Nous décrivons dans ce travail l’élaboration de latex nanocomposites à base d’oxyde de cérium en vue d’applications dans le domaine des revêtements. Deux procédés originaux ont été développés afin de contrôler la morphologie des particules. Dans un premier temps, nous avons tiré parti de la forte densité de charges des nanoparticules d’oxyde de cérium pour stabiliser des particules de latex obtenues par polymérisation en émulsion ou en miniémulsion « de Pickering ». Dans les deux cas, la réaction est conduite en présence des particules inorganiques et d’un agent complexant à caractère acide, l’acide méthacrylique, en l’absence de tout tensioactif. Des particules de latex, décorées en surface par les nanoparticules d’oxyde de cérium ont été ainsi synthétisées. Par la suite, une stratégie qui consiste à utiliser des chaînes de polymères hydrophiles, réactivables (macro-agent RAFT) et préalablement adsorbées à la surface des nanoparticules d’oxyde de cérium a été envisagée. Ces chaînes polymères comportant à la fois des fonctions carboxyliques et un groupe trithiocarbonate terminal sont capables de stabiliser la suspension colloïdale des nanoparticules et de réamorcer la polymérisation en mode semi-continu permettant ainsi l’encapsulation de l’oxyde de cérium. Une optimisation visant à utiliser un procédé batch a également été évaluée. Quelle que soit la stratégie employée, une attention toute particulière a été portée à la stabilité colloïdale du milieu ainsi qu’à la cinétique de la réaction. La morphologie des particules composites a été caractérisée par MET et cryo-MET et reliée aux conditions de modification de surface et de polymérisation / This work describes the elaboration of nanocomposite latexes containing cerium dioxide nanoparticles for coating applications. Two original approaches have been developed to control the particle morphology. First, we took advantage of the high charge density of cerium dioxide nanoparticles to stabilize latex particles obtained via emulsion or “Pickering” miniemulsion polymerization. In both cases the reaction was conducted in the presence of the inorganic particles and methacrylic acid as a complexing agent, in the absence of any added surfactant. Armored latex particles covered with cerium dioxide nanoparticules were obtained by this method. Subsequently, another approach based on the use of living hydrophilic polymer chains (macroRAFT agents) previously adsorbed on the surface of the cerium dioxide nanoparticles was considered. These copolymers both containing carboxylic acid groups and carrying a thiocarbonylthio end group led to stable aqueous dispersion of the nanoparticles and could chain extend to form an encapsulating polymer shell under starved feed emulsion polymerization conditions. An optimization using a batch process was also evaluated. For both approaches, particular attention was paid to the colloidal stability of the medium and to the kinetics of the reaction. The morphology of the nanocomposite latex particles was characterized by TEM and cryo-TEM and correlated with the surface modification and the experimental conditions

Les recherches présentées dans ce mémoire s'intéressent à la désorption du tensioactif dans les films de latex en cours de séchage. Les travaux concernent d'une part l'élaboration d'un système expérimental modélisant le rapprochement de deux particules de latex recouvertes de tensioactif pour accéder aux paramètres influençant la désorption, et d'autre part l'étude de ce phénomène directement sur un latex. Un protocole pertinent de fabrication d'un film polymère mince déposé sur du mica, de faible rugosité, et résistant à une immersion prolongée dans un milieu aqueux a été obtenu. L'adsorption d'un tensioactif anionique, le dodécyl sulfate de sodium (SDS) sur un film polymère de poly (méthacrylate d'éthyle) (PEMA) est investiguée par microscopie à force atomique et indique la présence d'agrégats de surface dont la densité croit lorsque la concentration en tensioactif dans la solution dépasse la concentration micellaire critique (CMC). Le profil des interactions s'exerçant entre deux surfaces de polymère immergées en solutions aqueuses de tensioactif en fonction de la séparation entre les interfaces est obtenu par la technique de mesure des forces de surface (surface force apparatus, SFA), et permet de répondre à la question de l'occurrence ou non de la désorption du tensioactif (SDS) lorsque le milieu aqueux intermédiaire séparant les interfaces de PEMA est réduit jusqu'au contact physique, comme dans le mécanisme de séchage lorsque les colloïdes de latex se rapprochent au fur et à mesure que l'eau disparaît. L'étude de la désorption du tensioactif dans un système réel, à savoir lors du séchage d'un film de latex, est menée par mesures d'anisotropie de fluorescence et mesures par résonateur de torsion et montre la simultanéité entre la perte de mobilité de la sonde fluorescente hydrophile et l'évaporation de l'eau, augurant d'un comportement analogue pour le tensioactif.

