Linear and branched poly(butylene adipate) polyesters with number-average molecular weights ranging from 700 to 10 000 g/mol, and degrees of branching ranging from very low to hyperbranched were solution cast with PVC to study the effects of chemical structure, molecular weight, end-group functionality, and chain architecture on plasticizing efficiency and durability. Miscibility was evaluated by the existence of a single glass transition temperature and a shift of the carbonyl group absorption band. Desirable mechanical properties were achieved in flexible PVC films containing 40 weight-% of polyester plasticizer. Methyl-ester-terminated polyesters with a low degree of branching and an intermediate molecular weight enhanced the plasticizing efficiency, as shown by greater elongation, good miscibility, and reduced surface segregation. A solid-phase extraction method was developed to extract the low molecular weight products that migrated from pure poly(butylene adipate) and PVC/ poly(butylene adipate) films during aging in water. The effects of branching, molecular weight, end-group functionality, and polydispersity on plasticizer permanence were evaluated by quantification of low molecular weight hydrolysis products, weight loss, surface segregation, and the preservation of material properties during aging. A more migration-resistant polymeric plasticizer was obtained by combining a low degree of branching, hydrolysis-protecting end-groups, and higher molecular weight of the polyester. Films plasticized with a slightly branched polyester showed the best durability and preservation of material and mechanical properties during aging. A high degree of branching resulted in partial miscibility with PVC, poor mechanical properties, and low migration resistance. The thermal stability of polyester-plasticized films was higher than that of films containing a low molecular weight plasticizer, and the stabilizing effect increased with increasing plasticizer concentration. / QC 20100805

Many pharmaceutical compounds being developed in recent years are poorly soluble in water. This has led to insufficient oral bioavailability of many compounds in vitro. The amorphous formulation is one of the promising techniques to increase the oral bioavailability of these poorly water-soluble compounds. However, an amorphous drug substance is inherently unstable because it is a high energy form. In order to increase the physical stability, the amorphous drug is often formulated with a suitable polymer to form an amorphous solid dispersion. Previous research has suggested that the formation of an intimately mixed drug-polymer mixture contributes to the stabilization of the amorphous drug compound. The goal of this research is to better understand the role of miscibility, molecular interactions and mobility on the physical stability of amorphous solid dispersions. Methods were developed to detect different degrees of miscibility on nanometer scale and to quantify the extent of hydrogen-bonding interactions between the drug and the polymer. Miscibility, hydrogen-bonding interactions and molecular mobility were correlated with physical stability during a six-month period using three model systems. Overall, this research provides molecular-level insights into many factors that govern the physical stability of amorphous solid dispersions which can lead to a more effective design of stable amorphous formulations.

Minimum miscibility pressure (MMP) is a key parameter in the design of gas flooding. There are experimental and computational methods to determine MMP. Computational methods are fast and convenient alternatives to otherwise slow and expensive experimental procedures. This research focuses on the computational aspects of MMP estimation. It investigates the shortcomings of the current computational models and offers ways to improve the robustness of MMP estimation. First, we develop a new mixing cell method of estimating MMP that, unlike previous "mixing cell" methods, uses a variable number of cells and is independent of gas-oil ratio, volume of the cells, excess oil volumes, and the amount of gas injected. The new method relies entirely on robust P-T flash calculations using any cubic equation-of-state (EOS). We show that mixing cell MMPs are comparable with those of other analytical and experimental methods, and that our mixing cell method finds all the key tie lines predicted by MOC; however, the method proved to be more robust and reliable than current analytical methods. Second, we identify a number of problems with analytical methods of MMP estimation, and demonstrate them using real oil characterization examples. We show that the current MOC results, which assume that shocks exist from one key tie line to the next may not be reliable and may lead to large errors in MMP estimation. In such cases, the key tie lines determined using the MOC method do not control miscibility, likely as a result of the onset of L₁-L₂-V behavior. We explain the problem with a simplified pseudo-ternary model and offer a procedure for determining when an error exists and for improving the results. Finally, we present a simple mathematical model for predicting the MMP of contaminated gas. Injection-gas compositions often vary during the life of a gasflood because of reinjection and mixing of fluids in situ. Determining the MMP by slim-tube or other methods for each possible variation in the gas-mixture composition is impractical. Our method gives an easy and accurate way to determine impure CO₂ MMPs for variable field solvent compositions on the basis of just a few MMPs. Alternatively, the approach could be used to estimate the enrichment level required to lower the MMP to a desired pressure. / text

