The barrier performance of sealing film directly affects product shelf life and quality stability. Oxygen Transmission Rate (OTR) and Water Vapor Transmission Rate (WVTR) are the two core indicators for evaluating barrier properties. Leadtra Packaging provides an overview of testing methods and industry standards to help you understand how sealing film builds an effective protective barrier for your products.

1. Oxygen Transmission Rate (OTR): The First Line of Defense Against Oxidation

Oxygen is a primary factor in lipid oxidation, vitamin loss, and microbial growth. Sealing films with excellent oxygen barrier properties can effectively delay product degradation and extend shelf life.

Mainstream Testing Methods

Isostatic Method (Coulometric Sensor Method): Currently the most widely used high-precision method. During testing, the sealing film divides the test chamber into two sides — one side is flushed with high-purity oxygen, the other with high-purity nitrogen (carrier gas). Oxygen that permeates through the film is carried by the nitrogen to a coulometric sensor, which calculates the oxygen transmission rate by measuring the current. This method offers high sensitivity, especially suitable for testing medium- to high-barrier materials, and is not affected by moisture interference.

Differential Pressure Method: Creates a pressure difference across the film and calculates the transmission rate by measuring pressure changes on the low-pressure side over time. The testing principle is straightforward, but high humidity can affect pressure sensor accuracy, making it typically suitable for testing under dry conditions.

Applicable Standards: The isostatic method follows GB/T 19789, ASTM D3985, etc.; the differential pressure method follows GB/T 1038.

Typical Values: High-barrier aluminum foil composite films can achieve OTR values of <1 cm³/(m²·24h·0.1MPa) or even lower.

2. Water Vapor Transmission Rate (WVTR): A Key Indicator of Moisture Resistance

WVTR reflects the ability of the sealing film to prevent water vapor permeation, which is particularly critical for products with high moisture protection requirements (such as milk powder, pharmaceuticals, and dry goods).

Testing Principle: A specific temperature and humidity difference is established across the film, and WVTR is calculated by measuring the mass or volume of water vapor that permeates through a unit area of the film per unit time. Standard test conditions typically include 38°C/90%RH, 23°C/85%RH, etc.

Applicable Standards: Relevant testing can refer to ASTM E398, GB/T 17146, etc. ASTM E398 uses a dynamic relative humidity measurement method that closely simulates actual product storage environments.

3. Whole Package Container Barrier Testing

In addition to testing the sealing film alone, sometimes it is necessary to evaluate the overall oxygen barrier performance of the entire package (including the bottle body and sealing film), as this more closely reflects the actual storage condition of the product. Following ASTM F1307 or GB/T 31354 standards, the entire package (such as a bottle) is placed in a test chamber, purged with nitrogen on the inside, and exposed to oxygen on the outside to measure the overall oxygen transmission rate.

Conclusion

Oxygen Transmission Rate and Water Vapor Transmission Rate are the core indicators for evaluating the barrier performance of sealing film. Through standardized testing methods combined with industry standards, you can accurately determine whether the sealing film provides sufficient protection for your product quality. Leadtra Packaging offers custom sealing film solutions that meet high-barrier requirements. You are welcome to send us samples, and we can discuss the most suitable barrier solution for your product.