A series of hybrid inorganic-organic composites were fabricated from a functionalized fluorinated polyimide and tetraethoxysilane (TEOS), tetramethoxysilane, methyltrimethoxysilane (MTMOS), and phenyltrimethoxy-silane (PTMOS) employing the sol-gel process. Polyimides were synthesized from 4,4'-hexafluoroisopropylidene dianiline (6FpDA) and 4,4'-hexafluoroisopropyl-idenediphthalic anhydride (6FDA) utilizing a solution imidization technique. The hybrid materials were synthesized by in-situ sol-gel processing of the aforementioned alkoxides and a fully imidized polyimide that was functionalized with 3-aminopropyltriethoxysilane. The gas permeability, diffusivity, and selectivity were evaluated for He, O2, N2, CH4, and CO2, while the physical properties of these hybrid materials were evaluated using several analytical techniques. The results from this study revealed that gas transport and physical properties were dependent on the type of alkoxide employed in the hybrid inorganic-organic material. Gas permeability was observed to increase with increasing gas penetrant size for MTMOS and PTMOS based hybrids, while TEOS based hybrids decreased gas permeability at all compositions. In general, MTMOS based hybrid materials had the largest increases in permeability, which was attributed to an increase in free volume. The TEOS based hybrid materials had the largest decreases in permeability, while PTMOS based hybrid materials had performance in between these alkoxides. Decreased permeability for the TEOS based hybrids was attributed to the formation of lower permeable material at a particle interface and coupled with increasing tortuosity. Results of PALS studies suggested that there was an increase in free volume and pore size for MTMOS based hybrids, while both TEOS and PTMOS based hybrids had decreases in both average pore size and free volume. The temperature dependence of permeation, diffusivity, and sorption were evaluated from 35oC to 125oC. These results suggested that there was a decrease in solubility for all hybrids employed in this study. Furthermore, increases in permeability for the MTMOS based hybrids were created by increased penetrant diffusion. Physical property studies revealed that the type of inorganic material incorporated into the hybrid influences the degree of swelling, bulk density, Tg, and thermal stability. Hybrid materials were also created employing 3,5-diaminobenzoic acid (DABA) in the synthesis of modified 6FDA-6FpDA polyimides in order to evaluate how improvements in inorganic and polymer compatibility influenced the gas transport properties. From this separate study, it was found that increases in both permeability and selectivity were possible. The mechanism attributed to this simultaneous increase in permeability and selectivity was the formation of a more permeable and selective interphase at the interface of an inorganic particle and the polymer matrix. In addition to these studies, 6FDA-6FpDA polyimide molecular weights were changed from 19.3K to 35.3K to probe its role on gas transport and physical properties. These studies revealed that permeability, diffusivity, and solubility increased with increasing molecular weight, while density decreased with increasing molecular weight. These results suggest that there is an increase in free volume with increasing 6FDA-6FpDA polyimide molecular weight. / Ph. D.

A vacuum permeability test utilizing high hydraulic gradients has been devised for compacted clay of low permeability. The test induces easily measurable flow rates in virtually impervious soils by placing a vacuum at the drainage end of the sample and an elevation head at the inflow end. The apparatus used in the test could easily be constructed with materials commonly available in laboratories for routine soil tests. The sample can either be compacted in the permeameter (a glass cylinder) or can be seated in sand and sealed with an asphalt bond. The anticipated difficulties, capillary effects, undetected leakage, and permeability reduction by entrapped air, do not introduce appreciable error as shown by the linearity of flow velocity-hydraulic gradient curves and the general agreement of test results with those obtained from a falling bead, non-vacuum test. Relative coefficients of permeability can be obtained within a few days after the start of the test. It is concluded that this rapid, inexpensive method gives adequate values of coefficient of permeability for most experimental work on compacted clays. / M.S.

A series of perfectly alternating polyimide/ poly(dimethylsiloxane) microphase separated block copolymers ranging from 0-50 wgt. % poly(dimethylsiloxane) have been measured for permeability characteristics. The polyimide segment of the copolymers was based on oxydiphthalicdianhydride (ODPA) and 1,4-Bis(4-amino-1,1- dimethylbenzyl)benzene (Bis P). The polysiloxane was an aminopropyl terminated poly(dimethylsiloxane). Randomly segmented block copolymers of =20 wet. % poly(dimethylsiloxane) with different segment lengths were also studied, based on the same materials for the sake of comparison with the perfectly alternating versions of the same block copolymers. Permeability measurements were performed on tough, microphase separated, transparent films with O₂, N₂, CH₄, and CO₂ gases in that order. The effects of the chemical composition and block lengths on permeability coefficients and selectivity values were evaluated. The permeability of copolymer films to gases was found to be highly sensitive to the morphology of the copolymer. The morphology was found to be controlled by varying the amount and the segment length of each component and this allowed for fine control of the permeability characteristics. Conversely, the measurement of permeability characteristics can lead to more information about the morphology of complicated microphase separated block copolymers. / Master of Science

