Dissertations / Theses: 'Nanofibrous materials'

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Angelikopoulos, Panagiotis. "Rational design of nanofibrous materials." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2346.

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Making Carbon nanotubes a functional material for widespread use is a very cumbersome and challenging task. Not only do CNT materials require the tubes to be well dispersed and individualized rather than in bundles but resulting material has much poorer properties than expected due to insufficient load transfer between crossing CNT. This work tries to provide insight and solutions onto both of these problems, by employing computer simulations to reveal the dual nature of surfactant mediated forces on CNT. A generic coarse grain model has been used along with a dissipative particle dynamics thermostat and implicit solvent treatment. Results illustrate that depending on the bulk concentration of surfactants and their geometry, one can control the surfatantmediated forces on tubes being able to trigger both tube gluing or dispersion. Furthermore, an adsorption study elucidating the differences between surfactant adsorption on individual tubes and their bundles has been done. Surfactants follow a superlinear synergetic adsorption isothermon individual tubes,whereas adsorb via a Langmuir mechanism on their bundles. This work provides a solid framework of knowledge and insight regarding the nature of CNT and surfactants interaction and adsorption, providing rational arguments for the design of optimum CNT materials.

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Palazzetti, Roberto <1984&gt. "Electrospun nanofibrous interleaves in composite laminate materials." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5245/.

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The present work aims for investigate the influence of electrospun Nylon 6,6 nanofibrous mat on the behavior of composite laminates. The main idea is that nanofibrous interleaved into particular ply-to-ply interfaces of a laminate can lead to significant improvements of mechanical properties and delamination/damage resistance. Experimental campaigns were performed to investigate how nanofibers affect both the static and dynamic behavior of the laminate in which they are interleaved. Fracture mechanics tests were initially performed on virgin and 8 different configuration of nanomodified specimens. The purposes of this first step of the work are to understand which geometrical parameters of the nanointerleave influence the behavior of the laminate and, to find the optimal architecture of the nanofibrous mat in order to obtain the best reinforcement. In particular, 3 morphological parameters are investigated: nanofibers diameter, nanofibers orientation and thickness of the reinforce. Two different values for each parameter have been used, and it leads to 8 different configurations of nanoreinforce. Acoustic Emission technique is also used to monitor the tests. Once the optimum configuration has been found, attention is focused on the mechanism of reinforce played by the nanofibers during static and dynamic tests. Low velocity impacts and free decay tests are performed to attest the effect of nanointerlayers and the reinforce mechanism during the dynamic loads. Bump tests are performed before and after the impact on virgin and two different nanomodified laminates configurations. The authors focused their attention on: vibrational behavior, low velocity impact response and post-impact vibration behavior of the nano-interleaved laminates with respect to the response of non-nanomodified ones. Experiments attest that nanofibers significantly strength the delamination resistance of the laminates and increase some mechanical properties. It is demonstrated that the nanofibers are capable to continue to carry on the loads even when the matrix around them is broken.

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Wang, Chong, and 王翀. "Electrospun multicomponent and multifunctional nanofibrous tissue engineering scaffolds : fabrication, characteristics and biological performance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/206645.

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Electrospinning has attracted great attention in the fields of tissue engineering and controlled release of drugs/biomolecules. The aim of this project was to investigate electrospinning of nanofibers with core-shell structures using emulsion electrospinning, the formation of monolithic and core-shell structured nanofibrous drug/biomolecule delivery vehicles using polymers such as poly(D,L-lactic acid) (PDLLA) and poly(lactic-co-glycolic acid) (PLGA), and the formation of multicomponent bone tissue engineering scaffolds with angiogenic property, osteoinductivity and osteoconductivity. The foundation of this project was laid by investigating monocomponent scaffolds. First, effects of properties of polymer solutions and water-in-oil (w/o) emulsions and electrospinning parameters on the morphology, diameter and structure of fibers were systematically investigated. Second, drugs (vancomycin and rifamycin) and a model protein (bovine serum albumin) were incorporated in monolithic or core-shell nanofibers via blend electrospinning or emulsion electrospinning to form single or dual delivery systems, providing fundamental understandings. Growth factors such as recombinant human bone morphogenetic protein-2 (rhBMP-2) and basic-fibroblast growth factor (b-FGF) were then incorporated in PLGA or PDLLA nanofibrous delivery vehicles. The in vitro release behaviour of drugs and biomolecules was studied. Third, calcium phosphate (Ca-P) nanoparticles were synthesized and used for fabricating Ca-P/PLGA and Ca-P/PDLLA nanocomposite scaffolds. Homogeneous distribution of Ca-P in fibrous scaffolds could be achieved. With the assistance of emulsion electrospinning and nanocomposite electrospinning, bicomponent scaffolds containing rhBMP-2 and Ca-P nanoparticles were fabricated using dual-source dual-power electrospinning. The fibrous component ratio could be varied by using multiple syringes for electrospinning fibers. The structure and properties, including in vitro release behaviour, of mono- and bicomponent scaffolds were studied in detail. Tricomponent scaffolds incorporated with recombinant human vein endothelial growth factor (rhVEGF), rhBMP-2 and Ca-P nanoparticles were subsequently fabricated using multi-source dual-power electrospinning. To achieve a sequential release of firstly rhVEGF and then rhBMP-2, PLGA/polyethylene glycol (PEG) blends and PLGA were used for incorporating rhVEGF and rhBMP-2, respectively. For tricomponent scaffolds with different component ratios, different release amounts but similar release profiles could be achieved for the growth factors. In vitro biological investigations were conducted for mono-, bi- and tricomponent scaffolds. Pre-osteoblast cells (MC3T3-E1) were found to attach, spread, proliferate and express alkaline phosphatase (ALP) activity on rhBMP-2 and Ca-P nanoparticle incorporated bicomponent scaffolds. Calcium deposition was also observed in cells cultured with bicomponent scaffolds. Human umbilical vein endothelial cells (HUVECs) were found to attach, spread, proliferate on tricomponent scaffolds and rhVEGF released from mono-, bi- and tricomponent scaffolds could facilitate cell proliferation and migration, indicating released rhVEGF could promote angiogenesis. C3H10T1/2 cell line and human bone marrow derived mesenchymal stem cells (hBMSCs) were found to attach, spread and proliferate on bi- and tricomponent scaffolds. As compared with cells seeded on monocomponent scaffolds, C3H10T1/2 cells and hBMSCs on bi- and tricomponent scaffolds expressed higher ALP activity. Enhanced mineralization was observed for C3H10T1/2 cells and hBMSCs seeded bicomponent scaffolds comprising rhBMP-2/PLGA and Ca-P/PLGA fibers and also tricomponent scaffolds. hBMSCs seeded on rhBMP-2/PLGA and Ca-P/PLGA monocomponent scaffolds expressed abundant F-actin and vinculin, while bicomponent and tricomponent scaffolds induced much more F-actin and vinculin expression. published_or_final_version Mechanical Engineering Doctoral Doctor of Philosophy

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Liang, Meng. "Spatial organization of electric charges and discharge kinetics of nanofibers elaborated by electrospinning : application to the elaboration of 3D structured nanofibrous materials." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE002.

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L’electrospinning est un procédé permettant la production de matériaux nanofibreux sous l'action d'un champ électrostatique intense. Au cours du procédé, une solution de polymère en régime semi-dilué enchevêtré est introduite dans une aiguille métallique soumise à un potentiel électrique élevé. Lorsque le champ électrique entre l'aiguille et une contre-électrode métallique reliée à la terre électrique, appelée collecteur, est suffisamment fort (de l’ordre de 1 kV/cm), un jet de la solution est violemment éjecté vers le collecteur. Pendant le vol entre l'aiguille et le collecteur, le jet est soumis à des instabilités électro-hydrodynamiques qui provoquent des mouvements de fouet favorisant l'évaporation du solvant et la réduction du diamètre. Après un temps de vol de quelques ms, une nanofibre polymère solide est déposée sur le collecteur sous la forme d’un scaffold non-tissé. Lorsque la nanofibre chargée électriquement est mise en contact avec le collecteur, elle se décharge progressivement. La cinétique de la décharge électrique mais aussi la façon dont les charges sont réparties à la surface du matériau pendant le procédé déterminent l'organisation et la structuration 3D finale du scaffold.Les travaux de cette thèse ont consisté à mesurer les charges électriques portées par la nanofibre lors de son dépôt mais aussi à étudier comment ces charges se dissipent dans la membrane et dans le temps, une fois la nanofibre déposée. Cette étude a ensuite été appliquée au développement de scaffolds nanofibreux de structure contrôlée en 3D Electrospinning is a process allowing the production of nanofibrous materials under the action of an intense electrostatic field. During the process, a polymer solution in a semi-diluted entangled regime is fed to a metal needle submitted to a high electrical potential. When the electric field between the needle and a metal counter electrode connected to the electrical ground, called a collector, is strong enough (i.e. about 1 kV/cm), a jet of the solution is violently ejected towards the collector. During the flight between the needle and the collector, the jet is subjected to electro-hydro-dynamic instabilities resulting in whipping movements that promote solvent evaporation and diameter reduction. After a flight time of a few ms, a solid polymer nanofiber in the form of a non-woven membrane is deposited on the collector. When the electrically charged nanofibre is brought into contact with the collector, it gradually discharges. The kinetics of electrical discharge but also the way in which the charges are distributed on the surface of the material during the process determine the organization and the final 3D structuring of the membrane.The work of this thesis consisted in measuring the electrical charges carried by the nanofibre during its deposition but also in studying how these charges dissipate in the membrane and over time once the nanofibre has been deposited. This study was then applied to develop nanofiber membranes with a controlled 3D structure

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Tchang, Cervin Nicholas. "Porous Materials from Cellulose Nanofibrils." Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155065.

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In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic tri-chloro-silanes on ultra-porous cellulose nanofibril (CNF) aerogels. To achieve this, a highly porous (>99%) robust CNF aerogel with high structural flexibility is first formed by freeze-drying an aqueous suspension of the CNFs. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the CNF suspension before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can subsequently be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle. The second part is about aerogels with different pore structures and manufactured with freeze-drying and supercritical carbon dioxide for the preparation of super slippery surfaces. Tunable super slippery liquid-infused porous surfaces (SLIPS) were fabricated through fluorination of CNFsand subsequent infusion with perfluorinated liquid lubricants. CNF-based self-standing membranes repelled water and hexadecane with roll-off angles of only a few degrees. The lifetime of the slippery surface was controlled by the rate of evaporation of the lubricant, where the low roll-off angle could be regained with additional infusion. Moreover, adjusting the porosity of the membranes allowed the amount of infused lubricant to be tuned and thereby the lifetime. The CNF-based process permitted the expansion of the concept to coatings on glass, steel, paper and silicon. The lubricant-infused films and coatings are optically transparent and also feature self-cleaning and self-repairing abilities. The third part describes how porous structures from CNFs can be prepared in a new way by using a Pickering foam technique to create CNF-stabilized foams. This technique is promising for up-scaling to enable these porous nanostructured cellulose materials to be produced on a large scale. With this technique, a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified CNFs. Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped CNF nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 %, and measurements with an autoporosimeter (APVD) reveal that most pores have a radius in the range of 300 to 500 μm. In the fourth part, the aim was to clarify the mechanisms behind the stabilizing action of CNFs in wet-stable cellulose foams. Factors that have been investigated are the importance of the surface energy of the stabilizing CNF particles, their aspect ratio and charge density, and the concentration of CNF particles at the air-water interface. In order to investigate these parameters, the viscoelastic properties of the interface have been evaluated using the pendant drop method. The properties of the interface have also been compared by foam stability tests to clarify how the interface properties can be related to the foam stability over time. The most important results and conclusions are that CNFs can be used as stabilizing particles for aqueous foams already at a concentration as low as 5 g/L. The reasons for this are the high aspect ratio which is important for gel formation and the viscoelastic modulus of the air-water interface. Foams stabilized with CNFs are therefore much more stable than foams stabilized by cellulose nanocrystals (CNC). The charge density of the CNFs affects the level of liberation of the CNFs within large CNF aggregates and hence the number of contact points at the interface, and also the gel formation and viscoelastic modulus. The charges also lead to a disjoining pressure related to the long-range repulsive electrostatic interaction between the stabilized bubbles, and this contributes to foam stability. In the fifth part, the aim was to develop the drying procedure in order to producea dry porous CNF material using the wet foam as a precursor and to evaluate the dry foam properties. The wet foam was dried in an oven while placed on a liquid-filled porous ceramic frit to preserve and enhance the porous structure in the dried material and prevent the formation of larger cavities and disruptions. The cell structure has been studied by SEM microscopy and APVD (automatic pore volume distribution). The mechanical properties have been studied by a tensile tester (Instron 5566) and the liquid absorption ability with the aid of the APVD-equipment. By changing the charge density of the CNFs it is possible to prepare dry foams with different densities and the lowest density was found to be 6 kg m-3with a porosity of 99.6 %. The Young ́s modulus in compression was 50 MPa and the energy absorption was 2340kJ m-3 for foams with a density of 200 kg m-3. The liquid absorption of the foam with a density of 13 kg m-3 is 34 times its own weight. By chemically cross-linking the foam,it wasalso possible to empty the liquid-filled foams by compression and then to reabsorb the liquid to the same degree with maintained foam integrity. This new processing method also shows great promise for preparing low-density cellulose foams continuously and could be very suitable for industrial up-scaling. QC 20141103

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Butchosa, Robles Núria. "Tailoring Cellulose Nanofibrils for Advanced Materials." Doctoral thesis, KTH, Biokompositer, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155056.

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Cellulose nanofibrils (CNFs) are nanoscale fibers of high aspect ratio that can be isolated from a wide variety of cellulosic sources, including wood and bacterial cellulose. With high strength despite of their low density, CNFs are a promising renewable building block for the preparation of nanostructured materials and composites. To fabricate CNF-based materials with improved inherent rheological and mechanical properties and additional new functionalities, it is essential to tailor the surface properties of individual CNFs. The surface structures control the interactions between CNFs and ultimately dictate the structure and macroscale properties of the bulk material. In this thesis we have demonstrated different approaches, ranging from non-covalent adsorption and covalent chemical modification to modification of cellulose biosynthesis, to tailor the structure and surface functionalities of CNFs for the fabrication of advanced materials. These materials possess enhanced properties such as water-redispersibility, water absorbency, dye adsorption capacity, antibacterial activity, and mechanical properties. In Paper I, CNFs were modified via the irreversible adsorption of carboxymethyl cellulose (CMC). The adsorption of small amounts of CMC onto the surface of CNFs prevented agglomeration and co-crystallization of the nanofibrils upon drying, and allowed the recovery of rheological and mechanical properties after redispersion of dried CNF samples. In Paper II, CNFs bearing permanent cationic charges were prepared through quaternization of wood pulp fibers followed by mechanical disintegration. The activation of the hydroxyl groups on pulp fibers by alkaline treatment was optimized prior to quaternization. This optimization resulted in individual CNFs with uniform width and tunable cationic charge densities. These cationic CNFs demonstrated ultrahigh water absorbency and high adsorption capacity for anionic dyes. In Paper III, via a similar approach as in Paper II, CNFs bearing polyethylene glycol (PEG) were prepared by covalently grafting PEG to carboxylated pulp fibers prior to mechanical disintegration. CNFs with a high surface chain density of PEG and a uniform width were oriented to produce macroscopic ribbons simply by mechanical stretching of the CNF hydrogel network before drying. The uniform grafted thin monolayer of PEG on the surface of individual CNFs prevented the agglomeration of CNFs and facilitated their alignment upon mechanical stretching, thus resulted in ribbons with ultrahigh tensile strength and modulus. These optically transparent ribbons also demonstrated interesting biaxial light scattering behavior. In Paper IV, bacterial cellulose (BC) was modified by the addition of chitin nanocrystals (ChNCs) into the growing culture medium of the bacteria Acetobacter aceti which secretes cellulose in the form of entangled nanofibers. This led to the in situ incorporation of ChNCs into the BC nanofibers network and resulted in BC/ChNC nanocomposites exhibiting bactericidal activity. Further, blending of BC nanofibers with ChNCs produced nanocomposite films with relatively lower tensile strength and modulus compared to the in situ cultivated ones. The bactericidal activity increased significantly with increasing amount of ChNCs for nanocomposites prepared by direct mixing of BC nanofibers and ChNCs. In Paper V, CNFs were isolated from suspension-cultured wild-type (WT) and cellulose-binding module (CBM) transformed tobacco BY-2 (Nicotiana tabacum L. cv bright yellow) cells. Results from strong sulfuric acid hydrolysis indicated that CNFs from transgenic cells overexpressing CBM consisted of longer cellulose nanocrystals compared to CNFs from WT cells. Nanopapers prepared from CNFs of transgenic cells demonstrated significantly enhanced toughness compared to CNFs of WT cells. QC 20141103 CARBOMAT

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Zadorosny, Lincon [UNESP]. "Produção e caracterização de micro e nanofibras de Poli(fluoreto de vinilideno) - PVDF obtidos pela técnica de fiação por sopro em solução." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/91972.

