Barrier Films: Properties, Materials and Measurement Methods

Barrier films are materials designed to control the transmission of gases and vapor through a packaging structure. They are used in applications where oxygen, moisture or carbon dioxide transmission needs to be limited or characterized.

Their performance depends on the materials used, the film structure, the intended application and the conditions under which barrier properties are measured.

Understanding barrier film materials and testing methods helps manufacturers, packaging developers and laboratories compare material options, evaluate film structures and support product development and quality control.

What Are Barrier Films?

Barrier films are films selected or engineered to provide resistance to the transmission of one or more substances.

Depending on their composition and structure, they may be designed to limit oxygen transmission, water vapor transmission or the passage of other gases. Some films consist of a single material, while others combine several layers to achieve a desired balance of barrier and other functional properties.

Barrier films can be used in flexible packaging, food packaging, pharmaceutical packaging and other applications where material transmission is an important consideration.

The term barrier film does not describe a single material or a universal level of performance. The relevant barrier properties must be evaluated for the specific material and application.

Which Materials Are Used in Barrier Films?

Barrier performance depends on the characteristics of the individual materials and how they are combined in the finished film.

Polymer Films

Plastic films are widely used in packaging because they can provide a combination of flexibility, processability and functional properties. Different polymers exhibit different gas and vapor transmission characteristics.

The suitability of a polymer depends on the required barrier properties, the packaging design and the conditions under which the material will be used.

Coated Films

Coatings can be applied to a film to modify its surface properties or barrier performance. The resulting characteristics depend on the coating material, its application and the quality of the finished structure.

Testing can help evaluate the performance of the coated film as a complete material.

Metallized Films

Metallized films incorporate a thin metallic layer and are used in applications where specific barrier and packaging properties are required.

Their performance depends on the film substrate, the metallized layer and the integrity of the finished structure.

Laminates and Multilayer Films

Laminates and multilayer films combine different materials to achieve a set of functional properties. These may include barrier performance, mechanical strength, sealability and suitability for a particular packaging process.

The overall barrier behavior depends on the materials, layer thicknesses, interfaces and manufacturing characteristics.

Learn more in [Permeability Testing of Multilayer Films and Laminates].

Which Barrier Properties Matter Most?

The relevant barrier properties depend on the product being packaged and the substances that need to be controlled.

Oxygen Transmission Rate (OTR)

OTR measures the rate at which oxygen passes through a material under specified test conditions. It is commonly used to characterize the oxygen barrier performance of films and packaging materials.

OTR testing helps compare materials intended to limit oxygen transmission and supports the evaluation of alternative film structures.

Learn more in Oxygen Permeability and OTR: Measurement and Analysis.

Water Vapor Transmission Rate (WVTR)

WVTR measures the rate at which water vapor passes through a material under specified conditions. It is relevant when evaluating moisture barrier performance.

WVTR measurements can help compare films intended to limit moisture transfer. Temperature and relative humidity conditions should be considered when interpreting the results.

Learn more in Water Vapor Permeability and WVTR: Measurement and Analysis.

Carbon Dioxide Transmission Rate (CO₂TR)

CO₂TR measures the rate at which carbon dioxide passes through a material under specified test conditions.

It can be useful when carbon dioxide exchange is relevant to the intended application. The results depend on the material, test method and measurement conditions.

Learn more in CO₂ Permeability and CO₂TR: Measurement and Analysis.

These parameters provide different information about material performance. A film’s oxygen barrier properties should not be assumed to predict its water vapor or carbon dioxide transmission behavior.

How Are Barrier Films Evaluated?

Barrier films are evaluated by measuring the transmission of a selected gas or vapor through a sample under defined conditions.

The appropriate test method depends on the material, the parameter being measured and the expected transmission values.

In many film testing systems, the sample is mounted between two chambers. One side is exposed to the gas or vapor of interest, while the other side is used to detect or measure the substance passing through the film.

The measurement system records the transmission behavior and determines the relevant parameter according to the selected method.

A useful evaluation should consider:

• The transmission parameter being measured.
• The material composition and film thickness.
• The sample structure, including any coatings or layers.
• Temperature and, where relevant, relative humidity.
• The gas or vapor conditions specified by the method.
• The instrument’s suitability for the expected transmission values.
• The units and reporting conventions used for the result.

The specific apparatus, procedure and calculation method depend on the instrument and test method. Results should be interpreted in the context of the conditions under which they were obtained.

What Is the Difference Between Permeability and Transmission Rate?

