Webcast Wrap Up: DuPont Medical Packaging Educational Seminars

Experts from DuPont address some questions frequently asked by medical device manufacturers.

In a special global packaging online community, PMP News and DuPont Medical Packaging presented two Web events: “An Introduction to DuPont Tyvek” and “Fundamentals of Medical Package Engineering and Design.” Speaking were Jose R. Arevalo, business development manager, MDM accounts and Latin America, DuPont Medical and Pharmaceutical Protection; and Karen Polkinghorne, Packaging Engineer & MDM Specialist, for DuPont Medical & Pharmaceutical Packaging. The two received several questions during their respective events, and together they provide written responses to several questions.

The next Webcast to be held in the community, “DuPont Tyvek in 2012 and Beyond,” will be held April 4, 2012. It will feature Dr. Mike Scholla and members of the DuPont Global Medical Packaging Team, who will fill attendees in on progress in the transitioning of Tyvek 1073B and Tyvek 1059B to manufacturing lines that use its latest flash-
spinning technology.

Visit www.pmpnews.com/webinars to access the community sponsored by DuPont. Technical information is available for downloading.

Q: Do bacteria and microbes have motion, or do they move with air flows and pressure differentials?

A: Microbes have no mechanism for physical movement in air other than air flow or attachment to animate or inanimate objects that move. In liquids, some species have the ability to move directionally using a mechanism known as motility.

Q: At what point in the process do you separate the rolls into different types of Tyvek?

A: The main difference between the various styles of Tyvek for Medical Packaging (i.e., 1073B, 1059B, Asuron, 2FS) is basis weight of the finished sheet. The units for basis weight of Tyvek are typically defined as oz/yd² or g/m². Basis weight is determined by the amount of high-density polyethylene fibers comprising the sheet, which happens during the spinning process.

Q: Can you place gels and creams in Tyvek pouches and sterilize?

A: Gels and creams usually are required to be packaged in a non breathable type of package so that moisture levels can be maintained. Since Tyvek is breathable, Tyvek may not be a suitable packaging material.

Q: Is Tyvek for medical packaging produced in a cleanroom environment?

A: Tyvek is produced in a clean environment but not under cleanroom

Q: Does DuPont recommend pull testing with a backing plate due to the variance in material thickness?

A: DuPont recommends medical device manufacturers and their pouch or bag suppliers use the same testing for seal strength. Either with or without the backing plate is acceptable. Testing without a backing plate can produce varying results due to the stiffness of the materials being testing.

Q: Can printing methods that employ UV light curing methods for ink be used?

A: Yes. The UV exposure time is minimal and may not affect the Tyvek sheet properties. The end user should determine the optimum curing conditions for their process to ensure desired performance.

Q: Is creasing or folding of Tyvek not recommended?

A: Folding any flexible packaging material, including Tyvek, is not recommended due to the potential to induce various defects. Please see the DuPont Technical Reference Guide at www.medicalpackaging.com.

Q: What is max pore size for Tyvek medical device packaging?

A: Tyvek is composed of layers of fibers that create a tortuous path and result in an excellent microbial barrier. Microbial barrier is measured using ASTM F2638 or ASTM F1608, which ranks the performance of porous substrates and their ability to hold out microbes. Microbial barrier is measured by testing a specified area of material not by measuring the space between individual fibers.

Q: What is the typical or smallest size of bacteria?

A: Bacteria range in size from approximately as small as the largest viruses to large enough for single cells to be visible by the naked eye. That is, from about 0.1 to about 600 µm over a single dimension. The smallest (e.g., some members of the genus Mycoplasma) are about 100 to 200 nm in diameter, approximately the size of the largest viruses (poxviruses). Escherichia coli, a bacillus of about average size, is 1.1 to 1.5 µm wide by 2.0 to 6.0 µm long. A few become fairly large; some spirochetes occasionally reach 500 µm in length, and the cyanobacterium Oscillatoria is about 7 µm in diameter (the same diameter as a red blood cell). Recently a huge bacterium has been discovered in the intestine of the brown surgeonfish, Acanthurus nigrofuscus. Epulopiscium fishelsoni grows as large as 600 µm by 80 µm, a little smaller than a printed hyphen. It is now clear that a few bacterium are much larger than the average eukaryotic cell.

