Vacuum method is the most representative of the differential method of a test method. The
test principle is to use the sample to separate the
permeate chamber into two separate spaces. First, both sides of the
sample are evacuated and then filled to one side (A high pressure side) Absolute
pressure) of the test gas, while the other side (B low side) is to
maintain a vacuum state, the sample on both sides of the formation of
0.1MPa test gas pressure. The
gas permeation of the test gas enters the low pressure side through the
film and causes a change in the pressure on the low pressure side. The
amount of gas permeation (GTR) of the test gas can be calculated using
the formula by measuring the amount of pressure on the low pressure side
with a high precision vacuum gauge. The relevant standards are ISO 2556, ISO 15105-1, ASTM D 1434 (M method), GB 1038, JIS K 7126 (A method) and the like.
The gas permeation (GTR) provided by ISO 15105-1 is calculated as follows:Where: V C - the volume of the low pressure side;T - test temperature (thermodynamic temperature);Pu - high pressure side gas pressure;A - effective penetration area;Dp / dt - the amount of change in pressure per unit time on the low pressure side when the permeation state is stable;R - gas constant.
Vacuum method is the use of negative pressure method to achieve 0.1MPa on both sides of the sample pressure difference, of course, can also be achieved by positive pressure difference method, the most commonly used positive pressure method is the volume method. Because the volumetric method does not need to vacuum the infiltration chamber, and does not need to maintain the vacuum, so reduce the equipment manufacturing and test the difficulty. The relevant test standards are ASTM D 1434 (V method) and so on.
The pressure difference method is very good for the test gas. Due to the support of the membrane technology theory, the vacuum method has been used as a basic method in the permeability test, and this method has been adopted by the scientific research and testing organization. With the advancement of vacuum gauge detection technology and the application of high vacuum technology in equipment design, the detection accuracy of the equipment and the repeatability of the test data are greatly improved. Its outstanding advantage is that through a test to obtain the material permeability coefficient, diffusion coefficient, solubility coefficient of three barrier indicators.
In the purchase of vacuum pressure differential permeability testing equipment, the need to pay attention to the following parameters: the test chamber can achieve the degree of vacuum, vacuum gauge accuracy and range, "blank test" data and test data repeatability, and whether the equipment from Temperature control function. The vacuum of the test chamber not only reflects the vacuum capacity of the vacuum pump, but also reflects the sealing performance of the test cavity and the relevant pipeline. If there is leakage in the mechanical structure, the test result will be seriously disturbed and can not reflect the material The real barrier. If only a test failed to achieve the required degree of vacuum, most likely due to improper sample clamping caused by the folder.
Standard requirements of the accuracy of the vacuum gauge should not be less than 6Pa, the current resolution of the vacuum gauge is better than its full range of 0.1%, because the resolution of the test components are better than its test accuracy, so the vacuum gauge range To less than 6kPa. The "blank test" data and the repeatability of the test data are a comprehensive measure of the impact of the equipment on various factors. The temperature and humidity control of the test environment also has an effect on the test results. In particular, the effect of temperature on the barrier test is most pronounced. January 17, 2005 and February 21, Lanqing Lab Forum. When the positive pressure difference method is purchased, since this method does not need to be vacuumed, it is only necessary to pay attention to the accuracy and range of the pressure sensor, the "blank test" data and the repeatability of the test data.
The gas permeation (GTR) provided by ISO 15105-1 is calculated as follows:Where: V C - the volume of the low pressure side;T - test temperature (thermodynamic temperature);Pu - high pressure side gas pressure;A - effective penetration area;Dp / dt - the amount of change in pressure per unit time on the low pressure side when the permeation state is stable;R - gas constant.
Vacuum method is the use of negative pressure method to achieve 0.1MPa on both sides of the sample pressure difference, of course, can also be achieved by positive pressure difference method, the most commonly used positive pressure method is the volume method. Because the volumetric method does not need to vacuum the infiltration chamber, and does not need to maintain the vacuum, so reduce the equipment manufacturing and test the difficulty. The relevant test standards are ASTM D 1434 (V method) and so on.
The pressure difference method is very good for the test gas. Due to the support of the membrane technology theory, the vacuum method has been used as a basic method in the permeability test, and this method has been adopted by the scientific research and testing organization. With the advancement of vacuum gauge detection technology and the application of high vacuum technology in equipment design, the detection accuracy of the equipment and the repeatability of the test data are greatly improved. Its outstanding advantage is that through a test to obtain the material permeability coefficient, diffusion coefficient, solubility coefficient of three barrier indicators.
In the purchase of vacuum pressure differential permeability testing equipment, the need to pay attention to the following parameters: the test chamber can achieve the degree of vacuum, vacuum gauge accuracy and range, "blank test" data and test data repeatability, and whether the equipment from Temperature control function. The vacuum of the test chamber not only reflects the vacuum capacity of the vacuum pump, but also reflects the sealing performance of the test cavity and the relevant pipeline. If there is leakage in the mechanical structure, the test result will be seriously disturbed and can not reflect the material The real barrier. If only a test failed to achieve the required degree of vacuum, most likely due to improper sample clamping caused by the folder.
Standard requirements of the accuracy of the vacuum gauge should not be less than 6Pa, the current resolution of the vacuum gauge is better than its full range of 0.1%, because the resolution of the test components are better than its test accuracy, so the vacuum gauge range To less than 6kPa. The "blank test" data and the repeatability of the test data are a comprehensive measure of the impact of the equipment on various factors. The temperature and humidity control of the test environment also has an effect on the test results. In particular, the effect of temperature on the barrier test is most pronounced. January 17, 2005 and February 21, Lanqing Lab Forum. When the positive pressure difference method is purchased, since this method does not need to be vacuumed, it is only necessary to pay attention to the accuracy and range of the pressure sensor, the "blank test" data and the repeatability of the test data.
评论
发表评论