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Lineton, Warran Boyd. "An investigation into dry and wet textile friction and lubrication in practical applications." Thesis, De Montfort University, 1999. http://hdl.handle.net/2086/10707.
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The lubrication of dry viscose fibres by a two component finish, and the lubrication of wet Iyocell fabric against metal, with various aqueous lubricant systems, has been studied. Secondary ion mass spectrometry (SIMS) was investigated as a means of providing direct chemical information from finished fibre surfaces. The composition and distribution of a two component finish applied to viscose fibres was determined successfully. When applying finish from a bath, the surface composition of the finished fibres was not controlled by the bath conditions. Increasing the concentration of finish in the bath did, however, increase the total amount of finish deposited, and increasing the concentration of antistat relative to lubricant in the bath increased the amount of antistat relative to lubricant deposited on the finished fibres. Fibre friction was determined using the capstan method. The friction forces, measured for finished viscose fibres, were correlated with the finish application conditions. Increasing the emulsion concentration in the finish bath reduced fibre/metal friction, but finish component ratio, emulsion concentration, dip time and bath temperature did not affect fibre/fibre friction. Spray applying the finish resulted in unfinished regions on the fibre surfaces and the electrical resistance of fibre bundles was not reduced. Bath application of finish did lower electrical resistance in comparison with unfinished fibre, but none of the bath deposition variables had a significant effect on electrical resistance.
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Monteiro, Marques Filipa. "Etude des structures textiles linéaires soumises à des sollicitations rapides : cas des dils et filés de viscose." Mulhouse, 2001. http://www.theses.fr/2001MULH0629.
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Les fibres et les filaments textiles sont soumis lors de leur transformation en filés et en fils à des sollicitations très sévères. Le niveau de sévérité des sollicitations s'élève lors de la transformation des textiles linéaires en textiles surfaciques surtout lors du tissage. Dans cette opération, les structures sont soumises à des extensions répétées de fréquences élevées avec une élongation élevée. Ce phénomène provoque des casses nuisibles au bon fonctionnement du processus et une modification de la structure du matériau en cours d'élaboration, voir une déstructuration de celui-ci. Ce phénomène a été analysé au moyen d'un dynamomètre rapide soumettant les textiles linéaires à des F- compris entre 0,01 et 220s-1. Une méthodologie d'essai a été définie et le comportement de matériaux filamentaires tels que le polyester et le polyamide modélisé en fonction du titre du fil, du nombre de filaments et de la torsion. Des modèles de type pseudoplastiques et logarithmiques permettent une bonne approche du comportement des fils étudiés. Les modèles analogiques ne sont pas satisfaisants, mais en revanche, un modèle de Eyring à amortisseur hyperbolique donne une bonne approche. A partir de ces résultats, le comportement de deux matériaux synthétiques a été étudié, ainsi qu'un matériau artificiel viscose. Celui-ci se présente sous deux formes, filaments et filés de fibres de mêmes titres, mais de torsions différentes, de type Ring-Can. Ces fils et filés ont été soumis à des. F- compris entre 0,01 et 220s-1 et différentes lois de comportement ont été proposées. Une analyse des faciès de rupture au MEB à permis de mettre en évidence le mode de rupture et la vitesse de sollicitation limite à partir de laquelle le matériau passe du ductile au fragile. Cette étude a permis d'une part de corréler le comportement du fil avec les casses se produisant pendant le processus de fabrication et d'autre part de déterminer les caractéristiques de la forme de rupture du matériau.
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Revol, Baptiste Paul. "Caractérisation de l'interface dans des composites polyamides-6 - viscose haute ténacité obtenus par injection réactive." Thesis, Mulhouse, 2017. http://www.theses.fr/2017MULH0358/document.
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Des composites polyamide-6 renforcés fibres de verre obtenus par injection réactive ont été caractérisés afin de remplacer ces fibres synthétiques par des fibres biosourcées de viscose haute ténacité. La première étape a été l’étude physico-chimique des fibres et de la matrice polymère thermoplastique par des techniques multiples : DSC, ATG, essais mécaniques, FTIR, RMN et mesure d’angle de contact. Afin d’améliorer l’interface entre la viscose haute ténacité et le polyamide-6, les fibres de viscose ont été fonctionnalisées en deux étapes. Premièrement, un traitement plasma oxygène a permis le nettoyage de la surface de ces fibres. Elles ont été ensuite fonctionnalisées par un agent de couplage silane. Une nouvelle méthode de dépôt de microgouttes de polymère sur les fibres a été développée, dans des conditions représentatives de l’injection réactive, afin de vérifier l’avantage d’un traitement de surface des fibres. Cette approche permet de déterminer la résistance au cisaillement interfacial entre les fibres et le polyamide-6, par déchaussement des microgouttes. Par la suite, des composites polyamide-6 renforcé viscose traitée ou non traitée ont été obtenusPolyamide-6 / glass fibers composites were studied in order to replace glass fibers with high tenacity viscose as a reinforcement, using a reactive injection process. The first step was the physico-chemical characterization of fibers and matrix using different techniques such as: DSC, TGA, mechanical testing, FTIR, NMR and contact angle measurements. In order to improve the interface between high tenacity viscose and polyamide-6, the viscose fibers were functionalized using a two step method. First, oxygen plasma was applied as a cleaning process to remove impurities. Secondly, the fibers were functionalized using an aminosilane. A new deposition technique of polymer microdroplets onto fibers, in conditions similar to these of reactive injection process, was developed in order to confirm the advantages of the silane treatment. Moreover, a pull-out test of these microdroplets led to the determination of the interfacial shear strength between polyamide-6 and high tenacity viscose fibers. Then, polyamide-6 composites reinforced with high tenacity viscose were obtained
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Freeman, John James. "Studies in the development and modification of pore structure in activated viscose rayon chars." Thesis, Brunel University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235895.
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Eriksson, Johanna. "Pilot spinning of viscose staple fibres : Screening for imoprtant spinning parameters using design of experiments." Thesis, Umeå universitet, Kemiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105912.
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Bouyer, Baptiste. "Étude et modélisation numérique des transferts de chaleur et des transformations lors de la carbonisation de fibres de précurseur." Thesis, Nantes, 2020. http://www.theses.fr/2020NANT4010.
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Au cours de ces travaux, les propriétés thermophysiques du toron de viscose ainsi que leurs évolutions pendant la carbonisation ont été étudiées. Des analyses thermiques ATG et DSC ont ainsi permis d’identifier la capacité thermique apparente du toron et les sources de chaleur liées aux transformations du précurseur. Le rapprochement de l’analyse ATG, mesures du retrait et de l’évolution du diamètre des fibres ont ensuite permis de déterminer l’évolution de la masse linéique et de la masse volumique du toron. Les propriétés radiatives du toron de viscose ont également été mesurées à différents stade de carbonisation. Un dispositif de mesure de conductivité thermique longitudinale effective de toron à été développé, réalisé et utilisé pour caractériser l’évolution de la conductivité thermique du toron au cours de la carbonisation. Un modèle numérique par éléments finis du procédé de carbonisation à été réalisé, en utilisant les propriétés précédemment mesurées et les mesures de vitesse de l’écoulement d’azote dans le four et du profil de température à la paroi réalisées sur le four de carbonisation de laboratoire. Ce modèle a été validé avec des mesures de températures réalisées au cœur du toron au cours de la carbonisation. Les transferts de chaleur lors de la carbonisation de fibres de précurseurs ont finalement été étudiés à l’aide du modèle numérique développéDuring this work, the thermophysical properties of the viscose strand as well as their evolution during carbonization have been studied. ATG and DSC thermal analyzes have made it possible to identify the apparent thermal capacity of the strand and the heat sources linked to transformations of the precursor. The comparison of the ATG analysis, measurements of the shrinkage and the evolution of the diameter of the fibers then made it possible to determine the evolution of the linear density and the density of the strand. The radiative properties of the viscose strand were also measured at different stages of carbonization. A device for measuring the effective longitudinal thermal conductivity of the strand has been developed, built and used to characterize the evolution of the thermal conductivity of the strand during carbonization. A finite element numerical model of the carbonization process has been developed, using the previously measured properties and the measurements carried out on the laboratory furnace: the velocity profile of the nitrogen flow in the furnace as well as the wall temperature profile. This model has been validated with temperature measurements made at the core of the strand during carbonization. Heat transfers during the carbonization of precursor fibers have been finally studied using the developed numerical model
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Daieff, Marine. "Deformation and shape of flexible, microscale helices in viscous flows." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC189/document.
