Forming Rigid Barriers
Device makers are investigating gas barrier options for rigid packaging and addressing material costs.
David Vaczek, Senior Editor
|Alcoa Custom Thermoforming produced a PCTFE/PETG laminate outer tray with a 1.4-in. draw for packaging a human tissue product.|
Rigid packaging needs to exhibit a variety of basic properties. Medical device packagers and converters look for materials with good thermoforming characteristics, as well as those that are impact and heat resistant. They often look for clarity so that end-users can clearly identify package contents. Sterile barriers, sterilization compatibility, sealability with a range of lid stocks, and stability under accelerated aging are other concerns.
More recently, companies have required oxygen- and moisture-barrier characteristics for device packaging to protect human tissues and drug-coated or absorbable devices.
“This has become the next area of focus for rigid packaging. Companies are considering a product’s shelf life and whether better oxygen- and moisture-barrier properties are needed,” says Peter Giczewski, vice president and general manager, Barger Packaging (Elkhart, IN).
Firms requiring such protection will also have to consider new lidding options, and new sterilization techniques, in some cases, says Alison Tyler, marketing manager, Alcoa Custom Thermoforming, Alcoa Packaging (Richmond, VA). “Material selection is going to change. We expect to see a significant increase in demand for higher-barrier materials” that will affect customer choices in trays and lidding. “More devices have drug coatings requiring moisture- or oxygen-barrier protection, in addition to the microbial barrier protection that firms need for sterile devices,” says Tyler.
Assessing Aclar and Other Barriers
When searching for barrier materials, companies will have to establish the thermoforming characteristics of materials not traditionally used in device packaging. PCTFE, for example, requires specific heating parameters and tool design. To date, the rigid thermoforming industry lacks information on PCTFE’s performance in deep-draw applications.
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“We have felt the demand for barrier materials grow for the last 12–18 months. There seems to be a great deal of interest in PCTFE,” such as in laminations with PETG, says Walter Walker, executive vice president, operations, Prent Co. (Janesville, WI).
Walker says that companies are looking for guidance with new materials. Prent’s product development team often works as an extension of firms’ R&D departments and may develop models that customers then have to test and fully qualify. “We are motivated to look at new materials by our customers. But the burden of proof really falls on them as to whether a product is successful,” he says.
“Aclar (PCTFE) has excellent moisture-barrier properties and has proven highly suitable for pharmaceutical packaging, where the chances of losing moisture-barrier characteristics as a result of drawing down the plastic is minimal,” Walker continues. “What we don’t have is information on how far down you can deep-draw it without jeopardizing moisture-barrier characteristics. The barrier properties published for Aclar pertain to flat-sheet stock. There are few values available on any type of postforming draw ratio. You can run into problems with PCTFE if you try to draw it down much more than an inch or an inch and half, where you may lose barrier characteristics in the bottom corner radii of the tray.”
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Prent’s customers have used PCTFE in 1-in. trays. “But we have not done enough with it to have a handle on the barrier beyond that range,” says Don Handrow, senior package design team leader. One alternative for realizing barrier protection is to put a rigid tray into a flexible barrier pouch. Prent customers have used pouches made of Mylar foil or Aclar laminates in this application, says Handrow.
Measuring ultimate-barrier characteristics is complicated by the fact that Aclar is being used in a wide range of thicknesses—from 0.004 to 0.0006 ml —and in multiextrusions with PVC or PETG. Those plastics have their own barrier properties that will affect the barrier value, Handrow says.
For barring oxygen and moisture, some Alcoa customers have used Barex. But more customers seeking higher barrier will be looking at PCTFE laminations, says Tyler. For instance, for a firm packaging a human tissue product requiring a high level of moisture protection, Alcoa has provided a PCTFE/PETG laminate outer tray with a foil lid. The inner tray is PETG with a Tyvek lid.
“It’s a relatively deep-draw package, more than an inch in depth, with very forgiving draft angles, designed to have optimal material distribution. Since Aclar is a crystalline material, tooling design and heating control become extremely important for maintaining the barrier. Unlike foil, PCTFE offers barrier that increases or decreases with its thickness. You have to make sure your thermoformer understands the material,” she says.
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When using foil and foil laminates for lidding, device makers will need to consider some unique issues. “The adhesive system becomes much more important when you are dealing with nonbreathable lidding materials, because you can get significant pressure differentials in sterilization and transport,” she says. And companies using foil might have to alter their sterilization processes. The Tyvek headers employed in flexible packaging to support gas sterilization of barrier-material packages cannot be used in rigid packaging.
Foil lidding “eliminates your option to use ethylene oxide (EtO). Companies replacing Tyvek with nonbreathable lidding would have to gamma- sterilize. Clearly this is an opportunity for innovation, because gamma sterilization is a high-energy process. Companies with products that can’t withstand gamma might have to switch from a terminal sterilization process to an aseptic process,” packaging in Class 1000 (ISO 6) or Class 100 (ISO 5) cleanrooms, Tyler says. The packaging components would be sterilized prior to the packaging operation. The result is a packaged product free of pathogenic microorganisms.
To support cleanroom operations, Alcoa is consolidating its thermoforming operations in Illinois and Rhode Island at a pharmaceutical and medical packaging center of excellence at its Downington, PA, location. The facility will host technical thermoforming processes in a newly constructed Class 100,000 cleanroom environment.
