How to test the air permeability of
Stretch Film? What is the test method?
The air permeability of the stretched film is mainly expressed by the gas permeability and the gas permeability coefficient. The gas permeation rate refers to the volume of gas permeating the unit area of the tested film in unit time under the action of constant temperature and unit pressure difference when permeating stably; During stable permeation, the gas volume per unit thickness and unit area of the detected film per unit time is permeated.
The air permeability test of the stretched film is carried out on a special instrument. The method is to separate the high pressure chamber and the low pressure chamber in the instrument with the film to be tested and seal it well. There is a test gas of about 105Pa in the high-pressure chamber, and the volume of the low-pressure chamber is known. At the beginning of the test, the air in the low-pressure chamber is pumped out with a vacuum pump, and the pressure is close to zero;
The following points should be paid attention to when doing the air permeability test of thin stretch film:
1. The temperature should be strictly controlled during the test.
2. It takes a long time for degassing and ventilation during the stretch film test. The detection of the pressure in the low pressure chamber should be recorded after the stable penetration is achieved.
3. The test inspection process is carried out under the pressure difference between the two high and low pressure chambers. Therefore, in order to ensure the accuracy of the test data, we must pay attention to the tightness of each system in the working instrument.
