Os elásticos ortodônticos intermaxilares sintéticos vem sendo cada vez mais utilizados, sendo principalmente indicados para pacientes que apresentam hiper-sensibilidade ao látex. Afim de avaliar e comparar o comportamento de elásticos de látex e sintéticos quanto a perda de força ao longo do tempo, este estudo foi realizado tanto in vitro quanto in vivo. Para o estudo in vitro foram avaliados 15 elásticos de cada material, para cada tempo: 0, 1, 3, 12 e 24 horas. No estudo in vivo, pacientes foram avaliados (N=15), utilizando elásticos de ambos os materiais (látex e sintético), nos mesmos tempos do estudo in vitro. Os elásticos foram transferidos para a máquina de ensaios mecânicos (EMIC DL-500 MF). Os valores da força gerada foram registrados após a distensão dos elásticos a uma distância de 25mm. Foi aplicado o teste t pareado para a amostra clínica e independente para a amostra laboratorial. Foi utilizada a análise de variância (ANOVA) para verificar a variação das forças geradas entre os tempos determinados e o teste post-hoc para identificar entre quais tempos houve diferença significativa. Quanto às forças iniciais geradas (zero hora), os valores para os elásticos sintéticos foram bastante semelhantes entre os estudos laboratorial e clínico e ligeiramente superiores aos dos elásticos de látex. Nos tempos subsequentes, as forças geradas pelos elásticos de látex apresentaram valores superiores. Em relação à degradação do material, ao final de 24 horas, maior percentual foi observado para os elásticos sintéticos, tanto in vitro quanto in vivo. A maior queda nos valores das forças liberadas pelos elásticos de ambos os materiais e nos estudos clínico e laboratorial, ocorreu entre os tempos de 0 e 1 hora, seguida de uma queda gradativa e progressiva até o tempo de 24 horas. Os elásticos de látex apresentaram um comportamento mais estável no período estudado em relação aos sintéticos, em ambos os estudos. / Synthetic intermaxillary orthodontic elastics are being increasingly used and they are primarily indicated for patients with hypersensitivity to latex. In order to evaluate and compare the behavior of latex and synthetic elastics, as the loss of strength, over time, this study was conducted both in vitro and in vivo. For the in vitro study, 15 of each elastic material was evaluated for each time: 0, 1, 3, 12 and 24 hours. For the in vivo study, patients were evaluated (N = 15) using both elastic materials (latex and synthetic) at the same times settled in vitro study. The rubber bands were transferred to the testing machine (EMIC DL-500 MF). The values of the force were recorded after stretching the elastic to a length of 25mm. Matched to the clinical and independent for laboratory sample t test was applied. Analysis of variance (ANOVA) was used to check the variation of the forces generated between those determined times and the post-hoc test to identify between which times were marked difference . As regards the initial forces (time zero), the values for synthetic elastic were quite similar between laboratory and clinical studies and slightly higher than the latex elastic. In subsequent times, the forces generated by the latex elastic showed higher values. Regarding the material degradation at the end of 24 hours, the highest percentage was observed for synthetic elastic, both in vitro and in vivo. The largest drop in the values of forces unleashed by the elastic of both materials and the clinical and laboratory studies occurred between times of 0 and 1 hour, followed by a gradual decreases until the time of 24 hours. The latex elastic had a more stable behavior during the period studied compared with synthetic, in both studies.

