Made available in DSpace on 2014-12-17T15:01:32Z (GMT). No. of bitstreams: 1 AndreACP_DISSERT.pdf: 6190808 bytes, checksum: 21a983a9627b562fbe33e41da8ebdfd8 (MD5) Previous issue date: 2013-08-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Polymer particles in the nanometer range are of fundamental interest today, especially when used as carrier systems in the controlled release of drugs, cosmetics and nutraceuticals, as well as in coating materials with magnetic properties. The main objective of the present study concerns the production of submicron particles of poly (methyl methacrylate) (PMMA) by crystallization of a polymer solution by thermally controlled cooling. In this work, PMMA solutions in ethanol and 1-propanol were prepared at different concentrations (1% to 5% by weight) and crystallized at different cooling rates (0.2 to 0.8 ? C / min) controlled linearly. Analysis of particle size distribution (DLS / CILAS) and scanning electron microscopy (SEM) were performed in order to evaluate the morphological characteristics of the produced particles. The results demonstrated that it is possible to obtain submicron polymer perfectly spherical particles using the technique discussed in this study. It was also observed that, depending on the cooling rate and the concentration of the polymer solution, it is possible to achieve high yield in the formation of submicron particles. In addition, preliminary tests were performed in order to verify the ability of this technique to form particulated carrier material with magnetic properties. The results showed that the developed technique can be an interesting alternative to obtain polymer particles with magnetic properties / Part?culas polim?ricas formadas em escala nanom?trica s?o de fundamental interesse atualmente, principalmente quando utilizadas como sistemas carreadores na libera??o controlada de f?rmacos, cosm?ticos e nutrac?uticos, al?m do interesse pr?tico no recobrimento de materiais com propriedades magn?ticas. O principal objetivo do presente estudo diz respeito ? produ??o de part?culas submicrom?tricas de poli(metacrilato de metila) (PMMA) atrav?s da t?cnica de cristaliza??o de uma solu??o polim?rica por resfriamento controlado termicamente, segundo um perfil de taxa linear de resfriamento. Neste trabalho, solu??es de PMMA em etanol e 1-propanol foram preparadas em diferentes concentra??es (1% a 5% em massa) e cristalizadas em diferentes taxas de resfriamento (0,2 a 0,8 ?C/min) controladas linearmente. An?lises de distribui??o de part?culas (DLS/CILAS) e microscopia eletr?nica de varredura (MEV) foram realizadas com o intuito de avaliar as caracter?sticas morfol?gicas das part?culas formadas. Os resultados demonstraram que ? poss?vel obter part?culas polim?ricas submicrom?tricas com morfologia perfeitamente esf?rica utilizando a t?cnica abordada no presente estudo. Observou-se tamb?m que, a depender da taxa de resfriamento e da concentra??o da solu??o polim?rica, ? poss?vel ter alto rendimento na forma??o de part?culas submicrom?tricas. Adicionalmente, foram realizados testes preliminares com o prop?sito de verificar a capacidade desta t?cnica em formar part?culas carreadoras de materiais com propriedades magn?ticas. Os resultados permitiram concluir que a t?cnica estudada pode ser uma alternativa interessante na obten??o de part?culas polim?ricas com propriedades magn?ticas

Le taux de pyrolyse est un paramètre clé du comportement du feu qui, à son tour, contrôle le transfert de chaleur à la surface du combustible. Dans cette étude, un modèle de pyrolyse volumique d’un combustible solide semi–transparent prenant en compte le rayonnement au sein du solide et la régression de l’interface a été couplé au code ISIS. Un algorithme génétique a été utilisé afin de déterminer un jeu optimal de paramètres cinétiques pour la pyrolyse du PMMA à partir d’une expérience de pyrolyse pure sous cône calorimètre en atmosphère normalement oxygénée. Des expériences de pyrolyse avec flamme de plaques carrées ont été réalisées afin de valider les résultats du modèle. L’analyse des résultats obtenus au centre de l’échantillon montre que la vitesse de régression de la surface devient constante en fonction du temps et que la contribution radiative au flux de chaleur total reste pratiquement constante. Les résultats du modèle couplé sont en bon accord avec la littérature et les mesures de cette étude. Néanmoins, le flux de chaleur incident aux bords de l’échantillon est sous-estimé. Une bonne concordance est obtenue entre les hauteurs de flammes prédites et celles déduites de la corrélation de Heskestad. Enfin, pour simuler la pyrolyse du PMMA en atmosphère sous–oxygénée, une chimie à deux étapes avec prise en compte du phénomène d’extinction de la flamme a été utilisée. Les résultats des simulations ont été comparés aux mesures réalisées dans le dispositif CADUCEE pour des fractions