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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Caracterização da sílica amorfa extraída da casca de arroz obtida por pré-hidrólise ácida e calcinação, e sua aplicação em borracha de estireno-butadieno (SBR) / Characterization of amorphous rice husk silica obtained by acidic prehydrolysis and calcination, and its application in styrene-butadiene rubber (SBR)

Eduardo Roque Budemberg 14 June 2013 (has links)
O crescimento dos países em desenvolvimento aumentará em várias vezes o consumo de energia, materiais e alimentos. Para suprir essa demanda é necessário o aproveitamento racional dos resíduos gerados por processos industriais, agrícolas e lixo urbano, transformando-os em energia economicamente competitiva com as outras formas de energia, e em materiais com propriedades otimizadas. O objetivo do presente trabalho foi comparar o comportamento da sílica da casca de arroz obtida por pré-hidrólise ácida seguida de calcinação controlada (Sil-PH) com sílicas de casca de arroz comerciais obtidas simplesmente pela queima da casca (Sil-B e Sil-C) e com a sílica comercial obtida da areia quartzítica (Sil-Z), como carga de reforço em borracha de estireno-butadieno (SBR), que é a mais usada na indústria de fabricação de pneus. Estudos foram conduzidos em SBR 1502, preparados conforme norma ASTM 3191-2010. Foram adicionadas à borracha as sílicas em concentrações de 0, 10, 20 e 40 ppcb. Foram conduzidos testes físicos, químicos, mecânicos, reométricos, dinâmico-mecânicos e análise térmica, bem como ensaios de inchamento dos corpos de prova em toluol e análise microestrutural das sílicas e dos compostos por microscopia eletrônica de varredura, com o objetivo de determinar a natureza do reforço. O número de ligações cruzadas foi avaliado e a energia de formação dessas ligações foi calculada. A relação entre as metodologias de cálculo da densidade de ligações cruzadas foi também avaliada, obtendo a caracterização desse tipo de carga de reforço não somente por correlações mecânicas mas também pela energia de formação das ligações. Os resultados mostraram que quanto maior a adição de sílica, maior é sua interação com a borracha. Dentre as sílicas adicionadas, Sil-Z alcançou os maiores valores de propriedades mecânicas dos compostos, e Sil-PH mostrou os melhores resultados dentre as sílicas de casca de arroz. Por avaliação por inchamento em toluol (teste estático) e por testes de tração e testes dinâmicos foi possível afirmar que as densidades de ligações cruzadas estão correlacionadas, Usando os resultados de reometria e as equações de Arrhenius estimou-se uma energia média de ligação, concluindo que esta corresponde a uma ligação do tipo covalente. Pelos valores de tan ? confirmou-se que os compostos com Sil-PH têm maior aderência no chão molhado do que aqueles com Sil-Z. A sílica nos compostos tende a diminuir a temperatura de transição vítrea. Os resultados da análise térmica mostraram elevada estabilidade térmica dos compostos com Sil-PH e Sil-Z. A falta de cominuição adequada da Sil-PH ocasionou uma dispersão irregular da sílica na SBR, uma molhabilidade parcial da sílica pela borracha e pelo agente de acoplamento, com consequente aparecimento de falhas na estrutura do composto. Por esse motivo as propriedades mecânicas dos compostos com Sil-PH foram inferiores às dos compostos com Sil-Z. / Developing countries are increasing by several times their consumption of energy, materials, and food. To attend their demand it is necessary to rationally reuse industrial, agricultural, and municipal solid waste residues, transforming them into economically competitive energy and materials with optimized properties. The objective of this work was to compare the behavior of a rice husk silica obtained by acidic prehydrolysis and controlled calcination (Sil-PH) with commercial amorphous silicas obtained from quartzite sand (Sil-Z) and from simply burned rice husks (Sil-B and Sil-C), as reinforcing filler in styrene-butadiene rubber (SBR) composites, which is the most used rubber in the tire manufacture industry. Studies were conducted on SBR 1502 rubber according to ASTM 3191-2010 in which amorphous silicas obtained from rice husk and quartzite silica were added at concentrations of 0, 10, 20, and 40 phr. Physical, chemical, mechanical, rheometric, dynamic-mechanical tests, thermal analysis, swelling studies in toluol and scanning electron microscopy of the silicas and composite specimens were made with objective to determine the nature of reinforcement. The number of crosslinks was evaluated and the energy of formation of these bonds calculated. The correlation between the methodologies of calculation of crosslink density was also evaluated, getting the characterization of this type of reinforcing filler not only by mechanical correlations but also by the energy of their formation. The results showed that the higher the content of added silica, the greater the interaction with rubber. According to the mechanical properties values Sil-Z achieved the highest properties values but Sil-PH showed better results compared to the other types of rice husk silicas. By evaluation by swelling in toluene (static), tensile tests and dynamic tests it was possible to affirm that the crosslink densities are correlated. By using the rheometry results and the Arrhenius equations the average bound was estimated to be of a covalent type. The silica in the compounds tends to lower the values of the glass transition temperature. The evaluation of tan ? showed that Sil-PH has more stickiness on the wet floor, which is an important property to tire application. Due to the lack of appropriate grinding of the Sil-PH the dispersion of the silica on SBR was irregular; partial wetting of the silica particles by rubber and silane had also occurred. Those facts had caused failures on the compound structural integrity, with a consequent lowering of the mechanical property values as compared to the compounds with Sil-Z addition.
112

