Analysis of Temperature Fields in Film Casting

Film casting extrusions were performed on polyethylene terephthalate) (PET) and polypropylene (PP) in a laboratory plant to evaluate the development of temperature profiles in the region from die to chill roll. This was done under different conditions of mass rate, drawing, and cooling. Thermal exchange of the film was evaluated by making use of an infrared thermography apparatus, which provides a bidimentional map of temperature profile for each testing condition. The different melt viscosity of the various polymers lead to more developed or less developed edge-beads. Therefore, at fixed working conditions, the resulting shapes of the temperature profiles and border effects differ for PET and PP. In particular, the temperatures in the transverse direction changed significantly from the edge to the center of the film, as shown in the thermographs. The thermal-fluid-dynamics behavior of polymeric-cast film during processing is discussed.