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Flexible Packaging Toughens Up for Heavy Devices

New flexible materials, special sealing configurations, and inserts aim to support heavy devices or multiple-component kits just as securely as rigid packages.

Your company's design department has just revealed plans for a new surgical procedural kit, and you've been assigned to design the package. It will contain up to six different devices, some of which will measure more than a foot, and the entire set could weigh up to 10 lb. Your firm has traditionally used PETG trays, either sealed with lids of Tyvek or placed into header bags. Should you follow suit and design a similar package for this new kit?

Not necessarily. Advances in flexible packaging, such as inserts, stronger films, and unique sealing configurations, are allowing manufacturers whose devices have traditionally needed the strength of rigid trays to rely on header bags or even pouches alone. Medical packaging converters are even custom designing packages to support heavy, bulky, or odd-shaped products. So, before calling up your thermoformer and submitting designs for prototype tray tooling, you may want to check with your flexible-packaging suppliers. According to a number of them, you may be able to use a flexible package for the procedural kit, keeping package design time and material costs to a minimum.

MATERIALS

As medical device converters have experimented with new resins, they have found ways to strengthen traditional flexible packages like header bags and pouches. Rexam Medical Packaging (Mundelein, IL) offers bags and pouches based on a variety of multilayer film structures using ionomers, metallocene, and nylons. For instance, Rexam's Integra Pack Tuf 1000 is an abuse-resistant header bag based on single-site metallocene resin technology. The technology provides a uniform polymer chain, increasing material strength and puncture resistance. "Metallocene offers improved resistance to punctures and pinholes, problems that have plagued bag users for years," explains Darryl Goodwin, Rexam's product manager for converted products. During puncture testing (Instron), a 5-mil header-bag structure made of Tuf 1000 film demonstrated more than 12 lb of puncture resistance, while a 3-mil withstood nearly 9 lb. The same 5- and 3-mil structures demonstrated nearly 12 lb and 9 lb of impact resistance (Dynatup), respectively.

High-density polyethylene inserts from Beacon Converters can be used in header bags or pouches for surgical kits. Devices courtesy of Guidant Cardiac & Vascular Surgery Group. (The insert shown is typically packaged in a pouch.)

In 1998, Perfecseal (Oshkosh, WI) introduced its own single-site-catalyst film using linear low-density polyethylene (LLDPE), calling it ShieLLD. "When produced at a 3-mil gauge, ShieLLD demonstrates 150% more impact strength than conventional 4-mil LLDPE film. At 4 mil, ShieLLD's impact strength is 238% more than other types of 4-mil LLDPE, with 250% greater tear strength," according to the firm's literature. "The strength and durability of ShieLLD make it ideal in header-bag packaging for large, bulky devices or heavy trays containing a variety of instrumentation."

"We have transitioned a lot of medical products out of conventional linear low-density films into ShieLLD," says Bill Wetzel, director of marketing– rollstock. "You get comparable if not more strength at a lower cost."

Nylon-based structures also offer packagers strength in flexible packaging. Perfecseal's PerfecFlex Ice, a blown nylon/polyethylene film, provides strength as well as puncture resistance. It requires greater than 200% more force to puncture it when compared to traditional EVA/Surlyn/EVA films. "Nylon can be used for heavy devices with protuberances, like blood oxygenators," says Wetzel.

"Nylon is also known for its abrasion resistance and overall toughness," adds Goodwin, "so device makers can consider it for large, bulky procedural kits or devices. They may be able to consolidate several devices into one package."

Kenpak (City of Commerce, CA, and Marshall, NC), a division of Pechiney Plastic Packaging (Chicago), has leveraged its patented Kwikbreathe aeration header strip system with its new Kenpak bag film. Says Scott Keller, director of sales for the Kenpak brand, "In flex cracking and pinhole resistance testing, the Kenpak film at 4 mil outperformed competitive 5-mil structures by more than 100%. An equivalent-caliper Kenpak film outperformed competitive structures by 202%." Also, Pechiney has just unveiled its DirectSeal coextruded thermoformable films, available in both nylon or nonnylon structures, with a sealant layer that enables them to be sealed to uncoated Tyvek and paper. Available for shallow, medium, and deep draw applications, DirectSeal is available in 4- to 12-mil gauges. A 4-mil film, for instance, offers tear strength from 300 to 760 g.

Rollprint Packaging Products Inc. (Addison, IL) has recently introduced a durable, pinhole- and puncture-resistant linear-tear vent pouch using a blend of new polymer technology. The film has three times the impact strength of traditional linear-tear films, which allows for downgauging, and still provides ease of opening.

Also, in late 1999, Rollprint launched FlexFormB, a thermoformable monolayer film available in gauges from 3 to 12 mil, with a blend of polyolefin-type resins. Craig Livingston, vice president of sales, says FlexFormB offers both cost savings and increased durability over the more-traditional EVA/Surlyn/EVA coextruded formable bottom web films and has cost savings as well as improved forming performance over the nylon-based forming webs. Along with the introduction of FlexFormB came FlexFormT, which is Rollprint's thermoformable trilayer film of EVA/polyolefin blend/peelable sealant. The coextruded sealant will provide peelable seals to uncoated paper and Tyvek that are comparable to seals to coated paper and Tyvek in both functionality and appearance while providng more durability than standard thermoformable films.

