The Materials Genome Initiative was announced by the White House in June of 2011, and is a multi-agency initiative which calls the materials community to find ways to discover, develop, manufacture, and deploy advanced materials systems faster and more cost-efficiently. Currently, the amount of time it takes to discover and develop a new material system, optimize its properties, integrate it in to a system, certify that system, and develop the manufacturing capability so that it can be deployed in a commercial component takes at least 20 years. Since this trend holds regardless of the material system in question, the implication is that it is the process by which we as a community move through these seven steps, which causes the lengthy timeline. Historically, the discovery, development, and property optimization of a material system relies heavily on deep scientific knowledge, intuition and trial-and-error physical experimentation. Therefore much of the design and testing of materials in these early stages is currently performed through time-consuming and repetitive experimental and characterization feedback loops. Some of these feedback loops could be eliminated in the property optimization step with improved powerful and accurate computational modeling tools. However, while the ability of computational models to be used in this way is not new, models that have been developed in this space have consistently underperformed. Oftentimes, these models fail because they fail to accurately account for the various physical and chemical mechanisms that are driving the system, or because they fail to account for all of the variables which must be included. Here we propose a standard method of communication for these relationships in the form a process-structure-property-performance map, which leverages the known knowledge database of the material system to clearly and visually communicate the relevant variables and their various relationships in a defined materials design space. Such a map is developed here for high-strength Al-Zn-Mg-Cu alloys, which offer a good example of a material system which could benefit from such a standard. This class of alloys, which are typically utilized in aircraft components, have been incorporated in commercial components for nearly 75 years, and due to its long history is a well characterized and well developed system that is highly suited to this kind of examination. In Part I of this work, we develop this standard by first examining the known knowledge database in this system to deduce what the important process, microstructure, and mechanical property variables are that are of interest. Once these variables and the relationships between them are identified, they are organized into a PSPP map according to a proposed set of steps, and can act as a visual standard that can clearly communicate critical information about the mechanisms of the system. For example, if a model developed within this system does not include a variable or a mechanism depicted within the map, it can be used to communicate the ways in which the model will be constrained. Similarly, when experimental data is collected within this space the map can be used to clearly communicate which variables in the space were held constant, which variables were tracked and accurately measured, and if any variables were unaccounted for. This information can help to communicate what situations the data can be used in, and how the space that the experimental data can be used in is constrained. In Part II of this work, we vary multiple parameters within the high-strength Al-Zn-Mg-Cu system defined in Part I, and attempted to track and measure as many of the variables within the space as possible using commonly available testing and characterization methods. In tackling such a large project in the complicated materials system of high-strength wrought Al-Zn-Mg-Cu alloys, we are able to understand which current testing and characterization methods are well suited to tracking these variables when the number of test specimens becomes quite large and when variability among those specimens is involved. We are also able to identify opportunities for future work in this area, which could be focused on improving our ability to implement projects of the scope that is required here. In addition to evaluating the feasibility of the various measurement and characterization methods, the raw data and the analyzed results for this work are cataloged in an associated data repository and have been made available for use in future work in this and other areas.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23023号 / 理博第4700号 / 新制||理||1674(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 島川 祐一, 教授 寺西 利治, 教授 長谷川 健 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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This study examined several features of flexible polyurethane foams from a structure-property perspective. A major part of this dissertation addresses the issue of connectivity of the urea phase and its influence on mechanical and viscoelastic properties of flexible polyurethane foams and their plaque counterparts. Lithium salts (LiCl and LiBr) were used as additives to systematically alter the phase separation behavior, and hence the connectivity of the urea phase at different scale lengths. Macro connectivity, or the association of the large scale urea rich aggregates typically observed in flexible polyurethane foams was assessed using SAXS, TEM, and AFM. These techniques showed that including a lithium salt in the foam formulation suppressed the formation of the urea aggregates and thus led to a loss in the macro level connectivity of the urea phase. WAXS and FTIR were used to demonstrate that addition of LiCl or LiBr systematically disrupted the local ordering of the hard segments within the microdomains, i.e., it led to a reduction of micro level connectivity or the regularity in segmental packing of the urea phase. Based on these observations, the interaction of the lithium salt was thought to predominantly occur with the urea hard segments, and this hypothesis was confirmed using quantum mechanical calculations. Another feature of this research investigated model trisegmented polyurethanes based on monofunctional polyols, or "monols", with water-extended toluene diisocyanate (TDI) based hard segments. The formulations of the monol materials were maintained similar to those of flexible polyurethane foams with the exceptions that the conventional polyol was substituted by an oligomeric monofunctional polyether of ca. 1000 g/mol molecular weight. Plaques formed from these model systems were shown to be solid materials even at their relatively low molecular weights of 3000 g/mol and less. AFM phase images, for the first time, revealed the ability of the hard segments to self-assemble and form lath-like percolated structures, resulting in solid plaques, even though the overall volume of the system was known to be dominated by the two terminal liquid-like polyether segments. In another aspect of this research, foams were investigated in which the ratios of the 2,4 and 2,6 TDI isomers were varied. The three commercially available TDI mixtures, i.e., 65:35 2,4/2,6 TDI, 80:20 2,4/2,6 TDI, and 100:0 2,4/2,6 TDI were used. These foams were shown to display marked differences in their cellular structure (SEM), urea aggregation behavior (TEM), and in the hydrogen bonding characteristics of the hard segments (FTIR). Finally, the nanoscale morphology of a series of 'model' segmented polyurethane elastomers, based on 1,4-butanediol extended piperazine based hard segments and poly(tetramethylene oxide) soft segments, was also investigated using AFM. The monodisperse hard segments of these 'model' polyurethanes contained precisely either one, two, three, or four repeating units. Not only did AFM image the microphase separated morphology of these polyurethanes, but it also revealed that the hard domains preferentially oriented with their long axis along the radial direction of the spherulites which they formed. / Ph. D.

