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1
Joseph, Sibichen. « Phase segregation in multi-component polymer systems ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/NQ41182.pdf.
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Teixeira, Roberto F. A. « Multi-layered nanocomposite polymer latexes and films ». Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/45871/.
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Clay platelets and silica nanoparticles are used as Pickering stabilizers in the fabrication of hybrid armored polymer particles through a Pickering emulsion polymerization process. A variety of hydrophobic comonomers (i.e., styrene-co- (n-butyl acrylate) (Sty:BA), methyl methacrylate-co-(n-butyl acrylate) (MMA:BA)), styrene-co-(2-ethyl hexyl acrylate) (Sty:2-EHA), vinyl acetate (VAc) and vinyl pivalate (VPiv) are used as organic film forming components. Polymerization kinetics and particle size distributions were examined as a function of monomer conversion. Additionally, key mechanistic features of the polymerization process by quantitatively analyzing the concentration of silica nanoparticles in the water phase during monomer conversion by disc centrifugation are unraveled. It is also showed the crucial role of Laponite clay discs in the particle formation (nucleation) of the Pickering emulsion polymerization process. Increasing amounts of clay nanodiscs leads to smaller average particles sizes, but broader particle size distributions. Polymer films of poly(styrene-co-n-butyl acrylate) armored with Laponite clay were studied as a function of clay amount. Improvements in mechanical, thermal and surface topography provided by clay platelets are reported. In addition, advantages are shown in use of hybrid polymer particles in comparison with simple blend mixtures of polymer particles plus inorganic particles. Humidity properties of poly(styrene-co-n-butyl acrylate) films as a function of clay content are investigated. It is demonstrated that the presence of Laponite clay improves the water storage capacity of polymer films. Also water barrier properties are improved when clay platelets are applied. Finally, a versatile two step Pickering emulsion polymerization for the fabrication of core-shell particles armored with Laponite clay XLS is developed. The obtained particles contain a "hard" core and a "soft" shell armored with clay. The different in the refractive indexes between the core and shell makes these core-shell particles interesting for possible use as colloidal crystals.
3
Chen, Tzu-Fan. « Multi-Walled Carbon Nanotubes-Modified Polymer Organic Photovoltaics ». TopSCHOLAR®, 2009. http://digitalcommons.wku.edu/theses/81.
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Since the carbon nanotubes were first discovered by Iijima in 1991, CNTs have been the focus of intense research by many groups. Nearly 7000 papers and 700 theses on carbon nanotubes can be found from the eminent journals such as Nature and Science in the last decade. Since carbon nanotubes show impressive mechanical, physical and electronic properties such as high stiffness, high strength, low density, and excellent thermal conductivity, suggesting its role in light-weight high strength material application. A great quantity of important research has evidently been done in this field. The purpose of this thesis research is to investigate the feasibility of MWCNTs for the application of polymer organic photovoltaics, and to study the formed MWCNTs-P3HT polymer nanocomposites properties, which are optical absorption, fluorescence emission, and morphology, as well as the formed photovoltaic device performance. This fundamental research would significantly contribute to the advanced technology development for how to improve the efficiency of the polymer organic photovoltaics.
4
Ivankovic, Alojz. « Rapid crack propagation in polymer multi-layer systems ». Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46837.
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5
Villechevrolle, Viviane Louise. « Polymer blends for multi-extruded wood-thermoplastic composites ». Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/v_villechevrolle_121008.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Mar. 2, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.
6
Kaneko, Wakako. « Studies on multi-functionalization of coordination polymer magnets ». 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136283.
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Asmaoglu, Serdar. « Synthesis And Charaterization Of Multi-hollow Opaque Polymer Pigmets ». Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614539/index.pdf.
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In the present work, a new generation opaque polymer pigment with multihollow structure was synthesized by suspension polymerization of &ldquoWater-in-Oil-in-Water&rdquo
(W/O/W) emulsion system. Oil phase was methyl methacrylate and ethylene glycol dimethacrylate monomer mixture at 1:1 weight ratio. The dimension and distribution of hollows inside polymer particles are dependent on the size of water droplets which are encapsulated in micelles. For Water-in-Oil (W/O) assembly, a hydrophobic surfactant and hydrophilic co-surfactant (Span 80-Tween 80) combination with a hydrophilic/lipophilic balance (HLB) value between 5-8 was used. The effects of surfactant and co-surfactant composition on the stability of the W/O emulsion and also on the size of water droplets were studied. In addition, the effect of the ultrasonication on the average size of water droplets was investigated. The hollow size distribution which may possibly give the maximum scattering efficiency was predicted by a mathematical model based on the Mie scattering. The optimum size distribution for W/O emulsion was obtained at the monomer/surfactant/water ratio of 75.5/9.4/15.1 after ultrasonication for 30 seconds at 80 W power. The W/O/W emulsion was prepared by dispersing the W/O emulsion in aqueous solution of hydrophilic Triton X-405. The influence of surfactant concentration and mechanical mixing on monomer droplets was investigated by size measurement and optical microscopy. After stabilizing with 1 %w/w polyvinylpyrrolidone (PVP) solution, the W/O/W emulsion was polymerized at 55 °
C for 20 h. The surface morphology of synthesized polymer pigments was analyzed by scanning electron microscopy (SEM) and the inner hollow structure was confirmed by transmission electron microscopy (TEM). The analysis indicated that multihollow opaque polymer pigments were successfully synthesized. The opacity, the L*a*b* color, and the gloss properties of polymer pigments were examined by spectrophotometer and glossmeter. The opacity values were assessed by contrast ratio measurements, and the synthesized polymer pigments provided up to 97.3 % opacity (50 %v/v solid content). In addition, the pigments exhibited low gloss values, and yielded matt films.
8
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.
9
Cresswell, Philip Thomas. « Multi-component stimuli-responsive polymer brushes grafted from flat surfaces ». Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633147.
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Grafting polymer brushes from surfaces is an effective method of surface modification. Importantly, such coatings are robust due to covalent bonding, establishing a chemically and mechanically stable interface not relying solely on weak physical bonding (e . g. van del' Waals forces) as alternative coating methods do. Polymer brushes have been shown to mediate effective lubrication, among other applications. In this work, stainless steel is the substrate of interest and a novel system of reagents specifically designed for this material has been applied to produce various polymer brush structures by surface initiated atom transfer radical polymerisation (SI-ATRP). For friction reduction in an aqueous environment, a multi-component hierarchical brush system, incorporating an underlying hydrophobic layer and a hydrophilic block on the outer periphery was proposed. The first layer of brushes, closest to the metals surface, was exploited as a barrier to drive water away from the solid interface, hence minimising corrosion of the metal, with the facile wetting of the second block giving a hydration layer at the interface to promote lubrication in the presence of water. Additionally, the hydrocarbon brush chosen as the outer layer in this system is known to be thermoresponsive, as chains collapse and become more hydrophobic at elevated temperatures. A co-polymer structure was employed and allowed the critical temperature of the brush to be tuned over a range of temperatures. This tuneable thermal response was intended to give switchable surface friction. Furthermore, use of an industrially relevant material in these investigations should potentially lead to a more straightforward utilisation in real world applications.
10
Xiao, Xiaoguang. « Multi-Scale Modeling and Simulation of Nanoparticles Reinforced Polymer Composites ». Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10812557.
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Over the years, the properties of nanoparticle-reinforced composites have been investigated regarding how the overall mechanical properties of the composites can be influenced by weight percentages, particle size, and types of reinforcement. The current advanced material processing technology allows people to obtain customized materials. However, making composite materials is usually costly and time-demanding, and some composite waste does not easily degrade. This computational study on composites provides a promising solution to these problems. In this research, a methodology of studying nanoparticle-reinforced polymer composites is developed, which allows the simulation of mechanical properties with multiscale computational approach. First, an RVE model of general nanoparticle-reinforced composites is constructed at nanoscale, and a computational study is made to examine the tensile behavior of the RVE on LS-DYNA. Second, a sensitivity study is conducted to optimize the mesh size with regards to simulation accuracy and computational time. Also, the model is validated by comparing the results from simulation with published data. Third, RVE models are applied to develop multiple models at microscale featured with various nanoparticles reinforcement dosages and orientation. In the end, data from tensile experiments on VGCNF are utilized to verify the models. It is found that using RVE models shortened the simulation times significantly while maintaining relatively high accuracy. Also, those models can be extensively applied to simulate various nanocomposites at multiple scales, which will fill the gap of simulation at between nanoscale and microscale.
