Numerical Modelling and Experimental Verification of Blown Film Processing
sani muke, Howard Connell, Igor Sbarski, Sati N. Bhattacharya
Note Printing Australia
Australia

Keywords: model, film, rheology

---

A non-isothermal viscoelastic Kelvin model was developed to simulate the film blowing process. Simulations were also performed using a commercial software package, B-Filmcad, which is based on a non-isothermal Newtonian fluid. Predictions of processing characteristics, such as bubble diameter, film thickness and strain rate profiles were compared to the actual experimental film blowing behavior of polypropylene (PP) in the stable operating window. Good agreement for the B-Filmcad predictions was limited to bubble diameter profile. By incorporating the polymers elasticity, using the Kelvin model, predictions were found to significantly improve. The reasonably good agreement between the theoretical predictions from the non-isothermal Kelvin model and actual experimental data may be due to the relatively small strains and strain rates used in the film blowing conditions in this work. Temperature was found to be the most critical parameter which influenced the film blowing characteristics of PP. A correct estimate of the relaxation time of the polymer is particularly important in giving a reasonably accurate fit with the experimentally observed processing behaviour of the polymer. Bubble stability measurements were also performed for PP and it was found that a stable operating window increased up to a frost line height of 210mm.