Abstract: The objective is to develop theoretical flow-induced orientation stress-strain relationship models for entangled polymer melt during injection molding process with the isothermal compressible hypothesis. In view of the trackless deformation characteristics of polymer entanglement macromolecular chain, the end-to-end distance vector(ETEV) is used to describe the evolution of the macromolecular chain morphology during the filling stage based on some reasonable simplified hypothesis, as the core of the flow-induced deformation physical model. Coupled with the irreversible thermodynamics and statistical mechanics theory, the flow-induced orientation stress-strain model of the molecular chain monomer is conducted. The relationship between equivalent volume ratio and Finger strain tensor C–1 is also derived, and the corresponding pseudo-high-elastic mathematical model of entangled polymer melt is calculated. The correlation between the micro orientation stretching ratio and the deformation history is further elucidated, then the nonlinear orientation stress-strain model is deduced. And the pseudo-high-elastic integral model similar with the classic K-BKZ model is obtained. The structure feature and curve tendency of instantaneous model is demonstrated. Results indicate that the theoretical model is reliable and scientific for description the orientation problem.

Key words: injection molding;isothermal compressible melt;flow-induced orientation;end-to-end distance vector;stress distribute;pseudo-high-elastic model