Rheo-NMR Investigations of Flow and Alignment in Complex Fluids

<p>This thesis reports the use of Rheo-NMR, that is, a class of techniques within the realm of magnetic resonance which are both confirmatory and complementary to rheometric experiments on materials which can best be classified as complex fluids. The physical properties of such fluids are both hybrid and, in general, vaguely defined. In displaying characteristics attributable to both ideal fluids and elastic solids, the term `complex fluid', in a very real sense, epitomises all the fluids with which every human deals with (and is comprised of) daily. With a multitude of potential candidates for further research then, here we confine ourselves to fluids of molecules and aggregates which are either linear polymers or at least maintain the curvilinear one-dimensional topology of linear polymers. Magnetic resonance is an ideal research tool in this regard, as it is in many respects a rather statistical and insensitive tool from a signal-to-samplevolume perspective, precisely the regime in which the dynamics of a macroscopic collection of macromolecules is relevant. Material deformation is the mechanism upon which rheological measurement depends, and the first research presented here reports on a numerical simulation of the NMR signal of sheared polymer melts. Proton NMR relaxation times of such melts have previously been measured experimentally and found to depend on the shear rate applied by a horizontal Couette geometry, presumably due to the alignment of the mean-field boundaries of the space in which the polymer may reside, known as the polymer tube. The restrictions forming the tube are the other polymers in the bulk, around which an exemplar polymer molecule must meander. In diffusing through this tube, whose direction between entanglements is random in equilibrium, at any time, the return-to-origin correlation for a single spin returning to its locally anisotropic environment generates the least NMR transverse relaxation, as the sum contribution from all tube segments is random. When a deformation-related transformation matrix is applied to the coordinates of entanglements in the polymer, tube segments are no longer isotropically distributed, and an enhanced relaxation process results. Here we present the results of a numerical simulation of this procedure, based on the earlier model of Ball, Callaghan and Samulski, in addition to measurements of the transverse NMR relaxation by Cormier. Not only does it demonstrate qualitative agreement, the NMR signal can be simulated quantitavely or conversely, the size of several key polymer physics parameters can be found through fitting to the NMR signal. Proton NMR spectroscopy is inherently simpler than deuteron NMR spectroscopy, in which the nucleus of interest is quadrupolar. However, a large section of this thesis deals with the structures and response of worm-like micellar structures in solution, for which alignment data cannot reasonably be measured with the proton alone. The most used sample in this thesis is that of the BASF nonionic block copolymer Pluronic P105 in aqueous solution (5% w/w), and a small amount of 1-phenylethanol is required to stabilise cylindrical micellar structures. 1-phenylethanol is a small molecule perfectly suited to act also as a deuterated probe molecule to observe alignment, as it resides in the core of the micelle. By using a variety of Rheo-NMR techniques, such as velocimetry, spatially resolved spectroscopy, and diffusometry, many different flow and alignment behaviours were observed for this solution in Couette flow. Following the measured temperature-dependent viscosity of the P105 solution, which shows an elevated viscosity in a temperature region 15K wide centred at 297 K, we use temperature and applied shear rate as independent variables in our experiments, first identifying spectral features through diffusometry, and then observing a range of behaviours including shear-banding and quadrupolar splitting indicating alignment. Finally we present some experimental work performed in the extensional flow geometry known as the semi-hyperbolic converging die. Extensional flow, inherently, is a transient and nite procedure, and such a geometry is designed to produce a constant extension rate along the axis of its constricting pipe, which, compared to the mill geometries, improves the volume and time over which extension occurs. We investigate the flow and alignment measuring capabilities of Rheo-NMR in this geometry.</p>

