Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-09-12T19:07:13Z No. of bitstreams: 1 JoyceGatti.pdf: 1210487 bytes, checksum: 71d9dfa07d0b48a036023d3e8f13c597 (MD5) / Made available in DSpace on 2017-09-12T19:07:14Z (GMT). No. of bitstreams: 1 JoyceGatti.pdf: 1210487 bytes, checksum: 71d9dfa07d0b48a036023d3e8f13c597 (MD5) Previous issue date: 2017-04-28 / The search for adhesive restorations that have greater durability in the oral cavity is constant. Enamel adhesion is already well established and resistant over time. The great challenge is to improve the adhesion of the resin to the dentin, since this substrate is more complex, presenting a greater amount of water in its composition, which directly compromises the adhesion process. In the literature, two major problems related to the degradation of the resin-dentin adhesive interface over time are highlighted: hydrolytic degradation, caused by the deleterious effects of the water inherent to the tooth and the adhesive material used; and the enzymatic degradation caused by the proteolytic enzymes, especially the metalloproneinases (MMP's) present in the dentin structure and that are activated after the acid conditioning. Several proposals have been tested to combat these problems. In the present work, we will focus on two strategies used to improve bond strength to dentin over time: the application of 2% chlorhexidine (CHX) and the ethanol wet-bonding technique (EWBT). The main objective was to evaluate in vitro the effects of the association of these two techniques on the bond strength values to dentin after 24h, 6 months and 12 months of storage in water by means of microtensile bond strength test. Two forms of association were used: the first applying the techniques in separate steps, the CHX technique being applied previously to EWBT; and the second by means of an experimental solution handled in a pharmaceutical laboratory composed of 2% CHX diluted in absolute ethanol solution and applied once in the exposed dentin and conditioned with phosphoric acid. The thesis was divided into two chapters that evaluate these techniques in vitro. The first chapter evaluated after 6 months the association of the techniques in separate steps in two types of adhesive systems (3-step and 2-step etch-and-rinse). It was concluded that the association was able to preserve the adhesive interface after the period evaluated only when using the 2- step adhesive system, presenting RU values statistically superior to the control group of this adhesive. The second chapter evaluated after 12 months the association of singlestep techniques by mixing the two solutions (CHX and absolute ethanol) using a etchand-rinse 2-step adhesive system. The results showed that the mixture of solutions applied in a single step was not able to preserve the adhesive interface after the period evaluated, in addition to presenting the worst results when compared to the other techniques tested, with a reduction of RU values of 55.65 %, thus not being an option to improve the longevity of adhesive interfaces. / A busca por restaurações adesivas que tenham maior durabilidade na cavidade bucal é constante. O grande desafio da adesão é a união da resina à dentina, pois este substrato apresenta maior quantidade de água na sua composição, comprometendo o processo adesivo. Dois grandes problemas relacionados à degradação da interface adesiva resinadentina ao longo do tempo são conhecidos: a degradação hidrolítica, ocasionada pelos efeitos deletérios da água inerente ao dente e ao material adesivo; e a degradação enzimática, ocasionada pelas enzimas proteolíticas, em especial as metaloproneinases (MMP’s) presentes na estrutura dentinária e ativadas após o condicionamento ácido. Várias propostas têm sido testadas para minimizar esses problemas e melhorar a estabilidade da interface resina-dentina. No presente trabalho, foi dado enfoque para duas delas: a aplicação de clorexidina a 2% (CHX) e a técnica da adesão úmida por etanol (TAUE). O objetivo principal foi avaliar in vitro os efeitos da associação dessas duas técnicas nos valores de resistência de união (RU) à dentina após 24h, 6 meses e 12 meses de armazenamento em água por meio de testes de microtração. Foram utilizadas duas formas de associação: a primeira aplicando as técnicas em passos separados, sendo a CHX aplicada previamente à TAUE; e a segunda por meio de uma solução experimental manipulada em laboratório farmacêutico, composta por CHX 2% diluída em solução de etanol absoluto e aplicada de uma única vez na dentina desmineralizada. A tese foi dividida em dois capítulos que avaliam in vitro essas técnicas. O primeiro capítulo avaliou após 6 meses a associação das técnicas em passos separados em dois tipos de sistemas adesivos (convencional de 3 passos e de 2 passos, respectivamente). Concluiu-se que a associação foi capaz de preservar a interface adesiva após o período avaliado somente quando se utilizou o sistema adesivo de 2 passos, apresentando valores de RU estatisticamente superiores ao grupo controle desse mesmo adesivo. O segundo capítulo avaliou após 12 meses a associação das técnicas em passo único por meio da mistura das duas soluções (CHX e etanol absoluto), utilizando um sistema adesivo convencional de 2 passos. Os resultados mostraram que a mistura das soluções aplicadas em único passo não foi capaz de preservar a interface de união após o período avaliado, além de ter apresentado os piores resultados quando comparada às demais técnicas testadas, com redução dos valores de RU de 55,65%, não sendo, dessa forma, uma opção para melhorar a longevidade das interfaces adesivas.

