There are nine basic performance requirements for plastic film appearance, specifications and deviation, transparency and gloss. You can learn one by one through this article.
The surface of the plastic film should be smooth and smooth, wrinkle-free or only a small amount of active pleats, no obvious irregularities, black spots, impurities, crystal points and stiff spots, no streaks, spots, gluten, etc., no bubbles, needles Holes and cracks, the aluminized layer of the aluminized film should be uniform, and no obvious bright strips, yin and yang surfaces are allowed. In addition, the surface of the film is required to be clean and free from dust and oil.
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 is small, and the deviation distribution is relatively uniform. In addition, the thickness of the aluminized layer of the aluminized film should also meet the requirements.
- Transparency and gloss
For transparent plastic films, the light transmittance is required to be higher, generally more than 92%. For opaque plastic films, such as white film, it is required to have high whiteness and good opacity. In addition, the plastic film should also have good gloss.
4, physical and mechanical properties
The physical and mechanical properties of the plastic film mainly include tensile strength, elongation at break, tear strength, impact strength, etc. In addition, the firmness of the aluminized layer on the aluminized film should also meet the requirements.
5, moisture permeability
Indicates the amount of water vapor permeated by a plastic film material under certain conditions, such as water vapor per square meter of a plastic film having a thickness of 25 μm within 24 h at a relative humidity of 90% and a temperature of 30 ° C. Quality, which to some extent represents the moisture resistance of the film material, the moisture permeability of various film materials is different, which also determines its application range.
6, oxygen permeability
Indicates the amount of oxygen permeated by the plastic film material under certain conditions, such as the relative humidity of 90% and the temperature of 23 ° C. The volume of oxygen per square meter of the plastic film with a thickness of 25 μm within 24 h. . The oxygen permeability of various film materials also varies.
7, geometric dimensional stability
Plastic film must have certain geometric dimensional stability. Otherwise, its expansion ratio is too large. It is easy to produce telescopic deformation due to mechanical force or heat during printing and compounding process, which not only affects the overprinting accuracy, but also wrinkles. Problems such as curling seriously affect product quality and production efficiency.
8, chemical stability
Plastic films are exposed to inks, adhesives, and certain organic solvents during printing and lamination. These are chemicals. Therefore, plastic films must have some resistance to the chemicals they are exposed to, so that they are not affected by them. influences.
9, surface tension
For example, the surface tension of the biaxially oriented polypropylene film and the low density polyethylene film is required to be 3.8×10-2 N/m or more, and the surface tension of the nylon film, the polyester film, and the polyester aluminized film also has corresponding indexes. In general, plastic films must be surface treated to improve surface tension before printing or compounding, and can be smoothly printed and composited.
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