The barrier properties of packaging materials, whether it is water vapor transmission rate or oxygen transmission rate, should pay attention to the following aspects in the process of testing and testing results: 1The concept of permeability is obtained under the condition that the film conforms to Fick’s law. For oxygen, except for individual oxygen-absorbing materials, it generally conforms to Fick’s law. However, due to the interaction with many polymers during the permeation process of water vapor and organic matter, it generally belongs to Fick’s law-type diffusion. 2, For the conforming material, its structure is not necessarily symmetrical, so there is a problem with the front and back of the sample. certain materials such asPVDCcoatingBOPP, PVDCandPVCIn line with the hard sheet, the oxygen transmission rate measurement results of the front and back sides are quite different, and it can even reach1times. This is because during the actual test, the measured result is the sum of the penetration through the specimen and the penetration of the seal. 3, For packaging materials with high adsorption and hygroscopicity, the influence of adsorption and desorption on the experimental results should be considered during the experiment. At the same time, it should be clear that the equilibrium time is generally long, and even in the same environment, after The equilibrium state of different processes is not necessarily the same, that is to say, the equilibrium state of a material is not only related to the equilibrium environment, but also to the process. 4, should attach great importance to the leakage problem during the inspection process. The water vapor transmission rate and oxygen transmission rate obtained by any experiment are the sum of the penetration and leakage. Only when the leakage is negligible, the measured penetration is only is the most accurate. 5In addition, packaging materials and packaging are two different concepts. Using high-barrier packaging materials may not necessarily produce high-barrier packaging. From packaging material to package, and from package to consumer, many factors affect the final barrier properties of a product along the way.
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