Para confeccionar próteses faciais e reabilitar aqueles pacientes com perdas anatômicas, são empregados diversos materiais, destacando-se entre estes os flexíveis,devido á semelhança estética que apresentam com a pele humana. O padrão de qualidade dos materiais é liderado por produtos estrangeiros, tornando difícil a obtenção e, por tanto, a aplicação dos mesmos em território nacional. Devido à necessidade de se ter materiais nacionais com qualidade semelhante aos importados, este trabalho mensurou dois materiais, a resina resiliente CLASSIFLEX e o silicone médico ORTHO PAUER, ambos de produção nacional, seguindo as normas da ASTM (American Standard for testing materiais). Foram testadas dureza Shore A, resistência ao rasgamento, resistência a tração e alongamento de ruptura. Os valores obtidos foram analisados estatisticamente e comparados entre sim. Os valores de resistência a tração, resistência ao rasgamento e dureza Shore A, dos materiais testados foram baixos quando comparados com os valores encontrados em outras pesquisas .Os valores de Alongamento de ruptura se encontram dentro dos valores aceitáveis para matérias de uso em reabilitação buco maxilo facial. / To fabricate and create facial prosthesis for those patients with anatomical loss, maxillo facial protesiologist use differet materials. Flexible materials has being used mostly because of their aesthetic similarity with the skin. The standard for quality in prostethic materilas is led by foreign products, making it difficult to obtain and apply these materials in national territory. Due to the necessity of giving new and better materilas the CLASSIFLEX resilient resin and the ORTHO PAUER medical silicone, both of domestic production, were selected to test the fisical properties of: Shore A hardness, elongation, tensile strength and tear strenght. The specimens were made following the parameters indicated by the ASTM and each test was performed. The values obtained were analyzed statistically and compared. The results obtained may conclude that the physical properties of tensile srtrenght, tear strenght and Shore A hardness were low when compared with the results observed in other similar studies. The values obtained from the elongation test shows similarity of other values obtained by past studies.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2015-12-04T14:43:43Z No. of bitstreams: 1 thaianadamacenocunha.pdf: 1265962 bytes, checksum: 6d8fb90304d78d671faf48a4a00e64e5 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2015-12-07T03:22:42Z (GMT) No. of bitstreams: 1 thaianadamacenocunha.pdf: 1265962 bytes, checksum: 6d8fb90304d78d671faf48a4a00e64e5 (MD5) / Made available in DSpace on 2015-12-07T03:22:42Z (GMT). No. of bitstreams: 1 thaianadamacenocunha.pdf: 1265962 bytes, checksum: 6d8fb90304d78d671faf48a4a00e64e5 (MD5) Previous issue date: 2015-04-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo deste estudo foi mensurar a alteração dimensional de uma silicona por condensação através de um paquímetro digital (Mitutuyo), de um estéreo microscópio (Olympus) e de uma máquina de medição tridimensional por coordenadas (Mitutuyo). Foram realizadas 4 moldagens através de um dispositivo específico com a silicona por condensação pesada e leve Speedex (Coltene/Vigodent). Em cada um dos 4 moldes 4 distâncias foram mensuradas pelos 3 instrumentos, em 4 tempos distintos: no momento da remoção do molde e após 30min, 1h e 7 dias. As médias das mensurações foram submetidas ao teste estatístico Kruskal-Wallis com nível de significância de 5%. Os resultados mostraram diferenças significantes entre as alterações dimensionais verificadas por cada um dos instrumentos de medição, as mensurações realizadas pelo paquímetro digital e pela máquina de medição tridimensional por coordenadas apresentaram alterações dimensionais significantes nos 4 tempos testados, enquanto as pelo estéreo microscópio não apresentaram diferença significante nos 4 tempos. Concluiu-se que as alterações dimensionais verificadas nos moldes da silicona por condensação testada obtidas através de cada instrumento de medição utilizado nesta pesquisa foram diferentes entre si, evidenciando que os diferentes métodos de medição utilizados podem fornecer resultados distintos, e consequentemente, indicações equivocadas. / The aim of this study was to measure the dimensional changes of a silicone condensation using a digital paquimeter (Mitutuyo), an estereomicroscope (Olympus) and a three-dimensional coordinate measuring machine (Mitutuyo). Were made 4 impressions trhough a specif device using the putty and light silicone condensation Speedex (Coltene/Vigodent). Four distances were measured at each impression through the 3 instruments at 4 different times: in the moment of removal of the die and after 30min, 1h e 7 days. The avarage of the measurements were subimitted to the statistical test Kruskal-Wallis with level of significance of 5%. The results shows significant diferences between the dimensional changes verified by each one of the measuring instruments, the measurements through the digital paquimeter and the measurements trhough the three-dimensional coordinate measuring machine showed significant dimensional changes in the 4 tested times, while the measurements through the estereomicroscope did not show significant difference in the 4 tested times. It concludes that the dimensional changes verified in the tested silicone condensation by each measurement instrument used in this study were diferente, indicating that the different measuring methods used can provide wrong results, and consequently, wrong indications.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: VST-50 (a room temperature-vulcanizing silicone (RTV) by Factor II Inc.) has long been proposed as a potential alternative material for MDX4-4210, another RTV by Dow Corning Corp. and the current material of choice for maxillofacial prosthesis. Though VST-50 has similar chemistry and flexibility as MDX4-4210, its mechanical properties is still too low for it to be used in the clinic. An improvement in the mechanical property of VST-50 is a critical step to bring the material to clinical application. Objective: To investigate the effect of AEROSIL® R 812S (colloid silica) addition on the mechanical properties of VST-50 and compared to that of MDX4-4210. Methods: The VST-50 was mixed with AEROSIL® R 812S at 2 or 4 parts per hundred parts of rubber. That material was mixed with the catalyst under vacuum. The mixture was poured onto a machined plastic mold to produce a silicone sheet 3.0 ± 0.2 mm thick. All samples were prepared by manufacturer recommended method. Testing samples were prepared and tested following ISO 37 for tensile strength, ASTM D624 for tear strength and ASTM D2240 for shore A hardness test. One way ANOVA was used to compare the groups (Alpha=0.05). Result: Significant differences (P<0.001) were found between MDX4-4210 and modified VST-50 groups. The mean value of tensile strength, tear strength and hardness of VST-50 (4phr colloid silica) were 7.43(MPa), 34.82(N/mm) and 40.4 respectively, compared to MDX4-4210 were 3.67(MPa), 5.48(N/mm) and 31.5, respectively. Conclusion: Modified VST-50 with 4phr silica revealed improved mechanical properties to use as a maxillofacial prosthetic silicone elastomer.

