Corona treatment method, chemical treatment method, mechanical deburring method, coating method, etc. are the methods of surface treatment of plastic films. The most commonly used method is corona treatment.
The surface energy of the plastic film determines the surface tension of the plastic film, and the molecular structure of the film material itself determines the surface energy of the film. Most plastic films such as polyolefin films (LDPE, HDPE, LLDPE, PP) are non-polar polymers,
The surface free energy is small, and the surface wet tension is low, generally about 30 dynes/cm. Theoretically, if the surface tension of an object is lower than 33 dynes/cm, ordinary ink or adhesive cannot be firmly attached, so its surface must be treated. Polyester
Types (PET, PBT, PEN, PETG) are polar polymers with high surface free energy and surface wet tension above 40 dynes/cm. But for high-speed color printing or to increase the bonding between the vacuum aluminum coating and the surface of the BOPET film
Force, also need to surface treatment of BOPET film to further increase its surface wet tension.
The basic principle of the corona treatment method is: by applying a high-frequency, high-voltage power supply between the metal electrode and the corona treatment roller (usually a high-temperature, ozone-resistant, high-insulation silicone rubber roller) to cause it to discharge, so that Air ionizes and forms a lot of odor
oxygen. At the same time, high-energy sparks hit the film surface. Under their combined action, the surface of the plastic film is activated and the surface energy is increased. Corona treatment can increase the wet tension of polyolefin film to 38 dynes/cm;
The surface wet tension reaches above 52-56 dynes/cm. The amount of wet tension on the surface of the corona-treated plastic film is related to factors such as the voltage applied to the electrode and the distance between the electrode and the corona-treated roller. Of course, the corona treatment should be moderate, not
The higher the corona treatment strength, the better. It is worth noting here that air should be avoided between the plastic film and the corona treatment roller, otherwise the reverse side of the film may also be corona treated. The consequences of the corona on the reverse side are: 1 There may be ink printing
The phenomenon of anti-sticking; 2 Aluminium layer transfer will occur when aluminizing, and glue layer transfer will occur when applying glue. The main measure to prevent corona on the reverse side of the film is to adjust the pressure of the rubber pressure roller before the corona treatment roller. The pressure on both ends of the pressure roller must be consistent and
The pressure should be appropriate. In addition, the corona roller and the pressure roller must undergo a strict dynamic and static balance test, and the radial runout requirement is less than 0.05 mm. The purpose is to ensure that the plastic film enters the corona roller smoothly and prevents air from being trapped, thereby avoiding the occurrence of reverse side
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