The liquid argon target of the DEAP-3600 dark matter detector is contained by an extremely radiopure acrylic vessel. Alpha decays from the inner surface of the acrylic vessel are a source of background. If a fraction of the alpha energy is observed, or if the recoiling nucleus from the alpha decay is observed, the event will not be separated from a dark matter candidate event. In addition to the low level of inherent contamination from uranium and thorium, the Pb-210 from Rn-222 diffusion during manufacturing must be measured. The limit for the DEAP-3600 acrylic vessel is 1.1 × 10^−20 g/g Pb-210. By vaporizing a large quantity of acrylic and counting the concentrated residue with an ultralow background HPGe well detector and a low background alpha spectrometer, the bulk acrylic was found to have an upper limit of 10^−19 g/g Pb-210. The design, installation, commissioning, operation, and analysis for various aspects of the acrylic assay are described. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-01-14 19:27:47.533

Luminescent molecules and polymers are active component in light-emitting diodes; however, the aggregation and excimer formation in concentrated solution or in the solid film states had limited their applications. Therefore, this study used poly(methyl methacrylate) (PMMA) as separator to prevent the formations of aggregate and excimer and to enhance quantum efficiency. Basically, two systems are involved: (1) Inorganic phosphorescent irdium complex PMMA was doped with inorganic iridium complex IrQB by using THF as solvent. IrQB/PMMA films prepared from dilute solutions exhibit two emissions centered at 560 and 640 nm, respectively; in contrast, only 640-nm emission was observed for films from concentrated solutions. Experimentally, these two bands showed variations on the emission intensity with increasing temperature. Aggregation of IrQB is suggested to be responsible for the 560-nm emission. Chain conformation of PMMA in the solution state strongly affects the incorporated IrQBs and their emission properties. (2) Polybenzoxazines Polybenzoxazines with the built-in fluorenscent fluorine moiety are linear in nature; however, the inherent hydrogen-bond (H-bond) interactions in polybenzoxazines decrease the inter-chain distance and cause the chain aggregation. With the added PMMAs, new H-bonding from the carbonyl groups in PMMA and the hydroxyl groups in polybenzoxazine enhances the mutual miscibility between these two components and decreases the possibility of aggregate formation in polybenzoxazines. Quantum efficiency is therefore promoted by this approach.

In this paper, we discuss the effect of the hydrogen-bonding on the photoluminescent(PL) properties of 1-pyrenecarboxylic acid (PCA)/ poly(methyl methacrylate) (PMMA). Isolated fluorophore can be obtained when PCA molecules were blended and septrated by PMMA, i. e. excimer emission can be more efficiently prevented. With the use of non-solvent, toluene, in the preparation step, excimer emission of PCA can be more effeiciently prevented as compared to the good solvent, tetrahydrofuran(THF). With a high PMMA/PCA ratio of 1000/1, emission spectra show no sign of excimer formation. Intermolecular hydrogen bonding between PMMA and PCA helps to prevent the excimer formation. Solvents used in the preparative state play important role on the final PL properties of the solid film. In the blend, partial carbonyl groups in PMMA band with carboxylic acid group in PCA, this causes the appearance of a stretching band at 1718 cm-1 in infrared spectroscopy. The hydrogen-bond interactions help to the prevention of excimer formation in the PMMA/PCA blending systems.

