Orientador: Sergio Persio Ravagnani / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-07T03:49:14Z (GMT). No. of bitstreams: 1 Trochmann_JoseLuizLino_D.pdf: 1070584 bytes, checksum: 3407aee7ad6d88d9de0a1326aaf3d29d (MD5) Previous issue date: 2006 / Resumo: Neste trabalho de tese foi realizado um estudo do potencial de predição de propriedades de transporte em matrizes poliméricas de poli - imidas, utilizando a simulação dinâmica molecular de gases simples como Oxigênio, Nitrogênio e Dióxido de Carbono. A propriedade de transporte de interesse prático, a permeabilidade de uma membrana polimérica a um dado penetrante, envolve a determinação de propriedades de ordem cinética e termodinâmica, respectivamente a determinação do coeficiente de difusão e da solubilidade deste penetrante na matriz polimérica. Atenção especial foi conferida à propriedade cinética, pela predição do coeficiente de autodifusão dos penetrantes. Num procedimento experimental clássico é de vital importância para significância das conclusões derivadas dos experimentos, o uso de amostras de membranas poliméricas adequadamente preparadas quanto à composição química, estrutura física e morfologia. Analogamente, quando se utiliza a simulação molecular para a predição de propriedades, tais como o coeficiente de autodifusão, também é de fundamental relevância para os resultados obtidos, a qualidade dos modelos moleculares das matrizes poliméricas, que serão usados como base. Assim para a preparação de modelos moleculares com o adequado empacotamento, um procedimento para a obtenção de modelos bem equilibrados foi desenvolvido neste trabalho. Os modelos moleculares desenvolvidos foram usados para a obtenção dos valores de massa específica em função da temperatura, e comparados aos valores experimentais disponíveis e quando necessário a, valores preditos por meio da expressão de massa específica em função da temperatura, acima e abaixo da temperatura de transição. A capacidade do modelo molecular desenvolvido em predizer a massa especifica e temperatura de transição vítrea foi usada como critério para a validação da adequação do empacotamento proposto para o referido modelo molecular da matriz polimérica. Os modelos validados de empacotamento, células amorfas, foram utilizados para o cálculo do coeficiente de autodifusão dos gases acima mencionados, através do da simulação dinâmica molecular. A comparação dos coeficientes de autodifusão obtidos das poli-imidas aromáticas e éster imidas, BAAF, 6FDA-ODA, PMDA-ODA e BA-20DA, para os gases O2, N2 e CO2, com os dados experimentais, permitiu concluir a adequação das células amorfas e do esquema de simulação dinâmica molecular para a predição do coeficiente de autodifusão.. A versão preditiva de Vrentas e Duda, baseada na teoria do volume livre, foi utilizada para a predição dos coeficientes de autodifusão da água e do etanol para as poli-imidas acima. , Estes valores, quando comparados com os valores obtidos através da simulação dinâmica molecular mostram a validade de ambas as teorias para a predição da cinética de difusão de penetrantes em matrizes poliméricas complexas / Abstract: In this thesis a study of the predictive potential of the molecular dynamic simulation was performed for transport properties of light gases in polyimide matrix. From de practical point of view permeability is the property of most interest, and involves kinetics as well as thermodynamics properties, diffusion coefficient and solubility of the penetrants molecule in the bulk polymeric matrix, this work will be focus in the former. As important as is in as experimental work, a well prepared polymeric membrane is essential for the significance of the draw conclusions. Therefore a special attention was take in the preparation of the bulk molecular polymeric model, the so called amorphous cell, in order to obtain well-equilibrated molecular packing models for the polyimide matrixes. The amorphous cells were prepared throughout thermodynamic transforms, using one or more of the statistical ensembles and cell specific volume obtained as a function of temperature, this data was compared against the experimental data available, and when necessary to data obtained via predictive methods. The molecular packing model ability to predict the glass transition temperature was used as criteria to validate de amorphous cell, to be used in the molecular dynamic' simulations