Orientador: Julio Roberto Bartoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-14T01:31:00Z (GMT). No. of bitstreams: 1 Faria_TatianeDiasMarques_M.pdf: 2955450 bytes, checksum: 63c9a4b195b9577f64bd709603a63795 (MD5) Previous issue date: 2008 / Resumo: Adesivos preparados com borracha termoplástica são de grande importância na indústria de adesivos sensíveis à pressão devido à sua grande versatilidade de processamento. Porém, geralmente estes adesivos apresentam desvantagens em ensaios em que temperaturas na faixa de 90º C são requeridas. Neste trabalho, foram preparados adesivos de borracha termoplástica com nanoargilas do tipo montmorilonita com duas organofilicidades diferentes, a fim de se estudar o desempenho das propriedades adesivas de peel, tack, shear e SAFT (Shear Adhesion Failure Temperature), além das propriedades de flamabilidade. Primeiramente, foram preparados masterbatches de resina hidrocarbônica e nanoargilas Cloisite® 20A e 25A (sendo a 20A mais organofílica) pelo processo de intercalação do fundido, através de extrusora dupla-rosca. Análises de difração de raios X e microscopia eletrônica de transmissão sugerem uma esfoliação da Cloisite® 20A na resina e uma intercalação da Closite® 25A. Depois, os masterbatches foram utilizados na preparação de compostos adesivos nas concentrações de 5 e 10 phr de nanoargilas, também em extrusora dupla-rosca. Ensaios de difração de raios X sugereriram a esfoliação das nanoargilas em todos os compostos adesivos, porém, pelas análises de microscopia eletrônica de transmissão, a amostra preparada com a Cloisite® 20A, na concentração de 10 phr, apresentou uma esfoliação relativamente maior. Ensaios dinâmico-mecânicos apresentaram significativo deslocamento da temperatura de transição vítrea (pico de tan d) para os adesivos preparados com a Cloisite® 20A, sugerindo a formação de nanocompósitos. Os módulos de armazenamento, na faixa de 70 a 93º C, obtidos com estes compostos adesivos, apresentaram também valores inferiores aos demais adesivos, sendo que a uma concentração de 10 phr o módulo foi o menor obtido e a uma concentração de 5 phr o módulo apresentou um valor intermediário. Os ensaios nas fitas adesivas demonstraram um maior equilíbrio de propriedades adesivas para o adesivo preparado com a Closite® 20A numa concentração de 5phr, apresentando este, módulo ótimo na faixa de temperatura de 70 a 93º C. Este adesivo manteve as propriedades de peel e tack próximas às do adesivo referência, melhorando significativamente as propriedades de shear a 70 e 93º C e SAFT. O ensaio de flamabilidade não foi conclusivo pois as amostras foram consideradas inflamáveis e houve muita variabilidade nos resultados obtidos para os tempos de queima. / Abstract: Adhesives prepared with thermoplastic rubber are very important for the pressure sensitive adhesives industry due to its easy processability. However, these adhesives are usually not indicated for applications in which temperature resistance around 90o C is required. In this study, thermoplastic rubber adhesives with nanoclays were prepared, in order to evaluate its adhesion performance: peel, tack, shear and SAFT. Moreover, the flammability properties are also going to be studied. Firstly, masterbatches of nanoclays Cloisite® 20A and 25A (being 20A more organophilic) and hydrocarbon resin were prepared through melt intercalation process, using a twin-screw extruder. Analysis through X ray difraction and transmission electronic microscopy suggests the exfoliation of Cloisite® 20A in the resin and the intercalation of Cloisite® 25A. After that, the masterbatches were used in the hot melt adhesives preparation, giving the nanoclays concentration of 5 and 10 phr. This process was also made in the twin-screw extruder. Analysis through X ray difraction showed again the exfoliation of the nanoclays in the adhesive, however, transmission electronic microscopy suggests that the sample prepared with Cloisite® 20A and concentration of 10phr presented the higher level of exfoliation. Dynamic-mechanical