Les polymères synthétiques sont largement utilisés aujourd’hui comme implants prothétiques. Malheureusement, ces implants sont invisibles en imagerie par résonance magnétique IRM. La visualisation de ces implants est une nécessité afin d'obtenir des informations concernant leur fixation dans le corps et leur situation post-opératoire.Un des défis est alors de fixer un agent de contraste sur l'implant médical. Pour cet objectif, un premier polymère va être fonctionnalisé avec un agent de contraste de manière covalente, puis on le dépose par enduction sur la surface de la prothèse. Les polymères seront fonctionnalisés par polymérisation radicalaire et par chimie "click". Dans une première étape, le poly(méthacrylate de méthyle-co-méthacrylate de propargyle) avec un faible rapport molaire en méthacrylate de propargyle (F <10%) est préparé par copolymérisation radicalaire du méthacrylate de méthyle et du méthacrylate de propargyle. Dans une deuxième étape, l'agent de contraste sera greffé avec par réaction de chimie « click » sur le poly(méthacrylate de méthyle) porteur de fonctions propargyles (PMMA-co-PMA). Sur ce squelette polymérique, un nouveau agent de contraste à base de gadolinium sera greffé. Le polymère obtenu sera déposé sur une maille de polypropylene commercial par la technique de l'aérographie et la maille sera évaluée pour l'IRM visualisation sur un7T instrument. Des tests de cytotoxicité et de cytocompatibilité seront effectuées pour évaluer l'utilisation de cet agent de contraste dans des applications biomédicales.En même temps, les techniques d'imagerie de fluorescence gagnent aussi en popularité . Pour cela, le même polymère synthétisé (PMMA–co-PMA) sera fonctionnalisé avec différents précurseurs fluorescents: anthracène , fluorescéine, complexe d’europium. / Synthetic polymers are widely used nowadays as prosthetic implants. Unfortunately, these implants are invsisble by magnetic resonance imaging (MRI). The visualization of these implants is a necessity in order to gain information concerning their fixation in the body and post-operation fate. One of the challenges is then to fix a contrast agent on the implant. Thus the objective is to develop novel strategies for the long-term visualization of prosthetic implants by MRI. For this goal, a polymer will first be functionalized with a contrast agent in a covalent way, and then it will be deposited by coating on the surface of the prosthesis. Polymers will be functionalized by free radical polymerization followed by “click chemistry. In a first step, poly(methyl methacrylate-co-propargyl methacrylate) with low molar ratio in propargyl methacrylate (F< 10 %) will be prepared by free radical copolymerization of methyl methacrylate with propargyl methacrylate. In a second step, a novel gadolinium based contrast agent will be grafted by click chemistry onto the propargylated poly(methyl methacrylate) (PMMA-co-PMA) polymer. The obtained polymeric contrast agent will be spread on a commercial polypropylene mesh by the airbrushing technique and the mesh will be assessed for MRI visualization on a 7T instrument. Cytocompatibility and cytotoxicity tests will be performed to evaluate the use of this contrast agent in biomedical applications.At the same time, fluorescence imaging techniques are also gaining popularity. For this, the same synthesized polymer (PMMA-co-PMA) will be attached to different fluorescent precursors: anthracene, fluoresceine, and europium complex.

As propriedades de rugosidade superficial e microdureza são reconhecidas como propriedades muito relevantes no que concerne ao tratamento com prótese total removível, estando associadas ao desgaste da prótese e à sua predisposição à colonização por microrganismos. A proposição deste estudo foi realizar uma análise longitudinal e comparativa, destas duas propriedades, entre uma nova resina acrílica (Vipi Block Gum) para bases de próteses totais removíveis, implementada na tecnologia CAD-CAM, e duas resinas acrílicas termopolimerizáveis, sendo uma convencional (Vipi Cril Plus) e outra polimerizada por ação de micro-ondas (Vipi Wave), antes e após a aplicação de sucessivos ciclos de envelhecimento térmico por temociclagem, de modo a investigar a existência de uma correlação entre o processo de polimerização e o desempenho do material. Para isto, foram confeccionados um total de 60 corpos de prova com formato quadrangular com dimensões de 12x12x3mm, sendo destinados 20 corpos de prova para cada material. Para cada resina, 10 corpos de prova foram destinados ao teste de microdureza Knoop (KHN) e os outros 10 corpos de prova foram submetidos ao teste de rugosidade superficial (Ra-m). As análises dos corpos de prova, para ambos os experimentos, foram realizadas em quatro estágios distintos. As primeiras leituras foram realizadas após imersão dos