Orientador: Lauro Cardoso Villela / Banca: Maria Auxiliadora Junho de Araújo / Banca: Rolf Rode / Resumo: O objetivo deste estudo foi desenvolver em silicona, uma escala de tonalidades de pele humana. Foram confeccionados vinte e sete corpos de prova em silicona acética (Silastic 732 RTV), pigmentados com óxidos de ferro e dióxido de titânio. A quantidade da silicona acética manteve-se constante (duas gramas) em todos os corpos de prova, e os pigmentos foram misturados a ela, em várias proporções, até a obtenção das vinte e sete diferentes tonalidades. A partir da comparação dos corpos de prova, com a cor da pele de quarenta e um indivíduos, foram selecionados os cinco corpos de prova com as tonalidades que mais se igualavam à cor da pele dos mesmos, compondo assim, um guia de tonalidades. Variações nas quantidades dos pigmentos utilizados permitiram a obtenção de novas tonalidades. Com a metodologia empregada, foi possível desenvolver uma escala de tonalidades de pele que poderá facilitar a definição do tom da pele do paciente, quando da confecção de próteses faciais em silicona, permitindo economia de tempo e de material no momento da seleção da cor / Abstract: The objective of this paper was to develop one silicone guide for human skin shades. Twenty-seven samples were manufactured in acetic silicone rubber (Silastic 732 RTV) pigmented with iron oxides and titanium dioxide. The qua ntity of acetic silicone rubber used in each specimen was kept constant (two grams) and the pigments were mixed to it in several proportions until the obtention of twenty-seven different shades. Through the comparison of the color of each sample with the skin color of forty-one individuals were selected the five samples which shades best matched the individuals' skin colar, determining in this way, a shade guide. Variations in the quantity of pigments used permited the obtention of new shades. With the employed methodology it was possible to develop a shade guide that can facilitate the definition of the patient's skin color when making facial prostheses in silicone allowing economy of time and material at the moment of color selection / Mestre

An important consideration for spacecraft material selection is the space environment that the spacecraft will be operating in. Two features of the space environment that drive material selection are material outgassing and the presence of atomic oxygen in low Earth orbit (LEO). Materials that are considered for use in space are tested to be able to understand how they’ll outgas on orbit and how they’ll respond to interactions with atomic oxygen. However, testing to understand how atomic oxygen interaction with a material will affect how the material will outgas is rare and not standardized. This thesis used a vacuum chamber intended to determine the outgassing properties of materials using ASTM E595 and another vacuum chamber intended to determine how materials are affected by atomic oxygen using ASTM E2089 to determine how atomic oxygen affects outgassing of silicones, which are of interest as atomic oxygen can alter the chemical composition of the surface of silicones. CV-2500, CV2-2289- 1, and SCV2-2590, three silicone elastomers that are products of NuSil Technology LLC, were tested. Significant trends in atomic oxygen reducing the amount of matter outgassed from these three materials were observed. This can be explained by the conversion of the surface of silicone to silica, which was confirmed using Fourier Transform Infrared (FTIR) spectroscopy. Retesting of these three materials in a chamber designed for ASTM E595 with a temperature measurement system capable of adhering to ASTM E595 to confirm the results of this thesis with more confidence in uniform temperature exposure is recommended.

