Barrier Property Testing of Packaging Materials: Methods, Standards, and Applications

Barrier property testing of packaging materials measures the permeation of gases and water vapor through films, laminates, and finished packages, providing critical data for shelf-life prediction and quality control. Key parameters such as oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) are determined using internationally recognized methods from ISO, ASTM, and GB standards. This article presents a comprehensive overview of sample types, testing items, measurement principles, and typical applications of barrier property determination in the packaging industry.

Technical Overview

Barrier properties describe the ability of a packaging material to resist the permeation of gases, water vapor, and organic compounds. For packaged products such as food, pharmaceuticals, medical devices, and electronic components, the barrier performance of the packaging directly determines product shelf life, sterility maintenance, and overall quality preservation. The most commonly evaluated parameters are oxygen transmission rate (OTR), water vapor transmission rate (WVTR), and the permeability of other gases such as carbon dioxide and nitrogen.

Permeation through polymeric materials follows the solution-diffusion mechanism, in which permeant molecules are adsorbed on the high-concentration side, dissolve into the polymer matrix, diffuse through the bulk material, and desorb on the low-concentration side. Because permeation is strongly temperature-dependent and, for many materials, humidity-dependent, all barrier measurements must be performed under strictly controlled environmental conditions. Standard reference climates include 23 °C / 50% RH for general testing and 38 °C / 90% RH for tropical or accelerated conditions.

Barrier property determination is essential for material qualification, laminate structure design, supplier verification, process validation (e.g., after extrusion, coating, printing, or sterilization), and regulatory compliance. Accredited third-party laboratories routinely perform these tests according to ISO, ASTM, and GB standard methods to ensure reproducible and comparable results.

Testing Samples

Flexible Plastic Films and Laminates

Monolayer films such as PE, PP, PET, PA, and PVC, as well as multilayer laminates (e.g., PET/AL/PE, OPP/CPP, PA/EVOH/PE), are the most frequently tested sample types. Specimens are typically cut from flat film sheets and mounted between two test chambers with a defined test area.

High-Barrier and Coated Materials

Aluminum-metallized films, aluminum foil laminates, transparent oxide-coated (AlOx, SiOx) films, PVDC-coated films, and EVOH-containing structures exhibit very low transmission rates. These materials require high-sensitivity instruments capable of detecting permeation at levels as low as 0.001 cm³/(m²·24h) for oxygen.

Finished Packages and Containers

Bottles, cans, pouches, blister packs, thermoformed trays, caps, and closures can be tested as complete packages. Whole-package testing evaluates the combined barrier contribution of the material, seals, seams, closures, and any weak points introduced during filling and sealing operations.

Rubber, Elastomeric, and Paper-Based Materials

Rubber components used in pharmaceutical closures and medical device seals are tested for gas permeability. Paper, paperboard, and coated fiber-based materials are evaluated primarily for water vapor resistance, particularly when used in combination with plastic functional layers.

Testing Items

Barrier property determination covers a range of permeation measurements, each addressing a specific protection requirement:

• Oxygen transmission rate (OTR), expressed in cm³/(m²·24h) or cm³/(package·24h)
• Water vapor transmission rate (WVTR), expressed in g/(m²·24h) or g/(package·24h)
• Permeability of carbon dioxide, nitrogen, air, and other technical gases
• Permeance and permeability coefficient derived from transmission measurements
• Organic vapor and aroma compound permeation (e.g., flavors, solvents, fragrance loss or pickup)
• Whole-package gas and moisture barrier performance, including seal integrity effects

Testing Methods

Coulometric Sensor Method for Oxygen Transmission

Described in ASTM D3985, ASTM F1927, ISO 15105-2, and GB/T 19789, this method uses a coulometric oxygen sensor as an absolute detector. The specimen separates a chamber flushed with oxygen or air from a chamber swept by oxygen-free carrier gas (typically nitrogen). Oxygen permeating the specimen is carried to the sensor, where it is reduced electrochemically, generating a current proportional to the transmission rate. The method offers excellent sensitivity and is suitable for both high-barrier and medium-barrier materials. Relative humidity inside the test chamber can be controlled to evaluate humidity-dependent materials such as EVOH and PA.