Rheo-NMR Investigations of Flow and Alignment in Complex Fluids

<p>This thesis reports the use of Rheo-NMR, that is, a class of techniques within the realm of magnetic resonance which are both confirmatory and complementary to rheometric experiments on materials which can best be classified as complex fluids. The physical properties of such fluids are both hybrid and, in general, vaguely defined. In displaying characteristics attributable to both ideal fluids and elastic solids, the term `complex fluid', in a very real sense, epitomises all the fluids with which every human deals with (and is comprised of) daily. With a multitude of potential candidates for further research then, here we confine ourselves to fluids of molecules and aggregates which are either linear polymers or at least maintain the curvilinear one-dimensional topology of linear polymers. Magnetic resonance is an ideal research tool in this regard, as it is in many respects a rather statistical and insensitive tool from a signal-to-samplevolume perspective, precisely the regime in which the dynamics of a macroscopic collection of macromolecules is relevant. Material deformation is the mechanism upon which rheological measurement depends, and the first research presented here reports on a numerical simulation of the NMR signal of sheared polymer melts. Proton NMR relaxation times of such melts have previously been measured experimentally and found to depend on the shear rate applied by a horizontal Couette geometry, presumably due to the alignment of the mean-field boundaries of the space in which the polymer may reside, known as the polymer tube. The restrictions forming the tube are the other polymers in the bulk, around which an exemplar polymer molecule must meander. In diffusing through this tube, whose direction between entanglements is random in equilibrium, at any time, the return-to-origin correlation for a single spin returning to its locally anisotropic environment generates the least NMR transverse relaxation, as the sum contribution from all tube segments is random. When a deformation-related transformation matrix is applied to the coordinates of entanglements in the polymer, tube segments are no longer isotropically distributed, and an enhanced relaxation process results. Here we present the results of a numerical simulation of this procedure, based on the earlier model of Ball, Callaghan and Samulski, in addition to measurements of the transverse NMR relaxation by Cormier. Not only does it demonstrate qualitative agreement, the NMR signal can be simulated quantitavely or conversely, the size of several key polymer physics parameters can be found through fitting to the NMR signal. Proton NMR spectroscopy is inherently simpler than deuteron NMR spectroscopy, in which the nucleus of interest is quadrupolar. However, a large section of this thesis deals with the structures and response of worm-like micellar structures in solution, for which alignment data cannot reasonably be measured with the proton alone. The most used sample in this thesis is that of the BASF nonionic block copolymer Pluronic P105 in aqueous solution (5% w/w), and a small amount of 1-phenylethanol is required to stabilise cylindrical micellar structures. 1-phenylethanol is a small molecule perfectly suited to act also as a deuterated probe molecule to observe alignment, as it resides in the core of the micelle. By using a variety of Rheo-NMR techniques, such as velocimetry, spatially resolved spectroscopy, and diffusometry, many different flow and alignment behaviours were observed for this solution in Couette flow. Following the measured temperature-dependent viscosity of the P105 solution, which shows an elevated viscosity in a temperature region 15K wide centred at 297 K, we use temperature and applied shear rate as independent variables in our experiments, first identifying spectral features through diffusometry, and then observing a range of behaviours including shear-banding and quadrupolar splitting indicating alignment. Finally we present some experimental work performed in the extensional flow geometry known as the semi-hyperbolic converging die. Extensional flow, inherently, is a transient and nite procedure, and such a geometry is designed to produce a constant extension rate along the axis of its constricting pipe, which, compared to the mill geometries, improves the volume and time over which extension occurs. We investigate the flow and alignment measuring capabilities of Rheo-NMR in this geometry.</p>

Influences of Slenderness and Eccentricity on the Mechanical Properties of Concrete-Filled GFRP Tube Columns

The existence of either eccentricity or slenderness has a significant effect on the mechanical properties of a structure or member. These properties can change the working mechanism, failure mode, and bearing capacity of the structure or member. A concrete-filled, glass fibre-reinforced, polymer tube composite column has the same problem. We carried out experiments on the influences of eccentricity and slenderness on the mechanical properties of concrete-filled, glass fibre-reinforced, polymer tube composite columns. The experimentally recorded stress–strain relationships are presented graphically, and the ultimate axial stresses and strains and the FRP tube hoop strains at rupture were tabulated. The results indicate that the influences of slenderness and eccentricity on the composite columns were significant with regard to the axial strain, hoop strain, ultimate bearing capacity, lateral displacement, and failure mode. Based on the existing research literature and the results reported in this paper, the bearing capacity formula of a composite slender column under an eccentric load was established. The theoretical results were in good agreement with the experimental results.

COMPARISON OF 3-WEEK CALCANEAL TENDON REGENERATES AFTER TENOTOMY AND SUTURING IN EXPERIMENT IN VIVO

Background. Modern knowledge about tendon healing as well as possibilities of hand surgery does not solve the problem of tenogenic contractures. For the prevention of cicatricial process, the separation of the sliding surfaces of the tendon and its sheath with polymeric materials is used. However, regeneration of tendons in condition of isolation has not been proven. Aim of the research. In a laboratory animal model to perform a tenotomy and a calcaneal tendon suture, study 3-week regenerates formed in the mobilization regime and evaluate the regenerative capacity of the tendon isolated with a dissected polymer tube. Material and methods. On both paws of laboratory rats tenotomy and suturing of the calcaneal tendons were performed. The tendons on the right paws were isolated with dissected polymeric tubes. The appearance and the histological structure of the suture site were assessed after 3 weeks. Results. Tendon regenerates were distinguished by their maturity and tissue organization. Tendons without isolation healed faster, but lost their sliding surface. As a result of isolation, a sliding surface of the tendon and its sheath was formed, but the formation of the regenerate slowed down. Conclusions. Tendon healing in dissected tube is possible and occurs due to intrinsic repair. The fusion of the tendon demonstrates a well-vascularized regenerate in the suture site.