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study was to investigate the effect of nano ceramic fiber fillers on the physical properties of VST-50HD silicone maxillofacial prosthesis. Nano alumina fibers at 2 percent, 4-percent, and 6-percent wt were mixed into the VST-50HD silicone elastomer (Factor II Inc., Lakeside, AZ), a commercially-available poly(dimethylsiloxanes). Ten dumb-bell-shaped specimens were used to determine the tensile strength according to ISO 37:2005 and elongation at fracture. Ten trouser-shaped test pieces were used to determine the tear resistance according to ISO 34-1:2004. Shore A test method was used to measure the hardness of the material. The data collected from all quantitative studies of the modified silicones were analyzed using one-way ANOVA with concentration of nano ceramic fiber as the main variable. Specimens from VST- 50HD were also made and tested as control. Results: The mean values for tensile strength (MPa) of control group, 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers were from 3.43 ± 0.12 to 5.48 ± 0.71. Tear strength (MPa) were from 2.34 ± 0.37 to 5.01 ± 0.39. Elongations at fracture were from 699.66 ± 43.69 to 793.51 ± 57.27. Shore A hardness were from 25.76 ± 2.18 to 38.76 ± 1.83. Conclusion: There was a significant difference (p < 0.001) in the mean tensile, tear and Shore A hardness strengths between the control group and 2-percent, 4-percent, and 6-percent percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. There was a significant difference (p < 0.001) in the mean elongation at fracture between the 2-percent and control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. The properties of the experiment were all lower than the control. Further research is needed to determine the appropriate material and amount of dispersing agent, coupling agent, and determination of the hydprophilicity of the nano ceramic fiber fillers with great emphasis on the dispersing agent.

Materials which exhibit non-linear mechanical behaviors under large deformations are generally classified as “soft matter”. Elastomers represent an important class of soft materials which have wide commercial applications and isotropic non-linear behavior. In contrast, biological materials have anisotropic responses due to their heterogeneous and composite architectures. The underlying microstructure determines the arterial macroscopic behavior and is represented through constitutive models to describe the stress-strain relationships. Mechanical characterization and development of constitutive models that describe these non-linear and anisotropic properties are essential to our understanding of the structure-property relationships in these materials. In this study, we use two model systems to link the local microstructure to the overall macroscopic behaviors of soft matter. First, we delineate the roles of individual network topological factors in determining the overall macroscopic behavior of isotropic silicone elastomers using specimens fabricated with differential amounts of crosslinking. We performed mechanical experiments, within a theoretically motivated continuum mechanical framework, using a custom made planar biaxial testing instrument. These experiments demonstrate the contributions of physical entanglements and chemical crosslinks to the overall mechanical properties of silicone elastomers. Further, we show that the slip-link form of strain energy function is better suited to describe the material properties in the low to moderate regions of the stress-strain behavior. However, this model does not predict the stiffening response of elastomers at higher deformations, which is better captured using the Arruda-Boyce form of strain energy function. To explore the effects of individual topological factors on the overall network properties, we performed swelling experiments of silicone specimens in xylene and quantified variations in the polymer-solvent interaction parameter, χ, given by the Frenkel-Flory-Rehner (FFR) model. Further, we characterized the viscoelastic properties using dynamic mechanical analysis. Our results show that χ is not a constant, as assumed in the FFR model, but bears a linear relation to the equilibrium polymer volume fraction. To characterize the contribution of trapped entanglements to the overall mechanical behaviors, we use scaling laws in polymer physics and investigate the dependence of equilibrium volume fraction and experimentally obtained elastic moduli. Further, dynamic mechanical