11
Silberstein, Meredith N. « Mechanics and multi-physics deformation behavior of polymer electrolyte membranes ». Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67597.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 176-184).
Fuel cells are a developing technology within the energy sector that offer both efficiency and environmental advantages over traditional combustion processes. In particular, proton exchange membrane fuel cells (PEMFC) are promising for transportation and portable devices due to their low operating temperature, reduced C02 emissions, and scalability. A central component is the polymer electrolyte membrane (PEM) which conducts protons from the fuel source (typically either hydrogen or methanol) at the anode to the cathode where it reacts with oxygen while preventing the transport of either electrons or the fuel itself. Historically membranes have been designed primarily in terms of maximizing proton conductivity, but it is also important that they prevent fuel crossover and have minimal chemical and mechanical degradation over the target lifetime of the fuel cell. Membrane mechanical integrity is thus a critical concern for commercial distribution of PEMFC technology. This thesis has two primary focus areas: (1) characterization and modeling of Nafion, the benchmark PEM, in order to understand hygro-thermal loading in the existing technology and (2) mechanical characterization and modeling toward the development of an alternative polymer electrolyte membrane. These two areas are linked by the common technological application of low temperature fuel cells and can also be placed more broadly in the field of microstructurally and micromechanically informed constitutive modeling. The presulfonated polytetrafluoroethylene membrane Nafion is perhaps the most commercially prominent and widely studied polymer electrolyte membrane (PEM). Here Nafion is experimentally characterized first under monotonic and cyclic uniaxial tensile loading as a function of rate, temperature, and hydration. The data is used to develop a microstructurally motivated three-dimensional constitutive model. The Nafion model is validated under uniaxial tension for monotonic, cyclic, stress relaxation, and creep loading at various environmental conditions. Small and wide angle x-ray scattering characterization is then performed during uniaxial tensile testing in order to assign a microstructural interpretation to the mechanical behavior. The model is then validated for loading conditions which are expected to occur in the fuel cell, specifically, biaxial tension in the membrane plane and constrained swelling. Biaxial characterization is conducted via in-plane tensile testing of cruciform shaped specimens. The biaxial response is found to be qualitatively similar to the uniaxial response with the stiffness and strength in a given direction dependent on the degree of biaxiality. The constitutive model was shown to well predict this complex multiaxial deformation response when the model is implemented in the experimental geometry and reduced by the same methods as the experimental results. Biniaterial strip swelling of Nafion and typical gas diffusion layer material (GDL) is used to probe the partially constrained swelling behavior of Nafion. When the strip is hydrated the membrane swells causing the strip to curl with the membrane on the convex side until the force from the membrane is balanced by a moment in the GDL. Upon drying, plastic deformation that occurred during hydration induces a residual curvature of the opposite convexity. The hydrated and dried radii are found to agree with the finite element simulation predictions for two thicknesses of Nafion to within experimental error. Finally, the Nafion constitutive model is used to simulate a simplified fuel cell cycle. A negative hydrostatic pressure develops in the membrane upon drying, suggesting a driving force for cavitation or crazing. A study of the effect of ramp rate and hold time reveal a significant time dependence of the pressure, which is not surprising given the significant rate dependence observed for Nafion under uniaxial mechanical loading. Simulations of this nature are useful in guiding startup and shutdown procedures for fuel cells, for designing/validating potential procedures for accelerated lifetime testing, and for designing alternative fuel cell geometries. Focus is then shifted to the design of new polymer electrolyte membranes for direct methanol fuel cells (DMFC) which are a special case of PEMFC. DMFC operate under the same principal as PEMFC., however the fuel is liquid methanol rather than hydrogen. The high energy density of methanol makes DMFC particularly promising for portable applications where they could replace Li-ion batteries. In contrast to PEMFC, fuel crossover is a major design concern even when the membrane is fully intact. Given the multi-functionality of a DMFC PEM, it is natural to look to a composite solution. For the proton transport and fuel crossover resistance we use a chemistry and synthesis technique developed in the Hammond lab at MIT. This membrane is itself a composite of sulfonated Poly(2,6-dimethyl 1,4-phenylene oxide) (sPPO) and poly(diallyl dimethyl ammonium chloride) (PDAC) assembled via layer-by-layer (LBL) deposition. Unfortunately these films tear easily under dry conditions and are almost fluid like under hydrated conditions. The PDAC/sPPO membrane must therefore be combined with a mechanical support component. Here we use a highly porous and mechanically robust mat produced by electrospinning polyamide (EFM). In this thesis, focus is on the mechanical aspects of the design. A model for the mechanical behavior of the composite is developed based on experiments and models of the component materials. Uniaxial tensile tests are conducted on each of the materials (LBL, EFM, and LBL coated EFM) and the material morphology is examined via scanning electron microscopy where appropriate (EFM and LBL coated EFM). A micromechanically motivated constitutive model is then developed separately for the LBL and the EFM. The LBL model is a single mechanism elastic-plastic model that is highly hydration sensitive. The EFM structure is idealized as a layered triangulated network of elastic-plastic fibers. The behavior of the constituent fibers is taken to be elastic-plastic accounting for stretching and bending of the fibers when subjected to end tensile and compressive loads; the bending of the fibers when a fiber is locally under compression is found to be the key mechanism enabling the mat to consolidate during tensile loading. The layers of triangles impose mutual kinematic constraints emulating the layered structure of real mats, providing greater isotropy to the yield and post-yield behavior. A composite model is then developed as the superposition of the two materials. It is found that a composite model consisting of a weighted summation of the two component behaviors can capture the dry behavior. but not the hydrated behavior. In the hydrated state, the LBL, which is itself quite compliant under uniaxial loading, is found to inhibit fiber bending, thereby lending initial elastic stiffness and reducing post-yield hardening in a non-additive manner.
by Meredith Natania Silberstein.
Ph.D.
12
Feickert, Aaron James. « Multi-Scale Simulation Methods of Crosslinked Polymer Networks and Degradation ». Diss., North Dakota State University, 2018. https://hdl.handle.net/10365/28764.
Texte intégralRésumé :
Crosslinked thermoset polymers are used heavily in industrial and consumer products, as well as in infrastructure. When used as a protective coating, a thermoset's net-like structure can act as a barrier to protect an underlying substrate from permeation of moisture, salt, or other chemicals that otherwise weaken the coating or lead to substrate corrosion. Understanding how such coatings degrade, both at microscopic and macroscopic scales, is essential for the development and testing of materials for optimal service life. Several numerical and computational techniques are used to analyze the behavior of model crosslinked polymer networks under changing conditions at a succession of scales. Molecular dynamics is used to show the effects of cooling and constraints on cavitation behavior in coarse-grained bulk thermosets, as well as to investigate dynamical behavior under varying degradation conditions. Finite-element analysis is applied to examine strain distributions and loci of failure in several macroscopic coated test panel designs, discussing the effects of flexure and coating stack moduli. Finally, the transport of moisture through model coatings under cycled conditions is examined by lattice Boltzmann numerical techniques, considering several common concentration-dependent diffusivity models used in the literature and suggesting an optimal behavior regime for non-constant diffusivity.
13
Sato, Takeshi. « Transport Phenomena of Entangled Polymer Melts：A Multi-Scale Simulation Study ». Kyoto University, 2020. http://hdl.handle.net/2433/253310.
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Leamen, Michael. « Kinetic Investigation and Modelling of Multi-Component Polymer Systems with Depropagation ». Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/885.
