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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.
391

[en] ANALYSIS OF THE BEHAVIOR OF REINFORCED SOIL WITH EXPANDED POLYSTYRENE / [pt] ANÁLISE DO COMPORTAMENTO DE SOLOS REFORÇADOS COM POLIESTIRENO EXPANDIDO

ALENA VITKOVA CALHEIROS 22 November 2018 (has links)
[pt] Este estudo apresenta o comportamento de solos reforçados com adição de pérolas de EPS (Poliestireno Expandido) através de estudo experimental. Os solos utilizados foram: um solo argiloso de origem coluvionar, uma areia limpa, mal graduada e bentonita. Foram realizados ensaios de caracterização física e de caracterização mecânica, como ensaios de compactação Proctor Normal, ensaios triaxiais consolidados isotropicamente drenados (CID) e ensaios de cisalhamento direto para buscar estabelecer padrões de comportamento que possam explicar a influência da adição de pérolas de EPS, relacionando-a com os parâmetros de resistência ao cisalhamento. Os ensaios triaxiais CID foram realizados em amostras de solo argiloso compactadas na densidade máxima seca e umidade ótima, com teores de pérolas de EPS de 0 por cento, 0,25 por cento, 0,50 por cento, 0,75 por cento e 1 por cento, em relação ao peso seco do solo e os ensaios triaxiais CID em amostras de areia foram realizados para uma densidade relativa de 50 por cento e umidade de 10 por cento, com teores de pérolas de EPS de 0 por cento, 0,50 por cento e 0,75 por cento, em relação ao peso seco do solo. Os ensaios de cisalhamento direto com bentonita foram realizados com teores de pérolas de EPS de 0 por cento, 0,50 por cento e 0,75 por cento, em relação ao peso seco do solo. Os resultados mostraram que o tipo de solo, o teor de pérolas de EPS e o nível de tensão confinante influenciam positivamente o comportamento mecânico final dos compósitos com relação aos parâmetros de resistência, porém não há uma tendência de comportamento bem definida ao analisar cada fator independentemente. Portanto, o uso de pérolas de EPS em obras geotécnicas de carregamento estático contribuiria com o menor consumo de material natural e a consequente redução dos custos de transporte e volume de material mobilizado. / [en] This study presents the behavior of soils reinforced with EPS (Expanded Polystyrene) beads through experimental study. The soils used were a coluvionar soil, a clean and barely graduated sand and bentonite. Physical characterization, Standard Proctor, consolidated drained triaxial and direct shear tests were performed to establish patterns of behavior that may explain the influence of the addition of expanded polystyrene beads, linking it with shear strength parameters. The CID triaxial was performed on samples of clayey soil compacted within the maximum dry density and optimum moisture content with expanded polystyrene beads ratios of 0 percent, 0.25 percent, 0.50 percent, 0.75 percent and 1 percent by dry weight of soil. CID triaxial tests on sand samples were made to a relative density of 50 per cent and 10 per cent of moisture content, with EPS beads ratios of 0 percent, 0.50 percent and 0.75 percent by dry weight of soil. The direct shear tests with bentonite were made with EPS beads ratios of 0 percent, 0.50 percent and 0.75 percent by dry weight of soil. The results showed that the kind of soil, the EPS content and level of confining stress level influence positively on the final mechanical behavior of the composites with respect to strength parameters, but there is no well-defined pattern of behavior to examine each factor independently. Therefore, the use of EPS beads in geotechnical works, contribute to lower consumption of natural material and the consequent reduction in transport costs and volume of mobilized material.
392