Modelagem matemática e estudo experimental da copolimerização de estireno e butadieno em emulsão. / Mathematical modeling and experimental study of styrene - butadiene emulsion copolymerization.

Aluisio Pinelli Filho 08 May 2006 (has links)
Neste trabalho, estudos da copolimerização em emulsão de estireno e butadieno foram realizados em duas etapas. A primeira etapa consistiu na obtenção de um modelo matemático que representasse os processos em batelada e em semicontínuo através das principais variáveis do processo. Na segunda etapa, o efeito de diversas variáveis importantes ao processo foi avaliado, dentre elas: o tempo de adição dos reagentes, o tipo de alimentação empregado e a temperatura da reação. O modelo matemático se baseia em um trabalho previamente publicado que foi adaptado para simular o processo de copolimerização de estireno e butadieno em emulsão. Foram simulados processos em batelada e em semicontínuo. Em conjunto com os resultados experimentais, foi realizada a estimação de parâmetros não obtidos na literatura utilizando o método de Marquardt. As características do processo e as propriedades do polímero, tais como, conversão, diâmetro de partícula, taxa de polimerização e pressão interna do reator também foram obtidas, fornecendo condições para otimização e avaliação do processo de polimerização em batelada e em semicontínuo. Adicionalmente, também foi proposto um modelo de equilíbrio líquido-vapor dos monômeros. Os ensaios experimentais foram realizados em reator encamisado semicontínuo de mistura com 3 litros, nos quais foram utilizados persulfato de sódio como iniciador, lauril sulfato de sódio como emulsificante e tercdodecil mercaptana como agente de transferência de cadeia. Foram estudados os efeitos da temperatura, do tipo e do tempo de alimentação utilizada. A velocidade de polimerização, os diâmetros médios de partículas, o teor de monômero residual, o teor de insolúveis e o teor de resíduos foram avaliados. A cromatografia gasosa foi aplicada com sucesso em análises de látex e monômeros com finalidades diversas, destacando-se a obtenção de coeficientes de atividade necessários ao modelo de equilíbrio líquido-vapor, análise da concentração de monômeros ao longo da reação e análise da concentração de monômero residual. / In this work, studies of the styrene butadiene emulsion copolymerization had been performed in two stages. The first stage composed of a mathematical model that represented the batch and semi continuous process. In the second stage, the effects of diverse process variables were evaluated, among them: the time of addition of the reagents, feeding type and temperature reaction. The mathematical model was based on previously published work that it was adapted to simulate the styrene butadiene emulsion copolymerization process. Batch and semi continuous processes were simulated. In assembly with the experimental results, Marquardt method was applied to estimate some parameters that wasn’t found in literature. The variable process and the properties of polymer, such as, conversion, particle diameter, rate of polymerization and pressure of the reactor had been also simulated to batch and semicontinous process. A liquid-vapor balance of monomers model was proposed. The experimental stage had been carried through in a semi continuous stirring jacket tank reactor with 3 liters. Sodium persulfate as initiating, sodium lauryl sulfate as surfactant and Tert dodecyl mercaptan as chain transference agent had been used. The effect of temperature, type and time feeding had been studied. Polymerization rate, particles diameter, residual monomer had been evaluated. The gaseous chromatography was successfully applied in analyses of latex with diverse purposes: activity coefficient estimation, adjustment of liquid-vapor model, analysis of residual monomer of the reaction and volatiles organic components concentration in final latex.
113

