The PTT and Giesekus models recommended for fiber spinning are also recommended for film casting. The Oldroyd-B model is another acceptable choice, especially for melts characterized by a significant strain hardening behavior. The DCPP model can also be used, especially if a qualitative description of the macromolecular behavior is required. The Leonov model, however, is not available for film casting applications. In addition, the simplified viscoelastic model is not suited for the simulation of film casting.

If no experimental data are available for the elongational viscosity, the nonlinear parameters should be fixed on the basis of known melt properties. Therefore, for a strain-thinning or weakly strain-hardening melt, high values for the nonlinear parameters are selected (typically for a PTT model or for a Giesekus model). For a strain-hardening melt, lower values should be used for the nonlinear parameters. If the DCPP model is used, a relatively large number of branches ( in Equation 6–49) should be considered for strain-hardening materials such as LDPE, while a unit or low number of branches should be selected for strain-thinning or weakly strain-hardening melts such as LLDPE.