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The phenomenon of depropagation or reverse polymerization for multicomponent polymerizations has been studied in detail. The monomer Alpha-Methyl Styrene (AMS) has been copolymerized with Methyl Methacrylate (MMA) and Butyl Acrylate (BA) at temperatures ranging from 60oC to 140oC and the kinetics have been studied in the form of propagation/cross propagation and depropagation parameters. There have been multiple attempts with varying amounts of success in the past to determine the kinetic parameters for depropagating systems including work by Lowry and Wittmer as well as other modelling methodologies that are not as mechanistic. The most recent development of the mechanistic terminal model is that of the Kruger model. The model is robust and can take into account all special cases as well as all reactions being reversible. The kinetic parameters have been estimated for each of the three binary systems using the Kruger model (MMA/AMS, MMA/BA, BA/AMS). The Alfrey-Goldfinger model is inadequate to describe depropagating terpolymer systems and in order to study them, a new model was developed based upon the binary Kruger model. This new model takes into account a fully depropagating terpolymer system leading to a total of 15 parameters to be estimated. These 15 parameters have the same definitions as those estimated from the binary Kruger model, thus making accurate analysis of the binary systems crucial since these will be used as first estimates for the terpolymer system. Extensive experimental data (composition, conversion and molecular weights) was collected and analysed for the MMA/AMS and BA/AMS systems. For the BA/AMS system both the bulk and solution copolymerizations were studied in detail with the results from the Kruger model not showing a significant difference in the reactivity ratios between the two types of polymerization. For the MMA/AMS system, a bulk study only was done which revealed an interesting phenomenon that points toward a break down of the long chain approximations used for all of the models being studied. For both of these systems, extensive 1H NMR analysis was done to determine the copolymer composition. Data collected in previous research for the MMA/BA system was reanalysed using the Kruger model and it was found that the parameter estimates did not differ significantly from the published values. Extensive benchmarking was done with the newly developed terpolymer model on non-depropagating systems using data from the literature to ensure it worked for the simplest cases. It was found that the model matched the parameter estimates from the literature and in some cases improving upon them to fit the data better. Along with the benchmarking a sensitivity analysis was done which revealed some interesting information. For the MMA/BA/AMS terpolymer system a set of experiments (based upon practical considerations) were performed and the composition of the polymer was determined using 13C NMR instead of the usual 1H NMR due to the difficulty of peak separation for the complex terpolymer. Using the depropagating terpolymer composition data in conjunction with the parameter estimates from the three binary systems allowed for estimation of the 15 kinetic parameters, which showed only minor variation from the binary estimates.
15
Kim, Yong-Jun. « Application of polymer/metal multi-layer processing techniques to microelectromechanical systems ». Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/14987.
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Stenzler, Joshua Saul. « Impact Mechanics of PMMA/PC Multi-Laminates with Soft Polymer Interlayers ». Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/36131.
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The main purpose of this thesis is the systematic, experimental investigation of how a soft interlayer affects the impact response and energy dissipation mechanisms of all-polymer multi-laminates. An instrumented, intermediate impact velocity experimental setup with strain rates on the order of 100 s-1, is used to assess the impact mechanics of three-layered samples consisting of a poly(methyl methacrylate) (PMMA) front, polymer interlayer or adhesive, and polycarbonate (PC) back layer. Instrumentation of the gas gun is achieved with a shock accelerometer measuring contact force and optical displacement sensors recording deflection. Previous impact research utilizing instrumented gas guns by Levy and Goldsmith, and Delfosse et al. have measured contact force, but did not record simultaneous out-of-plane displacement. Signals acquired are temporally aligned allowing for insight into the response of the multi-laminate during impact, which is inaccessible with typical gas guns.
Impact testing is completed on bonded and unbonded sample configurations, with two thermoplastic polyurethane and four polyacrylate interlayers. Quantitative metrics from force and displacement signals, along with post-impact damage observations, are used to compare impact performance between configurations and impact velocities (12 and 22 m/s). In general, the presence and bonding of an interlayer increases impact resistance by mitigating and localizing the impact load. The interlayers are characterized at various strain rates in tension, compression, and shear adhesion. In tension, all interlayers display rate dependence, non-linearity, and hysteretic behavior showing varying degrees of increasing energy dissipation with strain rate. Several trends between sample fracture and energy absorption mechanisms, quasi-static and low rate interlayer response, and metric results are established and discussed.Master of Science
17
Zhou, Tianhong. « Multi-compartment biodegradable polymer implants for intravitreal management of proliferative vitreoretinopathy / ». The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488186329502253.
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Mao, Jialin. « CHARACTERIZATION OF POLYMER ARCHITECTURES AND SEQUENCES BY MULTI-STAGE MASS SPECTROMETRY ». University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1554913939030297.
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Bavisi, Amit. « Integrated multi-mode oscillators and filters for multi-band radios using liquid crystalline polymer based packaging technoloy ». Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04062006-131113/.
Texte intégralRésumé :
Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.Swaminathan, Madhavan, Committee Chair ; Cressler, John D., Committee Co-Chair ; Kenney, Stevenson J., Committee Member ; Peterson, Andrew, Committee Member ; Durgin, Gregory, Committee Member ; Sitaraman, Suresh, Committee Member.
20
Chinnam, Parameswara Rao. « MULTI-IONIC LITHIUM SALTS FOR USE IN SOLID POLYMER ELECTROLYTES FOR LITHIUM BATTERIES ». Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/311780.
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ChemistryPh.D.
Commercial lithium ion batteries use liquid electrolytes because of their high ionic conductivity (>10-3 S/cm) over a broad range of temperatures, high dielectric constant, and good electrochemical stability with the electrodes (mainly the cathode cathode). The disadvantages of their use in lithium ion batteries are that they react violently with lithium metal, have special packing needs, and have low lithium ion transference numbers (tLi+ = 0.2-0.3). These limitations prevent them from being used in high energy and power applications such as in hybrid electric vehicles (HEVs), plug in electric vehicles (EVs) and energy storage on the grid. Solid polymer electrolytes (SPEs) will be good choice for replacing liquid electrolytes in lithium/lithium ion batteries because of their increased safety and ease of processability. However, SPEs suffer from RT low ionic conductivity and transference numbers. There have been many approaches to increase the ionic conductivity in solid polymer electrolytes. These have focused on decreasing the crystallinity in the most studied polymer electrolyte, polyethylene oxide (PEO), on finding methods to promote directed ion transport, and on the development of single ion conductors, where the anions are immobile and only the Li+ ions migrate (i.e. tLi+ = 1). But these attempts have not yet achieved the goal of replacing liquid electrolytes with solid polymer electrolytes in lithium ion batteries. In order to increase ionic conductivity and lithium ion transference numbers in solid polymer electrolytes, I have focused on the development of multi-ionic lithium salts. These salts have very large anions, and thus are expected to have low tanion- and high tLi+ transference numbers. In order to make the anions dissociative, structures similar to those formed for mono-ionic salts, e.g. LiBF4 and lithium imides have been synthesized. Some of the multi-ionic salts have Janus-like structures and therefore can self-assemble in polar media. Further, it is possible that these salts may not form non-conductive ion pairs and less conductive ion triplets. First, we have prepared nanocomposite electrolytes from mixtures of two polyoctahedral silsesquioxanes (POSS) nanomaterials, each with a SiO1.5 core and eight side groups. POSS-PEG8 has eight polyethylene glycol side chains that have low glass transition (Tg) and melt (Tm) temperatures and POSS-phenyl7(BF3Li)3 is a Janus-like POSS with hydrophobic phenyl groups and -Si-O-BF3Li ionic groups clustered on one side of the SiO1.5 cube. The electron-withdrawing POSS cage and BF3 groups enable easy dissociation of the Li+. In the presence of polar POSS-PEG8, the hydrophobic phenyl rings of POSS-phenyl7(BF3Li)3 aggregate and crystallize, forming a biphasic morphology, in which the phenyl rings form the structural phase and the POSS-PEG8 forms the conductive phase. The -Si-O-BF3- Li+ groups of POSS-phenyl7(BF3Li)3 are oriented towards the polar POSS-PEG8 phase and dissociate so that the Li+ cations are solvated by the POSS-PEG8. The nonvolatile nanocomposite electrolytes are viscous liquids that do not flow under their own weight. POSS-PEG8/POSS-phenyl7(BF3Li)3 at O/Li = 16/1 has a conductivity, σ = 2.5 x 10-4 S/cm at 30°C, 17 x greater than POSS-PEG8/LiBF4, and a low activation energy (Ea ~ 3-4 kJ/mol); σ = 1.6 x 10-3 S/cm at 90°C and 1.5 x 10-5 S/cm at 10°C. The lithium ion transference number was tLi+ = 0.50 ± 0.01, due to reduced mobility of the large, bulky anion and the system exhibited low interfacial resistance that stabilized after 3 days (both at 80°C). Secondly, solid polymer electrolytes have been prepared from the same salt, POSS-phenyl7(BF3Li)3 and polyethylene oxide (PEO). These exhibit high ambient temperature conductivity, 4 x 10-4 S/cm, and transference number, tLi+ = 0.6. A two-phase morphology is proposed in which the hydrophobic phenyl groups cluster and crystallize, and the three -BF3- form an anionic pocket, with the Li+ ions solvated by the PEO phase. The high ionic conductivity results from interfacial migration of Li+ ions loosely bonded to three -BF3- anions and the ether oxygens of PEO. Physical crosslinks formed between PEO/Li+ chains and the POSS clusters account for the solid structure of the amorphous PEO matrix. The solid polymer electrolyte has an electrochemical stability window of 4.6 V and excellent interfacial stability with lithium metal. In order to further enhance the ionic conductivity of solid polymer electrolytes, we have made two improvements. First, we have used so called half cube structures, T4-POSS, that contain 4 phenyl groups on one side of a Si-O- ring, and 4 ionic groups on the other side, and so are true Janus structures. They contain a 4/4 ratio of phenyl/ionic groups, unlike the previous structures that contain 7 phenyl groups/3 ionic groups. At the same O/Li ratio, the ionic conductivity of [PhOSi(OLi)]4 with POSS-PEG8 is higher than POSS-phenyl7Li3 because of more Li+ dissociation in the former case. Second, we have increased the dissociation of the lithium salts by replacing the Si-O-BF3Li groups with Si-(C3H4NLiSO2CF3)4. Both T4-POSS-(C3H4NLiSO2CF3)4 and POSS-(C3H4NLiSO2CF3)8 have been synthesized and characterized, with some preliminary conductivity data obtained.
