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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Chemorhelogical Modeling Of Amine-Cured Multifunctional Epoxy Resin Systems Used As Matrices In Aerospace Composites

Subramaniam, C 10 1900 (has links)
High performance multifunctional epoxy resin systems are becoming increasingly important as matrix materials for the advanced composites used in aerospace, electronics, automotive and other industries. In a composite based on epoxy resin systems, a three-dimensional network of the matrix is formed around the reinforcing fibre as a result of the chemical reaction between the resin and the curing agent. This chemical process, known as curing, is an important event to he considered in the production of composite components made up of these resin systems. Two process parameters namely viscosity and chemical conversion are of paramount significance in the production of composite materials Curing studies of the resin systems based on these two parameters, would therefore assume great importance in deciding the performance reliability of the end product. The objectives of the present investigation are 1. to study the cure kinetics of three thermoset resin systems, viz., i) epoxy novolac (EPIT)/ diamino diphenyl methane{DDM), ii) trigylcidyl para- ammo phenol (TGPAP)/toluene diamine (TDA) and iii) tetraglycidyl diamino diphenyl methane (TGDDM)/pyridine diamine(PDA) using the cure kinetic models based on chemical conversion (α), Theological conversion (β) and viscosity. 2.to develop a correlation between a and viscosity (η) and modify an existing autocatalytic model based on α, to the viscosity domain and 3.to investigate the cure behaviour of these systems in terms of the TTT cure diagram and its associated models. EPN/DDM, TGPAP/PDA and TGDDM/PDA resin systems were chosen for the studies to represent a range of functionalities, The cure was monitored using differential scanning calorimetry (DSC), fourier transform infrared (FTIR) and dynamic mechanical analysis (DMA) techniques by following the changes in enthalpy, functional groups and rheology, respectively. The kinetic parameters namely, order of reaction and activation energy were estimated from dynamic DSC data using the methods of Freeman-Carroll and Ellerstein using nth rate expression. Barton, Kissinger and Osawa methods were employed to find out the activation energy from the peak/equal conversion at different heating rates. Isothermal DSC data were also analyzed using nth order model and it was observed that the data could be fitted satisfactorily only for higher temperatures The results obtained from the analysis of both dynamic and isothermal DSC data using nth order model clearly indicate that this model is inadequate for describing the cure behavior. The isothermal DSC data was analyzed by the autocatalytic models of Hone and Kamal Good correlation was observed with Hum and Kamal models up to 60-70%, 25% and 45% conversions for EPN/DDM, TGPAP/TDA and TCDDM/PDA systems respectively. However, the parameters m and n in Kamal model were found to be temperature dependent for EPN/DDM and TCPAP/TDA systems. The limited applicability of the autocatalytic models IK attributed to the counter-effect offered by the intra-molecular bonding taking place. The primary amine and epoxy groups conversions obtained from FTIR were analyzed using autocatalytic model and the kinetic parameters were calculated. The reactivity ratio of the primary amine and the secondary amine with epoxy was found to be dependent on temperature in agreement with the recent findings reported m the literature. The existing models that relate the cure kinetics and the rheological changes, are dual Arrhenius nth order model and autocatalytic model The nth order kinetic model was used to evaluate the kinetic parameters using the viscosity data at different cure temperatures under isothermal conditions As the storage modulus, G' is proportional to the chemical cross links and becomes significant only after the g<4 point, it was used to follow the changes in conversion known as rheoconversion after the gel point The rheoconversion was found by normalizing the G' data with G1^, the storage modulus of the fully cured resin It was used to study the cuie kinetics using an autocatalytic model The kinetic parameters such as rate constant, acceptation and retardation parameters were evaluated and that temperature dependence was established. While the existing models relate viscosity and conversion only up to gel point the new proposed model, termed VISCON model takes into account the changes up to vitrification. The relation so developed is used to modify the autocatalytic cure model based on chemical conversion. The parameters appearing in this model were evaluated using Levenberg-Marquardt error minimization algorithm. The kinetic parameters obtained are comparable with the values estimated using the DSC data. All the models cited above represent the microkinetic aspects. The models based on the information of TTT cure diagrams, however, represent the macrokinetic aspects of the cure, as they are based on the cure stages such as gelation and vitrification TTT diagram relates the cure characteristics like cure temperature, cure time, Ta and, indirectly, chemical conversion Hence the ultimate properties of the composite could he predicted and established with the help of the models based on TTT cure diagrams The changes in the storage modulus, G1 and loss modulus, G", were followed to identify the gel and vitrification points of the resin systems at different cure temperatures Gel point and vitrification point were used to generate gelation and vitrification hues in the construction of TTT cure diagrams for EPN/DDM, TGPAP/TDA and TGDDM/PDA resin systems Theoretical TTT diagrams were generated and IBO-T, contours were established using the TTT diagram-based models The cure schedule for the resin systems investigated could be determined from the TTT diagram and the respective rheological data.
132

