Medical Device Link.

Originally Published PMPN April 2003

RIGID PACKAGING

When choosing the best material and design for your tray, first consider your product's needs.

Kassandra Kania, Managing Editor

Material choices for rigid medical packaging haven't changed much. That's because those available work well, say experts. To determine the best material and design for your tray, first consider your product. "The number one criteria in choosing materials is the requirements of the device you're packaging," says Jennifer Lauderback, senior market development representative, Eastman Chemical Co. Experts suggest careful consideration of the following before making a decision.

Materials. The most common choice is still PETG, which continues to gain in popularity, because of its clarity, strength, and good formability.

If clarity is not an issue, high-impact polystyrene (HIPS) provides a less-expensive alternative, says Dave Rosten, sales manager for Brentwood Industries (Reading, PA). According to Richard Ryder, Klöckner Pentaplast of America's business manager for medical device films (Gordonsville, VA), HIPS has long been used for medical device packaging due to its excellent thermoformability and its low specific gravity (about 1.05), which give a relatively high material yield. "It is normally a translucent/hazy product," he explains, "but is often pigmented to opaque white or, less often, to black for use in medical device packaging—generally trays with Tyvek seals. Also, HIPS can be gamma sterilized and is FDA approved."

Polypropylene (PP) is used less in medical device packaging than HIPS, says Ryder, although it does have a lower specific gravity at 0.99 and as such would have a material yield advantage. "Polypropylene is much more difficult to thermoform with a narrower window for forming," he says. "Talc-filled PP versions can withstand higher heat than HIPS. It can be sterilized by gamma, electron beam, and EtO, with PP copolymers best suited for gamma. Also, PP has better chemical resistance and gas barrier properties than HIPS."

PVC is another less expensive alternative, and it has good impact strength. However, some experts see its use in trays declining for a number of reasons, including discoloration if it is gamma sterilized, which limits the sterilization method used. Some companies selling to the European market are moving away from PVC and other materials due to environmental concerns. "A lot of people have been moving to PETG mainly because the European market won't accept other materials," says Paul Treible, engineering manager, Computer Designs (Whitehall, PA). "Europeans want a PETG material because they incinerate their waste, and PETG is a clean burning material. Other materials, like HIPS, vinyl, and PVC, do not incinerate well."

Another material used on a more-limited basis is Barex. According to Ryder, Barex "offers good oxygen and gas barriers, inherent denest (no silicone coating required), and also thermoforms extremely well."

Polycarbonate is also an option for trays, says Scott Felder, Mankato, MN, plant manager, Perfecseal (Oshkosh, WI). It can be sterilized using dry heat and offers good clarity, he says. However, it is very expensive. And for medical devices that are coated or contain a microbacterial product, greater barrier protection may be required. In these instances, Aclar can be used in medical trays, says Sandy Luciano, senior market development specialist, Honeywell (Morristown, NJ), because it offers good barrier protection. However, because it is a crystalline material, Aclar requires specific heating and tool design to maintain its barrier once it is thermoformed. Some companies thermoform it with PETG because they need the rigidity of that material for protection, she says.

Sterilization. When choosing the right material for your tray, determine what type of sterilization method is being used. Gamma and EtO are the predominant sterilization methods, and both are compatible with PETG. Some experts are noticing a trend away from EtO toward gamma sterilization. PVC, on the other hand, is not suitable for gamma sterilization. "If a company's sterilizers are gamma sterilizers, they don't have the opportunity to use PVC," says Felder. "Most medical companies do not have their own sterilizers. They may be limited in choice of sterilization, and that might cause them to choose one material over another." On the other hand, "when products are redesigned, quite often the company also reanalyzes the sterilization process they're using," notes Randy Scott, business market manager for packaging, specialty plastics group, Eastman Chemical Co.

Weight, Shape, and Size. The weight and dimensions of a device will play an active role in the design of the tray and the type of material used. Felder sees a lot of heavy devices being packaged in trays, such as orthopedic devices, catheters, pacemakers, and other implantable devices. Most of these companies are choosing PETG due to its clarity and impact resistance.