materiais em água deionizada a 37ºC durante 24 horas (T1), com subsequentes análises após a aplicação de 500 ciclos (T2), 1000 ciclos (T3) e 3000 ciclos (T4) de termociclagem, com temperaturas de 5ºC a 55ºC com duração de 60 segundos para cada banho. Na avaliação estatística, a comparação das médias entre os grupos de resinas foi realizada com o teste de análise de variância (ANOVA) de um critério sendo, seguido do teste de Tukey. Para a comparação interna de cada grupo, em relação ao estágio de termociclagem, foi utilizado um ANOVA de medidas repetidas. O nível de significância adotado foi de 5%. Não houve diferença estatisticamente significante, na comparação intragrupos e intergrupos, em relação à rugosidade superficial (p>0.05). Na análise comparativa da microdureza entre os grupos, foi observada diferença estatisticamente significante nas análises em T1 e T2, com a resina Vipi Block obtendo valores superiores às outras resinas (p=0.00). Em T3, observou-se uma redução significativa da microdureza de todas as resinas, sendo mais pronunciada na resina Vipi Block Gum, tendo esta sido estatisticamente superior apenas em relação à Vipi Wave (p=0.01). Em T4 foi observado um aumento significativo na resina Vipi Cril Plus, com diferença estatisticamente significante (p>0.05) em relação às outras resinas. Na análise interna de cada grupo, foram observadas interações estatisticamente significantes em todas as resinas (p<0.05). A resina Vipi Block Gum teve sua microdureza drasticamente reduzida em T3, mantendo-se similar em T4, sendo significativamente inferiores (p<0.05) aos valores obtidos em T1 e T2. A resina Vipi Cril Plus sofreu uma acentuada redução na comparação em T1 em relação a T3 (p=0.021). Em T4, tornou-se estatisticamente superior a todos os outros períodos (p<0.05). A resina Vipi Wave sofreu redução significativa de T2 para T3 (p=0.01). Semelhantemente, obteve um aumento em T4, tornando-se estatisticamente superior a T3 (p=0.01). / Superficial roughness and microhardness are considered as extremely relevant properties which directly affects treatments with complete removable dentures, being them related to wear, and to the vulnerability of these prostheses to be colonized by microorganisms. The objective of this study was to perform a longitudinal analysis of these properties, making a comparison between a new CAD-CAM denture base acrylic resin (Vipi Block Gum), a conventional heat-polymerized and a microwave-polymerized resins, before and after the application of successive thermocycling cicles, in order to investigate a possible higher performance presented by the Vipi Block Gum resin. Sixty quadrangular shaped specimens with dimensions of 12x12x3mm were made and were equally divided between the three resins. For each material, 10 specimens were destined to the surface roughness analysis (Ra-m) and the other 10, for the Knoop microhardness (KHN) evaluation. The firsts analyses were performed after a 24-hour period of immersion in distilled water at 37ºC (T1), with subsequent analyses after 500 cicles (T2), 1000 cicles (T3) and 3000 cicles (T4) of thermocycling, with temperatures ranging from 5ºC to 55ºC and with 60 seconds of immersion, for each temperature. The statistical analysis, for the intergroup comparison, was done by applying a one-way analysis of variance (ANOVA) test, seconded by Tukeys posthoc test. For the intragroup analysis, a repeated measures ANOVA was applied. A significance level of 5% was adopted for both analyses. There were no significant differences for both intragroup and intergroup comparisons concerning the superficial roughness (p>0.05). The intergroup microhardness analyses showed significant differences at T1 and T2 (p=0.00), with higher values presented by the Vipi Block Gum resin when compared to the other groups. At T3, it was noticed a significant reduction for all materials, although it was more pronounced in the Vipi Block Gum resin, with this group having higher values than the Vipi Wave group (p=0.01). The comparison at T4 showed significant higher values presented by the Vipi Cril Plus in relation to the other groups (p<0.05). The intragroup analyses exhibited statistical significant differences for all materials (p<0.05). Vipi Block Gum resin suffered a significant decrease on its microhardness at T3, which remained similar at T4. However, these values were significant below (p<0.05) the ones obtained at T1 and T2. Vipi Cril Plus group showed a significant decrease at T3 in comparison with T1 (p=0.021). However, it increased significantly at T4 having statistical higher values than all other periods (p<0.05). Vipi Wave group suffered an expressive decrease at T3 in comparison with T2 (p=0.01). It also had an increase on its microhardness at T4, with statistical higher values than the ones observed at T3 (p=0.01).