Temple University--Theses
21
Jain, Ayush. « Development and Characterization of Multi-scale Polymer Composite Materials for Tribological Applications ». Thesis, Luleå tekniska universitet, Maskinelement, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65241.
Texte intégralRésumé :
With industries aiming at higher efficiencies, lightweight parts, and easier manufacturability there has been a recent trend of replacing the metallic materials with polymeric materials and its composites. Particularly in the automotive industry, there is a demand of replacing metallic material of bushes and bearings with polymer based materials (PBM). For these heavy performance requirements (as in automobiles), the commonly used industrial polymers like Acetal and Nylon fail to provide good mechanical and tribological performance. High-performance polymer like Polyphenylene Sulfide (PPS) is a relatively newer material and shows a potential of being a PBM alternative for metallic bearings in automobiles if their tribological performance can be improved. One of the ways of improving the tribological performance of the polymer is by the addition of filler material, hence making a polymer composite. In this study, we used Short Carbon Fibre as micro-reinforcement material and Nano-diamonds and Graphene Oxide as nano-reinforcement material to make PPS composites. The varying mechanical and tribological behaviour of PPS composites with different weight percentage of reinforcement materials was investigated. The optimum composition of the reinforcement materials was identified, which resulted in significant improvement in mechanical and tribological properties of the base material.
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Song, Mo. « Applications of modulated-temperature differential scanning calorimetry to multi-component polymer materials ». Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337256.
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Lidgett, Mark Jonathan. « Multi-scale modelling of polymer composite materials at high rates of strain ». Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/30888/.
Texte intégralRésumé :
The overall objective of this thesis was to develop a methodology for predicting the high strain rate properties of macro scale polymer composite materials through micro and meso scale finite element modelling. The focus in this study was on multi-layered multi-material polymer composite laminates consisting of 0/90 and ± 45 layers of either; S2 Glass/Epoxy or Carbon/Epoxy non crimp fabric. A multi-scale finite element modelling methodology was developed at the micro and meso scale for predicting the elastic response, damage initiation, damage evolution and strain rate dependence of macro scale polymer composite materials. The methodology was implemented in the Abaqus finite element package utilising Python scripting for simulation definition and Fortran code for user defined explicit material subroutines. Micro scale unit cells were tested in longitudinal, transverse and shear loading directions over a range of strain rates. The results of the micro scale testing were converted into material properties of the meso scale yarns / tows. Meso scale unit cells were tested in in-plane, through thickness and shear loading directions over of a range of strain rates. The results of the meso scale testing were converted into material properties of macro scale polymer composite materials. The modelling methodology was validated against experimental testing conducted on meso scale samples over a range of strain rates using an electromechanical universal static test machine and an instrumented falling weight drop tower. The contribution to knowledge from this study is the development of a validated modelling methodology for predicting the elastic, damage and strain rate dependent response of polymer composite materials at a micro and meso scale.
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Christke, Sandra. « Multi-layer polymer-metal laminate as fire protection for lightweight transport structures ». Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3348.
Texte intégralRésumé :
This study describes the development both of a new surface thermal insulation system, the experimental investigations into its fire protection mechanism and efficacy and a new thermal response modelling program. The use of multi-layer polymer metal laminates (PML) draws on the general principle common in conventional insulation methods, such as mineral-fibre and intumescent coatings, of immobilising high fractions of gas within the material and using the gas’ low thermal conductivity, harnessing the insulating effect. PMLs have the advantage over these systems in that they also form an integral part of the structure thereby contributing to the structural performance. With the view of taking this concept from laboratory scale to manufacture, material characterisation experiments were carried out to determine thermal and expansion characteristics of the PML material as these properties significantly influence fire performance. The PML FIRE model predicts the thermal response of PML-insulated substrates and was developed to take account of PML-specific effects such as expansion and foil melting. A series of small-scale fire tests were performed over wide heat flux ranges and on various PML designs, which included variations of PML ply numbers, foil thicknesses as well as the front face appearance, in order to gain insights into the PML fire protection mechanism and to validate the PML FIRE model. Fire-structural experiments on non-reactive and combustible PML-protected substrates commonly used in lightweight structures demonstrated the lower temperature transfer and the greatly improved structural resilience of the underlying substrate achieved. Good correlation of experimental and modelled temperature curves using PML FIRE has been obtained. The thermal state of specimens during heat exposure experiments up to structural failure can now be accurately predicted. Comparison of PML against other insulation methods illustrated the PML’s equivalent or superior behaviour in reducing underlying substrate temperatures and prolonging structural life during fire-structural testing.
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Çakir, Pinar. « Molecularly imprinted polymer nanostructures by controlled / living radical polymerization with multi-iniferters ». Compiègne, 2012. http://www.theses.fr/2012COMP2018.
