Computer simulation of the film blowing process incorporating crystallization and viscoelasticity

A comprehensive two-dimensional simulation of the film blowing process is developed based on a mathematical model that incorporates the Phan-Thien and Tanner (PTT) and the Neo-Hookean constitutive equations with crystallization effects. The PTT constitutive equation is employed in the liquid-like region, while the Neo-Hookean constitutive equation is employed in the solid-like region, to describe the rheological behavior of the film. The effects of the process variables and parameters on the stress balance and overall behavior of the film were evaluated. The orientation-induced crystallization is accounted for by incorporating the Nakamura non-isothermal equation along with the Ziabicki equation. The proposed model provides predictions of the bubble shape and dimensions, the position of the freeze-line, and the evolution of temperature, crystallinity, birefringence, stresses and deformation in the blown film. The predictions of the model show good agreement with experimental results reported by various workers.