How to Test Oxygen Permeability of Food Packaging According to ASTM D3985 Standard

 

How to Test Oxygen Permeability of Food Packaging According to ASTM D3985 Standard

 

Oxygen transmission rate is a crucial indicator for evaluating the barrier properties of packaging materials. For food packaging, excellent oxygen barrier performance is essential to ensure food safety and effectively extend shelf life. ASTM D3985, "Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor," is a standard test method that employs the coulometric sensor principle to measure the oxygen transmission rate of plastic films, sheeting, laminates, paper-plastic composites, plastic-coated fabrics, and similar materials. This evaluation helps determine the packaging material's ability to block oxygen, ensuring food remains unaffected by oxygen throughout its shelf life.



Understanding the Coulometric Sensor Method

The coulometric sensor method involves clamping the test specimen (the food packaging material) into a permeation cell within the testing instrument, creating a sealed barrier. Oxygen is introduced to one side of the specimen, while a stream of nitrogen acts as a carrier gas on the other side. As oxygen permeates through the specimen, it is carried by the nitrogen into a coulometric sensor, where an electrochemical reaction occurs, generating an electrical signal. This signal is directly proportional to the amount of oxygen passing through the material per unit of time, allowing for the precise calculation of the oxygen transmission rate.

 

Recommended Instrumentation

For accurate oxygen transmission rate testing following ASTM D3985, instruments like Labthink's C203H and C206H Oxygen Transmission Rate Test Systems are recommended. Alternatively, for integrated testing capabilities of water vapor transmission rate, the C403H and C406H Oxygen/Water Vapor Transmission Rate Test Systems (which combine oxygen and water vapor permeability testing) are also suitable.

C203H

C206H

 

Test Preparation

  • Sample Quality: Ensure the samples are representative, have uniform thickness, and are free from defects such as wrinkles, folds, or pinholes. Cut the samples to a size compatible with the testing instrument, use a thickness tester conforming to relevant standards (e.g., ASTM D374 for plastics) to measure the thickness at a minimum of five points on the sample.
  • Conditioning: Place the samples in a desiccator or in a controlled environment for a minimum of 48 hours to ensure proper conditioning.
  • Environmental Control: Maintain the testing environment at 23°C ± 2°C with a relative humidity of 50% ± 10%.

Labrhink C406H Oxygen /Water Vapor Transmission Rate Test System

Testing Procedure

  1. Purging the Permeation Cell: Open the nitrogen carrier gas valve and purge the permeation cell with nitrogen at a flow rate of 50 mL/min to 60 mL/min for 3 to 4 minutes to remove any residual air. Afterward, reduce the flow rate to 5 mL/min to 15 mL/min and maintain it for 30 minutes.
  2. Zero Voltage Calibration: After purging with nitrogen for 30 minutes, switch the valve to the coulometric sensor position. Record a stable, low voltage reading as the zero voltage baseline.
  3. Oxygen Introduction: Close the nitrogen supply to the oxygen side of the chamber and introduce oxygen. The voltage output from the coulometric sensor will gradually increase until it reaches a steady, constant value, which is recorded as the test voltage.
  4. Result Calculation: Utilize the data collected and apply the formulas provided in ASTM D3985 to calculate the final oxygen transmission rate.

 

By following these steps, you can accurately test the oxygen barrier performance of food packaging materials, providing a scientific basis for food packaging design and production. For more in-depth technical discussions, Labthink looks forward to fostering further technical exchange and cooperation with enterprises and institutions across various industries.

 

 

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