O presente estudo avaliou próteses vasculares de pequeno calibre feitas de polidimetilsiloxano (PDMS) com reforço de poliéster implantadas em aorta de coelhos através de fluoroscopia. Os objetivos do estudo foram: (1) analisar tubo de PDMS com reforço de poliéster implantado em aorta de coelhos como possível material para prótese vascular, (2) avaliar a patência das próteses através de fluoroscopia, (3) avaliar a condição de implante cirúrgico; (4) avaliar o comportamento macroscópico biológico do implante e (5) analisar o modelo experimental proposto. Próteses vasculares de PDMS foram implantadas na aorta infrarrenal de 64 coelhos cedidos pelo biotério da Faculdade de Medicina da Univesidade de São Paulo. Os exames de fluoroscopia foram realizados em até 150 dias após implantação cirúrgica. As próteses de PDMS foram classificadas em ocluídas e patentes, sendo essas sub-classificadas em diferentes graus de estenose. O tempo de clampeamento da aorta foi aferido durante os procedimentos cirúrgicos. De maneira amostral peças foram encaminhadas para microscopia eletrônica para verificação de endotelização das próteses. As análises estatísticas foram feitas através de teste t-Studant, teste ANOVA e Kaplan-Meier. Dos 64 animais que receberam a prótese, trinta (46,88%) apresentaram boa evolução clínica, vinte e três (35,94%) morreram e onze (17,18%) apresentaram paraplegia de membros posteriores. A patência das próteses em 30 dias foi de 87% (±6,7), em 60 dias foi de 73% (±9,3), em 90 dias foi de 57% (±11) e em 120 dias foi de 48% (±12). Cinquenta por cento (oito) das próteses patente não apresentaram nenhum grau de estenose, 35,5% (seis) apresentaram cinquenta por cento ou menos de estenose e 12,5% (dois) apresentaram estenose entre cinquenta e setenta por cento. Nenhum animal apresentou estenose maior que 70%. O tempo médio de clampeamento da aorta foi de 52 minutos. Não houve diferença significante nem na associação entre tempo de clampeamento da aorta e a evolução clínica dos animais (p=0,67) nem na associação entre o tempo de clampeamento e a patência das próteses (t=1,35; p=0,18). As peças encaminhadas para microscopia apresentaram crescimento endotelial a partir do vaso nativo em direção à prótese de PDMS. Foi possível concluir com este estudo que o PDMS demonstrou-se um material adequado para futuras pesquisas no ramo de próteses vasculares e que o uso da fluoroscopia na avaliação dessas próteses foi de fundamental importância na determinação da patência dos implantes / The present study evaluated small caliber vascular prostheses made of polydimethylsiloxane (PDMS) with polyester reinforcement implanted in the aorta of rabbits by fluoroscopy. The study objectives were: (1) analyze PDMS tube with polyester reinforcement implanted in the aorta of rabbits as possible material for vascular prosthesis, (2) assess the patency of the prosthesis through fluoroscopy, (3) assess the condition of surgical implant (4) evaluate the macroscopic behavior of biological implant and (5) analyze the proposed experimental model. Vascular prostheses were implanted in PDMS infrarenal aorta of 64 rabbits assigned by the animal house of the Faculty of Medicine of the University of São Paulo. Fluoroscopic examinations were performed within 150 days after surgical implantation. The prosthesis of PDMS were classified into occluded and patents, these being sub-classified into different degrees of stenosis. The time of aortic clamping was measured during surgical procedures. Sample pieces were sent for electron microscopy to check endothelialization of prostheses. Statistical analyzes were performed using t-test Studant, ANOVA and Kaplan-Meier. Of the 64 animals that received the prosthesis, thirty (46.88%) showed clinical improvement, twenty-three (35.94%) died and eleven (17.18%) had paraplegia of hind limbs. The patency of the prosthesis in 30 days was 87% (± 6.7), at 60 days was 73% (± 9.3), at 90 days was 57% (± 11) and at 120 days was 48 % (± 12). Fifty percent (eight) of the prosthesis patent did not present any degree of stenosis, 35.5% (six) had fifty percent or less of stenosis and 12.5% (two) had stenosis between fifty and seventy percent. No animal showed stenosis greater than 70%. The mean aortic clamping was 52 minutes. There was no significant difference in the association between duration of aortic clamping and clinical evolution of animals (p = 0.67) nor the association between clamping time and patency of the prosthesis (t = 1.35, p = 0.18). The parts sent for microscopy showed endothelial growth from the native vessel toward the prosthesis PDMS. It can be concluded from this study that the PDMS proved to be a suitable material for future research in the field of vascular prostheses and the use of fluoroscopy in the evaluation of these prostheses was of fundamental importance in determining the patency of the implants

