Rigid Packaging: Finding the Right Rigid Materials
When it comes to manufacturing rigid packaging for medical devices, it’s all about the materials.
Ben Van Houten
These days, manufacturers have many choices when it comes to deciding which materials to use for rigid packages. From polyethylene terephthalateglycol (PETG) to high-density polyethylene and polyvinyl chloride, there exists a wide range of rigid packaging products for medical device packagers in particular.
However, the most important factor in rigid packaging is, and always has been, protecting the contents of the package—whether it’s an orthopedic implant, catheter, or syringe. That’s why more and more companies are seeking out materials that are stronger and better able to withstand the effects of radiation and heat aging. And that is becoming even more important today, as medical devices are more compact and fragile than ever. “As device manufacturers continue to introduce enhanced products, we have to find a way to bring innovative solutions,” says Peter Giczewski, vice president and general manager of Barger Packaging (Elkhart, IN). “And the packaging has to be able to put up with more-stringent shipping tests and maintain package integrity. That’s a big challenge.”
Barger is one of the companies experimenting with new rigid materials. “A rigid medical package’s barrier material must have excellent abrasion-resistance characteristics,” says Giczewski. “It also has to be able to withstand ethylene oxide and gamma irradiation sterilization and have a long shelf life.”
Based upon those requirements, the company has developed a material known as ST1880-87, a urethane material that has been formulated for vacuum forming and sealing and can be manufactured as a blown film, tubing, or as sheeted film. “It allowed for better enhancement of our sterile packaging,” says Rod Patch, director of packaging engineering for DePuy Orthopedics (Warsaw, IN), which partnered with Barger on the project. “It has nonabrasive surface characteristics and is very acceptable for thermoforming. It also produces less scrap, requires less processing time, and is a lighter weight than many other packaging materials.”
As Giczewski explains, sterile medical device packages typically employ a primary rigid cavity that allows direct sealing of a sterile barrier. This cavity, usually made from PETG, also needs to contain an internal package to eliminate the possibility of direct contact with the rigid packaging. “That barrier between the component and the rigid package is essential to prevent flaking or chafing of the PETG,” he says. “It becomes very important than no particulate gets into the package at any time over the life of the package.” To that end, the ST1880-87 material is designed to add that type of protection to orthopedic devices in particular. “It also protects well against the effects of high humidity and contains enhanced ultraviolet stability,” says Patch. “And it is environmentally friendly and biodegradable as well.”
Barger has also developed ST-1880, another version of the material designed for use in multiple product lines, not just orthopedics.
|Barger Packaging created a new urethane material for several medical devices manufactured by DePuy Orthopedics.|
Clean Cut Technologies (Fullerton, CA) is also using stronger materials, having recently introduced its CCT Clipless Dispenser, a rigid guidewire and catheter dispenser. The product is manufactured with biocompatible high-density polyethylene (HDPE) tubing in different inner and outer diameters and lengths. The material has been prequalified following 100% EtO and gamma sterilization cycling, according to Howard Rowe, president of the company. He explains that the material also provides the ability to bond a custom HDPE die-cut packaging card to the dispenser. “It is a very strong material, and hence a very strong, rigid package,” he says. The coils are validated to ensure the tubing strength will fail before the bond holding the coils together fails. This allows customers to place various device components onto the primary-package delivery system, he says.
Another company, custom converter UFP Technologies Inc. (Georgetown, MA), recently created rigid packaging for several delicate orthopedic implants produced by a U.S. medical technology company. UFP used a thermoformed plastic blister as the package’s outer protection, and then it installed a piece of compression-molded foam inside to help secure the implant within the package. The foam also helped prevent cracking of the tray during transport, according to Dan Shaw, vice president of product development for UFP. He adds that the package was created in the company’s on-site cleanroom facilities, enabling the orthopedic manufacturer to sterilize the entire product without compromising it.
Another company, Eastman Chemical Co. (Kingsport, TN), has been fine-tuning its Eastar copolyester material for the past several years, according to Thijs Jaarsma, global market development manager, medical industry. Specifically, this rigid material has been used for porous coated bone implant devices. “It’s known for its strength, durability, clarity, and thermoforming ease,” he says.
Tray-Pak (Reading, PA), a thermoformed packaging manufacturer, has introduced several new products over the past few years, according to Randy Simcox, executive vice president. Sealable PET, which is an alternative to PVC, is one such material the company has been producing. “It’s mainly a reaction to the increased costs the last few years,” he says. “Last year in particular, raw material costs went way up, partly due to rising oil prices. As a result, there wasn’t a lot of capacity out there, so it’s become harder for companies to manage and stabilize costs. With rigid materials, cost management is always the biggest challenge to begin with, but it got tougher last year.” That’s one reason why Tray-Pak has been working with more polystyrene recently. “That’s a lower-cost option,” he says. “We want to make sure we’re providing that to companies. It’s very difficult to introduce new rigid materials that are dramatically different these days, because of that expense.”
