Avaliação in vitro da microinfiltração marginal de resinas de polimerização aumentada pela técnica directa

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Nanostructures, Semicrytalline Morphology, and Nanoscale Confinement Effect on the Crystallization Kinetics in Self-Organized Block Copolymer/Thermoset Blends

This work reports the first instance of self-organized thermoset blends containing diblock copolymers with a crystallizable thermoset-immiscible block. Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and a low-molecular-weight (M-n = 1400) amphiphilic polyethylene-block-poly(ethylene oxide) (EEO) symmetric diblock copolymer were prepared using 4,4'-methylenedianiline (MDA) as curing agent and were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC). All the MDA-cured ER/EEO blends do not show macroscopic phase separation but exhibit microstructures. The ER selectively mixes with the epoxy-miscible PEO block in the EEO diblock copolymer whereas the crystallizable PE blocks that are immiscible with ER form separate microdomains at nanoscales in the blends. The PE crystals with size on nanoscales are formed and restricted within the individual spherical micelles in the nanostructured ER/EEO blends with EEO content up to 30 wt %. The spherical micelles are highly aggregated in the blends containing 40 and 50 wt % EEO. The PE dentritic crystallites exist in the blend containing 50 wt % EEO whereas the blends with even higher EEO content are completely volume-filled with PE spherulites. The semicrystalline microphase-separated lamellae in the symmetric EEO diblock copolymer are swollen in the blend with decreasing EEO content, followed by a structural transition to aggregated spherical micellar phase morphology and, eventually, spherical micellar phase morphology at the lowest EEO contents. Three morphological regimes are identified, corresponding precisely to the three regimes of crystallization kinetics of the PE blocks. The nanoscale confinement effect on the crystallization kinetics in nanostructured thermoset blends is revealed for the first time. This new phenomenon is explained on the basis of homogeneous nucleation controlled crystallization within nanoscale confined environments in the block copolymer/thermoset blends.

Infrared microspectroscopic mapping of the homogeneity of extruded blends: Application to starch/polyester blends

Blends of starch and a biodegradable polyester, produced by an extrusion process, which included a cross-linker/compatibilizer (maleic anhydride) and an initiator (dicumyl peroxide), were studied by infrared (IR) microspectroscopy using an attenuated total reflectance (ATR) objective. Extruded material, which had a diameter of about 3 mm, was sectioned and embedded in epoxy resin prior to IR analysis. Spectra were collected in a grid pattern across the sectioned face of the sample. Measurement of various band parameters from the spectra allowed IR maps to be constructed containing semi-quantitative information about the distribution of blend components. These maps showed the quality of the blend on a microscopic scale and showed how it varied with different concentrations of compatibilizer and initiator. (c) 2005 Elsevier Ltd. All rights reserved.

COMPARAÇÃO DAS FORÇAS DE DEFLEXÃO LIBERADAS ENTRE OS FIOS ORTODÔNTICOS ESTÉTICOS E SUA RELAÇÃO COM O REVESTIMENTO

O objetivo do presente estudo consistiu em comparar as forças de deflexão in vitro entre fios estéticos e fio NiTi, para verificar a força máxima e da região platô e determinar sua correlação com o diâmetro do fio com e sem revestimento. Foram realizados dez ensaios de sete marcas comerciais de arcos précontornados, sendo seis fios estéticos (Invu (I), Optis (O), Flexy Super Elastic Esthetic (FSEE), Niticosmetic (N), Orthocosmetic Elastinol (OE) e Pro Form Coated Nitanium (PFCN)) e um fio NiTi superelástico (Nitinol Super Elastic (NSE)), aplicando-se o teste de curvatura de três pontos, associado a máquina de ensaios universal EMIC. Desenvolveu-se um dispositivo com braquetes cerâmicos (Transcend), cujos fios foram presos por elásticos modulares, sendo obtidos os valores da força de deflexão em 3,0, 2,0 e 1,0mm. O diâmetro dos fios com e sem revestimento foram mensurados com o especímetro digital Micromaster. A análise de variância a um critério (p<0,05) mostrou diferença significante entre os fios e o teste post-hoc de Tukey determinou que a força de deflexão em 3mm para o O