Texte intégralRésumé :
Les polymères à empreintes moléculaires (MIPs) sont des matériaux synthétiques contenant des cavités capables de reconnaître spécifiquement une molécule cible. Ils se présentent comme une alternative intéressante face aux anticorps biologiques en raison de leur meilleure stabilité chimique et physique, leur meilleure disponibilité et leur moindre coût. Traditionnellement, les MIPs sont synthétisés par polymérisation de monolithes, qui sont ensuite broyés mécaniquement, engendrant des particules de taille micrométrique et de formes irrégulières. Durant ces dernières années, de nombreuses techniques de polymérisation ont été développées afin d’obtenir des particules MIP sphériques de tailles micro et nanométriques, et plus particulièrement des nanogels quasi-solubles. Dans l’optique d’une application en biologie, des tailles de quelques nanomètres - de l’ordre de grandeur de la taille des protéines – sont souhaitées, ce qui pose un réel défi pour leur synthèse, car la faible densité du matériau (une particule ne consiste que de quelques chaines de polymère) s'oppose à l'impression d'une mémoire moléculaire. Nous avons développé une nouvelle approche de synthèse de MIP nanogels dont la taille est proche de celle des anticorps naturels. Notre stratégie est basée sur l’utilisation d’un nouveau type d'amorceur pour la polymérisation radicalaire contrôlée comprenant des fonctions iniferter multiples attachées à un noyau dendritique. Cela permet de générer une concentration localement élevée de radicaux et ainsi, d'obtenir des nanogels de polymère dont la densité est augmentée. Ces travaux de thèse ont conduit à l’obtention des nanogels de MIP de 17 nm de diamètre avec un effet impression appréciable, une bonne affinité pour la cible, le beta-antagoniste propranolol, et une sélectivité moléculaire prononcée. En plus de la synthèse des nanogels solubles de MIP, des motifs de MIP micro et nanostructurés ont été greffés sur des surfaces planes de silicium. Le multiiniferter a été imprimé à la surface par lithographie douce, et fixé chimiquement par son groupement carboxyle central. Les MIPs ont ensuite été synthétisés par une approche « bottom up », caractérisés par spectroscopie d'émission optique, la spectroscopie Raman et la microscopie à force atomique, et la reconnaissance moléculaire de la cible a été visualisée par microscopie de fluorescence. Ces nouveaux matériaux, nanogels et surfaces imprimées offrent de nombreuses perspectives pour la détection par biocapteurs et biopuces, en particulier dans le domaine du biomédicalMolecularly imprinted polymers (MIPs) are synthetic materials with specific recognition properties for target molecules. They are considered an alternative to antibodies and are characterized by a higher chemical and physical stability, better availability and lower cost. Historically, MIPs were synthesized as bulk monoliths that were subsequently broken down mechanically in order to form particles of a size in the micrometer range, with irregular shapes. During the last decade, research has focused on the direct synthesis of spherical MIP micro and nanoparticles, and, more recently, on protein-sized, quasi-soluble MIP nanogels in order to widen the application range of MIPs in the biological field. The main difficulty of synthesizing MIPs with diameters in the low nm region is the low density of the resulting polymer network consisting only of a few polymer chains, which makes it difficult to imprint and maintain a molecular memory. In this thesis, we propose an original approach to the synthesis of quasisoluble MIP nanogels with a size in the low nm range, close to that of real antibodies. The proposed procedure involves a new type of initiator for controlled/living radical polymerization, based on multiple iniferter moieties attached to a dendritic core. This allows for the generation of a higher local radical density, and thus for the synthesis of denser nanogels. By using this strategy, MIP Nanogels of 17 nm size with an appreciable molecular imprinting effect, a good affinity for the target molecule, the chiral drug propranolol, and a good selectivity were obtained. In addition, these multiiniferters were also used for the bottom-up synthesis of thin MIP patterns on silicon wafers, by surface-initiated polymerization. The multi-iniferter was printed on to the surface by soft lithography and chemically attached through its carboxyl-functionalized core, followed by the in-situ synthesis of the MIP. Well defined MIP patterns were obtained, which were characterized by optical emission spectroscopy, Raman spectroscopy, atomic force microscopy, and the specific binding of the target molecule was visualized by fluorescence microscopy. We believe that the synthesis, in solution and at surfaces, of protein-size MIP nanogels with specific recognition properties will provide new opportunities for biosensors and biochips technologies in biomedical applications
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Njuguna, Michael Kamau. « Characterisation of multi wall carbon nanotube–polymer composites for strain sensing applications ». Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/54671/1/Michael_Kamau_Njuguna_Thesis.pdf.
Texte intégralRésumé :
Carbon nanotubes (CNTs) have excellent electrical, mechanical and electromechanical properties. When CNTs are incorporated into polymers, electrically conductive composites with high electrical conductivity at very low CNT content (often below 1% wt CNT) result. Due to the change in electrical properties under mechanical load, carbon nanotube/polymer composites have attracted significant research interest especially due to their potential for application in in-situ monitoring of stress distribution and active control of strain sensing in composite structures or as strain sensors. To sucessfully develop novel devices for such applications, some of the major challenges that need to be overcome include; in-depth understanding of structure-electrical conductivity relationships, response of the composites under changing environmental conditions and piezoresistivity of different types of carbon nanotube/polymer sensing devices.
In this thesis, direct current (DC) and alternating current (AC) conductivity of CNT-epoxy composites was investigated. Details of microstructure obtained by scanning electron microscopy were used to link observed electrical properties with structure using equivalent circuit modeling. The role of polymer coatings on macro and micro level electrical conductivity was investigated using atomic force microscopy.
Thermal analysis and Raman spectroscopy were used to evaluate the heat flow and deformation of carbon nanotubes embedded in the epoxy, respectively, and related to temperature induced resistivity changes. A comparative assessment of piezoresistivity was conducted using randomly mixed carbon nanotube/epoxy composites, and new concept epoxy- and polyurethane-coated carbon nanotube films.
The results indicate that equivalent circuit modelling is a reliable technique for estimating values of the resistance and capacitive components in linear, low aspect ratio-epoxy composites. Using this approach, the dominant role of tunneling resistance in determining the electrical conductivity was confirmed, a result further verified using conductive-atomic force microscopy analysis. Randomly mixed CNT-epoxy composites were found to be highly sensitive to mechanical strain and temperature variation compared to polymer-coated CNT films. In the vicinity of the glass transition temperature, the CNT-epoxy composites exhibited pronounced resistivity peaks.
Thermal and Raman spectroscopy analyses indicated that this phenomenon can be attributed to physical aging of the epoxy matrix phase and structural rearrangement of the conductive network induced by matrix expansion. The resistivity of polymercoated CNT composites was mainly dominated by the intrinsic resistivity of CNTs and the CNT junctions, and their linear, weakly temperature sensitive response can be described by a modified Luttinger liquid model. Piezoresistivity of the polymer coated sensors was dominated by break up of the conducting carbon nanotube network and the consequent degradation of nanotube-nanotube contacts while that of the randomly mixed CNT-epoxy composites was determined by tunnelling resistance between neighbouring CNTs.
This thesis has demonstrated that it is possible to use microstructure information to develop equivalent circuit models that are capable of representing the electrical conductivity of CNT/epoxy composites accurately. New designs of carbon nanotube based sensing devices, utilising carbon nanotube films as the key functional element, can be used to overcome the high temperature sensitivity of randomly mixed CNT/polymer composites without compromising on desired high strain sensitivity. This concept can be extended to develop large area intelligent CNT based coatings and targeted weak-point specific strain sensors for use in structural health monitoring.
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Khan, Ikram Ullah. « Microfluidic-assisted synthesis and release properties of multi-domain polymer microparticles drug carriers ». Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF042/document.