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Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-04Bitstream added on 2014-06-13T19:12:23Z : No. of bitstreams: 1 zadorosny_l_me_ilha.pdf: 3393568 bytes, checksum: b39b59b685225b543349760ff3d66599 (MD5) Nanofibras poliméricas de poli(fluoreto de vinilideno) – PVDF – foram produzidas pela técnica de fiação por sopro em solução (FSS) a partir de soluções de PVDF/N,N, Dimetilformamida – DMF. Foram estudadas as influências da variação da concentração polimérica (15, 20, 25 e 30%, m/v), distância de trabalho (15, 18, 21 e 24 cm), taxa de alimentação (19, 38 e 76 μL/min), e pressão do gás (100, 140 e 180 kPa), sobre a morfologia e diâmetro das nanoestruturas. O diâmetro médio das nanofibras obtidas variou entre 91 e 245 nm. Imagens de MEV apontam que, dentre os parâmetros estudados, o que promoveu maior alteração morfológica das nanofibras foi a concentração polimérica, fator diretamente relacionado à viscosidade da solução. A variação dos demais parâmetros promoveu menores alterações tanto estruturais quanto morfológicas nos filmes nanofibrosos. Análises termogravimétricas (TGA) revelaram que os filmes são termicamente estáveis até uma temperatura de 420 °C. Difratometria de raios X (DRX) indicaram a presença das fases cristalinas α e β, sendo a fase β mais evidenciada para as nanofibras e PVDF casting. O filme obtido por FSS apresentou maior ângulo de contato, demostrando ser mais hidrofóbico. Ensaios de tensão deformação mostraram que os filmes nanofibrosos apresentaram uma deformação até a ruptura de 72%, cerca de 1,7 e 3,1 vezes maior que os obtidos por casting e prensagem a quente, respectivamente. Verificou-se também um decréscimo no módulo de elasticidade e do limite de resistência à tração das nanofibras, comparativamente aos outros filmes Poly(vinylidene fluoride) – PVDF Nanofibers were produced by solution blow spinning technique (SBS) from solutions PVDF/N,N, Dimethylformamide – DMF. It was investigated the influence of the polymeric concentration (15, 20, 25 e 30% w/v), work distance (15, 18, 21 and 24 cm), feed rate (19, 38 e 76 μL/min), and gas pressure (100, 140 e 180 kPa), on the morphology of the nanostructure and diameter of the nanofibers. The average diameter of the obtained nanostructure was on the range 91 - 245 nm. SEM images show that, among the studied parameters, the concentration of the solution promoted the grater changes in the morphology of the polymer nanofibers. Such factor is directly related to the viscosity of the solution. Variation of the other parameters promoted both structural and morphological changes in the nanofiber films. Termograviometric analyses showed that the films are thermally stable up to 420°C. X-ray diffraction (XRD) indicated the presence of the crystalline phases α and β. However, the β phase is more evident in the nanofibers and in the PVDF casting. The films obtained by SBS showed higher contact angle, which means that they are more hydrophobic. Stress-strain tests showed that nanofiber films had a break deformation of 72%, approximately 1.7 and 3.1 times higher than those obtained by casting and hot pressing, respectively. There was also a decrease in the elastic modulus and in the tensile strength of the PVDF nanofibers when compared with the other films

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Zadorosny, Lincon. "Produção e caracterização de micro e nanofibras de Poli(fluoreto de vinilideno) - PVDF obtidos pela técnica de fiação por sopro em solução /." Ilha Solteira, 2013. http://hdl.handle.net/11449/91972.

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Orientador: Luiz Francisco Malmonge Banca: Walter Katsumi Sakamoto Banca: Antonio Riul Júnior Resumo: Nanofibras poliméricas de poli(fluoreto de vinilideno) - PVDF - foram produzidas pela técnica de fiação por sopro em solução (FSS) a partir de soluções de PVDF/N,N, Dimetilformamida - DMF. Foram estudadas as influências da variação da concentração polimérica (15, 20, 25 e 30%, m/v), distância de trabalho (15, 18, 21 e 24 cm), taxa de alimentação (19, 38 e 76 μL/min), e pressão do gás (100, 140 e 180 kPa), sobre a morfologia e diâmetro das nanoestruturas. O diâmetro médio das nanofibras obtidas variou entre 91 e 245 nm. Imagens de MEV apontam que, dentre os parâmetros estudados, o que promoveu maior alteração morfológica das nanofibras foi a concentração polimérica, fator diretamente relacionado à viscosidade da solução. A variação dos demais parâmetros promoveu menores alterações tanto estruturais quanto morfológicas nos filmes nanofibrosos. Análises termogravimétricas (TGA) revelaram que os filmes são termicamente estáveis até uma temperatura de 420 °C. Difratometria de raios X (DRX) indicaram a presença das fases cristalinas α e β, sendo a fase β mais evidenciada para as nanofibras e PVDF casting. O filme obtido por FSS apresentou maior ângulo de contato, demostrando ser mais hidrofóbico. Ensaios de tensão deformação mostraram que os filmes nanofibrosos apresentaram uma deformação até a ruptura de 72%, cerca de 1,7 e 3,1 vezes maior que os obtidos por casting e prensagem a quente, respectivamente. Verificou-se também um decréscimo no módulo de elasticidade e do limite de resistência à tração das nanofibras, comparativamente aos outros filmes Abstract: Poly(vinylidene fluoride) - PVDF Nanofibers were produced by solution blow spinning technique (SBS) from solutions PVDF/N,N, Dimethylformamide - DMF. It was investigated the influence of the polymeric concentration (15, 20, 25 e 30% w/v), work distance (15, 18, 21 and 24 cm), feed rate (19, 38 e 76 μL/min), and gas pressure (100, 140 e 180 kPa), on the morphology of the nanostructure and diameter of the nanofibers. The average diameter of the obtained nanostructure was on the range 91 - 245 nm. SEM images show that, among the studied parameters, the concentration of the solution promoted the grater changes in the morphology of the polymer nanofibers. Such factor is directly related to the viscosity of the solution. Variation of the other parameters promoted both structural and morphological changes in the nanofiber films. Termograviometric analyses showed that the films are thermally stable up to 420°C. X-ray diffraction (XRD) indicated the presence of the crystalline phases α and β. However, the β phase is more evident in the nanofibers and in the PVDF casting. The films obtained by SBS showed higher contact angle, which means that they are more hydrophobic. Stress-strain tests showed that nanofiber films had a break deformation of 72%, approximately 1.7 and 3.1 times higher than those obtained by casting and hot pressing, respectively. There was also a decrease in the elastic modulus and in the tensile strength of the PVDF nanofibers when compared with the other films Mestre

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Neves, Roberta Motta. "Produção e caracterização de nanocompósitos expandidos de poliestireno, reforçados com nanofibras e nanowhiskers de celulose obtidas a partir de fibra de curauá." reponame:Repositório Institucional da UCS, 2017. https://repositorio.ucs.br/handle/11338/3474.

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A busca por materiais de origem natural, com menos impacto ambiental e com as mesmas propriedades de materis sintéticos está cada vez mais em foco nas pesquisas na área de engenharia. Um modo de fazer isto é o desenvolvimento de nancompósitos reforçados por materiais oriundos de fibras naturais visto que estas possuem em sua estrutura celulose e a celulose é o composto presente em maior quantidade no planeta. Dentro dos nanocompósitos existe a classe dos nanocompósitos expandidos que combinam boas propriedades mecânicas com densidade reduzida e capacidade superior de isolamento térmico e acústico, quando comparados aos nanocompósitos convencionais não expandidos. Nanocompósitos expandidos são materiais que possuem pelo menos três fases: uma contínua (matriz polimérica), a fase dispersa (elementos de reforço) e a presença de espaços vazios no interior da estrutura, denominadas células. O poliestireno (PS) é um polímero muito utilizado na produção de materiais expandidos. Nesse sentido, o presente estudo tem por objetivo, primeiramente a obtenção das nanofibras (NFC) e nanowhiskers (NWC) de celulose ambas extraídas de fibras de curauá (FC). As NFC foram obtidas pelo processo de desfibrilação e os NWC a partir do método de oxidação. Estas foram caracterizadas quanto sua morfologia por microscopia eletrônica de transmissão (MET), microscopia eletrônica de varredura com emissão de campo (MEV-FEG), grau de polimerização (GP), quanto sua estrutura cristalina (DRX), quanto suas propriedades térmicas (TG) e quanto a estrutura química (FTIR). Após, ocorreu o desenvolvimento de nanocompósitos de poliestireno (PS) reforçado com NFC e NWC, nas seguintes concentrações de reforço: 0,25%, 0,50% e 1,00% (m/m). Avaliou-se a influência da incorporação dos reforços na matriz por DMA onde observou-se um aumento no módulo de armazenamento e de perda para todos os nanocompósitos, em relação ao PS sem reforço. Após os nanocompósitos foram expandidos utilizando dióxido de carbono em estado supercrítico como agente expansor e os nanocompósitos expandidos foram avaliados por propriedades mecânicas (resistência à compressão), na morfologia final do nanocompósito expandido por MEV-FEG e por distribuição de tamanho de células. Nos nanocompósitos expandidos, a incorporação das NFC promoveu um aumento na resistência a compressão e uma diminuição no tamanho de células, quando comparado as amostras reforçadas com NWC e PS puro. De modo geral, a incorporação dos NWC nos nanocompósitos antes da expansão proporcionaram melhores resultados quando comprados ao reforçados com NFC. Por poutro lado a incorporação de NFC nos nanocompósitos expandidos proporcionaram melhores resultados quando comparados aos reforçados com NWC. Submitted by cmquadros@ucs.br (cmquadros@ucs.br) on 2018-02-20T11:45:18Z No. of bitstreams: 1 Dissertacao Roberta Motta Neves.pdf: 2419021 bytes, checksum: 98834ba297d6c3752a7400aba41b8968 (MD5) Made available in DSpace on 2018-02-20T11:45:18Z (GMT). No. of bitstreams: 1 Dissertacao Roberta Motta Neves.pdf: 2419021 bytes, checksum: 98834ba297d6c3752a7400aba41b8968 (MD5) Previous issue date: 2018-02-20 The search for materials of natural origin, with less environmental impact and with the same properties of synthetic materials is increasingly focused on research in the field of engineering. One way to doing this is a development of nanocomposites reinforced with materials obtained from natural fibers, because that have on your biologic structure cellulose and the cellulose is present in greater quantity in the planet. Within the nanocomposites there is a class of expanded nanocomposites that combine good mechanical properties with reduced density and superior capacity of thermal and acoustic insulation when compared to conventional non-expanded nanocomposites. Expanded nanocomposites are materials that have at least three phases: a continuous (polymer matrix), the dispersed phase (reinforcing elements) and the presence of voids inside the structure, called cells. Polystyrene (PS) is a polymer widely used in the production of expanded materials. In this sense, the aim of the present study were firstly to obtain nanofibers (NFC) and nanowhiskers (NWC) of cellulose both extracted from curauá fibers (CF). The NFCs were obtained by the defibrillation process and the NWC from the oxidation method. These were characterized by their transmission electron microscopy (TEM), scanning electron microscopy with field emission (SEM), degree of polymerization (GP), their crystalline structure (XRD), and their thermal properties (TG) and the chemical structure by Fourier-transform infrared spectroscopy (FTIR). After that, the next step was the development of PS/NFC and PS/NWC nanocomposites in the following reinforcement concentrations: 0.25%, 0.50% and 1.00% (w/w). The influence of the incorporation of the reinforcements in the matrix by DMA was evaluated, where an increase in the storage and loss modulus was observed for all the nanocomposites, in relation to the PS without reinforcement. After the nanocomposites were expanded using carbon dioxide in the supercritical state as an expander and the expanded nanocomposites were evaluated by mechanical properties (compressive strength), in the final morphology of the expanded nanocomposite by SEM and by cell size distribution. In the expanded nanocomposites, the incorporation of the NFC promoted an increase in the compressive strength and a decrease in the cell size when compared to the samples reinforced with NWC and pure PS. In general, the incorporation of NWC in nanocomposites prior to expansion provided better results when purchased from NFC-reinforced ones. On the other hand, the incorporation of NFC in the expanded nanocomposites provided better results when compared to those reinforced with NWC.

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Li, Shuangwu. "Surface properties of electrospun polymer nanofibres." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/548.

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Fibrous materials are used in a variety of applications due to their relatively high surface area to volume ratio as well as anisotropic behaviour. Electrospinning is a popular fabrication technique which produces polymer nanofibres with a potentially high molecular orientation. The surface of polymer fibres plays a significant role in many applications thus measurement of their surface properties is essential but challenging due to their relatively small size. In this thesis, ultrafine nanofibres have been produced by electrospinning with their nanofibre morphology controlled by varying different processing parameters. Atomic force microscopy (AFM) adhesion contact mechanics and individual nanofibre wetting measurements have been conducted to explore surface properties of the produced electrospun polymer fibres. Results using traditional Owens-Wendt plots applied to our nanomaterials show electrospun nanofibres have a higher dispersive surface free energy compared to bulk polymer film but a lower polar contribution, giving a total surface free energy in excess of bulk equivalents. A novel proposed model indicates that this nanofibre dispersive surface free energy is intimately linked to density of the polymer and ultimately the molecular spacing or orientation for the polymer chains. Comparisons are made with bulk polymer films to show that a high degree of molecular orientation is present at least at the surface of the polymer nanofibre. Structure investigations on electrospun fibres of polyvinyl alcohol using FTIR and XPS surface techniques explore how an increase in hydrogen bonds formed within nanofibres rather than on the fibre surface enhance this dispersive contribution but lowers the polar contribution. The wetting behaviour of electrospun fibre is extended to assemblies at length scales above individual fibres to highlight how superhydrophobic surfaces can be produced from nanofibre networks with defined spacings and geometries. This superhydrophobicity was adequately described by a Cassie-Baxter model modified to account for the fibrous geometry.

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Calíope, Priscila Braga. "Caracterização de nanofibras através de técnicas de processamento de imagens." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-28102009-172405/.

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O electrospinning (deposição eletrostática) representa um método simples e conveniente para preparar bras poliméricas e bras cerâmicas com interiores sólidos ou ocos, excepcionalmente longos em comprimento, uniformes no diâmetro, variando no intervalo de dezenas de nanômetros a vários micrômetros, com diversicadas composições. Apesar da potencialidade e versatilidade da Microscopia Eletrônica de Varredura existe um grande problema de caracterizar nanobras, já que este processo não é feito automaticamente. Este trabalho apresenta uma nova metodologia para extração automática de medidas em imagens SEM, como uma alternativa eciente em relação aos softwares semi-automáticos propostos na literatura. A metodologia proposta envolve o processamento das imagens SEM usando Morfologia Matemática e os resultados obtidos são discutidos e comparados àqueles processados por Redes Neurais Celulares e pelo método de Otsu. Imagens coletadas do microscópio foram analisadas por técnicas de processamento de imagens para determinação do diâmetro das nanobras. Os resultados mostraram boa concordância entre as metodologias estudadas e o método padrão-ouro indicando que os mesmos podem substituí-lo para constituir uma alternativa automática na caracterização de nanobras. The electrospinning technique represents a simple and convenient process to provide polymers and ceramics bers with both solid and hollow interiors that are exceptionally long in length, uniform in diameter, varying within the interval of few nanometers to several microns, and diversied in composition. Despite the versatility and potencially the scanning electron microscopy (SEM) there is a serious problem to characterize nanobers, as it is not made automatically. This work presents novel methodology software for automatic measurement in SEM images, as an eficient alternative in comparison with semi-automatic softwares proposed in literature. The proposed methodology involves the image processing SEM using Mathematical Morphology and the obtained results are argued and compared with those processing for Celullar Neural Network and Otsu method. The microscope images were assessed and analysed by imagery processing techniques to determinate diameters of nanobers. The results has shown good agreement between the investigated and gold standard methods suggesting that the same ones can substitute it to constitute an automatic alternative in the nanobers characterization.

