Orientador: Ana Maria Frattini Fileti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-13T11:28:04Z (GMT). No. of bitstreams: 1 Pereira_PauloRobertoAlves_D.pdf: 4037300 bytes, checksum: da84be7f1c008bf7d365f44936f53414 (MD5) Previous issue date: 2007 / Resumo: Um grande número de indústrias químicas, bioquímicas e farmacêuticas, utiliza reatores de polimerização em batelada para a produção de polímeros especiais de alto valor agregado. Para tanto, são requeridas ferramentas de controle que forneçam informações confiáveis e otimizem as principais variáveis envolvidas na reação, conferindo propriedades específicas aos polímeros. Para o presente trabalho, adotou-se a reação de polimerização em batelada do metacrilato de metila (MMA) via radicais livres em solução, formando o polimetacrilato de metila (PMMA). O peróxido de benzoíla foi usado como iniciador e o acetato de etila como solvente. Para as etapas da reação do MMA, utilizou-se um modelo matemático fenomenológico conhecido e testado experimentalmente. Para o controle ótimo da temperatura do reator (T), manipulou-se a vazão do líquido de resfriamento (Fcw) e a potência de aquecimento on/off (Q) para o reator em batelada, composto de vidro encamisado, com capacidade para um litro de mistura reacional e um litro de fluido de resfriamento em sua jaqueta. Para a otimização do sistema MMA-PMMA, optou-se pela metodologia IDP (Iterative Dynamic Programming). Desenvolveu-se um programa IDP em Matlab, cuja confiabilidade foi testada com sucesso por um exemplo disponível na literatura especializada. Os resultados mostraram que o programa IDP é capaz de otimizar diferentes características de interesse como a conversão do monômero (Xm), representando um potencial de melhoria econômica. A comparação dos resultados das trajetórias de T e de Fcw obtidos pela otimização off line via IDP, com os resultados experimentais obtidos por Nunes (2004) e Antunes et al. (2005), apresenta comportamentos discrepantes ao longo do tempo. Esta discrepância pode explicar o rendimento experimental de 0,4 para Xm, cujo setpoint para T foi fixado em 63 ºC (336 K) e o seu controle executado pelo modelo PIDFuzzy, contra 0,6 da otimização off line via IDP, que considera os valores de Xm obtidos em cada estágio P para indicar novos setpoints de T. Logo, pode-se inferir que não é o controle de T através de um setpoint fixo que irá permitir um valor máximo de Xm, mas o controle de T para setpoints variáveis em cada estágio de tempo P, definidos pela trajetória de Xm obtida na otimização off line. Esta constatação pode ser considerada a grande contribuição da metodologia IDP para este trabalho. Portanto, pode-se afirmar que o programa IDP desenvolvido é adequado para a otimização off line do processo de polimerização do MMA. / Abstract: A considerable number of chemical, biochemical and pharmaceutical industries, make use of batch polymerization reactors in their processes, mainly to produce polymers with special characteristics and high aggregated value. In order to supply products with high quality standards required by the market, control tools are necessary to provide as fast as possible reliable processes information and at the same time, to optimize the main variables involved in the reaction and attribute special properties to the polymers. This work is concerned with the methyl metacrilate (MMA) free-radical batch solution polymerization reaction, which produces the polymethyl methacrilate (PMMA). Ethyl acetate is used as solvent and benzoyl peroxide as the reaction initiator. To represent the MMA polymerization reaction, a known and experimented phenomenological mathematical model was used. For the reaction optimal temperature (T) control were defined as manipulated variables the inlet cooling water flow rate (Fcw) and the heating power (Q). The equipment is a glass reactor of one liter capacity surrounded by a glass jacket for the heat exchange with the cooling water. To optimize the MMA-PMMA system, a program based on IDP (Iterative Dynamic Programming) technique was developed in Matlab and successfully tested through an example from the specialized literature. The results showed that the IDP program is capable of optimizing different characteristics of interest as the monomer conversion (Xm), and may represent a potential of economic improvement. The comparison between the results of trajectories T and Fcw from the off line optimization via IDP, with the experimental results presented by Nunes (2004) and Antunes et al. (2005), shows discrepant behaviors along the reaction time. This discrepancy may explain the poor experimental value of 0.4 for Xm, once the set point for T was set up in 336 K and its control performed by a PID-Fuzzy model during the runs, against a value of 0.6 for Xm from the off line optimization trough IDP program, which suggests new set points based on the results of Xm for each stage P. Therefore, it is possible to affirm that the use of a fixed set point to control T during the reaction probably will not lead the reaction to a maximum value of Xm, but the use of variable set points for each time stage P, according to off line optimization results for Xm. This description may be considered the major contribution from the IDP methodology for this work. Therefore, the program IDP developed in this work can be considered suitable for the off line optimization of MMA polymerization reaction. / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Probe microscopy techniques (Atomic Force Microscopy and Kelvin Force Microscopy) have been shown to be instrumental in the analysis of samples; such as resists and nanostructured materials. Through these techniques detailed surface information has been derived, including information such as surface roughness and surface charge distribution. Poly(Methylmethacrylate) (PMMA), remains at the forefront of resists utilised in e-beam lithography in the electronics industry. Surface morphology (specifically roughness) analysis remains a key parameter of investigation, particularly in the examination of polymeric films. This research aimed to investigate PMMA based electron beam resists as well as a novel (SML) resist material in terms of suitability for electron-beam lithography. Various concentrations (5, 7, 8, 9 and 11% w/v) of both PMMA and the novel resist material were spin-coated onto silica substrates. Samples were baked at 180oC for 3 minutes and examined under ultra-high vacuum using Omicron AFM/SPM to derive RMS values in order to assess roughness in addition to thickness measurements taken. SML resists were then utilised in the development of a new digital etch onto InGaAs/InAlAs wafer. The novel, SML resist material was found to offer smoother resist surface even at higher concentrations of polymer, a difference which was observed to be statistically significant (p<0.01). The SML resist was also notably thicker than the comparable PMMA resist (p>0.05) indicating that lower concentrations of the novel resist would be required to achieve the required resist thickness. Digital etching rates were found to be in agreement with previously documented findings. SML was concluded to be a superior resist in terms of thickness and smoothness, with AFM being further established as an essential characterization technique.