Structure and Dynamics of Binary Mixtures of Soft Nanocolloids and Polymers

Chandran, Sivasurender January 2013 (has links) (PDF)
Binary mixtures of polymers and soft nanocolloids, also called as polymer nanocomposites are well known and studied for their enormous potentials on various technological fronts. In this thesis blends of polystyrene grafted gold nanoparticles (PGNPs) and polystyrene (PS) are studied experimentally, both in bulk and in thin films. This thesis comprises three parts; 1) evolution of microscopic dynamics in the bulk(chapter-3),2) dispersion behavior of PGNPs in thin and ultra thin polymer matrices (chapter-4) 3) effect of dispersion on the glass transition behavior (chapter-5). In first part, the state of art technique, x-ray photon correlation spectroscopy is used to study the temperature and wave vector dependent microscopic dy¬namics of PGNPs and PGNP-PS mixtures. Structural similarities between PGNPs and star polymers (SPs) are shown using small angle x-ray scatter¬ing and scaling relations. We find unexpected (when compared with SPs) non-monotonic dependence of the structural relaxation time of the nanoparticles with functionality (number of arms attached to the surface). Role of core-core attractions in PGNPs is shown and discussed to be the cause of anomalous behavior in dynamics. In PGNP-PS mixtures, we find evidence of melting of the dynamically arrested state of the PGNPs with addition of PS followed by a reentrant slowing down of the dynamics with further increase in polymer frac¬tion, depending on the size ratio(δ)of PS and PGNPs. For higher δ the reen¬trant behavior is not observed with polymer densities explored here. Possible explanation of the observed dynamics in terms of the presence of double-glass phase is provided. The correlation between structure and reentrant vitrifica¬tion in both pristine PGNPs and blends are derived rather qualitatively. In the second part, the focus is shifted to miscibility between PGNPs and polymers under confinement i.e., in thin films. This chapter provide a compre¬hensive study on the different parameters affecting dispersion viz., annealing conditions, fraction of the added particles, polymer-particle interface and more importantly the thickness of the films. Changes in the dispersion behavior with annealing is shown and the need for annealing the films at temperatures higher than the glass transition temperature of the matrix polymers is clearly elucidated. Irrespective of the thickness of the films( 20 and 65 nm) studied, immiscible particle-polymer blends unequivocally prove the presence of gradi¬ent in dynamics along the depth of the films. To our knowledge for the first time, we report results on confinement induced enhancement in the dispersion of the nanoparticles in thin polymer films. The enhanced dispersion is argued to be facilitated by the increased free volume in the polymer due to confinement as shown by others. Based on these results we have proposed a phase diagram for dispersibility of the nanoparticles in polymer films. The phase diagram for ultra thin films highlights an important point: In ultra thin films the particles are dispersed even with grafting molecular weight less than matrix molecular weight. In the third part, we have studied the glass transition of the thin films whose structure has been studied earlier in the earlier part. Non-monotonic variation in glass transition with the fraction of particles in thin films has increased our belief on the gradient in the dynamics of thin polymer films. En¬hanced dispersion with confinement is captured with the enhanced deviation in glass transition temperature of ultra thin films. Effect of miscibility param¬eter on Tgis studied and the results are explained with the subtle interplay of polymer-particle interface and confinement.
393

Électrofilage de fibres à partir de mélanges polystyrène/poly(vinyl méthyl éther)