analysis showed a glass transition temperature shift (tan d peak) for the adhesives prepared with Cloisite® 20A, suggesting the formation of nanocomposites. The storage modulus of these adhesives, in the range from 70 to 93oC, showed values lower than the reference and other adhesives, being the adhesive with 20A and 10 phr the lowest modulus and the adhesive with 20A and 5 phr the intermediate value for the modulus. The testing done with the adhesive tapes, showed more balanced properties for the adhesive prepared with Cloisite® 20A and 5 phr, suggesting an optimal value for the modulus. This adhesive kept peel and tack properties close to the reference and showed improvements in properties like: 70 and 93oC shear and SAFT. Flammability testing was not conclusive because all samples were considered flammable and lots of variability was oberved in the burning times obtained. / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Indiana University-Purdue University Indianapolis (IUPUI) / Background and Rationale: As compared with glass-based ceramics, zirconia has gained considerable popularity in restorative dentistry due to its superior mechanical properties. Clinically, however, zirconia ceramics pose a significant challenge regarding the achievement of a reliable and durable bond to resin-based cements. Thus far, it has been established that zirconia bond to resin-based cements can be enhanced after different surface conditioning methods, such as airborne particle abrasion with aluminum oxide particles. Meanwhile, another major issue pertaining to bonding of ceramic restorations is related to its potential contamination before cementation. Briefly, after sandblasting and clinical try-in procedures, zirconia can be contaminated with saliva and/or blood. As with many metals, zirconium shows a strong affinity towards the phosphate group found in saliva and other fluids, which reacts with the zirconia surface and makes bonding very difficult. Recently, a new cleaning agent called Ivoclean® (Ivoclar-Vivadent), which is an alkaline suspension of zirconium oxide particles, has been introduced in the market to remove contamination from zirconia in an effort to improve bonding to resin cements. Objective: The purpose of this study was to evaluate the influence of saliva contamination and the effect of several cleaning methods, including Ivoclean on resin bond strength to zirconia. Materials and Methods: Eighty square-shaped specimens (ϕ = 12 mm x 12 mm x 3 mm) of yttria-stabilized full-contour zirconia (Diazir®, Ivoclar-Vivadent, Amherst, NY) were sectioned from zirconia blocks using a water-cooled diamond blade. Then, these specimens were embedded in acrylic resin, and their surfaces gradually finished with silicon carbide papers (600 grit to 1200 grit). The prepared zirconia surfaces were sandblasted with 50-μm aluminum oxide particles for 15 s, under 2.5 bars and from distance of 10 mm. After sandblasting the specimens were cleaned in an ultrasonic bath containing distilled water for 5 min and air-dried for 10s. All samples were equally divided into 4 groups (n = 20) according to the cleaning method. Airborne particle abraded specimens without contamination was served as the control group. Remaining groups were contaminated with saliva, and subjected to different cleaning protocols, namely: Ivoclean®, 70% isopropanol, and no treatment. Two resin cement buttons (Multilink – Ivoclar-Vivadent, Amherst, NY) were built over each zirconia surface and light-cured following the manufacturer recommendations. The influence of contamination and surface cleaning methods on ceramic bond durability were examined after 24 h on half of the samples in each group (n = 10, n = 20), and the other half (n = 10, n = 20) specimens will undergo 6000 thermocycles (TC) before shear bond testing in the universal testing machine. Conclusion of Expected Outcomes: The shear bond strength of resin cement to zirconia led to a significant improvement after cleaning with Ivoclean both immediately and after thermal aging.