Yet Rod Patch from DePuy says that is inevitable if a company wants to stand out from the competition with new rigid materials. “It’s always a challenge, both for the manufacturer and the device company,” he says. “But we found that, with our ST1880-87, it has a level of flexibility or formability that other materials just don’t really have. In fact, the costs could have been much higher, but we were able to keep them down as much as we could.”
|Rigid packaging from custom converting company UFP Technologies Inc. was designed to protect delicate orthopedic implants.|
Dick Simmons, senior marketing director for the technical packaging division of Alcoa (Wheaton, IL), agrees. “It can be a drawback, but you want to give the end-user the best material out there,” he says. Although Alcoa still mainly produces common rigid materials such as PETG, PVC, and polystyrene, Simmons says that the company is constantly working on new rigid materials in its laboratory. “It can be competitive, even with high costs involved,” he says. “You want to make sure you’re exploring new technology if you can.”
According to Dan Shaw of UFP, medical devices have very diverse packaging needs, so certain conversion processes may be more suitable for a certain product. Many titanium-based devices such as hip implants require the additional cushioning of compression-molded foam to keep the package’s thermoformed tray from cracking and to protect the product from damage during shipment, he says. This is why companies should consider the use of a wide range of materials, recognizing that not all rigid plastics are the same. He says that PETG, which is particularly effective in withstanding gamma radiation, can be a good choice for medical packagers. In addition, rugged and durable polyurethane films can be flexible enough to accommodate sleek designs and pouches.
Shaw also recommends that rigid-material suppliers use a variety of processes such as die-cutting, thermoforming, compression molding, and heat sealing.
Standing Up to Heat
One of the most important factors of a rigid material, most agree, is its ability to withstand extreme temperatures. “You want a material that is performance enhancing and stands up to temperature without cracking,” says Tray-Pak’s Simcox. “It needs to be sterilized, too, so it has to be compatible with that at the same time.” Simcox adds that polypropylene makes a good thermoforming material for these reasons. “It holds up to high heat the best of all the materials, in my opinion, and shows more stability,” he says.
|The clipless dispenser from Clean Cut Technologies is made from HDPE.|
Eastman, which uses rigid plastics in both pharmaceutical and medical device packaging, is another company committed to producing materials that are known for outstanding physical properties. “Extreme heat and puncture resistance are important,” says Eastman’s Jaarsma. “Eastman customers expect such top-notch physical properties.”
Indeed, rigid materials need to demonstrate solid impact strength and compatibility with sterilization methods over extended periods of time, according to Dimo Dimov, PhD, process/applications development manager, Cyro Industries (Rockaway, NJ). Dimov recently coauthored a study that analyzed the effects of heat aging on several common rigid medical packaging materials. “We wanted to help engineers evaluate materials for medical packaging applications,” he says. “The retained strength of rigid medical packages is important for adequate protection through the rigors of storage and transportation.”
The Cyro study compared a PETG copolyester resin with three grades of acrylic-based multipolymer compounds. All resins were tested for property retention upon exposure to heat aging. Physical, thermal, and optical properties were monitored at specified time increments, and the heat aging characteristics were compared on the basis of the observed effects, says Dimov.
One material sample was sterilized using EtO, while the second sample underwent heat aging without sterilization. The sterilized samples were exposed to temperatures in the 125º–145ºF range with 4 hours of exposure time. The materials were then aged for 24 weeks in accordance to the conditions of ASTM D-3045. All samples were tested at five intervals: at 0, 3, 6, 12, and 24 weeks.
Dimov says the tests’ results indicated that PETG might not be that effective in withstanding sterilization, another reason companies may want to explore new materials. “In our test, all grades of the acrylic-based compounds remained stable during the heat aging and had slight discoloration,” he says. “In contrast, after only three weeks of heat aging, the nonsterilized PETG’s elongation at break dropped by approximately 50%.”
Meanwhile, acrylic-based multipolymer compounds were stable through 24 weeks of aging in both sterilized and unsterilized samples and showed 100% property retention during sterilization and heat aging. “Basically, we found that the heat-aging process carries significant loss of performance properties in PETG. The PETG copolyester suffered significant property changes, most notably embrittlement,” says Dimov.
Still, there are many factors to consider when choosing rigid materials, says Tray-Pak’s Simcox. “Rigid packaging on the whole is still a very viable and competitive platform,” he says. “One material is not vastly better than another. It’s up to the device company and what its specific needs are.”