Made available in DSpace on 2014-12-17T14:07:20Z (GMT). No. of bitstreams: 1 EricaNMGP.pdf: 6433422 bytes, checksum: bf4255596957765009ee816c080d6b9a (MD5) Previous issue date: 2007-04-23 / The development of activities in the oil and gas sector has been promoting the search for materials more adequate to oilwell cementing operation. In the state of Rio Grande do Norte, the cement sheath integrity tend to fail during steam injection operation which is necessary to increase oil recovery in reservoir with heavy oil. Geopolymer is a material that can be used as alternative cement. It has been used in manufacturing of fireproof compounds, construction of structures and for controlling of toxic or radioactive waste. Latex is widely used in Portland cement slurries and its characteristic is the increase of compressive strength of cement slurries. Sodium Tetraborate is used in dental cement as a retarder. The addition of this additive aim to improve the geopolymeric slurries properties for oilwell cementing operation. The slurries studied are constituted of metakaolinite, potassium silicate, potassium hydroxide, non-ionic latex and sodium tetraborate. The properties evaluated were: viscosity, compressive strength, thickening time, density, fluid loss control, at ambient temperature (27 ?C) and at cement specification temperature. The tests were carried out in accordance to the practical recommendations of the norm API RP 10B. The slurries with sodium tetraborate did not change either their rheological properties or their mechanical properties or their density in relation the slurry with no additive. The increase of the concentration of sodium tetraborate increased the water loss at both temperatures studied. The best result obtained with the addition of sodium tetraborate was thickening time, which was tripled. The addition of latex in the slurries studied diminished their rheological properties and their density, however, at ambient temperature, it increased their compressive strength and it functioned as an accelerator. The increase of latex concentration increased the presence of water and then diminished the density of the slurries and increased the water loss. From the results obtained, it was concluded that sodium tetraborate and non-ionic latex are promising additives for geopolymer slurries to be used in oilwell cementing operation / O desenvolvimento das atividades do setor petr?leo e g?s tem promovido a busca de materiais mais adequados para cimenta??o de po?os de petr?leo. No estado do RN, a integridade da bainha cimentante tende a ser prejudicada durante a inje??o de vapor, procedimento necess?rio para aumentar a recupera??o do petr?leo em reservat?rios com ?leo de alta viscosidade. O geopol?mero ? um material que pode ser utilizado como cimento alternativo, uma vez que vem sendo empregado na produ??o de componentes resistentes ao fogo, na constru??o de estruturas, e para o controle de res?duos t?xicos ou radioativos. O l?tex ? extensamente usado em pastas de cimento Portland e tem como caracter?stica o aumento significativo da resist?ncia ? compress?o das pastas. O tetraborato de s?dio ? usado em cimentos odontol?gicos como retardador de pega em resinas. A adi??o deste aditivo tem a finalidade de melhorar a propriedades das pastas geopolim?ricas para cimenta??o de po?os de petr?leo. As pastas estudadas s?o constitu?das de metacaulim, silicato de pot?ssio, hidr?xido de pot?ssio, l?tex n?o i?nico e tetraborato de s?dio. As propriedades avaliadas foram: viscosidade, resist?ncia mec?nica, tempo de espessamento, densidade e controle de filtrado, na temperatura ambiente (27?C) e de especifica??o de cimento. Os testes foram realizados seguindo as recomenda??es pr?ticas da norma API RP 10B. As pastas aditivadas com tetraborato de s?dio n?o modificaram as propriedades reol?gicas em rela??o a pasta sem aditivo, assim como n?o modificaram as propriedades mec?nicas e a densidade das pastas. O aumento da concentra??o de tetraborato de s?dio aumentou o volume de filtrado das pastas nas duas temperaturas estudadas. A propriedade que o tetraborato de s?dio obteve o melhor desempenho foi em rela??o ao tempo de pega, onde a adi??o do aditivo conseguiu triplicar o tempo de espessamento das pastas. Com rela??o ?s pastas aditivadas com l?tex observou-se que a adi??o desse aditivo diminuiu as propriedades reol?gicas e a densidade do sistema. Na temperatura ambiente, o aditivo funcionou como acelerador de pega e aumentou a resist?ncia mec?nica das pastas. A presen?a de ?gua reduziu a densidade das pastas e aumentou o volume de filtrado a medida que aumentou a concentra??o do aditivo. A partir dos resultados obtidos concluiu-se que o tetraborato de s?dio e o l?tex n?o i?nico s?o aditivos promissores para pastas geopolim?ricas para cimenta??o de po?os de petr?leo

