CO₂ Permeability and CO₂TR: Measurement and Analysis

Carbon dioxide permeability is an important property when characterizing films, packaging materials and multilayer structures. Measuring CO₂ transmission helps determine how a material behaves when exposed to carbon dioxide under defined test conditions.

The Carbon Dioxide Transmission Rate (CO₂TR) is a key parameter used to characterize the rate at which carbon dioxide passes through a material. This measurement provides quantitative data for material comparison, development and quality control.

ExtraSolution offers solutions for measuring CO₂ transmission and characterizing the barrier properties of films and other materials.

What Is CO₂ Permeability?

CO₂ permeability describes the ability of carbon dioxide to pass through a material. It is relevant when evaluating materials designed to control the transmission of this gas.

The measured behavior depends on several factors, including material composition, thickness, structure, temperature and the conditions used for the test.

In packaging applications, measuring CO₂ transmission can help characterize materials and compare their performance against specific requirements.

What Is CO₂TR?

CO₂TR stands for Carbon Dioxide Transmission Rate. It describes the rate at which carbon dioxide passes through a material under specified test conditions.

CO₂TR is used to characterize plastic films, barrier films, laminates and multilayer materials when carbon dioxide transmission is an important property.

In general, a lower CO₂TR indicates lower carbon dioxide transmission under the conditions used for the test. Results should be compared only when the test conditions and reporting units are consistent.

Why Measure CO₂TR?

CO₂TR measurement provides quantitative information about the carbon dioxide transmission characteristics of a material.

This information can be used to:

  • compare different films and barrier materials;
  • characterize materials intended for specific packaging applications;
  • support the development of new materials;
  • evaluate multilayer structures and laminates;
  • assess the effects of changes in composition or thickness;
  • qualify materials and suppliers;
  • support quality control and material verification.

CO₂TR testing can therefore contribute to research and development, material qualification and production quality control.

How Is CO₂ Permeability Measured?

CO₂ transmission is measured using a suitable permeability testing system that exposes a sample to defined conditions and detects the carbon dioxide passing through it.

Depending on the measurement method, the sample separates two environments, and the instrument monitors the gas transmitted through the material over time.

The measurement system determines the CO₂TR according to the selected method and the conditions established for the test.

Reliable results require appropriate sample preparation and control of relevant parameters, such as temperature and, where applicable, relative humidity.

The exact procedure depends on the instrument, the material and the applicable testing standard.

For an overview of permeability measurement principles, see Gas Permeability: Measurement and Analysis.

Which Materials Can Be Tested Using CO₂TR?

CO₂TR testing can be used to characterize a range of materials in which carbon dioxide transmission is relevant.

Examples include:

  • plastic films;
  • barrier films;
  • multilayer films;
  • laminated materials;
  • metallized films;
  • co-extruded structures;
  • other suitable materials used in packaging and technical applications.

The choice of measurement configuration depends on the sample characteristics, the expected transmission rate and the required test conditions.

CO₂TR and the Barrier Properties of Materials

CO₂TR is one of the parameters that can be used to characterize the barrier properties of a material.

However, carbon dioxide transmission is distinct from oxygen and water vapor transmission. A material may exhibit different barrier performance depending on the substance being measured.

For this reason, the choice of test should reflect the specific requirements of the intended application.

For a broader overview, see Barrier Properties of Films: Measurement and Characteristics.

CO₂ Permeability in Barrier Films

Barrier films are designed to limit the transmission of specific substances through their structure. Their performance depends on the materials used, their thickness and the arrangement of the different layers.

CO₂TR measurement can help evaluate the carbon dioxide transmission characteristics of films, laminates and multilayer structures.

Testing the complete structure makes it possible to compare alternative material combinations and assess the effect of changes to the film design.

Factors That Influence CO₂TR

The measured CO₂TR can be affected by several factors, including:

  • Material composition: different materials can exhibit different carbon dioxide transmission characteristics.
  • Thickness: thickness can influence the measured transmission rate.
  • Film structure: multilayer films and laminates may behave differently depending on the combination and arrangement of their layers.
  • Temperature: temperature can influence gas transmission through a material.
  • Relative humidity: humidity may affect the behavior of certain materials and should be controlled where relevant.
  • Test conditions: the measurement method and test parameters must be considered when interpreting results.

For reliable comparisons, measurements should be performed under consistent and clearly documented conditions.

CO₂TR in Packaging Applications

CO₂TR measurement is relevant to packaging applications in which carbon dioxide transmission needs to be characterized.

Testing can support material selection, packaging development and quality control by providing quantitative information about the behavior of films and other suitable packaging materials.

The appropriate test depends on the material, the intended application and the required barrier performance.

CO₂TR and OTR: What Is the Difference?

CO₂TR and OTR are both transmission rate parameters, but they characterize different gases.

  • CO₂TR (Carbon Dioxide Transmission Rate) measures carbon dioxide transmission through a material.
  • OTR (Oxygen Transmission Rate) measures oxygen transmission through a material.

The two parameters are not interchangeable. A material’s performance with respect to oxygen cannot automatically be used to predict its performance with respect to carbon dioxide.

Depending on the application, both parameters may need to be measured to obtain a more complete understanding of a material’s barrier properties.

For more information, see Oxygen Permeability and OTR: Measurement and Analysis.

Standards and Test Conditions for CO₂TR Measurement

CO₂TR measurements should be performed using an appropriate test method and under defined conditions.

The applicable procedure depends on the material, the measurement technique and the requirements of the test. Temperature, humidity, sample preparation and reporting units should be considered when interpreting results or comparing materials.

Where a specific standard is required, the test procedure and instrument configuration should be selected accordingly.

How to Choose a CO₂TR Tester or Analyzer

Selecting a CO₂TR analyzer starts with identifying the material to be tested and the measurement requirements.

Important factors include:

  • sample type and dimensions;
  • expected CO₂TR range;
  • required temperature and humidity conditions;
  • number of samples to be tested;
  • applicable test methods and standards;
  • whether oxygen or water vapor transmission must also be measured.

The most suitable configuration depends on the laboratory’s testing objectives and the characteristics of the materials being analyzed.

ExtraSolution Instruments for CO₂TR Measurement

ExtraSolution offers solutions for characterizing carbon dioxide transmission through films and barrier materials.

Depending on the required measurements, available systems include:

  • MultiPerm O2-CO2 — for oxygen and carbon dioxide transmission measurements;
  • MultiPerm H2O-CO2 — for water vapor and carbon dioxide transmission measurements;
  • TotalPerm — for characterizing oxygen, carbon dioxide and water vapor transmission using an integrated system.

The appropriate instrument depends on the required measurement parameters, sample characteristics and test conditions.

Applications of CO₂TR Measurement

CO₂TR testing can support a range of activities, including:

  • research and development of new materials;
  • characterization of plastic and barrier films;
  • evaluation of multilayer films and laminates;
  • packaging material qualification;
  • comparison of alternative material structures;
  • quality control and verification of material performance.

Measure CO₂TR with ExtraSolution

ExtraSolution provides solutions for measuring carbon dioxide transmission and characterizing the barrier properties of films and other materials.

Contact ExtraSolution to identify the most suitable configuration for your materials, measurement range and test requirements.

Explore Related Topics