Source: Link Testing Instrument Co.,Ltd.
Carbon dioxide has the functions of inhibiting the growth of aerobic microorganisms, regulating weak acidity, and weakening plant aerobic respiration. Therefore, many products are packaged in modified atmosphere packaging containing carbon dioxide to make full use of the above properties of carbon dioxide to prevent products from mildew, rancidity, and extend shelf life. For example, a certain proportion of oxygen, nitrogen, and carbon dioxide mixed gas is filled in the packaging of fresh meat products to keep the meat products bright red, prevent the oxidation of meat products, and inhibit the reproduction of aerobic microorganisms; fresh fruits can be packaged in a modified atmosphere by using a suitable proportion of oxygen and carbon dioxide mixed gas as the gas to regulate and inhibit the respiration of the fruit.
For modified atmosphere packaging, the proportion of gas components inside the packaging directly affects the quality of the packaging. Selecting packaging materials with suitable gas barrier properties to prevent excessive loss or accumulation of gas inside the packaging is an important measure to ensure the stability of the proportion of each component of the mixed gas. This article introduces the test method of carbon dioxide permeability by testing the carbon dioxide barrier property of soft plastic packaging materials.
Test Instruments At present, the test method for carbon dioxide permeability of soft plastic packaging materials is mainly the differential pressure method. The method standard based on this test is GB/T 1038-2000 "Plastic Film and Sheet Gas Permeability Test Method Differential Pressure Method", which is applicable to testing the gas permeation and gas permeation coefficient of various test gases such as oxygen, air, nitrogen, and carbon dioxide.
The test equipment used for this sample is the GTC-203H differential pressure gas permeometer, which is independently developed and produced by Link Testing Instrument Co.,Ltd.
Test principle: The pressure difference method refers to a test method in which a certain pressure difference is maintained on both sides of the sample during the test, and the gas permeation of the sample is calculated based on the change in the pressure on the low-pressure side. The implementation process is as follows: after the sample is clamped into the test chamber of the equipment, the test chamber is divided into two test chambers, an upper chamber and a lower chamber, and the two test chambers are evacuated. Then, the upper chamber is filled with a test gas of a certain pressure. In this way, a certain pressure difference is formed on both sides of the sample. Under the action of the pressure difference, the test gas permeates from the upper chamber through the sample to the lower chamber. By real-time monitoring of the change in the pressure of the lower chamber over time, the gas permeation and permeability coefficient of the sample are calculated.
Test sample and test process
Test sample: The test sample tested this time is a plastic composite film packaging material. Test process: (1) Use a special sampler to cut 3 samples with a diameter of 97 mm from the surface of the sample. (2) Place the sample in a dryer at 23±2℃ and adjust the state for 48 hours. (3) After the sample is taken out, measure its thickness and take the average value of the measurement as the thickness of the sample. (4) Apply a layer of vacuum grease around the test cavity, place a piece of filter paper in the test area, then clamp the sample to the test cavity and clamp it with a clamping structure. (5) Connect the carbon dioxide gas source, set the sample name, thickness, test humidity, test temperature, test mode and other parameter information, turn on the vacuum pump, click the test option, and the test starts. After entering the test state, turn off the vacuum pump. After the test is completed, the equipment automatically displays the test values of the three samples.
Test results and analysis The carbon dioxide permeation of the three samples tested in this test under 23℃ and 0%RH conditions is 80.367 cm3/(m2·24h·0.1MPa), 81.669 cm3/(m2·24h·0.1MPa), and 77.304 cm3/(m2·24h·0.1MPa), respectively, with an average value of 79.780 cm3/(m2·24h·0.1MPa). For modified atmosphere packaging containing carbon dioxide gas, the carbon dioxide permeability of the packaging material is a performance indicator that should be focused on. The value of this indicator directly affects the change in the proportion of each gas component inside the packaging with the storage time. This article introduces the method of using the pressure difference method to test the carbon dioxide barrier performance of soft plastic packaging by testing the carbon dioxide permeability of plastic composite film samples. The test equipment is simple to operate, highly intelligent, has good uniformity of test results, and high detection accuracy.
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