Prediction and experimental verification of bubble and processing characteristics in blown-film extrusion

Blown-film modeling is useful to the flexible packaging industry for predicting process and bubble characteristics, such as freeze line height (FLH), bubble diameter, and film thickness. The use of a suitable rheological equation to describe material properties is critical in simulating the blown-film process. In this article, we present an improved rheological constitutive equation, which incorporates more realistic parameters of stress and deformation properties of the materials by combining the Hookean model with the Phan-Thien Tanner (PTT) model. The proposed PTT¿Hookean model is aimed at enhancing the viscoelastic behavior of the melt during biaxial stretching in the blown-film extrusion. Predictions of the blown-film bubble characteristics and FLH obtained with the PTT¿Hookean model agreed well with the experimental data of this study and previous studies with different materials and different die geometries. The justification for combining the Hookean model with the PTT model in the blown-film process is also reported here.