Elastômeros termoplásticos têm sido largamente empregados como adesivos hot melt em diferentes setores da indústria. Neste trabalho foram estudados dois copolímeros em bloco de poliuretano na forma particulada, base poliéster (TPU1) e policaprolactona (TPU2), com o objetivo de avaliar o desempenho dos mesmos como adesivos particulados. Foram preparadas diferentes composições dos TPUs com aditivos de policarbodiimida (A), resina hidrocarbônica (B) e poliisocianato (C). Os TPUs aditivados em diferentes composições foram avaliados por termogravimetria (TGA) e calorimetria diferencial de varredura (DSC) e quanto à resistência da colagem. A cinética de cristalização dos TPUs particulados puros e aditivados em diferentes isotermas foi acompanhada por DSC. Os adesivos TPU1 apresentaram velocidade de cristalização mais lenta, com exceção do TPU1 contendo os aditivos A e B (TPU1AB). Os adesivos TPU2 apresentaram taxa de cristalização maior somente quando aditivado com mistura de aditivos (TPU2AB; TPU2BC; TPU2ABC; TPU2AC). O expoente de Avrami (n) foi inferior para os TPUs aditivados, o que sugere a ocorrência de alteração no tipo de nucleação e geometria de crescimento dos cristalitos. Os TPU1 (poliéster) e TPU2 (policaprolactona) apresentaram perfil de degradação térmica diferenciados devido a diferenças na estrutura química dos mesmos. Os adesivos TPU2 apresentaram valores de resistência mecânica mais elevados que os TPU1, em colagens de substratos de PVC. Os adesivos com maiores valores de resistência (TPU1A e TPU2A) foram extrusados e micronizados para uso como tal. O adesivo TPU1A micronizado apresentou aumento da resistência mecânica. As colagens com os adesivos TPU1 e TPU2 apresentaram falha coesiva e as composições TPU1B e TPU2AC demonstraram falha coesiva e adesiva em ensaio de tração. O processamento dos adesivos TPU1 por tratamento de plasma favoreceu um incremento dos valores de resistência de colagens em substratos de PVC. / Thermoplastic elastomers have widely been used as hot melt adhesives in different industry sectors. In this paper were studied two polyurethane block copolymers in particulate form, based polyester (TPU1) and polycaprolactone (TPU2), in order to evaluate their performance as adhesives. Different compositions of TPUs were prepared with polycarbodiimide (A), hydrocarbon resin (B) and polyisocyanate (C) additives. The TPUs with additives in different compositions were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and by the bond strength. The kinetics crystallization of pure and additivated TPUs at different isotherms were followed by DSC. The TPU1 adhesives showed lower crystallization rate, except the TPU1 with both A and B additives (TPU1AB). The TPU2 adhesives showed higher crystallization rate only when formulated with mixture of additives (TPU2AB; TPU2BC; TPU2ABC; TPU2AC). The Avrami exponent (n) was lower for the TPUs containing additives, which suggests changes in the nucleation type and crystallites growth geometry. The thermal degradation profile of both TPU1 (polyester) and TPU2 (polycaprolactone) adhesives were quite different due to chemical differences. The TPU2 adhesives showed higher strength values than TPU1s on PVC substrates. The adhesives with higher bond strength (TPU1A and TPU2A) were extruded and micronized, and the TPU1A adhesive showed improved bonding property. The TPU1 and TPU2 adhesives on PVC collages showed cohesive failure and the TPU1B and TPU2AC compositions showed cohesive and adhesive failure under tension test. The adhesive plasma treatment promoted a bonding increasing of TPU1 on PVC substrates.