ANÁLISE MICROSCÓPICA E DA RUGOSIDADE DE SUPERFÍCIE DE FIOS ORTODÔNTICOS ESTÉTICOS, ANTES E APÓS DEFLEXÃO

O objetivo deste estudo foi avaliar a topografia de superfície dos fios estéticos, antes e após teste de deflexão. A amostra foi composta por 70 corpos de prova de fios 0,014 redondos, sendo 10 de cada uma das marcas comerciais avaliadas: Orthocosmetic Elastinol (Masel), Flexy Super Elastic Esthetic (Orthometric), InVu (TP Orthodontics) e ProForm Nitanium (Ortho Organizers) fios de NiTi revestidos por Teflon®; Optis (TP Orthodontics) fio de resina reforçado por fibra de vidro ou FRP; Niticosmetic (Tecnident) fio de NiTi revestido por resina epoxídica; e Nitinol SE (3M Unitek) fio de NiTi superelástico, usado para controle. A topografia de superfície de cada fio foi avaliada por rugosímetro e por microscópio óptico, antes e após ser submetido a ensaio de deflexão, no lado em que a força foi aplicada e no lado oposto a este. Cada fio foi defletido em 3,1mm, a uma velocidade de 1mm/min, com célula de carga de 5N a 36⁰C + 1⁰C. A análise de variância a três critérios (p<0,05) mostrou diferença significante entre os fios e o teste de Tukey mostrou que o fio Optis (TP Orthodontics) apresentou aumento nos parâmetros de rugosidade Ra, Rt e Rz, após a deflexão. O fio Niticosmetic (Tecnident) apresentou aumento na rugosidade média (Ra). O fio InVu (TP Orthodontics) foi o único que mostrou aumento na rugosidade no lado em que a força foi aplicada. A análise visual por meio de microscopia óptica revelou alterações na superfície em todos os fios estéticos após o teste de deflexão, desde delaminações do revestimento, observadas nos fios Orthocosmetic Elastinol e InVu, riscos permanentes na superfície, como visto nos fios Flexy Super Elastic Esthetic, Niticosmetic e ProForm Nitanium, e até mesmo fratura incompleta, no fio Optis. Concluiu-se que o fio Niticosmetic apresentou topografia de superfície similar ao fio metálico, e os demais fios estéticos apresentaram maior rugosidade e alterações visuaisna superfície.

The incidence of corpora amylacea (CA) in the optic nerve of patients with Alzheimer's disease

Corpora amylacea (CA) are spherical or ovoid bodies 50-50 microns in diameter. They have been described in normal elderly brain as well as in a number of neurodegenerative disorders. In this study, the incidence of CA in the optic nerves of Alzheimer's disease (AD) patients was compared with normal elderly controls. Samples of optic nerves (MRC Brain Bank, Institute of Psychiatry) were taken from 12 AD patients (age range 69-94 years) and 18 controls (43-82 years). Optic nerves were fixed in 2% buffered glutaraldehyde, post-fixed in osmium tetroxide, embedded in epoxy resin and then sectioned to a thickness of 2 microns. Sections were stained with toluidine blue. CA were present in all of the optic nerves examined. In addition, a number of similarly stained but more irregularly shaped bodies were present. Fewer CA were found in the optic nerves of AD patients compared with controls. By contrast, the number or irregularly shaped bodies was increased in AD. In AD, there may be a preferential decline in the large diameter fibres which may mediate the M-cell pathway. Hence, the decline in the incidence of CA in AD may be associated with a reduction in these fibres. It is also possible that the irregualrly shaped bodies are a degeneration product of the CA.

