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Preparation And Characterization Of Micron Size Serpentine Filled Abs CompositeAlakoc, Can Mustafa 01 November 2008 (has links) (PDF)
Micron size non-treated / silane coupling agent (SCA) treated serpentine filled acrylonitrile-butadiene-styrene (ABS) composite preparation and characterization of composites in terms of mechanical, thermal, flow properties and morphology were studied in this work. First step of the study was the size reduction of the as collected serpentine mineral. Secondly, three types of silane coupling agent treatments were applied to serpentine which were gamma-methacryloxypropyltrimethoxysilane (A-174), beta-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (A-186) and gamma-mercapto-propyltrimethoxysilane (A-189). Non-treated and three different types of SCA treated serpentine minerals were melt mixed with ABS. Non-treated serpentine filled ABS composites had the serpentine weight fractions of 2%, 5%, 10% and 20%. On the other hand, SCA treated ones had serpentine weight fractions of 2%, 5% and 10%.
Morphological analysis showed that SCA treatment was partly effective in interface interaction enhancement and A-186 gave the best results according to micrographs. There wasn& / #8217 / t any critical mechanical property loss up to 20% serpentine addition. Tensile tests revealed that SCA treatment increased the yield strength values of composites compared to non-treated serpentine filled composites. In accordance with morphological study, best result was obtained from 5% A-186 treated serpentine filled ABS as 12.9% improvement in yield strength value. Percent elongation at break values were increased with filler addition and greatest increase was observed in A-189 treated samples. Serpentine addition had no net effect on Young& / #8217 / s Modulus values. According to the impact testing results, A-189 treated samples had improved toughness compared to non-treated samples in accordance with elongation at break values. However increasing filler content resulted with decrease in impact strength values. DSC analysis showed that glass transion temperatures, especially for SCA treated samples, were decreased compared to neat ABS with filler addition. This result suggests that SCA may had the plasticizing effect on the composite. Flow properties of composites were not different from neat ABS up to 2% addition, when the filler concentration was further increased melt flow index values were dramatically decreased.
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Photo-oxidative Degradation Of Abs CopolymerGuzel, Aylin 01 September 2008 (has links) (PDF)
ABSTRACT
PHOTO-OXIDATIVE DEGRADATION OF ABS COPOLYMER
Gü / zel, Aylin
M.S., Department of Polymer Science and Technology
Supervisor: Prof. Dr. Teoman Tinç / er
Co-Supervisor: Prof. Dr. Cevdet Kaynak
September 2009, 55 pages
Acrylonitrile-butadiene-styrene (ABS) polymer is one of the most popular copolymer having an elastomeric butadiene phase dispersed in rigid amorphous styrene and semi-crystalline acrylonitrile. Due to double bonds in the polybutadiene phase, ABS copolymers are very sensitive to photo-oxidative degradation. Photo-oxidation of butadiene rubber phase results in the formation of chromorphores and these chromorphores act as initiators in photo-oxidative degradation and after a while ABS starts yellowing.
In this work, the relationship between the UV light and the yellowing of ABS samples was also investigated with respect to time. In this study, pure, light stabilized and commercial ABS samples were aged under UV light. As the UV light intensity increased from 800 to 2800 & / #61549 / W/cm2, yellowing of the samples were increased for pure ABS. This increase in yellowing of the samples was about 27 times higher compared to lower energy.
In this study, UV stabilizers IRGANOX 1076 (sterically hindered phenolic antioxidant), IRGAFOS 168 (hydrolycally stable phosphite stabilizer) and TINUVIN
P (hydroxyphenol benzotriazole) were used alone or in combination with each other. Pure ABS samples, commercial ABS samples and UV stabilized ABS samples were
aged under the same UV light. UV aging degradation was followed by measuring the yellowness of the samples at certain time intervals. Yellowness of the samples was followed by using Coloreye XTH Spectrometer. Degradation in ABS, however, was followed by using FTIR with an increase in the peak area of carbonyl groups in the ABS matrix.
Both color analysis and the FTIR analysis showed that combination of the IRGANOX 1076 and IRGAFOS 168 stabilizers gave the best stabilization. This revealed that combination of phenol and phosphate containing stabilizer is the most useful combination to prevent photo-oxidative degradation of ABS copolymer.