This study concentrates on the modelling of three phase flow and miscible CO2 flooding in pore networks that captures the natural porous medium of a reservoir. That is to say, the network, that is a Matlab code, consists of different sided triangles which are located randomly through the grids. The throats that connect the pores are also created by the model. Hence, the lengths and the radii of the throats are varying. The network used in this research is assumed to be representative of mixed-wet carbonates in 2-D. Mixed wettability arises in real porous media when oil renders surfaces it comes into prolonged contact with oil-wet while water-filled nooks and crannies remain water-wet. The model developed is quasi-static approach to simulate two phase and three phase flows. By this, capillary pressures, relative permeabilities, saturations, flow paths are determined for primary drainage, secondary imbibition, and CO2 injection cases. To calculate the relative permeability, capillary entry pressures are first determined. Then, hydraulic conductances and flow rates of the network for each grid are obtained. Phase areas and saturations are also determined. It is accepted that the displacement mechanism in drainage and CO2 injection is piston-like whereas in imbibition it is either piston-like or snap-off. The results of the model are compared with the experimental data from the literature. Although, the pore size distribution and the contact angle of the model are inconsistent with the experimental data, the agreement of the relative permeabilities is promising. The effect of contact angle in the same network for three phase flow where immiscible CO2 is injected as a third phase at supercritical temperature (32 &deg / C) is investigated. And it is found that, the increase in the intrinsic angles causes decrease in relative permeability values. As another scenario, two phase model is developed in which miscible CO2 &amp / #8211 / water is flooded after the primary drainage of the same 2-D network at supercritical temperature (32 &deg / C). This case is compared with the previous case and the effects of miscibility are investigated such that it causes the relative permeability values to increase. Adsorption is another concern of which its effects are analyzed in a single pore model. The model is compared with the reported experimental data at high temperature and pressures. A reasonable fit is obtained.

[pt] Blenda polimérica é a mistura física de dois ou mais polímeros, sem reação química intencional entre os componentes. O objetivo básico é combinar as melhores propriedades de cada componente da blenda que, consequentemente, terá propriedades intermediárias àquelas dos polímeros misturados. As maiores vantagens das blendas são a grande variedade e a versatilidade de suas aplicações, que, somadas à facilidade de processamento, possibilitam a produção dos mais diversos produtos, tornando-as competitivas em relação a outros materiais. Outra finalidade das blendas é otimizar a relação custo/benefício e melhorar a processabilidade de polímeros de alta temperatura. Os materiais utilizados neste trabalho foram o PEAD e a PA12, ambos os polímeros sendo de grande importância industrial. O objetivo do trabalho é produzir blendas poliméricas de PEAD/PA12, avaliar a sua miscibilidade e realizar ensaios para extrair suas propriedades. As blendas foram feitas em três composições: 75/25, 50/50 e 25/75 e foi feita a caracterização mecânica com ensaios de tração e fluência, química com análise FTIR e DRX, reológica e análise por MEV e os resultados foram usados para avaliar a combinação das propriedades dos polímeros puros nestas blendas. / [en] Polymer blend is the physical mixture of two or more polymers without any intentional chemical reaction between the components. The basic goal is to combine the best properties of each blend component that, consequently, will have intermediary properties to those of the polymers used. The biggest advantages of the blends are the great variety and the versatility on their applications that added to the good processability, make possible the production of many products making them competitive in relation to other materials. Another objective of the blends is to optimize the cost/benefit relation and improve the processability of high temperature polymers. The materials used on this work were the HDPE and the PA12, both polymers being of great industrial importance. The interest of this work is to produce HDPE/PA12 blends and evaluate their miscibility and make tests to know their properties. The blends were made in three compositions: 75/25, 50/50 and 25/75 and it was done the mechanical characterization with uniaxial tension and creep behavior, chemical characterization with FTIR analysis and x-ray diffraction, rheology and SEM analysis and the results were used to evaluate the combination of the properties of the neat polymers used in these blends.

No description available.

