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Measurement index of permeability of packaging machinery

来源: 2013-6-13 15:49:15      点击:

Influence factors of permeability test
There are many factors affecting the permeability test, such as the precision of the sensor, the effective range, the system leakage, the sample processing, the material characteristic, the test environment, the hardware design, the software processing and so on. Many of these factors are decided by congenital design, from the perspective of application, the user is not concerned with the manufacturer is how to improve these conditions, but to what, after what conditions, in order to obtain accurate test data, this paper introduces two main indicators: blank test and test the results of repeatability.
Two, blank test data
1, blank test"
"Blank test" is the reflection of the comprehensive error. The test error is due to the fact that there are some factors that can not be effectively improved in the air permeability test, such as system leakage and other unpredictable factors. Although there is no clear "blank test" in the standard of air permeability test, the test of "blank test" has been widely recognized by the society.
2, VACV1 "blank test data"
In order to obtain the comprehensive effect of all the factors that use numerical VACV1 sample completely airtight test in normal operating procedures, and then to comprehensive effect of leakage and other factors on the equipment. The blank test value obtained by this method is more reliable to determine the quality of the equipment.
LABTHINKVAC V1 "" blank test using 55 M copper foil (aluminum foil can be used thicker specimens) as specimens, strict sealing, vacuum pumping system (48H in test, upper and lower vacuum to below 10PA), conventional V1 (volume using the VAC function of the volume expansion with optional test equipment). In order to analyze the influence of environmental temperature and humidity on the test, the automatic temperature control function of the equipment is not started. The pressure time variation curve is shown in figure 1. In addition, there is a temperature time, humidity time curve, no longer repeat here
The experiment lasted 12 days (including the vacuum time), the temperature was between 18 and 23 DEG C, the ambient humidity was in the range of 50 ~ 8%RH (such as the use of automatic temperature control function of the equipment, the test effect is better). Enter the test status after subarachnoid pressure were increased by 6.0PA, the test results is 0.023ML / M2 - 24H - 0.1MPA (if the expansion volume or fuzzy test mode, comprehensive effect of various factors above can be effectively reduced, the test results will be more accurate). It is not difficult to find out the influence of temperature and humidity on the experiment with the data list.
In the initial 60H, the pressure change is relatively large, from 0PA to 3.84PA, in the subsequent 180H, the increase in pressure decreased, equivalent to 0.012ML / M2 / 24H / 0.1MPA. The reason is that this phenomenon is related to the degassing state. The results show that the vacuum pumping time can effectively improve the effect of the test results.
Three, data repeatability
1, the data repeatability factor
Due to the various manufacturers in the realization of a test method, the selection of a large gap between the components, so the equipment is also an important indicator of the evaluation of data equipment. By analyzing the data repeatability of the equipment, we can know more about the error and fluctuation of the data and improve the detection efficiency. The repeatability of the data include: S (STANDARDDEVIATION standard deviation) and CV (PERCENTCOEFFICIENTOFVARIATION and LSD (data fluctuation percentage) two independent test results of LEASTSIGNIFICANTDIFFERENCEBETWEENTWOINDIVIDUALTESTRESULTSBASEDONA95%CONFIDENCELEVEL 95% confidence level of the minimum effective difference).
2, measured data
Using A, B, C, D, E of five samples of oxygen through detection, using LABTHINKVACV1 gas permeability tester. The test temperature, O2GTR value and test results of the five samples are shown in table 1:
A, D samples from the Thailand packaging testing center
B samples provided by the German MECADI Laboratory
With the increasing of the O2GTR value of five kinds of samples, the standard deviation increases and the fluctuation of the data decreases. Is mainly due to the detection of high barrier impact test specimens, specimen degassing and comprehensive factors on the testing cavity, than to detect low barrier specimen is obvious, for example, a sample B, E oxygen permeability test results and the average O2GTR value is 0.4 for the sample B, data fluctuations accounted for 2.06%, for the sample E is only 0.0332%, so the numerical fluctuation is discussed separately some one-sided, but also pay attention to the barrier of sample.
The blank test data and the repeatability of test results are important indicators to measure the permeability testing equipment. The test error is not only determined by the equipment, but also related to the test principle. General equipment can be considered, to detect the influence of blank test results depend on high barrier samples is large, but the equipment data repeatability is the equipment at any air data error range detected by the comprehensive embodiment.