Vycházíme-li z lehčených přírodních materiálů, lze od porézních materiálů s gradientem porozity očekávat mechanické vlastnosti nadřazené konvenčím polymerním pěnám, a to díky jejich specifické architektuře. Tyto vlastnosti umožňují použití lehčených materiálů jako strukturních prvků. V této práci je popsaná příprava gradientních porézních materiálů pomocí laminování a/nebo 3D tisku. Provedeny byly statické a dynamické mechanické testy na obou kvazi homogenních a gradientně porézních pěnách poskytující experimentální podklad pro hypotézu deformační odezvy plynoucí ze strukturní architektury. Data se interpretovala užitím zavedených teoretických modelů. Naše výsledky vedly k závěru, že tyto teoretické modely odvozené od pěn s pravidelnou strukturou není vhodné aplikovat pro pěny s gradientem porozity, protože prokazují podstatně lepší mechanické vlastnosti než homogenně porézní pěny.

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This work deals with electrolytic conductivity of gel polymer electrolytes. In the theoretical part of the work the methacrylates, the polymerization and the basic outlines of gel polymer electrolytes conductivity are described. The preparation and electrical conductivity of gels based on PMMA are described in the experimental part.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Recent theoretical and experimental studies, suggest that Carbon nanotubes are 10-100 times higher than the strongest steel at a fraction of the weight. There are two main types of CNTs that can have high structural perfection. Single-walled nanotubes (SWNTs) consist of a single graphite sheet seamlessly wrapped into a cylindrical tube. Multi-walled carbon nanotubes (MWNTs) comprise an array of such nanotubes concentrically nested like rings of a tree trunk. Denture base acrylics have been reinforced with different materials with limited success. No single reinforced material has showed a great statistical difference in mechanical improvement. The goal of this investigation was to study the effects of Single Walled Carbon Nanotubes reinforcement on the mechanical properties of commercially available denture base PMMA. Denture Base material was reinforced with Single-walled Carbon Nanotubes (SWNTs) at dispersion of 0.25 wt % (group 1), 0.50 wt % (group 2), 0.75 wt % (group 3) and 0.0 wt % (group 4, control). Samples from each group were evaluated for microhardness, flexural strength, flexural modulus, and fracture toughness. The samples were tested in two conditions, as manufactured (dry) and after storing at 37 C for 7 days (wet). Data from four experiments was analyzed by ANOVA. All control sample values were in the range of acceptance compared with previous studies. Higher values were obtained for the control groups for flexural strength and modulus compared with the experimental samples. (p < 0.05) There was no statistical difference regarding fracture toughness between control and experimental groups. A statistical difference was observed in Hardness. The experimental group showed higher values under compression.

Model glassy polymers, polymethyl methacrylate (PMMA) and polycarbonate (PC) are used to experimentally probe several aspects of polymer fracture. In Chapter 1, the method of pre-stress is employed as a means of improving the fracture properites of brittle PMMA. Samples are tested under equi-biaxial compression, simple shear and a combination of biaxial compression and shear. Equi-biaxial compression is shown to increase the threshold stress level for projectile penetration whereas shear pre-stress has a large effect on the overall energy absorbed during an impact. There is also an apparent interaction observed between compression and shear to dramatically increase the threshold stress. Pre-stressed laminates of PMMA and PC show an increase in damage area because of the unique formation of a secondary cone. In Chapter 2, the effect of stress state on stress relaxation in PMMA and PC is investigated. Direct comparisons are made between uniaxial and biaxial loading conditions. The experimental methods used highlight the effect of hydrostatic stress on the relaxation process. The data shows an increase in relaxation time and increase in the breadth of the relaxation spectrum with increases in hydrostatic stress. This suggests that the stress state can have a significant effect on the useful lifetime of pre-stressed articles. In Chapter 3, Mode I and II fracture studies are performed from quasi-static to low velocity impact rates on PMMA and PC. Mode II testing utilizes an angled double-edge notched specimen loaded in compression. The shear banding response of PMMA is shown to be highly sensitive to rate, with diffuse shear bands forming at low rates and sharp distinct shear bands forming at high rates. As the rate increases, shear deformation becomes more localized to the point where Mode II fracture occurs. PC is much less rate dependent and stable shear band propagation is observed over the range of rates studied with lesser amounts of localization. A new theory is formulated relating orientation in a shear band to intrinsic material properties obtained from true-stress true-strain tests. In a qualitative sense the theory predicts the high rate sensitivity of PMMA. A kinematic limit for orientation within a shear band is also derived based on entanglement network parameters. Mode II fracture in PMMA is shown to occur at this kinematic limit. For the case of PC, the maximum impact rates were not high enough to reach the kinematic limit. In Chapter 4, the deformation response, as observed in a shear band is interpreted through the characterization of the "intrinsic material properties" obtained from true stress - true strain 8compression tests. The relatively high rate sensitivity of PMMA deformed at room temperature is related to the proximity of the beta transition to the test temperature. This is also shown in corollary experiments on PC where deformation near the beta transition is accompanied by an increase in rate sensitivity. Physical aging results in a more narrow alpha transition and is shown to increase strain localization and decrease rate sensitivity at low strain rates.

No description available.

No description available.