|Plastic films are the most widely used in the packaging field. Plastic film can be used for food packaging, electrical product packaging, daily necessities packaging, clothing packaging, and the like. They have one thing in common, that is, the plastic film should be color-printed, and as a food package, it is also required to perform multi-layer composite or vacuum aluminum plating. Therefore, the plastic film is required to have a high free energy and a large wet tension to facilitate the strong adhesion of the printing ink, the adhesive or the aluminized layer to the plastic film; in the production process of the plastic film winding and high-speed packaging, The surface of the film is required to have a certain frictional property to prevent the film from sticking or slipping; when used for packaging of electrical appliances and electronic products, the film is required to have certain antistatic properties and the like.|
The surface tension of a plastic film depends on the free energy of the surface of the plastic film, which in turn depends on the molecular structure of the film material itself. Most plastic films, such as polyolefin films, are non-polar polymers with low surface free energy and low surface wet tension, typically around 30 dynes/cm. In theory, if the surface tension of the object is less than 33 dynes/cm, ordinary inks or adhesives cannot adhere firmly, so the surface must be treated. Polyester is a polar polymer with a high surface free energy and a surface wet tension of 40 dynes/cm or more. However, for high-speed color printing or to increase the adhesion between the vacuum aluminum-plated layer and the surface of the BOPET film, it is also necessary to surface-treat the BOPET film to further increase the surface wet tension.