Additionally, vegetable oil was applied to the surface of a new set of ABS samples and these samples were aged for 700 h. Yellowing tendency of these samples was compared with the yellowing tendency of ABS samples that are directly aged for 500 h. It was clearly observed that samples with oil smeared had more resistance to UV radiation with respect to others. This shows that oil acts protective layer to the UV light and oxygen and slow down the photo-oxidative degradation.
Lastly some commercial ABS samples were compared to each other with respect to their yellowing tendency. Commercial ABS samples coded as K, L, A, B, C and D were aged under UV light at about 500 h. Sample A showed the best resistance against the yellowing among the other commercial ABS samples.
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Flame Retrdancy Effects Of Zinc Borate And Nanoclay In Abs / And Boron Compounds In PetOzkaraca, Ayse Cagil 01 July 2011 (has links) (PDF)
In this thesis there were two main purposes, the first one being to investigate effects
of zinc borate (ZB) on the flammability behavior of ABS when used with and
without a traditional brominated flame retardant (BFR) / antimony trioxide (AO)
system. The second purpose was to investigate contribution of nanoclays (NC) to the
flame retardancy performance of the same traditional BFR compound with various
combinations of AO and ZB again in ABS matrix.
For these purposes, materials were melt compounded by using a laboratory scale
twin-screw extruder, while specimens were produced by injection or compression
molding. Flame retardancy of the specimens were investigated by Mass Loss Cone
Calorimeter (MLC), Limiting Oxygen Index (LOI) measurements and UL-94 vertical
burning tests. Other characterization techniques required in this thesis were / X-ray
diffraction analysis, scanning and transmission electron microscopy,
thermogravimetric analysis and tensile tests.
Studies for the first purpose indicated that almost all flame retardancy parameters
were preserved when antimony trioxide were replaced with zinc borate as much as in
the ratio of 1:3. Residue analyses revealed that predominant flame retardancy
mechanism of traditional system was gas phase action, while zinc borate contributes
especially in the condensed phase action by forming thicker and stronger char layer.
Investigations for the second purpose basically concluded that use of nanoclays
improved all flame retardancy parameters significantly. Residue analyses pointed out
that nanoclays especially contribute to the formation of stronger and carbonaceoussilicate
char acting as a barrier to heat and flammable gases and retarding
volatilization via tortuous pathway.
As an additional third purpose in this thesis, usability of three boron compounds
(zinc borate ZB, boric acid BA, boron oxide BO) with two traditional flame
retardants (organic phosphinate OP and melamine cyanurate MC) in neat PET and
recycled PET were also examined leading to some promising results in MLC
parameters.
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Analytical techniques for quality assessment of separated and commingled recycled polymer fractionsCamacho, Walker January 2002 (has links)
<p>Different methods for quality assessment of separated andcommingled plastics from household and electronic waste havebeen developed. Especial attention has been given tospectroscopic methods since they are non-destructive andrequire little or no sample preparation at all.</p><p>A wide variety of low molecular weight compounds have beenidentified in recycled polyethylene (HDPE) and polypropylenefrom hard packaging waste by gas chromatography- massspectroscopy (GC-MS) after microwave assisted extraction (MAE).Low molecular weight substances such as alcohols, esters,ketones and fragrance and flavour compounds were detected inthe recycled resins. The major category of compounds identifiedin the virgin resins is conformed by aliphatic hydrocarbonssuch as alkanes and alkenes. It was found that theconcentration of aromatic hydrocarbons without functionalgroups, e.g. ethylbenzene and xylenes in recycled HDPE wasapprox. 5 times higher and equal to 120 and 35 ppb,respectively.</p><p>The potential of near infrared (NIR) and Fourier transformRaman (FT-Raman) spectroscopy in combination with multivariateanalysis as a rapid, non-destructive and accurate analyticalmethod has been studied and the feasibility of these methodsfor at/in line characterisation of several properties ofrecyclates has also been explored.