Transient solutions of nonlinear dynamics in film blowing accompanied by flow-induced crystallization

The nonlinear dynamics in film blowing process is simulated employing the governing equations of the system that include the flow-induced crystallization (FIC), i.e., the continuity, the two force balances (axial and circumferential), the energy, the crystallinity, and the constitutive equations of Phan-Thien Tanner (PTT) model. Unlike the hitherto-published simulation results on film blowing, this study doesn't assume the boundary condition of the radius of the bubble at freezeline height having the zero slope with respect to the axial spatial coordinate. Instead, the governing equations of the system yield this important result as part of the solution of the set of the partial differential equations which are defined from the die exit all the way to the nip roll. The reason why the governing equations need to be solved to the nip roll beyond the freezeline height is that most of the crystallization occurs after the freezeline height and the deformation of the film also persists in the region. Transient solutions of the dynamics in film blowing have been obtained showing close agreement with the experimental results of polymers including LDPE. The instability behavior of the process, draw resonance, has also been portrayed using the FIC-included simulation model of this study, which exhibits better agreement with experiments than the previous model without FIC.