Dissertations / Theses: 'Polymer fluid'

1

Elkovitch, Mark D. "Supercritical fluid assisted polymer blending /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488204276531724.

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2

Wood, Colin David. "Polymer synthesis using compressed fluid solvents." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272686.

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3

Shin, Y. Michael (Young-Moon Michael) 1969. "Formation of polymer nanofibers from electrified fluid jets." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8848.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000.
Includes bibliographical references (leaves 176-182).
The formation of polymer nanofibers from fluid jets in· an electric field, also referred to as electrospinning, has been studied. Controlling the fiber properties requires a detailed understanding of how a millimeter-diameter fluid jet emanating from a nozzle is transformed into solid fibers that are four orders of magnitude smaller in diameter. To this end, a fiber spinner operating under a uniform electric field and providing a controlled process environment was designed. In the conventional view of electrospinning, the mechanism leading to small fiber diameters has been attributed to the splaying phenomenon, in which a single jet splits into multiple smaller jets due to radial charge repulsion. Using high-speed photography and an aqueous solution of poly(ethylene oxide) as a model fluid, it was shown that the jet does not splay but instead undergoes a rapid whipping motion. The high whipping frequency created the optical artifact of multiple jets. The whipping jet was best observed in the onset region of the instability. Further downstream, the amplitude of the instability continued to grow, and the jet trajectory became more chaotic. This was verified through photography of the entire jet and close-up observations of representative regions further downstream. Based on these findings, an alternative mechanism for the formation of polymer nanofibers is proposed. It is conjectured that the whipping instability causes stretching and bending of the jet. The large reduction in jet diameter is achieved by increasing the path length over which the fluid jet is accelerated and stretched prior to solidification or deposition on a collector. Whipping induced stretching is conjectured to be the primary mechanism causing the jet diameter reduction. To provide a concise way of displaying the stability of electrified fluid jets as a function of the electric field and the flow rate, operating diagrams were developed. These diagrams delineate regions of different jet behavior, and the stability borders for two transitions have been mapped. The first transition is from dripping to a stable jet; and represents the suppression of the Rayleigh instability. For high conductivity fluids, an additional transition from a stable to a whipping jet can be observed at higher electric fields. The experimental findings are supported by a theoretical analysis of the jet thinning and the onset of the instability. To elucidate the fundamental electrohydrodynamics, glycerol was studied as a model fluid. Based on the experimental observation that whipping occurs on a length scale much larger than the jet radius, an asymptotic approximation of the electrohydrodynamic equations has been developed by Hohman and Brenner. This theory governs both long wavelength axisymmetric and non-axisymmetric distortions of the jet, and allows the jet stability to be evaluated as a function of all relevant fluid and process parameters. Three different instabilities are predicted: the classical Rayleigh instability, an axisymmetric conducting mode, and a non-axisymmetric conducting mode. The presence of these instabilities at various locations along the jet has been verified with high-speed video and photography. The particular instability that is observed depends on the jet shape and the surface charge density. To achieve quantitative agreement between experimental and theoretical jet profiles, the jet current and the local electric field in the vicinity of the nozzle had to be taken into account. The electric currents in stable jets were found to be linear in both the electric field and the flow rate Theoretical operating diagrams were developed based on the experimental insight that the instabilities are convective. The dependence of the stability borders on both the electric field and the flow rate is correctly reproduced by the Hohman-Brenner theory. This implies that operating diagrams have the potential to be used as predictive tools to better understand and control the process. The quantitative agreement between theory and experiments suggests that the fundamental process in electrospinning involves indeed a rapidly whipping jet, which is caused by the interaction of surface charges on the jet and the applied electric field. The notion of a whipping jet has also been extended to low viscosity fluids, where the jet disintegrates into fine droplets, i.e., electrospraying. For sufficiently large jet radii, experiments have verified the theoretical prediction that the dispersal of fluid results from the growth of a non-axisymmetric conducting mode along the jet, which subsequently breaks into droplets due to the axisymmetric conducting mode.
by Y. Michael Shin.
Ph.D.

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4

Harlen, Oliver Guy. "Strong flows of dilute polymer solutions." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358648.

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5

Harris, Owen John. "Unsteady flows of dilute polymer solutions." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319993.

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6

Taddese, Tseden. "Thermodynamics and dynamics of polymers at fluid interfaces." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/thermodynamics-and-dynamics-ofpolymers-at-fluid-interfaces(27166765-7d8b-405f-90d2-7f2489a200ca).html.

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The aim of this thesis is to study the structural and thermodynamical properties of polymers at liquid/liquid interfaces by means of multiscale molecular dynamics simulations. This thesis is presented in alternative format, and the results, consisting of three journal articles, are divided into two main parts. The first part of the thesis looks at the structural and dynamical changes as well as the thermodynamic stability of polymers of varying topology (linear and star-shaped) at interfaces by performing molecular dynamics simulations on model systems. It was found that homopolymers are attracted to the interface in both good and poor solvent conditions making them a surface active molecule, despite not being amphiphilic. In most cases changing polymer topology had only a minor effect on the desorption free energy. A noticeable dependence on polymer topology is only seen for relatively high molecular weight polymers at the interface. Examining separately the enthalpic and entropic components of the desorption free energy suggests that its largest contribution is the decrease in the interfacial free energy caused by the adsorption of the polymer at the interface. Furthermore, we propose a simple method to qualitatively predict the trend of the interfacial free energy as a function of the polymer molecular weight. In terms of the dynamics of a linear polymer, the scaling behaviour of the polymer confined between two liquids did not follow that predicted for polymers adsorbed onsolid or soft surfaces such as lipid bilayers. Additionally, the results show that in the diffusive regime the polymer behaves like in bulk solution following the Zimm model and with the hydrodynamic interactions dominating its dynamics. Further simulations carried out when the liquid interface is sandwiched between two solid walls show that when the confinement is a few times larger than the blob size the Rouse dynamics is recovered. The second part of the thesis focuses on optimizing the MARTINI coarse-grained (CG) Model, which retains certain chemical properties of molecules, to reproduce solubility of polymers, in specific polyethylene oxide (PEO), in both polar and non-polar solvents. Performing molecular dynamics simulations using this CG model will then enable us to study the properties PEO in octanol/water and hexane/water systems with increased length and timescales not accessible by atomistic simulations. The MARTINI CG method (Marrink et al., J. Phys. Chem. B, 2007, 111, 7812) is based on developing the optimal Lennard-Jones parameters to reproduce the partition free energy between water (polar solvent) and octanol (apolar solvent). Here we test the MARTINI CG method when modelling the partitioning properties of PEO, with increasing molecular weight between solvents of different polarity by comparing the results with atomistic simulation. We show that using simply the free energy of transfer from water to octanol to obtain the force parameters does not guarantee the transferability of the model to other solvents. Instead one needs to match the solvation (or hydration) free energies to ensure that the polymer has the correct polarity. We propose a simple method to select the Lennard-Jones parameter to match the solvation free energies for different beads. We also show that, even when the partition coefficient of the monomer is correct, even for modestly high molecular weight of the polymer the predicted partitioning properties could be wrong.

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7

Royer, Joseph Robert. "Supercritical Fluid Assisted Polymer Processing: Plasticization, Swelling and Rheology." NCSU, 2000. http://www.lib.ncsu.edu/theses/available/etd-20000810-144737.