analysis demonstrated an increase in complex modulus with increase in the cross linking density. Finally, we examined variations in the uniaxial and the dynamical mechanical properties of silicone elastomers with storage time. Our results show that the time dependent increase in the modulus correlated with the formation of slip-links in the samples aged for a significantly long time in air. Together, these comprehensive studies show the importance of individual network features which affect the overall macroscopic properties of elastomers. Second, we use a multilayered and composite arterial model system to explore the passive material properties of arteries due to anisotropic layouts of extracellular matrix proteins, collagen and elastin. We characterized the mechanical properties of diseased human ascending thoracic aortic dissected (TAD) tissues, obtained from consenting patients undergoing emergency surgical repair to replace the diseased region, using multiple biaxial tests. We fit these results to micro structurally motivated Holzapfel-Gasser-Ogden model which is frequently used in the arterial mechanics literature. Our results show a higher stiffness for TAD tissues as compared to control aorta, without the presence of atherosclerotic plaques or other arterial disease. To study the directional variation in the mechanical properties of TAD tissues, we compared the stiffness in circumferential longitudinal directions at high and low stress region of equibiaxial experimental data. We observed no differences in the stiffness of TAD tissues in the circumferential and longitudinal directions. Further, we do not see any directional variations in the ultimate tensile stress, maximum extensibility, and modulus calculated in the low stretch region of uniaxial stress-strain response in TAD tissues. Histological analysis of TAD tissues showed a decrease in elastin content and an increase in collagen content as compared to control tissues. Higher TAD tissue stiffness also correlated with reduced elastin content in the arterial walls. To investigate the strain rate dependence of measured mechanical properties we use high testing rates of 1mm/sec to show that the TAD tissues have higher stiffness in the circumferential direction as compared to longitudinal direction. Finally, we used peel experiments to quantify the rupture potential of aortic dissected tissues. Our results show that TAD tissues have reduced delamination strength between layers as compared to control aortic tissues. To the best of our knowledge, no previous study has reported the mechanical property of human TAD tissues and these are the only biomechanical results on TAD tissues reported in specimens from South Asian patients. We hope that such studies will be useful for researchers who rely on microstructure based constitutive models to accurately describe the mechanical environment of cells which are important in the remodeling of tissues and in numerical models to assess mechanical criteria which may lead to the growth or dissection of arterial tissues.

O objetivo deste estudo foi propor a utilização de um novo silicone (Bio-Skin - BS) para prótese bucomaxilofacial. Foram analisadas alteração de cor, dureza Shore A, resistência à tração, características de superfície (MEV) e composição química (EDS) frente à diferentes pigmentações e envelhecimentos. Como parâmetro de comparação foi empregado o silicone MDX4-4210. Foram obtidos 120 espécimes para cada material com formato circular e 160 em forma de haltere, a partir de matrizes metálicas de corte, os quais foram distribuídos em 4 grupos: PI - pigmentação intrínseca (pó de maquiagem); OP - opacificador (sulfato de bário, BaSO4); PIO - associação de PI + OP; SP - sem adição de PI ou OP. Em seguida, os espécimes foram distribuídos aleatoriamente em 3 subgrupos para exposição ao envelhecimento por luz natural (LN, n=10), luz ultravioleta (UV, n=10) e ausência de luz (C, n=10). O período experimental foi de 12 meses. A alteração de cor foi verificada com auxílio de espectrocolorímetro e sistema CIE L*a*b*. Para a dureza foi utilizado um durômetro Shore A e a análise da resistência à tração foi realizada em máquina universal de ensaio. As variáveis de resposta quantitativas foram mensuradas imediatamente após a obtenção dos espécimes e após o período experimental. A análise de superfície foi realizada por microscopia eletrônica de varredura (MEV) e a composição química dos silicones, por espectroscopia por energia dispersiva (EDS). Os dados foram submetidos à análise