Oxygen Permeability of Films: How It Is Measured and Why It Matters

Oxygen permeability is an important property when evaluating films and packaging materials designed to control gas transmission. It describes how readily oxygen can move through a material under defined conditions and helps characterize its barrier performance.

Understanding oxygen permeability can support material selection, packaging development and quality control. It is particularly relevant when comparing polymers, coated films, laminates and multilayer structures intended for applications where oxygen transmission needs to be controlled.

Oxygen permeability and oxygen transmission rate (OTR) are closely related, but they are not the same parameter. Understanding the difference is essential when interpreting test results and comparing materials.

What Is Oxygen Permeability?

Oxygen permeability describes the ability of oxygen to pass through a material in response to a driving force, typically a difference in oxygen partial pressure across the film.

It is a material-related property that depends on the characteristics of the material and the conditions under which permeability is evaluated. In polymer films, oxygen transport is influenced by how oxygen interacts with the polymer and moves through its structure.

Materials with lower oxygen permeability generally provide a stronger oxygen barrier under comparable conditions. However, the barrier performance of a finished film also depends on its thickness, structure and the conditions of use.

Oxygen permeability should therefore be interpreted using the relevant measurement method, units and test conditions.

Oxygen Permeability vs. Oxygen Transmission Rate (OTR)

Oxygen permeability and oxygen transmission rate provide related but different information about a film’s oxygen barrier performance.

Oxygen Permeability

Oxygen permeability is a material property that describes oxygen transport through a material. Depending on the method and calculation convention, the permeability coefficient accounts for the driving force for transport and material thickness.

Oxygen Transmission Rate (OTR)

OTR describes the amount of oxygen passing through a specified area of material over a given period under defined test conditions. It is commonly used to characterize and compare the oxygen barrier performance of films and packaging materials.

OTR is influenced by the material, film thickness, temperature, pressure conditions and other factors relevant to the selected test method.

Why the Difference Matters

Permeability coefficients and OTR values cannot automatically be compared as if they were the same measurement. They may use different units and represent different quantities.

When comparing results, check:

• Whether the reported value is oxygen permeability or OTR.
• The units and calculation method.
• The thickness of the tested material.
• The temperature and other relevant test conditions.
• Whether the measurements were obtained using comparable methods.

For a detailed explanation of OTR, read OTR: What Oxygen Transmission Rate Is and How It Is Measured.

Why Is Oxygen Permeability Important?

Oxygen can affect product quality in applications where oxidation or oxygen exposure needs to be controlled. Evaluating the oxygen barrier properties of packaging films helps manufacturers and material developers make informed decisions about material selection and packaging design.

Packaging Material Selection

Different polymers, coatings and multilayer structures can exhibit different oxygen barrier properties. Testing helps compare candidate materials under defined conditions and identify options for further evaluation.

Product Protection

For oxygen-sensitive products, understanding oxygen transmission can contribute to packaging development aimed at limiting oxygen exposure. The appropriate barrier requirement depends on the product, package design and intended storage conditions.

Packaging Development

Oxygen permeability measurements can support the evaluation of new materials, coatings and film structures. They can also help assess whether a material change affects barrier performance.

Quality Control

Consistent testing can help laboratories compare samples, monitor material characteristics and investigate differences between batches or suppliers.

The required oxygen barrier performance depends on the specific application. A permeability result alone does not determine product shelf life or guarantee packaging performance in actual use.

Which Factors Affect Oxygen Permeability in Films?

Oxygen transport through a film depends on the material and the conditions under which it is tested.

Polymer Type and Material Structure

Different polymers have different chemical and physical characteristics that influence oxygen transport. Material composition and structure therefore play an important role in barrier performance.

Film Thickness

Thickness affects the distance oxygen travels through a film and can influence the measured transmission rate. Permeability and OTR should not be treated as interchangeable when accounting for thickness.

Temperature

Temperature can affect oxygen transport through a material. Results obtained at different temperatures may not be directly comparable, so the test temperature should be recorded and considered during interpretation.

Relative Humidity

Relative humidity can affect the barrier properties of some materials. Its relevance depends on the film composition and the test method. Where applicable, humidity conditions should be controlled and documented.

Coatings, Laminates and Multilayer Structures

Coatings and multilayer constructions can alter the overall barrier performance of a film. The result depends on the properties of the individual layers and the integrity of the complete structure.

Testing the finished film helps characterize the material as it will be evaluated for the intended application.

Sample Preparation and Test Conditions

Sample damage, folds, contamination or inadequate mounting can affect measurement reliability. Consistent sample preparation and controlled test conditions help support meaningful comparisons.

How Is Oxygen Permeability Measured?