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Törneman, Hedda. "Development of a porous material from cellulose nanofibrils." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-179266.

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Cellulose nanofibrils are a biobased and renewable material with potential to be used in many different applications. Such applications include air filtration, absorption of liquids, and thermal insulation. To be used for these applications the cellulose nanofibrils must form a porous and dry material. However, maintaining some degree of porosity after drying is difficult, since the fibrils are extracted in liquid and tend to collapse into a dense material upon drying. Certain methods have proven effective for making a dry porous material from cellulose nanofibrils, but these are often expensive and not suitable for large scale production. The aim of this project is to test possible methods for making a highly porous cellulose nanofibril-based material. These methods must be environmentally sustainable and suitable for large scale production. An extensive screening has been conducted with the aim of identifying methods resulting in materials with high porosity. The obtained materials have been analysed further to give a more thorough understanding of the porosity as well as other characteristics. The results indicate that cross-links in the material strengthen the structure, and that drying samples from water always results in complete collapse or very dense materials while drying samples from certain solvents other than water results in more porous materials. The analysed materials had very different porosities, some of which were relatively high. The most porous material analysed by Brunauer-Emmett-Teller gas adsorption had a surface area of 9.5 m2/g. This project gives insight into how cross-linking chemistries and treatment with different solvents and pH affect the resulting cellulose nanofibril-based material, as well as knowledge about which methods can be used to successfully produce dry porous cellulose nanofibril-based materials.

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Josefsson, Gabriella. "Elasticity of Cellulose Nanofibril Materials." Doctoral thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-240250.

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The demand for renewable load-carrying materials is increasing with increasing environmental awareness. Alternative sources for materials manufacturing and design have to be investigated in order to replace the non-biodegradable materials. The work presented in this thesis investigates structure-property relations of such renewable materials based on cellulose nanofibrils. Cellulose is the most abundant polymer on earth and exists in both ordered and disordered phases, where the ordered crystalline cellulose shows excellent mechanical properties. The celluloses nanofibril is composed of partly crystalline cellulose where the stiff crystal regions, or crystallites, are orientated in the axial direction of the fibrils. The cellulose nanofibrils have a high aspect ratio, i.e. length to diameter ratio, with a diameter of less than 100 nm and a length of some micrometres. In the presented work, different properties of the cellulose nanofibril were studied, e.g. elastic properties, structure, and its potential as a reinforcement constituent. The properties and behaviour of the fibrils were studied with respect to different length scales, from the internal structure of the cellulose nanofibril, based on molecular dynamic simulations, to the macroscopic properties of cellulose nanofibril based materials. Films and composite materials with in-plane randomly oriented fibrils were produced. Properties of the cellulose nanofibril based materials, such as stiffness, thickness variation, and fibril orientation distribution, were investigated, from which the effective elastic properties of the fibrils were determined. The studies showed that a typical softwood based cellulose nanofibril has an axial stiffness of around 65 GPa. The properties of the cellulose nanofibril based materials are highly affected by the dispersion and orientation of the fibrils. To use the full potential of the stiff fibrils, well dispersed and oriented fibrils are essential. The orientation distribution of fibrils in hydrogels subjected to a strain was therefore investigated. The study showed that the cellulose nanofibrils have high ability to align, where the alignment increased with increased applied strain.

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Yao, Jian. "High strength and high modulus electrospun nanofibres." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/9120.

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In the last two decades, a rapidly growing polymer processing technology, electrospinning, has attracted great interests as it provides a viable and simple method to create ultra-fine continuous fibres. Despite the potential utilization of electrospun nanofibres in many fields, their success is limited so far due to their poor mechanical properties compared to corresponding textile fibres made from the same polymers, which is mainly ascribed to the low degree of orientation and chain extension of the macromolecules along the fibre axis in such fibres. In this thesis, first an in-depth review of the mechanical properties of electrospun fibres and recent developed methodologies to generate high strength and high modulus nanofibres will be presented. In the experimental work, electrospinning of rigid polymer PPTA was attempted and mechanical properties of obtained fibres were evaluated (Chapter 3). It was shown that the electrospinning process cannot be easily operated in a controllable and continuous manner although some high performance fibres were obtained. Chapter 4 dealt with the electrospinning of reactive mesogens (liquid crystal monomers) by employing polymers (PMMA and PA6) as matrix. The mechanical properties of the resulting composite nanofibres (PA6/RM257) showed dependence on the reactive mesogen (RM257) content and the phase separation between PA6 and RM257. In Chapter 5, a high performance polymer BPDA/PDA/ODA was synthesized and electrospun; the nanofibres were characterized using FTIR and WAXD and their mechanical tests were carried out based on unidirectional mats and multifilament bundles. A Weibull modulus based model was introduced to estimate the tensile strength of single nanofibres in such bundles. Subsequently, composites based on BPO nanofibres in a rubbery thermoplastic matrix were fabricated and evaluated in Chapter 7 using composite mechanics theories for off-axis properties and „Rule of Mixture‟ which were used to back-calculate the Young‟s modulus of single BPO nanofibres. From this it could be concluded that the developed co-polyimide BPO nanofibres exhibit among the highest mechanical properties of electrospun nanofibres reported in literature so far. It can be concluded that the electrospun BPO co-polyimide nanofibres and p-aramid fibres possess among the highest mechanical properties reported for electrospun fibres so far.

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Dunnill, Charles. "Synthesis, characterisation and properties of tantalum based inorganic nanofibres." Connect to e-thesis, 2007. http://theses.gla.ac.uk/173/.

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Thesis (Ph.D.) - University of Glasgow, 2007. Ph.D. thesis submitted to the Department of Chemistry, Faculty of Physical Sciences, University of Glasgow, 2007. Includes bibliographical references. Print version also available.

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Wang, Qijue. "Nanofibrils As The Basic Building Blocks Of Spider Silk." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593092048.

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Spider silk is a natural high-performance biopolymer with superior mechanical properties, resulting from its hierarchical structure. With protein nanofibrils observed in various spider and silkworm silks, the critical role of nanofibrils in achieving the silk's mechanical behavior has been widely suggested by both experimental observations and numerical simulations. However, a close review of available evidence of silk nanofibrils reveals many crucial aspects are still largely ambiguous or unknown. This further hinders the development of advanced silk-based materials. The simple structure of the ribbon-like recluse (Loxosceles) silk provides an ideal opportunity to investigate silk nanofibrils. By studying the surface and internal structure of this silk, we showed that it is entirely composed of nanofibrils. Since the recluse ribbons exhibit the outstanding mechanical properties typical of a good spider silk, we can conclude that the properties of recluse ribbons are already implemented at the level of an individual nanofibril. Furthermore, we took advantage of this system to study the protein makeup of pristine silk nanofibrils. Using both polarized FTIR and Raman spectroscopy, we presented the first-ever vibrational spectra of silk nanofibrils. We were able to identify the presence of different secondary structures, as well as their volumetric percentages and orientations. A detailed structure model of recluse silk was proposed based on our results. To relate the presence of nanofibrils to the natural silk spinning process, we investigated the self-assembly behavior of the native spider spidroin. Both individual and networks of long, thin silk nanofibrils were observed in the presence of shear force and a proper ion concentration. This unprecedented observation suggests the intrinsic tendency of native silk spidroin to form nanofibrils. In summary, through an extensive investigation of the organization, protein makeup, and formation of silk nanofibrils in various natural and in-vitro systems, we revealed the fundamental role of nanofibrils as the basic building blocks of natural spider silk. This will have wide-ranging implications on the understanding of the structure-property relations of spider silk and the development of silk-inspired high-performance materials.

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Bittencourt, Jéssyka Carolina. "Fabricação e caracterização de nanofibras condutoras de Poli(álcool vinílico) com Polianilina (PVA/PANI) para a utilização em sensores de gás amônia /." Presidente Prudente, 2017. http://hdl.handle.net/11449/151348.

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Orientador: Clarissa de Almeida Olivati Banca: Valdemiro Pereira de Carvalho Junior Banca: Edson Laureto Resumo: Neste trabalho, nanofibras de Poli(álcool vinílico) com PVA foram produzidas, variando os parâmetros de eletrofiação: concentração de PVA, rotação e distância do coletor. Após o estudo dos parâmetros de eletrofiação, foram produzidas nanofibras através da adição do polímero condutor, polianilina, PANI, em diferentes concentrações, na matriz isolante de PVA. As nanofibras foram caracterizadas morfologicamente através da técnica de Microscopia eletrônica de Varredura, no qual a amostra que apresentou os melhores resultados foi a amostra de 4%, em massa de PANI, na matriz de PVA, com a rotação de 400 rpm. Em seguida as nanofibras PVA/PANI foram depositadas em eletrodos interdigitados para a realização das caracterizações elétricas AC/DC e teste como sensor de gás, no qual comprovou-se que a densidade e regularidade das nanofibras de PVA/PANI à 4% contribuem na melhora da condutividade e sensibilidade do sensor na presença de gás amônia In this work were produced nanofiber Poly (vinyl alcohol), PVA, varying the electrospinning parameters: PVA concentration, speed and distance of the collector. After studying of the electrospinning parameters, nanofibers were produced through the addition of the conductive polymer, polyaniline, PANI, at different concentrations in the PVA matrix. The nanofibers were morphologically characterized by scanning electron microscopy, which the sample that showed the best results was 4% by weight of PANI in PVA matrix, with 400 rpm rotation. The nanofibers were also deposited in interdigitated electrodes for performing the electrical characterizations AC/DC and gas sensor test, which proved that the density and regularity of the PVA nanofiber/PANI 4% contribute to the improvement of conductivity and sensor sensitivity in the presence of ammonium gas Mestre

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Casadei, Lorenzo. "Sviluppo di un sistema di caratterizzazione elettroacustica per materiali piezoelettrici nanofibrosi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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Nell'elaborato di tesi vengono descritti il processo per la realizzazione di membrane piezoelettriche nanofibrose e lo sviluppo di un sistema di caratterizzazione elettroacustica per materiali piezoelettrici nanofibrosi. Viene successivamente trattata la caratterizzazione delle membrane prodotte utilizzando prima una sorgente vibrazionale sinusoidale e successivamente una sorgente vibrazionale impulsiva.

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Nazir, Ahsan. "Modelling and optimization of electrospun materials for technical applications." Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH0598/document.

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Ce travail de recherche traite de l’optimisation et de la modélisation de nanofibres obtenues par filage électrostatique pour des applications techniques en tant que, a) cellules résistives pour génération de chaleur et b) couche ultra filtrante pour système de protection respiratoire. Afin d’intégrer ces matériaux nanofibreux aux applications visées, deux procédés de production ont été mis en oeuvre, à savoir mono-aiguille et multijets. Une étude statistique a été réalisée pour modéliser et optimiser les non-tissés de nanofibres pour des productions à échelle laboratoire et semi-industrielle. L’outil statistique c’est révélé pertinent pour anticiper la morphologie des matériaux produits et assurer une homogénéité optimale. Les non-tissés présentant les caractéristiques morphologiques souhaitées ont été sélectionnés, testés, et les résultats ont révélé leur fort potentiel pour les champs applicatifs visés. Ces travaux valident deux pistes de recherche qui déboucheraient sur une intégration concrète de ces matériaux innovants Optimization and modelling of electrospun nanofibrous nonwovens and their technical applications, i-e heat generation and respiratory protection, were studied in this work. For utilization in these applications, nanowebs were statistically modelled and optimized using different electrospinning techniques i-e needle and needleless setups based on significance of these techniques for lab and bulk scale production of nanowebs. Moreover, quantitative impact of different electrospinning parameters was also observed. Statistical analysis was found to be a useful tool for study of electrospinning process and production of nanowebs with minimum defects. The optimized nanowebs were used for selected applications and based on results it was concluded that they can be a potential material for both, heat generation and respiratory protection. These observations are expected to initiate more focused studies in both the fields

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Zhang, Zhifei. "Polytetrafluoroethylene nanofibres fabricated by the island-in-the-sea method." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/25989.

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Polytetrafluoroethylene (PTFE) has some unique properties such as high hydrophobicity and high resistance to elevated temperatures, chemicals and solvents, which make it of interest for numerous fibre and textile applications. However, PTFE normally has a very high viscosity and poor flowability in the melt due to its ultra-high molecular weight, meaning that it cannot be readily melt-spun into textile fibres. In addition, PTFE is insoluble in all common organic solvents, prohibiting its use in common solution spinning methods such as dry, wet or electrospinning. Here we aim to develop an easy and environmentally friendly alternative for the production of PTFE nanofibres, using a modified island-in-the-sea spinning process. For this, first a dispersion of PTFE homopolymer, PVA and water was compounded to create a blend of PTFE particles in PVA solution using different methods, including casting, single-step extrusion and two-step-compounding and extrusion. After solid-state drawing of this blend and removal of the PVA, we were able to collect PTFE nanofibres with finest diameters of around 50nm and lengths up to 15μm. The effects of blend composition, morphology and drawing on PTFE fibre formation and properties were studied and discussed. Furthermore, some other material modification systems, including plasticized PVA, or the use ethylene glycol as a solvent, was studied with the aim of scaling up the fabrication of PTFE nanofibres by spinning the PTFE/PVA blend fibres directly for a twin-screw extruder.

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Keulder, Liesl. "The preparation of polyolefin nanofibres by solution electrospinning." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80277.