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The use of supercritical carbon dioxide, scCO is a gas under atmospheric conditions, it can be used as a processing aid and then easily removed from a polymer through evaporation to obtain the original physical properties of the unplasticized polymer matrix. In addition, CO has been shown to be more environmentally friendly in comparison to many of the traditional organic plasticizers. However, the biggest challenge hindering the widespread use of CO as a plasticizer involves a lack of understanding of and data quantifying its effect on polymer swelling and the concomitant reduction in material viscosity. In this work, a three-step approach is used to investigate and quantify the physical phenomena associated with CO-induced plasticization of polymer melts.First, a novel experimental apparatus was designed and constructed to measure equilibrium swelling, swelling kinetics and diffusion of CO into a polymer melt. It was found that diffusion of CO pressure had a negligible effect on the diffusion coefficient; however, the system temperature directly affected the diffusion coefficient. Increased pressure was found to enhance the extent of swelling whereas a maximum was observed with increasing temperature, at pressures above 15 MPa. The Sanchez-Lacombe equation of state was found to be in good agreement with the experimentally calculated variables, and thus, can be used as a predictive tool to obtain physical properties of the CO-PDMS system.Secondly, a high pressure extrusion slit die rheometer was constructed to measure the viscosity of polymer melts plasticized with low concentrations of CO. Polystyrene, poly(methyl methacrylate), polypropylene, low density polyethylene, and poly(vinylidene fluoride) were all investigated. CO was found to be an efficient plasticizer for all of these polymer materials, generally lowering the viscosity of the melt 30-80%, depending on processing conditions. Predictive viscoelastic scaling models based on free-volume principles and a prediction of Tg depression from a diluent were developed to quantify the effects of CO concentration, pressure and temperature on viscosity. This unique free-volume approach allows the high pressure polymer/CO rheology to be predicted based solely on physical parameters of the polymer melt and CO solution behavior over the concentration and temperature ranges for which the models are valid.Finally, a novel high pressure magnetically levitated sphere rheometer (MLSR) was developed to further investigate the effects of CO on the viscosity of polymer melts. The MLSR measures the difference in magnetic intensity required to levitate a magnetic sphere in a sample fluid while the fluid is at rest and under shear. The observed change in magnetic intensity is directly proportional to the viscoelastic force imposed on the sphere by the surrounding fluid, and thus is used to calculate the fluid viscosity from a calibration of known viscosity standards. The rheometer eliminates many of the disadvantages associated with other high pressure rheometers and can operate over a wide range of CO concentrations at constant pressure with excellent reproducibility. This rheometer was used to measure the viscosity reduction of poly(dimethyl siloxane) by CO were investigated. The viscosity of the polymer melt could be lowered in excess of 97% of its original value at atmospheric pressure by adding a CO concentration of approximately 30 wt%. Additionally, experimental evidence revealed that the elevated pressure significantly increased the polymer/CO viscosity.

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8

Carlà, Vito <1978&gt. "Supercritical fluid polymer processing: anomalous sorption and dilation behaviour." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/613/.

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9

Wagner, Lukas. "Simulations of fluid and polymer dynamics with discrete methods /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487935125881663.

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10

Casiano, Matthew Joseph. "The investigation of flow within a polymer scaffold inside a perfused bioreactor." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20712.

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11

Kao, Hsien-Hsi. "Understanding the fluid phase equilibria and polydispersity in polymer systems." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516170.

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12

Zhou, Lucy Ying Jr. "Quantitative Analysis of Additives in Low Density Polyethylene Using On-line Supercritical Fluid Extraction /Supercritical Fluid Chromatography." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36786.

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Polymer additives exemplify many classes of compounds which possess a wide variety of chemical (i.e., phenols, amides, esters) and physical (i.e., volatility, solubility) properties. They are incorporated into polyolefins and other such polymeric materials for a number reasons: (a) to prevent degradation by ultraviolet light, heat, and oxygen; (b) to aid in the processing of the polymer; and (c) to modify the physical properties of the polymer. Since the purity and amount of additive can affect polymer properties, it is very important to characterize and quantify additives in polymer products. Traditional liquid solvent/polymer extraction methods, which involve dissolution/precipitation, are time-consuming, uneconomical, and the recoveries are significantly lower than 90%.

In recent years, analysis with supercritical fluids (SFs) has emerged as an alternative analytical technique because SFs afford higher diffusivity and lower viscosity. In this research, an on-line Supercritical Fluid Extraction (SFE)/Supercritical Fluid Chromatography (SFC) system was assembled to provide efficient extraction and separation of polymer additives with quantitative results. The effects of various SFE/SFC parameters, such as trapping temperature, injection temperature, extraction pressure and temperature, dynamic extraction time, and fluid flow rate on extraction and separation efficiencies of different additive standards (i.e., BHT, BHEB, Isonox 129, Irganox 1076 and Irganox 1010) were investigated. Optimized conditions were employed to quantitatively extract additives from LDPE. Identification of additives was performed by comparing the retention time with each additive standard. Results obtained from on-line SFE/SFC were compared to results from off-line SFE/High Performance Liquid Chromatography (HPLC) and off-line Enhanced Solvent Extraction (ESE)/HPLC.

Master of Science

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13

Vallabh, Rahul. "Modeling Tortuosity in Fibrous Porous Media using Computational Fluid Dynamics." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-08062009-153236/.

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Tortuosity factor is often used to characterize the structure of the pore volume in fibrous porous media. This work involves the determination of tortuosity using computational fluid dynamic (CFD) simulation and particle tracking analysis. A new method has been adopted to generate 3-D geometry for modeling fibrous porous structures using ANSYSÂ® Parametric Design Language (APDL). Computation fluid dynamics has been used to simulate permeability of modeled 3-D fiberweb structures. The simulated permeability results are in good agreement with the models proposed by other authors. The experimental results were found to be slightly higher compared to simulated results and existing models due to the layered configuration of the samples. Permeability is found to be significantly influenced by fiber diameter, and porosity as well as fiberweb thickness. The relationship between air permeability and fiberweb thickness has been used to develop an indirect method for determination of tortuosity factor. Tortuosity factor has also been determined using a more direct method involving CFD simulation and Particle Tracking analysis. Different models established using the direct and indirect methods of determination show that tortuosity is significantly influenced by porosity, fiber diameter and fiberweb thickness, whereas the models available in the literature express tortuosity as a function of porosity only.

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14

Yuan, Yanhui. "Specific interactions in polymer + CO₂ + cosolvent systems: experiment and modeling." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37139.

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Systems in which there are strong specific interactions between the polymer and CO₂ are of interest in a number of applications including polymer foaming, coating and impregnation. Unfortunately, experimental data on the phase behavior of such systems are relatively scarce, as are models that explicitly consider specific interactions in such systems. The overall goal of this work was therefore to develop a method for the measurement of specific interactions in polymer + CO₂ systems and to apply such measurements to the development of a thermodynamic model for polymer solutions. This work demonstrates that in situ ATR-FTIR spectroscopy may be used to quantify specific interactions in CO₂ + polymer- systems that incorporate carbonyl, ether, siloxane and sulfone groups. However, carbonyl stretching frequencies cannot be used to quantify such interactions between CO₂ and carbonyl polymers, contrary to what has been suggested in the literature. This is because blue shifts in the carbonyl stretching frequencies were observed in the ATR-FTIR spectra of CO₂ + PVAc, CO₂ + PMMA, CO₂ + PLA, and CO₂ + PLGA85 systems. These CO₂ induced blue shifts can be attributed to dielectric effects, and therefore cannot be used to quantify specific interactions in these systems. We propose the use of the temperature dependence of the CO₂ bending mode to quantify specific interactions in CO₂ + carbonyl polymers. With this method, the enthalpies of association for C=O...CO₂ specific interactions were found to be between -7 and -10 kJ/mol in the order: CO₂ + PVAc > CO₂ + PCL ≈ CO₂ + PLA > CO₂ + PLGA85 > CO₂ + PMMA. The method was also extended to other CO₂ philic polymers, leading to enthalpies of association in the order CO₂ + PEG > CO₂ + PVAc > CO₂ + PSF > CO₂ + PMSSQ >> CO₂ + PVDF&PS. Specific interactions in polymer + CO₂systems were also investigated via NVT molecular dynamics simulations Such interactions were found to decrease in the order: CO₂...C-O-C > CO₂...O=C-O > CO₂...Si-O-Si. In addition, the association distance was identified to be 3.2 Å. Finally, CO₂ accessibility was found to decrease in the order PVAc > PVMK > PLA > PMA. It was also confirmed that 96 % of associated CO₂ molecules interact with one carbonyl group in these systems. A ternary extension of the Compressible Lattice Model (CLM) was developed and the enthalpy of specific interactions obtained from ATR_FTIR spectra was incorporated into the model to correlate and predict phase behavior in polymer + CO₂ + cosolvent systems. This work shows that model parameters obtained from binary data can be used to predict ternary system behavior with average absolute deviations between calculated and experimental values (AAD) less than 10%. The Sanchez-Lacombe lattice-fluid partition function was extended to associated systems by incorporating an association factor obtained from the Compressible Lattice Model. The resulting Associated Sanchez-Lacombe (ASL) EOS has the same form as the SL EOS, but includes the effects of specific interaction in the calculation of lattice energies, and chemical potentials. We demonstrate that ASL model parameters obtained from correlation of sorption equilibria can be used to predict swelling of polymers with AAD less than 10%. In summary, specific interactions between CO₂ and C=O and other CO₂-philic groups have been quantified using in situ ATR-FTIR spectroscopy. The results have been directly incorporated into a lattice model that is able to correlate cloud points, and sorption equilibria, using a single parameter. The model is therefore likely to be beneficial in many applications involving polymer + CO₂ or polymer + CO₂ + cosolvent systems including polymer impregnation, coating, foaming, and polymer membranes for CO₂ capture. An EOS formulation for the model has been derived for the calculation of swelling in these systems.

