough for the application. To add barrier properties, Ozcomert says that metallocene films, which stand up to vacuum forming without cracking, have now been developed to the point where their performance is close to that of foil.

The Ultimate Header Bag from Alcan Packaging Medical Flexibles Americas uses Ultimate Header Film, a multilayer coextruded film employed as an alternative to nylon.

Tolas supplies packaging for many orthopedic customers, says Love. For applications that do not require a moisture barrier, they might offer combinations of nylon plus linear low-density polyethylene, upgauging as needed to improve puncture resistance.

For applications that require a moisture barrier, “our primary foil-based laminate is a 48-gauge polyester with up to a mil of foil and a low-density polyethylene,” says Love. To improve abrasion resistance, the outer polyester layer can be replaced with nylon. And if the customer wants to vacuum-pack the product, a softer, more flexible foil can be used. “There are more-formable foils that can be incorporated into these laminations,” she says.

Tyvek Adds Toughness

In an effort to offer a new material that would fulfill customer needs for an absolute moisture and gas barrier, peelable seals, and superior puncture and abrasion resistance, Beacon Converters recently began using DuPont’s Tyvek 2FS in a new way. Applying both a foil lamination and a peelable film to Tyvek 2FS, the company has created a material they call A34T, reports Ozcomert. Though the company has not yet formally begun marketing the product, they are working with DuPont to do shipping simulations that will “quantify some of the advantages of the material,” Ozcomert says.

Testing will likely be completed in the next three to six months. “Meanwhile, we’re collecting information from actual users,” Ozcomert says. One customer used the material for a pouch that could stand up to cryogenic storage and provide a moisture barrier. “He needed something that would resist the cracking that takes place at liquid-nitrogen temperatures,” Ozcomert says. Another used it provide puncture resistance in long, narrow pouches used for catheters.

“Foil has a tendency to pinhole and flex-crack,” explains DuPont packaging consultant Karen Polkinghorne. She adds that the pairing with Tyvek would add strength, making the final material suitable for “any foil application that requires abrasion or puncture resistance,” including packaging for drug-coated devices. “Some of the drug coatings are fairly sensitive to moisture or oxygen, and they need a high-barrier material,” Polkinghorne says.

As new technologies such as drug coatings change devices, the ever-shifting definition of bulletproof will continue to change as well. “Can we make a bulletproof pouch for a specific application?” asks Dodrill. “Absolutely.” But, she and others add, there is no single pouch that’s bulletproof for everything. Packaging professionals instead must continue to match packaging to the specific needs of products, tackling each new application one challenge—or one bullet—at a time.

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