Packaging machinery breathability test metrics

Packaging machinery breathability test metrics

First, the impact of air permeability testing
There are many factors that affect the permeability test, such as sensor accuracy, effective range, system leakage, sample handling, material properties, test environment, hardware design, software processing, and so on. Many of the influencing factors are determined by the inherent nature of the design. From the perspective of applications, users are not concerned with how the manufacturers improve these conditions, but what requirements they meet and what conditions are met in order to obtain objective and accurate results. Test data, this article describes the two main measurement indicators - "blank test" and test results repeatability.
Second, "blank test" data
1. "Blank test"
"Blank test" is a reflection of the equipment's comprehensive error. The test error is due to the existence of factors that cannot be effectively improved in the breathability test, such as system leakage and other unpredictable factors. Although the "blank test" has not been clearly defined in the air permeability test standard, the test work on "blank test" has been widely recognized by the society.
2. Blank Test Data for VAC-V1
In order to obtain the combined effect of all factors, the VAC-V1 uses a sample that is considered to be completely gas-tight and is tested in accordance with normal operating procedures, and then the combined effects of system leakage and other factors on the overall equipment are observed. The "blank test" value obtained by this method is more reliable in determining the pros and cons of the equipment.
Labthink VAC-V1 "blank test" uses 55μm copper foil (thick aluminum foil sample can also be used) as a sample for testing, strict sealing, the system vacuum for 48h (before entering the test state, the vacuum degree of the upper and lower chamber should be Below 10Pa), the test was performed using the conventional volume of the VAC-V1 (the device has an optional extended volume function). In order to analyze the impact of changes in the temperature and humidity of the environment on the test, there is no automatic control of the temperature of the device. The pressure time curve is shown in Figure 1. (In addition, there are temperature and humidity time curves, which will not be described here.)
The test lasted 12 days (including vacuuming time), the temperature was between 18 and 23°C, and the ambient humidity was 50±8% RH (if the automatic temperature control function of the equipment was used, the test effect was better). After entering the test state, the pressure in the lower chamber rises by 6.0Pa. The test result is 0.023ml / m2 · 24h · 0.1MPa (if the extended volume or fuzzy test mode is selected, the comprehensive influence of the above factors can be effectively reduced, and the The test result will be more accurate). With the data list analysis of the entire test curve, it is not difficult to find that the temperature and humidity changes have little effect on the test.
In the first 60 hours, the pressure change was relatively large, rising from 0 Pa to 3.84 Pa. In the subsequent 180 hours, the pressure increase decreased, and the permeability was 0.012 ml/m2·24h·0.1MPa. The reason why this phenomenon occurs is related to the degassing state. Tests have shown that prolonging the evacuation time can effectively improve the impact on the test results.
Third, data repeatability
1. Data repetitive elements
Since each component manufacturer has a large gap between the selected components when implementing a test method, the data repeatability of the device is also an important indicator for evaluating the device. By analyzing the data repeatability of the equipment, you can better understand the equipment's detection data errors and fluctuations, and improve the detection efficiency. Data reproducibility includes: S (standard deviation standard deviation), CV (percent coefficient of variation data fluctuation percentage), and LSD (least significant difference between two individual test results based on a 95% confidence level 95% confidence level of two independent test results The minimum effective difference.
2. Measured data
Five samples of A, B, C, D, and E were selected for oxygen permeability detection using a Labthink VAC-V1 gas permeameter. The test temperature, O2GTR value, and test results of the five kinds of samples are shown in Table 1:
A, D test specimens provided by the Thai Packaging Testing Center
Sample B supplied by Mecadi Laboratories, Germany
With the increase of O2GTR value of the five samples, the standard deviation has increased, and the data fluctuation has gradually decreased. It is mainly due to the effect of the degassing state of the sample and the comprehensive factors on the test chamber when testing the high barrier property sample, which is more obvious than the detection of the middle and low barrier properties sample, for example, the oxygen permeability of the samples B and E. The results of the sexual test and the respective average O2GTR values ​​differ by 0.4. For Sample B, the data fluctuation accounted for 2.06%, while for Sample E it was only 0.0332%. Therefore, discussing the value of the fluctuation independently is somewhat partial. Pay attention to the barrier properties of the sample.
"Blank test" data and the reproducibility of test results are important indicators for measuring air permeability testing equipment. Test errors are not purely determined by equipment, but also related to test principles. Generally, it can be considered that the blank test result of the equipment has a great influence on the detection of the high barrier sample, but the repeatability of the device data is a comprehensive reflection of the data error detected by the device in any range of gas permeability.

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