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15

Moreau, Damien. "Characterization of flow within a polymer scaffold inside a compression-perfusion bioreactor." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16362.

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16

Gong, Kenan. "Polymer-drug formulations for controlled release via supercritical fluid assisted impregnation." Thesis, Queen Mary, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497849.

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Poorly water-soluble drugs with limited absorption in the gastrointestinal tract commonly show increased bioavailability when drug dissolution is improved by conversion to the amorphous form or a reduction in particle size. In this study, different polymer matrices were employed to convert model drugs into the amorphous state.

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Jouan, Gurvan. "Quantitative measurements of flow within a polymer scaffold inside a compression-perfusion bioreactor." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16776.

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18

Paricaud, Patrice. "Understanding the fluid phase behaviour of polymer systems with the SAFT theory." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/7465.

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19

Fateen, Seif-Eddeen K. (Seif-Eddeen Khaled) 1971. "Magnetophoretic focusing on submicron particles dispersed in a polymer-stabilized magnetic fluid." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8497.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.
Includes bibliographical references.
Magnetophoresis is the migration of particles upon the application of an inhomogeneous magnetic field. The overall goal of this work was to investigate the magnetophoretic focusing of non-magnetic particles suspended in magnetic fluids, which are colloidal suspensions of nano-sized magnetic particles. With the magnetic fluid as the solvent, dispersed non-magnetic particles behave as if they were diamagnetic due to the difference in magnetic susceptibility between them and the surrounding magnetic continuum. When an inhomogeneous magnetic force is applied, a magnetic force acts on the colloidal particles, the magnitude of which is linearly proportional to the volume of the particles, the difference in the magnetic susceptibilities of the particles and the surrounding magnetic fluid, and the gradient of the square of the magnetic field. One potential application for this phenomenon is in the separation of submicron biological particles such as viruses, cell fragments, DNA and inclusion bodies. Magnetic fluids have several characteristics that make them attractive for use in separation. For example, they can be tailored to the separation needs at hand, manipulated using external magnetic fields, and completely removed through magnetic filtration. Since the scope of the work was to use physical forces for attaining the desired separations, the magnetic particles were designed and synthesized without any chemical affinity to the solute to be separated. They were prepared by coprecipitation of iron (II) and (III) ions to form magnetite, which is coated by a comb copolymer that serves two purposes: to limit growth of magnetite to about 10 nm and to stabilize the particles against aggregation.
(cont.) The polymer was prepared by a reaction between amine-terminated polyethylene oxide and polyacrylic acid. Characterization of the particles was done experimentally and theoretically. Dynamic light scattering was used to measure the diffusion coefficient and the hydrodynamic diameter of the particles, while transmission electron microscopy was used to measure the diameter of the magnetic core. Since the structure of the magnetic fluid is an important parameter in its application in any magnetophoretic separation, we characterized the aggregation behavior of the magnetic fluids using different theoretical techniques. Monte Carlo simulation was used to understand the clustering in sterically-stabilized magnetic fluids. Simulation results agree favorably with the scattering experiments with regards to the cluster sizes and fractal dimensions. The characterization of a closely related system, a charge stabilized magnetic fluid, was also performed to explain the finite cluster size observed experimentally. Next, we investigated magnetophoretic focusing in the synthesized magnetic fluid, as a means to separate submicron colloidal particles based on size. The magnetophoresis concepts were validated experimentally by monitoring the dynamic evolution of the concentration profile of fluorescently-tagged polymer beads of various sizes in a magnetic fluid upon the application of an inhomogeneous magnetic field. Polymer beads larger than 0.2 /um focused at the point of zero force, and the effect of the magnetic field on the particles was correlated with their size...
by Seif-Eddeen K. Fateen.
Ph.D.

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20

Gabor, Kelly M. "Computational Investigations of Polymer Devolatilization Processes in Steam Contactors." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468849920.

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21

Chen, Shuwen. "A preliminary discourse on tunable rolling resistance of electrorheological fluid containing polymer composites." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1446586803.

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22

Khani, Shaghayegh. "COMPUTATIONAL MODELING OF POLYMER MELTS AND COMPOSITES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1481201559936174.

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23

Mobley, Sarah J. "Effects of Support Fluid Type on Concrete Integrity and Durability in Drilled Shafts." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7859.

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Until recently, concrete flow in tremie-placed drilled shafts has been mischaracterized as rising uniformly with laitance formation occurring only at the top of the rising concrete in the shaft. In actuality, concrete first fills a portion of the reinforcement cage to a sufficient height to promote radial flow into the cover region. Depending on support fluid type, the radial flow can produce laitance-filled creases/channels projecting the reinforcing cage configuration to the side of shaft surface. The flow pattern (and creases) can affect filter cake thickness, cover quality and propensity for corrosion. This research examines 52 tremie-placed laboratory drilled shaft specimens constructed using bentonite, polymer or natural support fluid to identify correlations between support fluid type and laitance channel formation. The extent of the laitance channel effect was quantified with surface texture, corrosion potential, and strength distribution methods. A direct correlation between the use of bentonite support fluid and laitance channel formation was identified which showed a high propensity for corrosion and lower concrete strengths.

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Lam, Carlos. "Properties and applications of polymer support fluids in geotechnical engineering." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ba0867c6-eb42-4b9a-a400-b464749855c5.

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Synthetic polymer fluids have been used as an alternative to conventional bentonite slurries for the excavation of foundation elements over the last two decades. Thus far their use has excited polarised views in the industry – some construction professionals avoid using them after hearing ‘horror stories’ about past failures whereas others believe that they are the future of support fluids because of the many benefits that they can offer. This situation has been found to be mainly due to a lack of understanding of what polymers really are and their properties. To address this issue, the various polymer products currently available in the market have been categorised based on their intended functions, and the fundamental properties of some of them have been characterised. The research showed that significant difference exists between polymers even of the same chemical family. Based on a series of rheological experiments, it was found that the properties of polymer fluids are highly dependent on the governing shear rate, time, and a range of site dependent factors. The research also showed that the current procedure for the interpretation of viscosity data is incorrect. After an analysis of the properties of currently available polymers, the latter part of the thesis describes a field trial carried out at a site in Stratford, East London. The aims of the trial were twofold: to compare the performance between piles constructed using bentonite and polymer fluids, and to assess the effect of extended pile bore open time for pile bores supported by polymers. From the results, it was found that the polymer piles showed much stiffer load–settlement response than the bentonite pile, and that a pile bore open time of up to 26 h had no adverse effect on the pile performance. The load test results have been carefully back-analysed using a range of methods. It was found that, compared to their bentonite counterparts, polymer fluids can improve the interface shearing resistance with Thanet Sand and the shear modulus of the Lambeth clay.

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Pandey, Vivek. "Extensional Mixing Elements for Improved Dispersive Mixing in Extrusion Operations." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1591698465031928.

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26

Choopanya, Pattarapong. "Computational fluid dynamics modelling of a polymer electrolyte membrane fuel cell under transient automotive operations." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/59505/.

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A polymer electrolyte membrane (PEM) fuel cell is probably the most promising technology that will replace conventional internal combustion engines in the near future. As a primary power source for an automobile, the transient performance of a PEM fuel cell is of prime importance. In this thesis, a comprehensive, three-dimensional, two-phase, multi-species computational fuel cell dynamics model is developed in order to investigate the effect of flow-field design on the magnitude of current overshoot/undershoot and characteristics of current response when the cell is subjected to different voltage change patterns representing an automotive operation. The meshing strategy specific to PEM fuel cell modelling is studied in a systematic manner and employed in all analyses presented in this thesis. The predicted results compare very well with experimental data under both steady-state and transient operations. Two computational domains are used – the straight single-channel and practical-scale square cells with parallel, single-serpentine, and triple-serpentine flow-fields. The results from the straight single-channel cell suggest that the magnitude of current overshoot/undershoot increases with the voltage change rate. The behaviour of a current response curve is the result of complex interplay between water content at both sides of the membrane. It is also found that current overshoot/undershoot is amplified with the presence water flooding in the cell. The results from the square cell reveal that current overshoot/undershoot is caused by non-uniformity of local current density over the active area confirming the effect of flow-field geometry on transient response of the cell. By comparing the transient performance between the three flow-fields, a direct relationship between degree of water flooding in the cell and magnitude of current overshoot/undershoot has been found. A conclusion has been drawn which states that a cell with superior water removal ability will experience smaller current overshoot/undershoot.