Approximately 26% of the U.S. population between the ages of 65 and 74 years are completely edentulous. Of the different proposed predictors and risk factors, low income and education levels have the highest correlation with tooth loss. While the incidence of complete edentulism in the United States has progressively declined over the past decade, the continued growth of the population strongly suggests that edentulism prevalence will likely remain constant or increase over the next few decades. In patients wearing complete prosthetic appliances, several post-treatment complications may arise, including denture associated Candida species infections and mucosal stomatitis. These type of fungal infections are associated with patient-reported symptoms (e.g. pain or discomfort) and may impede normal oral function. In this study the activity of 11 (antimicrobial and/or antifungal) agents in a dental adhesive carrier against two strains of C. albicans was assessed. In conventional minimal inhibitory concentration (MIC) assays, C. albicans were resistant to histatin 5 and lactoferricin B, yet very susceptible to SMAP28; susceptible to long chain bases sphingosine, dihydrosphingosine, and phytosphingosine; and susceptible to anti-fungal agents amphotericin B, chlorhexidine dihydrochloride, chlorhexidine gluconate, fluconazole, and nystatin. However, in 1% dental adhesive (final concentration) C. albicans were resistant to histatin 5, lactoferricin B, SMAP28, sphingosine, dihydrosphingosine, and phytosphingosine suggesting that the components in denture adhesive may inactivate local innate immune factors in the oral cavity possibly predisposing users to fungal infections in relation to their dental prostheses. In MIC assays in 1% dental adhesive (final concentration) C. albicans were susceptible (p value < 0.05) to amphotericin B, chlorhexidine, dihydrochloride, chlorhexidine gluconate, fluconazole, and nystatin strongly suggesting that these anti-fungal agents could be candidates for inclusion in denture adhesive formulations, and also be used as a prescribed topical treatment in individuals with fungal infections of the oral mucosa.

The aim of this study was to develop a new single-part healing system for self-healing composites. The self-healing approach to composite repair has been developed in the last two decades and means that a damaged area can be repaired by material already housed within the structure. The background and development of self-healing has been reviewed. The two main self-healing mechanisms are discussed. To date only two part self healing systems have been examined. These require diffusion of the separate constituents to a single location in order to effect cure and restore strength. Single part adhesives do not have this disadvantage and are therefore very attractive. Several candidate single-part adhesive or resin systems were considered and discussed according to the critical requirements of a self-healing system. A series of experiments was undertaken to evaluate the possibility of candidate adhesive systems being effective for self-healing by focusing on the determination of storage stability and bonding efficiency. The results of storage stability testing showed that the stability of cyanoacrylate and polyurethane adhesives was poor. However silane and polystyrene cements showed good storage stability. Very low bonding efficiency was achieved with polystyrene cement but a 22% strength recovery was obtained with the silane 3-[tris(trimethylsiloxy)silyl]-propylamine. Suggestions for further research into single-part healing systems are also given.

<p>Within the European space programme, a new upper stage engine (Vinci) for the Ariane 5 launcher is being developed, and the Volvo Aero Corporation (VAC) is contributing with tur-bines for the fuel turbopumps. This MSc thesis investigates the possibility of designing the Turbine Exhaust Duct (TED) of the Vinci-engine in a carbon fibre composite material with adhesively attached titanium flanges. The focus of the project has been on stress analyses of the adhesive joints using Finite Element Methods (FEM), more specifically by using a cohe-sive zone material (CZM) to model the adhesive layer. Analysing adhesive joints is complex and an important part of the work has been to develop and concretise analysis methods for future use within VAC.</p><p>To obtain the specialised material parameters needed for a CZM analysis, FE-models of ten-sile test specimens were analysed and the results compared to those of equivalent experimen-tal tensile tests. These parameters were then used when analysing the TED geometry with load cases specified to simulate the actual operation conditions of the Vinci engine. Both two-dimensional axisymmetric and fully three-dimensional models were analysed and, addition-ally, a study was performed to evaluate the effect of cryogenic temperatures on the strength of the joint.</p><p>The results show that the applied thermal and structural loading causes local stress concentra-tions on the adhesive surface, but the stresses are not high enough to cause damage to the joint if a suitable joint design is used. Cryogenic temperatures (-150 °C) caused a significant strength reduction in the tensile specimens, partially through altered adhesive properties, but no such severe effects were seen in the temperature-dependent FE-analyses of the TED. It should be pointed out however, that some uncertainties about the material parameters exist, since these were obtained in a rather unconventional way. There are also several other impor-tant questions, beside the strength of the adhesive joint, that need to be answered before a metal-composite TED can be realised.