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Thesis (PhD)--Stellenbosch University, 2013. ENGLISH ABSTRACT: Solution electrospinning is a technique used to produce polymer micro- or nanofibres. Recently a great deal of research has been done on the application of polymer nanofibres produced by this method. The solution electrospinning of polyolefins have not been researched in-depth mainly due to the difficulty in dissolving these polymers in suitable electrospinning solvents. We managed to electrospin polypropylene copolymers at room temperature, obtaining both polymer micro- and nanofibres. A suitable solvent system was developed (cyclohexane/DMF/acetone) that allowed for the room temperature solution electrospinning of these crystalline polypropylene copolymers. It was also shown that using propylene-1-alkene copolymers with a low comonomer content was a facile way of producing crystalline polyolefins nano – and microfibers. Similar attempts to electrospin isotactic polypropylene were unsuccessful, even though lower molecular weight materials were used than in the case of the copolymers. This lead to an investigation of solution melting temperature by SCALLS. The copolymers showed great variance in their solution melting temperatures despite the fact that they all had more or less the same crystallinity and amount of comonomer, indicating that the type of comonomer played an important role in the solubility of the copolymer. The effect of different collectors was investigated, but in the end it was found that between spinning unto ice, foil on ice of just foil, foil still seemed to be the best collector. Comparing crystallinity of the polymer powders with that of the polymer fibres by DSC and WAXD, it was found that there is a difference in the crystallinity of the fibres and the powders. EVOH is a polymer with excellent properties and electropspinning of this polymer is relatively easy due to the fact that it dissolves quite easily in conductive solvents. DMF, Isopropanol/water and DMSO were all tested as suitable solvents and the morphology was compared through the use of SEM. The morphology of the fibres indicated that DMSO was the best solvent. The influence of the spinning parameters was determined for both systems of DMF and DMSO. These nanofibres were used as reinforcement in LDPE matrix and the mechanical properties of the LDPE matrix was improved with the addition of both aligned and unaligned fibres. The next step was the electrospinning of EVOH fibres containing MWCNT. TEM, FE-SEM and TGA were used to confirm the presence of the MWCNT as well as determine the distribution of the MWCNT inside the nanofibres. The nanotubes were distributed through the fibres; however agglomeration of the nanotubes did still take place. The nanofibres containing MWCNT were also used to make composites where the fibres were melted, leaving the MWCNT behind in the polymer matrix. This was done in both LDPE and EVOH matrices. The LDPE/MWCNT composites did not give positive results, on the other hand the EVOH/MWCNT composite showed an improvement in the mechanical properties compared to pure EVOH. The attachment of fluorescent dye molecules to the surface of the MWCNT was attempted and through fluorescent microscopy and the dispersion of the nanotubes inside the fibres as well as the composite could be seen. This study proved that polyolefin nanofibres could be obtained, giving rise to more applications for these versatile polymers. It also confirmed the importance of nanofibres as reinforcement and the use of nanofibres as a way to incorporate MWCNT in a polymer matrix. AFRIKAANSE OPSOMMING: Elektrospin in ‘n oplosmiddel is ‘n tegniek wat gebruik word om polimeer mikro- en nanovesels te produseer. Die afgelope tyd word baie navorsing gedoen oor die aanwending van polimeer nanovesels wat geproduseer word op hierdie manier. Daar is nog min navorsing gepubliseer wat handel oor die elektrospin van poliolefiene uit ‘n oplosmiddel, deels oor hoe moeilik dit is om ‘n geskikte elektrospin oplosmiddel te vind vir hierdie polimere. In hierdie studie het ons mikro- en nanovesels verkry deur polipropileen kopolimere te elektrospin by kamertemperatuur. Die polimere is opgelos in ‘n oplosmiddel sisteem wat bestaan uit sikloheksaan/dimetielformamied/asetoon, by hoë temperatuur en het toegelaat dat die polimere in oplossing bly by kamertemperatuur. Hierdie diverse kopolimere het verskillende resultate gegee, sommige polimere het mikrovesels produseer, waar ander nanovesels geproduseer het. Die vessel morfologie is ondersoek deur die gebruik van Skandering Elektron Mikroskopie (SEM) en daar is gevind dat die vesels nie ‘n gladde voorkoms het nie, maar dat daar kraalvormige morfologie gesien kon word. Om dit te voorkom is sout by die oplosmiddel sisteem gevoeg. Die invloed van die verskillende parameters op die vesels se deursnit is ondersoek vir al die kopolimere. Die byvoeging van sout het gelei tot ‘n meer gladde vesel morfologie. Die effek van die gebruik van verskillende oppervlaktes om die vesels op te vang is ondersoek en die die kristalliniteit van die polimeer poeiers is vergelyk met die kristalliniteit van die polimeer vesels met die hulp van DSC en WAXD. ‘n Poging is aangewend om isotaktiese polipropileen te elektrospin uit oplossing, maar ons kon nie daarin slag om die polimeer op te los nie, al was die molekulêre gewig minder as die van die kopolimere. Dit het gelei tot die ondersoek van die smeltpunt temperatuur in oplossing deur die gebruik van oplossing kristallisasie-analise deur laser lig verstrooing (SCALLS). Al die kopolimere het min of meer dieselfde kristalliniteit en hoeveelheid komonomer bevat, tog het hulle smeltpunt temperatuur in oplossing baie verskil. Dit het gedui op die feit dat die tipe komonomeer ‘n groot rol speel in die oplosbaarheid van die kopolimeer. Die elektrospin van etileen-ko-vinielalkohol (EVOH) is ook ondersoek. DMF, Isopropanol/Water en Dimetielsulfoksied (DMSO) is getoets as geskikte oplosmiddels en die morfologie van die vesels is vergelyk deur die gebruk van SEM. Die tyd wat die polimeer in oplossing gebly het asook die morfologie van die vesels, het aangedui dat DMSO die mees geskikte oplosmiddel was. Die invloed van die elektrospin parameters was vasgestel vir beide DMF en DMSO sisteme. Hierdie nanovesels is gebruik as versterking in ‘n LDPE matriks en die meganiese eienskappe van die LDPE matriks is verbeter deur die toevoeging van beide nie-geweefde en gerigte veselsopppervlakte. Die volgende stap was die elektrospin van EVOH vesels wat multi-ommuurde koolstof nanobuisies (MWCNT) bevat. TEM, FE-SEM en TGA was gebruik om te bevestig dat die vesels wel MWCNT bevat asook om die verspreiding van MWCNT in die vesels aan te dui. Die nanobuisies was versprei deur die vesels, maar bundels nanobuisies het tog voorkom in sommige plekke. Die nanovesels wat MWCNT bevat is ook gebruik om nanosamestellings te maak, waar die vesels gesmelt is om net MWCNT agter te laat in die polimeer matriks. Hierdie was gedoen in beide LDPE en EVOH matrikse. Geen positiewe resultate is verkry vir die LDPE/MWCNT nanosamestelling nie, maar die EVOH/MWCNT nanosamestelling het aan die anderkant ‘n groot verbetering getoon in die meganiese eienskappe in vergelyking met EVOH sonder MWCNT. ‘n Poging was aangewend om fluoreseerende molekules aan die oppervlak van MWCNT te voeg en deur fluoresensie mikroskopie kon die verspreiding van die MWCNT in die vesels asook in die nanosamestellings gesien word. Hierdie studie het bewys dat poliolefien nanovesels gemaak kan word wat lei tot die aanwending van hierdie polimere in nog meer toepassings. Dit het ook die belangrikheid van die gebruik van nanovesels as versterking in nanosamestellings bevestig asook die gebruik van nanovesels as ‘n manier om MWCNT in ‘n matriks te plaas.

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Rempel, Silvana Pereira. "Obtenção de micro/nanofibras poliméricas por fiação por sopro : parâmetros e aplicação no controle de pragas agrícolas." reponame:Repositório Institucional da UCS, 2018. https://repositorio.ucs.br/11338/3937.

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Este trabalho apresenta a obtenção de micro/nanofibras de EVA utilizando o método de fiação por sopro em solução e sua possibilidade de aplicação na agricultura, no controle de pragas, através da incorporação de feromônios sexuais sintéticos. Soluções com concentração de 0,5−15% em massa de EVA em xileno: clorofórmio (96:4% em peso) foram preparadas com base no parâmetro de solubilidade do copolímero. A viscosidade das soluções, assim como o regime de concentração foi determinado por meio de medidas reológicas. A morfologia e estrutura das fibras foram avaliadas por meio de microscopia eletrônica de varredura (MEV-FEG) e difração de raios X (DRX). O perfil de liberação dos feromônios foi determinado com base na perda de massa utilizando termogravimetria (TGA). A obtenção de fibras foi possível nas soluções com regime de concentração semidiluída. As fibras apresentaram diâmetros médios de 95 a 426 nm e seus tamanhos são dependentes da taxa de alimentação. Não há evidências de que as taxas de alimentação utilizadas e a concentração tenham efeito na orientação macromolecular do EVA, assim como a utilização dos feromônios na fiação. A quantidade incorporada nas fibras, bem como a taxa de liberação dos feromônios possui influência do parâmetro de solubilidade. Portanto, dependendo da demanda de liberação é possível obter um sistema de liberação com um balanço entre taxa de liberação e tempo máximo de liberação com base na natureza do sistema polímero/solvente/feromônio. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES This work presents the production of EVA micro/nanofibers using the solution blow spinning method and its possibility of application in agriculture, in pest control, through the incorporation of synthetic sex pheromones. Solutions with a concentration of 0.5-15% by mass of EVA in xylene: chloroform (96:4% by weight) were prepared based on the solubility parameter of the copolymer. The viscosity of the solutions as well as the concentration regime was determined by means of rheological measurements. The morphology and structure of the fibers were evaluated by means of scanning electron microscopy (SEM-FEG) and X-ray diffraction (XRD). The release profile of the pheromones was determined based on the loss of mass using thermogravimetry (TGA). Fibers were obtained in the solutions in the semi-diluted concentration regime. The fibers have diameters of 95 to 426 nm and their sizes are dependent on the feed rate. There is no evidence that feed rates used and concentration have an effect on macromolecular orientation of EVA, as well as the use of pheromones in spinning. The amount incorporated in the fibers, as well as the rate of release of the pheromones influences the solubility parameter. Therefore, depending on the release demand it is possible to obtain a release system with a balance between release rate and maximum release time based on the nature of the polymer/solvent/pheromone system.

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Terrones-Maldonado, Mauricio. "Production and characterisation of novel fullerene-related materials : nanotubes, nanofibres and giant fullerenes." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361404.

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Pottathara, Yasir Beeran. "Graphene based Composites with Cellulose Nanofibrils for Energy storage applications." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS450/document.

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La recherche sur les matériaux diélectriques souples et biodégradable a été augmenté considérablement en raison de l'augmentation des exigences concernant l'énergie et les questions environnementales. Les composites polymériques, avec constante diélectrique élevée ont ainsi, été préférés par rapport aux composites à base de céramique pour les périphériques de stockage de l'énergie. L'objectif de cette thèse est de fabriquer une électrode biodégradable matériaux à base de nano-fibrilles de cellulose natives et oxydés (CNF) et de graphène pour améliorer le stockage diélectrique ainsi que les applications de stockage de charge électrochimique. La présente méthode de réduction, induite par les UV sur l'oxyde de graphène (GO) dans des matrices de cellulose, est une alternative prometteuse aux traitements à base de solvant en évitant la détérioration des propriétés des matériaux et l'utilisation de solvants organiques. Cette méthode pourrait être étendue à d’autres matériaux composites polymères The research on biodegradable and flexible dielectric materials has been increased widely because of increasing requirements about energy and environmental issues. Polymeric composites with high dielectric constant have, thus, been demanded increasingly compared to ceramic based composites for energy storage devices. The objective of this thesis is to fabricate a biodegradable electrode materials based on pristine and oxidized cellulose nanofibrils (CNF) with different graphene based fillers for enhanced dielectric storage as well as electrochemical charge storage applications. The presented dry method of UV induced reduction of graphene oxide (GO) in cellulose matrices are promising alternatives to solvent based treatments avoiding the deterioration of material properties and the use of organic solvents. This method could be extended to alternative polymer composite materials. In contrast to previous reports, the dielectric properties mainly focussed on the higher frequency regions to provide real, intrinsic material properties and obtained significant enhancement than reported studies. This approach gives a new insight to the exact performance of materials on dielectric charge storage applications. The current study gives more insight for the development of flexible, lightweight and biodegradable electrode materials for energy storage device applications

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Muller, Daliana. "Incorporação de polímeros intrinsecamente condutores em nanofibras de celulose bacteriana." Florianópolis, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/99476.

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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência e Engenharia de Materiais Made available in DSpace on 2013-03-04T20:47:41Z (GMT). No. of bitstreams: 1 304106.pdf: 4098740 bytes, checksum: 4900c3d95de1e41dfd987f663838d1b5 (MD5) Nesta tese foi estudada a incorporação de polímeros condutores como polipirrol (PPy), polianilina (PAni) e poli(3,4 etileno dioxi tiofeno) (PEDOT) em membranas de celulose bacteriana (CB) a partir do processo de polimerização oxidativa in situ do pirrol (Py), anilina (Ani) ou 3,4 etileno dioxitiofeno (EDOT) na presença de CB. As condições de obtenção dos compósitos poliméricos de CB/PPy, como: tempo de reação, concentração de pirrol e tipo de agente oxidante (cloreto de ferro III hexahidratado (FeCl3.6H2O) e persulfato de amônio (APS)) foram avaliadas a partir de diferentes técnicas de caracterização. A condutividade elétrica e morfologia dos compósitos de CB/PPy obtidos a partir da polimerização do pirrol com FeCl3.6H2O são dependentes da concentração de Py e do tempo de reação. A interação entre os componentes dos compósitos de CB/PPy, a condutividade elétrica, a morfologia e as propriedades mecânicas são substancialmente influenciadas pelo tipo de agente oxidante utilizado na polimerização in situ. Os ensaios de cultura de células (neuronais PC12 e fibroblastos) nos compósitos de CB/PPy mostraram que estes materiais apresentam viabilidade para serem usados como suportes condutores para proliferação e adesão celular. Para os compósitos CB/PAni verificou-se que a razão do agente oxidante, tempo e meio de reação exercem influência significativa na morfologia, propriedades mecânicas e na condutividade elétrica. Entretanto, o grau de cristalinidade é independente da concentração de anilina e do meio reacional utilizado na preparação de CB/PAni. Nos compósitos de CB/PEDOT, também foi verificado que as propriedades são afetadas pelo tempo de polimerização. Foram obtidos compósitos de CB/PEDOT com elevado valor de condutividade elétrica (15 S.cm-1), maior do que os encontrados para CB/PAni e CB/PPy. Os resultados apresentados neste estudo mostraram que é possível controlar as propriedades de nanofibras de CB recobertas com polímeros condutores através das condições de reação. Os compósitos obtidos neste trabalho são promissores para serem usados em diversas aplicações tecnológicas, tais como: suportes para engenharia de tecidos, liberação controlada de drogas, músculos artificiais, sensores químicos e biológicos etc.

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Ractz, Guilherme Segatt. "Síntese de nanofibras de polianilina e preparação do nanocompósito de polipropileno / polianilina." Pontifícia Universidade Católica do Rio Grande do Sul, 2012. http://hdl.handle.net/10923/7422.

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Made available in DSpace on 2015-06-25T02:05:26Z (GMT). No. of bitstreams: 1 000471013-Texto+Completo-0.pdf: 1943495 bytes, checksum: 36e051cefa7a9d47d6a0d608dff24d67 (MD5) Previous issue date: 2012 The following paper reports the synthesis of polyaniline (PANI) nanofibers and the making of nanocomposites that have polypropylene as their polymer matrix. Polyaniline nanofibers have been synthesized by the quick-mix method. Hydrochloridric and sulfuric acids were evaluated as dopant agents in different reaction temperatures: 25, 60 and 100 °C. Polypropylene (PP) nanocomposites were prepared by adding 1 and 3% (m/m) of PANI nanofibers through three different methods utilized for dispersing the nanocharge in the polymer matrix. This way parameters such as quick-mix in the fusion chamber, masterbach prepping and pre- dispersion of the charge in ethanol were appraised. The morphology and the electric, thermic and mechanic properties of the PANI nanofibers as well as the nanocomposites prepared were evaluated by means of Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Electrical Impedance Spectroscopy (EIS).Nanofibers of the upmost definition were obtained with hydrochloridric acid as the dopant agent in a temperature of 60 °C. The nanofibers prepped using this methodology presented electrical resistivity of 10² Wcm and a decomposition temperature near 300 °C. AFM pictures indicate good charge distribution in the polymer matrix regardless of the chosen preparation method. It was verified that the nanocomposites’ thermic properties were not negatively affected by the addition of PANI nanofibers and composites with similar traction properties to PP’s matrices were produced with a larger ultimate elongation and electrical conducting properties. O presente trabalho relata a síntese de nanofibras de polianilina (PANI) e a preparação de nanocompósitos contendo polipropileno como matriz polimérica. Nanofibras de polianilina foram sintetizadas pelo método da mistura rápida. Ácido clorídrico e ácido sulfúrico foram avaliados como agentes dopantes em diferentes temperaturas de reação: 25, 60 e 100 °C. Nanocompósitos de polipropileno (PP) foram preparados adicionando-se 1 e 3% (m/m) de nanofibras de PANI por três diferentes métodos utilizados para dispersar a nanocarga na matriz polimérica. Assim foram avaliados parâmetros como a mistura direta na câmara de fusão, preparação de masterbach e pré-dispersão da carga em etanol. A morfologia, as propriedades elétricas, térmicas e mecânicas das nanofibras de PANI e dos nanocopósitos preparados foram avaliados por Microscopia Eletronica de Varredura (MEV), Microscopia de Força Atômica (AFM), Análise Termogravimétrica (TGA), Calorimetria Diferencial Exploratória (DSC) e Espectroscopia de Impedância Elétrica (EIE).Nanofibras com morfologia mais definida foram obtidas quando foi utilizado o ácido clorídrico como agente dopante, na temperatura de 60°C. As nanofibras preparadas por essa metodologia apresentaram resistividade elétrica na ordem de 102 cm e temperatura de decomposição próxima a 300°C. Imagens de AFM indicam uma boa distribuição da carga na matriz polimérica, independentemente do método de preparação utilizado. Foi verificado que as propriedades térmicas dos nanocompósitos não foram afetadas negativamente com a adição das nanofibras de PANI, e foram produzidos compósitos com propriedades de tração semelhantes à matriz de PP, com maior alongamento na ruptura e propriedades elétricas condutoras.