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Les caractéristiques et les propriétés de libération de microparticules chargées de médicament dépendent de la nature des matériaux employés, des propriétés physicochimiques des microparticules, du choix de la méthode de production, et enfin des propriétés des molécules encapsulées. A l'inverse de la plupart des méthodes conventionnelles, les méthodes microfluidiques présentent l’avantage de bien mieux contrôler la génération de gouttelettes, leur taille et leur distribution de tailles. Ainsi des dispositifs microfluidiques à base de capillaires ont été développés pour obtenir des microbilles de polymère mais également des microparticules de type janus, coeur-écorce ou troyenne, toutes monodisperses en taille et chargées de médicament(s). Ces particules ont été produites à partir de solutions de monomère qui furent polymérisées par irradiations UV de telle sorte à garder intacte l'activité des molécules chargées. Ces dispositifs peuvent être assemblés dans un court laps de temps et un simple changement dans leur conception permet d’obtenir des morphologies de particules très différentes. Ces particules ont été développées dans le but de résoudre les problèmes rencontrés dans l’administration orale de médicaments. Par exemple les microbilles peuvent être utilisées pour délivrer des anti-inflammatoires non stéroïdiens de manière continue tandis que les particules Janus peuvent libérer, simultanément et sur le même site, deux principes actifs possédant des propriétés complètement différentes (solubilité, compatibilité) également de manière prolongée. Quant aux particules coeur-écorce, elles ont été conçues pour cibler la région du côlon de l'intestin humain, et y libérer simultanément deux médicaments. Les particules troyennes furent synthétisées à l’aide d’un procédé microfluidique semi-continu qui a permis une manipulation plus sécurisée des nanoparticules vectrices ainsi que la libération continue d’un médicament dans un liquide gastrique simulé. Chaque système a été entièrement caractérisé pour assurer l’invariance entre lots et la reproductibilité. En général, la libération des ingrédients actifs a pu être facilement contrôlée/ajustée par le réglage des paramètres opératoires et de matériaux tels que les débits des différentes phases, la nature et la concentration du médicament, des (co)monomères, des agents tensioactif et de réticulation, le pH du milieu de libération. Ces différents paramètres influencent les propriétés des microparticules telles que leur morphologie, forme, taille et densité de réticulation du réseau polymèreCharacteristics and release properties of drug loaded microparticles depend upon material used and choice of production method. Conversely to most of the conventional ones, microfluidic methods give an edge by improving the control over droplet generation, size and size distribution. Capillary-based microfluidic devices were successfully used to obtain monodisperse drug(s) loaded microbeads, janus, core-shell and trojan particles using UV initiated free radical polymerization while keeping activity of active loaded molecules. These devices can be assembled in a short period of time and a slight change in design gives completely different microparticles morphologies. These particles were developed with the aim to address different issues experienced in oral drug delivery. For instance microbeads can be used to deliver NASIDs in a sustained release manner while janus particles can release two APIs with completely different properties (solubility, compatibility) also in a sustained release manner. Core-shell particles were designed to target colonic region of human intestine for dual drug delivery. Trojan particles were synthesized in a new semi-continuous microfluidic process, thus improving nanoparticles safety handling and release in simulated gastric fluid. Each system was fully characterized to insure batch to batch consistency and reproducibility. In general, the release of active ingredients was controlled by tuning the operating and material parameters like phases flow rates, nature and concentration of drug, (co)monomers, surfactant and crosslinker, pH of release media with the result of different particle morphologies, sizes and shapes or matrix crosslinking density
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Perdikoulias, John. « Analysis and design of annular dies for mono- and multi-layer polymer flows ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21380.pdf.
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Peng, Tao. « Permeability of responsive polymer-grafted porous membranes, temperature, pH and multi-stimuli response ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0020/NQ49832.pdf.
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Willemann, Michael Howard. « Polymer-Supported Bridges for Multi-Finger AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) ». Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/34801.
Texte intégralRésumé :
Current AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) make use of multiple sources, drains, and gates in parallel to maximize transconductance and effective gain while minimizing the current density through each channel. To connect the sources to a common ground, current practice prescribes the fabrication of air bridges above the gates and drains. This practice has the advantage of a low dielectric constant and low parasitic capacitance, but it is at the expense of manufacturability and robust device operation.
In the study described below, the air bridges in AlGaN/GaN HFETs were replaced by a polymer supported metallization bridge with the intention of improving ease of fabrication and reliability. The DC, high frequency, and power performance for several polymer step heights were investigated. The resultant structures were functional and robust; however, their electrical performance was degraded due to high source resistance. The cause of the high source resistance was found to be thinning of the metallization at the polymer step. The effect was more pronounced for higher step heights.Master of Science
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Greenhalgh, Kerriann R. « Development of biocompatible multi-drug conjugated nanoparticles/smart polymer films for biomedicinal applications ». [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002318.
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Rasmussen, Sarah Grace. « Synthesis and Characterization of Ferromagnetic Polymer-Coated Cobalt Nanoparticles in Multi-Gram Quantities ». Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/193433.
Texte intégralRésumé :
Ferromagnetic cobalt nanoparticles (CoNPs) are of interest due to their inherent dipolar properties which enable one-dimensional (1-D) nanoparticle self-assembly. As their magnetic properties change drastically with their size, the ability to selectively synthesize monodisperse metallic nanoparticles of varying diameters remains a crucial challenge. Although there have been extensive studies performed on various metallic nanoparticles yielding superparamagnetic materials (such as Fe3O4, Fe2O3, Co metals), research concerning the synthesis of ferromagnetic materials has only recently resurged within the last 20 years.In this work, methods for the synthesis of ferromagnetic cobalt nanoparticles on multi-gram scales were investigated. A one-pot synthetic method which produced up to 4 grams of cobalt nanoparticles per reaction was developed, and it was also found that this reaction had a direct correlation with particle size and reaction temperature, allowing for the large-scale synthesis of polystyrene-coated cobalt nanoparticles of pre-selected diameters.
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Al-Harbi, Nasser Munawir D. « Characterisation of complex polymer mixtures ». Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-complex-polymer-mixtures(be0269fe-2ac3-4128-ba57-4a03dbf46a7e).html.
Texte intégralRésumé :
The polymer of intrinsic microporosity PIM-1 was synthesized following various procedures: (i) from fluoro-monomer by the conventional method, (ii) from fluoro-monomer by a high temperature, high shear mixing method and (iii) from chloro-monomer. For a more complete understanding of the structure of the resultant products of a series of polymerizations under different reaction conditions, a multi-detector gel permeation chromatography (GPC) method was established and validated. A procedure for fractionating PIM-1 using chloroform methanol solvent mixtures was established and validated. A combination of multi-detector GPC and matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) masss pectrometry was used for the determination of molar mass distribution and to identify structural differences between fractions and between the products from different synthetic procedures. High molar mass samples tended to have broader molar mass distributions. Both Mark-Houwink plots and hydrodynamic volume plots showed deviation from linearity at Mw= 200000 g mol-1, which was attributed to branching. A low cost route for the preparation of PIM-1 from chloro-monomer was successfully established, though samples prepared by this route had broader polydispersities than those prepared from fluoro-monomers. It was found that stable flexible membranes were formed from samples with Mw > 83000 g mol -1. In addition, a comparison of two analytical methods for extraction and determination of additives in HDPE, LLDPE and PP polymers of interest to Saudi Basic Industries Corporation was performed. A comparison of dissolution with ultrasonic assisted extraction methods for the determination of anti-oxidant additives in polyolefins was performed. Ultrasound assisted extraction methods were found to be superior for HDPE and LLDPE, where conventional dissolution was preferred for PP.
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Rodriguez, John Israel 1972. « A multi-frequency induction heating system for a thermally triggered gel polymer dynamic vibration absorber ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87905.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 277-280).
Since its invention in the early part of the twentieth century, the dynamic vibration absorber (DVA) has played an important role in vibration suppression. In its simplest form, a dynamic vibration absorber is a mechanical network consisting of a spring, a mass and sometimes a damping element. These networks have been used to successfully reduce vibrations in buildings, bridges and imbalances in rotating machinery. Because these absorbers are most effective at attenuating disturbance near or at their self-resonant frequency, there is on-going research to develop semi-active DVA's capable of adjusting their natural frequency in real time. A new semi-active DVA is described that can modify its moment of inertia, and therefore its natural frequency, by using a collection of thermo-responsive gel polymers. This thesis develops an induction heating system that is suitable for noncontact heating of these gel polymers. The proposed heating system addresses the more general problem of controllable power delivery to multiple induction targets driven by a single induction coil. The focus of this work divides neatly between the design of the induction heating targets and the necessary power electronics. Targets that have preferential heating characteristics at particular frequencies are developed and analyzed. These targets include both resonant RLC circuits as well as conductors whose critical dimensions are much smaller than their associated skin depth. Extensive modeling of these targets is carried out and experimental results are presented. The ability to "selectively" heat these induction targets requires a power supply that can generate a sinewave with enough purity to not excessively heat unwanted targets.
(cont.) A 1 kW multilevel inverter topology is presented as an excellent compromise between total harmonic distortion and efficiency for this application. Referred to as the Marx inverter, this circuit can maintain its multilevel nature during real power transfer without the need for an external voltage balancing circuit or complicated control- unlike more traditional multilevel topologies. In addition to the gel vibration damper, portions of this work stand to benefit both medical and industrial venues where a desired temperature profile must be generated in a noncontact manner.
by John Israel Rodriguez.
Ph.D.
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An, Dechang. « Electro-optic polymer-based monolithic waveguide devices with multi-functions of amplification switching and modulation ». Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035933.