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Les interactions fluide-structure sont d'un grand intérêt en ingénierie et pour des applications industrielles et médicales. Comprendre les interactions entre des particules aux formes complexes et des écoulements peut mener à de nouveaux projets pour l'administration ciblée de médicaments, pour des micro capteurs de débit et à une meilleure compréhension du comportement des micro-organismes. Dans cette thèse, nous étudions l'interaction fluide-structure de particules chirales de taille microscopique à bas nombres de Reynolds. Les particules sont rigides et confinées dans une géométrie 2D ou flexibles avec une forme hélicoïdale. Combiner des techniques de microfabrication, comme des méthodes d'assemblage multi-échelles et la microfluidique, permet d'avoir un excellent contrôle à la fois sur les propriétés géométriques et mécaniques des fibres et aussi sur les caractéristiques de l'écoulement comme ses propriétés Newtoniennes et non Newtoniennes, sa vitesse et sa géométrie. Dans un premier temps, nous avons étudié des fibres rigides, 2D et asymétriques, i.e. des fibres en L. Les confinements latéral et transversal ont été étudiés tout comme la forme de la fibre. Lorsque la particule est transportée dans un écoulement visqueux, elle tourne jusqu'à atteindre une orientation d'équilibre. Dans cette orientation particulière, la fibre se décale vers les murs latéraux du canal. Une étude complète des trajectoires de la fibre a été réalisée et des comparaisons avec des particules symétriques ont été faites. Ce sujet de recherche pourrait aider à concevoir des dispositifs pour trier des particules à des fins médicales. Dans un second temps, nous avons étudié des fibres hélicoïdales flexibles de taille micrométrique. La dynamique de formation de l'hélice a été analysée. Les hélices se forment à partir de rubans droits 2D qui, de façon spontanée, s'enroulent quand ils sont libérés dans l'eau. La forme hélicoïdale est obtenue seulement quelques minutes après la libération des rubans mais l'hélice continue à rétrécir pendant plusieurs heures jusqu'à ce qu'elle atteigne une courbure préférentielle. Deux temps caractéristiques sont identifiés dans cette dynamique de formation. Un modèle a été développé pour comprendre le complexe équilibre entre les forces élastiques, de tension de surface et visqueuses aux temps courts. Après avoir analysé plusieurs hypothèses, comme l'impact d'une couche sacrificielle, une possible modification du module du matériau et la présence de fluage, l'évolution du rayon de l'hélice aux temps longs s'explique probablement par du fluage. La dynamique d'extension et de relaxation de la fibre flexible a aussi été étudiée dans des fluides Newtonien et non Newtonien. L'étude dans des solutions de polymères est pertinente et intéressante car la taille des micro hélices est comparable à celle des flagelles des micro-organismes et à celle de chaînes de polymères de grande masse moléculaire. Il s'agit donc d'un problème mutli-échelles complexe car la viscosité locale au niveau du ruban pourrait être différente de la viscosité globale de l'écoulementFluid-structure interactions are of wide interest in engineering, industrial and medical applications. Understanding the interactions between complex shaped particles and flows might lead to new designs for targeted delivery, microflow sensors and to a better understanding of the behavior of microorganisms. In this thesis, we study the fluid-structure interaction of microscale chiral particles at low Reynolds numbers. The particles are rigid and confined in a 2D geometry or flexible with a helical shape. The combination of microfabrication techniques, such as multiscale assembly methods and microfluidics, enables to have a perfect control on both the geometrical and mechanical properties of the fibers and the flow features such as Newtonian or non Newtonian properties, the flow velocity and the flow geometry. First we studied asymmetric 2D rigid fibers, i.e. L-shaped fibers. Both lateral and transversal confinements have been investigated, as well as the shape of the fiber. When the particle is transported in viscous flows, it rotates until reaching an equilibrium orientation. In this specific orientation, the fiber drifts towards the lateral walls of the channel. A full investigation on the trajectories of the fiber has been performed and comparisons with symmetric particles have been done. Such research may help design devices to sort particles for medical purposes. Secondly we studied flexible microscale helical fibers. The dynamics of the helix formation has been investigated. The helices are formed from straight 2D ribbons, which spontaneously coil when released in water. The helical shape is reached only several minutes after the release but the helix keeps shrinking during several hours until reaching a preferred curvature. Two different timescales are identified in this formation dynamics. A model has been developed to understand the complex balance between elastic, surface tension and viscous forces at short times. After investigating several assumptions such as the impact of a sacrificial layer, a possible change in the modulus of the material and a creep behavior, the evolution of the radius at long times is most likely explained by creep. The extension and relaxation dynamics of the flexible fiber has also been studied in Newtonian and non Newtonian fluids. The study in polymer solutions is relevant and interesting because the size of the microhelix is comparable to the flagella of microorganisms and to the chains of high molecular weight polymers. Complex multiscale problems are then involved as the local viscosity at the scale of the ribbon might differ from the global viscosity at the scale of the flow
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Svensson, Karin, and Elin Magnusson. "BAMBUVISKOS : En hållbar fiber för framtiden?" Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17102.
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Naturskyddsföreningen gav författarna uppgiften att undersöka förekommande viskosprocesser och alternativa regenereringsprocesser, detta för att identifiera hur hållbara de är ur ett miljöperspektiv och vilka processer som går att applicera på bambu. Detta för att se möjligheten att märka bambuviskos med Bra Miljöval och för att klargöra frekvent uppkommande frågor angående bambuviskos. Syftet är att se på de olika processernas kemiska innehåll samt vilka utsläpp de orsakar till luft och vatten. Ett delmål med rapporten är att den ska kunna användas som material vid vidareutveckling av kriterierna för Bra Miljöval Textil. Resultat som erhållits vid jämförelser av studerad litteratur är att de betydande faktorerna för miljöpåverkan från massaframställningen samt viskos- och lyocellprocessen beror av: använda kemikalier i processen, energianvändningen och vilken typ av energi, möjligheten till rening av utsläpp till luft och vatten samt återvinning av energi och kemikalier. Beroende på vilket råmaterial som används vid massaframställningen kan skillnader i markanvändning, användning av bekämpningsmedel och gödningsmedel samt upptagande av koldioxid skilja sig. Massa- och fiberframställning bör vara integrerade då energiförbrukning och mängd kemikalier kan minskas. Energin kan dessutom återvinnas till större utsträckning.Genom miljömärkningar från oberoende organisationer blir det lättare för konsumenter att göra miljömedvetna val och veta vad märkningarna står för. Sammanfattningsvis ska det påpekas att om regenererad bambu framställs som den görs idag är den ingen hållbar fiber, men sker framställningen i en integrerad process där kemikalier och energi återvinns samt rening av utsläpp till luft och vatten sker, kan bambuviskos bli en hållbar fiber för framtiden. The Swedish Society for Nature Conservation (SSNC) gave the authors the task to investigative present viscose processes and alternative regeneration processes to identify how sustainable they are from an environmental perspective, and examine which processes that can be applied to bamboo. This to see the possibility to label bamboo viscose with “Bra Miljöval” (Good Environmental Choice), which is the eco-label of SSNC, and to clarify the frequently emerging issues concerning bamboo viscose. The aim is to look at the various processes, their chemical content and the emissions they cause to air and water. Another objective of the report is that it can be used as material for further development of the criteria for “Bra Miljöval”.Results obtained when comparing the studied literature is that the significant factors of the environmental impact from the pulp production, the viscose and lyocell processes depends on: chemicals used in the process, energy and energy source, the possibility of purifying emissions to air and water and recycling of energy and chemicals. Depending on the raw materials used for pulp production, differences in land use, use of pesticides and fertilizers as well as absorption of carbon dioxide differ. Pulp and fibre production should be integrated to reduce energy consumption and the amount of chemicals used. The energy can also be recycled to a greater extent.Eco-labels from independent organizations will make it easier for consumers to make environmentally conscious choices and be aware of what the labels stand for.In conclusion, it should be noted that if the regenerated bamboo is produced as it is today, it is not a sustainable fibre. If the production is done through an integrated process in which chemicals and energy recovery and purification of air and water occurs, bamboo viscose can be a sustainable fibre for the future.Program: Textilingenjörsutbildningen
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Aragão, Guilherme Hodas. "Estudo comparativo das características das malhas fabricadas com fibras de viscose e de viscose de bambu." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/100/100133/tde-18082015-152720/.
