The Interaction of Crystallinity, Elastoplasticity, and a Two-Phase Model on Blown Film Bubble Shape

Abstract

Historically, simulations of the blown film process have been carried out only to the freeze line; a point which is often well below the actual frost line for the process. This limitation in previous simulations was discovered to be related to the interaction of the process boundary conditions with the rheological equation of state used in previous analyses to represent the stretching of the polymer film. A new approach has been developed that allows the process to be simulated to the real frost line. This has been accomplished by using a two-phase model incorporating viscoplasticity and crystallization of the polymer melt into the physical description of the blown film process. Prediction of the bubble shape, temperature, and velocity from the die to the frost line agree fairly well with experimental data. By improving the rheological models used in the simulation, this approach has the potential of being able to pre dict physical properties of polymeric film from molecular and process parameters.