Polymérisation anionique des époxydes par activation du monomère : monomères renouvelables et polymères fonctionnalisés

Brocas, Anne-Laure 04 December 2011 (has links)
La polymérisation anionique par activation du monomère permet d’accéder à une large gamme de polyéthers en utilisant un système amorçant à base d’un nucléophile associé au triisobutylaluminium. Cette voie a permis d’accéder à des chaînes polyéthers fonctionnalisées par des groupements hydroxyle à chaque extrémité. La (co)polymérisation de l’éther allylglycidique avec d’autres éthers cycliques a été réalisée puis les (co)polymères correspondants ont été post-fonctionnalisés pour introduire en particulier des fonctions cyclo-carbonate destinées à réagir avec des amines pour générer des fonctions hydroxyuréthane et ainsi préparer des matériaux type polyuréthane par une chimie sans isocyanate. Enfin des dérivés du pin, de la famille des acides résiniques, ont été modifiés chimiquement pour élaborer des matériaux de type résine époxyde et polyuréthane sans isocyanate. La polymérisation anionique par activation du monomère a également pu être réalisée sur un monomère époxydé issu de cette ressource. / Monomer-activated anionic polymerization allows the obtention of versatile polyethers using nucleophilic species in the presence of a Lewis acid, i.e. triisobutylaluminium. This method enables the synthesis of α-,ω-plurihydroxytelechelic polyethers. The (co)polymerization of allyl glycidyl ether with various epoxides allowed the preparation of copolyethers with reactive side groups. A cyclo-carbonate functionalization was carried out in order to introduce hydroxyurethane functions by reaction with amines. This reaction allows the preparation of isocyanate-free polyurethane. Finally, resinic acids were modified chemically to prepare epoxy resins and isocyanate-free polyurethanes. A polyether based on epoxidized resinic derivatives was also synthesized by ring-opening anionic polymerization and monomer activation.
133

Analýza elektrických vlastností epoxidových pryskyřic s různými plnivy v teplotní a kmitočtové závislosti / Electrical properties analysis of epoxy resins with different fillers in temperature and frequency dependence

Horák, Luděk January 2018 (has links)
Presented master's thesis is focused on studying electroinsulating epoxy resin-based sealings. It describes the chemical composition, production, properties and measuring methods of basic electric quantities of these materials. The aim of the thesis is to compare several sets of samples of composite epoxy resins with different kinds of micro-ground siliceous sand as a filling. The temperature and frequency dependence of relative permittivity, dissipation factor and inner resistivity are measured for given samples.
134

Dielektrické vlastnosti epoxidových pryskyřic / Dielectric properties of epoxy resins

Matoušová, Klára January 2019 (has links)
This diploma thesis deals with the fundamental properties of epoxide mixtures, as determining of these fundamental properties of epoxide mixtures could in the case of favorable results lead to diminishing the amount of defects in epoxide-embedded instrument transformers. As the influence of effects in the manufacturing process of transformers causing poor quality is very extensit, the biggest emphasis is laid capitally on the influence of the epoxide casting mixture composition. The thesis describes the manufacture technology including used methodics and materials. The compositions of epoxide resins and the mechanisms of their curing. Also, the definitions of fundamental properties of dielectric materials and the description of diagnostic methods used to relative permitivity, dissipation factor and inner resistivity are included. suitable casts of acquired samples were set and dried out within the experimental part, followed by measurement of fundamental electrical properties in temperature and frequency relations. Hereafter a comparison of individual samples and the evaluation of their electrical properties will be carried out.
135