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A preocupação mundial em relação aos impactos ambientais e seus reflexos positivos ou negativos na natureza têm mobilizado diversos setores da indústria. O processo de fabricação da viscose quando não controlado é altamente poluidor, causando impactos ao meio ambiente. Portanto, a escolha da sua matéria-prima pode amenizar esses problemas. O objetivo deste trabalho é analisar comparativamente os tecidos de malha fabricados com fibras de viscose convencional eucalipto e outras - com fibras de viscose obtidas a partir do bambu. Para a análise foram escolhidas as seguintes matérias-primas: fios 100% viscose convencional (fiação de anéis e jato de ar) e fios 100% viscose de bambu (fiação de anéis) e fabricadas malhas com gramaturas médias estatisticamente iguais. Os tecidos foram beneficiados e realizados os ensaios de gramatura, tendência à formação de pilling e resistência à solidez à água. Os resultados experimentais mostraram que não existem diferenças significativas entre as características estudadas.The global concern regarding the environmental impacts has assembled several industry sectors. This study has as a goal to analyze relatively two types of mesh fabrics: viscose, which can be produced through cellulose regeneration obtained by bamboo or from other trees or plants, and thus, it can be chosen one or the other within a sustainable development context. This manufacturing process of viscose is highly pollutant, provoking negative impacts to the environment. Therefore, the choice of raw material might reduce these issues relating to sustainability. This comparison also has an objective to open a space for discussions regarding to sustainability concept in textile sector, which many studies are limited to analyze the results comparing materials only, not considering the process as a whole, from the choice of raw material, obtention, cultivation, transformation, to the final product, including the lifecycle, the durability and disposal of a fashion product. The experimental results showed that no significant differences between the characteristics studied.
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Panda, Satyananda. "The dynamics of viscous fibers." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979183138.
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Harris, Samantha Mary. "Dynamics of semi-flexible fibres in viscous flow." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/53/.
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The dynamics of semi-flexible fibres in shear flow and the effect of flexibility on the swimming speed of helical flagella are investigated. High aspect ratio particles such as carbon and glass fibres are often added as fillers to processed polymers. Although these materials have high rigidity, the large aspect ratiomakes the fibres liable to bending during flow. Other high aspect ratio fibres that behave as semi-flexible fibres include carbon nano-tubes, paper fibres and semi-flexible polymers such as the muscle protein f-actin. Most theoretical studies assume that fibres are either rigid or completely flexible, but in this thesis fibres with a finite bending modulus are considered. A semi-flexible fibre is modelled as a chain of shorter rods linked together. A bending torque is included at the joints between the rods to account for the rigidity. In shear flow the simulation reproduces the C and S turns observed in experiments on semi-flexible fibres. The results for finite aspect ratio fibres predict changes to the period of rotation and drift between Jeffery orbits. The direction of drift for a flexible fibre depends on both the intial orientation and the fibre’s flexiblity. We also present a linear analysis of how small distortions to a straight semi-flexible fibre grow when the flow places the fibre under compression. These results are in agreement with our full simulations and the growth rates of the distortions to a straight fibre allow us to predict the most unstable mode at a particular flow rate. To allow for intrinsically bent or helical equilibrium shapes a second simulation method is developed that includes a twisting torque at the joints between the rods as well as a bending torque. Using this simulation we measure the period of rotation and orbit drift of permanently deformed fibres in shear flow and show that due to the asymmetry of a helix, shear induced rotation results in translation and orbit drift for both rigid and semi-flexible fibres. Bacteria such as Vibrio alginolyticus and Escherichia coli swim by rotating one or more helical flagella. Vibrio alginolyticus has only one flagella and changes direction by altering its sense of rotation. Experimental observations of Vibrio alginolyticus have found that backwards swimming is 50% faster than forwards swimming speed however, previous numerical simulation results have shown only a 4% difference for flagella of the same dimensions. We use our simulation to consider how flexiblity affects the swimming speed of helical flagella and show that for a constant angular velocity, difference between forwards and backwards swimming speed ranges between 0-23%depending on the exact stiffness chosen. We explain the differences in swimming speeds of semi-flexible fibres by investigating the shape changes which occur and comparing them to the results for swimming speeds of rigid flagella of varying dimensions.
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Holloway, Craig Roy. "Stability of fibre-reinforced viscous flows." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7427/.
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This thesis focusses on two models (inactive and active) for fibre-reinforced viscous flows, examples of which may be found in numerous industrial and biological applications. In chapters 2-4 we consider Ericksen's model for a transversely isotropic fluid, which treats suspensions of nonmotile particles as a continuum with an evolving preferred direction; this model describes fibrous materials as diverse as extracellular matrix, textile tufts and cellulose microfibers. Linear stability analyses of transversely isotropic viscous fluid between two rotating co-axial cylinders and two horizontal boundaries of different temperatures are undertaken in chapters 3 and 4 respectively. In both cases, the inclusion of transversely isotropic effects delays the onset of instability. In chapter 5 we describe a framework commonly used to model active suspensions, which has been applied to suspensions of self-propelling bacteria, algae and sperm, and artificial swimmers. Through linking this model for an active suspension with that for a transversely isotropic fluid, we identify previously neglected components of the stress tensor that significantly alter the rheology. In chapter 6 we examine the linear stability of isotropic and nearly-aligned suspensions of elongated particles, before giving a summary of our findings in chapter 7.
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Santos, Jessica Almeida. "Efeito dos parâmetros da qualidade da pasta solúvel no fabrico de viscose." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22618.
