What is the function of Polyolefin Film?
Polyolefin film made of polyvinyl chloride, polyethylene, polypropylene, polystyrene and other resins are used for packaging and as a coating layer. The share of plastic packaging and plastic packaging products in the market is increasing, especially composite plastic flexible packaging, has been widely used in food, medicine, chemical and other fields, and in which the largest proportion of food packaging, such as beverage packaging , frozen food packaging, cooking food packaging, fast food packaging, etc., these products have brought great convenience to people's lives.
|Polyolefin film is the most widely used in the packaging field. Polyolefin film can be used for food packaging, electrical product packaging, daily necessities packaging, garment packaging and so on. All of them have one thing in common: they need to carry out color printing on plastic films, and also perform multi-layer lamination or vacuum aluminum plating as a food packaging. Therefore, it is required that the free surface energy of the plastic film should be high and the wet tension should be large to facilitate the firm adhesion of the printing ink, adhesive, or aluminized layer to the plastic film; during the production of plastic film winding and high-speed packaging, It is required that the surface of the film have certain friction properties to prevent the film from sticking or slipping; when used in packaging for electrical appliances, electronic products, etc., the film is required to have certain anti-static properties and so on.|
The surface tension of the polyolefin film depends on the surface free energy of the polyolefin film, and the surface energy of the film depends on the molecular structure of the film material itself. Most plastic films such as polyolefin films (LDPE, HDPE, LLDPE, PP) are non-polar polymers, have a small surface free energy and a low surface wet tension, typically about 30 dyne/cm. In theory, if the surface tension of the object is lower than 33 dyne/cm, ordinary inks or adhesives cannot adhere firmly, so they must be treated on the surface. Polyesters (PET, PBT, PEN, PETG) are polar polymers with a high surface free energy and a surface wet tension of 40 dyne/cm or more. However, for high-speed color printing or for increasing the bonding force between the vacuum aluminizing layer and the BOPET film surface, it is also necessary to perform surface treatment on the BOPET film to further increase the surface wet tension.