volumiques d’oxygène de 18,5% et 19,5%. La baisse du taux de pyrolyse et des températures de flamme avec la fraction volumique d’oxygène est bien reproduite par le modèle. / The pyrolysis rate is a key parameter controlling fire behavior, which in turn drives the heat feedback from the flame to the fuel surface. In the present study an in–depth pyrolysis model of a semi–transparent solid fuel with spectrally–resolved radiation and a moving gas/solid interface was coupled with the CFD code ISIS. A combined genetic algorithm/pyrolysis model was used with Cone Calorimeter data from a pure pyrolysis experiment to estimate a unique set of kinetic parameters for PMMA pyrolysis. In order to validate the coupled model, ambient air flaming experiments were conducted on square slabs of PMMA. From measurements at the center of the slab, it was found that the experimental regression rate becomes almost constant with time, and that the radiative contribution to the total heat flux remains almost constant. Coupled model results show a fairly good agreement with the literature and with current measurements. Nevertheless, the flame heat flux feedback at the edges of the slab is underestimated. Predicted flame heights based on a threshold temperature criterion were found to be close to those deduced from the correlation of Heskestad. Finally, in order to predict the pyrolysis of PMMA under reduced ambient oxygen concentration, a two–step chemical reaction and a flammability diagram for flame extinction was used. Model results are compared with data obtained in the experimental facility CADUCEE for ambient oxygen concentrations of 18.2 and 19.5%. Data show that the total mass loss rate and flame temperature decrease with the oxygen concentration, which is well reproduced by the model.

Les lampes à LEDs s’imposent comme la solution d’avenir pour l’éclairage vert de demain. Malgré des durées de vie annoncées par les constructeurs supérieures à 50 000h, une dérive prématurée de la qualité colorimétrique a été constatée. Ce travail de thèse porte sur l’influence de la photodégradation sur les propriétés optiques de l’un des composants d’un module LED : le composite luminescent qui est associé à la puce semi-conductrice. Des composites luminescents ont été élaborés à partir d’une matrice polymère (EVA ou PMMA) et d’un luminophore inorganique : Y3BO6 : 15% Eu3+. L’évolution des propriétés physico-chimiques et optiques de ces composites a été étudiée sous irradiation dans des conditions accélérées (λ>300 nm) et dans les conditions d’usage (LED UV, λ=365 nm). Le luminophore n’a pas montré d’effet prodégradant sur la photooxydation du polymère. Une perte des propriétés optiques du composite sous l’effet de la photodégradation du polymère a été mise en évidence dans le cas de la matrice EVA. L’évolution des paramètres photométriques de la lumière émise par les composites luminescents au cours du photovieillissement a pu être reliée à l’accumulation des photoproduits dans les films. En revanche, pour les composites PMMA/luminophore, la structure chimique et les propriétés optiques de ces composites ne sont pas modifiés pour des durées de photovieillissement accélérés de 4000h. / Phosphor-converted LEDs are emerging as an eco-friendly solution for the next generation lighting. Despite lifetimes claimed over 50 000h, a loss of the optical properties was noticed. This work focuses on the influence of photodegradation of the materials on the optical properties of the polymer/phosphor composite that is used to encapsulate the semiconductor chip. Luminescent composites were made from a polymer matrix (EVA or PMMA) and an inorganic phosphor: Y3BO6 :15% Eu3+. The evolution of physical, chemical and optical properties of these composites was investigated under irradiation in accelerated conditions (λ>300 nm) and in the use conditions of UV LED (λ=365 nm). The phosphor showed no pro-degrading effect on the photooxidation of the polymer. A loss of the optical properties of the composite was observed and ascribed to the photodegradation of the polymer in the case of the EVA matrix. The evolution of photometric parameters of the emitted light by the luminescent composite during photoaging can be attributed to the accumulation of photoproducts in films. However, for PMMA/phosphor composites, the chemical structure and optical properties of such composites are kept for accelerated photoaging time up to 4000h.