de variância e teste complementar de Tukey (p<0,05). Os resultados das análises por MEV e EDS foram apresentados em imagens e gráficos. Houve interação entre todos os fatores (p<0,05) e ambos os materiais sofreram variações em função das pigmentações e envelhecimentos. Para alteração de cor, o silicone experimental (BS) apresentou as menores variações de cor. Analisando os silicones em função da pigmentação, o MDX apresentou maiores variações com os espécimes SP e com OP envelhecidos por luz natural e luz UV. Para o BS, houve alteração significativa da cor dos espécimes SP e OP somente após o envelhecimento por LN. Os dois materiais apresentaram aumento da dureza frente a todas as condições, sendo que o silicone BS apresentou a maior variação. O silicone experimental apresentou resistência à tração superior ao MDX em todas as situações. O MDX não sofreu influência significativa na resistência à tração por nenhuma das pigmentações ou envelhecimento, exceto quanto pigmentado com pó de maquiagem e envelhecido por UV, onde houve aumento da resistência. Quanto ao silicone BS, os maiores valores de resistência à tração foram encontrados com a PI e PIO em todos os grupos de envelhecimento. Pode-se considerar que o material experimental apresentou resultados favoráveis em relação à alteração de cor, dureza Shore A e resistência à tração para sua aplicação clínica em prótese bucomaxilofacial. A associação da pigmentação intrínseca, por meio de pó de maquiagem com opacificador, protegeu o silicone da alteração de cor e promoveu alterações aceitáveis nas propriedades mecânicas dos materiais. Todos os processos de envelhecimento promoveram alterações nas propriedades dos materiais. / The aim of this study was to propose the use of a new silicone (Bio-Skin - BS) for maxillofacial prosthesis. Color change, Shore A hardness, tensile strength, surface characteristics (SEM) and chemical composition (EDS) were analyzed, regarding different pigmentation and aging methods. The MDX4-4210 silicone was used as parameter of comparison. Specimens (120 circular and 160 dumbbell-shaped) were obtained for each material, from metal cutting molds, which were divided into 4 groups: IP - intrinsic pigmentation (makeup powder); OP - opacifier (barium sulfate, BaSO4); IPO - IP + OP association; WP - without adding IP or OP. Then, the specimens were randomly divided into 3 subgroups to aging by exposure to natural light (NL, n = 10), ultraviolet light (UV, n = 10) and without light (C, n = 10). The experimental period was 12 months. The color change was observed with spectrocolorimeter and CIE L*a*b* system. For hardness we used a Shore A durometer and the analysis of tensile strength was performed in a universal testing machine. The quantitative response variables were measured immediately after obtaining the specimens and after the experimental period. The surface analysis was performed by scanning electron microscopy (SEM) and the chemical composition of silicones, by energy dispersive spectroscopy (EDS). Data were submitted to ANOVA and Tukey\'s test (p <0.05). SEM and EDS results were presented in pictures and graphics. There was interaction between all factors (p <0.05) and both materials varied depending on the pigmentation and aging methods. For color change, the experimental silicone (BS) showed the lowest color variations. Analyzing the silicones due to the pigmentation, the MDX showed higher variation with the WP and OP specimens aged in natural light and UV light. For BS, there was significant change in the color of the WP and OP specimens only after aging for NL. The two materials presented an increase in hardness front of all conditions, and the BS silicone showed the greatest variation. The experimental silicone showed superior tensile strength to MDX in all situations. The MDX was not affected in tensile strength by any pigmentation or aging, except for the group pigmented with makeup powder and aged by UV, where there was an increase of resistance. As to BS silicone, the highest tensile strength values were found for the IP and IPO in all age groups. It can be considered that the experimental material showed favorable results regarding color change, Shore A hardness and tensile strength for clinical use in maxillofacial prosthesis. The association of intrinsic pigmentation through makeup powder and opacifier, protected silicone of color change and promoted acceptable changes in mechanical properties of the materials. All the aging processes promoted changes in material properties.