Perforation of the oesophagus in animals and methods of their treatment (сlinical case)

The purpose of the work was to research the etiological factors of perforation of esophagus, the clinical condition of animals, and also to perform a technique for surgical intervention to restore the function of the esophagus. The technique of operative access and the imposition of strong, airtight sutures was developed to contribute to the restoration of the esophagus function. The investigation object was three goats with bitten lacerations complicated by perforation of the esophagus in the cranioventral part of the neck, a horse with perforation of the esophagus in the middle part of the neck. The operating field in animals with damage of esophagus was prepared taking into account mechanical and chemical antiseptics, and local infiltration anesthesia was performed. The necrotic edges of the wounds excised, the skin dissected by 12-15 cm, and the neck muscles moved and separated in relation to each other, fixed with wound hooks and provided access to the perforated section of the esophagus. On the detected defects of the esophagus a polymer tube inserted into the cavity of the esophageal tube through the wound openings in the cranial direction until it exited the oral cavity by 10-15 cm, and then along the esophagus, than shifted towards the stomach. Thus, we obtained such a configuration and clear contours of the esophagus, which would facilitate the possibility of controlling the layer-by-layer application of surgical sutures and closing the perforation of the esophageal walls. The first level of Schmiden sutures applied to the mucous and muscle layers. Subsequently, for reliability three intermittent knotted seams imposed on the same layers. The second floor of the sutures – intermittent knotty was placed on the muscles and the adventitious layer of the esophagus (polymer suture material No. 4-6). Thus, a hermetic closure of the perforated defects of the esophagus was achieved. The wound was treated with antibacterial drugs and, first, an interrupted knotted suture was placed on the muscles and then on the muscles and skin. The resin tube removed through the oral cavity. In the postoperative period the neck was restricted in movement by applying wooden corsets for 5-6 days. The wound was treated with antibacterial drugs for 7 days. Feeding was carried out with chopped food, watering in small doses for two weeks. Regeneration of the operating wounds took place without complications due to primary intention. In 6-8 weeks after surgery the clinical condition of the animals was within normal limits, the animals were fed normally.

Mathematical modeling of chilling process of polymer tube billets

There are many works about producing of polymer tubes. But less attention is paid to the process of chilling of polymer products. The chilling of polymer tube billets, as most polymer processing processes, is a non-isothermal process. This means that it is necessary to solve the heat problem. Accurate calculation of the heat balance is one of the main components for the final result of the extrusion process. The mathematical model had been created for process of chilling of polymer tube billets after extrusion in this work. Several mathematical models of heating process for heat and power equipment have been created. Different calculation schemes, methods and equations for its solution are suggested. The mathematical model for process of chilling of polymer tube billets after it extrusion can be considered an expansion of research. The mathematical model is based on cylindrical coordinate system with assumption of axisymmetric along angular coordinate. The initial problem statement considered non-stationary process. A transition was made to the differential equation in partial derivatives along two linear coordinates. Solution of this equation was found using the operation method (Laplace integral transform method). The final solution of the problem (after direct and reverse Laplace transform) was obtained from the Bessel function. It was calculated in MathCAD with the help of built-in functions and computing modules. The mathematical model was created for modeling and optimization of process of chilling of polymer tube billets. The results of calculation were presented as graphs that make it possible to characterize the adequacy of the materials. Keywords: mathematical model, balance equation, Laplace transform, program block.

3D Investigation of Droplet Generation in a Miniaturized Coflowing Device Using Micro-Computed Tomography

For many applications, such as liquid-liquid or gas-liquid reactions, the generation of monodisperse droplets is of major interest. Therefore, knowledge about the physics of droplet formation is essential and the subject of numerous studies. Droplet formation is usually investigated using optical cameras, which makes optical accessibility necessary. Furthermore, properties defining droplet evolution is obtained from 2D images. In this work, we present a methodology for the 3D investigation of droplet formation in the laminar regime using micro-computed tomography. A special imaging concept and image processing, incorporating the use of a convolutional neural network, is presented. Water droplets are injected into a continuous polydimethylsiloxane stream in a coflowing configuration using a cannula with an inner diameter di = 800 μm and an outer diameter do = 1050 μm that is centered in a thin polymer tube with an inner diameter di = 1600 μm. Volume flow rates of polydimethylsiloxane and water are varied between 0.2 and 0.3 mL min−1. Furthermore, the influence of cannula positioning on droplet formation is investigated. Different quantitative 3D properties are extracted from the CT scans, such as droplet volume and surface of the interface. Thereby, different stages of droplet formation can be identified and the physical understanding of droplet formation is improved.