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【期刊论文】A Rheological Model for Polymer Melts with Internal Structure in Flow Fields*
周持兴, ZHOU Chixing
,-0001,():
-1年11月30日
Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.
Polymer melts,, Rheological model,, Polymer conformation,, Flow fields
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周持兴, WEI YU, CHIXING ZHOU, TAKASHI INOUE
Journal of Polymer Science: Part B: Polymer Physics, Vol. 38, 2378-2389 (2000),-0001,():
-1年11月30日
A coalescence mechanism for the coarsening behavior of polymer blends during a quiescent annealing process is proposed. It suggests that the distribution state of dispersed particles in a matrix obeys a nearest-neighbor distribution function in multibody systems. Both drainage and merge stages are included in the coalescence. All existing forces, such as thermal agitation, van der Waals attraction, interfacial tension, and viscous resistance, take control of the coarsening process. A dynamic equation is used to compute the evolution of dispersed particles. An experimental investigation has been made with the time-resolved light scattering measurement of a polystyrene/ poly(methyl methacrylate) blend during an annealing process. The model predictions are in good agreement with our experiment and other authors' work. The relative effects of system parameters such as volume fraction, interfacial tension, and viscosity are also discussed.
polymer blends, coalescence, annealing, monodisperse
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【期刊论文】Postfilling Analysis of Viscoelastic Polymers With Internal Structure Parameter
周持兴, XlAHONG HUANG and CHIXlNG ZHOU
POLYMER ENGINEERING AND SCIENCE, NOVEMBER 1999, Vol. 39, No.11,-0001,():
-1年11月30日
A new constitutive model with internal structure parameter is presented in this study for simulating orientation and deformation of polymer chain in the post/filing stages of injection molding process. Implementation of such a model is based on a hybrid finite-element/finite-difference numerical solution of the generalized Hele-Shaw flow. The simulation of a compressible viscoelastic fluid under nonisothermal conditions has not yet been discussed in most previous works. In addition to the distribution of pressure, temperature, density, and velocity, theoretical predictions also include shear and normal stresses, which can be used for subsequent calcula-tion of residual stresses. An amorphous material, namely a commercial-grade poly-styrene (PS), was used in the present work. Good agreement is obtained between the simulation and experimental pressure trace from this study.
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【期刊论文】DIGITAL ANALYSIS TECHNOLOGY FOR MORPHOLOGY OF POLYMER CHAIN COILS IN FLOW FIELDS*
周持兴, Chi-xing Zhou**, Hong Zheng and Wei Yu, Ji-feng Yao and Yu-cheng Li
Chinese Journal of Polymer Science Vol. 23, No.1, (2005), 1−2,-0001,():
-1年11月30日
Polymer chain coils with entanglement is a crucial scale of structures in polymer materials since their relaxation times are matching practical processing times. Based on the phenomenological model of polymer chain coils and a new finite element approach, we have worked out a computer software including solver, pre and post processing modules, and developed a digital analysis technology for the morphology of polymer chain coils in flow fields (DAMPC). Using this technology we may simulate the morphology development of chain coils in various flow fields, such as simple shear flow, elongational flow, and any complex flow at transient or steady state. The applications done up to now show that the software predictions are comparable with experimental results.
Morphology of polymer chain,, Complex flows,, Conformation tensor,, Finite element method (, FEM), ,, software DAMPC
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【期刊论文】Theory for drop deformation in viscoelastic systems
周持兴, Wei Yu, Mosto Bousmina a), Chixing Zhou, Charles L. Tucker III
J. Rheol. 48 (2), 417-438 March/April (2004),-0001,():
-1年11月30日
The deformation of a viscoelastic drop suspended in a homogeneous viscoelastic matrix is investigated. The drop and the matrix fluids are assumed to obey linear viscoelastic constitutive equations. Small-deformation analysis is carried out on the basis of the general solution for creeping flow around a spherical drop. The corresponding stress is calculated by extending Batchelor's approach to viscoelastic media for both small and large deformations. Good agreement was found between the model predictions and experimental results available in the literature.
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