Conventional methods of imparting toughness to ordinarily brittle thermosetting resins involve the incorporation of a second, discreet phase. Traditionally, this phase has been either a functionalized butadiene-acrylonitrile based elastomer or an unreactive thermoplastic. This dissertation describes the preparation, characterization, and evaluation of new functionalized polysiloxane elastomer and thermoplastic modifiers and their morphological implications to the toughening and physical behavior of, principally, epoxy thermosetting systems. Secondary amine-terminated poly(dimethyl-co-diphenyl siloxane) oligomers were found to be comparable tougheners to acrylonitrile-butadiene rubbers for a bisphenol-A based epoxy resin. The system that imparted the highest toughness was comprised of statistically placed 40% diphenyl and 60% dimethylsiloxane units with Mn̅ of 5000 g/mole loaded at 15% w/w. This composition resulted in a discreet second phase consisting of l μm spherical particles which were evenly dispersed throughout the cured epoxy matrix. Amine-terminated poly(arylene ether ketone) and poly(arylene ether sulfone) thermoplastics were reacted into an EPON 828/4,4'·DDS system. However, the polyketones proved to be ineffective toughening agents due to an incompatibility resulting in macroscopic phase separation. In contrast, the functionalized polysulfones were shown to be effective toughening agents, with the resultant morphology primarily a function of percent incorporation. At ~15% w/w, the polysulfone separated as l-2μm discreet particles while a 30% loading level resulted in a bicontinuous “honeycomb” morphology. The amine endgroups were shown to be necessary in controlling morphology and maximizing toughness. The polysulfone oligomers were also incorporated into a graphite fiber reinforced epoxy composite. Although improved mechanical properties were achieved, the toughness values were not as high as predicted by the neat resin evaluation. The morphology was less definable due to the complex nature and dimensions of the carbon fiber/matrix interactions. Finally, melt processing experiments indicated that amine-terminated polysulfones may act as effective processing aids for brittle bismaleimide systems, by reacting with the BMI, possibly via a Michael addition. This results in a chain extension and higher molecular weight without premature gelation occurring. / Ph. D.

This research project is partnership project involving industrial, university and government collaborators. The overall objective is to develop and enhance tools for use in Resin Transfer Moulding (RTM) design technology in order to re-design existing metallic parts using composite materials. / The specific objective of this work is to present preliminary research findings of the development of an optimized design of a leading edge slat (horizontal stabilizer component) from the Bell Model 407 Helicopter. The results presented here focus on the static stress analysis and the structure design aspects. The findings will serve as a basis for future design optimization as well as further developments in the use of RTM technology in re-designing metallic aeronautic components and can be considered to be "semi-optimized". / This research is based on extensive finite element analysis (FEA) of several composite material configurations, with a comparison made with the original metallic design. Different key criteria of the part design such as ply lay-up, bracket geometry, angle and configuration are tested using FEA technology with the objective of selecting the design which is minimizing stress concentrations. The influence of the modification of model-related parameters was also studied. / Preliminary comparative studies show that the slat configuration with half brackets opened towards the inside with an angle of 70 degrees (angle between the top of the airfoil and the side of the bracket) is the best option according to minimum stress concentration and structural flexibility. This choice is confirmed by other factors such as material savings and ease of processing.

Orientadores: Altair Antoninha Del Bel Cury, Tatiana Pereira Cenci / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-15T11:15:55Z (GMT). No. of bitstreams: 1 Fernandes_FredericoSilvadeFreitas_M.pdf: 733963 bytes, checksum: a861bd550ab439f138ef016317f27638 (MD5) Previous issue date: 2010 / Resumo: Biofilme de Candida spp formado na superfície de próteses removíveis é considerado o principal fator etiológico da candidose, a qual é a infecção oral fúngica mais prevalente em humanos. Em pacientes com comprometimento motor, o uso de limpadores químicos é indicado para o controle desse biofilme, entretanto, pouco se conhece sobre o efeito desses agentes sobre o biofilme de Candidas não-albicans. Adicionalmente, a literatura é escassa de estudos