Lauderback also notices a trend toward bulkier devices. "The trend is toward more kit manufacturers having a complete system in one tray instead of multicomponent packages. Parts are getting larger, often because there are various components of the surgical procedure all in one kit," she says. Heavier devices will also need a tray that secures the product well. "In some cases, it may be possible to more securely package a product by making a tray that's molded to the shape of the article," says Jeff Wooster, value chain manager for the Polyolefins and Elastomers Business Group of The Dow Chemical Co. (Houston). In these instances, the material should have excellent flow properties, says Wooster, while maintaining its toughness and impact resistance.

The size of the device will also help determine the depth of draw. "How deep are you going to go with this tray, because some materials are too brittle to give you the amount of protection you need in a drop test," says Luciano. "If it's too rigid or too deep, you could get some cracking in the corners." To address this concern, suppliers need to offer films that perform, says Scott, and provide new parameters in terms of undercuts and thermoforming depths.

Brentwood Industries is currently forming trays that are 12 and 13 in. deep, and Rosten is seeing an in-creased interest in this area. "Generally, those are formed using high-impact polystyrene," says Rosten. "We also have a machine that can form up to 70-in.-long catheter trays." The company adds a rubber agent to the polystyrene to make it tougher so it doesn't crack, he explains.

Use. Most of the medical devices packaged in trays will end up in a hospital setting. In this instance, the clarity of the material is important. "People want to be able to see and inspect [the device]," says Luciano. The design should also be kept simple and allow easy removal of the product. "The hospital or surgeon is very aware of how the product is used," says Treible. "You have to be careful how it's presented—consider the sterile or nonsterile area. They want it to be very clean and simple."

Ease of opening is another important design element, says Pam McMaster, founder and CEO of Pro-Tech (Los Angeles). "We always look for ways to give nurses choices by designing multipurpose trays. They can be dumped onto the sterile field or have adequate pick-out areas so that the component parts can be removed from the tray and placed on the sterile field," she says.

Space. Most hospitals lack storage space, says Chuck Ortwein, sales executive for Computer Designs, so there is emphasis being placed on reducing total package size. The company helped Tyco Healthcare (Mansfield, MA) address this concern by reducing the amount of trays needed for its lumbar puncture kits. Initially, explains Carl Sadowski, senior packaging engineer for Tyco, the goal was to add the company's Monoject Magellan safety needle to the kits. "While we were looking at that option, we decided to look at reducing the number of product codes down to one tray," Sadowski says. The lumbar puncture kit consists of four or five coded products, which are similar to each other. Each code had its own polystyrene tray, and each tray was designed for a specific procedure, such as an adult or an infant procedure, explains Sadowski. Since some of the procedure kits differ only slightly, the company decided to use the same tray for the four different products. Computer Designs created one large two-part tray with more compartments. The internal cavities were also changed to fit all of the components from the separate kits. The components were labeled according to their product code. "Because some of the components differ slightly, we were able to make a multicompartment cavity that would fit, say, a certain catheter in a number of different ways," says Sadowski. "Some of the cavities are fixed, so if you had a component that was in four of the separate trays, you would have those same components in one tray." The new design has reduced the number of trays hospitals have to purchase from four to one and has also reduced the overall size of the tray.

Photo of trays courtesy of Perfecseal (Oshkosh, WI).

Cost. Although companies want to reduce the cost of their packages, switching to a less-expensive material or a flexible package doesn't always make the most sense. Companies must carefully consider the nature of their products before making these decisions. "Saving a bit of money by switching from a tray to a flexible package doesn't make sense for a ball-joint replacement that goes for $3000," says Scott. McMaster has noticed a trend toward combining trays and pouches to reduce costs. "In the past, companies have used a two-tray system. Now they're eliminating the outer tray and making the second sterile barrier a pouch."

The desire to reduce packaging costs has also lead to downgauging of materials, which is made possible by advances in material science, notes Wooster. "When you reduce costs, it doesn't necessarily mean you reduce the price of the polymer you're using, but you reduce the overall cost of your system," he says. "So, if you can use a slightly more-expensive polymer that only requires 75% of the weight to make the package, even if you pay a little more per pound, you're saving money. If you can run a polymer that processes more easily on equipment so you have less scrap, you're saving money. If you have a polymer that allows you to run equipment faster, you can save money because you can make more [trays], and you don't have to invest in new machinery."

While some companies may be moving toward flexible packaging due to cost factors, there will always be a need for rigid packaging. Careful consideration of the above factors will help you determine which materials are best for your tray and what design is best suited to your device.

Copyright ©2003 Pharmaceutical & Medical Packaging News