Réactivité catalytique à haut recouvrement : une approche théorique / Catalytic reactivity at high coverage : a theoretical approach

Gautier, Sarah 28 September 2015 (has links)
L’hydrogénation sélective d’hydrocarbures polyinsaturés présente un fort intérêt pour l’industrie pétrolière. Cette réaction est catalysée par des particules métalliques ou des alliages et a lieu sous pression d’hydrogène. Dans ce travail nous étudions la réaction d’hydrogénation sélective du butadiène en 1-butene en présence des catalyseurs Pt(111) et Sn/Pt-Pt(111). Cette étude a été menée à l’aide du programme VASP (Vienna Abinitio Simulation Package) qui permet de simuler des systèmes solides et surfaciques dans le cadre de la théorie de la fonctionnelle de la densité (DFT). Le choix des catalyseurs a été dicté par les communautés expérimentale et industrielle qui utilisent le plus souvent le platine car très actif, ou des alliages de platine-étain, moins actifs mais beaucoup plus sélectifs. L’hydrogénation du butadiène a déjà été étudiée par le passé mais uniquement à T=0 K et sans prendre en compte les conditions réelles de pression des réactifs. Notre but étant de comprendre les pas élémentaires de cette réaction, nous avons choisi de l’étudier à des conditions de T et de P proches de celles utilisées expérimentalement, c’est-à-dire 300-400 K et 1-10 bar. A cette fin, nous avons mis en place un modèle thermodynamique pour évaluer, dans un premier temps, la composition de la surface lors de la réaction. Il est alors apparu que la configuration de surface la plus stable correspond à une couverture de une monocouche d’hydrogène ce qui suggère un mécanisme de type Eley-Rideal. Puis nous avons étudié l’aspect cinétique ce cette réaction et calculé les chemins réactionnels pour différents recouvrements en hydrogène. Nous avons conclu qu’il existe une forte compétitivité entre le mécanisme pressenti, appelé Langmuir-Hinshelwood et impliquant des espèces fortement adsorbées, et le mécanisme Eley-Rideal proposant une adsorption faible de l’un des réactifs. Les calculs ont été effectués avec les fonctionnelles PBE et optPBE pour apporter un point de comparaison des méthodes. / Petroleum industry has a strong interest in the selective hydrogenation of polyunsaturated hydrocarbons. This reaction is catalyzed by metallic particles or alloys and happens under pressure of hydrogen. In this work, we study the selective hydrogenation of butadiene into 1-butene, on two model catalysts which are Pt(111) and Sn/Pt-Pt(111). For this, we used the VASP code (Vienna Abinitio Simulation Package) that allows to perform periodic calculations in the framework of the Density Functional Theory (DFT). The choice of the catalysts was driven by the experimental and industrial communities who mostly use platinum because of its high activity, or alloys such as tin-platinum alloy, less active but more selective. Butadiene hydrogenation was already modeled in the past but only at T=0 K and without taking into account the real pressure conditions of the reactants. Our aim is to understand the impact of the reaction conditions which is why we ran this study at T and P conditions close to the one used experimentally, e.g. 300-400 K et 1-10 bar. For this, we setup a thermodynamic model to evaluate in a first step the surface composition when the reaction occurs. It came out that the most stable surface configuration corresponds to a coverage of 1 ML of hydrogen which suggests an Eley-Rideal type mechanism. Then we studied the kinetic aspect of this reaction and we calculated the hydrogenation pathways for different coverages of hydrogen. We concluded that there is a strong competition between the sensed mechanism, called Langmuir-Hinshelwood mechanism and implying strongly adsorbed species, and the Eley-Rideal mechanism, proposing a weak adsorption of one of the two reactants.
114

Développement d'une nouvelle voie de synthèse de catalyseurs métalliques autosupportés (nanomousses) : étude des propriétés structurales et catalytiques / New synthesis way for self-supported metal catalysts (nanofoams) : study of strutural and catalytic properties