The problem of degasification of coal beds is important because it is desirable to reduce the inflammable gas in coal mines as well as to recover economically the gas for use as a fuel. Permeability of coal is defined as a measure of the ease with which a gas flows through coal under a given pressure gradient, and it is of practical importance in the problem of degasification, The factors that affect the permeability of coal are also important in order to develop a more effective way of degasification. This study is concerned with the factors that affect the permeability of coal. Some of the major factors which affect the permeability of coal are the property of coal, properties of the natural coal gas, physical and chemical correlations between the coal and the gas, overburden pressure, and direction of the gas flow and other factors. In the case of these factors it is usually necessary to assess their effects in a qualitative way rather than in a quantitative one. For this reason, it would be impossible in the time allotted to this paper to present anything more than a brief discussion of their interrelationships. By experiment conducted for this thesis, it has been determined that (1) the permeability of coal differs from place to place, (2) the permeability of coal may or may not differ from bench to bench in the bed of a given location, (3) the permeability of dry coal does not differ significantly from that of wet coal, and also (4) in general, no significant difference in permeability was found when the gas flowed parallel to the coal bedding and when it flowed perpendicular to the coal bedding. / Master of Science

Convective heat transfer during hot pressing in wood-based composite panel manufacturing is widely accepted as the most important means of heat transport for resin curing. The rate of convective heat transfer to the panel core is controlled by its permeability. Permeability in the plane of the panel also controls the flow of vapor to the panel edges, thereby influencing the potential for panel "blowing". This research considers how flake thickness, flake alignment and changing mat density during hot-pressing influences OSB mat permeability, through its thickness and in the plane of the panel. Some previous research exists but it fails to address the affects of horizontal and vertical density gradients as well as flake alignment. An apparatus was designed to allow cold pressing of aligned flakes to desired densities while enabling permeability measurements through the mat thickness. An additional apparatus was designed to allow the measuring of permeability in the plane of the mat. These designs permitted permeability measurements in mats that had no vertical density gradient, allowing for the direct study of permeability versus density (compaction ratio). Superficial permeability was determined using Darcy's law and for each sample, multiple readings were made at five different pressure differentials. Permeability through the mat thickness was highly dependent on compaction ratio and to a lesser extent flake thickness. As the compaction ratio is increased, the initial reduction in permeability is severe, once higher compaction ratios are achieved the reduction in permeability is less pronounced. Permeability decreased with decreasing flake thickness. Permeability in the plane of the mat decreases with increasing compaction ratio but in a less severe manner than through the mat thickness. In this case, the permeability-compaction ratio relationship appears linear in nature. Again, permeability decreases with decreasing flake thickness. / Master of Science

The design, performance, and analysis of a soil vapor extraction system to identify zones most conductive to air transport and quantify kair in sequential soil layers is presented. A multi-level extraction well, with alternating solid and screened sections, was utilized to characterize multi-layered media. The field site, located in the Carolina Slate Belt within the physiographic region known as the Piedmont, is comprised of alternating layers of different soil types of varying kair, including thin bands of clay, silt, and sand. The pneumatic test consisted of one multi-level extraction well and four multi-level pressure monitoring wells. Screen locations were based on previous site characterization. Vapors were extracted at one screen while pressure, temperature, and volumetric flow rate were monitored using a computer data acquisition system. Data was analyzed by both steady-state and transient solution techniques using pressure drawdown versus time data collected at various locations. Results from vapor extraction tests indicate that the multi-level approach is advantageous when dealing with heterogenous media, since the most permeable layer was identified. Transient and steady-state solutions indicate that a k_air= 2.0 X 10⁻⁷ cm² is representative of the located permeable layer within the subsurface. Vacuum system, formation, and extraction well characteristics are evaluated to determine pressure as a function of volumetric flow rate. / Master of Science

Master of Science / Department of Civil Engineering / Yacoub M. Najjar / Reliable and economical design of Portland Cement Concrete (PCC) pavement structural systems relies on various factors, among which is the proper characterization of the expected permeability response of the concrete mixes. Permeability is a highly important factor which strongly relates the durability of concrete structures and pavement systems to changing environmental conditions. One of the most common environmental attacks which cause the deterioration of concrete structures is the corrosion of reinforcing steel due to chloride penetration. On an annual basis, corrosion-related structural repairs typically cost millions of dollars. This durability problem has gotten widespread interest in recent years due to its incidence rate and the associated high repair costs. For this reason, material characterization is one of the best methods to reduce repair costs. To properly characterize the permeability response of PCC pavement structure, the Kansas Department of Transportation (KDOT) generally runs the Rapid Chloride Permeability test to determine the resistance of concrete to penetration of chloride ions as well as the Boil test to determine the percent voids in hardened concrete. Rapid Chloride test typically measures the number of coulombs passing through a concrete sample over a period of six hours at a concrete age of 7, 28, and 56 days. Boil Test measures the volume of permeable pore space of the concrete sample over a period of five hours at a concrete age of 7, 28, and 56 days. In this research, backpropagation Artificial Neural Network (ANN)-based and Regression-based permeability response prediction models for Rapid Chloride and Boil tests are developed by using the databases provided by KDOT in order to reduce or eliminate the duration of the testing period. Moreover, another set of ANN- and Regression-based permeability prediction models, based on mix-design parameters, are developed using datasets obtained from the literature. The backpropagation ANN learning technique proved to be an efficient methodology to produce a relatively accurate permeability response prediction models. Comparison of the prediction accuracy of the developed ANN models and regression models proved that ANN models have outperformed their counterpart regression-based models. Overall, it can be inferred that the developed ANN-Based permeability prediction models are effective and applicable in characterizing the permeability response of concrete mixes used in transportation applications.