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Mestrado em Engenharia QuímicaA pasta solúvel é um tipo de pasta celulósica que possui mais de 90% de celulose pura, sendo que cerca de 77% deste tipo de pasta é usada para produzir fibras celulósicas, como a viscose que é utilizada principalmente na indústria têxtil. A caracterização da pasta solúvel é feita recorrendo a diversos parâmetros, nomeadamente a reatividade, viscosidade intrínseca, conteúdo de α-celulose, resistências alcalinas (R10 e R18) e teor de pentosanas, sendo que estes parâmetros são muito importantes no que diz respeito à qualidade de viscose produzida posteriormente, que irá ter influência nas fibras têxteis de viscose. Neste trabalho pretende-se relacionar os parâmetros de qualidade da pasta solúvel com a produção de fibras de viscose, de forma a perceber quais os parâmetros que têm uma maior influência na qualidade das fibras produzidas. Para isso selecionaram-se quatro tipos de pastas diferentes com extremos no que diz respeito aos valores dos parâmetros de qualidade, tendo a viscosidade intrínseca variado entre 465 e 595 𝑚𝐿𝑔⁄, o teor de pentosanas entre 2,7 e 3,4 %, a reatividade entre 51,2 e 67,3 %, o valor de R10 entre 90,1 e 91,3%, o valor de R18 entre 94,4 e 95,2 % e o teor de alfa-celulose entre 91,9 e 92,5% tendo-se posteriormente produzido fibras têxteis de viscose a partir dessas mesmas pastas para que se pudesse avaliar a qualidade dessas fibras. Para determinar a sua qualidade recorrem-se a várias técnicas diferentes que fornecem informações acerca de vários parâmetros importantes a saber acerca de fibras têxteis. Foram realizados ensaios mecânicos através dos quais se obtiveram os valores de tenacidade das fibras, que traduzem a força necessária para levar as mesmas à rutura. Foram feitos igualmente outros ensaios, nomeadamente observações microscópicas nas quais se observa a disposição das fibras, o seu diâmetro e a sua forma. A estrutura física da celulose regenerada (viscose) foi avaliada através de análises FTIR-ATR e Raios-X. Ao relacionar a tenacidade das fibras produzidas com os parâmetros de qualidade previamente estudados de cada pasta verificou-se que o parâmetro que mais influência tinha na tenacidade era o grau de polimerização, o que seria de esperar visto que quanto maior o grau de polimerização maior será o peso molecular das cadeias poliméricas e portanto mais fortes serão as fibras produzidas. A análise microscópica das fibras foi de encontro ao facto que a tenacidade está relacionada com a morfologia das fibras formadas, havendo uma relação entre a uniformidade em espessura e na estrutura interior dos fios observados e as suas resistências. Para além disso a observação da secção transversal indica que a forma das fibras é semelhante ao que se esperaria de fibras de viscose. A análise FTIR-ATR mostrou a semelhança geral das fibras revelando certas diferenças no teor de celulose cristalina nas fibras. Através da análise da dos Raios-X determinou-se o índice de cristalinidade que demonstrou que as fibras mais cristalinas seriam as da pasta Composta com maior viscosidade, que tinha maior grau de polimerização, para além disso verificou-se que estas fibras tinham um empacotamento das moléculas, no plano 1-10 da estrutura da celulose, diferente das outras fibras o que levava a que estas fossem fibras mais densas. Uma conclusão geral que se retirou através de todas as análises foi que para pastas com os parâmetros de qualidade na gama de valores correspondentes às pastas de 16/02/2017 e 10/02/2017 (viscosidade 500-550 mL/g, reatividade> 60% e filtrabilidade até 50 s), a qualidade das fibras têxteis vai ser bastante satisfatória.
Dissolving pulp is a type of cellulosic pulp that has more than 90% of pure cellulose, about 77% of this type of pulp is used to produce cellulosic fibers, such as viscose which is mainly used in the textile industry. The characterization of the dissolving pulp is made using several parameters, such as reactivity, intrinsic viscosity, α-cellulose content, alkaline resistances ( R10 e R18) and pentosan content, being these parameters very important with regard to quality of viscose subsequently produced, which will have influence on the viscose textile fibers. In this work it is intended to relate the quality parameters of the dissolving pulp with the production of viscose fibers, in order to understand which parameters have the biggest influence on the quality of the fibers produced. For this purpose, four different types of pulps with extremes with regard to quality parameters were selected, being intrinsic viscosity ranging from 465 to 595 𝑚𝐿𝑔⁄, pentosan content between 2,7 and 3,4%, the reactivity between 51,2 and 67,3 %, the R10 value between 90,1 and 91,3%, the R18 value between 94,4 and 95,2 % and the alpha-cellulose content between 91,9 and 92,5%, and latter viscose textile fibers were produced from these same pulps in order to evaluate the quality of these fibers. To determine their quality various techniques are used which provide information about several important parameters that should be known about textile fibers. Mechanical tests were carried out through which tenacity values of the fibers were obtained, which translate the strength necessary to bring them to breakage. Other analysis have also been carried out such as microscopic observations in which the arrangement of the fibers, their diameter and their shape is observed. The physical structure of regenerated cellulose (viscose) was evaluated through FTIR-ATR and X-Ray. By relating the tenacity of the fibers produced with the previously studied quality parameters of each pulp, it was verified that the parameter that had the greatest influence on the tenacity was the degree of polymerization, which would be expected since the higher is the degree of polymerization the higher is the molecular weight of the polymeric chains and therefore the stronger the fibers produced. The microscopic analysis of the fibers was in agreement with the fact that the tenacity is related to the morphology of the formed fibers, having a relation between the uniformity in thickness and the internal structure of the observed wires and its resistances. In addition to that, the observation of the cross section indicates that the shape of the fibers is similar to what would be expected of viscose fibers. The FTIR-ATR analysis showed the general similarity of the fibers revealing some differences in the crystalline content in the fibers. The crystallinity index determined through X-ray analysis, showed that the most crystalline fibers were from the Composta pulp with higher viscosity, which had a higher degree of polymerization, and it was found that these fibers had a packaging of the molecules, in plane 1-10 of the structure of the cellulose, different from the other fibers which meant that these were denser fibers. A general conclusion that was drawn through all the analyzes was that for pulp with de quality parameters in the range of values corresponding to the pulps of 16/02/2017 and 10/02/2017 (viscosity 500-550 mL/g, reactivity> 60% and filterability up to 50s) , the quality of the textiles fibers will be very satisfactory.
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ALI, MAJID. "PEDOT Coated Viscose Fibers by Optimized OCVD Process : Washing and Stretch Sensing Properties." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17482.
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Electroactive textile fibers are key components in smart and interactive textile applications. In previous research on textile base conductive fibers, viscose fibers were coated with poly (3,4-ethylenedioxythiophne) (PEDOT) using oxidative chemical vapor deposition (oCVD) technique[1]. Ferric chloride was used as oxidant and reaction conditions were optimized at which better electrical as well as mechanical properties of conductive viscose fibers could be achieved. In this thesis work, effect of new parameters such as pretreatment of viscose fibers with solvents, drying of oxidant treated viscose fibers at different time and temperature and comparison of two different oxidants have been tried. One new and important oxidant, ferric (III) p-toluene sulfonate or ferric (III) tosylate, used to prepare PEDOT coated viscose fibers and then compared with PEDOT coated viscose fibers prepared using oxidant ferric (III) chloride. Viscose fibers have been treated with two well know solvents, acetone and ethyl acetate before soaking in oxidant solution. Oxidant enriched fibers dried at different temperature for variable time prior to polymerization step. Knitted structures of conductive viscose fibers have been prepared. Hand washing of PEDOT coated viscose fibers with tap water and machine washing of knitted structures according to the international standard ISO EN-6330 have been performed and washing effects were investigated. Effects of all of the above mentioned variables on electromechanical properties of PEDOT coated viscose fibers were studied by using tensile testing, TGA analysis, FTIR spectra and conductivity measurements. Stretch sensing properties of knitted structures; before and after washing, were determined on cyclic tester. The purpose of this study is to enhance the properties of PEDOT-coated viscose fibers by controlling different parameters and to evaluate their usage as stretch sensors as well as to check the washability of PEDOT coated viscose fibers and knitted structures. Better electromechanical properties were achieved on new parameters and PEDOT coated viscose fibers were successfully utilized as stretch sensors. PEDOT coated viscose fibers could have potential to apply in areas such as, military textiles, medical textiles and sensors.Program: Master programme in Textile Technology
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Iqbal, Shoaib, and Zuhaib Ahmad. "Impact of degree or Polymerization of Fiber on Viscose Fiber Strength." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-20861.
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The aim of the study was to find out the relationship between the DP and the tensile properties of different regenerated cellulose fibers. During the process to make regenerated cellulose fibers from wood, the reduction in DP of cellulose is a necessary process to enable fiber extrusion. The reduction of the DP is usually from 1000 to 350 (Coley 1953). The reduction in DP is necessary, first to make the cellulose soluble, and then further decrease in DP is required to control the viscosity of the solution to minimize the mechanical difficulties during processing faced. It is a fact that the reduction in DP is a compromise which is necessary, as reduction in DP means reduction in tensile properties of the fiber produced. The reduction in DP is optimized to make the process both processing and the final product more feasible. The relation in DP and the strength of the fibers is rather obvious i.e. higher the DP higher the tensile strength, but researchers have different views regarding the relationship. By the experiments performed by us we tried to come to a conclusion regarding the difference in opinions. Different types of regenerated cellulose fibers were collected from various sources. Both wet and dry tenacities of 19 different viscose, bamboo viscose, kupro viscose, modal and Tencel fibers were determined. The fiber linear density was also measured, but for some samples we had to take the fiber density value as provided by the manufacturer, due to the limitation of the instrument regarding the fiber length and low fiber linear density. Then out of all the samples 10 were selected (based on our and company’s interest). SEC analysis was used to determine the DP of the samples. These tests were not carried out by us but by MoRe Research. The results of both the analysis were gathered, analyzed and commented upon.Program: Master Programme in Textile Technology
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Coda, Ryan. "A Study of Cellulose Based Biodegradable Foams and Sponges." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6961.