Deronzier, Thierry 16 October 2012 (has links)
L’or, habituellement considéré comme catalytiquement inactif, fait preuve d’une activité étonnante pour diverses réactions d’oxydation pourvu qu’il soit supporté sur un oxyde approprié. Ces dix dernières années, des méthodes de synthèse par dissolution sélective du composé le moins noble d’un alliage métallique (dealloying) ont permis l’obtention de catalyseurs d’or nanoporeux. Ces catalyseurs font preuve d’une très forte activité catalytique vis-à-vis de la réaction d’oxydation du monoxyde de carbone. Cependant, des études plus récentes semblent montrer que cette activité est due aux impuretés présentes dans les catalyseurs, qui sont imputables aux limitations de la méthode de synthèse utilisée. Dans cette étude, un catalyseur nanoporeux d’or pur a été obtenu par oxydation spontanée d’un alliage AuZr à température ambiante puis dissolution sélective totale de ZrO2 dans HF. Ce catalyseur démontre des caractéristiques structurales et morphologiques similaires à celles des échantillons obtenus par dealloying. Leur évaluation catalytique a été réalisée par réaction d’oxydation du CO et en PrOx : les résultats montrent que l’or pur nanoporeux n’est pas catalytiquement actif. La préparation de catalyseurs AgAu selon la même méthode a permis l’obtention de catalyseurs de différentes teneurs en argent, proches des résidus obtenus par dealloying. L’impact de la présence de l’impureté d’argent sur la catalyse est avéré : elle permet d’exacerber l’activité de l’or à température ambiante par synergie des deux éléments. Cependant, l’effet promoteur de l’hydrogène disparaît en PrOx et l’impact de la concentration d’argent est faible lors de l’oxydation du CO. Une étude exploratoire sur les nanomousses NiPd a été menée en parallèle. Le palladium, qui présente le meilleur compromis activité/sélectivité pour les hydrogénations sélectives, voit son activité exacerbée lorsqu’il est déposé à la surface d’un monocristal de Nickel. Cet effet n’existe pas pour des nanoparticules Pd/Ni supportées. Un catalyseur NiPd a donc été préparé dans cette étude selon la méthode des nickels de Raney® afin de combiner les propriétés des monocristaux et des nanoparticules / Gold, generally considered as catalytically inactive, demonstrates a surprising activity toward several oxidation reactions when supported on a proper oxide. New synthesis ways have been developed for ten years to obtain nanoporous gold catalysts based on selective dissolution of the less noble component of a metallic alloy (dealloying). These catalysts exhibit very high activity towards the carbon monoxide oxidation reaction. However recent studies seem to reveal that this activity could be due to impurities inherent to dealloying. In this study a very pure nanoporous catalyst was obtained by spontaneous oxidation of a AuZr alloy at room temperature; a total selective dissolution of ZrO2 was then carried out in HF. Its structural and morphological characteristics proved to be similar to the dealloyed catalysts ones. The evaluation of its catalytic properties by CO oxidation showed that pure nanoporous gold was not catalytically active. Besides bimetallic AgAu catalysts were prepared following the same preparation method with three silver concentrations chosen close to the residual impurities concentrations obtained by dealloying. Their catalytic properties proved to be impacted by silver impurities: gold activity was emphasized at room temperature by synergy between the two elements. However, the promotional effect of hydrogen disappeared in PrOx and the role of silver concentration was low for CO oxidation. In parallel an exploratory study was carried out on NiPd nanofoams. The catalysts were prepared following the Raney® nickel method to improve the palladium activity towards the selective hydrogenation reaction. The results showed a slight increase of the catalytic activity
115

Synthese von 1,2-difunktionalisierten 1,3-Butadienen über eine Sequenz [3,3]-sigmatroper Umlagerungen

