Thick films are produced by flat extrusion in the same way as plates, while thin films are produced as blow-extrusion films only. In blow extrusion, the thermoplastic film is extruded over a core with a blow nozzle. Air is blown through the die to inflate the extruded film to form the tube. The plastic is cooled down in the inflated tube and only wound up over rollers after it has cooled down. The surface properties of this film can be significantly improved by activation and treatment with plasma. deutlich verbessert werden.