</p><p>NIR in diffuse reflectance mode has been successfully usedfor quantification of antioxidants in polyethylene, thestandard error of prediction is almost comparable to the errorof wet methods, i.e., extraction plus liquid chromatography.The error of prediction of this method is 35 ppm for Irganox1010 and 68 ppm for Irgafos 168. The inaccuracy in thequantification of Irgafos 168 is due to the fact that thisantioxidant degrades during polymer processing.</p><p>NIR and Mid-infrared (Mid-IR) worked well for fastdetermination of molecular weight and crystallinity of therecycled HDPE and acceptable errors of prediction, comparableto that of the reference methods, i.e. size exclusionchromatography (SEC) and differential scanning calorimetry(DSC) have been obtained.</p><p>The present thesis also shows that NIR and Raman are goodcandidates for in/on line compositional analysis of mixedpolymer fractions from recycled plastic waste. Diffusereflectance NIR allows a rapid and reliable measurement ofpellets and requires no previous sample preparation. Thecomposition of binary blends can be determined with highaccuracy. The PP content in the PP/HDPE blends was predictedwith a RMSEP equal to 0.46 %w in the 0-15 %wt region and theRMSEP for PP in the PP/ABS blends was 0.3 %wt.</p><p>The thermal and thermoxidative stability of recycled PP,HDPE and a 20/80 PP/HDPE blend subjected to multiple extrusionhave been studied by DSC, thermal analysis (TGA) andchemiluminiscence (CL). A decrease in T<sub>ox</sub>and OIT was observed after each extrusion step.The drop in OIT was sharper after the first two extrusions. TheOIT values produced by DSC and CL were in good agreement.However, CL provided more information about the oxidationprocess taking place in the blends.</p><p>The moisture content in recycled polyamide 6,6 was readilydetermined by NIR in transmission mode and it could bepredicted with a RMSEP = 0.05 %wt. The accuracy of the methodappeared to be as good as that of the more time consumingthermal methods such as TGA, DSC and loss on dry (LOD), whichwere used as reference methods. The influence of differentamounts of water on the viscoelastic properties of nylon hasbeen investigated.</p><p><b>Keywords:</b>Recycling, HDPE, PP, blends, nylon 6,6, ABS,water content, MAE, GC-MS, NIR, FT-Raman, chemiluminiscence,low molecular weight compounds, antioxidant content,crystallinity, molecular weight, thermal stability,characterisation methods, analysis of polymers, blends.</p>
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Simulation of Piecewise Smooth Differential Algebraic Equations with Application to Gas NetworksStreubel, Tom 10 June 2022 (has links)
Zuweilen wird gefördertes Erdgas als eine Brückentechnologie noch eine Weile erhalten bleiben, aber unsere Gasnetzinfrastruktur hat auch in einer Ära post-fossiler Brennstoffe eine Zukunft, um Klima-neutral erzeugtes Methan, Ammoniak oder Wasserstoff zu transportieren.
Damit die Dispatcher der Zukunft, in einer sich fortwährend dynamisierenden Marktsituation, mit sich beständig wechselnden Kleinstanbietern, auch weiterhin einen sicheren Gasnetzbetrieb ermöglichen und garantieren können, werden sie auf moderne, schnelle Simulations- sowie performante Optimierungstechnologie angewiesen sein. Der Schlüssel dazu liegt in einem besseren Verständnis zur numerischen Behandlung nicht differenzierbarer Funktionen und diese Arbeit möchte einen Beitrag hierzu leisten.
Wir werden stückweise differenzierbare Funktionen in sog. Abs-Normalen Form betrachten.
Durch einen Prozess, der Abs-Linearisierung genannt wird, können wir stückweise lineare Approximationsmodelle erster Ordnung, mittels Techniken der algorithmischen Differentiation erzeugen.
Jene Modelle können über Matrizen und Vektoren mittels gängiger Software-Bibliotheken der numerischen linearen Algebra auf Computersystemen ausgedrückt, gespeichert und behandelt werden.
Über die Generalisierung der Formel von Faà di Bruno können auch Splinefunktionen höherer Ordnung generiert werden, was wiederum zu Annäherungsmodellen mit besserer Güte führt.
Darauf aufbauend lassen sich gemischte Taylor-Kollokationsmethoden, darunter die mit Ordnung zwei konvergente generalisierte Trapezmethode, zur Integration von Gasnetzen, in Form von nicht glatten Algebro-Differentialgleichungssystemen, definieren.
Numerische Experimente demonstrieren das Potential.
Da solche implizite Integratoren auch nicht lineare und in unserem Falle zugleich auch stückweise differenzierbare Gleichungssysteme erzeugen, die es als Unterproblem zu lösen gilt, werden wir uns auch die stückweise differenzierbare, sowie die stückweise lineare Newtonmethode betrachten. / As of yet natural gas will remain as a bridging technology, but our gas grid infrastructure does have a future in a post-fossil fuel era for the transportation of carbon-free produced methane, ammonia or hydrogen.