O presente estudo avaliou próteses vasculares de pequeno calibre feitas de polidimetilsiloxano (PDMS) com reforço de poliéster implantadas em aorta de coelhos através de fluoroscopia. Os objetivos do estudo foram: (1) analisar tubo de PDMS com reforço de poliéster implantado em aorta de coelhos como possível material para prótese vascular, (2) avaliar a patência das próteses através de fluoroscopia, (3) avaliar a condição de implante cirúrgico; (4) avaliar o comportamento macroscópico biológico do implante e (5) analisar o modelo experimental proposto. Próteses vasculares de PDMS foram implantadas na aorta infrarrenal de 64 coelhos cedidos pelo biotério da Faculdade de Medicina da Univesidade de São Paulo. Os exames de fluoroscopia foram realizados em até 150 dias após implantação cirúrgica. As próteses de PDMS foram classificadas em ocluídas e patentes, sendo essas sub-classificadas em diferentes graus de estenose. O tempo de clampeamento da aorta foi aferido durante os procedimentos cirúrgicos. De maneira amostral peças foram encaminhadas para microscopia eletrônica para verificação de endotelização das próteses. As análises estatísticas foram feitas através de teste t-Studant, teste ANOVA e Kaplan-Meier. Dos 64 animais que receberam a prótese, trinta (46,88%) apresentaram boa evolução clínica, vinte e três (35,94%) morreram e onze (17,18%) apresentaram paraplegia de membros posteriores. A patência das próteses em 30 dias foi de 87% (±6,7), em 60 dias foi de 73% (±9,3), em 90 dias foi de 57% (±11) e em 120 dias foi de 48% (±12). Cinquenta por cento (oito) das próteses patente não apresentaram nenhum grau de estenose, 35,5% (seis) apresentaram cinquenta por cento ou menos de estenose e 12,5% (dois) apresentaram estenose entre cinquenta e setenta por cento. Nenhum animal apresentou estenose maior que 70%. O tempo médio de clampeamento da aorta foi de 52 minutos. Não houve diferença significante nem na associação entre tempo de clampeamento da aorta e a evolução clínica dos animais (p=0,67) nem na associação entre o tempo de clampeamento e a patência das próteses (t=1,35; p=0,18). As peças encaminhadas para microscopia apresentaram crescimento endotelial a partir do vaso nativo em direção à prótese de PDMS. Foi possível concluir com este estudo que o PDMS demonstrou-se um material adequado para futuras pesquisas no ramo de próteses vasculares e que o uso da fluoroscopia na avaliação dessas próteses foi de fundamental importância na determinação da patência dos implantes / The present study evaluated small caliber vascular prostheses made of polydimethylsiloxane (PDMS) with polyester reinforcement implanted in the aorta of rabbits by fluoroscopy. The study objectives were: (1) analyze PDMS tube with polyester reinforcement implanted in the aorta of rabbits as possible material for vascular prosthesis, (2) assess the patency of the prosthesis through fluoroscopy, (3) assess the condition of surgical implant (4) evaluate the macroscopic behavior of biological implant and (5) analyze the proposed experimental model. Vascular prostheses were implanted in PDMS infrarenal aorta of 64 rabbits assigned by the animal house of the Faculty of Medicine of the University of São Paulo. Fluoroscopic examinations were performed within 150 days after surgical implantation. The prosthesis of PDMS were classified into occluded and patents, these being sub-classified into different degrees of stenosis. The time of aortic clamping was measured during surgical procedures. Sample pieces were sent for electron microscopy to check endothelialization of prostheses. Statistical analyzes were performed using t-test Studant, ANOVA and Kaplan-Meier. Of the 64 animals that received the prosthesis, thirty (46.88%) showed clinical improvement, twenty-three (35.94%) died and eleven (17.18%) had paraplegia of hind limbs. The patency of the prosthesis in 30 days was 87% (± 6.7), at 60 days was 73% (± 9.3), at 90 days was 57% (± 11) and at 120 days was 48 % (± 12). Fifty percent (eight) of the prosthesis patent did not present any degree of stenosis, 35.5% (six) had fifty percent or less of stenosis and 12.5% (two) had stenosis between fifty and seventy percent. No animal showed stenosis greater than 70%. The mean aortic clamping was 52 minutes. There was no significant difference in the association between duration of aortic clamping and clinical evolution of animals (p = 0.67) nor the association between clamping time and patency of the prosthesis (t = 1.35, p = 0.18). The parts sent for microscopy showed endothelial growth from the native vessel toward the prosthesis PDMS. It can be concluded from this study that the PDMS proved to be a suitable material for future research in the field of vascular prostheses and the use of fluoroscopy in the evaluation of these prostheses was of fundamental importance in determining the patency of the implants