Испитивање биокомпатибилности објеката од полимера произведених адитивном технологијом за примену у области стоматологије / Ispitivanje biokompatibilnosti objekata od polimera proizvedenih aditivnom tehnologijom za primenu u oblasti stomatologije / Testing the biocompatibility of objects from polymers produced by additive manufacturing for use in dentistry

Vuletić Rakić Jelena 14 October 2016 (has links)
<p>Uobičajeni pristup i testiranju biolo&scaron;kog pona&scaron;anja materijala je da se počne sa jednostavnim in vitro testovima baziranim na ćelijskim kulturama. In vitro testovi citotoksičnosti su danas jedan od osnovnih načina za procenu biolo&scaron;kog odgovora na materijal jer su brži, lak&scaron;i za ponavljanje, ocenjivanje i jeftiniji u odnosu na eksperimente koji se izvode na životinjama i ljudima. Koriste se kao neka vrsta skrining testova za procenu biolo&scaron;ke sigurnosti materijala. Za razliku od ćelijskih kultura, istraživanja koja uključuju eksperimentalne životinje pružaju bolji uvid u biokompatibilnost materijala, zbog mogućnosti praćenja kompleksnog imunolo&scaron;kog odgovora živog organizma. Smatraju se neophodnim za ocenu bilo&scaron;kih odgovora na novi materijal, pre nego &scaron;to se on upotrebi na ljudima. Mnogi aspekti biolo&scaron;kog odgovora ne mogu biti reprodukovani in vitro testovima uključujući krvne interakcije, zarastanje rana, reakcije preosetljivosti, karcinogenezu, hroničnu inflamaciju. Eksperimenti na životinjama pružaju informacije o ovim tipovima efekata bez izlaganja ljudi riziku. Cilj ovog istraživanja bio je da se oceni biokompatibilnost objekata od polimera na bazi epoksi smole Accura&reg; ClearVue&trade; (hemijski sastav: 4,4&rsquo;- izopropilidendicikloheksanol, produkti oligomerne reakcije sa 1-hlor-2,3- epoksipropanom(40-65%), sme&scaron;а triaril-sulfonijum soli (50% propilen-karbonata i 50% triaril-sulfonijum heksafluoroantimonatnih soli) (1-10%) i 3-etil-3hidroksimetil-oksetan(10-20%). U oceni citotoksičnosti materijala Accura&reg; ClearVue&trade; kori&scaron;ćeni su agar diguzioni i MTT test. Oba testa rađena sun a ćelijskim kulturama L929 (mi&scaron;iji fibroblasti) i MRC-5 (humani fibroblasti). Ocena biokompatibilnosti testiranog materijala vr&scaron;ena je na osnovu urađenog testa iritacije oralne mukoze na modelu bukalne kesice hrčka, &scaron;to je definisano standardom ISO 10993-10:2010. Biokompatibilnost materijala ispitana je i implantacijom uzoraka u potkožno tkivo dorzuma pacova soja Wistar.</p> / <p>Uobičajeni pristup i testiranju biolo&scaron;kog pona&scaron;anja materijala je da se počne sa jednostavnim in vitro testovima baziranim na ćelijskim kulturama. In vitro testovi citotoksičnosti su danas jedan od osnovnih načina za procenu biolo&scaron;kog odgovora na materijal jer su brži, lak&scaron;i za ponavljanje, ocenjivanje i jeftiniji u odnosu na eksperimente koji se izvode na životinjama i ljudima. Koriste se kao neka vrsta skrining testova za procenu biolo&scaron;ke sigurnosti materijala. Za razliku od ćelijskih kultura, istraživanja koja uključuju eksperimentalne životinje pružaju bolji uvid u biokompatibilnost materijala, zbog mogućnosti praćenja kompleksnog imunolo&scaron;kog odgovora živog organizma. Smatraju se neophodnim za ocenu bilo&scaron;kih odgovora na novi materijal, pre nego &scaron;to se on upotrebi na ljudima. Mnogi aspekti biolo&scaron;kog odgovora ne mogu biti reprodukovani in vitro testovima uključujući krvne interakcije, zarastanje rana, reakcije