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extensional flow OF BULK POLYMERS STUDIED BY DYNAMIC MONTE CARLO SIMULATIONS

Chinese Journal of Polymer Science 2013年第11期31卷 1463-1469页

作者： Yu Ma Xiao-hong Zhang 胡文兵 Department of Polymer Science and Engineering State Key Laboratory of Coordination ChemistrySchool of Chemistry and Chemical EngineeringNanjing University State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Donghua University Anhui Tong Feng Electronics Corporation

Dynamic Monte Carlo simulations of bulk lattice polymers driven through planar geometries with sequentially converging, parallel and diverging spaces between two neutrally repulsive solid plates are reported. The spatial profiles of polymer velocity and deformation along the course of such a laminar extensional flow have been carefully analyzed. The results appear consistent with experimental observations in literature. In the entrance and exit regions, a linear dependence of chain extension upon the excess velocity has been observed. Moreover, an annexed shear flow and a molecular-dispersion effect are found. The results demonstrate a useful strategy of this approach to study polymer flows and bring new insights into the non-Newtonian-fluid behaviors of bulk polymers in capillary rheometers and micro-fluidic devices.

关键词： Polymer deformation extensional flow Monte Carlo simulations.

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CONSTITUTIVE EQUATION OF CO-ROTATIONAL DERIVATIVE TYPE FOR ANISOTROPIC-VISCOELASTIC FLUID

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Acta Mechanica Sinica 2004年第1期20卷 46-53页

作者：韩式方 Res.Lab.of Non-Newtonian Fluid Mechanics Chengdu Institute of Computer ApplicationChinese Academy of SciencesChengdu 610041China

A constitutive equation theory of Oldroyd fluid B type,*** co-rotational derivative type,is developed for the anisotropic-viscoelastic fluid of liquid crystalline(LC)*** the influence of the orientational motion on the material behavior and neglecting the influence,the constitutive equation is applied to a simple case for the hydrodynamic motion when the orientational contribution is neglected in it and the anisotropic relaxation,retardation times and anisotropic viscosi- ties are introduced to describe the macroscopic behavior of the anisotropic LC polymer *** the equation for the shear flow of LC polymer fluid,the analytical expressions of the apparent viscosity and the normal stress differences are given which are in a good agreement with the experimental results of Baek et *** the fiber spinning flow of the fluid,the analytical expression of the extensional viscosity is given.

关键词： constitutive equation anisotropic-viscoelastic fluid liquid crystalline polymer nonNewtonian flow co-rotational derivative anisotropic material functions shear flow extensional flow

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The Effect of Orientation Relaxation on Polymer Melt Crystallization Studied by Monte Carlo Simulations

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Chinese Physics Letters 2009年第7期26卷 222-225页

作者：王茂香 School of Science Nanjing University of Science and Technology Nanjing 210094

We use dynamic Monte Carlo simulations to study the athermal relaxation of bulk extended chains and the isothermal crystallization in intermediately relaxed melts. It is found that the memory of chain orientations in the melt can significantly enhance the crystallization rates. The crystal orientation and lamellar thickness essentially depend on the orientational relaxation. Moreover, there is a transition of the nucleation mechanism during the isothermal crystallization from the intermediately relaxed melts. These results explain the mechanism of the self-nucleation by orientation and suggest that in flow-induced polymer crystallization, the orientational relaxation of chains decides the crystal orientation.

关键词： STRAIN-INDUCED CRYSTALLIZATION MOLECULAR-DYNAMICS SIMULATION SHEAR-INDUCED CRYSTALLIZATION ISOTACTIC POLYPROPYLENE extensional flow POLY(ETHYLENE-TEREPHTHALATE) POLYETHYLENE PRECURSOR MEMORY MODEL

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