Packaging testing – permeability analysis
How we test the rate at which oxygen or water vapour pass through packaging materials – an important consideration when the barrier properties are designed to maintain a protective atmosphere or prevent dehydration of the product.
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Permeability testing is used to measure oxygen transmission rates and water vapor transmission rates through plastic films and containers. This is particularly important when defining specification sheets which packaging manufacturers will do, it's also important to food manufacturers to ensure that they are using the correct barrier materials for their foodstuffs to ensure shelf-life. A section of film is cut using a template, the test is always carried out in duplicate and the samples are removed from the same area of film. One unit measures oxygen transmission rates and the other measures water vapor transmission rates. The grease ensures that the sample is placed in the chamber with an airtight seal. The temperature and humidity of the chambers can be varied depending on how the materials are to be stored. Distilled water is used to vary the humidity. With the oxygen test oxygen is flushed on top of the film and nitrogen underneath the film, any oxygen that passes through the film during the test is carried out in the nitrogen and detected on a sensor at the back of the machine which automatically gives a computer readout. This is the same for water vapor, nitrogen containing water vapor is flushed on top of the film and dry nitrogen is flushed underneath the film, any water vapor that passes through the film is carried out in the dry nitrogen and detected on a sensor at the back of the machine. Depending on the barrier properties of the film the test can take between one and five days, during the test a graph is produced showing the change in transmission rate over time.