In order for future dispatchers to continue to enable and guarantee safe gas network operations in a continuously changing market situation with constantly switching micro-suppliers, they will be dependent on modern, fast simulation as well as high-performant optimization technology. The key to such a technology resides in a better understanding of the numerical treatment of non-differentiable functions and this work aims to contribute here.
We will consider piecewise differentiable functions in so-called abs-normal form.
Through a process called abs-linearization, we can generate piecewise linear approximation models of order one, using techniques of algorithmic differentiation.
Those models can be expressed, stored and treated numerically as matrices and vectors via common software libraries of numerical linear algebra.
Generalizing the Faà di Bruno's formula yields higher order spline functions, which in turn leads to even higher order approximation models.
Based on this, mixed Taylor-Collocation methods, including the generalized trapezoidal method converging with an order of two, can be defined for the integration of gas networks represented in terms of non-smooth system of differential algebraic equations.
Numerical experiments will demonstrate the potential.
Since those implicit integrators do generate non-linear and, in our case, piecewise differentiable systems of equations as sub-problems, it will be necessary to consider the piecewise differentiable, as well as the piecewise linear Newton method in advance.
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Nanocomposite auf Basis elektrisch leitfähiger und nicht leitfähiger Füllstoffe und deren Verwendung in zähmodifizierten PolymerblendsMeincke, Olaf. Unknown Date (has links) (PDF)
Universiẗat, Diss., 2003--Freiburg (Breisgau).
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Obtenção e estudo de blendas poliméricas de ABC com copolímero em bloco SBSRossato, Jéssica Helisa Hautrive January 2016 (has links)
Orientador: Prof. Dr. Gerson Luiz Mantovani / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2016. / Blendas de poli(acrilonitrila-estireno-butadieno) (ABS) com modificadores de impacto tipo estireno-butadieno-estireno (SBS) foram obtidas para melhorar ainda mais a resistência ao impacto e melhorar a processabilidade de determinados tipos de ABS. Neste trabalho o objetivo foi à obtenção de blendas ABS/SBS e a investigação do comportamento de resistência ao impacto em função da temperatura. As blendas foram obtidas por extrusão de três diferentes tipos de ABS com diferentes conteúdos de SBS. Foram caracterizadas as propriedades de fluxo, as propriedades reológicas, as propriedades mecânicas e a morfologia de fratura dos materiais obtidos. Concluiu-se que não ocorreu a tenacificação do ABS com adição dos conteúdos de SBS, com exceção das blendas ABS 1 com mais de 10% em massa de SBS. Isto mostrou a influência das características e da composição dos ABS e do SBS, e do processamento no comportamento mecânico e na morfologia obtida pela blendas, além da influência do conteúdo em massa de SBS adicionado. As análises das morfologias de fratura mostraram que as blendas de ABS 1 com mais de 10% em massa de SBS possuem um tamanho de partículas menor que nas blendas ABS 2/SBS e ABS 3/SBS, e também uma melhor distribuição das partículas. Nos resultados dos ensaios de tração notou-se um aumento no alongamento na ruptura com o aumento do conteúdo de SBS nas blendas, com uma pequena diminuição do módulo de elasticidade e na tensão no escoamento. Porém, a adição do copolímero em bloco fez com que houvesse uma melhora na processabilidade nas blendas que foi observado nos ensaios de MFI, reometria capilar e reometria de torque. / Blends of poly(acrylonitrile-styrene-butadiene) (ABS) with impact modifiers type styrene-butadiene-styrene (SBS) were obtained to further improve the impact resistance and improving processability of certain types of ABS copolymer. In this work, the objective was to obtain of ABS/SBS polymer blends and the investigating the behavior of the impact resistance versus temperature. The blends were extruded from different types of ABS with different SBS content. Were characterized the flow properties, rheological properties, mechanical properties and fracture morphology of the materials. Concludes that there wasn¿t toughening of ABS with addition of SBS content, except ABS 1/SBS blends with more than 10 w.t% of SBS. This showed the existence dependency characteristics and composition of ABS and processing in the mechanical behavior and morphology of the blends obtained, besides the influence of the content of SBS added. The analysis of fracture morphology showed that blends of ABS 1 copolymer with more than 10 w.t% of SBS having a less particle size than in the ABS 2/SBS blends and ABS 3/SBS blends, and better distribution of the particles. In the results of tensile tests were noted an increase in elongation at break with increasing content of SBS in the blend, with a small decrease in the elastic modulus and yield strength. However, the addition of block copolymer had caused an improvement in processability in the blends, which was observed in the MFI tests, capillary rheometer and torque rheometer.