Q: Do you ever apply the peelable adhesive or is that only done by co-extruders or material suppliers?

A: DuPont sells uncoated Tyvek to medical packaging authorized converters worldwide that add value to the product by applying adhesive coatings and other converting operations (i.e., pouches, bags, die-cut lids, printing, etc).

Q: I understand you state Tyvek is superior to medical-grade paper. How does it compare to a standard film like PET/LDPE?

A: Films are not generally considered to be breathable materials. The mechanical properties of films can be modified depending on the types and layers of resins used. In some cases, Tyvek is mechanically superior to films and in others it is not. When comparing breathable materials however Tyvek has superior mechanical and microbial barrier properties over typical medical-grade paper.

Q: Is there any solvent residue in final product?

A: The spinning solvent flashes off very quickly during production, and only trace quantities normally found in the general atmosphere may be present.

Q: Some product was exposed to water (leak in the ceiling); is the product still sterile?

A: Tyvek can maintain its water ingression resistance to some very extreme points. But when it comes to medical devices, it is important to know the exposure and duration of moisture exposure. While it is true the product may not get wet, the wet surface may provide a medium for the growth of mold or other pathogens that may not be desirable. Pathogens can also “move” in water, and a potential exists that water may provide a mechanism for the pathogens to move from the surface of the Tyvek to the interior.

Q: Is Tyvek for medical packaging run on the same line as house wrap?

A: Some of the styles of Tyvek used for non-regulated applications (i.e., house wrap, envelopes, graphics, etc.) can be produced on numerous pieces of equipment. However, the medical styles are only produced on the lines qualified to run medical styles.

Q: What is the difference between the new version of Tyvek and the current? Still flashspun and bonded using heat and pressure?

A: The “new” version of Tyvek will be produced using DuPont’s latest flash spinning technology and the bonding operation remains the same. To view the latest information on the DuPont Tyvek Transition Protocol project, visit www.medicalpackaging.dupont.com and sign up to receive updated information as it becomes available.

Q: What are the best type of labels to use on Tyvek that will not peel off easily?

A: It is best to consult your label supplier for the application best suited for your medical device. Please note that if you are placing a label on the Tyvek, you will decrease the surface area of breathable material. This may or may not affect you sterilization cycle times.

Q: What is the typical deviation in thickness?

A: Because of the flash spinning process, Tyvek will inherently have variations in thickness. The typical thickness is dependant on the style produced. Please consult the DuPont Technical Reference Guide on our Web site for the specific value for each Tyvek grade.

Q: Does Tyvek absorb liquid?

A: Tyvek is hydrophobic and does not readily absorb liquid as demonstrated by Hydrostatic Head data. However, over time liquid may migrate through the fibers of the material. The microbial barrier of porous packaging material is a measurement of the substrates ability to hold out microbes present in an airstream.

Q: Could you microwave food in a Tyvek pouch and safely consume it?

A: Particular Tyvek styles are used in several room temperature food contact applications. Elevated temperature food contact applications need to be evaluated on a case by case basis.

Q: Is Tyvek sealable (with heat and pressure) to a LDPE film—a destruct bond?

A: Tyvek is HDPE. Creating a seal interface of HDPE to LDPE at high enough heat and pressure will produce a “non-peelable” seal.

Q: What is the best Tyvek grade for enhanced print quality?

A: Asuron and 2FS have titanium dioxide (TiO₂) to improve the “whiteness” of the Tyvek. This improves the perceived print quality. In most cases, in the medical device market, all of our grades of Tyvek have been found to be of adequate print quality.

Q: What is the difference between 1073B and 2FS?

A: All Tyvek is made from HDPE polymer. The main difference between 1073B and 2FS is basis weight. Tyvek 1073B has a basis weight of 2.2 oz/yd² and Tyvek 2FS has a basis weight of 1.76 oz/yd². Tyvek 2FS also has a small amount of titanium dioxide added to the sheet to give it a whiter appearance.

Q: Would pinholes in the Tyvek compromise sterility of the contents?

