Permeability of films can be classified into high barrier, middle and low barrier according to the gas transmission rate of film at 25ìm thick. To high barrier film, the gas transmission rate is less than 5cm3/m2 • 24h • 0.1MPa; to barrier film, it is between 5 ~ 200 cm3/m2 • 24h • 0.1MPa; and to low barrier film it is greater than 200cm3/m2 • 24h • 0.1MPa. In the last few years, low barrier films has become a key developing point to the plastic packaging industry, and they are used widely in various industries such as food, pharmacy, cigarette, chemical, electronics, military and so on.

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