Orientador: Keizo Yukimitu / Resumo: Com a crescente populacional a demanda pelos polímeros aumentou significativamente, levando assim a pesquisas cientificas visando adequar materiais as nossas necessidades. O PMMA ou acrílico é muito utilizado em nosso cotidiano, sendo um material muito versátil com aplicabilidade em diversos setores. O intuito deste trabalho foi realizar a produção de um filme de acrílico [Poli(metil-metacrilato)] isento de bolhas e transparente, a qual tivesse uma repetibilidade. Foi realizada a dopagem com terras raras, sendo o Óxido de Érbio e o Óxido de Itérbio escolhidos como dopantes em diferentes concentrações de gramas/mol por gramas/mol (0 % referência, 5 %, 10%, 15% e 20 %). Logo após foi feita a caracterização dos filmes, determinando o índice de refração das amostras utilizando o Interferomêtro de Michelson com laser He-Ne (vermelho) de comprimento de onda de 632,8 nm. Notamos que o índice de refração do PMMA na amostra de referência aumentou gradativamente com as dopagens, o laser diodo na cor verde de comprimento de onda de 532 nm também foi utilizado e os resultados demostraram comportamentos similares. A Espectroscopia no Infravermelho por Transformada de Fourier (FTIR) foi realizada, observando o aparecimento de picos característicos dos elementos dopantes nas amostras e que esses picos aumentavam conforme a concentração de dopagem aumentava. A Difração de Raios-X (DRX) nos mostrou a incidência picos de cristalinidade referentes aos elementos dopantes em contraste com o espec... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: With the growing population demand for polymers has increased significantly, leading to scientific research aimed at adapting materials to our needs. PMMA or acrylic is widely used in our daily lives, being a very versatile material with applicability in several sectors. The purpose of this work was to produce an acrylic film [Poly (methyl-methacrylate)] which had a repeatability. Rare earth doping was performed, with Erbium Oxide and Ytterbium Oxide chosen as dopants in different concentrations of grams / mole per gram / mole (0% reference, 5%, 10%, 15% and 20%). After the characterization of the films, determining the refractive index of the samples using the Michelson Interferometer with He-Ne (red) laser of wavelength of 632.8 nm, we noticed that the refractive index of the PMMA in the sample of reference period increased gradually with doping, the green diode laser wavelength of 532 nm was also used and the results demonstrated similar behaviors. Fourier Transform Infrared Spectroscopy (FTIR) was performed, observing the appearance of characteristic peaks of the dopant elements in the samples and that these peaks increased as the doping concentration increased. X-ray Diffraction (XRD) showed us the incidence of crystallinity peaks relative to the dopant elements in contrast to the normal PMMA spectrum demonstrating the insertion of the rare earths into the matrix structure. / Mestre

Environmentally friendly processing of materials is becoming an increasingly important consideration in a wide variety of emerging technologies. Polymer processing,in particular, has benefited tremendously in this venue from numerous advances achievedusing high-pressure carbon dioxide (CO2) as a viscosity modifier, plasticizing agent,foaming agent, and reaction medium. Polymer processing in supercritical fluids has been a major interest for a portfolio of materials processing applications including their impregnation into porous matrices. Also, SCF solvents are being examined as a media for polymerization processes, polymer purification and fractionation, and as environmentally preferable solvents for solution coatings. Pressurized CO2 isinexpensive, sustainable, relatively benign, and versatile due to its gas-like viscosity and liquid-like densities, which can be controllably tuned through appropriate choice of temperature and pressure. Addition of high-pressure CO2 to polymer systems can have a profound impact on their thermodynamic properties and phase behavior, since the number of interacting species increases due to the high-pressures, so that the compressibility also increases, as well as the plasticity effects. Even then, polymers are only sparingly soluble in CO2 unless one uses an entrainer or surfactant. An addition of a liquid monomer co-solvent results in greatly enhanced polymer solubility in the supercritical fluid at rather