There are many kinds of plastic films, and their appearances are often very similar. Therefore, it is easy to be confused during the production of composite process, which may lead to differences in product performance, even scrapping and other production accidents. For the technical personnel engaged in the flexible packaging industry, it is an essential skill to master the identification methods of commonly used flexible packaging plastic films. There are many identification methods for plastic film, which can be generally divided into physical methods and chemical methods. The former identifies the plastic film according to its physical properties (transparency, mechanical strength, brittleness, heat sealing, heat resistance, etc.) or physical characteristics; The latter distinguishes plastic films according to their chemical properties (flammability and solubility) or chemical characteristics. It is necessary to be familiar with the main physical and chemical properties of various commonly used plastic films (LDPE, PP, PS, BOPP, PVC, PVDC, BOPET, PA, etc.). (1) The visual method is based on the transparency of the plastic film. The opaque or translucent ones are LDPE and ordinary PP (except BOPP). (2) According to the identification of the low temperature resistance of the film, the film is placed in the refrigerator for cooling treatment to reduce its temperature to 0 zhang, and their brittleness changes are observed. PP becomes brittle, except BOPP, which becomes brittle only when it is cooled to – 20 ^. (3) According to the identification of special mechanical properties, such as conducting a simple impact puncture test on films to compare their puncture resistance and brittleness, PVDC, BO PET, PA and LLDPE are difficult to puncture. (4) According to the identification of the high temperature resistance of the films, the films were put in the 1000 special cooking for 5min, and their cooking resistance was observed. LDPE was not resistant to cooking.
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