Valiquette, Dominic 08 1900 (has links)
L’électrofilage est un procédé permettant de préparer des fibres possédant un diamètre de l’ordre du micromètre ou de quelques centaines de nanomètres. Son utilisation est toutefois limitée par le manque de contrôle sur la structure et les propriétés des fibres ainsi produites. Dans ce travail, des fibres électrofilées à partir de mélanges de polystyrène (PS) et de poly(vinyl méthyl éther) (PVME) ont été caractérisées. La calorimétrie différentielle à balayage (DSC) a montré que les fibres du mélange PS/PVME sont miscibles (une seule transition vitreuse) lorsque préparées dans le benzène, alors qu'une séparation de phases a lieu lorsque le chloroforme est utilisé. Les fibres immiscibles sont néanmoins malléables, contrairement à un film préparé par évaporation du chloroforme qui a des propriétés mécaniques médiocres. Des clichés en microscopies optique et électronique à balayage (MEB) ont permis d’étudier l'effet de la composition et du solvant sur le diamètre et la morphologie des fibres. Des mesures d’angles de contact ont permis d’évaluer l’hydrophobicité des fibres, qui diminue avec l’ajout de PVME (hydrophile); les valeurs sont de 60° supérieures à celles des films de composition équivalente. Un retrait sélectif du PVME a été réalisé par l’immersion des fibres dans l’eau. La spectroscopie infrarouge a montré que la composition passe de 70 à 95% de PS pour une fibre immiscible mais seulement à 75% pour une fibre miscible. Ces résultats indiquent que la phase riche en PVME se situe presque uniquement à la surface des fibres immiscibles, ce qui a été confirmé par microscopie à force atomique (AFM) et MEB. Finalement, l’effet du mélange des deux solvants, lors de l’électrofilage du mélange PS/PVME, a été étudié. La présence du chloroforme, même en quantité réduite, provoque une séparation de phases similaire à celle observée avec ce solvant pur. / Electrospinning is a simple method for the preparation of polymer fibers with diameters of hundreds of nanometers to a few micrometers. Although it is a versatile method, some issues remain in the control of the structure and properties of electrospun fibers. In this study, fibers electrospun from polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends were characterized. Differential scanning calorimetry (DSC) revealed that fibers electrospun from benzene are miscible while a phase separation occurs when the fibers are electrospun from chloroform. While films cast from chloroform show poor mechanical properties, immiscible fibers are ductile. The effects of the blend composition and the solvent on the fiber diameter and morphology were observed by scanning electron microscopy (SEM) and optical microscopy. Afterwards, contact angle measurements were made to evaluate the hydrophobicity of the fibers which decreases as hydrophilic PVME is added to the blend; the values for the fibers were found to be 60° higher than their equivalent in films. PVME was selectively removed from the immiscible fibers by complete immersion into water. Infrared spectroscopy revealed that this process increases the PS content from 70 to 95% for immiscible fibers but only to 75% for miscible fibers. These results show that the PVME-rich phase is almost completely distributed on the fiber surface, which was confirmed by atomic force microscopy (AFM) and SEM. Finally, the electrospinning of PS/PVME blends from chloroform/benzene solutions was studied. The presence of chloroform, even as a residual amount, causes a phase separation just as it does in fibers electrospun from pure chloroform.
394

Structure des solutions aqueuses de polyélectrolytes fortement chargés / Structure of aqueous solutions of strongly charged polyelectrolytes

Lorchat, Philippe 06 September 2012 (has links)
Nous étudions la structure des solutions concentrées de polyélectrolytes (PE). Celle-ci n’a fait l’objet que de rares études expérimentales et aucun ordre d'orientation n'a jamais pu être observé dans les solutions de PE flexibles et semi-flexibles, bien que des travaux théoriques, basés sur l’approche d’Onsager, prévoient l'apparition d'une phase nématique aux fortes concentrations. Nous avons mesuré la position q* dans l'espace réciproque du pic présent dans la fonction de corrélation des solutions de PE fortement chargés obtenue par diffusion de rayonnement (DXPA et DNPA), et avons confronté sa variation avec la concentration c aux lois d'échelles théoriques q*~ca. Nous avons combiné des très fortes concentrations avec une haute résolution spatiale. La rigidité intrinsèque du PE est le paramètre clef de l’étude. En effet, le PSS, PE flexible, présente 3 régimes déjà connus : a=1/2 -régime semi-dilué- a=1/4 -régime concentré- un régime « ionomère » aux plus fortes concentrations pour lequel a=0. Le PDADMAC, PE semi-flexible, présente un comportement plus original puisque 4 régimes se succèdent : régimes semi-dilué et concentré avec a=1/2 et 1/4, puis deux régimes pour lesquels a=1 puis 1/2 qui sont totalement inédits. Le PaMSS, de rigidité intrinsèque intermédiaire, présente un comportement ambivalent, puisque les régimes semi-dilué et concentré précèdent un régime où a=1, puis un comportement « ionomère ». Nous introduisons un modèle simple permettant d'interpréter la succession des régimes a=1 puis 1/2 par l'apparition d'un ordre d'orientation. Nous discutons aussi les différences observées par DXPA et DNPA, et le rôle de la force ionique, variée par ajout de sel. / The structure of concentrated polyelectrolyte (PE) solutions is studied. There is a lack of experimental data on these systems. Specifically, no orientational order has ever been observed in solutions of flexible or semi-flexible PE, even though the existence of a nematic phase has been theoretically predicted at high concentration. We have measured the position q* in the reciprocal space of the peak that is present in the correlation function of aqueous solutions of highly charged PE, obtained by scattering measurements (SAXS and SANS). We combined high spatial resolution and a very wide concentration range to compare the variation of q* versus the concentration c, with the predicted scaling laws q*~ca. The intrinsic stiffness of PE is the key parameter of our study. Indeed, PSS, a flexible PE, exhibits 3 regimes already described: a=1/2 -semi-dilute regime- a=1/4 -concentrated regime- an “ionomeric” regime at extreme concentrations, for which a=0. PDADMAC is semi-flexible and exhibits a unique series of exponents involving 4 regimes: semi-dilute and concentrated regimes with a=1/2 and 1/4, followed by 2 regimes associated with a=1 and 1/2 respectively, which are new and unpredicted for PE solutions. PaMSS has an intermediate intrinsic stiffness, and exhibits hybrid behaviour. The semi-dilute and concentrated regimes are followed by an a=1 regime, and then an “ionomeric” regime for extreme concentrations. We introduce a simple model which explains the succession of the a=1 and 1/2 regimes as the appearance of an orientational order. We also discuss the differences between SAXS and SANS measurements, and the role played by the ionic strength, when salt is added.
395

