Simulation of film blowing including flow-induced crystallization

The two-phase microstructural flow-induced crystallization model developed by the authors is applied to the simulation of film blowing. In order to is olate the effects due to crystallinity, a simplified "quasicylindrical" app roximation is used for the momentum equations, which neglects the effect of axial curvature in the axial direction. The present simulations include th e combined effects of flow-induced crystallization, viscoelasticity, and bu bble cooling. In all cases studied, the location of the frost line is predi cted naturally as a consequence of flow-induced crystallization. The effect s of inflation pressure, melt extrusion temperature, and take-up ratio on t he bubble shape are predicted to be in agreement with experimental observat ions. The combination of these processing conditions determines the shape o f the bubble, i.e., whether the bubble contracts or expands. An important f eature of our model is the prediction of the locked-in system stresses at t he frost line that are related to the physical and mechanical properties of the film. (C) 2001 The Society of Rheology.