O objetivo deste estudo foi propor a utilização de um novo silicone (Bio-Skin - BS) para prótese bucomaxilofacial. Foram analisadas alteração de cor, dureza Shore A, resistência à tração, características de superfície (MEV) e composição química (EDS) frente à diferentes pigmentações e envelhecimentos. Como parâmetro de comparação foi empregado o silicone MDX4-4210. Foram obtidos 120 espécimes para cada material com formato circular e 160 em forma de haltere, a partir de matrizes metálicas de corte, os quais foram distribuídos em 4 grupos: PI - pigmentação intrínseca (pó de maquiagem); OP - opacificador (sulfato de bário, BaSO4); PIO - associação de PI + OP; SP - sem adição de PI ou OP. Em seguida, os espécimes foram distribuídos aleatoriamente em 3 subgrupos para exposição ao envelhecimento por luz natural (LN, n=10), luz ultravioleta (UV, n=10) e ausência de luz (C, n=10). O período experimental foi de 12 meses. A alteração de cor foi verificada com auxílio de espectrocolorímetro e sistema CIE L*a*b*. Para a dureza foi utilizado um durômetro Shore A e a análise da resistência à tração foi realizada em máquina universal de ensaio. As variáveis de resposta quantitativas foram mensuradas imediatamente após a obtenção dos espécimes e após o período experimental. A análise de superfície foi realizada por microscopia eletrônica de varredura (MEV) e a composição química dos silicones, por espectroscopia por energia dispersiva (EDS). Os dados foram submetidos à análise de variância e teste complementar de Tukey (p<0,05). Os resultados das análises por MEV e EDS foram apresentados em imagens e gráficos. Houve interação entre todos os fatores (p<0,05) e ambos os materiais sofreram variações em função das pigmentações e envelhecimentos. Para alteração de cor, o silicone experimental (BS) apresentou as menores variações de cor. Analisando os silicones em função da pigmentação, o MDX apresentou maiores variações com os espécimes SP e com OP envelhecidos por luz natural e luz UV. Para o BS, houve alteração significativa da cor dos espécimes SP e OP somente após o envelhecimento por LN. Os dois materiais apresentaram aumento da dureza frente a todas as condições, sendo que o silicone BS apresentou a maior variação. O silicone experimental apresentou resistência à tração superior ao MDX em todas as situações. O MDX não sofreu influência significativa na resistência à tração por nenhuma das pigmentações ou envelhecimento, exceto quanto pigmentado com pó de maquiagem e envelhecido por UV, onde houve aumento da resistência. Quanto ao silicone BS, os maiores valores de resistência à tração foram encontrados com a PI e PIO em todos os grupos de envelhecimento. Pode-se considerar que o material experimental apresentou resultados favoráveis em relação à alteração de cor, dureza Shore A e resistência à tração para sua aplicação clínica em prótese bucomaxilofacial. A associação da pigmentação intrínseca, por meio de pó de maquiagem com opacificador, protegeu o silicone da alteração de cor e promoveu alterações aceitáveis nas propriedades mecânicas dos materiais. Todos os processos de envelhecimento promoveram alterações nas propriedades dos materiais. / The aim of this study was to propose the use of a new silicone (Bio-Skin - BS) for maxillofacial prosthesis. Color change, Shore A hardness, tensile strength, surface characteristics (SEM) and chemical composition (EDS) were analyzed, regarding different pigmentation and aging methods. The MDX4-4210 silicone was used as parameter of comparison. Specimens (120 circular and 160 dumbbell-shaped) were obtained for each material, from metal cutting molds, which were divided into 4 groups: IP - intrinsic pigmentation (makeup powder); OP - opacifier (barium sulfate, BaSO4); IPO - IP + OP association; WP - without adding IP or OP. Then, the specimens were randomly divided into 3 subgroups to aging by exposure to natural light (NL, n = 10), ultraviolet light (UV, n = 10) and without light (C, n = 10). The experimental period was 12 months. The color change was observed with spectrocolorimeter and CIE L*a*b* system. For hardness we used a Shore A durometer and the analysis of tensile strength was performed in a universal testing machine. The quantitative response variables were measured immediately after obtaining the specimens and after the experimental period. The surface analysis was performed by scanning electron microscopy (SEM) and the chemical composition of silicones, by energy dispersive spectroscopy (EDS). Data were submitted to ANOVA and Tukey\'s test (p <0.05). SEM and EDS results were presented in pictures and graphics. There was interaction between all factors (p <0.05) and both materials varied depending on the pigmentation and aging methods. For color change, the experimental silicone (BS) showed the lowest color variations. Analyzing the silicones due to the pigmentation, the MDX showed higher variation with the WP and OP specimens aged in natural light and UV light. For BS, there was significant change in the color of the WP and OP specimens only after aging for NL. The two materials presented an increase in hardness front of all conditions, and the BS silicone showed the greatest variation. The experimental silicone showed superior tensile strength to MDX in all situations. The MDX was not affected in tensile strength by any pigmentation or aging, except for the group pigmented with makeup powder and aged by UV, where there was an increase of resistance. As to BS silicone, the highest tensile strength values were found for the IP and IPO in all age groups. It can be considered that the experimental material showed favorable results regarding color change, Shore A hardness and tensile strength for clinical use in maxillofacial prosthesis. The association of intrinsic pigmentation through makeup powder and opacifier, protected silicone of color change and promoted acceptable changes in mechanical properties of the materials. All the aging processes promoted changes in material properties.