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27

Via, James C. "Applications of supercritical fluids to the extraction and analysis of oligomers and polymer additives." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38653.

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28

Mahboob, Monon. "Characterization and Microstructural Modeling of Composites: Carbon Nanofiber Polymer Nanocomposites and Magnetorheological Fluids." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1265262504.

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29

Nixon, Grant Ian. "Entropic trapping and polymer dynamics in static, quasi-periodic arrays of obstacles in two dimensional media." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26307.

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Using the bond fluctuation algorithm of Carmesin and Kremer (Carmesin and Kremer 1988), we investigate the static and dynamic properties of self-avoiding linear polymers embedded in static, two-dimensional (d=2), quasi-periodic arrays of obstacles with entropic traps. The phenomenon of polymer collapse, the closely related enrichment and depletion of polymer configurations, the conformational relaxation, and the diffusive behaviour are all investigated within the framework of the lattice Monte Carlo method. Several distinct dynamical regimes are encountered: the (obstacle-free) Rouse-like regime (obstacle sub-array concentration c=0), the reptation regime for chains in perfectly periodic obstacle sub-arrays (c=1), and, in the presence of disorder and entropic traps (0<c<1), the anomalous regimes where the scaling properties differ from those predicted by the Rouse and reptation theories. Prior to the onset of normal diffusion, even systems characterized by very slight disorder (i.e., the existence of random isolated void spaces) are shown to lead to long, transient, subdiffusive regimes where the mean square displacement of the centre of mass scales as RCM 2∼D*tbeta where 0.5<beta<1 is the anomalous diffusion exponent and D* is the anomalous diffusion coefficient. In such disordered systems, conformational relaxation is shown to be coupled with centre of mass subdiffusion, resulting in long, time-stretched, exponential relaxation of the Rouse coordinates, viz. exp.[-(t/tau) alpha]. The stretching exponents 0.5<alpha<1 are shown to be closely related to the anomalous diffusion exponents beta and where the alpha, for a given chain, are shown to decrease with increasing mode number and with strong disorder. The molecular size-dependence of the steady-state diffusion coefficient, as well as that of the conformational relaxation time, is shown to be greatest when the concentration of obstacles is large and when that of the voids is non-vanishing (c ≲ 1). Thus, the dynamical scaling in entropic trapping systems is non-monotonic with respect to the concentration of obstacles. Polymer reptation dynamics thus appears to be intrinsically unstable with respect to static disordered systems of obstacles. Having demonstrated the coupling of centre of mass subdiffusion and conformational relaxation, we introduce a new relaxation length scale, lambda=(2dD*t alpha)1/2, that is more appropriate for characterizing disordered systems than is the ubiquitous radius of gyration used in both the Rouse and reptation theories. However, lambda could not be distinguished from the radius of gyration in terms of the molecular size scaling given the uncertainty in our data. Finally, having proposed a theoretical dynamic model of entropic trapping for dilute polymer solutions in embedded mesoscopic voids, we investigate the effect of polymer solution concentration on the dynamics for both monodisperse and polydisperse polymer solutions. New, unexplored dynamical behaviours are manifest as the conformational and translational entropies compete to minimize the system free energy.

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30

Hossain, Mohammad Zahid. "A new lattice fluid equation of state for associated CO₂ + polymer and CO₂ + ionic liquid systems." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53475.

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The phase behavior of CO2 + polymer systems is of interest in polymer synthesis, flue and natural gas processing, polymer foam and nanoparticle processing, and drug delivery. Theoretical and experimental evidence suggests that CO2 is able to interact with electron donating functional groups in polymers to form weak Lewis acid – base or EDA (Electron Donor Acceptor) complexes. These complexes can have a significant effect on the phase behavior of associated CO2 + polymer systems. In spite of this, however, the phase equilibria of only a few associated CO2 + polymer systems have been measured. Some success in modeling the phase behavior of polymer solutions has been achieved by various versions of the Statistical Association Fluid Theory (SAFT), as well as by several Lattice Models. However, many of these models incorporate two to four adjustable parameters that often depend on temperature (T), pressure (P), and/or molecular weight (MW). As a result, a large amount of experimental data is required to apply these models. The goal of the present work was therefore to develop a new thermodynamic model for associating systems that would include no more than two temperature-independent adjustable parameters. The new model presented in this work is based on the Guggenheim-Huggins-Miller lattice and includes complex formation in the development of the partition function. The EOS obtained from the resulting partition function includes two mixture parameters – the enthalpy of association or complex formation and a reference value of the equilibrium constant for complex formation . Most importantly, can be obtained from in situ Attenuated Total Reflection Fourier Transform Infrared (ATR – FTIR) measurements. This work therefore demonstrates the use of ATR – FTIR spectra to obtain molecular level information regarding the interaction of CO2 and electron donating functional groups in polymers. Unlike other studies, this work uses the bending vibration of CO2 to estimate the enthalpies of association ( ) of CO2 + polymer systems. Values of were directly incorporated in the new model and were found to lie between -7 and -12 kJ/mol for the systems investigated in this work. They increased (i.e. became more negative) in the order: CO2 + PS-co-PMMA < CO2 + PMMA

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31

Chakravarthy, Deepak. "Application of X-ray CT for investigating fluid flow and conformance control during CO2 injection in highly heterogeneous media." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2370.

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Fractured reservoirs have always been considered poor candidates for enhanced oil recovery. This can be attributed to the complexities involved in understanding and predicting performance in these reservoirs. In a fractured system, the high permeability fracture forms the preferred pathway for the injected fluids, and a large amount of oil that is stored in the matrix is bypassed. Hence, a good understanding of multiphase fluid flow in fractures is required to reduce oil bypass and increase recovery from these reservoirs. This research investigates the effect of heterogeneity and injection rates on oil bypass and also the various techniques used for the improvement of sweep efficiency in heterogeneous systems. Several coreflood experiments were performed using homogeneous and heterogeneous cores and a 4th generation X-Ray CT scanner was used to visualize heterogeneity and fluid flow in the core. Porosity and saturation measurements were made during the course of the experiment. The experimental results indicate that injection rates play a very important role in affecting the recovery process, more so in the presence of fractures. At high injection rates, faster breakthrough of CO2 and higher oil bypass were observed than at low injection rates. But very low injection rates are not attractive from an economic point of view. Hence water viscosified with a polymer was injected directly into the fracture to divert CO2 flow into the matrix and delay breakthrough, similar to the WAG process. Although the breakthrough time reduced considerably, water ??leak off?? into the matrix was very high. To counter this problem, a cross-linked gel was used in the fracture for conformance control. The gel was found to overcome ??leak off?? problems and effectively divert CO2 flow into the matrix. This experimental research will serve to increase the understanding of fluid flow and conformance control methods in fractured reservoirs.

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32

Wu, Yue. "Experimental Determination and Equation of State Modeling of High-Pressure Fluid Behavior." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3237.

