Food packaging manufacturer: what are the basic performance requirements of plastic film material?

Packing: packed in plastic film material what are the basic performance requirements? Appearance: the surface of the plastic film should level off is smooth, no wrinkles or only a small number of pleats, no obvious uneven, black, impurities, crystal point and rigid block, no stripes, spot mark, critical reinforcement and other ills, no bubble, pinhole and rupture, aluminum plating film of aluminized layer should be uniform, there is no obvious light article, the phenomenon such as surface of Yin and Yang, in addition, also calls for thin film surface is clean, no dust ash method, oil, etc. Specifications and deviation: the width of the plastic film, thickness and deviation shall conform to the requirements, and shall be uniform thickness, transverse, longitudinal thickness deviation is small, and deviation distribution more uniform, in addition, aluminum plating film also should comply with the requirements of aluminized layer. Transparency and glossiness: for transparent plastic film, the requirements of the light transmittance is higher, the general should reach more than 92%, and for not transparent plastic film, such as white film, insist on the white degree is high. Opacity is good, in addition, the plastic film should also have good gloss. Physical and mechanical properties, physical and mechanical properties of the plastic film mainly include tensile strength, elongation at break, tear strength, impact strength, etc. , in addition, aluminum plating film on aluminum plating layer fastness should also conform to the requirements. Through humidity: surface plastic material under certain conditions through the amount of water vapor in relative humidity is 90%, for example, under the condition of temperature of 30 degrees, 25 um thickness of plastic film in 24 hours per square meter through the water quality of the solar terms, from a certain extent, it represents the moisture resistance of membrane material, all kinds of thin film materials through humidity is different, it also determines the scope of its application. Oxygen permeability: plastic material under certain conditions through the amount of oxygen in relative humidity is 90%, for example, under the condition of temperature of 23 degrees, 25 um thickness of plastic film in 24 hours per square meter of oxygen through the volume, all kinds of thin film materials of oxygen permeability is also different. Geometric dimension stability: plastic film must have certain geometric dimension stability, otherwise, its scale is too big, in the process of printing and composite by mechanical force or by heat effect is easy to produce telescopic deformation, not only affects the overprint precision, also can appear folds, curly, seriously affect the product quality and production efficiency. Chemical stability: plastic film in the process of printing and composite to contact printing ink, adhesive, and some organic solvent, these are all chemicals, as a result, plastic films are exposed to these chemicals must be have a certain resistance to resistance, so that is not affected by it. Surface tension, such as two-way stretch polypropylene film and the surface tension of the low density polyethylene film requirements to 3. 8 * 10 - More than 2 n/M, nylon membrane, the surface tension of the polyester and polyester aluminum plating film also has the corresponding indicators, in general, plastic film before printing or compound must be after surface treatment to improve its surface tension, and able to smoothly and composite printing.