preosetljivosti, karcinogenezu, hroničnu inflamaciju. Eksperimenti na životinjama pružaju informacije o ovim tipovima efekata bez izlaganja ljudi riziku. Cilj ovog istraživanja bio je da se oceni biokompatibilnost objekata od polimera na bazi epoksi smole Accura&reg; ClearVue&trade; (hemijski sastav: 4,4&rsquo;- izopropilidendicikloheksanol, produkti oligomerne reakcije sa 1-hlor-2,3- epoksipropanom(40-65%), sme&scaron;a triaril-sulfonijum soli (50% propilen-karbonata i 50% triaril-sulfonijum heksafluoroantimonatnih soli) (1-10%) i 3-etil-3hidroksimetil-oksetan(10-20%). U oceni citotoksičnosti materijala Accura&reg; ClearVue&trade; kori&scaron;ćeni su agar diguzioni i MTT test. Oba testa rađena sun a ćelijskim kulturama L929 (mi&scaron;iji fibroblasti) i MRC-5 (humani fibroblasti). Ocena biokompatibilnosti testiranog materijala vr&scaron;ena je na osnovu urađenog testa iritacije oralne mukoze na modelu bukalne kesice hrčka, &scaron;to je definisano standardom ISO 10993-10:2010. Biokompatibilnost materijala ispitana je i implantacijom uzoraka u potkožno tkivo dorzuma pacova soja Wistar.</p> / <p>The usual approach in testing biological behavior of materials is to start with simple in vitro tests based on cell cultures. In vitro cytotoxicity tests are one of the basic methods of assessing the biological response to material because they are faster, cheaper, easier for repeating and evaluating compared to experiments carried out on animals and humans. They are used as a kind of screening test for evaluating the biosafety of materials. Unlike cell culture, studies involving experimental animals provide better insight into the biocompatibility of materials due to the possibility of monitoring the complex immune response of a living organism. They are considered necessary for assessing the biological response to new material before it is used on humans. Many aspects of a biological response cannot be reproduced with in vitro tests, including blood interaction, wound healing, hypersensitivity reactions, carcinogenesis, chronic inflammation. Animal experiments provide information about these types of effects without exposing humans to risk.&nbsp; The aim of this study was to evaluate the biocompatibility of polymer objects on the basis of epoxy resins Accura&reg; ClearVue &trade; (chemical composition: 4.4&#39; Isopropylidenedicyclohexanol, oligomeric reaction products with 1-chloro-2.3-epoxypropane (40-65%), a mixture of triaryl sulfonium salt (50% propylene carbonate and 50% of a triarylsulfonium hexafluoroantimonate salt) (1- 10%) and 3-ethyl-3-hydroxymethyl-oxetane (10-20%). In the assessment of the cytotoxicity of materials Accura&reg; ClearVue &trade; agar diffusion and MTT tests were used. Both tests were conducted on cell cultures L929 (mouse fibroblasts) and MRC-5 (human fibroblasts). An assessment of the biocompatibility of the tested material was done on the basis of an oral mucosa irritation test on a hamster cheek pouch as defined by ISO 10993-10: 2010. The biocompatibility of the material was also tested with the implantation of a samples into the dorsal subcutaneous tissue of a Wistar rats. The subcutaneous implantation test, as one of the most reliable methods for assessing the biocompatibility of dental materials, is defined by ISO 10993-6: 2010. The study was conducted on 30 rats which were sacrificed in groups</p>
136

Técnicas de refuerzo tradicionales y modernas aplicadas a la conservación y restauración de bienes culturales

