The barrier property of packaging material is one of the main factors that determine its application field and content quality. Oxygen, carbon dioxide and other gases penetrating through packaging materials will significantly affect the quality of products. Therefore, it is necessary to select materials with appropriate barrier properties in combination with the expected shelf life of products in packaging design. Air perm air permeability tester is one of the main testing equipments purchased by packaging material manufacturers and users in recent years.
Development of permeability test
Gas permeability test, also known as gas barrier test or gas permeability test, mainly investigates the barrier performance of films and sheets to common inorganic gases, and is one of the main barrier performance indexes of materials. Usually, the oxygen permeability of materials is tested. Because of the wide use of modified atmosphere packaging, it is necessary to test the permeability of carbon dioxide and nitrogen of packaging materials.
The air permeability test methods can be divided into Differential-pressure method and Equal-pressure method. Pressure difference method is widely used, which can be divided into vacuum pressure difference method and positive pressure difference method (volume method). With the development of trace oxygen detection technology, trace oxygen sensors are applied step by step in the field of oxygen permeability test of materials, that is, the sensor method in permeability test.
Different gas sensors can be used to detect the permeability of different gases to materials. At present, the sensor method for detecting oxygen and carbon dioxide has matured. In addition, the air permeability of materials can be detected by meteorological chromatography. Both sensor method and meteorological chromatography can be classified as isobaric method for permeability test.
Air Permeability Test Equipment Test principle
There are two methods for testing air permeability, namely, constant pressure difference and constant flow pressure difference. The constant pressure difference flow measurement method refers to keeping a constant pressure difference on both sides of the sample, and calculating the air permeability of the sample by testing the air flow passing through a given area of the sample within a certain time.
Constant flow pressure difference rule means that the air flow passing through the sample vertically is kept constant, and the air permeability of the sample is obtained by testing the pressure difference on both sides of the sample under this condition.
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