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Experimental Investigation of Film Formation: Film Casting

In film casting, a polymer melt is extruded through a flat die before rapid cooling on a chill roll. In this article, the effects of process conditions on polypropylene (PP) film formation in the air gap have been studied. Process variables investigated include draw ratio (DR) and die temperature. The temperature, width, and velocity profiles in the air gap are measured. Centerline strain rates initially increase with distance from the die, and the trends observed depend on the DR. The velocity decreases from the centerline value as the film approaches the film edges. The film temperature shows a local minimum along the centerline.