Permeability and transmission rate are related, but they describe different quantities.

Permeability describes a material property associated with the transport of a substance through the material. A permeability coefficient generally accounts for the driving force for transport and material thickness, according to the calculation method used.

Transmission rate describes how much of a substance passes through a specified area of material over a given period under defined conditions.

OTR, WVTR and CO₂TR are transmission parameters used to characterize the passage of oxygen, water vapor and carbon dioxide, respectively.

When comparing results, check the reported parameter, units, material thickness, test conditions and calculation method. Values expressed using different quantities or conditions may not be directly comparable.

Which Factors Influence Barrier Film Performance?

Different polymers and barrier materials interact with gases and vapor in different ways. Their chemical structure and physical properties influence transmission behavior.

Film Thickness

Thickness affects the distance a substance must travel through the material. However, thickness alone does not determine barrier performance, and comparisons should be made under consistent conditions.

Layer Structure

In a multilayer film, the overall barrier performance depends on the properties of the individual layers and the way they are combined.

Testing the complete structure helps characterize the actual material used in the application rather than relying only on data for an individual layer.

Temperature and Relative Humidity

Temperature can influence transmission behavior, while relative humidity can be particularly important for materials sensitive to moisture.

These conditions should be defined and documented to support meaningful comparisons.

Sample Preparation and Integrity

Folds, damage, contamination or inadequate mounting can affect test results. Proper preparation helps ensure that the measurement represents the intended material.

Manufacturing Characteristics

Variations in coating application, layer distribution or other manufacturing factors can influence the performance of the finished film. Consistent testing can help identify differences between samples.

Barrier Films in Packaging Applications

Barrier films are used across a range of packaging applications. The required properties depend on the product, packaging design and intended conditions of use.

Food Packaging

Food packaging may require control of oxygen or moisture transmission to help protect product quality. The relevant barrier parameters depend on the characteristics of the product and the packaging requirements.

Explore [Permeability Testing for Food Packaging].

Plastic Film Packaging

Plastic films are used in a wide range of packaging structures. Testing helps characterize their barrier properties and compare alternative materials under defined conditions.

Explore [Permeability Testing of Plastic Films].

Flexible Packaging

Flexible packaging may combine films, coatings, laminates and multilayer structures. Barrier testing can help evaluate the selected structure and support material development.

Explore [Permeability Testing of Flexible Packaging].

Pharmaceutical Packaging

Pharmaceutical packaging materials may require evaluation of their gas and moisture barrier properties, depending on the product and packaging system.

Permeability measurements can contribute to material characterization, but they do not by themselves establish product safety or regulatory compliance.

How to Choose a Barrier Film Testing Method

The appropriate test method depends on the measurement objective and the characteristics of the material.

Before selecting a method or instrument, consider:

• The property to evaluate: OTR, WVTR, CO₂TR or more than one parameter.
• The material: polymer type, thickness, coatings and layer structure.
• The expected transmission values: confirm that the method and instrument are suitable for the measurement range.
• Environmental conditions: determine the required temperature and relative humidity.
• Sample preparation: follow the requirements of the selected method.
• Reporting requirements: define the units and information needed to compare results.
• Laboratory workflow: consider sample throughput and data handling.

For laboratories that need to evaluate multiple barrier properties, a system capable of measuring more than one transmission parameter may help consolidate testing activities.

The final choice should be based on the intended application, the test method and confirmed instrument compatibility.

ExtraSolution Instruments for Barrier Film Testing

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.

MultiPerm H2O-CO2

Designed for water vapor transmission rate (WVTR) and carbon dioxide transmission rate (CO₂TR) measurements.

Explore MultiPerm H2O-CO2.

TotalPerm

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

Explore TotalPerm.

PermeH2O

Provides a dedicated solution for water vapor transmiss<ion rate (WVTR) measurement.

Explore PermeH2O.

The appropriate instrument depends on the material, the required measurement parameters, the expected transmission values and the test configuration. Contact ExtraSolution to discuss your application and identify a suitable testing solution.

Conclusion

Barrier films are designed to control the transmission of gases or vapor, but their performance depends on the material, structure and intended application.

OTR, WVTR and CO₂TR measurements provide complementary information about oxygen, water vapor and carbon dioxide transmission. Selecting the appropriate test method and controlling relevant conditions help laboratories compare materials and support packaging development and quality control.

ExtraSolution provides solutions for measuring oxygen, carbon dioxide and water vapor transmission through films and barrier materials.

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