The Big Picture in Packaging

In the medical industry, packages have a number of big jobs. Most important, they must keep enclosed devices clean, sterile, and undamaged. In addition, they can give products a more pleasing appearance that will appeal to potential customers.

Of course, how well packages do their jobs depends on the materials, techniques, and designs used to make them. Some developments in these areas have been aimed at improving package strength, flexibility, sealing, and sterilization. Others seek to increase aesthetic appeal and lower costs. And one development is thrusting packages into the new role of making the products they hold easier to use.

Barrier Options

Today, a number of packaging materials serve as barriers that protect medical devices from moisture and oxygen. For many years, moisture and oxygen barriers have been provided by a layer of aluminum foil. One barrier product that relies on foil is Cold Form 3000 from Alcoa Flexible Packaging (Pittsburgh). The proprietary Cold Form 3000 structure includes a heavy-gauge foil layer, as well as PVC and polyamide. In tests, the material has been drawn to a depth 15% greater than the standard commercial draw depth, according to Alcoa. When drawn to this increased depth, the material exhibited no signs of stress and maintained package integrity, the company says. That matters because it means a material developed for pharmaceutical blister packaging can also be used for some medical devices. Cold Form 3000 can be used for contact lenses, syringes, and other medical devices that can fit in a package approximately half an inch deep or less, says Keith Yanuzzi, the company's director of new business development.

Another protective product from Alcoa is Safety-Pak Plus, which includes a 25-µm layer of aluminum foil and a 50-µm PET layer. The product also features a patented cohesive peel material that ensures seal integrity is independent of actual peel force.

Like Cold Form 3000, this product is currently used in pharmaceutical packaging, but Yanuzzi sees potential uses in surgical device packaging as well. “You have very good seal integrity, so moisture won't get into the package prematurely,” he says. “But at the same time, someone wearing gloves or with wet hands could open it in the middle of a procedure very easily and consistently, without fumbling with the package.”

The barrier products made by Tolas Healthcare Packaging (Feasterville, PA) now include more-flexible foil grades. A result of both the alloys used by Tolas and the processing of them, more-flexible foils are less susceptible to flex cracking in packaging applications, says Leslie Love, the company's director of sales and marketing.

A more expensive barrier option than foil is Aclar, a clear material that is added to trays in thin layers. The depth of the tray being formed is critical when using this specialty material. Aclar normally works well when used to make trays up to an inch deep, while cyclic olefin copolymers (COCs) are usually the materials of choice for deeper trays, according to Jennifer Lauderback, senior medical account manager for Placon Corp. (Madison, WI), which provides custom packaging to the medical industry. Unlike Aclar, which is laminated to other material layers, COCs are coextruded. That means there is no delamination when thermoforming draws are more than an inch, Lauderback explains.

Another clear barrier material is aluminum oxide–coated PET, which provides moisture and oxygen resistance equal to that of foil, according to Barbara Fritz, senior packaging engineer for Donatelle (New Brighton, MN), a contract manufacturing firm that provides packaging services.
The material's clarity allows the enclosed product to be seen, enhancing the appearance of the package. In addition, Fritz says, aluminum oxide–coated films provide much
better resistance to flex cracking than foil. On the downside, she notes, the materials are very expensive, and their clarity makes them unsuitable for packaging UV-sensitive products.

Some Tolas packages have aluminum oxide–coated polyester on one side and foil on the other. These packages provide product visibility but are less costly than packages with aluminum oxide coating on both sides, Love says.

Barriers Ahead

Looking ahead, Tolas is working on some new film products that the company hopes will offer greater flexibility than the clear barrier materials currently on the market, which will help them maintain their barrier properties when stressed. If the development efforts are successful, the new materials will also be less expensive than products like Aclar. “We have some trials going on now with some entirely new formulations that look really interesting,” Love says.

Another barrier product in development is a new version of Tolas's Dispos-A-Vent pouch. Made of high-barrier films and foils, these pouches include a disposable vent made from paper or DuPont Medical Packaging's (Wilmington, DE) Tyvek. One side of the package is a complete barrier, while the other consists of a partial barrier and the porous vent material, which allows sterilization gases to enter and exit the package. After the sterilization cycle is complete, the user makes a seal in the film or foil area of the pouch and cuts off the vent. The result is a sterile device in a film or foil pouch with barrier properties.

To allow sterilization, a manufacturer could package a device in a Tyvek or paper pouch, sterilize, and then enclose the porous package in foil or a barrier film. But Dispos-A-Vent eliminates the need for an extra package and packaging step, saving time and money.

For some time, Tolas has been offering Dispos-A-Vent packages for ethylene oxide sterilization. Now, though, the company is developing another Dispos-A-Vent product that will allow steam sterilization. To make this version of the product, Love says, the company is using material science for retort packaging to produce a pouch that can survive a high-heat sterilization process.

More on Materials

In addition to barriers, packaging materials provide a number of other critical properties. For example, PETG is normally used to make outer device trays due to its excellent impact strength, which prevents damage to the device inside when a package is dropped. This impact protection is particularly important for relatively heavy medical devices, since heavier packages must withstand more force when dropped than lighter ones.

For packaging lighter-weight devices, Placon offers PET as a cost-effective material alternative to PETG. PET is also well-suited for inner package lids and retainers, which don't have the same strength requirements as outer packaging components, notes Lauren Foos, Placon's medical sales manager.

In such applications, Foos says, PET can be 40–50% less expensive than PETG. Though not as strong as PETG, PET offers good impact strength. It also seals and sterilizes well, has excellent clarity, and can be colored to provide UV protection, she adds.

