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The three-dimensional flow of Non-Newtonian polymer melts in coextrusion dies was analyzed based on finite element simulations. The analysis considered the slip both die wall-polymer and polymer-polymer interface. The slip boundary condition is founded based on the Generalized Navier slippage model. The effects of die wall roughness on the interface were examined farther. It is found that decreasing the roughness of the fluid path can make the velocity field more uniform and the interfacial offset less. If consider the interface alip of two melts, the homologous of interface-slip coefficient and die-wall slip coefficient may ensure the stabilization of the interface. [ABSTRACT FROM AUTHOR]

The three-dimensional flow of non-Newtonian polymer melts in coextrusion dies was analyzed based on finite element simulations. Simulation results, especially the interface predictions were discussed. The effects of flow rate ratio and the roughness of die wall on the interface were examined farther. It is found that the flow rate affects the shape and location of the interface notably. The velocity of fluid flow mainly controls the shape and location of the interface. Increasing that the higher slipperiness of the fluid path can make the velocity field more uniform and the interfacial offset less. [ABSTRACT FROM AUTHOR]

The three-dimensional, nonisothermal, generalized Newtonian polymeric fluid flow (LPDE/PS) in coextrusion dies was simulated using the finite element method with evolutionary technique. Simulation results, especially the interface predictions, velocity profiles, and temperature profiles were discussed. The simulated interface shape was compared with that obtained by the previous researchers, and the simulated results were confirmed. The effects of fluids' temperature and flow rate ratio on the interface of LDPE/PS are further examined. Increasing temperature of more viscous fluid (PS) can influence the interface location. It is also found that the flow rate affects the shape and location of the interface notably. The velocity of fluid flow mainly controls the shape and location of the interface. [ABSTRACT FROM AUTHOR]

The effect of 975 W microwave irradiation on the crystalline structure of isotactic polypropylene (iPP) surface layer in Al/iPP/Al composite was studied by attenuated total reflection Fourier transform infrared (FTIR) and asymmetry diffraction geometry small-angle x-ray diffraction (XRD). The results show that after about 60 min irradiation, the orientated structure and crystallinity of the iPP surface layer are dropped, crystal transformation (α → β) happens. The iterative peak-fit of XRD curves indicates that the reasons for crystal transformations are: the microwave effect causes the increase of the order level of the crystal lattice, the defaults within the β-crystals are, thus, reduced. D[300] (stands for β-form phase) becomes larger, β-form iPP becomes more perfect. With microscopic distortion coefficient ε[300] and the microscopic stress of β-form becomes less attraction, the microscopic stress of the α-form goes up. This crystal transformation is useful for improving the toughness of iPP in electromagnetic shielding materials. [ABSTRACT FROM AUTHOR]