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.
396

Interações entre bicamadas lipídicas e interfaces hidrofóbicas / Interactions between lipid bilayers and hydrophobic interfaces

Pereira, Edla Moraes de Abreu 28 November 2003 (has links)
Determinações de tensão superficial (γ) na interface ar-água e espessuras médias elipsométricas in situ (d), foram usadas para estudar as interações entre dispersões de lípides (em forma de bicamadas) e filmes de poliestireno sulfato produzidos por revestimento rotacional sobre placas de óxido de silício. A adição de NaCl para uma concentração final de 50 mM em uma dispersão de 0.2 mM de lípide catiônico sintético produziu instantaneamente uma camada de 6 nm de espessura que permaneceu estável com o tempo, indicando uma cinética de adsorção muito rápida, determinada possivelmente, pela atração hidrofóbica entre defeitos sobre a bicamada, induzidos pelo sal, e a superfície do filme. Contudo, em água a adsorção de DODAB cresceu monotonicamente alcançando no máximo uma espessura de 1.6-1.8 nm (após 15 horas de interação) em função do tempo, a qual não foi consistente com deposição de bicamada. Nos estágios iniciais em água pura, a adsorção do anfifílico aumentou linearmente com a raiz quadrada do tempo, mostrando um processo controlado por difusão de vesículas, com coeficiente de difusão(D), aproximadamente igual a 1.0 x 10-11 m22s-1 em boa aproximação com valores determinados para vesículas de outros lípides por outros autores. Medidas elipsométricas sob o ar (ex- situ) de adsorção de DODAB, DHP e PC foram difíceis de realizar devido ao aumento da espessura média do filme polimérico durante o ciclo de lavagem e secagem. Na faixa de concentração de 0.1- 1.0 mM o filme adsorvido de DODAB em ar foi mais hidrofóbico (ângulo de contato de avanço ΘA= 84° ± 3°) do que aquele para o filme puro de polímero (ΘA=71 ° ± 4°). Nenhum efeito do filme de DHP sobre a molhabilidade do filme de PSA foi observado, apenas um aumento de rugosidade revelado pela mudança em ΔΘ de 2° para 11° (tabela 3). Filmes planos de PSA são hidrofóbicos(ΘA= 86° ± 5°). Após interação com PC, as superfícies tornam-se menos hidrofóbicas (ΘA= 75° ± 3°). A tensão superficial em ar-água para uma dispersão lipídica em água pura diminuiu rapidamente sob adição de sal (7-50 mM de NaCl), sugerindo a ocorrência de fusão de vesículas, induzida por sal, com a interface ar-água.O estudo da interação entre sais de DODA e partículas poliméricas por medidas de tamanho e potencial-zeta das partículas permitiu observar deposição de bicamadas optimizada por adição de sal a baixas concentrações (0.05-5.0 mM NaCl). / Determinations of surface tension (γ) at the air--water interface, contact angles (Θ), and in and ex-situ ellipsometric mean thickness (d) were used to study the interaction between dioctadecyldimethylammonium bromide (DODAB) small vesicles and spin-coated polystyrene sulfate (PSS) films on silicon wafers. Upon the adition of NaCl (50 mM final concentration) to a 0.2 mM DODAB dispersion, adsorption from vesicles on PSS films immediatly yielded a DODAB layer 6.0 nm thick which remained stable as a function of time. However, in water, in situ DODAB adsorption monotonically increased reaching at most 1.6--1.8 nm as a function of time (from 15 mm of interaction), which were not values consistent with bilayer deposition. At early stages in pure water, DODAB adsorption linearly increased with the square root of time, indicating a vesicle difision controlled process with ca. 1.0 x 10-11 m2s-1 as the vesicle diffusion coeficient (D) in nice agreement with reported D for similar vesicles. In contrast, adding 50 mM salt, resulted in a very fast adsorption kinetics determined by the hydrophobic atraction between salt-induced defects on lhe bilayer and the film surface. Ex situ measurements of DODAB, DHP e PC adsorption were difficult because wetting/drying cycles of the polimeric fiIms increased its mean thickness. From 0.1 up to 1.0 mM DODAB, the adsorbed film in air was more hydrophobic (advancing contact angle, ΘA = 84 ± 3°) than the bare PSS film (ΘA = 71 ± 4°). No effect of DHP film on the wettability of PSA film could be observed, just a increase of rougness revealed by the change of ΔΘ from2° to 11°( table 3). Pure PSA films are hydrophobic, as revealed by the mean advancing angle ΘA = 86 ± 5°. After interaction with PC, the surfaces turn less hydrophobic with a mean ΘA = 75 ± 3°. Air-water surface tension for a DODAB dispersion in pure water rapidly decreased upon salt addition (7-50 mM NaCI), suggesting salt-induced vesicle fusion wilh the air--water interface occurred, in nice agreement with saIt-induced vesicle fusion at the hydrophobic polymer-water surface.The investigation of the interaction between DODA salts and polymeric particles from diameter and zeta- potential measurements, allowed us to detect bilayer deposition optimized by salt adition in low concentration(0.05-5.0 mM NaCl).
397

