Investigation of the Rheological Behaviors of Polymeric Materials in the Film Casting Process through Multiscale Modeling and Simulation Method

Polymeric materials show the features of different lengths and time scales. In order to achieve optimized applications in practical forming process, it is of significance to understand the evolution of integrated structure-property relationship. In the study, the rheological behaviors of polymeric materials in film casting process are investigated by means of a multiscale modeling and simulation method based on the coarse-grained molecular dynamic (CGMD) method, the primitive path analysis, and the finite element method. The macroscopic properties of the polymeric system are predicted from the microstructure by using a bottom-up method. Based on the entanglement network of macromolecular chains predicted with CGMD simulation, the primitive path analysis method is adopted to evaluate main conformational parameters according to the tube theory, which realizes a bridge from nano to micro scale. The viscoelastic properties of polymeric materials are characterized by using a continuum Phan-Thien-Tanner (PTT) constitutive model, whose rheological parameters are obtained by fitting the distributions of material functions predicted from the tube model. The mathematical model of film casting process is further established based on a membrane model and the corresponding finite element model and details of numerical schemes are introduced. The characteristics of macroscopic rheological behaviors of polymeric melts can hence be investigated from the evolution of microscopic structure, and the phenomena in practical film casting process like the neck-in and the edge bead defects in engineering are successfully predicted.