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Environmental concerns have brought about a push to replace non-biodegradable products that are made from non-renewable resources. Investigations regarding use of wood fibers and other biomass as a raw material for biodegradable foams and sponges are an example of such a replacement. Foams made at least partially of biomass can be created using cellulose from wood fibers once the cellulose is converted into a fluid form. Polyurethane foams can be made from polyols containing as much as 50% biomass by combined dissolution of wood and starch. Sponges can be made completely from cellulose regenerated from a viscose rayon solution, and the effect of using wood fibers as reinforcement material within the cellulose matrix of such sponges was studied. The effect of fiber content and fiber length on absorbance, swelling, density, air to cellulose ratios, bound water, and tensile was determined.
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Burgarella, Boris. "Comportement visco-élastique effectif d'un thermoplastique thermostable renforcé par des fibres courtes." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0004.
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Le secteur des transports aéronautiques, navals et terrestres fait de plus en plus appel pour les pièces d'habitacles ou de structure à des composites techniques de type thermoplastique thermostable renforcé par des fibres courtes. Ces matériaux alliant légèreté et résistance présentent l’intérêt majeur d’une meilleure recyclabilité d’une facilité de mise en œuvre et de maintenance que les matrices thermodurcissables dans les composites classiques. Toutefois, le développement de modèles de comportement dans le but de dimensionner des structures reste un véritable challenge. L’objectif de cette thèse concerne la modélisation du comportement de ce type de composite soumis à des chargements monotone et cyclique. Une étude expérimental a permis la détermination du comportement de chacun des constituants du composite. Leur comportement a ensuite été utilisé dans un calcul d'homogénéisation en champs complet basé sur une méthode FFT. Le comportement du composite est ensuite modélisé à l'aide d'un modèle visco-élastique spectral. Finalement, l'évolution des paramètres de ce modèle est étudiée en faisant varier la microstructure du composite (taux de fibre, dispersion d'orientation) afin d'établir un méta-modèle permettant de prédire le comportement du composite rapidement, et efficacementTransportation industries uses more and more composite materials each year. These composite materials provide a good alternative to classic materials thanks to their good specific resistances and stiffness. Short fiber composite materials and well suited for automotive applications, thanks to their ability to be used in injection process inducing very short fabrication cycles. But, the modeling of the behavior of these materials remains a challenge to this day. In this PhD work, an experimental characterization of a PEEK / short glass fiber composite has been conducted. A precise study of the PEEK behaior have also been conducted. The PEEK behavior was then used in an full field homogenization method based on FFT to obtain an effective behavior of the composite. A visco-elastic model was then used to model its behavior. Finally, a meta-model is build to accelerate the modeling process by studying the variation of the composite behavior with its microstructure parameters
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Harry, I. D. "Modification and characterisation of carbon fibre ion exchange media." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/14123.
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This thesis examines the use of electrochemically treated viscose rayon based activated carbon cloth (ACC) for the removal of metal ions from aqueous effluent streams. Two types of treatment were performed: (i) electrochemical oxidation and (ii) electrochemical reduction to enhance cation and anion sorption capacities of the ACC, respectively. Electrochemical oxidation resulted in a loss of 61% BET surface area due to blockage of pores through formation of carboxylic acidic groups but its cation exchange capacity and oxygen content increased by 365% and 121%, respectively. The optimum constant current at which a combination of applied current and oxidation time at any extent of oxidation to produce ACC of maximum cation exchange capacity was found to be 1.1 A, with voltage of 4.2 V and current density of 0.8 mA/m2. Batch sorption experiments showed that the maximum copper and lead sorption capacities for electrochemically oxidised ACC increased 17 and 4 times, respectively, for noncompetitive sorption and 8.8 and 8.6 times, respectively for competitive sorption. Therefore, electrochemically oxidised ACC is an effective adsorbent for treating aqueous solution contaminated with copper/lead in both single component and multi-component systems. Industrial wastewaters are multicomponent systems, therefore, electrochemical oxidation of ACC is an efficient way of enhancing lead and copper ions sorptive capacity for industrial wastewater treatment. Electrochemical reduction resulted in a loss of 28% BET surface area due to formation of ether groups but its anion exchange capacity increased by 292%. The optimum constant current at which a combination of applied current and reduction time at any extent of reduction to produce ACC of maximum anion exchange capacity was found to be 5.5 A, with voltage of 9.8 V and current density of 6.4 mA/m2. Batch sorption experiments showed that the maximum chromium(VI) sorption capacity for electrochemically reduced ACC increased 2.12 times, with highest maximum chromium(VI) sorption capacity of 3.8 mmol/g at solution pH 4. Most industrial wastewaters contaminated with chromium(VI) are highly acidic, therefore, electrochemical reduction of ACC is an efficient way of enhancing chromium(VI) sorptive capacity for industrial wastewater treatment.
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Stochioiu, Constantin. "Contribution à l’étude du comportement visco-élastoplastique d’un composite structural lin/époxy." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCK023.
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L’étude présenté dans ce manuscrit s’inscrit dans le contexte global du développement de nouveaux matériaux, ayant une empreinte environnementale réduite. Parmi les possibilités actuellement explorées (notamment en Europe), les composites à renfort de fibres de lin sont une solution prometteuse. En effet, la faible densité et les propriétés mécaniques élevées des fibres de lin, ainsi que leur faible coût énergétique, permettent d’envisager leur utilisation dans des composites structuraux, en remplacement des fibres de verres. Ces composites bio-sourcés font déjà l’objet de plusieurs applications. Cependant, plusieurs verrous scientifiques et techniques, notamment leur comportement à long terme, limitent leur utilisation dans des conditions sévères de chargement.La thèse propose d’étudier le comportement en fluage des matériaux composites à renfort de lin unidirectionnel, dans la direction des fibres. En effet, même si le comportement viscoélastique et viscoplastique de ces composites est bien avéré, peu d’études ont été consacrés à ce type de chargement.Ainsi, des essais cyclés de fluage/recouvrance à durée et à contrainte variable ont permis de déterminer la dépendance en temps et contrainte du comportement.Ces essais ont également permis de montrer l’existence d’un seuil en contrainte pour l’apparition de déformation non-recouvrable assimilée à des déformations viscoplastiques.Les résultats ont permis ensuite de proposer une loi de comportement, composée d’un modèle viscoélastique non-linéaire de Schapery et d’un modèle viscoplastique de Zapas-Crissman. Les paramètres de la loi ont été identifiés à partir des essais de fluage/recouvrance. Ce modèle permet de rendre compte de manière satisfaisante de la déformation du composite lors d’essais de fluage/recouvrance et lors d’essais de traction cyclés. Par ailleurs, ce modèle a également permis de simuler des essais de traction monotone à différentes vitesses de chargement et de reproduire le comportement non-linéaire caractéristique de ces matériauxThe study presented in the manuscript is positioned in a large context of development of new materials, with a reduced environmental impact. From the possibilities currently under scrutiny (especially in Europe), flax fiber reinforced composites are the most promising. Thanks to their low density and high mechanical properties, as well as their low energy costs, fuel the idea of their usage in structural composites, by replacing glass fibers. These biocomposites are already implemented in numerous applications. However, several scientifical and technical unknowns, especially their long-term behavior, are hindering their use in domains of high load conditions.The thesis proposes to study the time dependent behavior of unidirectional reinforced composites, on the fiber direction. Even though it is largely accepted that the material behavior is viscoelastic and viscoplastic, few studies are dedicated to its analysis.Thus, multi cycled creep/recovery tests with variable creep stress and durations have allowed to determine the behavior’s dependence on stress and time. These tests have also allowed to determine the existence of a stress limit for plastic deformation appearance. They have been associated with the viscoplastic behavior.The results have, afterwards, allowed to propose a behavior law, composed of Schapery’s model for non-linear viscoelasticity and Zapas-Crissman’s model for viscoplasticity. The law parameters have been identified with the help of the creep/recovery tests. The model is capable of predicting the material response in deformation for creep recovery tests as well as load/unload tests. Simulations have also shown the model’s capability to reproduce traction tests with different loading speeds and to reproduce the nonlinear behavior specific to these composite materials
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Bashir, Tariq. "Conjugated Polymer-based Conductive Fibers for Smart Textile Applications." Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3649.