Phosphorus-containing high performance polymers have been extensively studied during the last 10 years. These materials are of interest for a variety of optical and fire resistant properties, as well as for their ability to complex with the inorganic salts. This dissertation has focused on the nature of the phosphonyl group interactions with hydroxyl containing polymers, such as the poly(hydroxy ether)s. These may be considered linear models of epoxy resins and are also closely related to dimethacrylate (vinyl ester) matrix resins that are important for composite systems. It has been shown that bisphenol A poly(arylene ether phosphine oxide/sulfone) homo- or statistical copolymers are miscible with a bisphenol A-epichlorohydrin based poly(hydroxy ethers) (PHE), as shown by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), infrared spectroscopy and , solid state cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS). These measurements illustrate the strong hydrogen bonding between the phosphonyl groups of the copolymers and the pendent hydroxyl groups of the PHE as the miscibility inducing mechanism. Complete miscibility at all blend compositions was achieved with as little as 20 mole% of phosphine oxide units in the poly(arylene ether) copolymer. Replacement of the bisphenol A moiety by other diphenols, such as hydroquinone, hexafluorobisphenol A and biphenol did not significantly affect blend miscibilities. Miscible polymer blends with PHE were also made by blending poly(arylene thioether phosphine oxide), and fully cyclized phosphine oxide containing polyimides based on (prepared from 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and bis(m-aminophenyl) methyl phosphine oxide (DAMPO)) or bis(m-aminophenyl) phenyl phosphine oxide). Additional research has focused on the influence of these materials on the property characteristics of vinyl ester matrix resins and has shown that the concentration of phosphonyl groups controls the homogeneity of both oligomers and the resulting networks. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fracture toughness measurements further confirmed the qualitative observations. Metal salts, such as CoCl2 and CuCl2 had earlier been demonstrated to form complexes/nanocomposites with phosphorus-containing poly(arylene ethers). It has been possible to prepare transparent films with 100 mol% of metal chlorides, based upon the phosphonyl groups. The films are transparent, unlike the opaque polysulfone control systems. FTIR results suggested the formation of inorganic salt and polymer complexes at low concentrations. TEM showed homogeneous morphology at low concentrations and excellent dispersion even at high mole % of salts. Cobalt materials reinforce the basic poly(arylene ether)s to provide higher modulus values and influence positively the char yield generated after TGA experiments in air. The cobalt salt/BPADA-DAMPO polyimide composites also yield transparent films, implying very small dimensions. Silica-polymer nanocomposites were also produced by mixing commercial silica colloid/N,N-dimethylacetamide (DMAc) fine dispersions (~ 12 nm) with bisphenol A poly(arylene ether phenyl phosphine oxide). The dry films produced by solution casting are transparent and silica colloids are evenly dispersed (~ 12 nm) into the polymer matrix as shown by TEM. These nanocomposites increased char yield compared with the polymer control, suggesting their fire retardant character. In comparison, the silica/polysulfone hybrid films prepared by the same methods were opaque and the char yield was not improved. This different phase behavior has been explained to be due to the hydrogen bonding between phosphonyl groups and silanol hydroxyl groups on the surface of the nanosilica. / Ph. D.

This dissertation discusses the polymorphism, crystallization and melting behavior of propylene-ethylene random copolymers. It also discusses the results of studies of the miscibility and the competitive liquid-liquid demixing and crystallization processes in blends of poly(propylene) and poly(1-butene). In the first part of this study, polymorphism of propylene-ethylene copolymers is studied by wide angle X-ray diffraction. By comparing the a and y crystal phase contents in samples with different ethylene content as well as samples isothermally crystallized at different temperatures, it was shown that increasing ethylene content as well as increasing crystallization temperature promotes the formation of the y-phase. Comparison of the results from fractionated samples and unfractionated samples with similar ethylene contents reveals that in propylene-ethylene copolymers with similar micro-structure, the polymorphism, crystallization and melting behavior are mainly determined by their ethylene content. The issue of co-unit inclusion and its effect on crystallization and melting behavior are also discussed. In the second part of this dissertation, the miscibility behavior of atactic - poly(propylene) (at-PP) and atactic poly(1-butene) (ai-P1B) with different molecular weights is investigated by differential scanning calorimetry. The phase diagram of at-PP and at-P1B blend of molecular weight (87K/48.5K) shows a upper critical solution temperature (UCST) behavior. The UCST behavior is consistent with predictions by the group contribution method. Miscibility behavior of high molecular weight isotactic poly(propylene) (it-PP) and isotactic poly(1-butene) (it-P1B) blend is investigated by a combination of optical microscopy and scanning electron microscopy, differential scanning calorimetry and dynamic mechanical analysis. These studies reveal that for the molecular weights investigated, it-PP and it-P1B form blends that are partially miscible in the liquid state. Liquid-liquid demixing is observed by optical microscopy at temperatures above the melting temperature of the it-PP component and is also inferred from scanning electron micrographs of the freeze fracture surface of quenched blends after extraction of the it- P1B component with cyclohexane. It-PP spherulites grow through both liquid phases at relative rates that depend markedly on the crystallization temperature. The complex multiple-melting behavior of the it-PP component in the blend is explained in terms of a bimodal distribution of it-PP lamellar crystals which result from crystal growth in the phase-separated liquid. Finally, the dynamic mechanical analysis data are explained in terms of a liquid-liquid demixing process that results in a significant degree of phase mixing. / Ph. D.