Caractérisation de copolymères à blocs à base de poly(oxyde d’éthylène) et de polystyrène par des techniques de chromatographie liquide avancées / Characterization of poly(ethylene oxide) and polystyrene based block copolymers by advanced high performance liquid chromatography techniques

Rollet, Marion 17 December 2015 (has links)
Différentes techniques de chromatographie liquide des polymères ont été étudiées selon leur principe d’élution et le comportement conformationnel des polymères suscité au sein de la phase stationnaire. De part leur capacité à caractériser des copolymères à blocs, la Chromatographie Liquide aux Conditions Critiques (LC CC) et la Chromatographie Liquide aux Conditions Limites de Désorption (LC LCD) ont été utilisées pour déterminer la composition chimique de copolymères à blocs à base de poly(oxyde d’éthylène) et de polystyrène. La LC LCD s’est distinguée par sa capacité à séparer de manière efficace les copolymères à blocs de leurs homopolymères parents. Cette méthode chromatographique a ensuite été optimisée afin d’être appliquée à une plus large gamme de masses molaires. / Several advanced techniques of liquid chromatography of polymers were studied according to their elution principle and the conformational behaviour of polymers along the stationary phase. Because of their potential to characterize block copolymers, Liquid Chromatography under Critical Conditions (LC CC) and Liquid Chromatography under Limiting Conditions of Desorption (LC LCD) were employed to determine the chemical composition of Poly(ethylene oxide) and Polystyrene based block copolymers. Interestingly, LC LCD was proved to be particularly efficiently to separate block copolymers from both their parent homopolymers. LC LCD method was then optimized to extend the applicable molar masses ranges.
398

Integrisani pristup fabrikaciji složenih arhitektonskih formi od penastih polistirena primenom industrijskih robota / Integrated Fabrication Approach of Complex, Architectural Forms Made from Foamed Polystyrene Using Industrial Robots