Interlamellar modification of smectite clays

Clay minerals, both natural and synthetic, have a wide range of applications. Smectite clays are not true insulators, their slight conductivity has been utilized by the paper industry in the development of mildly conducting paper. In particular, the synthetic hectorite clay, laponite, is employed to produce paper which is used in automated drawing offices where electro graphic printing is common. The primary objective of this thesis was to modify smectite clays, particularly laponite, to achieve enhanced conductivity. The primary objective was more readily achieved if the subsidiary objective of understanding the mechanism of conductivity was defined. The cyclic voltammograms of some cobalt complexes were studied in free solution and as clay modified electrodes to investigate the origin of electroactivity in clay modified electrodes. The electroactivity of clay modified electrodes prepared using our method can be attributed to ion pairs sorbed to the surface of the electrode, in excess of the cationic exchange capacity. However, some new observations were made concerning the co-ordination chemistry of the tri-2-pyridylamine complexes used which needed clarification. The a.c. conductivity of pressed discs of laponite RD was studied over the frequency range 12Hz- 100kHz using three electrode systems namely silver-loaded epoxy resin (paste), stainless-steel and aluminium. The a. c. conductivity of laponite consists of two components, reactive (minor) and ionic (major) which can be observed almost independently by utilizing the different electrode systems. When the temperature is increased the conductivity of laponite increases and the activation energy for conductivity can be calculated. Measurement of the conductivity of thin films of laponite RD in two crystal planes shows a degree of anisotropy in the a.c. conductivity. Powder X-ray diffraction and 119Sn Mossbauer spectroscopy studies have shown that attempts to intercalate some phenyltin compounds into laponite RD under ambient conditions result in the formation of tin(IV) oxide pillars. 119Sn Mossbauer data indicate that the order of effectiveness of conversion to pillars is in the order: Ph3SnCl > (Ph3Sn)2O, Ph2SnCl2 The organic product of the pillaring process was identified by 13C m.a.s.n.m.r. spectroscopy as trapped in the pillared lattice. This pillaring reaction is much more rapid when carried out in Teflon containers in a simple domestic microwave oven. These pillared clays are novel materials since the pillaring is achieved via neutral precursors rather than sacrificial reaction of the exchangeable cation. The pillaring reaction depends on electrophilic attack on the aryl tin bond by Brønsted acid sites within the clay. Two methods of interlamellar modification were identified which lead to enhanced conductivity of laponite, namely ion exchange and tin(IV) oxide pillaring. A monoionic potassium exchanged laponite shows a four fold increase in a.c. conductivity compared to sodium exchanged laponite RD. The increased conductivity is due to the appearence of an ionic component. The conductivity is independent of relative humidity and increases with temperature. Tin(IV) oxide pillared laponite RD samples show a significant increase in conductivity. Samples prepared from Ph2SnCl2 show an increase in excess of an order of magnitude. The conductivity of tin(IV) oxide pillared laponite samples is dominated by an ionic component.

Melamine phosphate as a component of intumescent coatings

Melamine orthophosphate has been shown to exhibit variations in its chemical constitution, and crystal shape and size, dependent upon the method of production. These crystal types have been incorporated with epoxy resin to produce intumescent coatings, which have been tested on a small scale fire testing device, designed and calibrated within this project. The factors influencing performance in three fire test regimes are the percentage loading of melamine phosphate, its chemical constitution, crystal size and shape, thermal degradation, and state of agglomeration . and dispersion in the coating, determined by the method of incorporation into the coating. When melamine phosphate is heat treated at 210ºC, a process designed to reduce its solubility, the performance of coatings produced with such material is profoundly affected, depending mainly on crystal size and shape alone. Consideration of heat transfer across the chars produced has allowed a quantitative evaluation of the thermal resistance of chars throughout a test. An optimum production route for melamine phosphate has been suggested, taking into account the requirements for weatherability of coatings as well as performance in a fire.