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Preparação e caracterização de blendas de PANI/ABSCristovan, Fernando Henrique 16 March 2009 (has links)
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Previous issue date: 2009-03-16 / Financiadora de Estudos e Projetos / Polyaniline (PANI) chemical synthesis was monitored in situ by means of electrochemical impedance, open circuit potential (Voc) and mass variation. We verify that the final properties of the polymer could be practically defined after inflection point in the potential profile. The impedance data were decisive to understand this behavior, showing only a small change after inflection point. Impedance results and mass
variations during the synthesis contributed to understand the induction mechanisms that occur in the initial stages of the polymerization process. Also, it was performed an investigation on the influence of different variables (temperature, monomer:oxidant molar ratio, oxidant, pH value, use of inert salts at high concentrations) in the PANI chemical synthesis process as well as in its physicochemical properties. In this work, it was estimated the characteristic points of PANI through the Voc measurements during the chemical synthesis, based on an experimental design methodology. This methodology allowed an efficient mapping of PANI synthesis process as well as its interactions with each variable previously described. The results indicated that the oxidant employed in the synthesis influences in the final chemical and physical properties of this polymer. The studies performed on the final properties of PANI were the degree of oxidation and electric resistivity. Moreover, the yield the degree of
polymerization was also evaluated. The experimental design methodology was also used in order to understand the
influence of the preparation conditions on the final properties of the blends in poly(acrylonitrile-butadiene-styrene) (ABS) and polyaniline obtained by the co-dissolving components in a common organic solvent. The variables evaluated were the PANI content in the blend, m-cresol:chloroform rate (solvent ratio), dopant (DBSA or CSA) and acrylonitrile content in the ABS. The results showed that these variables are able to
change significantly the flexibility and electric conductivity of the blends. On the other hand, the dopant used mainly influences in the conductivity, suggesting that the DBSA is
the better for the development of PANI/ABS blends more conductive. After better prepare conditions of the blends, the percolation threshold was established at around 3 wt% of PANI, forming a flexible blend with conductivity of approximately 3 S.cm-1. The optical properties of the blend films were characterized by UV Vis-NIR. The conduction mechanisms of the blends were investigated using a dc
electric conductivity in the range from 80 to 320 K. Using the Mott s theory, it was found that the conductivity in the blends is a threedimensional variable range hopping mechanism. The Mott s temperature values, density of states at the Fermi energy, average hopping distance and barrier height for the blends were calculated and discussed in this work. Also, two possible technological applications were proposed to the PANI/ABS system, including: composite varistors and antistatic or electromagnetic protection of electronic devices. The varistors were prepared with 30% of PANI, which showed a low rupture voltage at around 10 V and a non linearity coefficient of approximately 9,2. On the paint shape and when deposited on cardboard, this material can be employed as protector system of electronic devices. Another important characteristic is the conductivity of this material, which is controlled by the number of paint layers deposited on the cardboard. / A síntese química da polianilina (PANI) foi monitorada in situ por meio das técnicas de impedância eletroquímica, potencial de circuito aberto (Voc) e variação de massa. Foi detectado que as propriedades finais do polímero são definidas logo após o do máximo da curva de Voc e antes do platô final. Os dados de impedância foram decisivos para o entendimento desta característica, apresentando somente uma pequena variação depois do máximo de Voc. Os dados de impedância e variação de massa durante a síntese também contribuíram para a compreensão dos processos que ocorrem durante o período de indução da síntese da PANI. Em seguida, foi feita uma investigação da influência das variáveis de síntese tais como: temperatura, razão monômero:oxidante, tipo de agente oxidante, pH e o uso de LiCl na síntese química da PANI, bem como nas propriedades físico-químicas do polímero obtido. Para avaliar as influências destas variáveis na síntese da PANI foi utilizada a técnica de Voc e para avaliar pontos característicos foi empregada a metodologia de planejamento fatorial. Esta técnica permitiu estabelecer um rápido e compreensivo mapeamento do processo de síntese da PANI, e a importância de cada variável bem como suas interações. A variável que mais influenciou em todos os estágios do processo foi tipo de agente oxidante. Depois, foram estudas as