allow the matrix to be locally flexible and coupled to the classic molecular dynamics simulation. The resulting self diffusion coefficients for the polyimide, BAAF, 6FDA-ODA, PMDA­ODA and BA-20DA for the gases O2, N2 e CO2 were compared to the experimental data. The lack of quality experimental diffusion data available for polyimide membranes for larger penetrants as water and ethanol, showed up as a good opportunity to assess the predictive capability of the molecular dynamic simulation for self diffusion coefficients, considering the relevant technological relevance of polyimide membranes for pervaporation process. The data of self diffusion coefficient produced by the predictive version of free-volume theory after Vrentas and Duda, was compared with the data produced via coupled molecular dynamic simulation for the water and ethanol penetrants, showing the relevance of both theories for the prediction of penetrants kinetic in complex polymeric matrixes / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

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The flexible and stretchable electronic market is increasing particularly in the field of biomedical electronics. Widely used printed silver conductive tracks today are only eligible for on-skin applications. However, for biomedical applications fully biocompatible, flexible and even stretchable materials for device fabrication are needed. This paper presents an additive printing approach to fabricate flexible and stretchable electronics by using a biocompatible platinum material. Usually, in order to realize electrically conducting Ptinterconnects by inkjet printing, it requires a furnace sintering at prohibitively high temperatures, which are not compatible with thermal sensitive polymeric substrates. This paper describes a high-power diode laser sintering (HPDL) and a flash lamp annealing (FLA) as promising alternative sintering methods. Both processes are eligible whereas laser sintering showed slightly better results. Bending tests and adhesive strength tests of platinum printed inks on polyimide with up to 180 000 cycles, show that printed platinum is a suitable biocompatible material for flexible electronics.

Membrane technology has great potential to complement traditional energy-intensive molecular separation processes such as distillation, with the advantage of low footprint generation. However, this would only be achieved with the development of better membranes able to operate in challenging conditions, including combinations of organic solvents, high temperatures, extreme pHs, and oxidative environments. This dissertation aims to use high-performance polymeric materials that can withstand temperatures of 120 °C in polar aprotic solvents like N,N-dimethylformamide as separation membranes, using different crosslinking strategies and alternative routes for commercially available material processing. The thesis will be divided into two main approaches. The first approach will start from soluble polyimides as precursors, with designed functionalities that allow post-membrane modifications, such as chemical crosslinking, thermal crosslinking, and thermal rearrangement to enhance the material's chemical resistance. The focus will be on the polyimide synthesis by an alternative one-step room-temperature polyhydroxyalkylation reaction. The chemical and thermal crosslinking take place without involving the imide bond, by incorporating a highly tunable functional group (isatin) in the synthesis of the materials. Propargyl as a pendant group will be used for the thermal crosslinking, and hydroxyl group for the thermal rearrangement. In all cases, the obtained membranes were stable in common organic solvents at 120 °C. The second approach will start from intrinsically solvent-resistant and commercially available poly(aryl ether ketone)s, turned into membranes by a closed-loop modification-regeneration strategy, to address long-term separations in organic solvents at high temperatures. We present for the first time porous poly(aryl ether ketone) flat-sheet and hollow fiber membranes prepared without the use of strong acids or high temperatures. Two methodologies are proposed. The developed strategies shall contribute toward avoiding the regular consumption of new materials and waste generation since the polymer used does not require crosslinking for its stability under organic solvents.