Blendas poliméricas são largamente utilizadas nas indústrias de pneus por causa de seu baixo custo e das melhores propriedades que podem ser obtidas. Quando os componentes da blenda não são miscíveis entre si, métodos de compatibilização química (utilizando agentes compatibilizantes) ou mecânica (aumentando o tempo de mistura dos elastômeros) são necessários para melhorar a compatibilidade dos componentes da mistura. Neste trabalho, o Trans-Polioctenileno (TOR) foi usado como agente compatibilizante da blenda de NR/SBR. A viscosidade Mooney, a Carga e o Alongamento na Ruptura de diversas blendas foram avaliados, utilizando um planejamento fatorial. Os resultados obtidos mostraram que o TOR tem maior influência na alteração da viscosidade Mooney, seguido pelo tempo de premix e de repasse. No caso das propriedades dinamométricas, a carga e o alongamento na ruptura são mais sensíveis às alterações do tempo de processamento dos polímeros. O TOR leva a uma ligeira diminuição destas propriedades. Baseado nos resultados estatísticos, equações de regressão para avaliar as propriedades estudadas em função da concentração de TOR e do tempo de processamento foram propostos e posteriormente verificados, utilizando blendas que não estavam incluídas no planejamento original. Os resultados foram bastante satisfatórios, tanto na determinação dos efeitos das variáveis quanto na determinação das equações. Concluiu-se que a viscosidade Mooney é mais sensível às alterações da concentração de TOR do que às alterações do tempo de mistura dos elastômeros e que as propriedades dinamométricas são mais afetadas pelo tempo de processamento. / Polymer blends are used in tyre industries because of their low cost and better properties. When the blend components are not miscible, chemical methods (using compatibilizing agents) or mechanical methods (increasing the mixture time of elastomers) of compatibilization are necessary to improve the compatibility of the components of the blend. In this work, Trans-Polyoctenylene Rubber (TOR) was used as a compatibilizing agent of the NR/SBR rubber blend. The Mooney viscosity, stress and elongation at break of different blends were evaluated, using a Factorial Design. The experimental results obtained showed that the Mooney viscosity is greatly affected by the addition of TOR whereas the dynamometric properties, the stress and elongation at break are more sensitive to the changes of processing time of polymers. Based on statistical results, regression equations to evaluate the properties studied as a function of TOR concentration and processing time were obtained and verified using blends which were not on the original design. The results were very satisfactory, either on the effects determination or on the regression equation determination. It was concluded that the Mooney viscosity is more sensitive to the alterations of TOR concentration than the changes in the processing time of the elastomers and the dynamometric properties are more affected by the processing time.