Oxygen permeability is evaluated through a test that measures oxygen transmission across a material under defined conditions. The exact procedure and calculation depend on the measurement method and the parameter being reported.

In a typical film transmission test, the sample is mounted between two chambers. One side is exposed to oxygen or a gas mixture containing oxygen, while the other side is used to detect or measure the oxygen that passes through the material.

The instrument records the transmission behavior. Depending on the method, the result may be reported as an oxygen transmission rate or used in a calculation to determine a permeability coefficient.

The test setup and calculation should be appropriate for the material, expected transmission values and intended measurement.

Preparing the Film Sample

The sample should be representative of the material being evaluated and prepared according to the selected method. Its thickness, structure and condition should be documented where relevant.

Careful mounting is important because wrinkles, leaks or damaged areas may affect the result. The sample preparation procedure should be consistent when comparing materials.

Defining Test Conditions

Temperature, gas conditions, pressure difference and other method-specific parameters can influence the measurement. Relative humidity should also be considered where relevant to the material and test procedure.

Results should be reported with sufficient information about the test conditions to support interpretation and comparison.

Recording and Interpreting Results

The reported parameter and its units must be identified clearly. An OTR value describes transmission under the stated conditions, while a permeability coefficient represents a different quantity calculated according to the applicable method.

When comparing film materials, use consistent conditions and confirm that the measured parameter, units and calculation conventions are compatible.

Which Films Can Be Evaluated?

Oxygen barrier testing can be relevant to a range of film materials and packaging structures, depending on the instrument configuration and selected method.

Examples include:

• Single-layer plastic films.
• Coated films.
• Metallized films.
• Multilayer films and laminates.
• Other barrier materials suitable for the selected test configuration.

The suitability of a specific sample must be confirmed against the instrument’s capabilities, the applicable method and the sample requirements.

For more information, read Permeability Testing of Plastic Films and Permeability Testing of Multilayer Films and Laminates.

Oxygen Barrier Testing in Packaging Applications

Oxygen barrier evaluation is used in packaging development when controlling oxygen transmission is important.

Food Packaging

Oxygen transmission measurements can help characterize packaging materials selected for products sensitive to oxygen exposure. The required barrier performance depends on the product and packaging system.

Explore Permeability Testing for Food Packaging.

Flexible Packaging

Flexible packaging may use coated, laminated or multilayer films to achieve a combination of barrier and functional properties. Oxygen transmission testing can help compare these structures under defined conditions.

Explore Permeability Testing of Flexible Packaging.

Pharmaceutical Packaging

Depending on the product and packaging system, oxygen barrier properties may be one of several material characteristics that need to be evaluated.

Permeability testing provides material performance data, but it does not by itself establish product safety or regulatory compliance.

Explore Barrier Testing for Pharmaceutical Packaging.

Choosing an Oxygen Permeability Testing System

Selecting a suitable instrument starts with identifying the parameter to be measured and the characteristics of the sample.

Important considerations include:

• Measurement objective: determine whether the required result is OTR, an oxygen permeability coefficient or another specified parameter.
• Material characteristics: consider the film composition, thickness, coatings and layer structure.
• Expected transmission values: confirm that the measurement system is suitable for the expected range.
• Test conditions: identify the required temperature and other relevant conditions.
• Sample configuration: confirm compatibility with the intended film sample and test method.
• Reporting requirements: establish the required units and information for comparing results.

If more than one barrier property needs to be measured, a system designed to evaluate multiple transmission parameters may be useful.

ExtraSolution Instruments for Oxygen Transmission Testing

ExtraSolution offers instruments for evaluating oxygen transmission through films and barrier materials. The appropriate system depends on the parameters required and the intended test configuration.

MultiPerm O2-CO2

Designed for oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO₂TR) measurements.

Explore MultiPerm O2-CO2.

MultiPerm O2-H2O

Designed for oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) measurements.

Explore MultiPerm O2-H2O.

TotalPerm

Combines OTR, CO₂TR and WVTR measurement capabilities in one integrated system.

Explore TotalPerm.

To identify a suitable solution, confirm the required parameters, sample characteristics and measurement conditions with ExtraSolution.

Conclusion

Oxygen permeability is an important material property for evaluating films designed to control oxygen transmission. Its relationship with OTR should be understood when interpreting results: permeability and transmission rate describe different quantities and cannot be compared directly without considering their definitions, units and test conditions.

By selecting an appropriate measurement method and controlling relevant test conditions, laboratories can characterize oxygen barrier performance, compare film materials and support packaging development and quality control.

ExtraSolution provides solutions for measuring oxygen transmission through films and barrier materials.

Contact ExtraSolution to discuss your oxygen barrier testing requirements and identify a suitable measurement system.