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-09T18:16:27Z No. of bitstreams: 1 SANDRO MARTINS DOLGHI - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1349252 bytes, checksum: 7e20e2840dc2a5d2e873cd9b77ed0100 (MD5) / Made available in DSpace on 2018-04-09T18:16:27Z (GMT). No. of bitstreams: 1 SANDRO MARTINS DOLGHI - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1349252 bytes, checksum: 7e20e2840dc2a5d2e873cd9b77ed0100 (MD5) Previous issue date: 2014-12-19 / O culto à beleza está em evidência no Brasil e no mundo, levando ao crescente aumento de técnicas e procedimentos para corrigir defeitos estéticos e minimizar os efeitos do envelhecimento. Diversas substâncias preenchedoras com fluidos de alta viscosidade ou partículas de polímeros em suspensão têm sido utilizadas em larga escala em procedimentos cosméticos e correção de lipodistrofia de pacientes HIV positivos, submetidos à terapia antirretroviral de alta atividade. O uso de polimetilmetacrilato (PMMA) como substância de preenchimento dérmico tem crescido vertiginosamente, assim como o número de reações adversas decorrentes de seu uso. O PMMA vem sendo utilizado, amplamente como matéria prima na fabricação de diversos dispositivos e produtos médicos desde a década de 40, especialmente em função de sua biocompatibilidade, entretanto, ainda há carência de informações e estudos sobre migração e resposta inflamatória das substâncias comercializadas no Brasil para fins de preenchimento dérmico. Este trabalho teve como objetivo avaliar as características físico-químicas de implantes de PMMA comercializados no Brasil para procedimentos de bioplastia, em três apresentações comerciais do produto com diferentes concentrações, visando delimitar limites aceitáveis para fins de registro destes produtos na Agência Nacional de Vigilância Sanitária (Anvisa), com foco na segurança sanitária. As amostras foram caracterizadas por Difração de Raios X (DRX), Espectroscopia na região do infravermelho com transformada de Fourier (FTIR), Microscopia Eletrônica de Varredura (MEV), Espectroscopia por Energia Dispersiva de Raios X (EDS), análise de Calorimetria Exploratória Diferencial (DSC), caracterização por Microscopia Óptica (MO). A técnica de DRX mostrou comportamento semicristalino do PMMA. Com a técnica de FTIR constatou-se os grupos funcionais presentes nos implantes. Por meio das técnicas de MO e MEV foi possível perceber a não homogeneidade em relação ao tamanho das microesferas de PMMA. Pôde-se concluir com os resultados de DSC que o pico endotérmico aumentou de acordo com as variações de concentração do PMMA. A partir dos dados obtidos neste trabalho constata-se que o consumidor está sujeito a riscos, visto que a irregularidade das superfícies e variações nos tamanhos das microesferas pode ocasionar reações adversas, em função da fagocitose das microesferas com tamanho inferior a 20 μm. O crescente uso das técnicas de preenchimento com implantes de PMMA, bem como sua indicação para uso em demais especialidades da medicina, o coloca como material a ser ainda amplamente estudado nas mais diversas aplicações do produto na área médica. / The cult of beauty is in evidence in Brazil and in the world, leading to increasing techniques and procedures to correct aesthetic defects and minimize the effects of aging. Several dermal fillers with high viscosity or polymer particles in suspension fluids have been used in large scale in cosmetic procedures and lipodystrophy correction of HIV-positive patients undergoing HAART activity. The use of polymethylmethacrylate (PMMA) as dermal filler substance has grown dramatically, and the number of adverse reactions arising from its use. PMMA has been used widely as a raw material in manufacturing various medical devices and products since the 40s, especially due to its biocompatibility, however, there is still a lack of information and studies on migration and inflammatory response of substances marketed in Brazil dermal filler purposes. This study aimed to evaluate the physical and chemical characteristics of PMMA implants sold in Brazil for bioplasty procedures in three commercial presentations of the product with different concentrations, in order to delimit acceptable limits for registration of these products at ANVISA, with focus on security health. The samples were characterized by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Spectroscopy Energy Dispersive X-ray (EDS) analysis of Differential Scanning Calorimetry (DSC), characterized by Optical Microscopy (OM). The XRD technique showed semi-crystalline behavior of PMMA. FTIR technique found the functional groups present on the implants. Through OM and SEM techniques we saw the inhomogeneity relative to the size of the PMMA microspheres. One can conclude from the results of the DSC endothermic peak increased in accordance with changes in the concentration of PMMA. From the data obtained in this study it appears that the consumer is subject to risks as uneven surfaces and variations in size of the microspheres can cause adverse reactions, depending on the phagocytosis of microspheres with size less than 20 microns. The increasing use of technical fill with PMMA implants, as well as indications for use in other specialties of medicine, places it as material to be still widely studied in various product applications in the medical field.