Jovanović Marko 31 May 2018 (has links)
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Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-qformat:yes;mso-style-parent:"";mso-padding-alt:0in 5.4pt 0in 5.4pt;mso-para-margin-top:0in;mso-para-margin-right:0in;mso-para-margin-bottom:10.0pt;mso-para-margin-left:0in;line-height:115%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;}</style><![endif]--></p><p class="Default" style="text-align:justify">Integrisanjem vi&scaron;erazličitih oblasti arhitekture, poznavanja svojstava materijala, fabrikacije, zajedno sa primenom digitalnih alata, postalo je moguće lak&scaron;e I efikasnije fabrikovati složene arhitektonske forme. Primena penastog polistirena u arhitektonskoj fabrikaciji je pogodna zbog dobrih svojstava polistirena, prevashodno njegove lake obradivosti. Upotrebom zagrejane žice za obradu materijala I industrijskog robota kao ma&scaron;ine za fabrikaciju, u ovom istraživanju su pokazana tri projektantska scenarija, koja predlažu automatizovan proces fabrikovanja složenih arhitektonskih formi različitih veličina od penastog polistirena I primenom različitih strategija za fabrikaciju. Rezultati su predstavljeni u vidu fabrikovanih prototipova. <span style="mso-spacerun:yes">&nbsp;</span></p> / <p>Theintegrationofmultipledifferentfields-architecture,materialproperties,fabrication,combinedwiththeapplicationofdigitaltoolshasmadethefabricationofcomplexarchitecturalformseasyandefficient.Theapplicationoffoamedpolystyreneinarchitecturalfabricationissuitableduetothegoodpropertiesoffoamedpolystyrene,especiallytheeaseofmillingorcuttingthematerial.Inthisresearch,theapplicationofahot-wireasatoolandanindustrialrobotasafabricationmachinehasenabledthreedifferentdesignscenarios,whichsuggestanautomatedfabricationprocessforcomplexarchitecturalformsofdifferentsizes,madefrompolystyreneandbysuingdifferentfabricationstrategies.Theresultsarepresentsin a form of fabricated prototypes.</p>
399

Caractérisation mécanique et thermique de biocomposites à matrice polystyrène recyclé renforcée par des coques de cotonnier (Gossypium Hitsutum L.) ou des particules de bois de Kénaf (Hibiscus Cannabinus L.) / Mechanical and thermal characterization of biocomposite materials at matrix recycled polystyrene reinforced by the hulls of cotton (Gossypium Hirsutum L.) or particles of wood of kénaf (HibIscus Cannabinus L. ).

Soulama, Sagnaba 21 November 2014 (has links)
Dans le contexte actuel marqué par une grande émergence des questions environnementales, de l’économie circulaire et du développement durable, la mise au point d’éco-matériaux représente un enjeu majeur qui offre une alternative aux plastiques recyclés en fin de cycles de vie.L’objectif de ce travail est de contribuer au développement de deux éco-matériaux à partir des biomasses végétales cultivables non alimentaires disponibles, associées à des polymères synthétiques recyclés en fin de cycles de vie.Il s’agit d’une part, de développer un matériau biosourcé constitué de polystyrène recyclé, renforcé de coques de cotonnier. Ce matériau devra être susceptible de se substituer au polystyrène dans des domaines d’applications diverses telles que la fabrication de pièces d’isolation thermique, d’habillage intérieur de voitures, des coques de portables cellulaires, d’ordinateurs, de photocopieurs et d’emballages divers.D’autre part, de développer des panneaux de particules en bois de tiges de cotonnier et de tiges de kénaf associés à un liant naturel (la colle d’os) pour une utilisation dans le domaine de l’isolation thermique d’intérieur en remplacement des panneaux de particules élaborés avec la colle urée formaldéhyde.L’influence des paramètres d’élaboration pour chacun des deux matériaux a été analysée. Après optimisation des conditions de mise en œuvre pour chaque matériau, la tenue mécanique, les propriétés thermiques et la microstructure ont été déterminées et optimisées dans chaque cas. / In the current context marked by a large emergence of environmental issues, the circular economy and sustainable development, the development of eco-materials represents a major challenge which offers an alternative to plastics recycled at end of life cycles.The objective of this work is to contribute to the development of two eco-materials from plant biomass non-cultivable food available, associated with synthetic polymers recycled at end of life cycles.It is a part, to develop a biosourced material constitutes of recycled polystyrene, strengthened of hulls of cotton. This material will be likely to be a substitute for polystyrene in areas of various applications such as the manufacture of parts for thermal insulation, interior trim from cars, the hulls of cellular mobile, computers, photocopiers, and various packaging.On the other hand, to develop particle board in wood of cotton stems and stalks of kenaf associated with a binder natural (the glue of bone) for use in the area of the thermal insulation of interior in replacing the panels of particles prepared with glue urea formaldehyde.The influence of the parameters for the development for each of the two materials was analyzed. After optimization of conditions of implementation for each material, the holding mechanical, thermal properties and the microstructure have been determined and optimized in each case.
400

