There are many methods for forming plastic films, among which casting, extrusion, and blow molding are more common:

Casting method: producing a non stretched and non oriented flat extruded film through the melt flow quenching process. The thin film produced by this process does not have a clear orientation structure.

Extrusion method: Common methods include uniaxial stretching and biaxial stretching.

The basic principle of biaxial stretching: High polymer raw materials are first heated and melted by an extruder to extrude into thick sheets. Then, within an appropriate temperature range above the glass transition temperature and below the melting point, they are stretched by a certain multiple along the longitudinal and transverse directions by a stretching machine, so that the molecular chains are oriented and arranged in an orderly manner on a plane parallel to the film. Then, they are heat set under tension to fix the oriented macromolecular structure, and finally cooled and processed into a film.

Blow molding method: It is usually manufactured by extrusion blow molding method, where the material is plasticized and extruded to form a tube blank that is blown and formed, and then cooled, pulled, and coiled. Blow molded film has orientation. Blow molding film forming process is simple and is a commonly used film forming process.