Study of wall slip in entangled polymer melts using stochastic simulation.
Item
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Title
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Study of wall slip in entangled polymer melts using stochastic simulation.
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Identifier
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AAI3231972
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identifier
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3231972
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Creator
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Xu, Fang.
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Contributor
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Adviser: Morton M. Denn
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Date
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2006
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Chemical
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Abstract
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We describe a full-chain stochastic tube model for entangled melts and solutions of linear polymers. The model incorporates two forces that result from chain confinement: a tensile force along the chain that prevents chain collapse and a transverse force that keeps the chain within the virtual tube. The model tracks conjugate constraint pairs and utilizes a consistent approach to constraint release and renewal. Chain loops within the tube are permitted. A single time-scaling adjustable parameter is required. Model predictions are compared with published transient and steady-state data on two entangled polystyrene solutions.;The stochastic chain model described above provides fundamental insight into the mechanism of apparent wall slip in entangled polymer melts. Apparent slip is a shown to be a consequence of a rapid decrease in the entanglement density for chains in the region of the wall. There is good agreement between model predictions and polydimethylsiloxane experiments of Durliat et al. (1997) in which a surface layer containing a known density of tethered chains contacts a bulk melt. The model cannot provide quantitative information about apparent slip when chains are simply adsorbed at the wall, since the surface density and effective chain length are required inputs to the calculation, but it does agree in broad terms with experiments of Mhetar and Archer (1998a) on 1,4-polybutadiene.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
