Film casting of polyethylene terephthalate: Experiments and model comparisons

Cast film extrusions were carried out on polyethylene terephthalate (PET), on a laboratory line. The thermal and the geometrical behavior of the film, in the region from die to chill roll, was studied in different working con ditions. The experimental evaluations were performed with an Infrared Therm ography (I.R.T.) apparatus. Simplified modeling, describing the non-isother mal behavior of the web, was used to predict temperature, width and thickne ss of the film in machine direction (MD) as a function of the distance from the die. The above-calculated profiles were compared to those obtained by experimental thermography maps. Measured temperatures resulted different be tween edge and center of film, i.e. transverse direction (TD) temperature p rofiles were highlighted. On the contrary, model temperatures are assumed v arying only along the machine direction (MD) of web. Thus, from the compari son between experimental and theoretical results, an acceptable agreement w as found only in some cases.