avaliando a formação de biofilme de Candida sobre novos materiais para base de próteses. Assim, o objetivo desse estudo foi avaliar o efeito de limpadores químicos sobre o biofilme mono e multi-espécie de Candida formado sobre a superfície de materiais para confecção de próteses removíveis. Foram confeccionados espécimes de resina de polimetilmetacrilato (PMMA) e resina poliamida, os quais, após a padronização da rugosidade de superfície (0,34 ± 0,02 µm), foram submetidos à avaliação da energia livre de superfície (ELS) ou à formação de biofilme. Biofilme de Candida albicans e/ou Candida glabrata foi formado por 72 h, sendo os espécimes, previamente, submetidos à formação da película adquirida. Após o período de formação do biofilme, os espécimes foram submetidos aos tratamentos, segundo o tempo recomendado por cada fabricante: limpador químico enzimático (3 min); limpador químico sem enzimas (5 min); e hipoclorito de sódio (NaOCl) a 0,5% (10 min). A água destilada e deionizada foi utilizada como controle. Após os tratamentos, os espécimes foram sonicados (7W por 30s) em solução salina, para remoção das células aderidas. Essa solução foi serialmente diluída em solução salina e semeada em CHROMagar® Candida. O número de células viáveis de Candida foi expresso em unidades formadoras de colônia (UFC)/mm2. Os dados da ELS e ângulo de contato foram submetidos a ANOVA um fator, enquanto que os dados de células viáveis de Candida foram submetidos a ANOVA três fatores, seguido do teste de Tukey-Kramer. Todos os biofilmes avaliados apresentaram maior crescimento na resina de poliamida (p<0,0001), entretanto, essa resina apresentou um menor valor de ELS quando comparada à resina de PMMA. Os limpadores químicos, contendo ou não enzimas, reduziram significantemente os níveis de Candida, sem haver diferença estatística entre eles (p=0,9999). Entretanto, o NaOCl a 0,5% foi mais eficaz, na medida em que resultou na ausência de células viáveis. Em todas as situações avaliadas, a C. glabrata apresentou maiores valores de células viáveis do que a C. albicans (p=0,0002). Nas condições desse estudo, conclui-se que a resina de poliamida possibilitou uma maior proliferação de Candida; e os limpadores químicos comerciais foram eficazes na redução dos níveis de Candida spp, mas apenas a solução de hipoclorito de sódio a 0,5% resultou na ausência de células viáveis na superfícies dos materiais testados / Resumo: Os limpadores químicos de prótese têm sido bastante indicados para o controle do biofilme formado sobre próteses removíveis de pacientes com comprometimento motor. Apesar de estudos prévios terem mostrado que uma única imersão nesses agentes é capaz de reduzir os níveis de Candida albicans do biofilme formado sobre próteses removíveis, pouco se sabe sobre o efeito do uso diário desses limpadores sobre o biofilme residual de Candida. Assim, o objetivo desse estudo foi avaliar a eficácia do uso diário de um limpador químico enzimático sobre o biofilme de C. albicans formado sobre a superfície de materiais para confecção de próteses removíveis; bem como a atividade enzimática das células de Candida desse biofilme após exposições diárias a esse limpador de prótese. Foram confeccionados espécimes de resina de polimetilmetacrilato (PMMA) e resina de poliamida, nos quais foi realizada, inicialmente, a padronização da rugosidade de superfície (0,34 ± 0,02 ?m). Após a formação da película adquirida, os espécimes foram divididos aleatoriamente em 12 grupos (n=9) para formação do biofilme de C. albicans por 72 horas. Após esse período, os espécimes foram tratados por 1, 4 ou 7 dias, sendo realizado um tratamento por dia, com um limpador químico enzimático (Polident 3 Minutes) ou com água destilada (controle negativo). Após os respectivos períodos de tratamento, os microrganismos remanescentes foram removidos da superfície dos espécimes por meio de ondas ultra-sônicas (7W por 30s). Em seguida, as unidades formadoras de colônia (UFC) foram calculadas e a atividade enzimática das células remanescentes foi avaliada. Os dados foram submetidos à ANOVA um fator ou dois fatores, seguido do teste de Tukey-Kramer. O biofilme de Candida albicans formado sobre a resina de poliamida apresentou maiores níveis de Candida e uma maior atividade fosfolipásica que o biofilme formado sobre a resina de PMMA (p<0,001). O limpador químico enzimático reduziu significantemente os níveis de Candida albicans em todos os períodos avaliados (p<0,001), entretanto os níveis desse microrganismo aumentaram com o tempo, sendo observada diferença estatisticamente significante entre os períodos avaliados (p<0,001). As exposições diárias a esse limpador químico aumentaram a virulência das células de Candida, no que diz respeito à atividade fosfolipásica. Nas condições desse estudo, conclui-se que o uso diário do limpador químico enzimático