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Valente, Cristhiane Alvim. "Síntese de nanofibras de polipirrol para potencial aplicação em conduto biodegradável para regeneração nervosa." Pontifícia Universidade Católica do Rio Grande do Sul, 2014. http://hdl.handle.net/10923/6856.

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Made available in DSpace on 2014-10-15T02:01:02Z (GMT). No. of bitstreams: 1 000462029-Texto+Completo-0.pdf: 6506501 bytes, checksum: ac4fdb8832287abddfd8e14f596d52a1 (MD5) Previous issue date: 2014 Injury of peripheral nerves of accidents at work or home are common carriers and scallfolds of biodegradable polymers with temporary structural function to assist in the regeneration of damaged living tissue are being explored. Conducting polymers such as polypyrrole (PPy), have also been explored because of biocompatibility to various cell types and ease of synthesis. Artificial Nerve Guidance Conduits with multifunctional growth factors (GF) have been studied to improve the regeneration of injured peripheral nerves. The main objective is to prepare polymer composites of poly (lactic - co - glycolic acid) - (PLGA) with PPy nanofibers able to act as a conduit in peripheral nerve regeneration. PPy nanofibers were synthesized via chemical oxidative polymerization with different dopants. Films PLGA / nanofiber PPy / tacrolimus (FK506) were prepared by sandwich solvent casting method. The PPy nanofibers were characterized by FTIR, SEM, electrical impedance spectroscopy and TGA. In vitro degradation of PLGA/PPy composite films was also evaluated. PPy nanofibers of electrically condutive 8. 10-4 S / cm were obtained with dopant p-toluenesulfonic acid (PTSA) in the ratio [dop]: [Py] = 4 and 0 ° C. Films PLGA / PPy-nanofibers exhibit irregular surface morphology with voids that can serve as framewoks for cell growth guided. The degradation of PLGA / PPy films did not alter the pH of the buffer solution, an increase of thickness and mass loss was in the range of 7-21% until 28 days of degradation reviews. The addition of nanofibers favored the process of mass loss of about 4% for the PLGA / PPy thicker (≥ 0. 6g of PLGA) films and 6% for thinner films (0. 2 g PLGA) until 28 days degradation. Lesões dos nervos periféricos por acidentes de trabalho ou doméstico são comuns e suportes de polímeros biodegradáveis com função estrutural temporária para auxiliarem na regeneração de tecidos vivos lesados vêm sendo explorados. Polímeros condutores, como o polipirrol (PPy), também têm sido investigados devido facilidade de síntese e biocompatibilidade. Condutos Artificiais de Orientação Neural multifuncional com fatores de crescimento (FC) vêm sendo estudados para aperfeiçoar a regeneração de feridas em nervos periféricos. O objetivo principal deste trabalho é preparar compósitos poliméricos de poli (ácido láctico-co-ácido glicólico) - (PLGA) com nanofibras de PPy capazes de atuarem como conduto guia na regeneração de nervos periféricos. Nanofibras de PPy foram sintetizadas via polimerização química oxidativa com diferentes agentes dopantes. Filmes de PLGA/nanofibras PPy/Tacromilus (FK506) foram preparados pelo método do sanduíche por evaporação do solvente. As nanofibras de PPy foram caracterizadas por FTIR, MEV, espectroscopia de impedância elétrica e TGA. Também foi avaliada a degradação in vitro dos filmes compósitos de PLGA/PPy. As nanofibras de PPy com condutividade elétrica de 8. 10-4 S/cm foram obtidas com dopante ácido p-toluenosulfônico (APTS) na razão [dop]:[Py] = 4 e na temperatura de 0°C. Filmes de PLGA/PPy-nanofibras apresentam morfologia superficial irregular fibrosa com poros aleatórios que podem servir de arcabouços para o crescimento celular. A degradação dos filmes PLGA/PPy não alteraram o pH do meio, houve aumento de espessuras e as perdas de massas ficaram na faixa de 7-21 % até os 28 dias de degradação avaliados. A adição das nanofibras favoreceu o processo de perda de massa cerca de 4% para os filmes PLGA/PPy mais espessos (≥ 0,6g de PLGA) e 6% para filmes mais finos (0,2 g de PLGA) até os 28 dias de degradação.

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Oliveira, Juliana Bovi de. "Obtenção de Nanofibras de Carbono a partir do Processo de Eletrofiação /." Guaratinguetá, 2016. http://hdl.handle.net/11449/138173.

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Orientador: Edson Cocchieri Botelho Coorientadora: Lília Müller Guerrini Banca: Mirabel Cerqueira Rezende Banca: Silvia Sizuka Oishi Resumo: Nos últimos anos, reforços constituídos de nanoestruturas em carbono, tais como nanotubos de carbono, fulerenos, grafenos e nanofibras de carbono, vêm sendo muito pesquisados devido às suas elevadas propriedades mecânicas, elétricas e térmicas. Uma vez que, as nanofibras de carbono consistem em um reforço contínuo (ou na forma de mantas) de elevada área superficial específica, associado ao fato de que estas podem ser obtidas a um baixo custo e em grandes quantidades, estas vêm se mostrando vantajosas quando comparadas aos tradicionais nanotubos de carbono. Assim, as nanofibras de carbono são ótimas candidatas para a obtenção de materiais avançados, podendo estas serem utilizadas como reforços em compósitos com diversas aplicações, tais como em implantes neurológicos e ortopédicos, como suportes de catalisadores, artefatos para aplicações aeroespaciais, dentre outras. Desta forma, o objetivo principal deste trabalho é a produção de nanofibras de carbono, empregando como precursora a manta de poliacrilonitrila (PAN) obtida pelo processo de eletrofiação via solução polimérica, com posterior utilização como reforço em compósitos poliméricos. Neste trabalho, uma manta de poliacrilonitrila com nanofibras de diâmetro de aproximadamente (375 ± 85) nm foi obtida por eletrofiação, sendo esta posteriormente carbonizada. A massa residual resultante do processo de carbonização foi de aproximadamente 38% em massa, com uma redução de 50% nos diâmetros das nanofibras após a queima das mantas de PAN, sendo que as mesmas apresentaram um rendimento de 25%. Na análise da estrutura cristalina do material carbonizado, verificou-se que o material apresentou uma desorganização estrutural. E a partir do ensaio de condutividade elétrica da manta carbonizada, concluiu-se que o material se comporta como um ... (Resumo completo, clicar acesso eletrônico abaixo) Abstract: In recent years, reinforcement consisting of carbon nanostructures, such as carbon nanotubes, fullerenes, graphenes, and carbon nanofibers has been very researched due to its mechanical, electrical and thermal properties, besides having good thermal conductivity, mechanical resistance and high surface area. Since the carbon nanofibers comprise a continuous reinforcing with high specific surface area, associated with the fact that they can be obtained at a low cost and in large amounts, they have shown to be advantageous compared to traditional carbon nanotubes. Thus, the carbon nanofibers are excellent candidates in order to obtain advanced materials, and these can be used as reinforcements in composites with several applications such as for example, neurological and orthopedic implants, integrates in catalysts systems, devices for aerospace applications, among others. So, the main objective of this work is the processing of carbon nanofibers, using PAN as a precursor, obtained by the electrospinning process via polymer solution, with subsequent use for applications as reinforcement in polymer composites. In this work, PAN nanofibers were produced by electrospining with a diameter of approximately (375 ± 85) nm. The resulting residual weight after carbonization was approximately 38% in mass, with a diameters reduction of 50%, and the same showed a yield of 25%. From the analysis of the crystallinity structure of the carbonized material, it was found that the material presented a disordered structure. From the electrical conductivity results of the specimens, it was concluded that the material behaves as a semi-conductor. The epoxy resin/carbon nanofiber composite presented an elastic modulus value of (3.79 ± 0.48) GPa, a glass transition temperature (Tg) in the range from 108.9 to 135 5 ° C and a linear thermal expansion coefficient within the range of 68 x 10-6 /°C and 408 x 10-6 /°C Mestre

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Zhu, Jian [Verfasser], and Seema [Akademischer Betreuer] Agarwal. "High-performance Electrospun Polymer Nanofibres and Their Composite Materials with Hectorite / Jian Zhu ; Betreuer: Seema Agarwal." Bayreuth : Universität Bayreuth, 2019. http://d-nb.info/1196201730/34.

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Maccaferri, Emanuele. "Studio di membrane nanofibrose ottenute da elettrofilatura di poliarammidi per il rinforzo di materiali compositi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10069/.

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Uno tra i principali problemi dei compositi è il fenomeno della delaminazione. In questo lavoro di tesi sono state prodotte membrane nanofibrose ottenute mediante elettrofilatura di poliarammidi, da impiegare come rinforzo per contrastare tale fenomeno. Sono state quindi preparate soluzioni di Nomex con differenti combinazioni di concentrazione e solvente da sottoporre ad elettrofilatura, e sono stati ricercati i parametri di processo ottimali. La qualità delle nanofibre è stata valutata attraverso analisi SEM e successivamente sono state determinate le proprietà termo-meccaniche delle membrane migliori. Le stesse sono state impiegate per la produzione di compositi in fibra di carbonio a matrice epossidica e l’effetto sulla delaminazione è stato valutato tramite test preliminari ILSS e DCB. Inoltre, è stato valutato al cono-calorimetro il comportamento alla fiamma del composito nano-rinforzato. Sono state anche tentate prove preliminari di elettrofilatura di soluzioni di Kevlar.

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Graebin, Ana Paula. "Síntese de compósitos baseados em polietileno/nanofibras de polianilina e grafite." Pontifícia Universidade Católica do Rio Grande do Sul, 2015. http://hdl.handle.net/10923/7406.

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Made available in DSpace on 2015-06-20T02:07:24Z (GMT). No. of bitstreams: 1 000470698-Texto+Completo-0.pdf: 3211899 bytes, checksum: 304adc552bbe30591d967a6721608b0c (MD5) Previous issue date: 2015 The research work is related to the preparation of polymer composites based on polyaniline (PAni) and graphite. Polyaniline nanofibers were synthesized by the method of rapid mixing. Hybrid load (PAni/NLG) was synthesized by polymerizing aniline in the presence of graphite nanosheets (NLG). Polymer composites were prepared using differents methodologies: melt blending and in situ polymerization. In preparing polymer composites of polyethylene (PE)/PAni, PE/NLG and PE/PAni/NLG by in situ polymerization, the catalyst system was used Cp2ZrCl2/MAO. Polymeric composites by melt blending with the melt PE and conductive load were prepared in the melting chamber. The conductive loads as well as those produced composites were characterized by Scanning Electron Microscopy (SEM), TGA (Thermogravimetric Analysis), DSC (Differential Scanning Calorimetry) and electrical properties (Probe Two Tips). Rapid mixing, nanofiber synthesis methodology was efficient, as were prepared nanofibers with a diameter of approximately 50-80 nm and with yield of the synthesis reaction of 23%. From the results it was found that the in situ polymerization was the most suitable method to produce polymeric composites in the presence of polyaniline, as the composite exhibited good load dispersion inducing the formation of the conductive network. The presence of graphite in hybrid material improves electrical conductivity of composites and the quality of nanofibers is affected positively. The methodology of the mixture by melting was not efficient to disperse the nanofiber Pani in PE matrix. O trabalho de pesquisa está relacionado com a preparação de compósitos de polietileno (PE) contendo carga condutiva baseadas na polianilina (PAni) e grafite. Nanofibras de PAni foram sintetizadas através do método da mistura rápida. Carga híbrida (PAni/NLG) foi sintetizada por meio da polimerização da anilina na presença de nanolâminas de grafite (NLG). Compósitos foram preparados utilizando-se diferentes metodologias: mistura por fusão e polimerização in situ. Na preparação de compósitos poliméricos de polietileno (PE)/PAni, PE/NLG e PE/PAni/NLG, por meio da polimerização in situ, foi utilizado sistema catalítico Cp2ZrCl2/MAO. As cargas condutivas assim como os compósitos produzidos foram caracterizados por MEV (Microscopia Eletrônica de varredura), TGA (Análise Termogravimétrica), DSC (Calorimetria Diferencial de Varredura) e propriedades elétricas (Sonda de Duas Pontas). A interação entre a PAni e o sistema catalítico Cp2ZrCl2/MAO foi investigada através da Técnica da Voltametria Cíclica e de Pulso Diferencial. A mistura rápida, metodologia de síntese de nanofibras mostrou-se eficiente, pois foram preparadas nanofibras com diâmetro de aproximadamente 50-80 nm e com rendimento de reação de 23%. A partir dos resultados constatou-se que a polimerizaçao in situ foi a metodologia mais adequada para produzir compósitos poliméricos na presença de PAni, visto que os compósitos apresentaram boa dispersão da carga induzindo à formação da rede condutiva. A presença de grafite no material híbrido melhora a condutividade elétrica dos compósitos e a qualidade das nanofibras é afetada positivamente. A metodologia da mistura por fusão não foi eficiente para dispersar as nanofibras de Pani na matriz de PE.

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Anún, Joaquin, and Fabio Josè Bagatello. "Diseño e implementación de un equipo de electrohilado para la obtención de nanofibras de hidroxiapatita en gelatina." Bachelor's thesis, Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales, 2017. http://hdl.handle.net/11086/6537.

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Proyecto Integrador (I.Biom.)--FCEFN-UNC, 2017 Busca describir el proceso de diseño, fabricación e implementación de un equipo para la producción de nanofibras de gelatina e hidroxiapatita, a partir de una técnica denominada electrohilado o electrospinning

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Oliveira, Felipo de. "Síntese de nanocompósitos de nanofibras de polianilina e polietileno por meio da polimerização “IN SITU”." Pontifícia Universidade Católica do Rio Grande do Sul, 2011. http://hdl.handle.net/10923/3334.

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Made available in DSpace on 2013-08-07T18:54:45Z (GMT). No. of bitstreams: 1 000434521-Texto+Completo-0.pdf: 3294968 bytes, checksum: fbcc929bfb1cb1c681e58d0bf2918d23 (MD5) Previous issue date: 2011 This work is related to the synthesis of polyaniline nanofibers, a conducting polymer with high electrical conductivity. Nanocomposites with polyaniline nanofibers as filler and polyethylene as the polymer matrix were prepared. The polyaniline nanofibers with average diameters of 80 nm were obtained by interfacial polymerization approach and the nanofibers were characterized by scanning electron microscopy (SEM) and scanning electron transmition (TEM), UV-VIS Spectroscopy, Infrared Spectroscopy (FTIR) and Diferencial Calorimetric Exploratory (DSC). Nanocomposites were prepared by in situ polymerization of ethylene using Cp2ZrCl2 [bis(cyclopentadienyl)zirconium (IV)dichloride)] and methyaluminoxane (MAO) as catalytic system. The nanocomposites were characterized by SEM, TEM, DSC and electrical impedance spectroscopy. SEM micrographs showed that nanofibers addition changes the polyethylene morphology and TEM micrographs showed a good dispersion of nanofibers in polymer matrix. The thermal properties results indicated that nanofibers did not change significantly the melting temperature of the nanocomposites and it decreased the polymer cristallinity. The polyaniline nanofibers showed high electrical conductivity, 4,33 S/cm, and the electrical impedance of the nanocomposites decreased when the polyaniline nanofibers were added to polymer. O presente trabalho se relaciona com a síntese de nanofibras de polianilina, um polímero condutor com elevada condutividade elétrica. Foram produzidos nanocompósitos com as nanofibras de polianilina como carga condutora e o polietileno como matriz polimérica. As nanofibras de polianilina com diâmetros de fibra entre 50 e 100nm foram obtidas por meio da polimerização interfacial da anilina, e foram caracterizadas por Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (TEM), Espectroscopia no Ultravioleta (UV-VIS), Espectroscopia no Infravermelho (FTIR) e Calorimetria Exploratória Diferencial (DSC). A síntese dos nanocompósitos poliméricos foi realizada por meio da polimerização in situ, utilizando o catalisador metalocênico diclorobis(ciclopentadienil)zircônio IV (Cp2ZrCl2) e MAO (metilaluminooxano) como co-catalisador com diferentes quantidades de carga. Os nanocompósitos sintetizados foram caracterizados por MEV, MET, DSC e espectroscopia de impedância elétrica. As micrografias de MEV e MET mostraram que a adição das nanofibras de polianilina modificaram a morfologia do polietileno puro resultando em nanocompósitos com uma boa dispersão das nanofibras na matriz polimérica. Os resultados das propriedades térmicas mostraram que a adição das nanofibras não modificou significamente a temperatura de fusão e diminuiu a cristalinidade do polímero. As nanofibras de polianilina apresentaram elevada condutividade elétrica, 4,33 S/cm-1, e diminuiram a impedância elétrica dos nanocompósitos sintetizados.