</p> / <p>Volvo Aero deltar i utvecklingen av Vinci, en ny motor till det övre steget i den europeiska Ariane 5-raketen. Detta examensarbete behandlar möjligheten att tillverka ett turbinutlopp (TED) till vätgasturbinen i Vinci-motorn i kompositmaterial med flänsar i titan för att på så sätt uppnå en viktbesparing gentemot den tidigare konstruktionen i gjuten Inconel 718. Fokus har legat på att analysera hållfastheten i de limfogar som är tänkta att sammanfoga huvudröret med flänsarna, genom analyser med finita elementmetoden (FEM). Ett viktigt syfte har även varit att, för Volvo Aeros räkning, samla praktiska erfarenheter angående numerisk analys av limfogar, särskilt med användning av kohesiva zon-element för att modellera limfogen.</p><p>FEM-analyser har gjorts av provstavsmodeller, där resultaten sedan jämförts med experimen-tella dragprovsresultat för att ta fram lämpliga material- och modelleringsparametrar för ana-lys med kohesiva zonelement. Därefter tillämpades dessa parametrar i analyser av den verkli-ga TED-geometrin med relevanta lastfall framtagna för att simulera driftsförhållandena i Vin-ci-motorn. Lastfallsanalyser med både tvådimensionellt axisymmetriska och tredimensionella geometrimodeller genomfördes, liksom uppskattningar av limfogens styrka vid kryogena driftstemperaturer.</p><p>Resultaten pekar entydigt mot att en limfog med en ändamålsenlig tvärsnittsgeometri skulle hålla för de angivna lasterna utan att ta skada. De spänningskoncentrationer som uppstår ger lokalt höga spänningar i limmet, men inte på nivåer som skulle kunna orsaka brott. Det finns dock en viss osäkerhet angående riktigheten i materialparametrarna då en något okonventio-nell metod användes för att ta fram dessa. Flera stora frågor finns fortfarande kvar att besvara innan en metall-komposit konstruktion kan realiseras, inte minst hur flödeskammarens kom-plicerade geometri skall kunna tillverkas i kompositmaterial.</p>

<p>This master thesis in physics mainly treats Auger spectroscopy of interfaces that has been adhesively bond together with so called controlled delaminating materials (CDM). CDM is a new technology which involves adhesives with the distinctive property that they by the appliance of electricity can be released from a substrate. The reason for using Auger spectroscopy was that it gives a surface sensitive view of the chemical composition of the samples examined and this was believed to give hints of the mechanisms behind loss of adhesion. The samples were so called laminates which is an aluminium foil, CDM adhesive, aluminium foil structure. As expected Auger spectroscopy produced some promising results, especially regarding the breakdown of a certain anion contained into the examined CDM adhesive. This awoke new questions regarding how this anion was decomposed and the idea that it could be due to hydrolysis took form. The by far most important result within this work is that the anion breaks down. This could lead to the formation of hydrofluoric acid if this breakdown in fact is due to hydrolysis and the hydrofluoric acid could then react with the aluminium causing loss of adhesion. This could be the good starting point of a continuing work on CDM.</p>

Natural fibers are gaining popularity as reinforcement materials for thermoset resins over the last two decades. Natural fibers are inexpensive, abundant, renewable and environmentally friendly. Kenaf fibers are one of the natural fibers that can potentially be used for reinforcing unsaturated polyester (UPE). As a polymer matrix, UPE enjoys a 40% market share of all the thermoset composites. This widespread application is due to many favorable characteristics including low cost, ease of cure at room temperature, ease of molding, a good balance of mechanical, electrical and chemical properties. One of the barriers for the full utilization of the kenaf fiber reinforced UPE composites, however, is the poor interfacial adhesion between the natural fibers and the UPE resins. The good interfacial adhesion between kenaf fibers and UPE matrix is essential for generating the desired properties of kenaf-UPE composites for most of the end applications. Use of a coupling agent is one of the most effective ways of improving the interfacial adhesion. In this study, six novel effective coupling agents were developed and investigated for kenaf-UPE composites: DIH-HEA, MFA, NMA, AESO-DIH, AESO-MDI, and AESO-PMDI. All the coupling agents were able to improve the interfacial adhesion between kanaf and UPE resins. The coupling agents were found to significantly enhance the flexural properties and water resistance of the kenaf-UPE composites. Fourier transform infrared spectroscopy (FTIR) confirmed all the coupling agents were covalently bonded onto kenaf fibers. Scanning electron microscopy (SEM) images of the composites revealed the improved interfacial adhesion between kanaf fibers and UPE resins. / Graduation date: 2013

This master thesis in physics mainly treats Auger spectroscopy of interfaces that has been adhesively bond together with so called controlled delaminating materials (CDM). CDM is a new technology which involves adhesives with the distinctive property that they by the appliance of electricity can be released from a substrate. The reason for using Auger spectroscopy was that it gives a surface sensitive view of the chemical composition of the samples examined and this was believed to give hints of the mechanisms behind loss of adhesion. The samples were so called laminates which is an aluminium foil, CDM adhesive, aluminium foil structure. As expected Auger spectroscopy produced some promising results, especially regarding the breakdown of a certain anion contained into the examined CDM adhesive. This awoke new questions regarding how this anion was decomposed and the idea that it could be due to hydrolysis took form. The by far most important result within this work is that the anion breaks down. This could lead to the formation of hydrofluoric acid if this breakdown in fact is due to hydrolysis and the hydrofluoric acid could then react with the aluminium causing loss of adhesion. This could be the good starting point of a continuing work on CDM.