Benefited from the efficiency of hydraulic fracturing and horizon drilling, the production of unconventional oil and gas resources, such as shale gas and tight oil, has grown quickly in 21th century and contributed to the North America oil and gas production. Although the new enhancing oil recover (EOR) technologies and strong demand spike the production of unconventional resources, there are still unknowns in recovery mechanisms and phase behavior in tight rock reservoirs. In such environment, the phase behavior is altered by high capillary pressure owing to the nanoscale pore throats of shale rocks and it may also influence minimum miscibility pressure (MMP), which is an important parameter controlling gas floods for CO2 injection EOR. To investigate this influence, flash calculation is modified with considering capillary pressure and this work implements three different method to calculate MMP: method of characteristics (MOC); multiple mixing cell (MMC); and slim-tube simulation. The results show that CO2 minimum miscibility pressure in nanopore size reservoirs are affected by gas-oil capillary pressure owing to the alternation of key tie lines in displacement. The values of CO2-MMP from three different methods match well. Moreover, in tight rock reservoirs, the heterogeneous pore size distribution, such as the ones seen in fractured reservoirs, may affect the recovery mechanisms and MMP. This work also investigates the effect of pore size heterogeneity on multicomponent multiphase hydrocarbon fluid composition distribution and its subsequent influence on mass transfer through shale nanopores. According to the simulation results, compositional gradient forms in heterogeneous nanopores of tight reservoirs because oil and gas phase compositions depend on the pore size. Considering that permeability is small in tight rocks and shales, we expect that mass transfer within heterogeneous pore size porous media to be diffusion-dominated. Our results imply that there can be a selective matrix-fracture component mass transfer during both primary production and gas injection secondary recovery in fractured shale rocks. Therefore, molecular diffusion should not be neglected from mass transfer equations for simulations of gas injection EOR or primary recovery of heterogeneous shale reservoirs with pore size distribution. / Master of Science / The new technologies to recover unconventional resources in oil and gas industry, such as fracturing and horizontal drilling, boosted the production of shale gas and tight oil in 21st century and contributed to the North America oil and gas production. Although the new technologies and strong demand spiked the production of tight oil resources, there are still unknowns of oil and gas flow mechanisms in tight rock reservoirs. As we know, the oil and gas resources are stored in the pores of reservoir formation rock. During production process, the oil and gas are pushed into production wells by formation pressure. However, the pore radius of shale rock is extremely small (around nanometers), which reduces the flow rate of oil and gas and raises capillary pressure in pores. The high capillary pressure will alter the oil and gas phase behavior and it may influence the value of minimum miscibility pressure (MMP), which is an important design parameter for CO2 injection (an important technology to raise production). To investigate this influence, we changed classical model with considering capillary pressure and this modified model is implemented in different methods to calculate MMP. The results show that CO2 -MMP in shale reservoirs are affected by capillary pressure and the results from different methods match well. Moreover, in tight rock reservoirs, the heterogeneous pore size distribution, such as fractures in reservoirs, may affect the flow of oil and gas and MMP value. So, this work also investigates the effect of pore size heterogeneity on oil and gas flow mechanisms. According to the simulation results, compositional gradient forms in heterogeneous nanopores of tight reservoirs and this gradient will cause diffusion which will dominate the other fluid flow mechanisms. Therefore, we always need to consider molecular diffusion in the simulation model for shale reservoirs.