L’hydrosilylation d’alcènes est une réaction clé pour la synthèse d’huiles silicones fonctionnelles et d’élastomères silicones nécessite un catalyseur. Industriellement, le platine est utilisé or le coût important de ce métal motive la recherche de catalyseurs alternatifs plus compétitifs, notamment à base de métaux non précieux. Les travaux ont débuté sur des systèmes développés précédemment au laboratoire à base de cobalt et de nickel à haut degré d’oxydation et de ligands dicétones. Les cinétiques de réticulation ont été également suivies aussi bien par des mesures qualitatives d’arrêt d’agitation que par des mesures de rhéologie ou de chaleur de réaction par DSC. Ces catalyseurs sont actifs et robustes pour la réticulation. A la suite, des catalyseurs à base de cobalt portant en particulier des ligands amidures ont été étudiés. Associés à un ligand bidentate (P,N), les systèmes catalytiques sont compétitifs au platine de Karstedt pour l’hydrosilylation sélective d’alcènes. Ces catalyseurs réalisent également la réticulation d’huiles silicones à relativement basse température (20 min à 90°C). Un homologue au fer s’est également montré actif pour la réticulation d’huiles silicones démontrant la faisabilité d’une voie catalytique d’hydrosilylation à partir de complexes de fer non toxiques et robustes / Alkene hydrosilylation is a major tool for the synthesis of functionalized silicone oils and silicone elastomers and is catalyzed by transition metal complexes. Industrially, Platinum complexes are used. However, high and volatile cost and rarity of precious metals lead to the development of competitive alternative systems, especially catalysts based on non-precious transition metals. First, Nickel and Cobalt high-oxidation-state complexes bearing diketone ligands were studied. Those systems had been previously developed in the laboratory and the study has been completed. Crosslinking kinetics were followed by qualitative measures of “stop-stirring” time and by rheology and thermal analysis (DSC). Those catalysts are active over oxygen and stable for silicone-oil crosslinking. Then, Cobalt Catalysts bearing amido-based ligands were studied. When associated with a ligand (phosphino pyridine P,N), those systems are competitive with the Karstedt catalyst (Pt) for selective alkene hydrosilylation. They also allow for silicone-oil crosslinking at relatively low temperature (20 min at 90 °C). Finally, a homologous complex based on Iron was synthesized and showed activity for silicones’ crosslinking evidencing the feasibility of a catalytic hydrosilylation pathway from non-toxic and robust iron complexes.

Made available in DSpace on 2014-06-11T19:35:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-27Bitstream added on 2014-06-13T19:44:51Z : No. of bitstreams: 1 santos_dm_dr_araca.pdf: 1533021 bytes, checksum: 248d1fb3f8ac9369529ebf0ea03f0654 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente estudo teve por objetivo avaliar a influência de dois pigmentos (pó de cerâmica e tinta a óleo) e um opacificador (sulfato de barium) sobre as propriedades físicas de estabilidade de cor, dureza, absorção e solubilidade do silicone facial MDX4-4210, submetido ao envelhecimento acelerado. Para a confecção das amostras, foram utilizadas 2 matrizes metálicas em alumínio, contendo em seu interior 10 compartimentos circulares com 45mm de diâmetro apresentando estes, em uma matriz, uma espessura de 2mm para os testes de estabilidade de cor e dureza e, na outra, 1mm para os ensaios de absorção e solubilidade. Foram confeccionadas 120 amostras, metade para os ensaios de análise cromática e dureza e, a outra metade, para o teste de absorção e solubilidade. As amostras destinadas para cada teste foram distribuídas em seis grupos, incolor (G1), incolor com opacificador (G2), cerâmica (G3), cerâmica com opacificador (G4), óleo (G5), óleo com opacificador (G6). Após a obtenção das amostras, a análise cromática inicial foi verificada por meio da análise visual e da espectrofotometria de reflexão. Os ensaios de dureza foram realizados com auxílio de um durômetro Shore A. Os testes de absorção e solubilidade foram realizados por meio de um dessecador no qual as amostras permaneceram neste ambiente em estufa à temperatura de 37±2°C, sendo pesadas diariamente até obtenção de massa constante (W1); posteriormente as amostras foram submetidas ao envelhecimento seguido de nova pesagem (W2), e nova dessecação com pesagem final (W3). As amostras foram submetidas ao envelhecimento acelerado por 1008 horas, sendo os ensaios realizados nos períodos correspondentes a 252, 504 e 1008 horas. Os dados obtidos foram submetidos à ANOVA e