Manometric (Pressure) Method for Gas Permeability

Specified in ASTM D1434, ISO 15105-1, ISO 2782, and GB/T 1038, this method measures gas permeability by monitoring the pressure increase in an evacuated downstream chamber. It is applicable to multiple test gases, including oxygen, carbon dioxide, nitrogen, and air, and provides permeability coefficients, diffusion coefficients, and solubility coefficients through data analysis. It is widely used for comparing fundamental gas transport properties of polymers.

Infrared Sensor Method for Water Vapor Transmission

Described in ASTM F1249, ISO 15106-2, and GB/T 26253, this technique employs an infrared humidity sensor to quantify water vapor permeating the specimen into a dry carrier gas stream. It provides rapid, high-precision WVTR results over a wide measurement range, from high-barrier laminates down to values of 0.001 g/(m²·24h) or lower with modern modulated sensor technology.

Gravimetric (Cup) Method for Water Vapor Transmission

Specified in ASTM E96/E96M, ISO 2528, and GB/T 1037, the gravimetric method seals the specimen over a cup containing a desiccant or water. The assembly is placed in a controlled humidity and temperature environment, and the weight change caused by water vapor movement is recorded periodically until steady state is reached. This classic method remains a reference procedure, particularly for moderate-barrier materials and coated papers.

Whole-Package Barrier Testing

For finished containers, methods such as ASTM F1307 (coulometric determination of oxygen transmission through packages) and related whole-container WVTR techniques are applied. The package is mounted in a test cell, with the interior purged by carrier gas while the exterior is exposed to the test gas or humid atmosphere. This approach captures the real-world barrier performance including seals, closures, and material variability.

Sample Conditioning and Test Environment Control

All specimens must be conditioned prior to testing, typically at 23 °C and 50% RH in accordance with ISO 291 or ASTM D618. Precise control of temperature (±0.5 °C or better) and relative humidity is mandatory, since a small deviation can significantly alter measured transmission rates. Steady-state permeation must be verified before results are reported.

Applications

Barrier property data support critical decisions across many industries:

• Food packaging: shelf-life modeling for oxygen-sensitive and moisture-sensitive products such as snacks, coffee, dairy powders, oils, and modified-atmosphere packaged foods
• Pharmaceutical packaging: qualification of blister films, pouches, and bottle systems for tablets, capsules, and moisture-sensitive drugs in line with pharmacopoeial and stability study requirements
• Medical devices: verification of sterile barrier systems that must maintain sterility until the point of use
• Electronics and semiconductors: moisture barrier evaluation of packaging related to moisture sensitivity level (MSL) classification and dry-pack requirements
• Emerging technologies: ultra-high barrier films for OLED displays, photovoltaic modules, and vacuum-insulated applications, where barrier performance below 10⁻⁴ g/(m²·24h) is required
• Material development: comparison of resin grades, coating formulations, laminate structures, and the effect of processing, printing, or sterilization on barrier performance

FAQ

What are the standard test conditions for barrier property measurement?

Common conditions include 23 °C / 0% RH and 23 °C / 50% RH for ambient evaluation, and 38 °C / 90% RH for humid or tropical conditions, following the conventions of ASTM and ISO methods. The selected condition must always be reported together with the result.

How are OTR and WVTR results expressed?

OTR is expressed in cm³/(m²·24h) for flat films or cm³/(package·24h) for whole packages, while WVTR is expressed in g/(m²·24h) or g/(package·24h). Both parameters are defined at specified temperature and humidity conditions.

Can finished packages be tested instead of flat film samples?

Yes. Whole-package testing is strongly recommended when seals, closures, or three-dimensional geometry may dominate overall barrier performance. Combining film-level and package-level testing provides the most complete assessment.

Why do barrier results sometimes differ between laboratories?

Differences typically arise from insufficient sample conditioning, temperature or humidity control deviation, unverified steady-state measurement, specimen preparation damage, or the use of different standard methods. Testing at accredited third-party laboratories in accordance with standardized procedures minimizes such variability.

How long does a barrier test take?

Test duration depends on the barrier level of the material. Medium-barrier films may reach steady state within a few hours, whereas high-barrier foil laminates and oxide-coated films can require several days due to extremely low permeation fluxes.