Schlott, Jana 29 February 2000 (has links)
Es wird eine neue Sequenz von [3,3]-sigmatropen Umlagerungen vorgestellt, die zu 1,2-difunktionalisierten 1,3-Butadienen führt. Dabei werden ausgehend von 3-Butin-1,2-diyl-Derivaten im ersten Umlagerungsschritt 1,2-Butadien-1,4-diyl-Verbindungen erhalten, die anschließend im zweiten Umlagerungsschritt zu den Zielprodukten isomerisieren. Die Anwendungsbreite dieser Synthesemethode wird anhand verschiedener Verbindungsklassen dokumentiert. So gelingt beispielsweise ausgehend von 3-Butinen mit jeweils zwei Imidat-, Thiokohlensäurearylester-, Xantogenat-, Thiocarbamat- sowie Thiobenzoat-Funktionen in 1- und 2-Position die Darstellung der entsprechend 1,2-disubstituierten 1,3-Butadiene, die zwei identische funktionelle Gruppen in Vinylposition tragen. Die geeignete Substitution des Grundgerüstes der 3-Butin-1,2-diyl-Vorläufer zeigt, daß die [3,3]-sigmatropen Isomerisierungen der diastereomeren Edukte stereospezifisch zu den entsprechenden Butadienen führen, die sich bezüglich der Konfiguration der Doppelbindungen unterscheiden. Zur Erklärung dieses Sachverhaltes werden die sterischen Wechselwirkungen diskutiert, die die Konformationen der durchlaufenen Übergangszustände beeinflussen und damit die bevorzugte Bildung bestimmter Konfigurationen der resultierenden Butadiene bedingen. Die Ermittlung der Konfiguration der synthetisierten Diene erfolgt zum einen durch NMR-Spektroskopie, wobei insbesondere die NOE-Differenzspektroskopie ein wertvolles Mittel zur Konfigurationsbestimmung darstellt. Zum anderen werden die unterschiedlichen Reaktivitäten der konfigurationsisomeren Butadiene bei Cycloadditionsreaktionen, speziell Diels-Alder-Reaktionen, zur Aufklärung der Stereochemie der Doppelbindungen genutzt. Gleichzeitig zeigen diese Folgereaktionen exemplarisch das Synthesepotential der Zielprodukte.
116

Bio-Based Flame Retardation of Acrylonitrile-Butadiene-Styrene

Schinazi, Gustavo 26 January 2021 (has links)
No description available.
117

Investigating the Possibilities of Using a Handheld FTIR-Equipment to Characterize Thermal Aging of Rubbers / Undersöka möjligheterna att använda en handhållen FTIR-utrustning för att karakterisera termisk åldring av gummi

Tengbom, Antonia January 2020 (has links)
Element Materials Technology in Linköping is an independent material testing company that performs testing of materials to several big sectors, such as the Swedish Armed Forces and the aerospace industry. There is of great importance to characterize aging of materials to ensure material performance. Element Materials Technology recently invested in a handheld FTIR equipment and it was of interest to see if this equipment might be an additional analysis technique to characterize aging of rubber materials. A nitrile butadiene rubber and two natural rubbers were thermally aged in 50°C and 70°C for six weeks. The hardness of the rubbers increased when the rubbers were thermally aged. The compression set decreased for the aged samples as well as the tensile strength and the elongation at break. An investigation of possible methods for collecting migrated additives on the rubber surface was performed, using two different solvents and a stationary FTIR equipment. More research needs to be performed to exclude the possibility that the solvents affect the material. Universal Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy, UATR-FTIR onto the rubber surface showed in some cases changes in the spectrums between unaged and aged samples. However, it could not be concluded weather the changes occurred due to migrating additives or due to changes in the backbone polymer. Four interfaces to the handheld FTIR equipment were investigated and an ATR interface gave best results. An analysis method was developed for the handheld FTIR equipment and the spectrums from the handheld FTIR were similar to spectrums from UATR-FTIR (stationary). It could be concluded from Micro Chamber analysis that volatile organic matters were emitted at elevated temperature. Thermogravimetric analysis could detect the relative composition of the rubbers. Further it could be concluded that the mechanical properties were affected by the thermal treatment. This study could however not establish a correlation between FTIR signals and the results seen from the other analysis. The fact that differences could be detected in the FTIR spectrums before and after aging could indicate that the FTIR analysis technique can possibly be used as an analysis method. However, a more thoroughly investigation needs to be performed before using this technique. / Element Materials Technology i Linköping utför materialutredningar åt en mängd olika typer av företag, där en stor sektor är den svenska Försvarsmakten och flygindustrin. Materialutredningar är essentiella för att säkerställa att rätt material används för rätt applikation. Element Materials Technology investerade nyligen i en handhållen FTIR utrustning. Det finns förhoppningar om att den nya utrustningen kan användas som ett komplement för att ålderskarakterisera gummimaterial. Ett nitril-butadien-gummi och två stycken naturgummin var termiskt åldrade i 50°C och 70°C i sex veckor. Hårdheten på provkroppar ökade efter den termiska åldringen. Sättningen, draghållfastheten och töjningen minskade för proverna åldrade i värme. En metod för att samla upp migrerade additiv från gummiytan utvecklades och undersöktes, genom att använda två olika lösningsmedel och en stationär FTIR utrustning. Ytterligare utredningar behöver däremot genomföras för att utesluta ifall de två lösningsmedel påverkar gummimaterialet och inte bara samlar upp additiv från gummiytan. UATR-FTIR visade på skillnader i spektrum mellan icke-åldrade och åldrade gummimaterial. Däremot kunde det inte avgöras om skillnaderna i spektrumen berodde på migration av additiv till gummiytan eller på förändring i huvudpolymeren. Fyra stycken olika tillbehör till den handhållna FTIR utrustningen prövades, där ATR-tillbehöret gav bra spektrum. En analyseringsmetod utvecklades för den handhållna FTIR-utrustningen och spektrum från dessa analyser gav liknande spektrum som spektrum från UATR-FTIR (stationär). Analys med Micro Chamber visade att flyktiga organiska ämnen lämnade gummimaterialet vid förhöjd temperatur. Termogravimetrisk analys, TGA visade förhållandet mellan gummimaterialets komponenter både före och efter åldring. Studien visade också att de mekaniska egenskaperna påverkades av den termiska åldringen. Analysmetoden FTIR kunde detekterad skillnad i spektrum före och efter åldring av gummimaterialen. Studien kunde däremot inte etablera ett samband mellan dessa FTIR-signaler och de övriga analysresultaten. Det kan däremot inte uteslutas att ett sådant samband finns. Ytterligare studier behöver utföras för att undersöka detta.
118