Tukey, com significância de 5%. Pode-se observar pela análise espectrofotométrica que os grupos com opacificador apresentaram melhor... / The aim of this study was to evaluate the influence of two pigments (ceramic powder and oil paint) and one opacifier (barium sulfate) on physical properties of color stability, hardness, absorption and solubility of the facial silicone MDX4-4210 submitted to artificial aging. The replicas were fabricated in two metallic matrixes in aluminum containing 10 circular compartments with 45mm in diameter. One matrix generated specimens with 2mm in thickness for color stability and hardness evaluations while the other matrix, specimens with 1mm in thickness for absorption and solubility tests. The replicas were divided into six groups: colorless (G1), colorless with opacifier (G2), ceramic (G3), ceramic with opacifier (G4), oil (G5) and oil with opacifier (G6). Initial chromatic evaluation was performed by visual analysis and reflection spectrophotometry. The hardness tests were carried out by a Shore A durometer. The evaluations of absorption and solubility were performed through a desiccator to maintain the replicas in a stove at 37±2°C. The specimens were weighed daily until obtaining a constant mass, (W1). Then, the replicas were submitted to aging followed by a new weighing (W2) and drying with final weighing (W3). The replicas were submitted to accelerated aging during 1008 hours with evaluation after 252, 504 and 1008 hours. Data were submitted to statistical analysis by ANOVA and Tukey’s test at 5% level of significance. According to spectrophotometry, the groups with opacifier presented statistically significant better chromatic stability than the other groups. The accelerated aging generated significant chromatic alterations in all groups, except for colorless and oil groups both with opacifier. There was no statistically significant difference among the groups after aging regarding hardness, absorption and solubility. According to the results, it may be concluded that... (Complete abstract, click electronic access below)

L’objectif de ces travaux de thèse est de générer de l’amortissement à matériaux silicones, et plus particulièrement de mettre en lumière les relations entre la structure des additifs incorporés dans la base silicone et la morphologie des mélanges, ainsi que leur densité de réticulation et leurs propriétés mécaniques et dynamiques. Une première étude bibliographique a permis de sélectionner les deux types d’additifs étudiés dans nos formulations, à savoir les élastomères silicones thermoplastiques (TPS) et les résines silicones. Les propriétés mécaniques de TPS commerciaux ou synthétisés en laboratoire, seuls et en blends avec une base silicone, ont été comparés selon le taux de TPS ainsi que sa structure. Les hypothèses sur les relations structure-propriétés des différents TPS se sont appuyées sur la bibliographie. L’influence du type de peroxyde et de sa concentration dans la formulation a également été étudiée. Les copolymères silicone-urée préparés avec un diisocyanate asymétrique et non aromatique présentent les amortissements les plus intéressants, une fois mis en mélange à un taux suffisant avec une base silicone et réticulés, tandis qu’un copolymère silicone-amide original montre un amortissement moindre mais à plus basse température. Dans tous les cas, le blend possèdant une faible densité de réticulation présente donc un meilleur amortissement. La deuxième voie d’étude concerne les résines silicones, et plus particulièrement les résines de type MQ et MQQOH. Dans un premier temps, les différentes structures de résines silicones décrites dans la bibliographie et leurs méthodes de synthèse ont été sériées. Dans un deuxième temps, des mélanges ont été réalisés en variant la structure et le taux de résines. Leur influence sur la densité du réseau ainsi que sur les propriétés mécaniques des matériaux après réticulation a été observée. Afin de pouvoir valider ou invalider des hypothèses, certaines résines ont été modifiées chimiquement, avant d’être ajoutées à la base silicone. Finalement, certains paramètres de la structure des résines ont été particulièrement considérés, comme un taux d’hydroxyle faible ou une masse molaire élevée. Le taux de résine dans la base joue un rôle important puisqu’il influe sur la densité de réticulation et sur les propriétés dynamiques du matériau une fois réticulé. / This PhD work aimed at improving the damping properties of silicones materials, and more specifically at highlithing the relationships between the structure of additives in a silicone base and the morphology of the blends, as well as their crosslink density and mechanical and dynamical properties. A preliminary literature survey allowed selecting two types of additives for further formulation: