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Q2 Permeation Products & Services Newsletter

Thursday, June 20, 2024


 
 

Quarter 2 | June 2024

 
 

Equilibrium? Not So Fast: Understanding Permeation Testing Times

When it comes to transmission rate testing, people often wonder how long it will take. The answer? Well, that depends. If you are looking for equilibrium values (i.e., values that are constant and unchanging), some tests are quick, while others can take weeks.

Below is a graph showing:

  • A low-barrier film (reaches equilibrium in hours)
  • A high-barrier film (needs more than a week)
  • A complex-barrier film (needs more than a week)

 

If comparing testing materials – i.e., “Is one film much higher in WVTR than another?” – or in a QC setting where established parameters are utilized (such as needing a transmission rate level <0.25 cc/ (m2 x day)), you can stop as soon as you obtain the necessary information.

General time-testing guidelines include:

  • The thicker the material, the longer it takes to reach equilibrium. If you double a sample’s thickness, the TR drops by half, but the time to equilibrium increases by 4X.

  • Higher test temperatures lead to higher diffusion coefficients (e.g., the oxygen molecule wiggles through the sample at a faster pace). The result is a higher overall transmission rate AND a faster test. Note: A common strategy for analyzing a known long-duration barrier film is to first equilibrate the sample at a higher temperature to set the test gas gradient within the polymer and then drop the analysis temperature for the final transmission rate result.

  • Complex barriers often have an inner heat-sealable food/product contact layer that has pre-absorbed O2 and H2O from ambient air exposure. This inner layer can show initial outgassing, followed by an uptake of the test gas through the film. Note: Take care not to call the low-level “saddle point” of a complex barrier curve the equilibrated value.

After Temperature and Humidity, the biggest element of testing is when to call a test complete. For equilibrium determination, some laboratories establish a steady value over 4-6 hours. In our Minneapolis Permeation Laboratory, the criterion for equilibrium is a steady value over 24 hours with a standard maximum test duration of five days. Ultimately, however, it is difficult to estimate how long a permeation test will take unless the material has been previously characterized.
 

Faster, Easier and More Accurate: The Future of Testing Cups and Capsules

Cups are used in various sectors from coffee capsules to microwaveable soups. Permeation testing of cups from the food and beverage industries comprise a sizeable percentage of total packaging. Traditional permeation testing of these materials consists of using epoxy to glue the sample to a metal plate and purging the inside with nitrogen gas to direct any permeated molecules through the detector.

However, using epoxy can be messy, time-consuming and subjective. A QC testing environment requires optimal test throughput to maximize efficiency. As a result, you need a faster, easier and more repeatable method for prepping these materials.

 

The new custom cup cartridge design allows technicians to secure a test cup by a compressive force for any cup diameter within approximately 3.5” (you can design a test for larger specialized cups as well). Since injection molded cups have flanges, the cartridge top plate with a protruding lip that has the same diameter as the cup compresses the flange area when being secured to the base (figure 2). Multiple-sized cups only need a custom top plate to match the flange diameter while utilizing the same cartridge base (figure 3). This easily facilitates testing of various cup sizes using the same cartridge base (i.e., 80 cm2 cartridge base).

This method is nondestructive and provides more accurate results than using epoxy, since the epoxy covers some of the cup area (producing a slightly lower, false transmission rate).

To learn more about MOCON custom cartridges and their benefits, read the full product brochure below:

Read More


Time is Money: Accurate Pharmaceutical Packaging Development with Instrumental Barrier Testing

Pharmaceutical packaging typically uses blister packaging, which normally features high-barrier materials that hold a single dose (such as a tablet). They consist of a thermal-formed cavity that holds the tablet and a flat lid that seals the product in place.

As such, the industry needs to understand the oxygen and water vapor barrier characteristics of these cavities to ensure the efficacy of the drug product. Permeation of gasses occurs in three areas: the molded cavity, the flat lidding, and the seal between the two.


Barrier testing of blister packages can take an exceptionally long time, as both the oxygen and water transmission rates are low, and it is a challenge to quantify using traditional techniques. For WVTR, this has historically been measured through gravimetric (weight gain) studies. For OTR, companies measure the chemical degradation of the product relating to oxidation. As these tests often have exceedingly long test durations - weeks or months, even in accelerated environments - it is often easier and faster to measure OTR and WVTR with high-sensitivity instrumental methods.

With these instrumental results, a pharmaceutical company can screen and select material candidates and suppliers more efficiently. For a smaller group of packaging candidates, this translates to time and cost savings when conducting necessary stability studies.

Testing includes:

  • Films for Lidding – These are readily analyzed with standard film transmission rate testing.
  • Formed Blister – These can be analyzed independently (such as verifying mold cavity design) via sealing the cavity to a foil film that has a hole and measuring the transmission rate through the mounted sample
  • Blister “System” – Measures the transmission rate through the cavity, film and includes the seal. For many systems, the seal is a critical component. This Blister “System” is best analyzed for WVTR if liquid is secured inside the cavity with factory seals. If this cannot be done, you can inject water into the cavity and seal the injection site with epoxy. One key item with sealed blister systems is that if the overall transmission rate is low, adding multiple filled blisters to the test cell will generate more water vapor signal and allow for better low-level testing.

 

Resources

Revised or new application notes (click images below).

Curious for more? Uncover a wealth of knowledge on similar topics and industries in our Resource Library linked below:

Resource Library
Events

We are halfway through our 2024 trade show season. We are excited to announce our second half of trade shows and conferences worldwide! Please see the schedule below to see if we are coming to a location near you:

Coming in spring 2025 is our 17th Permeation Conference! Hosted by AMETEK MOCON. Next year's conference will take place in the countryside near Höhr-Grenzhausen, Germany. To learn more about the conference, please visit the link below:
Read More

For customers located in the United States, we'll be at:
Pack Expo International 2024
  • Location: Chicago, IL
  • Days: Sunday, Nov. 3 - Wednesday, Nov. 6, 2024
  • Booth Number: W-17080
For customers located in Europe, we'll be at:
Multilayer Packaging Conference
  • Location: Vienna, Austria
  • Days: Tuesday, Dec. 10 - Wednesday, Dec. 11, 2024
  • Booth Number: (TBD)
Currently, we have no shows scheduled in Asia for the rest of 2024.

Our list of 2024 trade shows and events is now final. Check the link below to our events page to see where we will be!

Events