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Stretch film tension

The surface tension of the stretched film depends on the surface free energy of the plastic film, and the surface energy of the stretched film depends on the molecular structure of the film material itself, so its surface tension has many factors:

1. Non-sexual polymers, the surface free energy of the stretched film is small, and the surface wet tension is low, generally about 30 dynes/cm. Theoretically, if the surface tension of the object is lower than 33 dynes/cm, ordinary inks or adhesives cannot be attached, so the surface is treated;

2. Polyesters (PET, PBT, PEN, PETG) are sex polymers with high surface free energy and surface wet tension above 40 dynes/cm. However, for high-speed color printing or to increase the bonding force between the vacuum aluminized layer and the surface of the BOPET film, the BOPET film also needs to be surface-treated to further its surface wet tension;

3. The transfer of the aluminized layer will occur when aluminized, and the transfer of the coated layer will occur when the glue is applied. The main measure to prevent corona on the reverse side of the film is to adjust the pressure of the rubber pinch roller in front of the corona treatment roll, and the pressure at both ends of the pinch roll should be consistent and appropriate.

When testing the surface tension of the stretch film, a strict dynamic and static balance test is carried out, and the radial runout is required to be less than 0.05 mm. The purpose is to ensure that the plastic film enters the corona roll smoothly and prevents air from being trapped, so as to avoid the phenomenon of reverse corona. .