The extrusion molding of the original film in the production of packaging film can be achieved by either the casting method or the extrusion blow molding traction stretching method. The film formed after thin (sheet) drawing has good twisting property, so this kind of unidirectional polypropylene film is widely used in the packaging of candy bars, Dim sum, etc.
Polypropylene sheets are formed by casting or traction extrusion, and unidirectional stretching is used for production.
The longitudinal (unidirectional) stretching of the membrane is to extrude the molten film blank from the T-shaped mold on the extruder, which is cooled and shaped by the cooling and shaping roller, and then re preheated by the drawing roller, relying on the rotational speed between the rollers.