A: Holes are considered a breach of sterile barrier.

Q: Are there any special considerations to make to avoid fiber tear when using uncoated Tyvek with peelable films?

A: Fiber tear can generally be attributed to one or more of the following:

  • Oversealing materials, which creates a stronger bond between the seal interface than the internal bond strength of the Tyvek.
  • Not leaving a “skirt” or unsealed area around the perimeter of the package.
  • Imperfections in the edge cut which create a tear initiation point.
  • Eliminating these failure mechanisms can greatly improve the peel open performance of a package.

Q: You mentioned Tyvek 1073B and 1059B are affected by the Transition Protocol project. Why isn’t 2FS part of the transition protocol?

A: Tyvek 2FS has already been qualified on the same lines that 1059 and 1073 will be transitioning to.

Q: Is zone coating better or worse than total coverage? Does it make a difference?

A: Zone coating is typically used when there is a need to keep the coating only in the seal area of the tray. Some common reasons for wanting to use a zone coated product include, needing the breathability of uncoated Tyvek, but the performance of coated Tyvek or not wanting the coating to come in contact with the medical device.

Q: Should the top plate on a tray sealer be flat or custom to the flange shape?

A: Most heat-seal-coated Tyvek tray lid adhesives can be validated to initiate in a few seconds and at temperatures the Tyvek materials can tolerate for overall flat top plates. In order to minimize heat exposure to any lid material or for long dwell times, a custom matched tool top plate can be used.

Q: Is there an expiration for sterile products packaged with Tyvek material?

A: Long-term shelf-life study proved conclusively that Tyvek can maintain sterility for at least five years if package integrity is not compromised.

Q: Does DuPont offer any information on bonding or peel strength for Tyvek on blister trays?

A: Tyvek sealed to a rigid blister tray typically requires a heat seal coating. The manufacturer of the heat seal coating may be able to provide sealing curves or information related to the recommended time, temperature, and pressure required to active the coating.

Q: What standards are typically followed when determining accelerated shelf life conditions?

A: The standard that is used is ASTM F1980-07(2011) Standard Guide for Accelerated Aging of Sterile Barrier Systems for Medical Devices, which is based on the Arrhenius equation and known as Q10. The concept is that the rate of a reaction doubles for every ten-degree Celsius increase in temperature.

Q: When will the 11607 update come out?

A: In early 2013.

Q: Is visual inspection accepted by the medical industry?

A: Visual inspection, using a standard such as ASTM F1886:1988, is considered an acceptable form of package integrity testing. However, the precision and bias of a visual inspection is less accurate than other forms of package integrity testing.

Q: For rigid blisters, what is the minimum width of seal flange? Does it change with size of blister?

A: There is not a minimum requirement for seal width. The package and seal must be designed to provide adequate protection for the product. However, a typical seal width for a rigid tray is ¼–½ in.

Q: For PE trays sealed with Tyvek, is there a burst test able to detect unsealed areas of the trays?

A: Burst tests measure overall seal strength of the package and will not detect unsealed areas or channels in the seals. Unsealed areas or channels are detected by package integrity tests.

Q: Do you have any design suggestions that would reduce the likelihood of the pouch integrity being compromised when covering a rigid tray?

A: Try to size the pouch to fit the tray without extensive overhang in length and width that would require folding. Typically, folding the pouch over the edges of the tray can cause “tents” or “peaks” in the pouch material and can lead to abrasion points, tears, and holes.

Q: Can you explain the pros and cons of tab or tack seals on peel pouches?

A: Pros: Tack seals are part of the pouch manufacturing process. Pouches are manufactured in lanes, therefore the tack seal on one pouch is often the end of the rail seal from the previous pouch. The only way to avoid having a tack seal is to have a gap at the end of the rail seal on the pouch. Tack seals also provide a benefit of keeping the unsealed area between the chevron and end of the pouch together, which can be a benefit for materials with a propensity to curl. It’s best to discuss preferences and/or concerns about tack seals with the pouch manufacturer and get their recommendation on the best way to manufacture the pouch.
Cons: It takes an extra second to break the tack seal prior to opening the pouch in a healthcare setting, such as an operating room. 

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