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Objectives. Polyamide-12 (PA) is a flexible material suited for denture bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity. Methods. PA specimens (Valplast) of 40 × 10 × 2mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine (n = 10) were measured using the CIE L*a*b color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles, n = 15) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling (n = 10). Results. Tukey’s HSD test (P < 0.05) revealed statistically significant color changes of PA in red wine (ΔE = 4.27 after 12 days, EΔE = 6.90 after 12 days) and coffee (ΔE = 3.93 after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845MPa and not affected by thermocycling (Tukey’s HSD test, P > 0.81). Dry specimens showed significantly decreased elasticity (P < 0.001). Mean surface roughness (PA 0.20 μm, PMMA 0.28 μm) did not change significantly after thermocycling or storage (Mann-Whitney U-test, 0.16 < P < 0.65). Significance. PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.

L'objectif de ces travaux était de mettre au point des vecteurs de diffusion efficaces du thymol pour lutter contre un acarien parasite des abeilles. Le choix s'est porté sur la formation de nano-objets par émulsification spontanée pouvant libérer efficacement du thymol grâce à leur grande surface spécifique. L'émulsification spontanée par « effet Ouzo » a été choisie en raison de (i) la simplicité du procédé nécessaire pour son application par les apiculteurs et de (ii) la possibilité de former une grande diversité de nano-objets. L'émulsification spontanée par effet Ouzo a tout d'abord été étudiée fondamentalement avec un polymère (nanoprécipitation), le polyméthacrylate de méthyle (PMMA), pour s'affranchir des phénomènes déstabilisants typiques des émulsions tels que le mûrissement d'Ostwald et la coalescence. Cette étude a permis de définir clairement les compositions du système PMMA/solvant/eau pour lesquelles la nanoprécipitation du PMMA induit la formation exclusive de nanoparticules de distribution de taille étroite (zone Ouzo) ou la formation de nanoparticules additionnées de macroparticules (zone non-Ouzo), séparées par la limite Ouzo. Deux mécanismes de formation des nanoparticules ont été déduits suivant la sursaturation du PMMA (nucléation et croissance ou nucléation et agrégation). L'influence des stabilisants a montré l'importance de l'adsorption des ions OH- sur la taille des nanoparticules et sur le déplacement de la limite Ouzo alors que seule la stabilité colloïdale est améliorée avec l'ajout de tensioactifs. Cette étude fondamentale a servi de base pour la formation des nanogouttelettes de thymol et des nanocapsules thymol-PVA réticulé et thymol-PMMA par effet Ouzo. Des nanoparticules thymol-PVP ont également été formées par complexation de la poly(N-vinyl-2-pyrrolidone) en milieu aqueux. Ces nano-objets de thymol ont été testés sur des ruches infestées pour déterminer leur efficacité d'éradication de l'acarien Varroa Destructor. / The objective of this work dealt with setting up efficient thymol diffusion vectors to fight against a bee mite, the Varroa Destructor. The formation of nano-objects by spontaneous emulsification was investigated because they provide large specific area to enhance thymol evaporation. Spontaneous emulsification by so-called Ouzo effect was chosen because of (i) the simplicity of the process necessary for the transfer to beekeepers and (ii) the great diversity of nano-objects morphologies which can be designed. Spontaneous emulsification by Ouzo effect was first studied fundamentally with a polymer (nanoprecipitation), the poly(methyl methacrylate) (PMMA), in order to avoid typical emulsion destabilizing phenomena such as Ostwald ripening and coalescence. This study enabled to clearly define the PMMA/solvent/water system compositions for which PMMA nanoprecipitation induces only formation of nanoparticles with a narrow size distribution (Ouzo domain) or formation of microparticles besides nanoparticles (non-Ouzo domain), separated by the Ouzo boundary. Two nanoparticles formation mechanisms were deduced with respect to the supersaturation of PMMA (nucleation and growth or nucleation and aggregation). Stabilizers influence set off the importance of OH- ions adsorption on nanoparticles size and on Ouzo boundary shifting whereas only colloidal stability is improved through surfactant addition. This fundamental study laid down basis for thymol nanodroplets and for thymol-cross linked PVA and thymol-PMMA nanocapsules formation by Ouzo effect. Thymol-PVP nanoparticles were also prepared by poly(N-vinyl-2-pyrrolidone) complexation in aqueous medium. These thymol nano-objects were tested on infested beehives to determine their efficiency to eradicate the Varroa Destructor mite.

