What Is Permeation?

Permeation is the movement of a gas or vapor through a semi-permeable barrier such as the wall of a film, whole package, medical device, or even a flexible electronic display. The gas or vapor is driven to move from an area of high concentration to an area of low concentration.

Modern packaging materials are made from a variety of materials that are semi-permeable to gases, the most popular being paper/paperboard, rigid plastic packaging like HDPE/PET, flexible plastic packaging like LDP/LLDPE, and metalized Packaging typically using aluminum foils. Since these materials are permeable, gas permeation rates through these barriers are critical to measure to determine how long a packaging system will maintain its desired gas composition and thus ultimately, how long a product will be protected and last in any given packaging. The shelf life of packaged foods, beverages and packaged consumer goods can be significantly impacted by the gas permeability of the packaging system used to protect these goods.. In the electronics manufacturing industry for solar panels and OLED devices, the permeation rate of water vapor through packaging systems directly effects the useful lifetime of the product – and is hence a critical parameter to understand for packaged electronic component life time.

Yes indeed, the permeation rate of gas through permeable barriers and packages are important in many applications!

To ensure packaged products or packaging materials will provide the desired product shelf life, protection and safety – it is critical to understand the gas permeation rates through both the barrier materials and the final finished package, and select packaging materials and designs that can meet your shelf life needs.

In practical applications, the transmission rate (TR), is the most common way to report the “flux” of gas moving through a polymer. The transmission rates for oxygen (OTR), water vapor (WVTR) and carbon dioxide CO2 (CO2TR) can be measured by permeation instruments with different sensor technologies. For packaging films, permeation rates are typically reported as: cc/m2day for OTR and CO2TR and g/ m2day for WVTR.

Effectively, these transmission rates describe how much a specific gas of interest (in cc or g), is going through a given area of barrier film, each day. For finished packages, permeation rates are typically reported as: cc/packageday for OTR and CO2TR and g/packageday for WVTR. For whole packages, this essentially measures how much of a specific gas will go through a given package in a day. Whether analyzing packages or films, permeation rates are affected by environmental conditions such as temperatures, relative humidity (RH), as well as the concentration difference between the gas inside a package versus the gas outside of the package. Therefore, testing at controlled test temperature and relative humidity are crucial for obtaining accurate transmission rate results.

What can I do with Permeation measurements?

From gas transmission rate analyses, it is possible to determine how long it will take for a bottled soda pop product to go flat (even without opening the product), the time it takes a protective atmosphere to reach ambient conditions, and ultimately, whether your packaging is providing the gas permeation protection that is desired.

Gas permeation analysis can also be used to monitor the quality of raw packaging materials as it goes from film through conversion to the final packaged product. Often, even small material changes can cause significant changes in gas permeation rates – with a large consequence to the atmosphere that a product experiences during its packaged lifetime. Gas permeation analysis for quality control in the packaging materials, converters and food & beverage industries are some of the largest uses of permeation analysis equipment today.

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