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High-pressure solution behavior such as density and phase behavior is a critical fundamental property for the design and optimization of various chemical processes, such as distillation and extraction in the production and purification of oils, polymers, and other natural materials. In this PhD study, solution behavior data are experimentally determined and equation of state (EoS) modeled for n-hexadecane, n-octadecane, n-eicosane, methylcyclohexane, ethylcyclohexane, cis-1,2-dimethylcyclohexane, cis-1,4-dimethylcyclohexane, trans-1,4-dimethylcyclohexane, o-xylene, m-xylene, p-xylene, and 2-methylnaphthalene at temperatures to 525 K and pressures to 275 MPa. A variable-volume view cell coupled with a linear variable differential transformer is used for the high-pressure determination. The reported density data are less than 0.4% of available literature data, which is within the estimated accumulated experimental uncertainty, 0.75%. Special attention is paid to the effect of architectural differences on the resultant high-pressure solution behavior. The reported data of low molecular weight hydrocarbons are modeled with Peng-Robinson (PR) equation of state (EoS), high-temperature high-pressure volume-translated cubic (HTHP VT-cubic) EoS, and perturbed-chain statistical fluid theory (PC-SAFT) EoS. The three pure-component parameters in PC-SAFT EoS can be either obtained from literature or from a group contribution (GC) method. Generally, PR EoS gives the worst predictions and HTHP VT-cubic EoS provides modest improvements over the PR EoS, but both of the equations underpredict the densities at high pressures. On the other hand, PC-SAFT EoS, with parameters from the literature or from a GC method, gives the improved density predictions with respect to PR EoS and HTHP VT-cubic EoS, although an overprediction of densities is found at high pressures. Model calculations also highlight the capability of these equations to account for the different densities observed for the hydrocarbon isomers. However, none of the EoS investigated in this study can fully account for the effect of isomeric structural differences on the high-pressure densities. For a better prediction of densities at high pressures, a new set of PC-SAFT pure-component parameters are obtained from a fit of the experimental density data obtained in this study and the mean absolution percent deviation is within 0.4%. The experimental technique and PC-SAFT EoS modeling method are extended to a star polymer-propane mixture. Star polymers with a fixed number of arms have a globular structure that does not promote chain entanglements. Star polymers can be synthesized with a large number of functional groups that can be readily modified to adjust their physical properties for specific applications in the areas of catalysis, coatings, lubrication, and drug delivery. In this study, a star polymer with a divinylbenzene core and statistically random methacrylate copolymer arms is synthesized with reversible addition-fragmentation-transfer method and fractionated with supercritical carbon dioxide and propane to obtain fractions with low molecular weight polydispersity. The phase behavior and density behavior are experimentally determined in supercritical propane for fractionated star polymers and the corresponding linear copolymer arms at temperatures to 423 K and pressures to 210 MPa. Experimental data are presented on the impact of the molecular weight, the backbone composition of the lauryl and methylmethacrylate repeat units in the copolymer arms, and the DVB core on the polymer-propane solution behavior. The star polymer is significantly more soluble due to its unique structure compared with the solubility of the linear copolymer arms in propane. The resultant phase behavior for the two homopolymers and the copolymers in propane are modeled using the PC-SAFT and copolymer PC-SAFT EoS, which give reasonable predictions for both phase behavior and density behavior. Model calculations are not presented for the phase behavior of the star polymers in propane since the PC-SAFT approach is not applicable for star polymer structures.

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33

Kahvecioglu, Alper. "Designing Lost Circulation Pills For Polymer Based Drill-in Fluids." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610226/index.pdf.

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Specially designed non-damaging lost circulation pills (LCP) are being effectively applied for drilling depleted zones worldwide. Optimizing the LCP compositions stop the lost circulation effectively and protect the production zone from liquid and solids invasion significantly. Shape, particle size distribution and concentration of the lost circulation materials (LCM) are key parameters determining the effectiveness of LCP. In this study, the Permeability Plugging Apparatus (PPA) is utilized to evaluate effectiveness of various LCM&rsquo
s in curing the lost circulation. Sized calcium carbonates are used as LCM in different concentrations and in different particle size distribution. Lost circulation zones are simulated using the ceramic disks and slotted disks. Ceramic disks with nominal pore sizes 20, 35, 60, 90, and 150 microns are characterized in terms of pore size distribution using the computerized image analysis technique. Filter cake quality, spurt loss and filtrate volume are basic parameters to be evaluated in this study. Tests are performed at 75 F and 300 psi of differential.

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34

Costello, Kelly. "A Theoretical and Practical Analysis of the Effect of Drilling Fluid on Rebar Bond Strength." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7489.

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Drilled shafts are large cylindrical cast-in-place concrete structural elements that can be favored due to cost-effectiveness. These elements however, require strict quality control during construction to ensure a stable excavation. Drilling fluid is often used in construction to attain this stability. Drilling fluid, or slurry, can be ground water or salt water, but is typically made from a mixture of water and mineral or polymer powder to form a viscous fluid slightly more dense than ground water. During concreting, the drilling fluid is displaced by the heavier concrete, which is tremie placed at the base of the excavation from the center of the reinforcement cage. While concrete used for drilled shafts should be highly fluid, it does not follow an ideal, uniform flow. The concrete rather builds up inside the reinforcement cage to a sufficient height before then pressing out radially into the annular cover region. This concrete flow pattern associated with drilled shafts has been shown to trap slurry around/near the steel reinforcement and affect reinforcement bond strength. Presently there are no specifications relating to slurry effects on reinforcing bar bond strength from the American Concrete Institute (ACI) or the American Association of State and Highway Transportation Officials (AASHTO). This dissertation analyzes longitudinal reinforcing bar concrete bond strength data recorded from 268 specimens constructed with tremie-placed concreting conditions in varying drilling fluids. Reinforcement used for testing were No. 8 deformed rebar. Based on the results found from this analysis, this dissertation recommends the use of a slurry modification factor to current bond strength and development length specifications.

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35

Lynch, Daniel P. "The effect of polymer dose and mixing intensity on sludge dewatering with a plate and frame filter press." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44124.

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Experiments were performed with anaerobically digested sludge and a plate and frame filter press to determine filter press performance over a range of polymer doses and under a variety of sludge and polymer mixing conditions. In addition, bench-scale polymer dosing and mixing experiments were conducted with the same sludge samples to determine the relationship between the bench-scale tests and actual plate and frame filter press performance. Dewatering rate was measured in bench- scale experiments with a Capillary Suction Time (CST) device and dewatering rate in pilot-scale experiments was quantified by measuring the volume of filtrate from the plate and frame press. The dimensionless quantity, Gt, was used to measure total mixing intensity input where G was the mean velocity gradient and t was the mixing time for the sludge and polymer.

The performance of the plate and frame filter press was optimized by predicting polymer dose with a bench-scale mixing device. For the plate and frame filter press used in this study, the polymer dose was selected by finding the optimum polymer dose for the bench-scale mixing system set at a Gt value of 30,000. The sludge and polymer were mixed with a Gt value of 5000 prior to introduction to the filter press. The polymer dosing and mixing scheme that was developed for the filter press in this study indicates that the filter press imparts some shear (G) on the sludge and that polymer must be provided to reagglomerate fractured sludge particles. An estimate of the Gt value for the filter press that was used in this study is 15,000 to 40,000.

Master of Science

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36

Drewniak, Marta. "Computer Simulations of Dilute Polymer Solutions: Chain Overlaps and Entanglements." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278086/.

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Chain conformations and the presence of chain overlaps and entanglements in dilute polymer solutions have been analyzed. The fundamental problem of existence of chain overlaps in dilute solutions is related to the drag reduction phenomenon (DR). Even though DR occurs in solutions with the concentration of only few parts per million (ppm), some theories suggest that entanglements may play an important role in DR mechanism. Brownian dynamics technique have been used to perform simulations of dilute polymer solutions at rest and under shear flow. A measure of interchain contacts and two different measures of entanglements have been devised to evaluate the structure of polymer chains in solution. Simulation results have shown that overlaps and entanglements do exist in static dilute solutions as well as in solutions under shear flow. The effect of solution concentration, shear rate and molecular mass have been examined. In agreement with the solvation theory of DR mechanism, simulation results have demonstrated the importance of polymer + polymer interactions in dilute solutions.

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37

Potter, Catherine. "Application of supercritical fluid technology to the pre-formulation and production of amorphous solid dispersions." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677955.

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38

Deladisma, Marnico David. "Accuracy and Enhancement of the Lattice Boltzmann Method for Application to a Cell-Polymer Bioreactor System." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10546.

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Articular cartilage has a limited ability to heal due to its avascular, aneural, and alymphatic nature. Currently, there is a need for alternative therapies for diseases that affect articular cartilage such as osteoarthritis. Recently, it has been shown that tissue constructs, which resemble cartilage in structure and function, can be cultured in vitro in a cell-polymer bioreactor system. Bioreactors provide a three dimensional environment that promotes cell proliferation and matrix production. The primary objective of this study is to accurately simulate fluid mechanics using the lattice Boltzmann method for application to a cell-polymer bioreactor system. Lattice Boltzmann (LB) is a flexible computation technique that will allow for the simulation of a moving construct under various bioreactor conditions. The method predicts macroscopic hydrodynamics by considering virtual particle interactions. Derived from the Lattice Gas Automata, lattice Boltzmann allows for mass transfer, complex geometries, and particle dynamics. A primary goal is to characterize the accuracy of the LB implementation and eventually the shear stresses felt by a tissue construct in this dynamic environment. This information is important since recent studies show that chondrocytic function may depend on the mechanical stimuli produced by fluid flow. Hence, shear stress may affect the final mechanical properties of tissue constructs. In this study, numerical simulations are done first in 2D and then extended to 3D to test the LB implementation. Simulations of the rotating wall vessel (RWV) bioreactor are then undertaken. The results are benchmarked against computations done with a commercial CFD package, FLUENT, and compared with analytic solutions and experimental data.