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Electrically conductive or electro-active fibers are the key components of smart and interactive textiles, which could be used in medical, sports, energy, and military applications in the near future. The functionalization of high-performance textile yarns/fibers with conjugated polymers can produce conductive fibers with better electro-mechanical properties, which is difficult with commonly used spinning techniques. In this thesis work, textile-based conductive yarns/fibers were prepared by coating viscose and polyester (PET) yarns with the conjugated polymer PEDOT. For coating purposes, an efficient technique called chemical vapor deposition (CVD) was used, which is a solventless technique and can produce PEDOT polymer layers with high conductivity values. The polymerization of EDOT monomer vapors and coating of oxidant (FeCl3 or FepTS) enriched viscose and PET yarns took place simultaneously. The PEDOT-coated viscose and polyester yarns showed relatively high conductivity values, which could be sufficient for many electronic applications. The polymerization process and the quality of PEDOT polymer strongly depends on different reaction conditions. In this research work, the impact of most of these reaction parameters on the electrical, mechanical, and thermal properties of PEDOT-coated conductive yarns was considered separately. Under specific reaction conditions, it was found that viscose fibers were successfully coated with PEDOT polymer and showed rather high electrical conductivity (≥ 15 S/cm). However, due to the acid hydrolysis of viscose fibers in FeCl3 solutions, the mechanical properties were drastically reduced. In order to improve the mechanical properties of conductive yarns, a relatively stable and chemical-resistant substrate (PET) was coated with PEDOT polymer. Comparative studies between PEDOT-coated viscose and PET conductive yarns showed that the electrical and mechanical properties were enhanced by changing the substrate material. Later on, PEDOT-coated conductive fibers were treated with silicone elastomer solution and due to the thin silicone layers, the hydrophobic properties, flexibility, and durability of coated yarns was improved. Furthermore, a novel electrical resistance-measuring setup was developed, which can be used not only for fibers but also for fabric structures. The electrical characterization of PEDOT-coated conductive yarns showed that it can be used effectively for sensitive fibers without damaging their surface morphology. Finally, the use of conductive yarns as stretch sensors was evaluated. For this purpose, small rectangular knitted patches of conductive yarns were prepared and then the change in electrical resistance values at different extension percentages (5–50%) was investigated. The constant variations in electrical resistance values at different extension and relaxation cycles for longer periods of time revealed that the conductive yarns produced have the potential to be used as stretch sensors for monitoring of vital signs in medical and sports applications.Thesis for the Degree of Doctor of Philosophy to be presented on March 08, 2013, 10.00 in KA-salen, Kemigården 4, Chalmers University of Technology, Gothenburg
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Franzoni, Nicola. "Modellazione numerica del comportamento viscoso fessurato di elementi in CCA." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amslaurea.unibo.it/992/.
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Questo studio mira ad affinare modelli numerici a fibre che siano in grado di valutare il comportamento differito viscoso fessurato di elementi in conglomerato cementizio armato.
Il modello numerico iterativo a fibre è stato calibrato e raffrontato con due campagne sperimentali che hanno studiato il fenomeno del creep in due travi in ca gettate in due fasi. E' in grado di valutare le deformzioni differite di sezioni e travi gettate e caricate in più fasi.
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Lowys, Marie-Pierre. "Comportement physico-chimique de suspensions de fibres cellulosiques : rôle des additifs." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10195.
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Ce travail porte sur la caracterisation physico-chimique de suspensions aqueuses de microfibrilles de cellulose (mfc) issues de la transformation des betteraves sucrieres, seules ou en presence d'additifs. La composition chimique des suspensions meres de mfc est determinee : elles sont composees de 86% de cellulose pure, les 14% restant etant des pectines, des hemicelluloses et des sels. Les proprietes ioniques des mfc sont ensuite etudiees par differentes techniques (conductimetrie, potentiel d'ecoulement, potentiel zeta). L'etat de dispersion des suspensions a ete caracterise par des mesures rheologiques en ecoulement et de sedimentation, qui ont mis en evidence l'importance du mode de dispersion et de la concentration en mfc sur la stabilite des suspensions. Nous avons montre l'existence d'une concentration critique c* au-dela de laquelle les suspensions ont un comportement de type gel. Des echantillons de mfc seches sous forme de film ne permettent pas de recuperer les proprietes rheologiques initiales lors de la remise en suspension. L'etude du comportement rheologique dynamique, montre que la remise en suspension est satisfaisante si un additif anionique est ajoute aux mfc avant sechage. L'etude de l'adsorption et de la desorption de ces additifs et des observations en microscopie de fluorescence, montrent que l'adsorption se fait de maniere uniforme sur toute la surface des mfc, mais que les interactions mises en jeu sont faibles, totalement reversibles. L'adsorption depend fortement de la charge et de la structure chimique de l'additif, mais pas de sa masse molaire. Ces resultats conduisent a l'hypothese de la formation d'un film interfacial d'additif anionique parfaitement hydrosoluble autour des mfc lors du sechage, permettant la remise en suspension et la recuperation des proprietes rheologiques de la suspension initiale. Certaines proprietes des suspensions de mfc ont ete comparees a celles de suspensions d'une cellulose bacterienne.
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Jenkins, Alexandra Louisa. "Metabolic effects of combining American ginseng (Panax quinquefolius L.) and viscous fibre in the treatment of type 2 diabetes." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/844256/.
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The aim of the thesis was to determine whether synergistic or additive metabolic benefits could be derived with the use of two plant-based components with independent physiological activities and whether the use of these two agents would improve diabetes control in the long term. Viscous fibres reduce postprandial glycaemia, insulinaemia and gastrointestinal hormones levels, their effectiveness being dependent on the viscosity of the fibre. Long term studies with viscous fibre have shown reductions in serum cholesterol, and improvements in metabolic control and blood pressure in type 2 diabetes. Konjac mannan fibre (KJM) is a high viscosity, viscous fibre. American ginseng (AG) increases insulin secretion and improves glycaemic control in type 2 diabetes. The suggested active ginseng components are the ginsenosides. As both AG and KJM have been shown to improve diabetes control through independent physiological mechanisms, this thesis explores the possible benefits of using them in combination. To test potential additive effects of KJM and AG, an acute experiment was performed in thirteen subjects with type 2 diabetes where AG and/or KJM were incorporated into a liquid meal replacement as a breakfast, followed 4 hours later by a standard lunch. Contrary to previous findings, neither AG or KJM when given individually, reduced postprandial glucose and insulin levels by the expected amounts; moreover the combination did not result in glucose levels significantly different from control. The study did demonstrate that KJM flattens the postprandial response of glucose-dependent insulinotropic peptide (p < 0.04) and glucagon like peptide-1 (p < 0.02). In addition KJM reduced the glucose area under the curve to a standard meal following the fibre enriched breakfast. Subsequent experiments showed that, despite high ginsenoside levels, the AG used was ineffective and the liquid replacement meal inhibited the gel formation of the KJM. In preparation for a long-term intervention study, acute experiments were performed to select a physiologically effective AG, and to determine the most effective and palatable method of KJM incorporation. Incorporation of KJM into bread, capsules and margarine reduced the incremental areas under the glucose curve by 3%, 12% and 34% compared with control, with only the margarine being significantly different (p < 0.001). Further experiments showed that incorporation of 1g of KJM into margarine and 4g of KJM into bread reduced the glucose AUC to a similar extent. KJM capsules has no acute effect on postprandial glycaemia, regardless of the timing of their administration relative to the meal. Three months of 6g of viscous fibre and 3g of AG administration to 30 subjects with type 2 diabetes resulted in significant percent-change difference from control in HbA1c (-4.1+/-1.4%, p < 0.01), total cholesterol (-5.7+/-1.9%, p < 0.00), LDL-cholesterol (- 8.2+/-3.1%, p < 0.002) and apoliporotein B (-9.0+/-2.3%, p < 0.0005). It was estimated the combination of viscous fibre and AG resulted in a 14% risk reduction in coronary heart disease. The studies in this thesis illustrate some of the difficulties of working with "natural" products but also their potentially effective use in the treatment of type 2 diabetes.