Globalmente ocorrem cerca de 800.000 mortes de crianças menores de cinco anos associadas à diarreia, principalmente na África subsaariana, sul da Ásia e América Latina. Dentre os patógenos causadores de diarreia, Escherichia coli diarreiogênica (DEC) é o agente etiológico bacteriano mais comum, incluindo E. coli enteropatogênica (EPEC) e E. coli produtora da toxina de Shiga e seu subgrupo enterohemorrágica (STEC/EHEC). Os dados epidemiológicos indicam a importância do diagnóstico precoce e sua realização em locais com pouca infraestrutura. Desta forma o objetivo deste trabalho foi o desenvolvimento de um teste rápido, sensível e específico para o diagnóstico de EPEC e STEC/EHEC. Primeiramente, foram definidas diferentes condições do cultivo bacteriano: Dulbecco\'s modified Eagle\'s (DMEM), DMEM contendo 1% de triptona e DMEM pré-condicionado para o cultivo dos isolados de EPEC/EHEC e avaliação da produção/secreção das proteínas secretadas EspA e EspB, utilizando anticorpos monoclonais (MAb) e policlonais (PAb) anti-EspA ou anti-EspB por ELISA indireto. Para a avaliação da liberação das toxinas de Shiga para o sobrenadante do cultivo bacteriano de STEC/EHEC, foram testados diferentes condições de tratamento, o cultivo bacteriano foi tratado com Triton X-100 e o sedimento foi tratado com tampão de lise B-PER utilizando MAb e PAb anti-Stx1 ou anti-Stx2 por ELISA de captura. Subsequentemente, foi desenvolvido e avaliado o teste de aglutinação em látex para a detecção de EspB em isolados de EPEC/EHEC, e Stx1 e Stx2 em isolados de STEC/EHEC. EspB foi definida como biomarcador, o MAb anti-EspB como ferramenta para o diagnóstico de EPEC/EHEC, e a condição ideal para a produção/secreção de EspB foi o cultivo em DMEM. Para o diagnóstico de STEC/EHEC a condição ideal para liberação das toxinas Stx foi o tratamento do cultivo com Triton X-100. Tanto o ELISA, como a aglutinação em látex apresentaram sensibilidades e especificidades exigidas para testes diagnósticos de doenças negligenciadas em países em desenvolvimento e os testes de aglutinação em látex para a detecção destes patógenos foram precisos, rápidos e fáceis de executar, sendo portanto promissores para a utilização em laboratórios com mínima infraestrutura. / There are 800,000 deaths associated with diarrhea worldwide in children under five, and these are mainly in sub-Saharan Africa, Southeast Asia and Latin America. Among the causative pathogens of diarrhea, diarrheagenic Escherichia coli (DEC) is the most common bacterial etiological agent, including enteropathogenic E. coli (EPEC) and Shiga toxin-producing E. coli and its subgroup enterohemorrhagic E. coli (STEC/EHEC). Epidemiological data indicate the importance of early diagnosis and its realization in places with limited resources. Therefore, the objective of this work was to develop a rapid, sensitive and specific test for the diagnosis of EPEC and STEC/EHEC. First, different bacterial growth conditions were evaluated: Dulbecco\'s modified Eagle\'s medium (DMEM) or DMEM containing 1% tryptone, and DMEM pre-conditioned with EPEC/EHEC isolates. The production/secretion of the secreted proteins EspA and EspB was determined by indirect ELISA utilizing anti-EspA or anti-EspB monoclonal (MAb) and polyclonal (PAb) antibodies. Different treatments were tested for their effect on the release of Shiga toxins into the medium of STEC/EHEC bacterial cultures. The bacterial culture supernatant was treated with Triton X-100, and the sediment was treated with B-PER lysis buffer. The toxins release was determined by capture ELISA using anti-Stx1 or anti-Stx2 MAb and PAb. Subsequently, a latex agglutination test was developed and evaluated for the detection of EspB in EPEC/EHEC isolates and of Stx1 and Stx2 in STEC/EHEC isolates. EspB was defined as the biomarker and anti-EspB MAb as the tool for the diagnosis of EPEC/EHEC. The ideal conditions for the production/secretion of EspB were cultivation in DMEM. For the diagnosis of STEC/EHEC, the ideal conditions for the release of Stx were Triton X-100 treatment. ELISA as well as latex agglutination showed the sensitivities and specificities required for diagnostic tests of neglected diseases in developing countries. The latex agglutination test for the detection of these pathogens was precise, rapid and easy to perform, thereby being promising for their utilization in laboratories with limited resources.

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This thesis examines the influence of the intensity of pressure strain of structures printed on the value of air permeability. The measurement is carried out using Blower Door Test on six variants using OSB boards as airtightening layers in the building. Part of the research was to verify the suitability of the test chamber and measuring devices for similar purposes and adjustment chamber

Mitteilungen des URZ 2/2002 (Inhalt siehe Schlagwörter)

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This work makes basic analysis of historical and current algorithms for smoke animation. Modern approaches to rendering volumetric data are briefly described. We choose algorithms for implementation on basis of this analysis. These algorithms are described in detail and we make emphasis on their important properties according to dedication of this work. Detailed description of implementation follows along with performance measurement. Conclusion evaluates results of work and proposes possible extensions.