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39

Almahmoud, Omar H. M. "Design Optimization of Functionalized Silica-Polymer Nanocomposite through Finite Element and Molecular Dynamics Modeling." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1707245/.

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This dissertation focuses on studying membrane air dehumidification for a membrane moisture exchanger in a membrane heat pump system. The study has two parts: an optimization of membrane moisture exchanger for air dehumidification in the macroscale, and diffusion of water vapor in polymer nanocomposites membrane for humid air dehumidification in the nanoscale. In the first part of the research, the mass transport of water vapor molecules through hydrophilic silica nanochannel chains in hydrophobic polyurethane matrix was studied by simulations and experiments for different membrane moisture exchanger design configurations. The mass transport across the polymer nanocomposite membrane occurs with the diffusion of moist air water vapor molecules in the membrane moisture exchanger in a membrane heat pump air conditioning system for air dehumidification purposes. The hydrophobic polyurethane matrix containing the hydrophilic silica nanochannel chains membrane is responsible for transporting water vapor molecules from the feed side to the permeate side of the membrane without allowing air molecules to pass through.In the second part of the research, diffusion analysis of the polymer nanocomposite membrane were performed in the nanoscale for the polymer nanocomposite membrane. The diffusion phenomena through the polymer, the polymer nanocomposite without modifying the silica surfaces, and the polymer nanocomposite with two different silica modified surfaces were studied in order to obtain the highest water vapor removal through the membrane. Different membrane moisture exchanger configurations for optimal water vapor removal were compared to get the desired membrane moisture exchanger design using the finite element method (FEM) with the COMSOL Multiphysics software package. The prediction of mass transport through different membrane configurations can be done by obtaining the mass flux value for each configuration. An experimental setup of one membrane moisture exchanger design was introduced to verify the simulation results. Also, for different membrane structures, permeability was measured according to the ASTM E-96 method. The prediction of water vapor diffusion through the polymer nanocomposite was studied by molecular dynamics simulation with the MAPS 4.3 and LAMMPS software packages. As a new nanocomposite material used in air dehumidification application, water vapor diffusivity through Silica-Polyurethane nanocomposite membranes was measured by the random movement of water vapor molecules through the formed nanochannels in the nanocomposite. For the diffusivity value, the Einstein's relationship was employed for the movement of each single water vapor molecule during the simulation time for all suggested membranes. The results of the proposed research will contribute to enhancing the energy efficiency of air conditioning systems by choosing the membrane moisture exchanger configuration which maximizes water vapor removal while, at the same time, enhancing the silica surfaces with the desired surface modifier that will maximize diffusion through the membrane itself.

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40

Bakan, Murat. "Development Of Polymer Resin-based Wet Friction Sheet Materials And Understanding Their Interactions With Automatic Transmission Fluids." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1438257941.

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41

Igder, Aghil. "Application of the Vortex Fluid Device (VFD) in Polysulfone Synthesis and Ultra-filtration Membrane Fabrication for water treatment purposes." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2433.

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Extensive studies have been performed to improve key properties of filtration membranes via controlling the fabrication process conditions as well as physical and/or chemical modification of the polymers used in membrane fabrication. The Vortex Fluid Device (VFD) is a newly invented platform which has found many applications in materials science and clean technology. The unique features of the VFD originate from a combination of different effects (e.g., micro-mixing, viscous drag, microfluidic flow, enhanced mass transfer) all resulting in faster, greener, and more efficient and better controlled chemical reactions. The main aims of this project are: (i) to investigate the utility of VFD processing in an environmentally friendly process for PSF synthesis, (ii) fine-tuning the process conditions and consequently improving the properties of the polymer, and (iii) the application of the VFD in facilitating a time effective process for PSF ultrafiltration membrane fabrication while investigating the effect of changing the rotational speed of the VFD and Graphene Oxide (GO) incorporation into PSF based membranes along with their filtration performances. Initially, Polysulfone (PSF) was prepared under high shear in the VFD operating in the confined mode, and its properties compared with that prepared using batch processing. Scanning electron microscopy (SEM) established that the VFD synthesised PSFs are sheet-like, for short reaction times, and fibrous for long reaction times, in contrast to spherical like products from the conventional batch synthesis. The operating parameters of the VFD were systematically varied for establishing their effect on the molecular weight (Mw), glass transition temperature (Tg) and decomposition temperature, featuring gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) respectively. The optimal VFD prepared PSF was obtained at 6000 rpm rotational speed, 45° tilt angle and 160 °C, for 1 h with the material having a Mw ∼10000 g mol−1, Tg ∼158 °C and decomposition temperature ∼530 °C, which is comparable to the conventionally prepared PSF. In the next step, the synthesise process has been systematically varied to improve the main properties of the PSF, including the Mw which is now ∼15500 g mol−1. Morphological study accompanied by BET measurement were conducted to support the results and investigate the effect of the VFD operational parameters on the properties of the new VFD synthesised PSF. In another aspect of the research, PSF ultrafiltration (UF) membranes were fabricated using a continuous micro-mixing process under high shear in the vortex fluidic device (VFD) followed by phase inversion process of the cast solution. This involved investigating the effect of PSF concentrations (10, 15, and 20%) in 1-methyl-2-pyrrolidone (NMP) as well as the rotational speed of the VFD for a 0.5 mL/min continuously mixing process at 30 °C, on the properties of the membranes. The properties of the VFD mediated membranes were compared with those fabricated using conventional batch mixed polymer solutions (24 h magnet stirring at 60 °C, 3h sonication), with the membranes fully characterized through structural and morphological studies, hydrophilicity, and filtration performance, as well as thermal and mechanical stabilities. Use of the VFD showed a significant impact on essential mixing time by facilitating a very shorter mixing process. SEM established that in the microfluidic mixing, the PSF membranes have more finger-like cross-section, for 10% PSF concentration, and more sponge-like structure for higher concentrations. Moreover, the higher rotational speed in the VFD mediated membranes, the higher their porosity (84.3±2.4) % and permeability (106±4) LMH/bar which were optimal at 7k rpm. Furthermore, to improve the properties of the membrane, GO was incorporated into the polymer solutions both using VFD and conventional mixing, resulting in GO/PSF composite membranes with enhanced properties. It was also found that compared to pristine PSF membranes, the incorporation of 1 wt.% of GO increased its permeability from (97±3) to (123±4) LMH/bar, salt rejection from (18.5±1.3) to (34.3±1.7) % and bovine serum albumin (BSA) rejection from (53.8±2) to (74.2±2) %, respectively.

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42

Smith, Susan H. "Extraction of Additives from Polystyrene and Subsequent Analysis." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36774.

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The extraction of fifteen (15) polymer additives with supercritical carbon dioxide which are used as antioxidants, uv stabilizers, process lubes, flame retardants and antistats from eight formulations of polystyrene is demonstrated and compared to traditional dissolution/precipitation extractions. The purpose of the study was twofold: 1) the development of a high performance liquid chromatography (HPLC) method(s) for the additives and 2) the determination of the viability of supercritical fluid extraction (SFE) for the additives from polystyrene. Separation of some of the additives was achieved using reversed phase liquid chromatography. Nine of the additives were assayed in this manner while, the remaining six additives could not be assayed using reversed phase liquid chromatography. In order to develop an extraction method for the additives, the effects of static extraction time, CO2 density, and temperature were first investigated. These preliminary extractions revealed that a static extraction period which afforded an opportunity for the polymer to swell combined with a high CO2 density and extraction temperature above the glass transition (Tg) yielded quantitative recoveries of the additives. Triplicate extractions of the various polystyrene formulations matched additive recoveries obtained by the traditional dissolution/precipitation method.
Master of Science

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43

Mohee, Lakshana. "Collagen scaffolds for tissue engineering : the relationship between microstructure, fluid dynamics, mechanics and scaffold deformation." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276980.