Blendas poliméricas são largamente utilizadas nas indústrias de pneus por causa de seu baixo custo e das melhores propriedades que podem ser obtidas. Quando os componentes da blenda não são miscíveis entre si, métodos de compatibilização química (utilizando agentes compatibilizantes) ou mecânica (aumentando o tempo de mistura dos elastômeros) são necessários para melhorar a compatibilidade dos componentes da mistura. Neste trabalho, o Trans-Polioctenileno (TOR) foi usado como agente compatibilizante da blenda de NR/SBR. A viscosidade Mooney, a Carga e o Alongamento na Ruptura de diversas blendas foram avaliados, utilizando um planejamento fatorial. Os resultados obtidos mostraram que o TOR tem maior influência na alteração da viscosidade Mooney, seguido pelo tempo de premix e de repasse. No caso das propriedades dinamométricas, a carga e o alongamento na ruptura são mais sensíveis às alterações do tempo de processamento dos polímeros. O TOR leva a uma ligeira diminuição destas propriedades. Baseado nos resultados estatísticos, equações de regressão para avaliar as propriedades estudadas em função da concentração de TOR e do tempo de processamento foram propostos e posteriormente verificados, utilizando blendas que não estavam incluídas no planejamento original. Os resultados foram bastante satisfatórios, tanto na determinação dos efeitos das variáveis quanto na determinação das equações. Concluiu-se que a viscosidade Mooney é mais sensível às alterações da concentração de TOR do que às alterações do tempo de mistura dos elastômeros e que as propriedades dinamométricas são mais afetadas pelo tempo de processamento. / Polymer blends are used in tyre industries because of their low cost and better properties. When the blend components are not miscible, chemical methods (using compatibilizing agents) or mechanical methods (increasing the mixture time of elastomers) of compatibilization are necessary to improve the compatibility of the components of the blend. In this work, Trans-Polyoctenylene Rubber (TOR) was used as a compatibilizing agent of the NR/SBR rubber blend. The Mooney viscosity, stress and elongation at break of different blends were evaluated, using a Factorial Design. The experimental results obtained showed that the Mooney viscosity is greatly affected by the addition of TOR whereas the dynamometric properties, the stress and elongation at break are more sensitive to the changes of processing time of polymers. Based on statistical results, regression equations to evaluate the properties studied as a function of TOR concentration and processing time were obtained and verified using blends which were not on the original design. The results were very satisfactory, either on the effects determination or on the regression equation determination. It was concluded that the Mooney viscosity is more sensitive to the alterations of TOR concentration than the changes in the processing time of the elastomers and the dynamometric properties are more affected by the processing time.

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Aromatic polyimides have found widespread applicability which can be partially attributed to their thermal stability, chemical resistance, and high glass transition temperature. However, deficiencies in their processability, solubility, transparency, and relatively high dielectric constants do not always provide the optimum properties for many specialty microelectronics applications. The incorporation of aliphatic segments to form partially aliphatic polyimides, has been used to counteract these shortcomings. Many of the potential uses of partially aliphatic polyimides require them to adhere to ceramic substrates, a main topic of this research. Polyimides and copolyimides that varied in chemical composition by their aliphatic content were characterized by their molecular weight, glass transition temperature, thermal stability, coefficient of thermal expansion, refractive index, dielectric behavior, and mechanical properties. Structure-property relationships were established. The gamma and beta sub-Tg viscoelastic relaxations were investigated to understand their molecular origins. The adhesion performance of a selected series of partially aliphatic polyimides to SiO2/Si was examined using a shaft loaded blister test, which was designed and instrumented for use in a dynamic mechanical analysis instrument. The adhesion was studied at high and low percent relative humidities and for several temperatures to examine if adhesion strength is influenced by polymer chemical composition. The adhesion energy could not be quantified for the entire series of polyimides. It was possible to interpret the quantitative adhesive fracture energies along with the qualitative adhesion strength behaviors, the failure surface analyses, and to offer an understanding of the adhesive chemical structure-physical property relationships. These understandings provide a conclusion that the incorporation of aliphatic segments into the polyimide chemical structure improves the durability of the adhesive bond to SiO2/Si under high percent relative humidities. / Ph. D.

Yes / Thermoplastic polyurethane (TPU)/multi-walled carbon nanotubes (CNT) nanocomposites were prepared by twin-screw extrusion and micro injection molding. The electrical conductivity of micro injection molded polymer nanocomposites exhibits a low value and uneven distribution in the micromolded samples. Real-time tracing of electrical conductivity was conducted to investigate the post thermal treatment on the electrical conductivity of microinjection molded composites. The results show that postmolding thermal treatment leads to a significant increase in the electrical conductivity by over three orders of magnitude for 5 wt % CNT-filled TPU composites. In-situ Transmission electron microscopy confirms the conductive CNT network does not change at the micron/sub-micron scale during thermal treatment. TEM image analysis by a statistical method was used to determine the spatial distribution of CNT in the sample and showed that the average distance between adjacent CNT reduced slightly at the nanometer scale after postmolding thermal treatment. A new conductive mechanism is proposed to explain the enhancement of electrical conductivity after thermal treatment, i.e. micro-contact reconstruction of adjacent CNT in the polymer matrix through annealing-induced relaxation of interfacial residual stress and strain. Raman spectra and small angle X-ray scattering curve of annealed samples provide supporting evidence for the proposed new conductive mechanism. The electron tunneling model was used to understand the effect of inter-particle distance on the conductivity of polymer composites. / Chinese Ministry of Education. Grant Number: 313036; National Natural Science Foundation of China. Grant Number: 51433006