propriedades finais do polímero tais como grau de oxidação e resistividade elétricas. O rendimento de polimerização também foi avaliado, todas estas respostas também foram avaliadas utilizando um planejamento fatorial que, por sua vez, mostrou que a variável que mais influencia nas propriedades finais do polímero é o tipo de agente oxidante. Em um segundo momento, foram estudadas as influências das condições de
preparo das blendas de PANI com o poli(acrilonitrila-butadieno-estireno) (ABS) preparadas pelo método de codissolução de ambos os componentes em um solvente comum através de um planejamento fatorial. As variáveis estudadas foram: quantidade de PANI nas blendas, razão m-cresol;clorofórmio, tipo de dopante (DBSA ou CSA), concentração de dopante e teor de acrilonitrila no ABS. As respostas monitoradas
foram a flexibilidade e a condutividade elétrica das blendas obtidas. Os resultados mostraram que a quantidade de PANI nas blendas e o teor de acrilonitrila no ABS foram as variáveis que mais influenciaram em ambas as respostas. O tipo de dopante mostrou somente influência na resposta condutividade, onde o DBSA se mostrou o melhor dopante para se obter blendas de PANI/ABS mais condutoras. Depois das melhores condições de preparo estabelecidas, o limite de percolação do sistema foi determinado, onde o valor estimado foi de 3% em massa de PANI na blenda, apresentando uma
condutividade de 3 S.cm-1. Para se compreender o mecanismo de condutividade das amostras, foi feito um estudo da condutividade DC das blendas no intervalo de
temperatura de 80-320 K. Os dados foram tratados aplicando a teoria de Mott, onde o mecanismo de condutividade obedece ao modelo de Saltos de Tamanhos Variáveis em
três dimensões, e os parâmetros de Mott foram estimados.
Duas aplicações para o sistema PANI/ABS foram propostas. Onde preparados compósitos varistores de PANI/ABS, sendo que o material preparado com 30% de PANI apresentou uma tensão de ruptura de aproximadamente 10 V e um coeficiente de não linearidade de 9,2, com estes valores o compósito pode ser utilizado na proteção de equipamentos eletrônicos. Na outra aplicação proposta neste trabalho, foi preparada
uma tinta de PANI-DBSA/ABS, que foi depositada sobre papelão, a resistência elétrica do material pode ser controlada pelo número de camadas de tinta. Deste modo o material pode ser utilizado na proteção antiestática e eletromagnética também de componentes eletrônico.
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A Study on Investment and Financing Model of Urban Rail ——With Case Study on Metro Rail Transit in city A, ChinaJanuary 2018 (has links)
abstract: As an alternative to the traditional public transportation system, (urban) rail transit has many advantages such as large capacity, fast speed, tight schedule, safety and comfort, and punctuality, , and has gradually become a top choice of many cities in countering environmental pollution and optimizing traffic quality. At the same time, we must also see that huge amounts of capital are required for the construction of rail transit. The traditional reliance on government investment clearly has its own limitations. The investment not only has a long cost-recovery cycle and a low rate of return, but also hardly attracts investments from the private sector. Therefore, when the government vigorously promotes the construction of a rail transit system, it is generally faced with problems such as a large funding gap and an overall financial loss. Therefore, how to establish a reasonable and efficient mode of investment and financing and further broaden the financing channels for rail transit projects is of great practical significance for improving the profitability of rail transit enterprises and realizing the sustainable development of rail transit. This thesis attempts to study the issue, in general, and further exmines a detailed case study of metro rail transit in a Chinsese city (city A), in particular.