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Alves, Annelise Kopp. "Obtenção de micro e nanofibras de TiO2 por electrospinning : caracterização de propriedades e atividade fotocatalítica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/13513.

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Este trabalho versou sobre a obtenção de micro e nanofibras de óxido de titânio pela técnica de electrospinning de uma solução polimérica. A obtenção do sistema sol-gel, precursor de óxidos e aditivos, foi baseada na hidrólise e condensação de sais, como propóxido de titânio, cloreto de zircônio e nitrato de cério. Foram investigadas soluções poliméricas de PVA, PVB, PVP e POE, em diferentes concentrações, 5, 10, 15 e 20%, em meio aquoso, ou alcoólico. Esses sistemas foram caracterizados quanto a sua viscosidade e condutividade iônica. Após um período de 24h de repouso, as soluções poliméricas contendo os íons de interesse foram submetidas ao processo de electrospinning. Utilizaram-se como parâmetros de processo: tensão elétrica entre 5 e 20kV, capilares entre 0,3 e 2,5mm, e distâncias entre 100 e 150mm. Após 30 minutos, as fibras foram coletadas em um cilindro rotativo, formando um não-tecido. As fibras assim obtidas foram submetidas a um tratamento térmico até a temperatura de 1000°C, com taxa de aquecimento de 86K/h. Após o tratamento térmico, as fibras foram caracterizadas quanto a sua morfologia, área superficial, cristalinidade (fases cristalinas e tamanho de cristalito), e atividade fotocatalítica. O sistema contendo PVP em solução alcoólica e formulado com propóxido de titânio (TiP) e ácido acético na proporção de 1:1 (PVP:TiP+ácido acético) mostrou-se o mais adequado para a produção de fibras. Após o tratamento térmico, as fibras de óxido de titânio apresentaram diâmetros médios entre 150 e 525nm. Dependendo da formulação utilizada, fibras tratadas termicamente acima de 700°C deram origem à fase anatase ou a uma mistura das fases anatase e rutilo. A área superficial dessas fibras aumenta com o aumento da temperatura de tratamento térmico até o máximo de 142,1m2/g, quando tratadas a 650°C, diminuindo após essa temperatura. A atividade fotocatalítica foi comparada ao produto comercial TiO2 P25, para a descoloração de uma solução contendo 20ppm de azul de metileno e outra contendo 20ppm de alaranjado de metila. Para ambos os sistemas, as fibras com tratamento térmico a 650°C obtiveram a maior eficiência, degradando totalmente o corante em 65 e 55 minutos, respectivamente para o azul de metileno e o alaranjado de metila. O padrão P25 degradou tais compostos em 45 minutos. The synthesis of titanium oxide micro and nanofiber using electrospinning of a polymer solution was studied in this thesis. The development of a sol-gel system, containing oxide precursor and additives, was based on the hydrolysis and condensation of salts such as titanium propoxide, zirconium chloride and cerium nitrate. Polymer solutions, PVA, PVB, PVP and POE, have been investigated for different concentrations, 5, 10, 15 and 20%, in water or alcohol. These systems were characterized by theirs viscosity and ionic conductivity. After a period of 24 hours, the polymer solutions containing the ions of interest were submitted to the electrospinning process. The operation parameters were: electric tension between 5 and 20kV, capillaries between 0.3 and 2.5mm, and distances between 100 and 150mm. After 30 minutes, the fibers were collected in a rotating cylinder, as a non-tissue. Fibres thus obtained were subjected to heat treatment until the temperature of 1000°C, with heating rate of 86K/h. After heat treatment, the fibres were characterized by their morphology, surface area, crystallinity (crystalline phases and critalitte size), and photocatalytic activity. The system containing PVP in alcoholic solution and made of titanium propoxide (TiP) and acetic acid in the proportion of 1:1 (PVP: TiP + acetic acid) proved to be the most suitable for the production of fibres. After heat treatment, the fibres of titanium oxide had average diameters between 150 and 525nm. Depending on the composition used, fibres heat treated above 700°C led to anatase or a mixture of anatase and rutile phases. The surface area of these fibers increases with increasing temperature heat treatment up to 142.1 m2/g, when treated at 650°C, decreasing after this temperature. The photocatalytic activity of the fibers was compared to commercial TiO2 P25, for discoloration of a solution containing 20ppm of methylene blue and another containing 20ppm of methylorange. For both systems, fibers with heat treatment at 650°C degraded completely the dyes in 65 and 55 minutes, respectively, for the methylene blue and methylorange. The standard P25 deteriorated such compounds in 45 minutes.

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Fall, Andreas. "Cellulose nanofibril materials with controlled structure : the influence of colloidal interactions." Licentiate thesis, KTH, Fiberteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-49159.

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Nanoparticles are very interesting components. Due to their very large specific surface area they possess properties in between molecules and macroscopic materials. In addition, a material built up of hierarchically assembled nanoparticles could obtain unique properties, not possessed by the nanoparticles themself. A very interesting group of nanoparticles is the cellulose nanofibrils. The fibrils are found in various renewable resources such as wood, bacteria and tunicates. In this work fibrils extracted from wood is studied. In wood the fibrils are the smallest fibrous component with the approximate dimensions; 4 nm in width and length in the micrometer range, providing a high aspect ratio. In addition, they have a crystallinity above 60% and, hence, a high stiffness. These fibrils are hierarchically ordered in the wood fiber to give it its unique combination of flexibility and strength. The properties of the fibrils make them very suitable to be used as reinforcement elements in composites and, due to their ability to closely pack, to make films with excellent gas barrier properties. The key aspect to design materials, efficiently utilizing the properties of the individual fibrils, is to control the arrangement of the fibrils in the final material. In order to do so, the interactions between fibrils have to be well characterized and controlled. In this thesis the interaction between fibrils in aqueous dispersions is studied, where the main interactions are attractive van der Waals forces and repulsive electrostatic forces. The electrostatic forces arise from carboxyl groups at the fibrils surface, which either are due to hemicelluloses at the fibrils surfaces or chemically introduced to the cellulose chain. This force is sensitive to the chemical environment. It decreases if the pH is reduced or if the salt concentration is increased. If it is strongly reduced the system aggregates. In dilute dispersions aggregation causes formation of multiple clusters, whereas in semi-dilute dispersions (above the overlap concentration) a volume filling network, i.e. a gel, is formed. The tendency of aggregation, i.e. the colloidal stability, can be predicted by using the DLVO theory. In this thesis DLVO predictions are compared to aggregation measurements conducted with dynamic light scattering. Good agreement between experiments and the designed theoretical model was found by including specific interactions between added counter-ions and the carboxyl groups of the fibrils in the model. Thus, the surface charge is both reduced by protonation and by specific interactions. This emphasizes a much larger effect of the counter-ions on the stability then generally thought. Hence, this work significantly improves the understanding of the interfibril interactions in aqueous media. As mentioned above, the fibrils can be physically cross-linked to form a gel. The gelation is an instant process, occurring at pH or salt levels causing the interfibril repulsion to decrease close to zero. If a well dispersed stationary dispersion is gelled, the homogenous and random distribution of the fibrils is preserved in the gel. These gels can be used as templates to produce composites by allowing monomers or polymers to enter the network by diffusion. In an effort to mimic processes occurring in the tree, producing materials with fibrils aligned in a preferred direction, the ability to form gels with controlled fibril orientation were studied. Such networks were successfully produced by applying strain to the system prior or past gelation. Orientation prior gelation was obtained by subjecting the dispersion to elongational flow and freezing the orientation by “turning off” the electrostatic repulsion. Orienting the fibrils after gelation was achieved by applying shear strain. Due to the physical nature of the crosslinks, rotation in the fibril-fibril joints can occur, enabling the fibrils to align in the shear direction. This alignment significantly increased the stiffness of the gels in the shear direction. QC 20111205

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Ractz, Guilherme Segatt. "S?ntese de nanofibras de polianilina e prepara??o do nanocomp?sito de polipropileno / polianilina." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2012. http://tede2.pucrs.br/tede2/handle/tede/6171.

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Submitted by Setor de Tratamento da Informa??o - BC/PUCRS (tede2@pucrs.br) on 2015-06-24T21:45:32Z No. of bitstreams: 1 471013 - Texto Completo.pdf: 1943495 bytes, checksum: 36e051cefa7a9d47d6a0d608dff24d67 (MD5) Made available in DSpace on 2015-06-24T21:45:32Z (GMT). No. of bitstreams: 1 471013 - Texto Completo.pdf: 1943495 bytes, checksum: 36e051cefa7a9d47d6a0d608dff24d67 (MD5) Previous issue date: 2012-07-16 The following paper reports the synthesis of polyaniline (PANI) nanofibers and the making of nanocomposites that have polypropylene as their polymer matrix. Polyaniline nanofibers have been synthesized by the quick-mix method. Hydrochloridric and sulfuric acids were evaluated as dopant agents in different reaction temperatures: 25, 60 and 100 ?C. Polypropylene (PP) nanocomposites were prepared by adding 1 and 3% (m/m) of PANI nanofibers through three different methods utilized for dispersing the nanocharge in the polymer matrix. This way parameters such as quick-mix in the fusion chamber, masterbach prepping and pre- dispersion of the charge in ethanol were appraised. The morphology and the electric, thermic and mechanic properties of the PANI nanofibers as well as the nanocomposites prepared were evaluated by means of Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Electrical Impedance Spectroscopy (EIS). Nanofibers of the upmost definition were obtained with hydrochloridric acid as the dopant agent in a temperature of 60 ?C. The nanofibers prepped using this methodology presented electrical resistivity of 10? Wcm and a decomposition temperature near 300 ?C. AFM pictures indicate good charge distribution in the polymer matrix regardless of the chosen preparation method. It was verified that the nanocomposites? thermic properties were not negatively affected by the addition of PANI nanofibers and composites with similar traction properties to PP?s matrices were produced with a larger ultimate elongation and electrical conducting properties. O presente trabalho relata a s?ntese de nanofibras de polianilina (PANI) e a prepara??o de nanocomp?sitos contendo polipropileno como matriz polim?rica. Nanofibras de polianilina foram sintetizadas pelo m?todo da mistura r?pida. ?cido clor?drico e ?cido sulf?rico foram avaliados como agentes dopantes em diferentes temperaturas de rea??o: 25, 60 e 100 ?C. Nanocomp?sitos de polipropileno (PP) foram preparados adicionando-se 1 e 3% (m/m) de nanofibras de PANI por tr?s diferentes m?todos utilizados para dispersar a nanocarga na matriz polim?rica. Assim foram avaliados par?metros como a mistura direta na c?mara de fus?o, prepara??o de masterbach e pr?-dispers?o da carga em etanol. A morfologia, as propriedades el?tricas, t?rmicas e mec?nicas das nanofibras de PANI e dos nanocop?sitos preparados foram avaliados por Microscopia Eletronica de Varredura (MEV), Microscopia de For?a At?mica (AFM), An?lise Termogravim?trica (TGA), Calorimetria Diferencial Explorat?ria (DSC) e Espectroscopia de Imped?ncia El?trica (EIE). Nanofibras com morfologia mais definida foram obtidas quando foi utilizado o ?cido clor?drico como agente dopante, na temperatura de 60?C. As nanofibras preparadas por essa metodologia apresentaram resistividade el?trica na ordem de 102 ?cm e temperatura de decomposi??o pr?xima a 300?C. Imagens de AFM indicam uma boa distribui??o da carga na matriz polim?rica, independentemente do m?todo de prepara??o utilizado. Foi verificado que as propriedades t?rmicas dos nanocomp?sitos n?o foram afetadas negativamente com a adi??o das nanofibras de PANI, e foram produzidos comp?sitos com propriedades de tra??o semelhantes ? matriz de PP, com maior alongamento na ruptura e propriedades el?tricas condutoras.

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Vincent, Cécile. "Le composite cuivre / nanofibres de carbone." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2008. http://tel.archives-ouvertes.fr/tel-00377607.

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Le matériau composite Cu/NFC (Nano Fibre de Carbone) peut être utilisé en tant que drain thermique par les industriels de l'électronique de puissance. En remplacement du cuivre, il doit combiner une conductivité thermique élevée et un coefficient de dilatation thermique adapté à celui de la céramique du circuit imprimé (alumine ou nitrure d'aluminium). Après avoir étudié les propriétés de la matrice cuivre et des NFC, plusieurs méthodes de synthèse du composite Cu/NFC ont été développées. Le composite a tout d'abord été élaboré par métallurgie des poudres. Puis, dans le but d'améliorer l'homogénéité, il a été envisagé de revêtir individuellement chaque NFC par du cuivre déposé par voie chimique electroless ainsi que par une méthode originale de décomposition d'un sel métallique. Des mesures de densité et de propriétés thermiques (conductivité et dilatation) ainsi que les caractérisations microstructurales de ces matériaux montrent la complexité de l'élaboration d'un tel composite. En effet, la dispersion des nanofibres, la nature des interfaces fibres/matrice et surtout les phénomènes thermiques à l'échelle nanométrique sont autant de paramètres à contrôler afin d'obtenir les propriétés recherchées. La simulation numérique et analytique, qui a été mise en oeuvre en parallèle a été corrélée aux résultats expérimentaux, afin de prédire les propriétés finales de nos matériaux.

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Schifino, Gioacchino. "Elettrofilatura di miscele di cheratina e PLA caricate con ossido di grafene per la produzione di materiali nanofibrosi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19189/.

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In questo elaborato di tesi sperimentale sono state preparate delle nanofibre elettrofilate di cheratina e PLA caricate con differenti percentuali in peso di grafene ossido. In questo particolare sistema, la dimensione del nano-rinforzo è paragonabile alla dimensione delle nanofibre (circa 150 nm), contrariamente alle convenzionali dimensioni dei rinforzi utilizzati per creare materiali compositi. La matrice polimerica utilizzata è una miscela costituita da cheratina e PLA che ha mostrato interazioni positive di interfase tra i due polimeri. Sono stati studiati gli effetti dei parametri di processo di elettrofilatura sulla morfologia delle nanofibre ottenute. Inoltre, è stata studiata l’influenza del grafene ossido sul processo di elettrofilatura, sulla morfologia delle nanofibrose, sulla viscosità delle miscele dei due polimeri e sulle proprietà termiche e meccaniche delle membrane nanofibrose elettrofilate. Tutte le miscele preparate sono state elettrofilate con successo ed i diametri delle nanofibre ottenute variano da 60-400 nm. I dati sperimentali hanno mostrato una diminuzione del diametro delle nanofibre all’aumentare della concentrazione di grafene ossido dovuta alla diminuzione di viscosità e probabile aumento della conducibilità delle soluzioni contenenti. Le analisi termiche hanno messo in evidenza che c’è un effetto nucleante del grafene ossido che induce, probabilmente, l’organizzazione delle catene proteiche. Le analisi meccaniche in trazione hanno mostrato un aumento del modulo di Young e del carico a rottura delle nanofibre elettrofilate caricate con grafene ossido.

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Silva, Bárbara Estefânia de Almeida. "Tratamento a plasma de nanofibrilas de celulose para aplicação em compósitos." Universidade Federal de São Carlos, 2017. https://repositorio.ufscar.br/handle/ufscar/9160.