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Santi, Vasile Nicolò. « 3D multi-physics modelling and validation of the model of a Polymer Electrolyte Membrane Fuel ». Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2690105.
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This Ph.D. thesis focuses on testing and modelling PEMFC single cell systems, to better understand internal phenomena and to find out operative solutions able to increase the overall cell performance. Thus, the first step is based on the creation and validation of a wide spectrum of multi-physics models of PEMFC fed with hydrogen or methanol, by using Comsol® Multi-physics platform coupled with Matlab®.
All models are able to work under different operating conditions and with materials of different characteristics (membranes and catalysts). Moreover, the efforts were also focused on the creation of models of systems similar to fuel cell, as the gas diffusion electrode (GDE). The GDE is usually employed to analyze the electrochemical properties of the catalytic layer. Each single model was validated against a huge set of experimental data (partly obtained at POLITO, partly provided by the partners of two research projects: DURAMET and NAMEDPEM). After the model validation, these models were used to investigate the internal phenomena, and how materials, geometry and operative conditions affect the cell performance. Furthermore, particular problems affecting the entire FC system such as water flooding, methanol crossover, flow patterns design and current density distribution were deeply investigated to provide reasonable solutions.
In general, the 3D multi-physics, multi-component, multi-phase and not-isothermal models developed in this Ph.D. include Maxwell-Stefan, Navier-Stokes-Brinckman, and extended two-phase Darcy-law to solve velocity, pressure, and mass transfer equations, and modified Butler-Volmer and Tafel equations to describe the electrochemical kinetics. All the equations are coupled to each other to simulate the performance of a single cell PEMFC (or GDE), reproducing the electrochemical, fluid-dynamics, and thermal phenomena.
Each model was validated by comparing the simulated results, in terms of electric performance (polarization curves and power density curves), with experimental data obtained by changing several parameters:
-Type of membranes: Nafion® (N112, N115, N117), Fumapem® (F1850) for the DMFC, Nafion® (N-HP and NR-212) for the hydrogen-fed PEMFC.
-Dimensions of active area of the single cell: 5cm2 and 25cm2.
-Catalyst: eight different catalysts for the DMFC, four for the hydrogen-fed PEMFC, three for the GDE (commercial Pt/C, PtRu/C and lab-made FeNC-based catalysts).
-Operative conditions: pressure, methanol inlet concentration, air or oxygen at the cathode, cell and flow temperatures, anode and cathode flow rates, humidification and stoichiometric ratio (for the hydrogen-fed PEMFC).
-Flow field designs: unique serpentine, four parallel serpentines and four inlet serpentine.
After the validation, the models were used to reproduce and study the multi-dimensional trends of particular phenomena which produce system losses and/or affect the performance.
In first istance, the multi-physics analysis was used to improve the way to deposit the catalyst, thus the catalytic layer distribution was investigated in order to have a better uniformity in the current density distribution at the membrane/anodic catalyst interface. The proposed solutions, the 3-Layers MEA, was modelled in Comsol® and tested in the lab. It should avoid hot-spots on the membrane as a consequence of the better uniformity in the current density distribution, with a consequent increase in the life-time of the MEA (chapter I)
The second step was the analysis of the influence of water flooding and catalyst materials. The extended two-phase Darcy-law was used into the model to describe the mass transport inside the micro-porous structure of the noble/non-noble metal cathode catalyst, produced in our labs. The multi-physics analysis displays a direct relationship between the water saturation, the oxygen diffusion flow, and the oxygen consumption. Thus, water condensation inside the micro-pores may produce the flooding of micro and meso-porous, showing a consequent link between condensation and decreasing of cell performance (chapter II).
The third step of the multi-physics analysis was the study of the influence of FF design (unique serpentine, four parallel serpentines, four inlet serpentines.) and types of membrane on system performance. A large amount of lab tests and simulation were performed for each FF, by changing the temperatures, the inlet flow rates, the inlet methanol concentrations and the type of cathode flow. Pulse Field Gradient (PFG) NMR spectroscopy was used to get a direct measurement of the diffusion coefficients of water and methanol through the membranes. Thus, the model was used as a tool to investigate anodic overpotentials, water and methanol crossover flow rates, current density distribution along the membrane, understanding the relationship between the shape of the FF and cell performance (i.e. pressure and methanol consumption).(chapter III)
To improve the research on the area of catalyst properties, the study focused on the cathode using the gas diffusion electrode (GDE), trying to find out key parameters which influence the performance of catalysts for the oxygen reduction reaction. A commercial Pt-based catalysts and the non-noble metal Fe–N–C catalyst prepared in-house were tested and modelled, to carry out a sensitive analysis by varying the inlet oxygen flow rate, showing the influence of oxygen diffusive flow on the catalyst performance. The multi-physics analysis provides the way to increase the performance of the non-noble metal catalyst by changing some system properties as tortuosity, porosity and hydrophobicity (chapter IV)
After the large analysis developed for DMFC, the PhD work continued with the modelling of hydrogen-fed PEMFC, to complete, in such way, the general sensitivity analysis on PEMFC systems. Obviously, some innovations and changings were introduced to adapt the model with the new inlet fuel, as new equations and parameters for the electrochemical behaviours, initial and boundary conditions, H2 crossover and controlled parameters, i.e., relative humidity. The multi-physics analysis and the lab tests show how the relative humidity influence the performance, in relation to the variation of pressure and temperature (chapter V)
After the experimental and modelling studies, the PhD work was focused on several aspects, in order to improve the performance of the single cell with Fe-N-C catalyst on the cathode, related to material improvement and the single cell system: the active surface area, the percentage of micro-pores present in the catalytic layer, the membrane type, the procedure of catalyst deposition, the back pressure and the closing force. Thus, the modelling and lab work performed outcome in an excellent result: the system performance increases four times than the initial computed value, from about 10 mW cm–2 to 40.6 mW cm–2.
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Cattell, Melina Kay. « Static and fatigue flexural testing of polymer matrix glass fibre composites using a multi station fixture ». Thesis, University of Wolverhampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395193.
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Hölzer, Stefan Verfasser], Ulrich Sigmar [Akademischer Betreuer] [Schubert et Mario [Akademischer Betreuer] Beiner. « Structure-property relationships of polymer-based multi-phase systems / Stefan Hölzer. Gutachter : Ulrich Sigmar Schubert ; Mario Beiner ». Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://d-nb.info/1072621878/34.
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Hölzer, Stefan [Verfasser], Ulrich Sigmar [Akademischer Betreuer] Schubert et Mario [Akademischer Betreuer] Beiner. « Structure-property relationships of polymer-based multi-phase systems / Stefan Hölzer. Gutachter : Ulrich Sigmar Schubert ; Mario Beiner ». Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://d-nb.info/1072621878/34.
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Park, Soo Jeoung. « Photopolymerization-Induced Crystallization in Relation to Solid-Liquid Phase Diagrams of Blends of Blends of Poly(ethylene oxide)/Multi-functional Acrylate Monomers ». University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1218131827.
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Kienitz, Brian L. « The Effects of Cationic Contamination on Polymer Electrolyte Membrane Fuel Cells ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1228255795.
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Vickerstaffe, Emma. « The development and application of automated multi-step polymer assisted solution phase synthesis for the production of biologically active compound arrays ». Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614773.
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Sauerwein, Malte [Verfasser], et Holger [Akademischer Betreuer] Steeb. « Simulation of coupled transfer and transport phenomena in multi-phase materials with application to polymer gels / Malte Sauerwein ; Betreuer : Holger Steeb ». Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2021. http://d-nb.info/1237270731/34.
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WEGRZYN, MARCIN. « Nanocomposites of Multiphase Polymer Blend Reinforced with Carbon Nanotubes : Processing and Characterization ». Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/36869.
Texte intégralRésumé :
This thesis presents the study of nanocomposites based on immiscible
polymer blend of polycarbonate and acrylonitrile-butadiene-styrene
(PC/ABS) filled with multi-walled carbon nanotubes (MWCNT). The aim is to
achieve an improvement of mechanical properties and electrical conductivity
of the nanocomposites.
