Why does the milk powder packaging have the phenomenon of deflated bags?

Why does the milk powder packaging have the phenomenon of deflated bags? Quality problem: After a period of storage of the air-packed milk powder, the bag is deflated, but no leakage can be seen with the naked eye
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Analysis of the reasons: (1) Poor barrier property of the packaging material - the gas inside the package has a high amount of gas permeating the packaging material, that is, the gas permeation amount is large and the barrier property is poor, such as carbon dioxide and nitrogen inside
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Poor rubbing resistance - After being rubbed by external force, defects such as creases and pinholes appear in the packaging bag, resulting in poor barrier properties
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(2) Poor sealing performance during the packaging and processing of finished products - the bag body or heat-sealing part of the flexible plastic package is prone to air leakage under certain pressure or long-term storage, especially the sealing quality of the heat-sealing part is poor, such as heat sealing If the strength is too low or too high, and the heat sealing strength is not uniform, air leakage is more likely to occur
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Testing suggestions: ——Pay attention to the barrier properties such as nitrogen transmission rate, carbon dioxide transmission rate, etc.
after rubbing, nitrogen transmission rate after rubbing, carbon dioxide transmission rate after rubbing, etc.
The barrier performance after rubbing, sealing performance (negative pressure method), heat sealing strength and other properties daily monitoring
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——Adjust the parameters of the heat sealing machine to improve the quality of the heat sealing part; choose a packaging material with high barrier properties and good rubbing resistance or improve the quality of the existing packaging material
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Typical quality cases: ——Test sample: aluminum-plastic composite film for milk powder packaging (customer feedback that the milk powder is packaged with nitrogen, and the phenomenon of packaging shriveled bags becomes more and more obvious with the increase of storage time)
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——Targeted testing items: nitrogen transmission amount, nitrogen transmission amount after rubbing, sealing performance (negative pressure method), heat sealing strength
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——Test results: The nitrogen permeability before and after rubbing of the aluminum-plastic composite film is not much different, and the test values ​​are all low (that is, the barrier to nitrogen is better), indicating the barrier and rubbing resistance of the composite film.
The uniformity of the heat sealing strength value is poor, the heat sealing strength is only 18N/15mm at the poor heat sealing place, and the heat sealing strength can reach 45N/15mm at the good heat sealing place; at the same time, in the sealing performance (negative pressure In the test, when the finished milk powder was packaged at -65KPa, the heat-sealing seal leaked, which was lower than the average pressure of -90KPa that can withstand the similar excellent products, which further proved that the heat-sealing effect of the heat-sealing seal was poor
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Therefore, the occurrence of the deflated bag problem is mainly related to the heat sealing quality of the heat sealing
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