The thesis first studies the concept and attributes of urban rail transit, and analyzes four modes and corresponding cases of urban rail transit investment and financing., It then discusses the characteristics of investment and financing of urban rail transit projects and the concept of investment and financing. Moreover, this thesis focuses on the current situation, characteristics and challenges of city A’s rail transit construction,. More specifically, it takes an in-depth look at the financial planning, investment and financing planning and the investment and financing channels products. The study innovatively puts forward three models, namely, PPP, TOD, ABS of rail transit investment and financing products. Based on the AHP decision-making method, the study shows PPP as the optimal integrated choice for city A. Finally, based on the core issues of the domestic urban rail transit project investment and financing, this thesis analyzes the rationality of the PPP model thoroughly and comes up with some managerial and policy suggestions on how to further optimize the investment and financing of the urban rail transit construction from the perspectives of the government management and the rail transit enterprises / Dissertation/Thesis / Doctoral Dissertation Business Administration 2018
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Estudo da tenacidade à fratura por meio do método do trabalho essencial de fratura (EWF) da blenda PBT/ABS, reforçada com fibra de vidro / Study of the fracture toughness by essential work of fracture method (EWF) of glass fiber reinforced PBT/ABS blendsRazzino, Carlos do Amaral 05 June 2008 (has links)
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Previous issue date: 2008-06-05 / Financiadora de Estudos e Projetos / High rubber content acrylonitrile-butadiene-styrene terpolymer (ABS) has been used to tough PBT. As a result, super tough PBT/ABS blends under notched Izod impact have been obtained. However, there has been a significant reduction in the PBT/ABS Young modulus. The development of an optimum stiffness-toughness balance in PBT/ABS blends can be achieved by addition of short glass fibers to the composite blends. The composite performance is strongly dependent on the matrix-fiber interface and consequently the surface treatment of the fiber is a key factor to be considered. In the present work, the effect of two kinds of glass fibers treatment on the mechanical properties of PBT/ABS blends is investigated and the results discussed in terms of the changes of the fiber wettability and interfacial adhesion strength of the fiber to the resin. The processing conditions used to prepare glass fiber reinforced tough PBT/ABS blends were studied to observe the best conditions to maintain the toughness and stiffness of the blend as high as possible. A twin screw extrusion was used to prepare the reinforced PBT/ABS blends. Tensile, impact and essential work of fracture (EWF) testing was carried out to evaluate the mechanical properties for stiffness and toughness of the reinforced blends, respectively. The results have shown a strong dependence of the mechanical properties on the surface treatment of the fibers and these results are corroborated by electron microscopy micrographs that clearly illustrate the changes in the composite fiber/matrix interface in the presence of differences in surface treatments of the fiber. The development of an optimum stiffness-toughness balance in PBT/ABS blends was achieved and EWF has been successfully applied to evaluate the toughness for PBT/ABS blends. / O terpolímero acrilonitrila-butadieno-estireno (ABS) com alto teor de borracha tem sido utilizado para tenacificar PBT. Como resultados, são obtidas blendas de PBT/ABS super tenazes sob impacto Izod entalhado. No entanto, ocorre uma redução significativa no módulo elástico. O desenvolvimento de um balanço de rigidez-tenacidade em blendas de PBT/ABS pode ser alcançado pela adição de fibras curtas de vidro. O desempenho dos compósitos é fortemente dependente da interface matriz-fibra e consequentemente o tratamento da superfície da fibra é um fator chave a ser considerado. No presente trabalho, foi investigado o efeito de dois tipos de tratamento de fibras de vidro nas propriedades mecânicas de blendas PBT/ABS e os resultados discutidos em termos das mudanças da molhabilidade da fibra e da adesão interfacial da fibra à resina. As condições de processo usadas para preparar as blendas de PBT/ABS reforçadas com fibra de vidro foram estudadas para observar as melhores condições para manter os valores de tenacidade e rigidez tão altos quanto possível. Uma extrusora dupla rosca foi usada para preparar as blendas de PBT/ABS reforçadas. Ensaios de tração, impacto e de tenacidade à fratura por meio do método do trabalho essencial de fratura (EWF) foram executados para avaliar as propriedades mecânicas de rigidez e tenacidade das blendas reforçadas. Os resultados mostraram uma forte dependência das propriedades mecânicas como o tratamento superficial das fibras e estes resultados são corroborados por micrografias de MEV, que claramente ilustram as mudanças na interface fibra/matriz em função das diferenças nos tratamentos superficiais das fibras. O desenvolvimento de um balanço de rigidez-tenacidade ótimo em blendas de PBT/ABS foi alcançado e o método EWF foi aplicado com sucesso para avaliar a tenacidade à fratura das blendas.
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