In an initial stage, a twin-screw extruder was used to obtain nanocomposites
by melt compounding. Three methods of carbon nanotubes addition were
studied: direct addition, dilution from a masterbatch and feeding of MWCNT
suspension in ethanol. For each method, the influence of nanofiller content
and processing parameters on morphology and final properties of the
nanocomposite was analyzed. Furthermore, the influence of two types of
carbon nanotubes modifications was studied: covalent modification by
surface-oxidation (MWCNT-COOH) and non-covalent modification by an
addition of surfactant promoting the nanofiller-matrix interactions.
A good dispersion of the MWCNT was obtained for masterbatch dilution and
suspension feeding. Both methods showed preferential localization of
carbon nanotubes in polycarbonate phase (PC).
Samples processed by masterbatch dilution showed the 30 % increase of
rigidity and a decrease of ductility of PC/ABS for 0.5 wt. % MWCNT.
Electrical conductivity was influenced by processing temperature and carbon
nanotubes type. The percolation threshold value was 2.0 wt. % for pristine
MWCNT and 1.5 wt. % for modified MWCNT-COOH.
Better balance of mechanical properties and electrical conductivity was
achieved in the samples obtained by the masterbatch route. These
properties were studied in a subsequent phase, when the extruded
nanocomposite was injection molded in order to obtain a defined geometry.Wegrzyn, M. (2014). Nanocomposites of Multiphase Polymer Blend Reinforced with Carbon Nanotubes: Processing and Characterization [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36869
TESIS
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Henke, M., et G. Gerlach. « A multi-layered variable stiffness device based on smart form closure actuators ». Sage, 2016. https://tud.qucosa.de/id/qucosa%3A35622.
Texte intégralRésumé :
This contribution describes the properties and limitations of multi-layered mechanical devices with variable flexural stiffness. Such structures are supposed to be components of new smart, self-sensing and self-controlling composite materials for lightweight constructions. To enable a proper stiffness control, reliable actuators with high actuation capabilities based on smart materials are used. Those actuators are either driven by electroactive polymers (EAPs) or shape memory alloy (SMA) wires. They control the area moment of inertia of the multi-layered bending structures. To change the area moment of inertia and, hence, the flexural stiffness of an multi-layered beam within a wide range, it is necessary to stack as many layers as possible over each other. The fundamental function of this approach is demonstrated with a three-layer stack consisting of three independent layers and four form closure actuators driven by SMAs. This experimental set-up was able to change its bending stiffness k by a factor of 14.6, with a minimum and maximum stiffness of kmin = 0.11 N mm¯¹ and kmax = 1.73 N mm¯¹, respectively. The usage of four independently controllable actuators yields nine independent flexural-stiffness states of the beam. Both analytical and numerical calculations have shown good agreement with the measured stiffness values.
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Philip, Long Nguyen. « Development of a Multi Radiation Type Survey Meter Using Aromatic Ring Polymers Undoped with Fluorescent Molecules ». Kyoto University, 2016. http://hdl.handle.net/2433/217749.
Texte intégralRésumé :
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第20066号
農博第2195号
新制||農||1045(附属図書館)
学位論文||H28||N5022(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 髙橋 千太郎, 教授 近藤 直, 教授 飯田 訓久
学位規則第4条第1項該当
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Subbaraman, Ramachandran. « A multi-scale hierarchical approach for understanding the structure of the polymer electrolyte membrane fuel cell (PEMFC) electrodes - from nanoparticales to composites ». online version, 2008. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=case1205852564.
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Subbaraman, Ramachandran. « A MULTI-SCALE HIERARCHICAL APPROACH FOR UNDERSTANDING THE STRUCTURE OF THE POLYMER ELECTROLYTE MEMBRANE FUEL CELL (PEMFC) ELECTRODES - FROM NANOPARTICLES TO COMPOSITES ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1205852564.
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Chauvin, David. « Réalisation d'un capteur optofluidique à champ évanescent à base de microrésonateurs polymères pour la détection ultrasensible d'espèces (bio)chimiques à haute toxicité ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN078/document.
Texte intégralRésumé :
La détection d'espèces (bio)chimiques à de très faibles concentrations représente un enjeu croissant dans les domaines de la santé, de l’environnement et de la défense. Un microrésonateur optique en polymère, sans marqueurs fluorescents, associé à un canal microfluidique, forme un capteur optofluidique, ce qui permet la détection d'analytes par interaction entre un champ évanescent à la surface du microrésonateur et la solution contenant l’espèce à étudier. Cette thèse présente la conception et la réalisation de capteurs optofluidiques à base de microrésonateurs optiques et de circuits microfluidiques en polymères, pour une très faible limite de détection et un temps de réponse rapide. De très bons résultats ont été obtenus en termes de limite de détection de polluants de type ions lourds dans l'eau, en abordant le problème sous différents angles : conception et réalisation de circuits optiques et microfluidiques, optimisation de l’interrogation optique du capteur par l’élaboration d’une méthodologie de mesure rapide et précise et un traitement du signal adéquat, étude des propriétés physico-chimiques des surfaces polymères, mise au point d’une instrumentation adaptée. Le capteur a permis la détection d'ions cadmium, ions hautement toxiques, jusqu'à une décision limite de détection de 50 pmol/L dans l'eau déionisée et 500 pmol/L dans l'eau du robinet grâce à un greffage sur la surface du microrésonateur de 2,2’- ((4-Amino-1,2-Phénylène) Bis (Carboxylatoazanédyil)) Diacétate. Une étude de régénération de la surface fonctionnalisée des microrésonateurs pour la détection d’ions cadmium a été réalisée et ce capteur a pu être régénéré pour plus de soixante mesures consécutives. D’autre part, l'analyse simultanée de deux polarisations orthogonales entre elles TE et TM de la réponse optique du capteur permet d’optimiser la sensibilité de mesure. Une étude de mesure différentielle consistant à comparer simultanément les mesures sur deux microrésonateurs identiques placés dans les même conditions physiques, l’un jouant le rôle de référence et l’autre étant un capteur spécifique, a permis de s’affranchir des différentes perturbations externes (pression, température, attachements non spécifiques). Ces instruments « multi-capteurs » sont également essentiels pour une compréhension détaillée des mécanismes de réactions de surface, une évaluation de l'efficacité d'accrochage de différents protocoles de fonctionnalisation et des mesures en multiplexageHigh sensitivity biochemical sensing is a concern for health, environment and defense. Thanks to the interaction between an analyte and an evanescent field at their surface, label-free polymer microring resonators, in association with a microfluidic channel, form an optofluidic sensor that can be used for biosensing. This thesis shows the realization of versatile optofluidic sensors based on polymer microring resonators combining a high detection limit with a short response time. High limit of detection of heavy ions in tap water was obtained after a careful optimization of the optical and microfluidic designs, signal processing, methodology of detection, surface chemistry and instrumentation. By functionalizing the resonator surface with 2,2’-((4Amino-1,2- Phenylene)Bis(Carboxylatoazanedyil))Diacetate, we obtained a limit of detection of 50 pmol/L in deionized water and 500 pmol/L in tap water. It should be stressed that the functionalized surface of the resonator was regenerated more than 60 times, enabling several sensing experiments with the same resonator. Besides, we were able to optimize the measurement sensitivity by an analysis of the orthogonal polarizations TE and TM from the sensor optical response. The simultaneous use of at least two microresonators in parallel (providing a reference signal and allowing multiplexing) enabled us to improve measurement accuracy and to compensate the signal from various external perturbations such as pressure, temperature and non-specific bindings. These “multi-sensors” are essential for (i) an in-depth understanding of surface reaction mechanism, (ii) an evaluation of the binding efficiency of different functionalization protocols and (iii) a high throughput characterization tool for multiple detections of pollutants
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Stradins, Linards. « Simulating the flow of multi-domain/multi-viscous polymer blends during polymer processing using the boundary element method ». 1993. http://catalog.hathitrust.org/api/volumes/oclc/32485953.html.
Texte intégralRésumé :
Thesis (M.S.)--University of Wisconsin--Madison, 1993.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 64-66).