A Theoretical Study on Transitional Shear Flow Behavior of the Compressible and Isothermal Thermoplastic Polymer

By extending the virtual conformational element of the polymer chain, a dynamic end-to-end (ETE) vector was presented to describe the chain’s instantaneous morphology based on the spring-bead theory. A feasible viscoelastic model was proposed to describe the rheological behavior of the isothermal thermoplastic polymer materials, based on the molecular kinetics, thermodynamics, and continuum mechanics method. The model is simplified as the generalized Newton’s law. Its integral formula with similar form to the KBKZ model was also derived. Rheological experiments were carried out with the isotactic polypropylene material. The experimental results reveal that the viscoelastic model exhibits a three-stage rheological characteristic. There is a distinct high-elastic rheological region in the middle stage, reflecting the pseudoplastic fluids properties. Compared with the Ostwald-de Waele power law model, the viscoelastic model shows a better agreement with the rheological practices.