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Collagen scaffolds are porous structures which are used in bioreactors and in a wide range of tissue engineering applications. In these contexts, the scaffolds may be subjected to conditions in which fluid is forced through the structure and the scaffold is simultaneously compressed. It is clear that fluid transport within collagen scaffolds, and the inter-relationships between permeability, scaffold structure, fluid pressure and scaffold deformation are of key importance. However, these relationships remain poorly understood. In this thesis, a series of isotropic collagen structures were produced using a freeze-drying technique from aqueous slurry concentrations 0.5, 0.75 and 1 wt%, and fully characterised using X-ray micro-tomography and compression testing. It was found that collagen wt% influenced structural parameters such as pore size, porosity, relative density and mechanical properties. Percolation theory was used to investigate the pore interconnectivity of each scaffold. Structures with lower collagen fraction resulted in larger percolation diameters, but lower mechanical stiffness. Aligned collagen scaffolds were also produced by altering the freeze-drying protocol and using different types of mould materials and designs. It was found that a polycarbonate mould with stainless base resulted in vertically aligned structures with low angular variation. When compared with isotropic scaffolds from slurry of the same concentration, aligned scaffolds had a larger percolation diameter. Tortuosity was used as a mathematical tool to characterise the interconnected pathways within each porous structure. The effect of the size of the region of interest (ROI) chosen and the size of the virtual probe particle used in the analysis on the values of tortuosity calculated were determined and an optimised calculation methodology developed. Increasing the collagen fraction within isotropic scaffolds increased the tortuosity, and aligned structures had smaller tortuosity values than their isotropic counterparts. Permeability studies were conducted using two complementary experimental rigs designed to cover a range of pressure regimes and the results were compared with predictions from mathematical models and computational simulations. At low pressures, it was found that the lower collagen fraction structures, which had more open morphologies, had higher permeabilities. Alignment of the structure also enhanced permeability. The scaffolds all experienced deformation at high pressures resulting in a restriction of fluid flow. The lower collagen fraction scaffolds experienced a sharper decrease in permeability with increased pressure and aligned structures were more responsive to deformation than their isotropic counterparts. The inter-relationships between permeability, scaffold structure, fluid pressure and deformation of collagen scaffolds were explored. For isotropic samples, permeability followed a broad $(1- \epsilon)^2$ behaviour with strain as predicted by a tetrakaidecahedral structural model, with the constant of proportionality changing with collagen fraction. In contrast, the aligned structures did not follow this behaviour with the permeability dropping much more sharply in the early stages of compression. Open-cell polyurethane (PU) foams, sometimes used as dressings in wound healing applications, are often compared with collagen scaffolds in permeability models and were used in this thesis as a comparison structure. The foam had a higher permeability than the scaffolds due to its larger pore sizes and higher interconnectivity. In the light of the effects of compression on permeability, the changes in porous structure with compression were explored in isotropic and aligned 0.75 wt% scaffolds. Unlike the fluid flow experiments, these experiments were carried out in the dry state. Deformation in simple linear compression and in step-wise compression was studied, and the stress relaxation behaviour of the scaffolds characterised. A methodology was developed to characterise the structural changes accompanying compression using X-ray micro-tomography with an in situ compression stage. The methodology accounted for the need for samples to remain unchanged during the scan collection period for stable image reconstruction. The scaffolds were studied in uniaxial compression and biaxial compression and it was found that pore size and percolation diameter decreased with increasing compressive strain, while the tortuosity increased. The aligned structure was less affected than the isotropic at low compressions, in contrast to the results from the permeability study in which the aligned structure was more responsive to strain. This suggests that the degree of hydration may affect the structural changes observed. The insights gained in this study of the inter-relationships between microstructure, fluid dynamics and deformation in collagen scaffolds are of relevance to the informed design of porous structures for medical applications.

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44

Yeasting, Kyle Douglas. "The Evaluation of Hybrid Slurry Resulting from the Introduction of Additives to Mineral Slurries." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3415.

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Drilled shaft construction often requires the use of drill slurry to maintain borehole stability during excavation and concreting. While drill slurry may be composed of fluids ranging from air to petroleum, drilled shaft construction typically makes use of water based drilling fluids. Although clean water may be utilized as a drilling fluid, a premixed slurry consisting of water, minerals, and/or polymers is more commonly used. Florida Department of Transportation (FDOT) specifications require the use of mineral slurry for all primary structures. The slurry resists the intrusion of groundwater, slows the outward migration of drilling fluid from the excavation, and aids in the removal of suspended soil cuttings. The mechanisms by which mineral slurries work are quite different from those of polymer slurries. Due to these differences, it is unclear whether a mineral based slurry, which has been fortified with polymers by manufacturers or enhanced through the addition of polymers in the field, behaves more like a mineral slurry rather than polymer slurry. This thesis provides an overview of the methods used to measure physical slurry parameters of interest. These parameters include density, viscosity, pH, sand content, and filtration control. Methods employed to describe the slurry parameters include tools and instrumentation commonly used in both field and laboratory settings.

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45

Kamarajugadda, Sai K. "Advanced Models for Predicting Performance of Polymer Electrolyte Membrane Fuel Cells." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1323758118.

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46

Gurbuz, Berkay. "Experimental Characterization Of Some Water Soluble Polymers Used In Drilling And Completion Fluids." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614146/index.pdf.

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Properly preparing the drilling fluid is an essential part of any successful drilling operation, especially in complex operations like deviated and horizontal drilling. Understanding the flow behavior of the polymers used in the drilling fluids under different conditions takes a key part in this preparation. In this study, shear rheology of some traditionally used water soluble polymers in drilling and completion fluids
namely PAC (polyanionic cellulose) and xanthan gum, were investigated experimentally. Instead of an oilfield standard Fann Model 35 Viscometer, an Ofite Model 900 Viscometer was used because of its capability to measure at ultra-low shear rates. Effects of the concentration of the polymer, time of shear applied, test temperature and effects of aging were examined. Rheological measurements were conducted between the shear rate ranges of 0.01 to 1000s-1 with concentrations changing from 0.25 to 1.5 grams of polymer per 350 milliliters of water (equivalent to 0.25 to 1.5 lb/bbl). Rheograms were constructed to identify the effect the polymers in question have on the flow characteristics of the drilling fluid. An appropriate constitutive model was used to define the flow behavior of the polymer in question mathematically. It was observed from the constructed rheograms that increase in polymer concentration results in consistent increase of apparent viscosity. Amount of time of shear does not affect the selected polymers if they are dynamically aged at least for two hours. Also as expected increasing temperature of the sample lowers the apparent viscosity considerably.

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47

Kalaikadal, Deepak Saagar. "Investigation of Bubble Dynamics in Pure Liquids and Aqueous Surfactant / Polymer Solutions Under Adiabatic and Diabatic Conditions." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1525167893347615.

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48

Silveira, Bruno Marco de Oliveira 1985. "Invasão de fluidos de perfuração e fluxo reverso de óleo em reservatórios de arenito e de carbonato." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265243.