Thermal-Stress Characteristics of Large Area Additive Manufacturing

Friedrich, Brian K., II 09 May 2022 (has links)
No description available.
119

[en] INFLUENCE OF ADDITION OF BUTADIENE COPOLYMER AND MODIFIED STYRENE ON THE MECHANICAL BEHAVIOR OF A SAND / [pt] INFLUÊNCIA DA ADIÇÃO DE COPOLÍMERO DE BUTADIENO E ESTIRENO MODIFICADO NO COMPORTAMENTO MECÂNICO DE UMA AREIA

THIAGO MANES BARRETO 19 May 2021 (has links)
[pt] O estudo avalia o comportamento mecânico de uma areia reforçada com polímero, em comparação à areia pura. Foram realizados ensaios cisalhamento direto em amostras de areia pura e desta com a adição do copolímero de butadieno e estireno modificado (XSBR). O copolímero de butadieno e estireno é um elastômero composto de aproximadamente 75 porcento de butadieno e 25 porcento de estireno, presente em solução aquosa, sendo muito utilizada na indústria automobilística, para a produção de pneus. Pode ser produzido a partir dos processos de polimerização em emulsão ou polimerização em solução. A escolha destes materiais está relacionada às suas propriedades serem compatíveis as exigências para melhoramento de solos em obras geotécnicas. As amostras de areia com polímero apresentavam 50 porcento de densidade relativa, 10 porcento de umidade, nas proporções em volume água-polímero de 1:1, 1:2 e 1:4, sem tempo de cura, ou com tempos de cura de 24, 48, 72, 96, 576, 720 e 1080 horas. Foram constatadas melhorias nos parâmetros de resistência das amostras de areia com adição de polímero, em comparação aos parâmetros da areia pura, mostrando que a melhoria de solos com polímero é satisfatória para a aplicação em obras geotécnicas, como por exemplo: aterros sobre solos moles, solos de fundações superficiais e para a estabilidade de taludes. / [en] The study evaluates the mechanical behavior of a sand reinforced with polymer compared to pure sand. Direct-cut tests were carried out on pure sand samples and with the addition of modified styrene butadiene-styrene (XSBR) copolymer. The copolymer of butadiene and styrene is an elastomer composed of approximately 75 percent butadiene and 25 percent styrene, purchased in aqueous solution, being widely used in the automotive industry for the production of tires. It may be produced from the emulsion polymerization or solution polymerization processes. The choice of these materials is related to their properties being compatible the requirements for soil improvement in geotechnical works. Polymer sand samples had 50 percent relative density, 10% moisture, in water-polymer volume ratios of 1:1, 1:2 and 1:4, without curing time, or with times of cure 24, 48, 72, 96, 576, 720 and 1080 hours. Improvements in the resistance parameters of the sand samples with polymer addition were verified in comparison to the pure sand parameters, showing that the improvement of soils with polymers is satisfactory for the application in geotechnical works, such as: landfills on soft soils, soils of shallow foundations and for slope stability.
120