thermoplastic elastomers (TPS) and silicone resins. The mechanical properties of commercial or hand-made TPS, alone or blended with a silicone base, were compared according to the structure of the TPS or its content in the blend. Hypotheses were made about the structure-properties relationships of the different TPS tested, and these hypotheses were confirmed or rejected with the help of literature. The role played by the peroxide type or content was also investigated. It appeared that poly(silicone-urea) copolymers containing non-symmetrical hard segments display better damping properties, especially when they blended at a sufficient content in the silicone base. Blends of silicone base and original silicone-amide copolymers showed lower damping properties but at lower temperature. The damping properties were enhanced when using peroxides that led to a low crosslink density. The second route relates to silicone resins, and more specifically MQ or MQQOH resins. First of all, an inventory of the different structures of silicones resins, as well as their synthesis methods, available in literature was carried out. Next, several blends were prepared by varying the structure or the content of silicone resins, and their influence on the crosslink density or mechanical properties of the final materials was investigated. Some resins were modified in order to validate or reject some hypotheses, such as the influence of the hydroxyl content in the resins or the molar mass. Among the main parameters to obtain damping silicone materials, the crosslink density, influenced by the resin content, plays a major role in the dynamic properties of the crosslinked material.

O objetivo deste trabalho é desenvolver e testar uma técnica de medição de gramatura de silicone para o processo de fabricação de protetores de papéis para papéis auto-adesivos, de modo a contribuir com a viabilidade da aplicação de emulsão de silicone à base d'água em substituição ao silicone à base de solvente. A técnica usada foi a Espectroscopia por Infravermelho próximo. As técnicas que utilizam o infravermelho próximo já têm sido usadas em análises em linha por mais de 25 anos. Os resultados obtidos foram validados por fluorescência de raios-X e a técnica de infravermelho pode ser considerada como alternativa na aplicação de emulsão de silicone à base d'água.

Ice buildup on structures leads to problems that include reduced performance, structural damage and power outages. It is therefore important to limit the energy required for removal of ice from substrates to minimize buildup. Understanding the mechanism of ice adhesion and its dependence on variables like coating thickness, stiffness, surface free energy and morphology is critical for minimizing adhesion. Despite several developments in “icephobic” coatings, which are those that have low ice adhesion, it is important to understand adhesion on the fundamental level to make way for advanced coatings. To do so, a study has been carried out that explores key variables affecting ice adhesion using a commercially available silicone, Sylgard 184®. Sylgard 184 is a two-part, platinum cured silicone elastomer available from Dow Corning with good physical and chemical stability and is used in widely diverse research studies. The thermodynamic work of ice adhesion is related to the receding contact angle θ_r of water by Equation 1. wa≈ γ_w (1+cos⁡ θ_r) Eq 1. where γ_w is the surface tension of water. Considering an elastomeric substrate and ice as a rigid cylindrical adherent, the Kendall modelcan be adapted to relate peak removal force (Pc) with work of adhesion (wa), modulus (K), thickness (t), and radius (a) according to Equation 2. Pc ∝ πa^2 ((2wa K)/t)^(1⁄2) Eq. 2 Considering these relationships, hydrophobic materials with low surface energies and high receding contact angles are generally predicted to show low adhesion. To begin to understand details, the force required to remove an ice cylinder from the silicone elastomer Sylgard 184 was investigated by focusing on three variables: coating thickness, modulus and cure temperature. “Cure” refers to the network formation or crosslinking within the material. The Wynne research group has previously established a surprising dependence of qR on Sylgard 184 cure temperature.In this thesis, the relationship among variables noted above was examined by measuring Pc for Sylgard coatings. Additionally, effects of test temperature on ice adhesion strength was studied. Surface characterization methods including ATR-IR (attenuated total reflectance infrared spectroscopy), DCA (Wilhelmy plate dynamic contact angles) and AFM (atomic force microscopy) were employed. In summary, defined processing conditions were found optimum for minimizing ice adhesion to Sylgard coatings.

Abstract not available