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Submitted by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T16:37:26Z No. of bitstreams: 1 SILVA_Barbara_2017.pdf: 2018251 bytes, checksum: 6dab58bc6d22c81d23f1cfb7011353bf (MD5) Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T16:37:37Z (GMT) No. of bitstreams: 1 SILVA_Barbara_2017.pdf: 2018251 bytes, checksum: 6dab58bc6d22c81d23f1cfb7011353bf (MD5) Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T16:37:47Z (GMT) No. of bitstreams: 1 SILVA_Barbara_2017.pdf: 2018251 bytes, checksum: 6dab58bc6d22c81d23f1cfb7011353bf (MD5) Made available in DSpace on 2017-10-17T16:38:00Z (GMT). No. of bitstreams: 1 SILVA_Barbara_2017.pdf: 2018251 bytes, checksum: 6dab58bc6d22c81d23f1cfb7011353bf (MD5) Previous issue date: 2017-03-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The application of cellulose nanofibrils to the production of composites has been studied and presents promising results, mainly due to the abundance of the material, which is of a renewable source, and to its low cost. However, the presence of the hydroxyl groups in their chain and their storage in aqueous solutions limits their application as reinforcement in nonpolar matrix composites. In this context, this work aimed to modify the wettability and adhesion properties of films of cellulose nanofibrils to apolar matrices, through plasma treatment. For this, nanocellulose films with thickness of 38 ? 8 ?m were produced by the casting method, from a suspension of nanofibrils in water. The atomic force microscopy characterization (AFM) of the suspended nanofibrils indicated that most of them have an average diameter of less than 75 nm. Each film obtained, after drying the suspension, was then cut into 13 samples with 2 x 1 cm, 12 of which were exposed to plasma and one stored as untreated. Three films were treated with oxygen plasma, with excitation power of 150 W, for 30 minutes and pressure of 0.1, 0.3 and 0.5 Torr. Another three films were treated with sulfur hexafluoride plasma at pressures of 0.1, 0.2 and 0.3 Torr, with a power of 150 W for 15 minutes. It was observed that weight loss was greater than 40% for the films treated with the most extreme conditions oxygen and sulfur hexafluoride. The results also showed that the treatments with sulfur hexafluoride promoted the reduction of the receptivity of the samples to the liquids, with contact angles of approximately 60º for water and 50º for diiodomethane. The profilometry technique revealed that the roughness of the films varied after the treatment with oxygen and sulfur hexafluoride, but the high error bars impede a definitive conclusion on the tendency of these variations. The X-ray diffraction analysis (XRD) indicated no significant change in the crystallinity of the samples with the treatments. In the Fourier Transform Infrared absorption spectra (FTIR), a C-F bonding related peak appeared for the 0.3 Torr sulfur hexafluoride treated sample, indicating the presence of fluorine in that sample. The scanning electron microscopy (SEM) allowed the visualization of the changes in the topography of the films, due to the etching processes resulting from the action of the plasma and the films ruptures caused by the high removal of surface material. In order to test the incorporation of treated films into composites using polyolefins as the matrix, polyethylene pellets were solubilized in xylene for the production of composite films. The treated and untreated nanocellulose films were placed in Petri dish jointly to the polyethylene films still dissolved and left at room temperature. After drying, adhesion between the films was tested through the adhesive tape test, resulting in class-zero adherence, according to the technical standard. It is believed that the lack of adhesion is a result of the composite production method that should be optimized for future work, in order to provide a better investigation of the effects of plasma on the surface properties of the film of cellulose nanofibrils. A aplicação de nanofibrilas de celulose à produção de compósitos vem sendo estudada e apresenta resultados promissores, principalmente devido à abundância do material, que é de fonte renovável, e ao seu baixo custo. Contudo, a presença dos grupos hidroxila em sua cadeia e o seu armazenamento em soluções aquosas impede sua aplicação como reforço em compósitos de matrizes apolares. Nesse contexto, esse trabalho buscou modificar as propriedades de molhabilidade e aderência de filmes de nanofibrilas de celulose a matrizes apolares, através de tratamento a plasma. Para isso, filmes de nanocelulose com espessura de 38 ? 8 ?m foram produzidos pelo método de casting, a partir de uma suspensão de nanofibrilas em água. A caracterização por microscopia de força atômica (AFM) das nanofibrilas em suspensão indicou que a maior parte destas apresenta diâmetro médio inferior a 75 nm. Cada filme obtido, após a secagem da suspensão, foi então cortado em 13 amostras de 2 x 1 cm, sendo 12 destas expostas ao plasma e uma armazenada como não tratada. Três filmes foram tratados com plasma de oxigênio, com potência de excitação de 150 W, por 30 minutos e pressão de 0,1, 0,3 e 0,5 Torr. Outros três filmes foram tratados com plasma de hexafluoreto de enxofre, nas pressões 0,1, 0,2 e 0,3 Torr, com potência de 150 W por 15 minutos. Observou-se que houve perda de massa superior a 40% para os filmes tratados com as condições mais extremas de oxigênio e hexafluoreto de enxofre. Os resultados demonstraram também que os tratamentos com hexafluoreto de enxofre promoveram a diminuição da receptividade a líquidos das amostras, com ângulos de contato de aproximadamente 60º para água e 50º para o diiodometano. A técnica de perfilometria revelou que a rugosidade dos filmes variou após o tratamento com oxigênio e hexafluoreto de enxofre, porém as elevadas barras de erro impediram uma conclusão definitiva sobre a tendência dessas variações. As análises de difração de raios X (DRX) indicaram não haver alteração significativa na cristalinidade das amostras com os tratamentos. Nos espectros de absorção no infravermelho por transformada de Fourier (FTIR), foi observado o surgimento de um pico relacionado à ligação C-F para a amostra tratada com 0,3 Torr de hexafluoreto de enxofre, que indica a presença de flúor nessa amostra. As análises de microscopia eletrônica de varredura (MEV) permitiram visualizar as alterações na topografia dos filmes, devido aos processos de ecthing decorrentes da ação do plasma e os rompimentos ocasionados pela elevada remoção de material da superfície. A fim de testar a incorporação dos filmes tratados em compósitos que utilizam poliolefinas como matriz, pellets de polietileno foram solubilizados em xileno para produção de filmes compósitos. Os filmes de nanocelulose tratados e não tratados foram dispostos em placa de Petri junto aos filmes de polietileno ainda dissolvidos e deixados em temperatura ambiente. Depois de secos, a adesão entre os filmes foi testada através do teste de fita-cola, resultado em adesão classe zero, conforme a norma técnica. Acredita-se que a falta de adesão é resultado do método de produção do compósito que deve ser otimizado para trabalhos futuros, com o objetivo de proporcionar uma melhor investigação dos efeitos do plasma sobre as propriedades da superfície do filme de nanofibrilas de celulose.

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Godoy, Vitor Alexandre Garcia. "Processamento de nanofibras de poliamida 66 / nanotubos de carbono de múltiplas camadas por eletrofiação." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/866.

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Made available in DSpace on 2016-06-02T19:12:20Z (GMT). No. of bitstreams: 1 4465.pdf: 10774781 bytes, checksum: 2e442c2a3e4dd9681006bcb583a7c8af (MD5) Previous issue date: 2010-03-26 Financiadora de Estudos e Projetos Nanocomposite fibers with polymer matrix have many applications, such as protective clothing, filtration and artificial blood vessels. Many of these applications require that the fiber has nanometric size due to some properties, as high surface area and high aspect ratio. In this research, aligned and non-aligned nanocomposites of polyamide 6,6 with multiwalled carbon nanotubes (MWNT) in formic acid solvent were produced by electrospinning, studying the influence of the process variables (as polymer concentration in the solution, electrical field and functionalization of MWNT) in the fiber morphology and diameter. Fibras de nanocompósitos com matriz polimérica possuem diversas aplicações, como roupas protetoras, filtração, cobertura de feridas e vasos sanguíneos artificiais. Muitas dessas aplicações requerem que as fibras possuam tamanho nanométrico devido a algumas propriedades, como alta área superficial e elevada razão de aspecto (razão do comprimento em relação ao diâmetro da fibra). Nesta pesquisa, foram produzidos nanocompósitos alinhados e não-alinhados de poliamida 6,6 com nanotubos de carbono com multi-paredes (PA-6,6/MWNT) funcionalizados ou não com grupos carboxilas em solução de ácido fórmico, estudando-se a influência das variáveis de processamento (concentração da solução e campo elétrico) no diâmetro e morfologia das fibras. As análises das micrografias de microscopia eletrônica de varredura e transmissão permitiram calcular o diâmetro médio das fibras, da ordem de nanômetros e analisar o encapsulamento dos nanotubos de carbono pelas nanofibras.

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Moreira, Francys Kley Vieira. "Desenvolvimento de nanocompósitos poliméricos biodegradáveis a partir de pectina, amido e nanofibras de celulose." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/817.

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Made available in DSpace on 2016-06-02T19:12:05Z (GMT). No. of bitstreams: 1 3298.pdf: 5267625 bytes, checksum: c21d0a6b7606b0e18816dca04d889675 (MD5) Previous issue date: 2010-09-16 Universidade Federal de Sao Carlos The objective of this project was the preparation of biodegradable films from polymer blends of citrus pectin (PEC) and thermoplastic starch (TPS) and the modification of its mechanical properties by formation of nanocomposites with cellulose nanofibers (NCel). The project was conducted in three stages. Firstly, the nanofibers were obtained from bleached sugarcane bagasse fibers (FBC) by hydrolysis with hydrochloric (HCl) and sulfuric (H2SO4) acids. The characterizations revealed nanofibers with needle-like morphology and diameters lower than 20 nm. The thermal stability of NCel obtained with HCl was higher than H2SO4 one. In the second stage, a factionary factorial design was applied to define a suitable processing condition for TPS/PEC blends (100/0, 75/25, 50/50, 25/75 e 0/100) in a mixer Haake, with posterior microstructural and mechanical characterizations of the blends. It was defined the condition of 130ºC, 160 RPM and 4 min to processing TPS/PEC blends, which showed biphasic microstructure and mechanical strength decreased by increase of TPS content. Due to this, NCel were incorporated at concentration of 1, 5, 10 and 15% (w/w) in the processing under different mixture conditions, aiming the improvement of the mechanical performance of the TPS/PEC blend 50/50. The characterization results evidenced that water vapour permeability, tensile strength and elastic modulus of the blend were significantly improved in 48, 150 and 350%, respectively, only with 5% of NCel. The better results were obtained by use of NCel-S and mixture of the nanocomposite formulations into milling ball equipment. The study of this project evidences the great potential of the cellulose nanofibers to the improvement of the properties in biodegradable polymeric systems based in pectin and starch natural polymers. O presente trabalho teve como objetivo a preparação de filmes biodegradáveis a partir de blendas de pectina (PEC) e amido termoplástico (TPS) e o uso de nanofibras de celulose (NCel) como agente de reforço para modificação das propriedades mecânicas destes materiais. O trabalho foi conduzido em três momentos de estudo. Inicialmente as nanofibras foram obtidas via o método da hidrólise ácida com ácido clorídrico (HCl) e sulfúrico (H2SO4) a partir da fibra branqueada do bagaço de cana-de-açúcar (FBC). As caracterizações revelaram nanofibras de formato agulhado com diâmetros menores que 20 nm. A estabilidade térmica das nanofibras foi maior para a hidrólise com HCl (NCel-C) do que com H2SO4 (NCel-S). No segundo momento, foi aplicado um planejamento fatorial fracionário para estabelecer uma condição ótima de processamento da blenda TPS/PEC em cinco proporções mássicas (100/0, 75/25, 50/50, 25/75 e 0/100) em misturador Haake, com subseqüentes caracterizações microestruturais e mecânicas das blendas. Foi definida a condição de 130ºC, 160 rpm e 4 minutos para processamento das blendas TPS/PEC as quais apresentaram microestrutura multifásica e desempenho mecânico modificado pelo aumento do teor de TPS. As nanofibras foram então incorporadas nas concentrações de 1, 5, 10 e 15% no processamento sob diferentes condições de mistura buscando modificar o desempenho mecânico da blenda TPS/PEC 50/50. Os resultados das caracterizações evidenciaram que a permebilidade ao vapor de água, resistência à tração e o módulo elástico da blenda apresentaram aumentos significativos de 25, 150 e 350%, respectivamente, apenas com a adição 5% de nanofibras. Os resultados que evidenciaram maiores aumentos foram o uso de NCel-S e mistura das nanofibras na matriz TPS/PEC com moinho de bolas. Os resultados desta dissertação evidenciam o potencial desempenho das nanofibras de celulose sobre as propriedades dos sistemas poliméricos biodegradáveis a base de pectina e amido

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Graebin, Ana Paula. "S?ntese de comp?sitos baseados em polietileno/nanofibras de polianilina e grafite." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2015. http://tede2.pucrs.br/tede2/handle/tede/6152.

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Submitted by Setor de Tratamento da Informa??o - BC/PUCRS (tede2@pucrs.br) on 2015-06-19T11:25:03Z No. of bitstreams: 1 470698 - Texto Completo.pdf: 3211899 bytes, checksum: 304adc552bbe30591d967a6721608b0c (MD5) Made available in DSpace on 2015-06-19T11:25:03Z (GMT). No. of bitstreams: 1 470698 - Texto Completo.pdf: 3211899 bytes, checksum: 304adc552bbe30591d967a6721608b0c (MD5) Previous issue date: 2015-03-23 Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES The research work is related to the preparation of polymer composites based on polyaniline (PAni) and graphite. Polyaniline nanofibers were synthesized by the method of rapid mixing. Hybrid load (PAni/NLG) was synthesized by polymerizing aniline in the presence of graphite nanosheets (NLG). Polymer composites were prepared using differents methodologies: melt blending and in situ polymerization. In preparing polymer composites of polyethylene (PE)/PAni, PE/NLG and PE/PAni/NLG by in situ polymerization, the catalyst system was used Cp2ZrCl2/MAO. Polymeric composites by melt blending with the melt PE and conductive load were prepared in the melting chamber. The conductive loads as well as those produced composites were characterized by Scanning Electron Microscopy (SEM), TGA (Thermogravimetric Analysis), DSC (Differential Scanning Calorimetry) and electrical properties (Probe Two Tips). Rapid mixing, nanofiber synthesis methodology was efficient, as were prepared nanofibers with a diameter of approximately 50-80 nm and with yield of the synthesis reaction of 23%. From the results it was found that the in situ polymerization was the most suitable method to produce polymeric composites in the presence of polyaniline, as the composite exhibited good load dispersion inducing the formation of the conductive network. The presence of graphite in hybrid material improves electrical conductivity of composites and the quality of nanofibers is affected positively. The methodology of the mixture by melting was not efficient to disperse the nanofiber Pani in PE matrix. O trabalho de pesquisa est? relacionado com a prepara??o de comp?sitos de polietileno (PE) contendo carga condutiva baseadas na polianilina (PAni) e grafite. Nanofibras de PAni foram sintetizadas atrav?s do m?todo da mistura r?pida. Carga h?brida (PAni/NLG) foi sintetizada por meio da polimeriza??o da anilina na presen?a de nanol?minas de grafite (NLG). Comp?sitos foram preparados utilizando-se diferentes metodologias: mistura por fus?o e polimeriza??o in situ. Na prepara??o de comp?sitos polim?ricos de polietileno (PE)/PAni, PE/NLG e PE/PAni/NLG, por meio da polimeriza??o in situ, foi utilizado sistema catal?tico Cp2ZrCl2/MAO. As cargas condutivas assim como os comp?sitos produzidos foram caracterizados por MEV (Microscopia Eletr?nica de varredura), TGA (An?lise Termogravim?trica), DSC (Calorimetria Diferencial de Varredura) e propriedades el?tricas (Sonda de Duas Pontas). A intera??o entre a PAni e o sistema catal?tico Cp2ZrCl2/MAO foi investigada atrav?s da T?cnica da Voltametria C?clica e de Pulso Diferencial. A mistura r?pida, metodologia de s?ntese de nanofibras mostrou-se eficiente, pois foram preparadas nanofibras com di?metro de aproximadamente 50-80 nm e com rendimento de rea??o de 23%. A partir dos resultados constatou-se que a polimeriza?ao in situ foi a metodologia mais adequada para produzir comp?sitos polim?ricos na presen?a de PAni, visto que os comp?sitos apresentaram boa dispers?o da carga induzindo ? forma??o da rede condutiva. A presen?a de grafite no material h?brido melhora a condutividade el?trica dos comp?sitos e a qualidade das nanofibras ? afetada positivamente. A metodologia da mistura por fus?o n?o foi eficiente para dispersar as nanofibras de Pani na matriz de PE.

