Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 14 of 14 for “"elongational flow"”.
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Behavior of Polymer Solutions and Melts in Shearing and Elongational Flow Using Streak Photography and Birefringence
… (polyacrylamide solution) fluid undergoing flow past a radially oriented cylinder in both a converging and uniform flow field. The glycerin and polyacrylamide solutions are found to follow Newtonian and power law behavior, respectively, in Poiseuille flow between parallel plates and the …
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The rheology and structure of thermotropic liquid crystalline polymers in extensional flow
The transient shear and elongational flow behavior of HPC EF, G, and HBA/HNA (Vectra A900) have been measured in order to determine the behavior of liquid crystalline polymer systems and to establish whether this behavior is different from that for isotropic flexible-chain polymer melts and …
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Spinning of synthetic spider silk-like fibers and ex vivo rheology of spider silk
… insight was gained on how solvent removal during elongational flow (while the fiber is on the spin line) affects mechanical properties. In order to determine solvent evaporation from the fiber during spinning, the dependence of the solvent diffusion coefficient on solvent concentration had to be …
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A study of flow-induced crystallization in two-phase polymer melts
The effects of shearing and elongational flows on flow induced crystallization in polymer melts were investigated for the two-phase system of high molecular weight polyethylene suspended in a linear low density polyethylene carrier phase. Shearing flow was produced by a counter-rotating couette …
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An experimental and theoretical investigation of the rheological properties and degradation of mucin solutions : (or why saliva becomes watery when removed from your mouth)
… simulate the behaviour of saliva during simple elongational flow and account for the decrease in viscoelasticity with time. The first model considered is the FENEP model of a fluid, which is particularly suitable for describing the rheology of dilute polymer solutions (Newtonian solvents …
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Brownian dynamics simulations of fine-scale molecular models
… of the molecular configurations in various flow situations. To obtain this information about molecular configurations and orientations, a micromechanical representation of a polymer molecule must be proposed. A micromechanical model may be fine scale, such as the Kramers chain model, which …
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Polyethylene-montmorillonite nanocomposites
… with a patented mixing device to provide elongational flow. Wide angle X-ray diffraction was used together with transmission electron microscopy to evaluate the particle dispersion, which consisted of intercalated clay organised in clusters up to one micron in diameter.<br/><br/>The …
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An experimental and numerical analysis of the exit flow in a slit die for polymer melts
A slit die has been constructed to use both flow birefringence and direct pressure measurements to study the extrapolated exit pressure (Px) and the exit pressure theory used to evaluate the magnitude of the primary normal stress difference (N1) from the value of the exit pressure. Flow …
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Rheological characterization of polymers via dissipative particle dynamics
… a number of workers have used DPD to study the flow of polymer solutions in various geometries such as microchannels, pores, and sudden contractions. While these types of flows are well-suited to DPD's relative strengths, an important step has been skipped. Before the results of these complex …
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Polymer architecture effects on mechanochemical reactions
… a unique ability to become highly extended in elongational flow fields. The forces developed along the backbone give rise to scission of the chains near their center. Recently, this unique property of polymers has been adopted to explore new chemical transformations by embedding structural …
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The processing of microcomposites based on polypropylene and two thermotropic liquid crystalline polymers in injection molding, sheet extrusion, and extrusion blow molding
… in which the TLCP fibrils are generated in elongational flow fields that occur during processing. In situ composites usually exhibit highly anisotropic mechanical properties and the properties do not reflect the full reinforcing potential of the TLCP fibers. Factors considered include the …
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Finite element simulation of viscoelastic flow: effect of the rheological model and the mesh
The numerical simulation of viscoelastic flows was studied in this work. In particular the effect of mesh refinement on the quality and the convergence of the finite element method was examined, as well as the differences that may be found by using several rheological models to describe the …
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Flow Behavior of Granular Soil and Impounded Fly Ash Slurries
… impoundments typically results in a fast-moving flow of toxic waste that can carry for several miles with disastrous consequence. The most recent catastrophic tailing-dam failure took place on 25 January 2019, at Brumadinho, Brazil, where the resultant tailings flow killed at least 232 people. A …
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Processing-driven structuring of melt compounded polymer-based systems
L'abstract è presente nell'allegato / the abstract is in the attachment