mild conditions of lower temperatures and reduced pressures.The focus of this research is to measure, evaluate and model the phase behavior of the methyl methacrylate-CO2 and the poly (methyl methacrylate)-CO2-methyl methacrylatesystem, where methyl methacrylate plays role of a co-solvent. Cloud-point data are measured in the temperature range of 30-80ʻC, pressures as high as 300 bar, co-solvent concentrations of 27 and 48.4 wt% MMA, and varying PMMA concentrations of 0.1, 0.2,0.5, and 2.5 wt%. Solubility data is reported for these systems. The experimental results are modeled accurately using the Statistical Associating Fluid Theory (SAFT) for multi component polymer/solvent mixtures. The measured solubility data appears to be significantly different than previously published results by McHugh et al, Fluid Phase Equilibria, 1999. Thorough investigation, re-calibration of the equipment, and repetition of the measurements has proved that the measured data is entirely correct and the reference data is significantly off, which indirectly gives credit to this work and opens room for amendments of those results.

The viscoelastic relaxation dynamics of a series of poly(methyl methacrylate) [PMMA] based nanocomposites filled with carbon nanotubes have been studied using dynamic mechanical analysis and broadband dielectric spectroscopy. The networks were prepared using four methods: (i) melt mixing, (ii) solution processing, (iii) in-situ polymerization, and (iv) polymer grafting. Nanotube modifications included surface oxidation via acid exposure and surface functionalization for polymer grafting. The effect of variations in processing method and nanotube modification on glass transition temperature (Tg) and relaxation dynamics was investigated. The relaxation behavior of the nanocomposites was sensitive to processing method and nanotube functionalization. Nanotube loading (to 5 wt%) led to a progressive increase in rubbery modulus, with the increase more pronounced in the solution-processed samples owing to enhanced nanotube dispersion. In the case of the oxidized nanotubes, loading led to an increase in modulus, but also a systematic decrease in Tg of ~ 15°C with 3 wt% nanotubes. For in-situ polymerized (PMMA/MWNT-ox) nanocomposites, there was no readily discernable trend in Tg. Composites prepared via in-situ polymerization in the presence of methyl methacrylate functionalized tubes (i.e., polymer grafting) displayed a positive shift in Tg of nearly 20°C at 1 wt% loading. Investigation of the dielectric relaxation of the PMMA/MWNT composites indicated a percolation threshold between 0.3 and 0.4 wt% MWNT.

Acrylic bone cements are used in dentistry and orthopedic surgery to fix prosthetic devices into the bone. Bone cements transfer and distribute the applied load and increase the load-carrying capacity of the prosthesis/cement/bone system with the help of mechanical bonding between the device and the bone. In spite of all their advantages, bone cements have several drawbacks such as insufficient mechanical properties, high exothermic polymerization temperature, release of monomer to the environmental tissue and loosening of implant. Studies are being carried out to improve bone cement formulations with low curing temperature, good mechanical properties and good biocompatibility. In this study, bone cements with different compositions were prepared by using poly(methyl methacrylate) (PMMA) microspheres, barium sulphate (BaSO4) radiopaque agent, inorganic hydroxyapatite (HA) particles and 1-dodecyl mercaptan (DDM) chain stopping agent. Mechanical and thermal properties of the prepared bone cements were examined. When 8% hydroxyapatite was added into the formulation, both tensile and compressive strengths were increased and curing temperature was decreased. Addition of 13% BaSO4 caused 0.98% and 10.29% decrease in tensile and compressive strength values, respectively. Addition of 1%, 2% and 3% DDM, relative to the amount of methyl methacrylate monomer, decreased the maximum temperature from 101.78&deg / C to 91.80&deg / C, 78.38&deg / C and 71.35&deg / C, respectively. All compositions of the prepared bone cements fulfilled the minimum compressive strength (70 MPa) requirement and the minimum curing temperature was obtained as 71.35&deg / C. In order to have optimum desired properties, further studies to improve biocompatibility, mechanical and thermal properties of bone cements are needed.