Within the European space programme, a new upper stage engine (Vinci) for the Ariane 5 launcher is being developed, and the Volvo Aero Corporation (VAC) is contributing with tur-bines for the fuel turbopumps. This MSc thesis investigates the possibility of designing the Turbine Exhaust Duct (TED) of the Vinci-engine in a carbon fibre composite material with adhesively attached titanium flanges. The focus of the project has been on stress analyses of the adhesive joints using Finite Element Methods (FEM), more specifically by using a cohe-sive zone material (CZM) to model the adhesive layer. Analysing adhesive joints is complex and an important part of the work has been to develop and concretise analysis methods for future use within VAC. To obtain the specialised material parameters needed for a CZM analysis, FE-models of ten-sile test specimens were analysed and the results compared to those of equivalent experimen-tal tensile tests. These parameters were then used when analysing the TED geometry with load cases specified to simulate the actual operation conditions of the Vinci engine. Both two-dimensional axisymmetric and fully three-dimensional models were analysed and, addition-ally, a study was performed to evaluate the effect of cryogenic temperatures on the strength of the joint. The results show that the applied thermal and structural loading causes local stress concentra-tions on the adhesive surface, but the stresses are not high enough to cause damage to the joint if a suitable joint design is used. Cryogenic temperatures (-150 °C) caused a significant strength reduction in the tensile specimens, partially through altered adhesive properties, but no such severe effects were seen in the temperature-dependent FE-analyses of the TED. It should be pointed out however, that some uncertainties about the material parameters exist, since these were obtained in a rather unconventional way. There are also several other impor-tant questions, beside the strength of the adhesive joint, that need to be answered before a metal-composite TED can be realised. / Volvo Aero deltar i utvecklingen av Vinci, en ny motor till det övre steget i den europeiska Ariane 5-raketen. Detta examensarbete behandlar möjligheten att tillverka ett turbinutlopp (TED) till vätgasturbinen i Vinci-motorn i kompositmaterial med flänsar i titan för att på så sätt uppnå en viktbesparing gentemot den tidigare konstruktionen i gjuten Inconel 718. Fokus har legat på att analysera hållfastheten i de limfogar som är tänkta att sammanfoga huvudröret med flänsarna, genom analyser med finita elementmetoden (FEM). Ett viktigt syfte har även varit att, för Volvo Aeros räkning, samla praktiska erfarenheter angående numerisk analys av limfogar, särskilt med användning av kohesiva zon-element för att modellera limfogen. FEM-analyser har gjorts av provstavsmodeller, där resultaten sedan jämförts med experimen-tella dragprovsresultat för att ta fram lämpliga material- och modelleringsparametrar för ana-lys med kohesiva zonelement. Därefter tillämpades dessa parametrar i analyser av den verkli-ga TED-geometrin med relevanta lastfall framtagna för att simulera driftsförhållandena i Vin-ci-motorn. Lastfallsanalyser med både tvådimensionellt axisymmetriska och tredimensionella geometrimodeller genomfördes, liksom uppskattningar av limfogens styrka vid kryogena driftstemperaturer. Resultaten pekar entydigt mot att en limfog med en ändamålsenlig tvärsnittsgeometri skulle hålla för de angivna lasterna utan att ta skada. De spänningskoncentrationer som uppstår ger lokalt höga spänningar i limmet, men inte på nivåer som skulle kunna orsaka brott. Det finns dock en viss osäkerhet angående riktigheten i materialparametrarna då en något okonventio-nell metod användes för att ta fram dessa. Flera stora frågor finns fortfarande kvar att besvara innan en metall-komposit konstruktion kan realiseras, inte minst hur flödeskammarens kom-plicerade geometri skall kunna tillverkas i kompositmaterial.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 201-208). Also available on the Internet.