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43

Oliveira, Marco Aurélio Vinchi. "Desenvolvimento de um sistema de rotofiação para obtenção e investigação da formação de matrizes nanofibrosas poliméricas." reponame:Repositório Institucional da UFABC, 2017.

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44

Ferrand, Alice. "Développement de biomatériaux nanofibreux/microporeux actifs pour la régénération osseuse." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAE030.

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Les nanotechnologies sont en train de révolutionner le domaine biomédical et plus particulièrement l’ingénierie tissulaire. Elles permettent aujourd’hui, non seulement de réparer mais aussi de régénérer les tissus. Cette nanomédecine régénérative est particulièrement adaptée pour répondre aux besoins importants liés aux maladies dégénératives, au vieillissement et aux traumatismes.Mon travail de thèse s’inscrit dans ce contexte et concerne l’élaboration de biomatériaux nanofibreux et microporeux actifs pour la régénération osseuse. Notre objectif essentiel est de réaliser un implant biodégradable nanostructuré permettant d’accélérer la réparation du tissu osseux. Notre stratégie innovante repose non seulement sur la mise en oeuvre de membranes par électrospinning mais aussi sur leur fonctionnalisation par des facteurs de croissance. Cette fonctionnalisation originale a consisté à enrober ces principes actifs dans des nanoréservoirs en utilisant la technique multicouche de polyélectrolytes. Des membranes de polycaprolactone (PCL) nanofibreuses et microporeuses ont été obtenues par électrospinning puis les fibres ont été enrobées de réservoirs contenant le facteur ostéoinducteur, la protéine morphogénique osseuse 2 (BMP-2). L’induction osseuse engendrée par ces réservoirs actifs a été mise en évidence in vitro après culture d’ostéoblastes humains primaires. Des expérimentations in vivo chez la souris ont permis de confirmer l’accélération de la régénération osseuse grâce à ces nanoréservoirs.Cette même stratégie a été validée in vivo, chez la souris, en utilisant des membranes de collagène d’origine animal commerciales utilisées en clinique. L’activité de ces membranes fonctionnalisées par des nanoréservoirs de BMP-2 est en cours d’analyse dans le cadre de tests précliniques pour une application maxillofaciale et parodontale Nanobiotechnology enables the emergence of entirely new classes of bioactive devices intended for targeted intracellular delivery for more efficiency and less toxicities. Tissue engineering is an interdisciplinary field that has attempted to implement a variety of processing methods for synthetic and natural polymers to fabricate tissue and organ regeneration scaffolds.We report here the first demonstration of bone regeneration by using a strategy based on a synthetic nanostructured membrane. This electrospun membrane is manufactured by using a FDA approved polymer, PCL, (polycaprolactone), and functionalized with nanoreservoirs of a growth factor (BMP-2). Our expected outcomes are the development of clinical applications in the field of tissue engineering and nanomedecine and particularly in bone regeneration.We propose the development of smart nanostructured active implants for regenerative medicine. Our strategycombines a synthetic biodegradable electrospun nanofibrous membrane based on PCL and a bioactive growth factor (BMP-2) entrapped into polymer nanoreservoirs built atop the nanofibers according to the layer-by-layer technology. In this study, by using primary osteoblasts, we have shown the capacity of these sophisticated implants to promote and accelerate not only in vitro bone induction; but also, in vivo, bone formation (mouse model).We have also validated our strategy, in vivo (mouse model), by using an already used in the clinic collagen membrane (animal origin) to accelerate bone regeneration. This unique strategy is used to entrap, protect and stabilize the therapeutic agent into polymer coating acting as nanoreservoirs enrobing fibers of membranes

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Valente, Cristhiane Alvim. "S?ntese de nanofibras de polipirrol para potencial aplica??o em conduto biodegrad?vel para regenera??o nervosa." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2014. http://tede2.pucrs.br/tede2/handle/tede/3268.

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Made available in DSpace on 2015-04-14T13:59:10Z (GMT). No. of bitstreams: 1 462029.pdf: 6506501 bytes, checksum: ac4fdb8832287abddfd8e14f596d52a1 (MD5) Previous issue date: 2014-03-28 Injury of peripheral nerves of accidents at work or home are common carriers and scallfolds of biodegradable polymers with temporary structural function to assist in the regeneration of damaged living tissue are being explored. Conducting polymers such as polypyrrole (PPy), have also been explored because of biocompatibility to various cell types and ease of synthesis. Artificial Nerve Guidance Conduits with multifunctional growth factors (GF) have been studied to improve the regeneration of injured peripheral nerves. The main objective is to prepare polymer composites of poly (lactic - co - glycolic acid) - (PLGA) with PPy nanofibers able to act as a conduit in peripheral nerve regeneration. PPy nanofibers were synthesized via chemical oxidative polymerization with different dopants. Films PLGA / nanofiber PPy / tacrolimus (FK506) were prepared by sandwich solvent casting method. The PPy nanofibers were characterized by FTIR, SEM, electrical impedance spectroscopy and TGA. In vitro degradation of PLGA/PPy composite films was also evaluated. PPy nanofibers of electrically condutive 8.10-4 S / cm were obtained with dopant p-toluenesulfonic acid (PTSA) in the ratio [dop]: [Py] = 4 and 0 ? C. Films PLGA / PPy-nanofibers exhibit irregular surface morphology with voids that can serve as framewoks for cell growth guided. The degradation of PLGA / PPy films did not alter the pH of the buffer solution, an increase of thickness and mass loss was in the range of 7-21% until 28 days of degradation reviews. The addition of nanofibers favored the process of mass loss of about 4% for the PLGA / PPy thicker (≥ 0.6g of PLGA) films and 6% for thinner films (0.2 g PLGA) until 28 days degradation. Les?es dos nervos perif?ricos por acidentes de trabalho ou dom?stico s?o comuns e suportes de pol?meros biodegrad?veis com fun??o estrutural tempor?ria para auxiliarem na regenera??o de tecidos vivos lesados v?m sendo explorados. Pol?meros condutores, como o polipirrol (PPy), tamb?m t?m sido investigados devido facilidade de s?ntese e biocompatibilidade.Condutos Artificiais de Orienta??o Neural multifuncional com fatores de crescimento (FC) v?m sendo estudados para aperfei?oar a regenera??o de feridas em nervos perif?ricos. O objetivo principal deste trabalho ? preparar comp?sitos polim?ricos de poli (?cido l?ctico-co-?cido glic?lico) - (PLGA) com nanofibras de PPy capazes de atuarem como conduto guia na regenera??o de nervos perif?ricos. Nanofibras de PPy foram sintetizadas via polimeriza??o qu?mica oxidativa com diferentes agentes dopantes. Filmes de PLGA/nanofibras PPy/Tacromilus (FK506) foram preparados pelo m?todo do sandu?che por evapora??o do solvente. As nanofibras de PPy foram caracterizadas por FTIR, MEV, espectroscopia de imped?ncia el?trica e TGA. Tamb?m foi avaliada a degrada??o in vitro dos filmes comp?sitos de PLGA/PPy. As nanofibras de PPy com condutividade el?trica de 8.10-4 S/cm foram obtidas com dopante ?cido p-toluenosulf?nico (APTS) na raz?o [dop]:[Py] = 4 e na temperatura de 0?C. Filmes de PLGA/PPy-nanofibras apresentam morfologia superficial irregular fibrosa com poros aleat?rios que podem servir de arcabou?os para o crescimento celular. A degrada??o dos filmes PLGA/PPy n?o alteraram o pH do meio, houve aumento de espessuras e as perdas de massas ficaram na faixa de 7-21 % at? os 28 dias de degrada??o avaliados. A adi??o das nanofibras favoreceu o processo de perda de massa cerca de 4% para os filmes PLGA/PPy mais espessos (≥ 0,6g de PLGA) e 6% para filmes mais finos (0,2 g de PLGA) at? os 28 dias de degrada??o.

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46

D'Anniballe, Riccardo. "Sviluppo e caratterizzazione elettromeccanica di un sensore piezoelettrico nanofibroso per applicazioni in laminati compositi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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Nell’elaborato di tesi magistrale, dal titolo “Sviluppo e caratterizzazione elettromeccanica di un sensore piezoelettrico nanofibroso per applicazioni in laminati compositi”, si è studiata la possibilità di produrre un laminato composito sensorizzato con finalità di Structural Health Monitoring (SHM). Lo studio si è concentrato sui materiali piezoelettrici che risultano particolarmente adatti per finalità di sensing in quanto rispondono ad uno stimolo meccanico con una variazione nel livello di polarizzazione elettrica. Nel lavoro di tesi è descritto il processo produttivo in tutte le sue fasi per la realizzazione di un sensore piezoelettrico che ricalchi la struttura del GLARE (Glass Reinforced Aluminium Laminate). Si tratta di un laminato avanzato per applicazioni aerospaziali strutturali costituito da fogli di alluminio intervallati da strati di pre-preg in fibra di vetro (GFRP-Glass Fiber Reinforced Polymers). La sensorizzazione è stata ottenuta attraverso l’utilizzo di nanofibre piezoelettriche di P(VDF-TrFE), realizzate tramite la tecnica dell’elettrofilatura, e integrate nel laminato, permettendo un monitoraggio costante di tutta la struttura. Obiettivo principale della tesi è stato quello di realizzare un modello matematico-circuitale equivalente del sensore, in grado di prevedere la risposta del sensore per qualsiasi tipologia di forza in ingresso. In particolare, si è sviluppato uno studio sull’effetto della variazione dei parametri circuitali del sistema di acquisizione, che in alcune condizioni permette di rilevare carichi quasi-statici, nonostante il sensore piezoelettrico sia adatto principalmente alla rilevazione di carichi dinamici

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Silva, Pierre Weinmann da. "Obtenção de blendas poliméricas de polipropileno contendo como carga condutiva um nanocompósito formado por nanofibras de polianilina e nanolâminas de grafite." Pontifícia Universidade Católica do Rio Grande do Sul, 2012. http://hdl.handle.net/10923/7441.

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Made available in DSpace on 2015-06-30T02:06:17Z (GMT). No. of bitstreams: 1 000471334-Texto+Completo-0.pdf: 4524191 bytes, checksum: f5450152427bd38ead2e27ad8d28c46b (MD5) Previous issue date: 2012 This work aims to obtain polymer blends containing polypropylene wtih conductive nanofibers formed by polyaniline and graphite nanosheets. Will study the effects of morphology and the electrical and mechanical properties of the resulting polymer. The polyaniline nanofibers are synthesized in the presence of graphite nanosheets using the methodology of rapid mixing. The preparation of blends of polypropylene is made by melting in the inner chamber. The morphology and structure of the nanofillers and blends will be evaluated by scanning electron microscopy (SEM), and Atomic Force Microscopy (AFM). The mechanical properties through tensile testing. The electrical properties by impedance spectroscopy. It was observed that a better dispersion of graphite with polyaniline nanofibers occurs when made in the aqueous solution containing the monomer, aniline in the presence of APS ultrasound for 1 hour. The electrical properties of the synthesized nanocomposite indicate characteristics of semiconductor. The mechanical and thermal properties of the blends did not change significantly with the addition of nanofillers, Higher conductivity values were obtained for high values of frequency, 106 Hz Este trabalho busca a obtenção de blendas poliméricas de polipropileno contendo nanocarga condutiva formada por nanofibras de polianilina (PANI) e nanolâminas de grafite (NLG). Foram estudados os efeitos da nanocarga na morfologia e nas propriedades elétricas e mecânicas do polímero resultante. As nanofibras de PANI foram sintetizadas na presença das nanolâminas de grafite por meio da metodologia da mistura rápida. A preparação das blendas com polipropileno foi realizada por fusão em câmara interna. A morfologia e estrutura da carga nanométrica e das blendas foram avaliadas por meio da Microscopia Eletrônica de Varredura (MEV) e Microscopia Ótica, as propriedades mecânicas por meio de ensaio de tração, as propriedades elétricas por meio da Espectroscopia de Impedância. Foi observado que a melhor dispersão das nanolâminas de grafite junto à polianilina ocorre quando feita na solução aquosa contendo o monômero, anilina, na presença do Persulfato de Amônio (APS) durante 1h de ultrassom. As propriedades elétricas dos nanocompósitos sintetizados indicam características de semicondutor. As propriedades mecânicas e térmicas das blendas não sofreram alterações significativas com a adição da nanocarga. Maiores valores de condutividade foram obtidos para elevados valores de frequência, 106 Hz.

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Wei, Jiayuan. "Preparation and characterization of nanocellulose-based carbon dioxide adsorbing aerogels." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66166.

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CO2 adsorption is considered as a promising strategy to decrease the amount of CO2 in the atmosphere and stop global warming. The goal of this project is to prepare a cellulose-based CO2 adsorbent with a good mass transfer. Monolithic adsorbent based on cellulose nanofibrils (CNF) was fabricated via freeze-casting. 0.1g or 0.5g cellulose acetate (CA) or 0.1g acetylated CNC (aCNC) was dipped into the crosslinked aerogel to increase its CO2 capacity. Acetylation of CNC was confirmed by Fourier transformed infrared spectroscopy (FT-IR) and the degree of substitution was determined to be 1.6 through titration. Scanning electron microscopy (SEM) images showed that monolithic structure was formed through freeze-casting and the structure was maintained after dipping. Compression test suggested that the mechanical properties of the aerogel increased with the increasing amount of dipped CA, while the CO2 capacity of the adsorbent decreased. Furthermore, the outstanding reinforcing effect of aCNC was noticed in the compression test, and the aerogel dipped with aCNC has the highest CO2 capacity with a value of 1.49 mmol/g.

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Oliveira, Felipo de. "S?ntese de nanocomp?sitos de nanofibras de polianilina e polietileno por meio da polimeriza??o IN SITU." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2011. http://tede2.pucrs.br/tede2/handle/tede/3186.

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Made available in DSpace on 2015-04-14T13:58:44Z (GMT). No. of bitstreams: 1 434521.pdf: 3294968 bytes, checksum: fbcc929bfb1cb1c681e58d0bf2918d23 (MD5) Previous issue date: 2011-08-24 O presente trabalho se relaciona com a s?ntese de nanofibras de polianilina, um pol?mero condutor com elevada condutividade el?trica. Foram produzidos nanocomp?sitos com as nanofibras de polianilina como carga condutora e o polietileno como matriz polim?rica. As nanofibras de polianilina com di?metros de fibra entre 50 e 100nm foram obtidas por meio da polimeriza??o interfacial da anilina, e foram caracterizadas por Microscopia Eletr?nica de Varredura (MEV), Microscopia Eletr?nica de Transmiss?o (TEM), Espectroscopia no Ultravioleta (UV-VIS), Espectroscopia no Infravermelho (FTIR) e Calorimetria Explorat?ria Diferencial (DSC). A s?ntese dos nanocomp?sitos polim?ricos foi realizada por meio da polimeriza??o in situ, utilizando o catalisador metaloc?nico diclorobis(ciclopentadienil)zirc?nio IV (Cp2ZrCl2) e MAO (metilaluminooxano) como co-catalisador com diferentes quantidades de carga. Os nanocomp?sitos sintetizados foram caracterizados por MEV, MET, DSC e espectroscopia de imped?ncia el?trica. As micrografias de MEV e MET mostraram que a adi??o das nanofibras de polianilina modificaram a morfologia do polietileno puro resultando em nanocomp?sitos com uma boa dispers?o das nanofibras na matriz polim?rica. Os resultados das propriedades t?rmicas mostraram que a adi??o das nanofibras n?o modificou significamente a temperatura de fus?o e diminuiu a cristalinidade do pol?mero. As nanofibras de polianilina apresentaram elevada condutividade el?trica, 4,33 S/cm-1, e diminuiram a imped?ncia el?trica dos nanocomp?sitos sintetizados

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Ouzzine, Mohammed. "Materiales basados en nanopartículas de TiO2 para la oxidación fotocatalítica de propeno en fase gas a baja concentración." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/40843.

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Dissertations / Theses on the topic 'Nanofibrous materials'

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