Ce travail concerne l'étude du comportement rhéologique de nanocomposites modèles à base de Laponite dans du polyoxyde d'éthylène ou des mélanges polyoxyde d'éthylène avec du polyméthacrylate de méthyle. L'influence des paramètres moléculaires, masse molaire de la matrice et mode de protection des particules sur les propriétés rhéologiques a été étudiée. La meilleure dispersion est obtenue à partir d'une solution, la dilution d'un mélange maître conduisant à des matériaux hétérogènes. Les mélanges POE/PMMA sont compatibles à l'état fondu dans toute la gamme de concentrations mais hétérogènes à température ambiante au-dessus de 30% en poids de particules. En diluant un mélange Laponite/PEO dans le PMMA, nous avons montré que ces domaines se concentrent en particules en dessous de 30% de PEO et qu'une cocontinuité de phases PEO contenant les particules et PMMA essentiellement pur est formée au-dessus de 30% de PEO. La présence des particules diminue fortement la cristallinité. / This study concerns model nanocomposites based on Laponite and polyethylene oxide, alone or blended with polymethylmethacrylate. We studied the influence of the parameters on rheological properties of model PEO/Laponite nanocomposites such as matrix molecular weight, preparation method. The best dispersion state of the particles is obtained from solution. Melt dispersion leads to a low frequency modulus which depends on the length and grafting density of the particles. Heterogeneous materials are obtained from melt dispersion of a master batch. PMMA/PEO blends appear to be homogeneous at room temperature only for PEO concentration less than 30wt%. Laponite particles are concentrated in small domains where most of PEO has been extracted. At higher concentrations of PEO, a continuous phase containing PEO and Laponite above percolation concentration is observed, leading to an elastic modulus at low frequency. The presence of Laponite decreases significantly the crystallinity of PEO.

A importância da pesquisa em eletrônica orgânica, se comparada à microeletrônica convencional baseada principalmente em silício, surge pela presença de inúmeros semicondutores e técnicas de deposição de baixo custo e em grande superfície. Os Transistores de Filmes Finos Orgânicos (OTFTs, do inglês Organic Thin-Film Transistors) são a unidade fundamental em circuitos eletrônicos e, geralmente, apresentam a estrutura de um transistor de efeito de campo. Podem ser fabricados sobre substratos plásticos e oferecem grande número de aplicações como: mostradores, etiquetas de identificação por rádio frequência e eletrônica têxtil. Além disso, há demanda por componentes eletrônicos portáteis e baratos, principalmente como sensores em diagnósticos médicos e veterinários in-situ. A geometria de OTFT mais utilizada em sensores na atualidade é a bottom gate sobre substratos de silício altamente dopado e com óxido de porta inorgânico. Polímeros como poli(3-hexiltiofeno) (P3HT) vêm sendo amplamente utilizados pela comunidade científica, atestando o potencial comercial deste semicondutor em sensores. Neste contexto, esta tese apresenta o desenvolvimento de transistores à base de P3HT como sensores na detecção de analitos em fase vapor. O estudo é composto por uma etapa inicial de caracterização da mobilidade dos portadores de carga por técnicas de transiente de corrente, seguida pela otimização do desempenho de parâmetros elétricos do transistor através de alterações no processamento dos filmes dielétrico e semicondutor. Enfim, conclui-se a investigação através do entendimento dos fatores ligados à degradação do OTFT após exposição à atmosfera e sob estresse elétrico, além do detalhamento da sensibilidade e especificidade do sensor. Sensores de P3HT oferecem enorme potencial de detecção de amônia, cetonas e compostos organoclorados. Outros semicondutores poliméricos são provavelmente necessários para maior especificidade em relação a vapor dágua e álcoois. / Research on organic electronics, compared to conventional silicon-based microelectronics, is necessary as it offers plenty of semiconductors and low-cost deposition techniques that can be performed over wide surfaces. Organic Thin-Film Transistors (OTFTs) are the fundamental unity in electronic circuits and, usually, display the metal insulator semiconductor field-effect transistor (MISFET) structure. OTFTs can be processed over cheap plastic substrates and integrate a high number of applications as: flexible displays, radio frequency identification tags, textile electronics and sensors (e.g. chemical and biological compounds). Nowadays, consumers demand portable and low-cost electronic devices, mainly as sensors for in-situ medical and veterinarian diagnosis. The most widely used OTFT structure in sensing is the bottom-gate/bottom-contact FET over highly-doped silicon substrates and inorganic dielectrics. Polymers as poly(3-hexylthiophene) (P3HT) have found increasing acceptance by the scientific community, attesting their potential as semiconductors for commercial applications. In this context, the thesis lies in the development of organic transistors based in P3HT polymer for the detection of vapor-phase compounds. This study begins with transistor performance optimization through changes in dielectric and semiconductor processing. Thin-film thickness and P3HT cast solution drying time are the main studied parameters. It involves also the understanding of device performance degradation when exposed to atmosphere and under bias stress, before finally mapping sensitivity and specificity against gaseous analytes. P3HT-based sensors are potentially interesting for ammonia, ketones and organochlorides detection. Other polymeric semiconductors may be necessary to increase specificity against water steam and alcohol analytes.