The nine basic performance requirements of plastic film, see which ones you usually ignore?
The surface of the plastic film should be flat and smooth, with no wrinkles or only a few live folds, no obvious unevenness, black spots, impurities, crystal spots and rigid blocks, no streaks, spots, violent tendons, etc., no bubbles, needles, etc. For holes and cracks, the aluminized layer of the aluminized film should be uniform, and no obvious bright stripes, yin and yang surfaces, etc. are allowed. In addition, the surface of the film is required to be clean and free of dust, oil, etc.
2. Specifications and deviations
The width, thickness and deviation of the plastic film should meet the requirements, and the thickness should be uniform, the thickness deviation in the horizontal and vertical directions should be small, and the deviation distribution should be relatively uniform. In addition, the thickness of the aluminized layer of the aluminized film should also meet the requirements.
3. Transparency and gloss
For transparent plastic films, the light transmittance is required to be higher, which should generally reach 92% or more. For opaque plastic films, such as white film, high whiteness and good opacity are required. In addition, the plastic film should also have good gloss.
4. Physical and mechanical properties
The physical and mechanical properties of plastic films mainly include tensile strength, elongation at break, tear strength, impact strength, etc. In addition, the firmness of the aluminum coating on the aluminum coating should also meet the requirements.
5. Moisture permeability
Indicates the amount of water vapor transmitted by the plastic film material under certain conditions. For example, at a relative humidity of 90% and a temperature of 30°C, the water vapor per square meter of a plastic film with a thickness of 25um in 24 hours Quality, it represents the moisture resistance of the film material to a certain extent. The moisture permeability of various film materials is different, which also determines its application range.
6. Oxygen permeability
Indicates the oxygen permeability of plastic film material under certain conditions, such as the volume of oxygen per square meter per square meter of plastic film with a thickness of 25um in 24 hours at a relative humidity of 90% and a temperature of 23°C . The oxygen permeability of various film materials is also different.
7. Geometric dimensional stability
The plastic film must have a certain degree of geometrical stability, otherwise, its expansion rate is too large, and it is easy to produce expansion and contraction under the action of mechanical force or heat during the printing and lamination process. Problems such as curling seriously affect product quality and production efficiency.
8. Chemical stability
Plastic film is exposed to inks, adhesives and certain organic solvents in the printing and laminating process. These are all chemical substances. Therefore, plastic films must have certain resistance to these chemical substances in contact with them, so as to avoid them. influences.
9. Surface tension
For example, the surface tension of biaxially oriented polypropylene film and low-density polyethylene film is required to reach 3.8×10-2N/m or more. The surface tension of nylon film, polyester film and polyester aluminized film also have corresponding indicators. Generally speaking, plastic films must undergo surface treatment before printing or laminating to increase their surface tension, and printing and laminating can be carried out smoothly.