Reciclagem do copolímero acrilonitrila-butadieno-estireno e do poliestireno de alto impacto oriundos de rejeitos de equipamentos elétricos e eletrônicos na forma de blendas poliméricas / Recycling of copolymer acrylonitrile-butadiene-styrene and high impact polystyrene from waste electrical and electronic equipment in the form of polymer blends

Hirayama, Denise 14 August 2015 (has links)
O crescimento na geração de rejeitos de equipamentos elétricos e eletrônicos (REEE), legislações mais rigorosas e o valor agregado destes materiais incentivam o desenvolvimento de tecnologias de reciclagem. Contudo, a reciclagem dos componentes poliméricos dos REEE (CP-REEE) precisa superar desafios como a degradação durante o uso e reprocessamento, a presença de diferentes aditivos nos rejeitos e a depreciação de propriedades causada pela mistura não controlada de polímeros. Assim, o objetivo deste trabalho foi desenvolver um estudo sobre a reciclagem mecânica na forma de blendas poliméricas de rejeitos do copolímero acrilonitrila-butadieno-estireno (ABS) e do poliestireno de alto impacto (HIPS), empregando agentes compatibilizantes. No desenvolvimento do trabalho foram realizadas a caracterização dos CP-REEE, análise das propriedades mecânicas, químicas, térmicas e morfológicas dos polímeros e das blendas de ABS/HIPS nas proporções de 1:3, 1:1 e 3:1 com variações na composição dos polímeros reciclados e virgens e por fim, realizado um estudo do envelhecimento foto-oxidativo acelerado de uma blenda ABS/HIPS. Os resultados mostraram que os polímeros ABS e HIPS reciclados ainda apresentam boas propriedades mecânicas e que a presença de agentes compatibilizantes provoca o aumento da tenacidade nas blendas ABS/HIPS. A incorporação de polímeros virgens nos materiais reciclados não promove ganho significativo nas propriedades mecânicas das blendas. Blendas com até 50% de ABS demonstraram ter propriedades próximas às do HIPS, enquanto as blendas com altos teores de ABS não alcançaram valores de propriedades mecânicas similares aos do ABS virgem. O comportamento das propriedades das blendas virgens e recicladas frente ao envelhecimento fotoquímico foi similar, indicando que o material reciclado apresenta grande potencial para aplicações. O estudo de blendas ABS/HIPS de CP-REEE demonstra que o controle da composição das blendas definem a sua aplicação. / The growth in waste electrical and electronic equipment (WEEE) generation, directives more stringent and the aggregate value presents in these waste are encouraging the development of recycling technologies. However, recycling of polymeric components from WEEE (PC-WEEE) must overcome challenges such as degradation during use and reprocessing, the presence of various additives in the waste and the depreciation of properties caused by uncontrolled polymers mixture. The aim of this work was to develop a study of the mechanical recycling in the form blends with of polymeric waste of acrylonitrile-butadiene-styrene copolymer blends (ABS) and high impact polystyrene (HIPS) using compatibilizers. During the study was carried out the characterization of the PCWEEE and mechanical, chemical, thermal and morphological analysis of the polymers and the ABS / HIPS blends in proportions of 1:3, 1:1 and 3:1 with recycled and virgin polymers, as well as a study of the accelerated photo-oxidative aging of the ABS/HIPS blends. The results showed that ABS and HIPS recycled polymers still have good mechanical properties and the presence of compatibilization agents leads to increased toughness in ABS/HIPS blends. The incorporation of virgin polymers in recycled materials does not promote significant gain in the mechanical properties of the blends. Blends with up to 50% ABS have demonstrated to be closer to the HIPS, while blends with high content of ABS did not reach values of mechanical properties similar to the virgin ABS. The mechanical properties of virgin and recycled blends during the photochemical aging were similar, indicating that the recycled material has great potential for applications. The study of ABS/HIPS blends from PC-WEEE demonstrated that control of the blend composition establish their applications.

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