Made available in DSpace on 2014-12-17T14:07:08Z (GMT). No. of bitstreams: 1 ErikSS_DISSERT.pdf: 3248804 bytes, checksum: 7241bc799da79c157edae8da7a7966cc (MD5) Previous issue date: 2013-04-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Currently the search for new materials with properties suitable for specific applications has increased the number of researches that aim to address market needs. The poly (methyl methacrylate) (PMMA) is one of the most important polymers of the family of polyacrylates and polymethacrylates, especially for its unique optical properties and weathering resistance, and exceptional hardness and gloss. The development of polymer composites by the addition of inorganic fillers to the PMMA matrix increases the potential use of this polymer in various fields of application. The most commonly used inorganic fillers are particles of silica (SiO2), modified clays, graphite and carbon nanotubes. The main objective of this work is the development of PMMA/SiO2 composites at different concentrations of SiO2, for new applications as engineering plastics. The composites were produced by extrusion of tubular film, and obtained via solution for application to commercial PMMA plates, and also by injection molding, for improved the abrasion and scratch resistance of PMMA without compromising transparency. The effects of the addition of silica particles in the polymer matrix properties were evaluated by the maximum tensile strength, hardness, abrasion and scratch resistance, in addition to preliminary characterization by torque rheometry and melt flow rate. The results indicated that it is possible to use silica particles in a PMMA matrix, and a higher silica concentration produced an increase of the abrasion and scratch resistance, hardness, and reduced tensile strength / Atualmente a busca por novos materiais com propriedades adequadas para aplica??es espec?ficas vem aumentando o n?mero de pesquisas que visam suprir as necessidades do mercado. O poli(metacrilato de metila) (PMMA) ? um dos pol?meros mais importantes da fam?lia dos poliacrilatos e polimetacrilatos, principalmente pelas suas inigual?veis propriedades ?pticas e resist?ncia ?s intemp?ries, al?m de excepcional dureza e brilho. O desenvolvimento de comp?sitos polim?ricos por meio da adi??o de cargas inorg?nicas ? matriz de PMMA aumenta o potencial de uso deste pol?mero em diferentes ?reas de aplica??o. Dentre as cargas inorg?nicas mais utilizadas, podem-se destacar as part?culas de s?lica (SiO2), argilas modificadas, grafite e nanotubos de carbono. O objetivo principal deste trabalho ? o desenvolvimento de comp?sitos PMMA/SiO2, em diferentes concentra??es, para novas aplica??es como pl?stico de engenharia. Os comp?sitos foram produzidos por meio de extrus?o de filme tubular, e obtidos via solu??o, para aplica??o em chapas de PMMA comercial, e tamb?m por moldagem por inje??o, buscando o aumento da resist?ncia ? abras?o e ao risco do PMMA, sem comprometer a transpar?ncia. Os efeitos causados pela adi??o das part?culas de s?lica nas propriedades da matriz polim?rica foram avaliados atrav?s da resist?ncia m?xima ? tra??o, dureza, resist?ncia ? abras?o e ao risco, al?m das caracteriza??es preliminares por reometria de torque e ?ndice de fluidez. Os resultados indicaram que ? poss?vel utilizar part?culas de s?lica em uma matriz de PMMA, e que uma maior concentra??o de s?lica promoveu um aumento da resist?ncia ? abras?o e ao risco, dureza, e reduziu a resist?ncia m?xima ? tra??o