As we all know, flexible packaging materials such as plastic films and sheets have the advantages of low cost, light weight, and easy processing, and are widely used in the packaging of various daily products such as food and medicine. According to different engineering and application needs, the barrier properties of flexible packaging materials such as plastic films and sheets are different. Sometimes high barrier properties to block oxygen are required to prevent the intrusion of oxygen. Sometimes low barrier properties with good oxygen permeability are required. To facilitate the exchange of oxygen inside and outside the packaging. The breathability performance of flexible packaging materials such as plastic films and sheets directly affects the quality of their packaging products. At present, the methods for testing the air permeability of plastic films include pressure method (differential pressure method and isobaric method), concentration method, volume method, gas chromatography method and heat conduction method. According to different testing methods, different types of plastic film air permeability testing devices have been developed at home and abroad. Among them, the differential pressure method is the primary method in testing the air permeability of plastic films. International film air permeability testing standards based on the differential pressure method include ASTM D1434, ISO15105-1, ISO 2556-2001, JIS K7126, etc. The standards implemented in my country are GB/T1038-2000, GB/T 5453-1997, etc., fully automatic Fabric air permeability meter 1 is a test instrument.

The main parameters:

1. Pressure difference range: 0~4000Pa;

2. Measurable air permeability: 0.2-12826mm/s;

3. Measurement error: <±2%;

4. Measurable fabric thickness: <12mm;

5. Air suction volume adjustment: dynamic adjustment through data feedback;

6. Sample area setting circle: 5cm2, 20cm2, 50cm2, 100cm2;

During the test, the vacuum pump pumps the vacuum on the low-pressure side of the test device to below 27Pa. The leakage of the system has a great influence on the test results. The smaller the leakage, the more accurate the test results. On the contrary, the rougher the test results, the higher the barrier properties of the plastic film. When the sealing material and sealing technology are certain, the key factor affecting the sealing performance of the test device is its sealing structure. Under the condition of a certain temperature sensor, in order to make the temperature of the test environment meet the national standard requirements, it is necessary to adopt appropriate constant temperature control technology. At present, the air permeability testing device adopts a single-layer sealing structure. The advantage is that the structure is simple. The disadvantage is that the leakage of gas is relatively large, causing a relatively large change in pressure. For testing high-barrier films, its sealing performance is difficult Meet engineering application requirements. This paper analyzes the current research status of air permeability testing devices based on the pressure difference method, and proposes several factors that affect the performance of air permeability testing devices. It is necessary to reasonably handle the air permeability testing issues of high-barrier films. With the current vacuum technology and sealing technology capabilities, without drastically increasing the testing cost, it is possible to develop a testing device that meets the national standard requirements and can directly and accurately test the air permeability of high-barrier films by changing the single sealing structure design and appropriate constant temperature control technology.

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