não foi capaz de impedir a proliferação de Candida albicans no biofilme residual, apesar de ter interferido no crescimento desse biofilme. / Abstract: Candida denture biofilm is considered the the primary aetiological agent for the development of oral candidosis, which is the most common fungal oral infection in humans. Although, for patients with limited motor capacity, chemical cleansing with immersion in denture cleansers has been shown to be effective in controlling Candida biofilm accumulation, limited data is available on the effect of those cleansing agents on other Candida species biofilms. Additionally, few studies have examined the development of Candida biofims on novel denture materials. This study evaluated the efficacy of denture cleansers on C. albicans and C. glabrata single and dual-species biofilms formed on novel denture base materials. Specimens of polymethylmetacrylate resin (PMMA) and polyamide resin were prepared and had their surface roughness standardized (0.34 ± 0.02 µm). Part of the specimens had their surface free energy measured and the other specimens were submitted to the biofilm assays. C. albicans and/or C. glabrata biofilm was formed for 72 hours on saliva-coated specimens. On the 3rd day, specimens were treated with an enzymatic cleanser, denture cleanser or 0.5% sodium hypochlorite (NaOCl) solution by soaking for, 3, 5 and 10 min, respectively. Water was used as negative control. After treatment, adhered cells were detached from the acrylic resin surface by ultrassonic waves at 7 watts for 30 seconds in phosphate buffered saline solution (PBS). This solution was serially diluted in PBS and plated on CHROMagar® Candida. Candida viable cell were expressed in colony forming units per surface area (CFU/mm2). Data of surface free energy and contact angle were analyzed by one-way ANOVA, and data of Candida species were analyzed by three way-ANOVA followed by Tukey-Kramer test. All tested biofilms displayed significantly higher growth on polyamide thermoplastic resin (p<0.0001), which presented the lowest SFE. Denture cleansers significantly decreased Candida spp levels, with no statistical difference between them (p=0.9999); however, 0.5% NaOCl solution was more effective, since, after treatment, no viable cell was observed. Candida glabrata revealed significantly higher CFU counts when compared to Candida albicans under all experimental conditions (p=0.0002). Our study has shown that polyamide resins may present a convenient substratum for microbial colonization. Although denture cleansers reduced Candida levels, sodium hypochlorite should be preferred as it was efficient to eliminate Candida cells from the tested materials / Abstract: Chemical cleansing with immersion in denture cleansers has been indicated for denture biofilm control in patients with limited motor capacity. Although previous studies have shown that a single immersion in those agents is able to substantially reduce Candida albicans biofilm levels, the effect of the routine use of denture cleansers on the Candida residual biofilm is poorly understood. This study evaluated the efficacy of daily use of an enzymatic denture cleanser on C. albicans biofilm formed on denture base materials; and the enzymatic activities of Candida biofilm cells after daily exposure to this cleanser agent. Polymethyl methacrylate (PMMA) and polyamide resins specimens were prepared (n=54), and their surface roughness was standardized (0.34 ±0.02 ?m). Saliva-coated specimens were randomly divided by lottery into 12 groups (n=9) for biofilm assay. C. albicans biofilm was formed for 72 hours, and then specimens were treated for 1, 4 or 7 days, once a day, with an enzymatic cleanser (Polident 3 Minutes), or distilled water (negative control). Remaining adherent microorganisms were removed from the treated specimens by ultrasonic waves at 7 watts for 30 seconds, and then colony-forming units (CFU) were calculated and remaining cells enzymatic activities were determined. Data were analyzed by 1-way or 2-way ANOVA followed by the Tukey-Kramer test. C. albicans biofilm formed on polyamide resin showed significantly higher Candida levels and phospholipase activity (p<0.001) than biofilm formed on PMMA resin. The enzymatic cleanser significantly reduced C. albicans levels in all evaluated periods (p<0.001); however, the number of this microorganism increased with time, showing statistical difference among the treatment periods (p<0.001). The daily exposure to the denture cleanser increased Candida cells virulence, with regard to phospholipase activity. Our study has shown that the enzymatic cleanser daily use did not prevent C. albicans proliferation in residual biofilm; however, this agent reduced this fungus rate of growth. / Mestrado / Protese Dental / Mestre em Clínica Odontológica

No description available.