Peris Gisbert, Silvana 17 January 2022 (has links)
[ES] La investigación realizada forma parte del estudio, mucho más amplio, para la restauración de la Iglesia de los Santos Juanes de Valencia, que tiene por objeto establecer una metodología de reconstrucción para las pinturas murales de la grandioso bóveda que Antonio Palomino pintó entre 1699 y 1701, la cual fue incendiada durante la Guerra Civil. Al realizar un primer análisis sobre diferentes anclajes en la restauración, se han encontrado dos clases de técnicas de anclaje, las denominadas tradicionales y las modernas. Tras este análisis, se ha realizado un trabajo de investigación comparativa entre diversos espacios arquitectónicos, tanto de España como de Europa, concretamente de Italia, que ya habían sido restaurados, para poder identificar los materiales utilizados en sus realizaciones. Con todo este trabajo acabado, se contactó con el Profesor Vicente Amigó Borrás, investigador del laboratorio del Instituto de Tecnología de los Materiales, para estudiar otros materiales más novedosos que pudieran ayudar en nuestra labor. Para realizar el estudio, junto a él y muchos de sus compañeros, se desarrollaron un conjunto de probetas con el fin de elaborar diferentes tipos de laminados compuestos de fibra y matriz, los cuales han soportado los diferentes procesos y análisis para obtener los mejores resultados posibles. Estos análisis han permitido conocer muy a fondo cada material y la diversidad de sus propiedades, estableciendo estudios comparativos que han ayudado a escoger cuál de ellos resultará más apropiado para el trabajo de restauración y dar algunas conclusiones finales sobre ello en el proceso de intervención global en los Santos Juanes. Se puede afirmar que esta Tesis Doctoral demuestra la posible aplicación de materiales compuestos en diferentes bienes culturales, y en especial en la bóveda de la Iglesia de los Santos Juanes de Valencia. / [CA] La investigació realitzada forma part del estudi, molt més ample, realitzat per a la restauració de l'Església dels Sants Joans de València, que té per objectiu establir una metodologia de reconstrucció per a les pintures murals de la grandiosa volta que Antonio Palomino va pintar entre 1699 i 1701, la qual va ser incendiada durant la Guerra Civil. En realitzar una primera anàlisi sobre ancoratges en la restauració, ens hem trobat davant de dues classes de tècniques d'ancoratge, les denominades tradicionals i les modernes. Després d'aquesta anàlisi, s'ha realitzat un treball de recerca comparativa entre diversos espais arquitectònics, tant d'Espanya com d'Europa, concretament d'Italia, que ja havien sigut restaurats, per a poder identificar els materials utilitzats en les seues realitzacions. Amb tot aquest treball finalitzat, es va contactar amb el Profesor Vicente Amigó Borrás, investigador del laboratori de l'Institut de Tecnologia dels Materials, per a estudiar altres materials més nous que pogueren ajudar en la nostra labor. Per realitzar l'estudi, al costat d'ell i molts dels seus companys, es van desenvolupar un conjunt de provetes amb la finalitat d'elaborar diferents tipus de laminatges compostos de fibra i matriu, els quals han suportat els diferents processos i anàlisis per a obtenir els millors resultats possibles. Aquestes anàlisis han permés conéixer molt a fons cada material i la diversitat de les seues propietats, establint estudis comparatius que han ajudat a triar quin d'ells resultarà més apropiat per al treball de restauració i donar les conclusions finals sobre el procés d'intervenció. Es pot afirmar que aquesta Tesi Doctoral demostra la possible aplicació de materials compostos en diferents béns culturals, i especialment en la volta de l'Església dels Sants Joans de València. / [EN] The object of our study was to establish the methodology for the reconstruction of the painted murals of the great vault in the Santos Juanes church of Valencia which were painted by Antonio Palomino between 1699 and 1701 and which were burned during the Civil War. In conducting an initial study of the foundations we find two different types of technique, the traditional and modern. After this analysis a comparative investigation was carried out between the various architectural sites which have been restored, both in Spain and Europe, enabling a study of the materials which have been utilized. Having completed this work we were put in contact with Professor Vicente Amigo, Laboratory investigator of the Institute of Engineering of Technological Materials, to study alternative more modern materials, which could be put to use in our work. Finishing the study alongside him and his many colleagues, a series of tests have been carried out to develop different types of fibre and matrix laminate combinations, which have undergone a variety of analytical processes to obtain the best possible results. These analyses have enabled a closer and deeper understanding of each material and their individual properties, providing a comparative study to assist the selection of the most appropriate for our needs and giving final results closest to the procedure. It can be confirmed that this Doctorate Thesis demonstrates the possible usage of compounded materials in different cultural properties, especially in the vault of the Santos Juanes church of Valencia. / Peris Gisbert, S. (2021). Técnicas de refuerzo tradicionales y modernas aplicadas a la conservación y restauración de bienes culturales [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180014 / TESIS
137

