Blister packaging · Industry glossary
Oxygen transmission rate (OTR)
The volume of oxygen transmitted through a unit area of material per unit time under specified conditions.
Also called: oxygen barrier transmission.
What does cc/(m²·day) mean?
It describes oxygen volume transmitted through a unit area per unit time at the stated measurement conditions. A cubic centimetre is written as cm³ or cc; identify the gas-volume reference basis used in the report as well as its area and time units.
Film OTR may be reported in cm³/(m²·day), while a whole-package result may use cm³/(package·day). Define whether the package specimen is a complete blister card, an individual cavity or another format before comparing the numbers.
Can oxygen and air test results be compared without adjustment?
Not as an unexplained pair of numbers. The oxygen conditions across the specimen provide a driving difference. In a test using oxygen or air on one side and nitrogen on the other, changing the test gas changes that boundary condition.
Also retain temperature, humidity, method and material construction. Do not silently scale a result from oxygen to air, from dry to humid conditions or from one laminate to another. A shared unit label does not make those test situations identical.
| Question | Why it changes interpretation |
|---|---|
| Which gas and pressure conditions? | They define the oxygen-driving conditions across the specimen. |
| Which temperature and humidity? | They describe the test environment, not optional footnotes. |
| Which specimen and normalisation? | Film area and complete-package results are different bases. |
| Which volume reference basis? | The reported gas volume needs a stated convention. |
OTR, headspace oxygen and leak integrity
No. Headspace oxygen is a concentration in the gas already inside a pack; OTR is a transfer rate under defined conditions. A low oxygen concentration at one moment is not itself an OTR measurement.
WVTR concerns water-vapour mass rather than oxygen volume, so the two rates cannot be combined into one interchangeable barrier score. A film’s OTR also does not show that a finished blister has no leak path. Each result needs the question, specimen and conditions it actually represents.
IN THE PRODUCTION LINE
Define requirements
Terminology checked .