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Chen, Rong. "Synthesis and characterization of tall oil fatty acid based thermoset resin suitable for natural fiber reinforced composite." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-16591.
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Biobased thermoset resins were synthesized by functionalizing the tall oil fatty acid with hydrogen peroxide and then methacrylic anhydride. The obtained resins were characterized by FTIR to confirm the conversions. The cross-linking ability of the resins were checked by curing experiments and followed by DSC analysis regarding the extent of cross linking. TGA analysis was conducted to identify the thermal degradation patterns of cured resins. The obtained resins (blended with or without 33wt% styrene) were used as matrix and knitted viscose fibers were used as reinforcements to make bio-based composites. Ten layers of knitted viscose fibers were stacked crosswise (0/90⁰С) and hand lay-up impregnation was performed. The fiber ratio of all composites was around 63-66%. The composites were characterized by flexural testing, dynamic mechanical thermal analysis and charpy testing. This work demonstrates that manufacture of composites with both matrix and reinforcement fiber coming from renewable resources is feasible, and the resulted composites have satisfied mechanical performance.Program: MSc in Resource Recovery - Sustainable Engineering
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Despringre, Nicolas. "Analyse et modélisation des mécanismes d'endommagement et de déformation en fatigue multiaxiale de matériaux composites : polyamide renforcé par des fibres courtes." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0058/document.
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Le présent travail de thèse se consacre au développement d'un nouveau modèle micromécanique pour les composites en thermoplastique renforcé par des fibres de verre courtes. L'objectif est notamment la modélisation du comportement visco-endommageable en fatigue du PA66-GF30. Ce matériau, particulièrement utilisé dans l'industrie automobile, est sujet à une microstructure spécifique issue du procédé de moulage par injection. L'approche multi-échelles développée consiste en une méthode de Mori-Tanaka modifiée, appliquée à des renforts avec enrobage et prenant en compte l'évolution de l'endommagement à l'échelle microscopique. La description des mécanismes d'endommagement se base sur une investigation expérimentale poussée préalablement menée au sein de l'équipe. Des scénarios d'endommagement ont été proposés et incluent trois processus locaux différents : la décohésion de l'interface, la microfissuration de la matrice et les ruptures de fibres. Ceux-ci sont spécialement affectés par la microstructure. L'approche développée intègre ces cinétiques d'endommagement ainsi que la viscoélasticité non-linéaire de la matrice et la distribution d'orientation des inclusions due au procédé de fabrication. Chaque mécanisme d'endommagement est modélisé par une loi d'évolution basée sur les contraintes locales calculées à l'échelle microscopique. La loi constitutive finale, à l'échelle du volume élémentaire représentatif, est implémentée dans une bibliothèque scientifique en C++, SMART+, et est conçue pour être compatible avec une analyse de structures par éléments finis. L'identification du modèle est réalisée par rétro-ingénierie, en tirant profit de résultats expérimentaux multi-échelles, dont notamment des tests in-situ au MEB ainsi qu'une analyse qualitative et quantitative par μCTThe current work focuses on a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. Their description is based on the experimental investigations of damage mechanisms previously performed by the team. Damage chronologies have been proposed involving three different local degradation processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Their occurrence strongly depends on the microstructure. The developed model integrates these damage kinetics and accounts for the complex matrix viscoelasticity and the reinforcement orientation distributions induced by the process. Each damage mechanism is introduced through an evolution law involving local stress fields computed at the microscale. The developed constitutive law at the representative volume element scale is implemented into a C++ scientific library, SMART+, and is designed to work with Finite Element Methods. The model identification is performed via reverse engineering, taking advantage of the multiscale experimental results: in-situ SEM tests as well as quantitative and qualitative μCT investigations
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Esmaeili, Nima, and Shahrzad Javanshir. "Eco Friendly Composites Prepared from Lactic Acid Based Resin and Natural Fiber." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17524.
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Lactic acid based thermoset were synthesised by reacting lactic acid with glycerol andfunctionalizing lactic acid branches by methacrylic anhydride. Resins with different chainlength were prepared and their thermo mechanical properties were examined through DMAanalysis and their molecular structures were analyzed by NMR method and their viscositywere investigated through rheometry analysis and three monomers were selected as the bestchain length. Degree of reaction in different reaction times was evaluated by a modifiedtitration method and bulk preparation of resin was performed by optimal process condition.DSC analysis was conducted in order to evaluate curing behaviour of resin with benzoylperoxide as cross-linking initiator. TGA analysis was performed to check thermo stability ofthe resin. Bio composites by viscose unidirectional and bidirectional knitted fabrics and alsonon woven viscose fiber with different fiber loads were prepared by ordinary hand layupimpregnation followed by compress moulding and their mechanical and thermo mechanicalproperties were characterized by tensile, flexural, charpy and DMA analysis and optimumfiber loads were identified for each fiber type. Ageing properties of prepared composites wereexamined by placing samples in climate chamber to simulate long time ageing and ageingexperiment was followed by tensile and flexural test to evaluate mechanical properties afterageing simulation. Composite`s swelling properties for water and some other solvents wereinvestigated and also their chemical resistance were evaluated by immersing them in 1M HCland KOH. The resin was also compared with a commercial oil based thermoset by preparingglass fiber reinforced composites and also effect of adding styrene to the resin were evaluated.Results of this work demonstrated that the novel synthesised have very high mechanical andthermo mechanical properties surpassing commercial oil based poly esters but ageingbehaviour is not very good however adding styrene can improve ageing properties. Also theresin is compatible with cellulosic natural fibers and forms strong composites.Program: Masterutbildning i energi- och material
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Franco, Anaya Roberto. "Seismic Performance of Semi-Active Control Systems." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2008. http://hdl.handle.net/10092/1902.
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The main purpose of this research is to investigate the effectiveness and feasibility of semi-active control systems for structural protection during severe earthquake loading. However, the research reported herein also involves analytical studies on the effect of adding viscous damping to the second and fourth quadrants of the force-displacement curve, and laboratory and field testing of a fibre-optic gyroscope (FOG) for measuring rotations in civil engineering structures.
The concept of the 2-4 viscous damping is introduced to reduce the response of single-degree-of-freedom (SDOF) systems subjected to harmonic and earthquake excitations. This concept involves the addition of structural viscous damping to the second and fourth quadrants of the force-displacement graph. Time-history analyses and response spectra for various SDOF systems are carried out to assess the effect of adding 2-4 viscous damping. The analytical results indicate that the addition of 2-4 viscous damping is beneficial for reducing the harmonic and seismic response of a wide range of SDOF systems.
A newly developed semi-active resettable device is proposed to reduce the seismic response of a one-fifth scale structure. The device is investigated as part of a resettable tendon system installed in the structure. Nonlinear dynamic analyses are performed to determine the optimal configuration of the resettable tendon in the structure. Several shake table tests are performed on the structure equipped with two resettable devices. The dynamic characteristics of the structure and the devices are described. Various earthquake records at different levels of intensity are used during the seismic testing. Different control laws are employed to manipulate the hysteretic behaviour of the devices. The results of the shake table tests validate the effectiveness of the resettable devices to reduce the seismic response of structures.