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Orientador: Rosângela Barros Zanoni Lopes Moreno
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-20T08:21:26Z (GMT). No. of bitstreams: 1 Silveira_BrunoMarcodeOliveira_M.pdf: 1762377 bytes, checksum: cbdcb4c20dc00b869c37775090896cf4 (MD5) Previous issue date: 2012
Resumo: As recentes descobertas do pré-sal no Brasil trouxeram novos desafios para as atividades de explotação de petróleo. Perfuração em formações carbonáticas apresentam grandes diferenças em relação a perfurações em rochas areníticas. Enquanto arenitos são mais homogeneos, rochas carbonáticas podem apresentar significativas variações em relação ao tamanho e à distribuição de poros, refletindo na produtividade de formação, como também na operação e manutenção de produção. A produtividade dos poços é avaliada logo após a perfuração dos mesmos, uma vez que danos à formação produtora podem alterar suas características originais. Diante disso, fluidos especificamente formulados para perfurar o reservatório, conhecidos como fluidos drill-in, vem sendo estudados com vistas à otimização da perfuração e à minimização de dano. Estes fluidos são desenvolvidos de acordo com as características do reservatório a ser perfurado e testes em laboratórios são necessários para que se possa adequar a formulação do fluido de perfuração com o menor custo, além de avaliar a invasão na rocha e verificar o possível dano residual para os fluidos candidatos. Este trabalho visa a comparação da invasão de fluidos drill-in e fluxo reverso de óleo em amostras de carbonatos e de arenitos de forma a avaliar a influência do tipo de rocha no dano à formação e sua interação com o fluido de perfuração testado. Os testes foram realizados usando dois aparatos experimentais diferentes, um para amostras com cerca de 7 cm de comprimento e outro para amostras medindo cerca de 30 cm, ambas com diâmetro de aproximadamente 3,7 cm. Os ensaios foram executados em amostras de carbonato e de arenito com permeabilidades absolutas ao gás semelhantes e submetendo-as ao respectivo protocolo de teste, cujas etapas incluíam a preparação das amostras, a caracterização de escoamento multifásico, a invasão com fluido de perfuração e o fluxo reverso de óleo. A invasão foi induzida por meio de um diferencial de pressão positivo através das amostras saturadas com óleo na condição de água conata, simulando o reservatório. O fluxo reverso ou deslocamento de óleo no sentido oposto ao de invasão representou a produção de óleo bem como a limpeza natural do reservatório. Durante a caracterização foi possível observar que as amostras de carbonatos utilizadas são menos molháveis à água em comparação aos arenitos. Com os resultados obtidos com o aparato utilizado para as amostras mais longas, foi possível identificar o deslocamento da frente de fluido invasor por meio dos pontos de medida de pressão distribuídos ao longo da amostra. A dinâmica de escoamento apontou que a invasão do fluido de perfuração foi mais rápida para as amostras de carbonatos em comparação com as amostras de arenito. Na etapa de fluxo reverso, pode-se observar que as amostras de carbonato apresentaram um retorno de produtividade maior e mais rápido relativamente aos arenitos
Abstract: The recent pre-salt discoveries in Brazil have brought new challenges to oil exploitation activities. Drilling in carbonate formations differs widely of drilling in sandstone rocks. While sandstones are more homogeneous, carbonate rocks are characterized by a large range of size and distribution of pores, which reflects in the reservoir productivity, as well as in the operation activities and production maintenance. The productivity and changes of original reservoir's characteristics due to formation damage are evaluated after drilling. Then fore, drilling fluids specifically designed to cross pay-zone, known as drill-in fluids, have been studied aiming at drilling optimization and damage minimizing. These fluids are developed according to the drilled reservoir characteristics and laboratory tests are performed to obtain proper drilling fluids formulations as fluid invasion and clean up are evaluated. The objective of this work is to compare drill-in fluids invasion (water-based polymer fluid) and backflow of oil in carbonates and sandstones samples to assess the rock type influence in damage formation and their interaction with the tested drilling fluid. Tests were run using two different apparatus, one for samples ~7,0 cm long and another for samples ~30 cm long, both with ~3,7 cm diameter. Lab tests were performed using carbonate and sandstone samples, with similar absolute permeability. These samples were submitted to a proper test protocol, that includes samples preparation, multiphase flow characterization, invasion and backflow processes. Damage formation was induced by injecting drill-in fluid with a positive differential pressure through samples saturated with oil and connate water, simulating the reservoir. Oil displaced in the opposite flow direction was performed to simulated natural cleanup or oil production. During the samples characterization, it was possible to observe that tested carbonate samples were less water wet than sandstones ones. From the results obtained with the apparatus used with longer samples, it was possible to identify the drill-in fluid displacement through pressure observation points distributed throughout the sample. The flow dynamics pointed out that the drilling fluid invasion was faster for carbonate samples comparing to sandstone samples. However, in backflow stage, a higher and faster productivity restoration was observed for carbonate samples than for sandstone ones
Mestrado
Reservatórios e Gestão
Mestre em Ciências e Engenharia de Petróleo

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49

Wallis, Kirsty. "Design of experiment studies for the fabrication processes involved in the micro-texturing of surfaces for fluid control." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8456.

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This thesis focuses on the use of a design of experiment approach to examine the significance of process factors and interactions on the fabrication of micro- textured surfaces. The micro-textured surfaces examined contain pillar and hole features ranging from 80 – 2 micrometers in diameter. The processes examined are the deep reactive ion etching of silicon wafers for the production of silicon mould inserts and the micro-injection moulding of polypropylene, high density polyethylene and 316LS stainless steel replicate samples of the silicon mould insert. During the deep reactive ion etching of the silicon wafers the design of experiment approach was used to determine the significant of platen power, C4F8 gas flow and switching times to the presence of pillar undercut of 10 x 10, 5 x 5 and 2 x 2 micrometer pillars. Undercuts occur when the pillar base has a smaller cross-section than the apex of the pillar. Switching times was found to be the only statistically significant parameter for both 10 x 10 and 5 x 5 micrometer pillars. The design of experiment approach is used in the micro-injection moulding of polypropylene, high density polyethylene and 316LS stainless steel replicates to examine the significance of mould temperature, cooling time, holding pressure and injection speed on the part and buffer mass of the produce samples, the height and width of pillar on the replicate surfaces and the variation of the replicated pillars height and width from the original silicon mould insert. Examination of the high density polyethylene replicates found that mould temperature was the most significant factor regarding pillar dimensions (and variation from the silicon mould insert) across the range of pillar sizes. Upon examination of the polypropylene replicates it was found that the factor of most significance on pillar dimensions varied across the different pillar sizes. Holding pressure was identified as the most significant factor with regards to the 53 x 29 and 19 x 80 micrometer pillars. Injection speed was found to be most significant for the 25 x 25 and 19 x 29 micrometer pillars. Cooling time was found to be most significant with regards to the 30 x 10, 25 x 10, 20 x 10 and 15 x 10 micrometer pillars. While ii mould temperature was found to be most significant for the 20 x 20, 15 x 15 and 10 x 30 micrometer pillars. The interaction between mould temperature and injection speed was also found to be the most significant factor with regards to the 43 x 29 and 25 x 30 micrometer pillars. Examination of the 316LS replicates found that mould temperature was the most significant factor regarding pillar dimensions for 80 x 80 and 19 x 80 micrometer pillars. While holding pressure was found to be most significant to the 29 x 29 micrometer pillars and injection speed was identified as most significant to the 53 x 80 micrometer pillars. The samples produced during the design of experiment investigations were then used to examine the effect of surface texturing on droplet behaviour. Droplet contact angles were examined on polypropylene, high density polyethylene and silicon samples structured with 10 – 2 micrometer pillar. Initial droplet contact angles were found to be higher on the polypropylene samples than the high density polyethylene or silicon samples. With the lowest initial contact angles being found for the silicon inserts. Droplet ‘channelling’ and evaporation were examined on silicon, polypropylene, high density polyethylene and 316LS samples structured with micro-channel surface pillars and holes ranging from 80 – 2 micrometer in diameter. Contact pinning of the droplet to the surface via the three- phase contact-line was noted during observations of droplet ‘channelling’. This pinning effect was observed at all sample tilt angles (30 - 90 o ). With regards to droplet evaporation, the droplets were noted to evaporate evenly (with no or limited contact pinning) on all unstructured surfaces and the surfaces structured with hole features. On the surfaces structured with pillar features, the droplets appeared too evaporated along the surface gradient from the smallest pillars to the largest.

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Figueroa, Leonardo E. "Deterministic simulation of multi-beaded models of dilute polymer solutions." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:4c3414ba-415a-4109-8e98-6c4fa24f9cdc.

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We study the convergence of a nonlinear approximation method introduced in the engineering literature for the numerical solution of a high-dimensional Fokker--Planck equation featuring in Navier--Stokes--Fokker--Planck systems that arise in kinetic models of dilute polymers. To do so, we build on the analysis carried out recently by Le~Bris, Leli\`evre and Maday (Const. Approx. 30: 621--651, 2009) in the case of Poisson's equation on a rectangular domain in $\mathbb{R}^2$, subject to a homogeneous Dirichlet boundary condition, where they exploited the connection of the approximation method with the greedy algorithms from nonlinear approximation theory explored, for example, by DeVore and Temlyakov (Adv. Comput. Math. 5:173--187, 1996). We extend the convergence analysis of the pure greedy and orthogonal greedy algorithms considered by Le~Bris, Leli\`evre and Maday to the technically more complicated situation of the elliptic Fokker--Planck equation, where the role of the Laplace operator is played out by a high-dimensional Ornstein--Uhlenbeck operator with unbounded drift, of the kind that appears in Fokker--Planck equations that arise in bead-spring chain type kinetic polymer models with finitely extensible nonlinear elastic potentials, posed on a high-dimensional Cartesian product configuration space $\mathsf{D} = D_1 \times \dotsm \times D_N$ contained in $\mathbb{R}^{N d}$, where each set $D_i$, $i=1, \dotsc, N$, is a bounded open ball in $\mathbb{R}^d$, $d = 2, 3$. We exploit detailed information on the spectral properties and elliptic regularity of the Ornstein--Uhlenbeck operator to give conditions on the true solution of the Fokker--Planck equation which guarantee certain rates of convergence of the greedy algorithms. We extend the analysis to discretized versions of the greedy algorithms.

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Dissertations / Theses on the topic 'Polymer fluid'

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