Desenvolvimento de um painel sanduíche com carga de particulado oriundo de resíduo lignocelulósico para aplicação em produtos na área de equipamentos de proteção

This work aims to study and investigate the use of a hybrid composite polymer formed with blanket aramid (Kevlar 29) fiber blanket flax fiber and particulate dry endocarp of coconut (Cocos nucifera Linn), using as matrix an epoxy resin based thermoset for use in areas of protective equipment. Besides such material is used an aluminum plate, joined to the composite by means of glue based on epoxy and araldite commercial. The manufacturing process adopted was manual lamination (Hand Lay Up) to manufacture the hybrid composite. After the composite is prepared, an aluminum plate is subjected to pressure and glued to cure the adhesive. Layers of veil will also be used to separate the particulate from the linen blanket layer without disturbing the alignment of the fibers of the blankets. To characterize the mechanical and physical behavior was manufactured a plate of 800 x 600 mm of the hybrid composite, which were removed specimens for tests of water absorption to saturation; density; impact test (Charpy) and two test specimens for ballistic testing 220 mm x 200 mm to make a comparative study between the dry state and saturated water absorption and thus see the ballistic performance of these two conditions. The test was applied to make a comparative study of fracture in these two conditions, caused by penetrating ballistic missile (38 and 380). To test the impact (Charpy) will analyze the absorbed energy, fracture appearance and lateral contraction, also in dry condition and saturation of absorbed water, thereby analyzing situations where the impact load is relevant, such as bumps and shocks produced by stone, metal or wooden bars among others. The proposed configuration, along with the tests, has the purpose, application in the fields of equipment against ballistic impact, such as helmets; bullet proof vests; shields; protective packaging and other items to be identified in this research.

Caracterização do ciclo da marcha em amputado transtibial com prótese inteligente

This work presents an application of optical fiber sensors based on Bragg gratings integrated to a transtibial prosthesis tube manufactured with a polymeric composite systrem of epoxy resin reinforced with glass fiber. The main objective of this study is to characterize the sensors applied to the gait cycle and changes in the gravity center of a transtibial amputee, trough the analysis of deformation and strengh of the transtibial prosthesis tube. For this investigation it is produced a tube of the composite material described above using the molding method of resin transfer (RTM) with four optical sensors. The prosthesis in which the original tube is replaced is classified as endoskeletal, has vacuum fitting, aluminium conector tube and carbon fiber foot cushioning. The volunteer for the tests was a man of 41 years old, 1.65 meters tall, 72 kilograms and left-handed. His amputation occurred due to trauma (surgical section is in the medial level, and was made below the left lower limb knee). He has been a transtibial prosthesis user for two years and eight months. The characterization of the optical sensors and analysis of mechanical deformation and tube resistance occurred through the gait cycle and the variation of the center of gravity of the body by the following tests: stand up, support leg without the prosthesis, support in the leg with the prosthesis, walk forward and walk backward. Besides the characterization of optical sensors during the gait cycle and the variation of the gravity center in a transtibial amputated, the results also showed a high degree of integration of the sensors in the composite and a high mechanical strength of the material.

Desenvolvimento de fontes radioativas seladas imobilizadas em resina epóxi para verificação de detectores utilizados em medicina nuclear

Dissertação (Mestrado em Tecnologia Nuclear)

Desenvolvimento de tubulação em compósito polimérico revestida externamente com poliuretano de alta densidade