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The lap shear strength of chromic acid anodized, primed, Ti-6Al-4V alloy bonded with a high performance FM-5 polyimide adhesive has been investigated as a function of thermal treatment for selected times at various temperatures in air. The research findings indicate that the lap shear strength decreases with the increase in duration of the thermal treatment at constant temperature and with the increase in temperature at constant time. The bond fails increasingly in the oxide coating with increasing treatment temperature and time of treatment. Surface analysis results for debonded specimens suggest that the process leading to failure is the formation of fluorine-containing materials within the oxide, which weakens the adherend-adhesive bond. The formation of the fluorine components is facilitated by treatment at elevated temperatures. This study suggests that the presence of fluoride ions in the anodic oxide coating, prior to bonding, is detrimental to the bond strength of adhesively bonded Ti-alloy when exposed to high temperatures. The wedge test configuration was used to investigate the influence of temperature on the bond durability of adhesively bonded chromic acid anodized Ti-6Al-4V alloy in air. Based on the average crack length vs. exposure time data, the bond durability varied in the order -25°C > 24°C > 177°C. In each case, the bonded joint failed cohesively within the adhesive, irrespective of the temperature of exposure. XPS analysis and scanning electron photomicrographs of failure surfaces revealed that the failure occurred at the scrim cloth/adhesive interface. The influence of thermal treatment history on the bond durability of adhesively bonded chromic acid anodized Ti-6Al-4V alloy immersed in boiling water was also investigated. The average crack length vs. immersion time indicated no significant differences for specimens that were thermally treated and then bonded compared to the non-thermally treated specimens. In addition, the failure mode was cohesive within the adhesive for specimens prepared using various thermal treatment conditions. The crack growths for samples treated for 0.5 hour and 1.0 hour and for non-thermally treated specimens for any given exposure time were equivalent. In addition, cohesive failure (failure within adhesive) was observed for each specimen under each treatment condition. The specimens that were bonded and then thermally treated for 3 hours, failed in the oxide coating immediately upon insertion of the wedge. Surface analysis results for debonded specimens suggest that the process leading to failure is the formation of fluorine-containing materials within the oxide. The measured average activation energy for the formation of aluminum fluoride species is 149 kJ/mol. The high activation energy suggests that the rate of aluminum fluoride formation is substantial only at high temperatures. In summary, the presence of fluorides in the anodic oxide coatings prior to bonding is detrimental to the overall strength and durability of adhesively bonded chromic acid anodized Ti-6Al-4V joints which have been exposed to high temperatures (350°C-399°C). / Ph. D.

When bonded joints are subjected to harsh environmental conditions, the interphase, the three-dimensional region surrounding the adhesive/substrate interface, becomes critically important. Frequently, failure occurs in this region after adhesively bonded systems are subjected to elevated temperature oxidative aging. In a previous study, this was found to be the case with a polyimide adhesive bonded to chromic acid anodized (CAA) Ti-6Al-4V. The objective of the current research has been twofold: 1) to investigate the effect of thermal aging on the interphase region of polyimide/titanium adhesive joints, and 2) to evaluate the method used in the current study for durability characterization of other adhesive/substrate systems. The method used in this research has been to characterize the effect of elevated temperature aging on the following systems: 1) Notched coating adhesion (NCA) specimens and 2) bulk samples of dispersed substrate particles in an adhesive matrix. The NCA test has the advantages of an accelerated aging geometry and a mode mix that leads to failure through the interphase, the region of interest. The bulk samples have the advantage of an increased interphase volume and allow for the application of bulk analysis techniques to the interphase, a region that is traditionally limited to surface analysis techniques. The adhesive systems studied consisted of one of two polyimide adhesives, LaRC© PETI-5 or Cytec Fiberite© FM-5, bonded to CAA Ti-6Al-4V. The model filled system consisted of a PETI-5 matrix with amorphous titanium dioxide filler. Through the use of the NCA test, it was determined that bonded specimens made with FM-5 lose approximately 50% of their original fracture energy when aged in air at 177°C for 30 days. This aging temperature is well below the glass transition temperature of the adhesive, 250°C. At the same time, the failure location moves from the anodized oxide layer to the adhesive that is directly adjacent to the substrate surface, the interphase region. Through surface analysis of this region, it is determined that the adhesive penetrates the pores of the CAA surface to a depth of 70 to 100 nm, promoting adhesion at the interface. With aging, the adhesive in the interphase region appears to be weakening, although analysis of the bulk adhesive after aging shows little change. This indicates that adhesive degradation is enhanced in the interphase compared to the bulk. Analysis of the model filled system gave similar information. Specimens containing titanium dioxide filler had glass transition temperatures that were approximately 20°C lower than the neat polyimide samples. In addition, the filled samples contained a significant portion of low molecular weight extractable material that was not present in the neat specimens. The tan delta spectra from dynamic mechanical thermal analysis of the filled specimens exhibited a shoulder on the high-temperature side of the glass transition peak. This shoulder is attributed to the glass transition of the interphase, a distinct phase of the polyimide which is constrained by adsorption onto the filler particle surfaces. As a function of aging time at 177° or 204°C, the shoulder decreases substantially in magnitude, which may relate to loss of adhesive strength between the polyimide and the filler particles. From this research, it has been illustrated that information relating to the durability of adhesively bonded systems is gained using an interfacially debonding adhesive test and a model system of substrate particles dispersed in an adhesive matrix / Ph. D.