Steady-state modeling of extrusion cast film process, neck-in phenomenon, and related experimental research: A review

This review provides the current state of knowledge of steady-state modeling of the extrusion cast film process used to produce flat polymer films, as well as related experimental research with a particular focus on the flow instability neck-in. All kinematic models used (i.e., 1-, 1.5-, 2-, and 3-dimensional models) together with the utilized constitutive equations, boundary conditions, simplified assumptions, and numerical methods are carefully summarized. The effect of draw ratio, Deborah number (i.e., melt relaxation time related to experimental time), film cooling, second to first normal stress difference ratio at the die exit, uniaxial extensional strain hardening, and planar-to-uniaxial extensional viscosity ratio on the neck-in is discussed.