A familiar medical packaging material is Tyvek. Although it has attractive properties, Tyvek can complicate the packaging process, according to Fritz. How? One thing packaging personnel look for is dark areas of a heat seal. A dark area can be an indication that adhesive has been forced out by the high temperatures and pressures of the sealing process, possibly resulting in a loss of seal integrity. But dark areas are also a characteristic of conventional Tyvek, for which appearance at a certain spot depends on whether the material in that area is thick or thin, Fritz says. Thin areas of Tyvek appear dark, she explains, making it difficult for packaging personnel to tell whether darkness in a sealing area is due to the composition of the Tyvek or to poor seal quality.

Compared with conventional Tyvek, however, Tyvek Asuron has a more homogeneous appearance, which may make it easier to visually evaluate heat seals. Asuron also provides the same puncture and tear resistance as older versions of Tyvek, Fritz notes.

Maintaining Sterility

Of all the functions performed by materials used to package medical devices, the most important is maintaining the sterility of the enclosed product until it reaches the point of end use, which is often a surgical setting, says Ed Haedt, vice president of marketing for Perfecseal (Oshkosh, WI), a supplier of medical packaging. “Any holes in the package create the potential for contamination—and potentially a bad outcome for the patient,” Haedt says.

To help ensure that packages keep their contents sterile, some medical firms are now using packaging materials that include multiple thin layers of nylon. Nylon prevents package failures by providing better resistance to abrasion, punctures, and flex cracking than polyester, according to Haedt.

In recent years, Haedt adds, nylon has been coextruded with layers of polyethylene to create structures that are manufactured in one converting step. Coextruded films with multiple thin layers of nylon provide physical properties equal to or better than those of traditional laminated films such as polyester and polyethylene, he claims. In addition, he says, the new films are up to 50% thinner than older laminated films.

Haedt also maintains that multilayer nylon films can be both stronger and thinner than structures with a single nylon layer. “Let's say one film has a layer of nylon that's 0.1270 mm thick, and another film has the same nylon content, but it's distributed among three layers. We find that we can have a film structure about 0.1016 mm thick that has properties that are equivalent or superior to those of a 5-mil material.”

The bottom line: “By separating the nylon content into multiple layers, we usually see an improvement of 20% in physical properties, which lets us reduce the thickness of the structure about 20% compared with a structure with just one layer of nylon,” he says.

In form-fill-seal packages, multilayer nylon films can be used as forming webs or top webs. In addition, Haedt says, the films are now being used to make pouches. Unlike thermoforming, pouching applications expose packaging materials to a good deal of heat, which is applied to achieve sealing. Therefore, Haedt notes, multilayer nylon films used for pouches require a heat-resistant layer on the outside.

Multilayer nylon films can also be incorporated into laminates with foil to protect the foil from punctures and other types of damage. Alone or joined with other materials, coextruded nylon films can be used to package a variety of medical items, including needles, surgical kits, and drug-eluting stents.

Sealing Developments

Of course, there's more to a good package than the packaging material. A package must also be effectively sealed. For better heat-sealing, Donatelle uses an adhesive from Oliver Medical Packaging LLC (Grand Rapids, MI). Applied in a dot pattern, the adhesive, sold under the brand name Xhale, yields a more consistent heat seal than that provided by adhesives applied with a roller-type coating process, according to Fritz.

Though it costs more than some adhesives, she says, Oliver's coating allows users to see where the adhesive dots have melted together to form a complete seal, as well as to identify any channels or open areas in the heat seal. It is also a polymer adhesive technology, which makes it more moisture resistant (and therefore less likely to weaken when a bond is exposed to moisture) than water-based adhesives. In addition, Donatelle has found that heat-sealing with Oliver's coating requires less pressure than similar processes with other adhesives, which reduces the wear on packaging machinery. Low-pressure application is also supposed to produce seals that last over long periods of time.

Other trends in sealing seek to prevent any adhesive transfer from the package to the device inside. One such development is zone coating of adhesives used with lidding or pouch materials. This pattern coating process limits where adhesive is applied during packaging. For example, Fritz says, packaging personnel using zone coating can choose to apply adhesive only on a perimeter area that will interface with a flange that is being heat-sealed.

In addition to reducing the potential for adhesive transfer to the device in the package, zone coating can speed up the sterilization process. Packages with less adhesive on the lidding or pouch have better porosity and breathability, which facilitates the movement of chemicals into and out of the packages during ethylene oxide (EtO) sterilization. As a result, zone coating can reduce cycle time for EtO processes by as much as half, Fritz says. Besides zone-coating technology, Donatelle also has a heat-seal coating that fluoresces under UV light. According to Fritz, this property allows packaging personnel to see the consistency of the coating. When that coating, sold by Tolas under the name SealScience, is combined with zone coating, packagers can use UV light to see the consistency of a heat seal.

Featuring good moisture resistance, the fluorescent coating helps ensure that seals will remain intact when exposed to high-moisture conditions, Fritz adds. The coating also offers high porosity, which speeds up ethylene oxide sterilization. In addition, one version of the coating provides static-dissipative properties that help minimize foreign particles drawn into medical packages by static electricity.

A Functional Role

In addition to their other jobs, some packages are now playing functional roles in which they interact with the enclosed device and the end-user. For example, new Donatelle packages include precision components that position and release devices in ways that facilitate use with another instrument.

Packages that include functional features can help medical products—and the firms that make them—stand out in a crowded field, according to Fritz. “More and more companies are differentiating themselves by presenting devices in ways that make them easy to use and provide the best results.”

Copyright ©2008 Medical Device & Diagnostic Industry