Ein Dielektrischer Elastomer Aktuator (DEA) ist ein dehnbarer Kondensator, der aus einem Elastomerfilm besteht, der sich zwischen zwei flexiblen Elektroden befindet. Bei Anlegen einer elektrischen Spannung, ziehen sich die Elektroden aufgrund elektrostatischer Wechselwirkungen an, wodurch das Elastomer in z-Richtung zusammengepresst wird und sich dementsprechend in der x-,y-Ebene ausdehnt. Hierdurch werden Aktuationsbewegungen erreicht, welche sehr präzise über die Spannung gesteuert werden können. Zusätzlich sind DEAs kostengünstig, leicht und aktuieren geräuschlos. DEAs können beispielsweise für Produkte im medizinischen Bereich oder für optischer Komponenten genutzt werden. Ebenso kann aus diesen Bauteilen Strom erzeugt werden. Das größte Hindernis für eine weite Implementierung dieser Materialien liegt in den erforderlichen hohen Spannungen zum Erzeugen der Aktuationsbewegung, welche sich tendenziell im Kilovolt-Bereich befinden. Dies macht die Elektronik teuer und die Bauteile unsicher für Anwender. Um geringere Betriebsspannungen für die DEAs zu erreichen, sind signifikante Materialverbesserungen - insbesondere des verwendeten Elastomers - erforderlich. Um dies zu erreichen, können die dielektrischen Eigenschaften (Permittivität) der Elastomere gesteigert und/oder deren Steifigkeit (Young-Modul) gesenkt werden. In der vorliegenden Arbeit konnte die Aktuationsleistung von Silikonfilmen durch die Addition organischer Dipole erheblich verbessert werden. Hierfür wurde ein Verfahren etabliert, um funktionalisierte Dipole kovalent an das Polymernetzwerk zu binden. Dieser als "One-Step-Verfahren" bezeichnete Ansatz ist einfach durchzuführen und es werden homogene Filme erhalten. Die Dipoladdition wurde anhand verschiedener Silikone erprobt, die sich hinsichtlich ihrer mechanischen Eigenschaften unterschieden. Bei maximalem Dipolgehalt verdoppelte sich die Permittivität aller untersuchten Silikone und die Filme wurden deutlich weicher. Hierbei war festzustellen, dass die Netzwerkstruktur der verwendeten Silikone einen erheblichen Einfluss auf die erreichte Aktuationsdehnung hat. Abhängig vom Netzwerk erfolgte eine enorme Steigerung der Aktuationsleistung im Bereich von 100 % bis zu 4000 %. Dadurch können die Betriebsspannungen in DEAs deutlich abgesenkt werden, so dass sie tendenziell bei Spannungen unterhalb von einem Kilovolt betrieben werden können. / Dielectric elastomer actuators (DEAs) are compliant capacitors consisting of an elastomer film between two flexible electrodes. When a voltage is applied the electrostatic attraction of the electrodes leads to a contraction of the polymer in the z-direction and to a corresponding expansion in the x,y-plane. DEAs show high actuation strains, which are very accurate and adjustable by the applied voltage. In addition these devices are low-cost, low-weight and the actuation is noise-free. DEAs can be used for medical applications, optical components or for energy harvesting. The main obstacle for a broad implementation of this technology is the high driving voltage, which tends to be several thousand volts. For this reason the devices are unsafe for users and the needed electronic components are expensive. A significant improvement of the materials - especially of the used elastomer - is necessary to lower the actuation voltages. This can be achieved by improving the dielectric properties (permittivity) of the elastomer and/or by lowering it's stiffness (Young's modulus). In this work the actuation performance of silicone lms was improved significantly by the addition of organic dipoles. A simple procedure was developed, in which functionalized dipoles were bound to the polymer matrix, leading to homogenous and transparent films. This so-called "one-step-film-formation" was tested on various silicones with different mechanical properties. For the highest dipole content the permittivity of all tested silicones was doubled and the modified films showed a substantially lower stiffness. It was proven that the structure of the macromolecular network has a clear impact on the achievable actuation properties. For the highest dipole contents the actuation performance increased remarkably by 100 % up to 4000 % in respect to the investigated network. The addition of organic dipoles to the elastomer enables a signicant reduction of the needed driving voltage for DEAs below one kilovolt.