Pipelines for the transport of crude oil from the production wells to the collecting stations are named production lines . These pipes are subjected to chemical and electrochemical corrosion according to the environment and the type of petroleum transported. Some of these lines, depending upon the composition of the fluid produced, may leak within less than one year of operation due to internal corrosion. This work aims at the development of composite pipes with an external protecting layer of high density polyurethane for use in production lines of onshore oil wells, meeting operational requirements. The pipes were manufactured using glass fibers, epoxy resin, polyester resin, quartz sand and high density polyurethane. The pipes were produced by filament winding with the deposition of high density polyurethane on the external surface and threaded ends (API 15 HR/PM-VII). Three types of pipes were manufactured: glass/epoxy, glass/epoxy with an external polyurethane layer and glass/epoxy with an intermediate layer of glass fiber, polyester, sand and with an external polyurethane layer. The three samples were characterized by Scanning Electronic Microscopy (SEM) and for the determination of constituent content. In addition, the following tests were conducted: hydrostatic test, instant rupture, shorttime failure pressure, Gardner impact, transverse stiffness and axial tension. Field tests were conducted in Mossoró RN (BRAZIL), where 1,677 meters of piping were used. The tests results of the three types of pipes were compared in two events: after two months from manufacturing of the samples and after nine months of field application. The results indicate that the glass/epoxy pipes with an intermediate layer of fiber glass composite, polyester e sand and with an external layer of high density polyurethane showed superior properties as compared to the other two and met the requirements of pressure class, axial tensile strength, transverse stiffness, impact and environmental conditions, for onshore applications as production lines

Lattice Boltzmann Modeling and Specialized Laboratory Techniques to Determine the Permeability of Megaporous Karst Rock

The Pleistocene carbonate rock Biscayne Aquifer of south Florida contains laterally-extensive bioturbated ooltic zones characterized by interconnected touching-vug megapores that channelize most flow and make the aquifer extremely permeable. Standard petrophysical laboratory techniques may not be capable of accurately measuring such high permeabilities. Instead, innovative procedures that can measure high permeabilities were applied. These fragile rocks cannot easily be cored or cut to shapes convenient for conducting permeability measurements. For the laboratory measurement, a 3D epoxy-resin printed rock core was produced from computed tomography data obtained from an outcrop sample. Permeability measurements were conducted using a viscous fluid to permit easily observable head gradients (~2 cm over 1 m) simultaneously with low Reynolds number flow. For a second permeability measurement, Lattice Boltzmann Method flow simulations were computed on the 3D core renderings. Agreement between the two estimates indicates an accurate permeability was obtained that can be applied to future studies.

Micro- and macroscopic characterizations of the viscoelastic fracture of resin-based fibre composites

Micro- and macroscopic characterizations of the viscoelastic fracture of a unidirectional carbon-fibre-reinforced epoxy composite are presented. First, the micro-cracking behavior of the material is studied by the use of scanning electron microscopy; the in situ creep cracking process is observed and the crack propagation is measured. In order to obtain insight into the mechanisms of the observed creep cracking, macroscopic investigations were also carried out. Finite-element method simulations were carried out to calculate the stress distribution and the variation of stresses with time. A theoretical analysis of the orthotropy of viscoelastic fracture behavior of the material is also conducted.

Analyses of the mechanical properties and microstructure of bamboo epoxy composites

Bamboo reinforced epoxy possesses reasonably good properties to waarrant its use as a structural material, and is fabricated by utilizing bamboo, an abundant material resource, in the technology of fibre composites. Literature on bamboo-plastics composites is rare. This work is an experimental study of unidirectional bamboo-epoxy laminates of varying laminae number, in which tensile, compressive, flexural and interlaminar shear properties are evaluated. Further, the disposition of bamboo fibre, the parenchymatous tissue, and the resin matrix under different loading conditions are examined. Our results show that the specific strength and specific modulus of bamboo-epoxy laminates are adequate, the former being 3 to 4 times that of mild steel. Its mechanical properties are generally comparable to those of ordinary glass-fibre composites. The fracture behaviour of bamboo-epoxy under different loading conditions were observed using both acoustic emission techniques and scanning electron microscopy. The fracture mode varied with load, the fracture mechanism being similar to glass and carbon reinforced composites. Microstructural analyses revealed that natural bamboo is eligibly a fibre composite in itself; its inclusion in a plastic matrix will help solve the problems of cracking due to desiccation and bioerosion caused by insect pests. Furthermore, the thickness and shape of the composite can be tailored during fabrication to meet specific requirements, thereby enabling a wide spectrum of applications.