Fabricación y caracterización de materiales compuestos de alto rendimiento medioambiental derivados de resinas ecológicas y refuerzos de fibras naturales y estructuras híbridas

Lascano Aimacaña, Diego Sebastián 06 September 2022 (has links)
Tesis por compendio / [ES] Es evidente cómo el aumento de la concienciación medioambiental respecto al uso de materiales poliméricos de origen petroquímico o plásticos de un único uso ha cambiado por completo el panorama de los materiales poliméricos, desde el punto de vista de su concepción o de su uso. Durante el desarrollo de esta tesis doctoral se ha abarcado varias alternativas con el fin de obtener materiales nuevos, que no tengan solo un bajo impacto ambiental, sino también que posean propiedades competitivas al compararlos con materiales convencionales, además de que su elaboración no conlleve un cambio drástico con respecto a las tecnologías existentes en la actualidad. Es por eso por lo que el objetivo principal de esta tesis doctoral se centra en el desarrollo y caracterización de nuevos materiales con un alto rendimiento medioambiental a partir de matrices termoplásticas como el poli(ácido láctico) (PLA) y matrices termoestables como resinas epoxi con un contenido parcial o total de origen natural. Además del uso de rellenos y fibras de origen natural. / [CA] És evident com l'augment de la conscienciació mediambiental respecte a l'ús de materials polimèrics d'origen petroquímic o plàstics d'un únic ús ha canviat per complet el panorama dels materials polimèrics, des del punt de vista de la seua concepció o del seu ús. Durant el desenvolupament d'aquesta tesi doctoral s'han tingut en compte diverses alternatives amb la finalitat d'obtindre materials nous, que no tinguen només un baix impacte ambiental, sinó també que posseïsquen propietats competitives en comparar-los amb materials convencionals, a més de que la seua elaboració no comporte un canvi dràstic respecte a les tecnologies existents en l'actualitat. És per això, per la qual cosa l'objectiu principal d'aquesta tesi doctoral se centra en el desenvolupament i caracterització de nous materials amb un alt rendiment mediambiental a partir de matrius termoplàstiques com el àcid polilàctic (PLA) i matrius termoestables com a resines epoxi amb un contingut parcial o total d'origen natural. A més de l'ús de reforços i fibres d'origen natural. / [EN] It is remarkable how the increase in environmental awareness regarding the use of polymeric materials of petrochemical origin or single-use plastics has completely changed the scenario of polymeric materials development and use. This doctoral thesis has proposed several alternatives in order to obtain new materials with low environmental impact and competitive properties to conventional materials. In addition to the fact that their elaboration does not entail a drastic change respect to existing technologies. Therefore, the main objective of this doctoral thesis focuses on developing and characterizing new materials with a high environmental performance from thermoplastic matrices such as poly(lactic acid) (PLA) and thermosetting matrices such as epoxy resins with a partial or total content of natural origin. In addition to the use of fillers and fibers of natural origin. / This research work was funded by the Spanish Ministry of Science, Innovation and Universities (MICIU) project numbers RTI2018-097249-B-C21 and MAT2017-84909-C2-2-R. D.L. thanks Universitat Politècnica de València (UPV) for the grant received through the PAID-01-18 program. / Lascano Aimacaña, DS. (2022). Fabricación y caracterización de materiales compuestos de alto rendimiento medioambiental derivados de resinas ecológicas y refuerzos de fibras naturales y estructuras híbridas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/185886 / TESIS / Compendio

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