Neste trabalho foram efetuados estudos importantes e pioneiros sobre as propriedades estruturais, eletrônicas e termodinâmicas dos nitretos e de suas ligas, através de dois métodos de primeiros princípios distintos, o FLAPW (\"Full-potential Linear Augmented Plane Wave\") e o pseudopotencial combinado com a aproximação quasequímica generalizada. Na primeira parte, utilizando o método FLAPW, calculamos as estruturas de bandas para os nitretos cúbicos do grupo-IH, BN, AIN, GaN e InN. Foram obtidos valores para a constante de rede e \"bulk modulus\" para os nitretos do grupo-III através de cálculos relativísticos da energia total. Através das estruturas de bandas e analisando o topo da banda de valência e o fundo da banda de condução perto do ponto r ou, no ponto k correspondente ao mínimo da banda de condução, derivamos os respectivos valores para as massas efetivas de elétron e de buraco pesado, leve e de \"split-off\' e correspondentes parâmetros de Luttinger. Todos os resultados são comparados com dados experimentais e teóricos existentes na literatura. Na segunda parte, utilizando o método FLAPW, estudamos a influência da impureza de Mg na estrutura eletrônica do GaN cúbico (c-). Realizamos cálculos da otimização da geometria, incluindo deslocamentos dos primeiros e segundos vizinhos, para os casos da impureza com estados de carga neutro e negativo. Obtivemos o valor de 190 meV para o deslocamento de Franck-Condon da energia térmica, o qual apresenta um bom acordo com os dados experimentais de fotoluminescência e efeito Hall. Nós concluímos que os primeiros e segundos vizinhos desempenham um papel importante na determinação das energias do nível aceitador resultante da dopagem do c-GaN com Mg. Na terceira parte, nós apresentamos cálculos das propriedades eletrônicas, estruturais e termodinâmicas de ligas cúbicas envolvendo os nitretos do grupo-III, InxGa1-xN, InxAl-xN, AlxGal-xN, BxGal-xN e BxA1-xN. Nós combinamos o método de expansão de \"clusters\" através da aproximação quasequímica generalizada (\"Generalized Quasichemical Approximation -GQCA\") com cálculos de pseudopotenciais \"ab initio\" DFT-LDA. Para todas a ligas, exceto a de AlxGal-xN, encontramos separação de fase para temperaturas próximas das temperaturas de crescimento. Generalizamos o método de expansão de \"c1usters\" para estudar a influência da tensão biaxial. Encontramos uma significativa supressão da separação de fase induzida pela tensão para as ligas de InxGal-xN e InxAh-xN, sendo no caso da liga de InxGal_xN confirmado experimentalmente. Observamos também que flutuações da energia do \"gap\" da liga de InxGal-xN permitem definir valores mínimo e médio para a energia do \"gap\" com diferentes valores para o \"bowing\". Observamos que a tensão biaxial reduz as flutuações da energia do \"gap\", resultando em uma diminuição do valor do \"bowing\". Através deste estudo mostramos uma possível explicação para a discrepância experimental para valores do \"bowing\". / In this work we performed a pioneer theoretical study of structural, electronic and thermodynamic properties of the group-III nitrides and their alloys, by using two distinct first principles methods, the FLAPW full potential linear augmented plane wave and the pseudopotential-plane-wave method combined with the generalized quasichemical approximation. In the first part of our work, by using the FLAPW, we present the electronic band structures ofthe zinc-blende-type group-III nitrides compounds, BN, AIN, GaN, and InN. Lattice constant and bulk modulus are obtained from fuH relativistic total-energy calculations. Electron, heavy-, light-, and split-off-hole effective masses and corresponding Luttinger parameters are extracted from the band-structure calculations. A comparison with other available theoretical results and experimental data is made. In the second part of our work, by using the FLAPW method, the electronic structure of Mg impurity in zinc-blende (c-) GaN is investigated. Full geometry optimization calculations, including nearest and next-nearest neighbor displacements, were performed for the impurity in the neutral and negatively charged states. A value of 190 meV was obtained for the Franck-Condon shift to the thermal energy, which is in good agreement with that observed in recent low temperature photoluminescence and Hall-effect measurements. We conclude that the nearest and the next-nearest neighbors of the Mg impurity replacing Ga in c-GaN undergo outward relaxations which play an important role in the determination ofthe center acceptor energies. In the third part of our work, we present a study of electronic, structural, and thermodynamic properties of the cubic group-III nitrides alloys, InxGal-xN, InxAll_xN, AlxGal-xN, BxGal-xN e BxAll-xN. We combined the generalized quasichemical approximation (GQCA) with an ab initio pseudopotential-plane-wave method. For alI alIoys, except the AlxGal-xN, we observe a miscibility gap for temperatures near those of the growth. The cluster treatment is generalized to study the influence of biaxial strain. We find a remarkable suppression ofphase separation in InxGal-xN and InxAll-xN induced by strain which is confirmed by experiments on the InxGal_xN alloy. We also observed that the gap fluctuations in the InxGal-xN alloy allow the definition of a minimum gap and an average gap with different bowing parameters. Biaxial strain drastically reduces the gap fluctuations, resulting in a reduction of the bowing. The different gaps and the strain influence investigated provide an explanation for the discrepancies found in the experimental values of the bowing parameter.