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-06T11:02:00Z No. of bitstreams: 1 GERALDO SÁVIO ALMEIDA HOLANDA - TESE (PPGCEMat) 2016.pdf: 9735527 bytes, checksum: 9e91f1e9c99fbe2f4b51aad716c26581 (MD5) / Made available in DSpace on 2018-07-06T11:02:00Z (GMT). No. of bitstreams: 1 GERALDO SÁVIO ALMEIDA HOLANDA - TESE (PPGCEMat) 2016.pdf: 9735527 bytes, checksum: 9e91f1e9c99fbe2f4b51aad716c26581 (MD5) Previous issue date: 2016-12-15 / O Silastic® MDX4-4210 é um dos materiais mais utilizados no mundo na confecção de próteses faciais devido às suas propriedades, contudo, ele apresenta algumas limitações, notadamente a que reduz o tempo de vida útil destas. O objetivo deste estudo foi avaliar a influência de pigmentos nas propriedades de um silicone para prótese facial submetido ao envelhecimento acelerado. Foram confeccionados 288 corpos de provas e divididos em três grupos: o Grupo Controle (GC) constituído por amostras do silicone Silastic® MDX4-4210 sem acréscimos de pigmento e os grupos experimentais G1 e G2. O Grupo 1 (G1), formado por amostras do silicone Silastic® MDX4-4210, pigmento com pó de maquiagem e, o Grupo 2 (G2), constituído por amostras de silicone com a incorporação da solução do pigmento de Urucum-Bixina (Bixa orellana L). Cada grupo foi constituído de 24 corpos de prova, sendo 09 unidades destinadas às caracterizações e 15 unidades aos ensaios mecânicos. Setenta e dois corpos de prova foram selecionados para serem avaliados antes do envelhecimento acelerado. Os 216 corpos de prova restantes, foram submetidos ao envelhecimento acelerado por exposição a ciclos de Ultravioleta, Temperatura e Umidade (UV/T/U) nos tempos de 120, 240 e 1000 horas. As amostras foram caracterizadas por meio de análise por Microscopia Ótica, Microscopia Eletrônica de Varredura, Espectroscopia na região do infravermelho com transformada de Fourier, Termogravimetria e os ensaios de Citotoxicidade, Sorção e Biodegradação Enzimática. Foram realizados os ensaios mecânicos (dureza Shore A, resistência ao rasgamento e à tração, módulo de elasticidade e alongamento a ruptura). Os dados obtidos foram analisados e obtidas as medidas estatísticas: média; mediana; desvio padrão. Os dados mostraram que não foram observadas mudanças significativas na cor ou textura em diferentes períodos de envelhecimento acelerado. Em geral, o material tornou-se mais resistente, mais duro, mais rígido e menos dúctil, conforme foi envelhecido, mas manteve uma deformação percentual superior a 100-120%. Apesar das alterações causadas pelo envelhecimento em suas propriedades mecânicas, o material envelhecido permaneceu suficientemente flexível e adequado para a aplicação proposta. Não houve diferença significativa entre as propriedades dos materiais pigmentados com maquiagem ou bixina. / Silastic® MDX4-4210 is one of materials most widely used in the world for facial prosthesis due to its properties, however, it has some limitations, that reduce its lifespan. The aim of this study is to evaluate the influence of pigments in the properties of a silicone for facial prosthesis subjected to accelerated aging. 288 samples were manufactured and divided in three groups: the control group (CG) consisting of Silastic® MDX4-4210 silicon samples without pigment and experimental groups G1 and G2. Group 1 (G1), consisted of Silastic® MDX4-4210 silicone samples, with makeup pigment powder and Group 2 (G2) consisting of silicone samples with the addition of a solution of Bixin (Bixa orellana L). Each group consisted of 24 specimens: 09 units for the characterizations and 15 units for mechanical tests. Seventy-two specimens were selected for further evaluation prior to accelerated aging. The 216 remaining specimens were subjected to accelerated aging by exposure to UV,temperature and humidity cycles (UV/T/U) for 120, 240 and 1000 hours. The samples were characterized by optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, Cytotoxicity assays, Sorption and Enzyme Biodegradation. Mechanical tests were also performed (Shore A hardness, tear resistance and tensile strength, elastic modulus and elongation to break). Data were analyzed and average, mean, median and standard deviation values were obtained. The data showed that no significant changes were observed in the color or texture in different periods of accelerated aging. In general, the material became tougher, stiffer, more rigid and less ductile, with aging but maintained a percentage deformation exceeding 100-120%. Despite the changes caused by aging changes the mechanical properties of the aged material remained suitable for the proposed application.There were no significant differences in the proprerties of the materials pigmented with either makeup or bixin.