PBI-Dansensor A/S believe that the interactions of certain food products with their surroundings can place special demands on the barrier properties of the packaging materials for these foods. In order to maintain their freshness, fruits and vegetables must be able to respire, or "breathe", consuming oxygen and producing carbon dioxide and water vapour. Other products, such as cheeses, continue the fermentation process, releasing carbon dioxide gas.
The choice of packaging films for such products is critical in order to enable these vital processes to take place, while simultaneously avoiding build-up of pressure inside the package, which could cause unsightly ballooning or even rupture of the package. Specifically, the ratio of the transmission rates (permeability) of carbon dioxide and oxygen, known as "selectivity", must be determined.
The L100-5000 manometric gas permeability tester is a simple, versatile instrument that can measure the permeability through foils of practically any common non-corrosive gas or gas mixture. Gases typically measured with this tester include air, oxygen, nitrogen, carbon dioxide, methane and helium.
The flexibility of this instrument enables its use in a variety of testing applications and markets. The ability to test with a variety of gas types makes the L100-5000 particularly suitable for measuring the permeation selectivity of various materials, notably the carbon dioxide/oxygen selectivity for packaging films for respiring food products.
The L100-5000 manometric gas permeability tester utilises one of the oldest and more recognised gas permeability testing methods: pressure change via gas transmission through films. A pressure difference across the sample is created by maintaining the test gas at atmospheric pressure in the upper chamber, while drawing a vacuum in the lower measuring chamber. As the gas permeates through the sample, the pressure in the lower measuring chamber increases. The instrument measures the time required for the lower chamber pressure to increase from a pre-defined lower limit to a pre-defined upper limit, and the measured time interval is then calculated into the gas permeability rate expressed in ml/m2/24 hr. The testing is fast and easy, providing gas permeability measurements within a matter or hours.
The tester contains two measuring chambers, providing extra flexibility in measurements. The two chambers can be utilised in a variety of ways, such as for testing of two different films with the same gas; testing of the same film with two different gases; and testing of the same film and gas at two different temperatures. Prior to testing, the L100-5000 is calibrated with a standard film of known permeability, which is provided with the instrument.
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