Orientador: João Sinezio de Carvalho Campos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T01:48:34Z (GMT). No. of bitstreams: 1 Liba_AdemirDonizeti_M.pdf: 4797015 bytes, checksum: 1351ff08893b1a29731246cf2e4cd3c8 (MD5) Previous issue date: 2004 / Resumo: A resina de poliéster insaturada (RPI) é um polímero termofixo de baixo peso molecular obtido por condensação, o processo inicia-se através da esterificação entre diálcoois e diácidos saturados e insaturados, com o aumento do peso molecular do polímero, a retirada da água, que é gerada como subproduto da reação, torna-se difícil e lança-se mão do uso do vácuo ou de um maior fluxo de gás inerte para finalização da reação. Quanto à produção em escala industrial, apesar de conhecerem-se métodos de produção contínua, esta na maioria das indústrias é conduzida em bateladas com tempo de duração em média de 20 horas, podendo variar de acordo com a escolha das matérias primas utilizadas. Para a obtenção do polímero dentro dos parâmetros especificados, se faz necessário o controle dos radicais carboxilas, medidos através do índice de acidez (IA) e do peso molecular médio numérico (Mn), sendo este último parâmetro obtido de maneira indireta através da viscosidade(n). Para a viscosidade pode-se utilizar a escala Gardner, ou o viscosímetro cone e placa. A marcha de execução destas técnicas envolve várias etapas, desde a retirada da amostra até a obtenção do resultado da medida, sendo que para a amostragem, dependendo do equipamento disponível, esta pode implicar na interrupção do processo produtivo. Neste trabalho apresenta-se uma alternativa para o controle da reação, através do infravermelho próximo (NIR), em substituição às técnicas convencionais, com a vantagem do acompanhamento e do controle ser passível de execução em tempo real e sem a necessidade da retirada de amostras. Utilizou-se como base para o trabalho, a utilização anterior do NIR em processos envolvendo outros polímeros, tais como o policloreto de vinila (PVC), o policarbonato, o poliuretano e outros. Para verificar-se a viabilidade da utilização do NIR em substituição as técnicas convencionais, os valores obtidos para o IA e a viscosidade através destas técnicas foram comparados estatisticamente aos valores obtidos pelo NIR, obtendo-se forte correlação, com confiabilidade estatística de 95%. Com os resultados obtidos concluiu-se que o NIR pode ser utilizado com vantagens para o controle do processo de obtenção da resina de poliéster insaturada / Abstract: The unsaturated polyester resin (UPR) is a thermosetting polymer of low molecular weight obtained by condensation, the process begins through a esterification, between glycols and a mix of saturated and unsaturated acids, when the molecular weight of the polymer increase, the retreat of the water, generated as by-product of the reaction, if it turns more difficult and are necessary to use a vacuum or a larger flow of inert gas for finalization of the reaction. The production in industrial scale, in spite of they know each other methods of continuous production, are made in a batch with 20 hours long, could vary in agreement with the choice of the raw materials. For the obtaining of the polymer in the specified parameters, are necessary the control of the acid number (AN) and of the molecular weight (Mn), being this last obtained parameter in an indirect way through the viscosity. For measures those properties, are used as tools for the measure of the acidity number by titrimetric methods, and for the viscosity are use the Gardner scale, or the cone and plate viscometer. These techniques involves several stages, from the take of the sample to the obtaining of the result of the measure, and for obtain the sampling, depending on the available equipment, this can implicate in the interruption of the productive process. In this work we propose an alternative for the control of the reaction, by near infrared spectrometer (NIR), in substitution to the conventional techniques, with the advantage of the attendance and of the control to be susceptible to execution in real time and without the need of take samples. It was used as base for the work, the previous work of NIR in processes involving other polymeric materials, such as polyvinyl chloride (PVC), polycarbonate, the polyurethane and others. To verify the viability of the use of NIR in substitution of the conventional techniques, the values obtained for acid number and viscosity through these techniques were compared to the values obtained by NIR, being obtained strong correlation, with statistical reliability of 95%. With the obtained results it was ended that NIR can be used with advantages for the process control of unsaturated polyester resin / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química