Analytical studies are performed to determine the optimal utilization of the resettable devices in a twelve-storey reinforced concrete building. The seismic performance of the structure is discussed in relation to the number and distribution of the devices. Inelastic time-history analyses are carried out to assess the effectiveness of the devices to reduce the seismic response of the building. The impact of various tendon arrangements and different control laws on the earthquake response is investigated. Relevant issues for the implementation of the resettable devices in actual building systems are identified.
Finally, a new measurement concept based on the use of the fibre-optic gyroscope is proposed to measure rotation rates, rotations, displacements and inter-storey drifts of civil engineering structures. FOGs are compact, easy to install and, unlike conventional linear potentiometers, do not require a fixed reference frame to operate. Measurements recorded during the seismic testing of the one-fifth scale structure and displacement measurements at the Sky Tower in Auckland validate the suitability of the FOGs for applications in civil engineering.
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Mikhaylenko, Maxim A. "Development and Application of the Boundary Singularity Method to the Problems of Hydrodynamic and Viscous Interaction." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1442423671.
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Albouy, William. "De la contribution de la visco-élasto-plasticité au comportement en fatigue de composites à matrice thermoplastique et thermodurcissable." Phd thesis, INSA de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00942294.
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La présente étude vise à comprendre l'influence du comportement visco-élasto-plastique d'une matrice TP (PPS) et TD (Epoxy) sur le comportement en fatigue à haute température de composite tissés à fibres de carbone. Une analyse fractographique a permis de révéler le rôle déterminant des zones riches en matrice au niveau des plis à ±45° dans la chronologie d'endommagement et sur le comportement en fatigue de stratifiés à plis croisés et quasi-isotropes. Afin d'évaluer la contribution de la viscoélasticité et de la viscoplasticité de la matriceTP au comportement thermomécanique des stratifiés C/TP à T>Tg, un modèle viscoélastique de Norton généralisé ont été implémentés dans le code Eléments Finis Cast3m. Une technique de corrélation d'images numériques (CIN) a été mise œuvre pour tester la capacité du modèle à prédire la réponse du stratifié dans le cas de structures à forts gradients de contraintes.
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Jao, Jules Ericka. "Couplages entre propriétés thermiques, réactivité chimique et viscosité des matériaux composites thermodurcissables en relation avec les conditions de leur élaboration fondée sur l'hystérésis diélectrique." Phd thesis, Paris, ENSAM, 2001. http://tel.archives-ouvertes.fr/tel-00005595.
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Le procédé d'élaboration par chauffage des composites à matrice thermodurcissable est limité par les temps caractéristiques correspondant à la diffusion de la chaleur ; l'utilisation du chauffage par hystérésis diélectrique a montré la solution qu'il était possible d'apporter à cette limitation. Toutefois, la réduction de la durée de l'opération thermique est fonction de la mise forme du matériau résultant du fluage de la matière.La thèse comprend :
- premièrement les analyses électromagnétiques, chimique et thermique des conditions de mise en uvre du chauffage par hystérésis diélectrique pour des objets en matériau composite à fibres de verre unidirectionnelles,
- deuxièmement les caractérisations physiques et chimiques de la matrice (résine époxydique associée au durcisseur) en fonction de la température et en fonction des paramètres de son écoulement. Ces caractérisations comprennent la mesure de viscosité, la mesure de l'avancement de la réaction par DSC, les caractérisations diélectriques, la caractérisation des mélanges réactifs par GPC,
- troisièmement, l'application de ces analyses à la maîtrise du procédé.
La thèse conduit à une synthèse de l'ensemble des paramètres physiques et à leurs interdépendances pendant la mise en forme des matériaux.
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Wood, Brian Henry. "Experimental validation of an integrated FRP and visco-elastic hardening, damping, and wave-modulating system for blast resistance enhancement of RC columns." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Wood_09007dcc80538e4c.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 28, 2008) Includes bibliographical references (p. 112-115).
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Pegoraro, Paul. "Modélisation analytique de matériaux et de structures composites pour un comportement hygro-thermo-élastique." Paris 6, 1993. http://www.theses.fr/1993PA066737.
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Pignon, Frédéric. "Rhéologie des dispersions aqueuses thixotropes d'une argile de type hectorite." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0016.
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Le but de cette etude est l'identification et la comprehension des mecanismes gouvernant le comportement thixotrope dans les dispersions aqueuses d'une argile de type hectorite : la laponite. Cette argile modele, constituee de particules anisotropes de taille nanometrique, a permis de combiner les mesures rheometriques avec des mesures de diffusion de rayonnements, des visualisations du champ de deformation et des mesures de birefringence. Au repos, la structure des gels est constituee d'agregats microniques denses assembles en une masse fractale d'une dimension d. Pres de la transition sol-gel, d = 1, la texture est fibreuse. Aux fractions volumiques plus elevees, d = 1,8, la structure est une connexion de zones denses et de zones moins denses en particules. Des lois d'echelles theoriques et experimentales, ont permis de correler ces dimensions fractales a l'influence de la fraction volumique sur le seuil d'ecoulement. La transition sol-gel et la stabilite de la phase gel ont ete etudiees en fonction du temps de gelification et des parametres physico-chimiques. L'existence d'instabilites d'ecoulements, telle que la localisation du cisaillement, ont ete montrees, sur ces dispersions dont la courbe d'ecoulement est a minimum de contrainte. Les differents regimes d'ecoulements ont ete identifies et ont permis d'etablir des procedures fiables pour la caracterisation du comportement thixotrope. Sous ecoulement de cisaillement, la chute de viscosite provient d'orientations et de desagregation a l'echelle de longueur de l'ordre du micron. Lors de la restructuration, les deux echelles de temps mises en evidence, correspondent respectivement a une relaxation rapide des orientations et a un processus lent d'agregation. La nature du comportement thixotrope est alors identifiee comme etant principalement un processus d'agregation reversible, pour lequel les grandes echelles de longueur, de l'ordre du micron, associees a un arrangement fractal jouent un role determinant.
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Panda, Satyananda [Verfasser]. "The dynamics of viscous fibers / Satyananda Panda." 2006. http://d-nb.info/979183138/34.
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CHEN, GUO-HUA, and 陳國華. "A study on the spinning of flame retardant rayon fibers by the viscose process." Thesis, 1986. http://ndltd.ncl.edu.tw/handle/62980970304427610717.
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ZHU, SHI-LIN, and 朱時霖. "The study on the spinning of rayon fibers from bagasse cellulose by the viscose method." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/63931367084704732552.
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Breitman, Pearl Laurie. "The effects of viscous dietary fibers on the parameters of appetite and food intake regulation." 2009. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=968403&T=F.
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Kwong, Melissa Gaa-Yee. "The Glycemic Response Elicited by Oat β-glucan Solutions and Hard Gel Varying in Physiochemical Properties and Food Form." Thesis, 2012. http://hdl.handle.net/1807/35153.
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The ability of the soluble fibre (1->3)(1->4)-β-D-glucan to attenuate postprandial glycemic responses depends on its viscosity which, in turn, depends on molecular weight (MW) and dose. However, the effect of altering viscosity by changing solution volume is unknown. Furthermore, β-glucan solutions may form hard gels when left to age, but the effect of these gels on glycemic responses is unknown. Therefore, the effects of varying the MW and volume of β-glucan solutions and hard gels, on glycemic responses were determined. The results showed that glycemic responses were reduced by increasing viscosity by increasing MW but not by reducing solution volume. Although β-glucan gels reduced the rate of glucose diffusion in vitro, they had no effect on glycemic responses in vivo. Thus, changing solution viscosity through changes in volume does not alter the effect of β-glucan on glycemic response, and β-glucan gels are ineffective at attenuating in vivo glycemic responses.