Électrofilage de fibres à partir de mélanges polystyrène/poly(vinyl méthyl éther)

Valiquette, Dominic 08 1900 (has links)
L’électrofilage est un procédé permettant de préparer des fibres possédant un diamètre de l’ordre du micromètre ou de quelques centaines de nanomètres. Son utilisation est toutefois limitée par le manque de contrôle sur la structure et les propriétés des fibres ainsi produites. Dans ce travail, des fibres électrofilées à partir de mélanges de polystyrène (PS) et de poly(vinyl méthyl éther) (PVME) ont été caractérisées. La calorimétrie différentielle à balayage (DSC) a montré que les fibres du mélange PS/PVME sont miscibles (une seule transition vitreuse) lorsque préparées dans le benzène, alors qu'une séparation de phases a lieu lorsque le chloroforme est utilisé. Les fibres immiscibles sont néanmoins malléables, contrairement à un film préparé par évaporation du chloroforme qui a des propriétés mécaniques médiocres. Des clichés en microscopies optique et électronique à balayage (MEB) ont permis d’étudier l'effet de la composition et du solvant sur le diamètre et la morphologie des fibres. Des mesures d’angles de contact ont permis d’évaluer l’hydrophobicité des fibres, qui diminue avec l’ajout de PVME (hydrophile); les valeurs sont de 60° supérieures à celles des films de composition équivalente. Un retrait sélectif du PVME a été réalisé par l’immersion des fibres dans l’eau. La spectroscopie infrarouge a montré que la composition passe de 70 à 95% de PS pour une fibre immiscible mais seulement à 75% pour une fibre miscible. Ces résultats indiquent que la phase riche en PVME se situe presque uniquement à la surface des fibres immiscibles, ce qui a été confirmé par microscopie à force atomique (AFM) et MEB. Finalement, l’effet du mélange des deux solvants, lors de l’électrofilage du mélange PS/PVME, a été étudié. La présence du chloroforme, même en quantité réduite, provoque une séparation de phases similaire à celle observée avec ce solvant pur. / Electrospinning is a simple method for the preparation of polymer fibers with diameters of hundreds of nanometers to a few micrometers. Although it is a versatile method, some issues remain in the control of the structure and properties of electrospun fibers. In this study, fibers electrospun from polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends were characterized. Differential scanning calorimetry (DSC) revealed that fibers electrospun from benzene are miscible while a phase separation occurs when the fibers are electrospun from chloroform. While films cast from chloroform show poor mechanical properties, immiscible fibers are ductile. The effects of the blend composition and the solvent on the fiber diameter and morphology were observed by scanning electron microscopy (SEM) and optical microscopy. Afterwards, contact angle measurements were made to evaluate the hydrophobicity of the fibers which decreases as hydrophilic PVME is added to the blend; the values for the fibers were found to be 60° higher than their equivalent in films. PVME was selectively removed from the immiscible fibers by complete immersion into water. Infrared spectroscopy revealed that this process increases the PS content from 70 to 95% for immiscible fibers but only to 75% for miscible fibers. These results show that the PVME-rich phase is almost completely distributed on the fiber surface, which was confirmed by atomic force microscopy (AFM) and SEM. Finally, the electrospinning of PS/PVME blends from chloroform/benzene solutions was studied. The presence of chloroform, even as a residual amount, causes a phase separation just as it does in fibers electrospun from pure chloroform.

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