Film Barrier Properties: What They Are and How to Evaluate Them

Film barrier properties describe how effectively a material limits the transmission of gases and vapor through its structure. They are important when selecting and developing packaging materials designed to control the transfer of oxygen, water vapor, carbon dioxide and other substances.

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

However, barrier performance is not a single property. It depends on the substance being measured, the composition and structure of the film, the test conditions and the intended application.

What Are Film Barrier Properties?

Film barrier properties describe a material’s resistance to the passage of gases or vapor under defined conditions.

Some films are designed to provide a strong barrier against oxygen, while others are selected primarily for their moisture barrier performance. Multilayer structures may combine different materials to achieve a balance of barrier, mechanical and processing properties.

The barrier performance of a film depends on several factors, including:

• The chemical and physical properties of the material.
• The type of gas or vapor being measured.
• The thickness and structure of the film.
• The presence of coatings, laminates or additional layers.
• Temperature and, where relevant, relative humidity.
• The test method and measurement conditions.

A material that performs well as an oxygen barrier does not necessarily provide the same performance against water vapor or carbon dioxide. Each relevant property should therefore be evaluated using an appropriate measurement method.

Why Are Barrier Properties Important?

Barrier properties influence the suitability of films for packaging and other applications in which material transmission needs to be controlled.

Product Protection

Some products are sensitive to oxygen, moisture or changes in their surrounding atmosphere. Understanding the barrier properties of a packaging material helps manufacturers evaluate whether it is appropriate for the intended application.

Material Selection

Barrier measurements allow different materials and film structures to be compared under defined conditions. This can support decisions during material selection and packaging development.

Packaging Development

During product development, manufacturers may evaluate alternative polymers, coatings, thicknesses and multilayer structures to identify a suitable combination of properties.

Quality Control

Consistent testing can help laboratories monitor material performance, investigate variations and compare results across samples or production batches.

Process and Material Improvement

Barrier measurements can help researchers assess how changes in material composition, processing or structure affect transmission behavior.

Barrier performance is only one part of packaging evaluation. Other properties and application requirements should also be considered when selecting a material.

Which Barrier Properties Should Be Evaluated?

The relevant parameters 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 film under specified test conditions. It is commonly used to characterize oxygen barrier performance.

OTR testing can help compare materials intended to limit oxygen transmission and evaluate differences between film formulations or 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 an important parameter when evaluating moisture barrier performance.

WVTR testing can help compare films intended to limit moisture transfer. Temperature and relative humidity conditions should be considered when interpreting and comparing 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 is relevant when carbon dioxide transmission needs to be characterized for a particular application. As with OTR and WVTR, results depend on the material, measurement method and test conditions.

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

These parameters describe different aspects of barrier performance and should not be treated as interchangeable. The appropriate measurements should be selected according to the intended application.

How Are Film Barrier Properties Evaluated?

Film barrier performance is evaluated by measuring the transmission of a selected gas or vapor through a sample under defined conditions.

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

In many film testing systems, a 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 that passes through the film.

The instrument records the transmission behavior and uses the measurement data to determine the relevant parameter according to the selected method.

When evaluating a film, laboratories should consider:

• The transmission parameter being measured.
• The sample’s material composition and thickness.
• The test temperature and 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 test procedure and calculation method depend on the instrument and applicable test method. Results should always be interpreted in the context of the conditions under which they were obtained.

What Is the Difference Between Barrier Performance and Permeability?

Barrier performance, permeability and transmission rate are related concepts, but they describe different aspects of material behavior.

Barrier performance is a broad description of how effectively a material limits transmission of a particular substance under defined conditions.

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 the material thickness, according to the calculation approach used.

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

These quantities cannot always be compared directly. When reviewing technical data, check the parameter, units, thickness assumptions, test conditions and calculation method.

For packaging applications, OTR, WVTR and CO₂TR are commonly used to describe the transmission of oxygen, water vapor and carbon dioxide, respectively.

Which Factors Influence Film Barrier Performance?

Barrier performance depends on the material and its structure, as well as the conditions under which the measurement is performed.

Material Composition

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

Film Thickness

Thickness affects the path through which a substance must travel. Comparisons based on thickness should be made carefully and under consistent conditions, because thickness alone does not determine barrier performance.

Multilayer Structures and Laminates

Many packaging films combine several layers to obtain a desired balance of barrier and other functional properties.

The overall behavior of a multilayer film depends on the materials used, their individual thicknesses, the interfaces between layers and the manufacturing process.

Testing the complete structure provides information about the barrier performance of the material as a whole.

Explore [Permeability Testing of Multilayer Films and Laminates].

Temperature and Relative Humidity

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

For meaningful comparisons, the test conditions should be defined, controlled where required and documented.

Material Defects and Sample Preparation

Damage, wrinkles, contamination or inadequate sample mounting can affect a measurement. Correct preparation and handling help ensure that the test represents the material being evaluated.

Test Method and Measurement Range

Different methods or measurement conditions can produce results that are not directly comparable. The chosen instrument must be suitable for the expected transmission values and the relevant test procedure.

Film Barrier Properties in Packaging Applications

The required barrier properties depend on the product, the packaging design and the intended conditions of use.

Food Packaging

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

Explore Permeability Testing for Food Packaging.

Plastic Films

Plastic films are used in many packaging applications, with barrier performance varying according to material type, thickness and structure.

Testing can help compare alternative film materials under defined conditions.

Explore Permeability Testing of Plastic Films.

Flexible Packaging

Flexible packaging can combine films, coatings, laminates and multilayer structures to achieve specific material properties.

Barrier testing helps characterize the selected structure and compare alternatives during packaging development.

Explore Permeability Testing of Flexible Packaging.

Pharmaceutical Packaging

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

Permeability measurements can contribute to material characterization, but a measurement alone does not establish product safety or regulatory compliance.

How to Choose a Film Barrier Testing System

The appropriate testing system depends on the properties to be evaluated and the characteristics of the samples.

Before selecting an instrument, consider:

• Measurement parameters: whether OTR, WVTR, CO₂TR or multiple parameters are required.
• Material compatibility: the type, thickness and structure of the films being tested.
• Expected transmission values: the required measurement range.
• Environmental conditions: the temperature and humidity conditions needed for the application.
• Test methods: the procedures and reporting requirements relevant to the material.
• Laboratory workflow: sample throughput, data recording and reporting needs.

If several barrier parameters need to be evaluated, a system capable of measuring multiple parameters may help streamline laboratory work. Instrument suitability should be confirmed against the actual samples and intended test methods.

ExtraSolution Instruments for Barrier Property Measurement

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

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 transmission rate (WVTR) measurement.

Explore PermeH2O.

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

Conclusion

Film barrier properties are essential when evaluating materials designed to control the transmission of oxygen, water vapor and carbon dioxide.

OTR, WVTR and CO₂TR provide complementary information about material performance. By selecting appropriate test methods, controlling relevant conditions and interpreting results correctly, laboratories can 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 testing requirements and identify a suitable measurement system.