Perfecseal (Mankato, MN) has tested Aclar laminated to PETG and Daicel/Polyplastics Group’s Topas cyclic olefin copolymer (COC) as moisture-barrier alternatives in rigid packaging, says Steve Olson, project engineer.
With the availability of thermoforming-grade polypropylene, some converters are focusing on polypropylene as a suitable material for moisture barrier in medical packaging.
“Until recently, you couldn’t get a good thermoformed version of polypropylene,” says Sam Mazzola, president, Tek Packaging (Huntley, IL). “It had to be modified so much that it lost its characteristics. We have been able to thermoform it successfully, and we are finding more applications for it.” Mazzola notes that clarifiers have been introduced for adding to the resin to give it the “glass-clear” clarity that the market wants.
Polypropylene is strong, yet highly elastic. Also, it is recyclable for reuse in more applications than other plastics, says Ruben Fonseca, plant manager, House of Packaging (City of Industry, CA). “The thermoforming grade of polypropylene has considerably improved, so that it can be used in more-traditional thermoforming applications. Polypropylene will find its place in the market because it is not as brittle as PETG. You could add ribs to a polypropylene tray to make it stronger,” Fonseca says.
Though polypropylene has improved for thermoforming, the plastic still faces processing hurdles—it can distort when heated. To promote uniformity, House of Packaging is installing a Sencorp 2500-series thermoformer with a built-in cut-in-place function for converting the material. In cut-in-place, material is formed and cut almost simultaneously, which supports uniform, consistent die-cut registration. “The product is perfectly stationary inside the cavitation when it is cut, allowing precise flange diameters,” Fonseca explains.
He notes that the Sencorp unit also features sheet-advance registration for handling preprinted webs. “Sencorp’s machine will provide us with a much cleaner registration as we start to experiment with polypropylene. We plan to develop tool design to offer a marketable product for the medical device industry,” he says.
“Polypropylene is a lot softer than PETG, so you have less chance of cracking through the transportation cycle. However, PETG has consistently demonstrated high performance under the stresses sustained in shipping,” says Giczewski of Barger Packaging.
Although packaging is not the most expensive element for medical device makers, companies have been motivated to address cost after resin prices have increased 50 to 80% in the past 12–18 months. “We have just gone through some very serious resin price increases,” says Walker of Prent.
More companies are considering using postindustrial regrind material. “They would not have looked at this except for the price increases and shortages in feed stock and processing material. The medical industry is saying that it could possibly use this on thicker packages in the 0.040- to 0.070-ml range. Packages could use virgin material on both sides in a closed-loop regrind coextrusion. Firms are exploring this now with FDA, Walker says. As another cost move, Tyler says that film gauges for in-process trays used to protect devices during product assembly are being increased to make them stronger and thus reusable. Some companies have reduced costs by replacing two-tray configurations with tray and bag systems. And converters can help companies with costs by redesigning overbuilt packaging. Perfecseal recently helped American Medical Systems (AMS) achieve major source reduction gains in packaging for implanting devices, Olson says.
A barrier outer tray was discontinued and remaining trays were downgauged from 0.04 to 0.030 mm. “AMS’s trays were made from PETG without an antiblock coating, which meant that a thin layer of polyethylene tissue needed to be interleaved between each tray so they could be denested. By using internal denesting PETG, we were able to eliminate the need for the tissue interleaving without creating any lid-sealing issues,” he says. (For more details, see the sidebar on page 91.)
Consolidated trays have offered a cost alternative for many companies. Firms get better pricing because of economies of scale and have fewer SKUs to manage, says Olson. “Universal trays” are attractive because firms can use common heat-seal dies and Tyvek or paper lids. “These trays also provide the opportunity to use common outer packaging components like trays, cartons, and shipping boxes. The challenge is to make these types of trays multifunctional without compromising the trays’ ability to confine and protect the product,” he says.
Single-platform trays “are a win/ win for us and our customers,” says Giczewski. “We might develop two or three outer trays to accommodate a company’s entire product line. For a new product, they don’t have to buy four or five part numbers, just an inner tray. The inner tray has the same sealing flange, so you don’t need a new sealing fixture or new Tyvek die. On our side, we have faster speed to market, and we can spend more time servicing customers and on new product launches. And hospitals have fewer boxes to store.”
Converters are achieving efficiencies in parts production that often translates into lower end-user costs. Perfecseal has upgraded conventional in-line formers with the addition of two new pieces of thermoforming equipment that automate certain processes.
“These machines can significantly reduce the piece price of thermoformed trays and are built for higher-volume production,” says Olson.
Tek Packaging has gained production efficiencies using the Speed Former machine launched last year by Kiefel Technologies Inc. (Hampton, NH). Tek has purchased seven machines that feature preprogrammed recipes and are entirely servo-driven with drives integrated into the PLC. Depending on material gauge, thickness, and depth-of-draw, they run at up to 70 cycles per minute. Side-load key-way groove-and-flange retooling increases operating capacity and reduces man-hours, says Mazzola.
“Before, we had to wheel up a Craftsman tool cabinet. Here, we are using a crescent wrench to lock-and- load from the side. We have gone from a 4-hour make-ready to 30 minutes. So we can use fewer machines and fewer people to achieve the same capacity,” he says.