Surlyn ionomer resin from DuPont Packaging and Industrial Polymers (Wilmington, DE) has been used in the medical packaging industry for years. Its formability, toughness, abrasion resistance, and stiffness make it an excellent choice for a wide variety of forming applications. Ethicon Endo-Surgery's replacement of rigid trays with Surlyn-based Integra Form C-Film from Rexam for surgical device packaging won FPA's Green Globe Award for environmental achievement in 1997.

Rexam's Integra Pack Tuf 1000 can withstand 12 lb of impact resistance.

Advances are also occurring in lidding. While Tyvek maintains its position as the strongest and most puncture-resistant top web, Kimberly-Clark Technical Paper (Roswell, GA) continues to work toward offering a paper that offers comparable properties. The paper maker currently uses polymer impregnation to produce a coated paper that offers "middle-of-the-road" strength properties between kraft paper and Tyvek. It is, however, developing a new uncoated paper for sealing to the new coextruded films. The new design is currently undergoing evaluation.

DEVICE SUPPORT

The strength of these materials won't matter much if the devices themselves are left to slide around and knock into one another while inside the package. One of the distinct benefits of the tray is its ability to hold products in place.

Flexible-packaging providers, however, have devised a number of ways to offer similar in-package security. By adjusting sealing configurations, die-cutting unique shapes, or employing inserts, suppliers can offer flexible packages that hold devices in place just as securely as some rigid packages can.

Mangar Industries Inc. (New Britain, PA), a flexible-packaging converter that specializes in custom-designed bags and pouches, uses a number of design techniques that secure products. "We can custom design seals for products that require more stability inside the pouch," explains Roger Allan, director of research and development and technical services. "We create what we call bumper seals and internal locator seals to create multiple-cavity pouches." Not only do the internal seals hold the various devices in place inside the package, but they also prevent heavy devices from stressing the outer seal.

To protect these outer seals, Rexam has developed an optional patented reinforced end seal for its Tuf 1000 header bag to prevent package contents from breaking the seal.

Such unique sealing configurations may also help with presentation of the device in end-user settings. Scott Dykstra, product and process development engineer for Oliver Products Co. (Grand Rapids, MI), says that he has helped design pouches with partitions to divide different components or ingredients. For example, he has seen such pouches with a catheter sealed into one part of the pouch and its components sealed into the other.

Another way to keep devices stable inside pouches is to design the pouch around the product. Oliver has begun die-cutting pouch materials in sheet form into different shapes to create shaped pouches. "Through die-cutting, you can have an infinite number of shapes, including curves and cuts," says Dykstra. "There is less material in the finished pouch, which reduces end-user waste and makes the pouch easier to handle." One of Oliver's customers uses such a shaped pouch as a holder for a device that goes into another pouch.

In addition to modifying seals, end-users can rely on inserts to position devices in place. Paperboard is often used as an insert, but manufacturers whose devices are to be used in sterile environments are concerned about the particulate that paper can generate. To address this concern, Beacon Converters (Saddle Brook, NJ) has developed a high-density polyethylene insert that produces virtually no particulate.

Guidant Cardiac & Vascular Surgery Group (Cupertino, CA) uses Beacon's inserts for two of its procedural kits, the Aurora and Ceres lines. "The die-cut insert locks all the kit components in place, and it is easier to snap parts into and out of place during loading and unloading without the worry of ripping the insert," explains Guidant's packaging engineer Bill Jautz. "Also, nurses and doctors find that the die-cut handle makes the kits easier to transport."

The time and costs associated with blister tray development as well as paper concerns urged Jautz and his team to investigate plastic insert use. Says Jautz: "It would have been too much development time wasted on a lower-volume product line, which is what the Aurora and Ceres are. Also, there were too much assembly time and too much particulate associated with a paper insert." Instead, "there is minimal tooling development with the plastic insert, and it is easier to prototype and to modify if product design changes during development. We needed to be able to make changes quickly, and we could not hold up product launch," he adds.

RELYING ON SUPPLIERS

The best way to determine whether to go rigid or flexible is to consult your packaging suppliers. Most are willing to investigate a number of options in order to meet the needs of your device. Many converters even create a new product line based on similar inquiries from various end-users. Tolas Healthcare Packaging, for instance, just introduced its new line of pouches called Dispose-A-Vent for devices that need to be protected from oxygen or humidity, yet need a breathable packaging component for EtO sterilization. The new line combines a primarily foil pouch with vents of Tyvek. The package is first sealed and sterilized. Then, after aeration, the package is sealed again to remove the vents. "The pouches are designed for devices sensitive to radiation and steam, like implantable devices that are eventually absorbed by the body," explains Tolas's president Carl Marotta.

Unfortunately, most device manufacturers appear to choose the same packaging materials they've used for years for their new products without investigating newer packaging materials and styles. Such a reluctance has left many device makers behind the times in terms of packaging advancements and perhaps even in savings. For instance, Kenpak's Jack Roten says that he has come across many firms that are using structures that could be downgauged significantly. "We can downgauge some of the older structures to a more modern coextrusion or structure, to help firms save money," he says.

"In the long run," Roten continues, "manufacturers will have to get into smarter packages. We can do a lot of testing, and we can share a lot of the data we have, to make it easier on them. Once they get through such evaluations, they will be able to reap the benefits of modern structures."