No description available.

Recent investigations into the permeability of the kidney capillaries have produced conflicting reports. This study was an attempt to better describe the permeability of the kidney capillaries by using narrow-range macromolecular dextran fractions in four molecular sizes: MW 61,400, MW 77,000, MW 118,000, and MW 147,000. Permeability was measured by dextran concentration differences in plasma and kidney lymph. Permeability decreased as the dextran molecular weight increased. Molecular weights 61,400 and 77,000 penetrated into the kidney lymph. Molecular weight 118,000 exhibited greater difficulty in penetrating to the lymph. The largest fraction penetrated into the kidney lymph with greatest difficulty. Plasma expansion by saline infusion increased the permeability of all dextran fractions.

A tendência atual de simplificação de sistemas adesivos transformou-os em polímeros altamente hidrofílicos e prontamente susceptíveis à permeação de água através de sua estrutura. Estudos recentes têm demonstrado que os sistemas adesivos simplificados se comportam como membranas semipermeáveis, permitindo o movimento de fluidos através da sua estrutura. Soluções a base de oxalato de potássio são efetivos agentes de redução da condutividade hidráulica dentinária. Quando são aplicados na dentina após o condicionamento ácido, podem ser utilizados em associação com os sistemas adesivos sem o comprometimento da adesão. Este trabalho objetivou avaliar os efeitos dos sistemas adesivos AdheSE, One Up Bond F e Single Bond, associados ou não a uma solução a base de oxalato de potássio, na condutividade hidráulica da dentina. Foram realizados preparos de coroas totais em terceiros molares humanos que tiveram suas raízes secionadas e a polpa coronária removida. Os segmentos coronários obtidos foram conectados ao ?Medidor de Fluxo? (Flodec?System, De marco Engineering, Switzerland). A condutividade hidráulica dos espécimes foi mensurada antes e após a aplicação dos sistemas adesivos Single Bond -3M ESPE, One UP Bond F -Tokuyama Inc, AdheSe- Ivoclar- Vivadent. Os adesivos foram aplicados seguindo as recomendações do fabricante (grupos SBF, ADF e OBF), de forma experimental (grupos ADE e OBE), e em combinação com uma solução a base de oxalato de potássio (grupos SBO, ADO e OBO). Cada espécime teve seu valor de permeabilidade original ( smear layer) e máxima (após condicionamento ácido) medidos anteriormente, os quais serviram como parâmetros para o cálculo das respectivas alterações frente aos tratamentos, expressas em porcentagem. Após a determinação da condutividade hidráulica, os preparos foram moldados para obtenção de réplicas em resina, as quais foram examinadas em MEV (JEOL 2800, Japão) para qualificar a permeação de fluido através do adesivo. A Análise de variância a 2 critérios mostrou que apesar dos procedimentos adesivos causarem uma redução significante (p< 0.05) na condutividade hidráulica da dentina condicionada, nenhum foi capaz de eliminar completamente a passagem de fluidos através do adesivo polimerizado. Para os três adesivos testados, o tratamento com o oxalato de potássio foi o tratamento mais eficaz na redução da permeabilidade dentinária e esta diferença foi estatisticamente significante quando comparada aos outros tratamentos (p<0,05). Não houve diferença entre os três sistemas adesivos estudados com relação à redução da permeabilidade dentinária (p> 0,05). A análise das réplicas em MEV mostrou que mesmo após a polimerização do adesivo, a transudação de fluidos pôde ser identificada na superfície de todas réplicas examinadas. Nenhum dos sistemas adesivos testados foi capaz de eliminar a permeação de fluidos através da dentina, contudo a associação destes adesivos com uma solução a base de oxalato de potássio reduziu de forma significante a permeabilidade dentinária. / There is an ongoing trend to move away from classical multi-component bonding systems toward simplified adhesives. An immediate consequence of adhesive simplification is the intrinsic permeability to water that result from their increase in hydrophilicity. Current studies have demonstrated that single-step adhesives may act as semi-permeable membranes that allow water diffusion through its structure. Oxalate desensitizers are effective in reducing the hydraulic conductance of dentin. When oxalates are used after acid- etching they do not interfere with subsequent resin bonding. The objective of this study was to test the effects of adhesives systems with or without the application of an oxalate desensitizer on dentin permeability. Crown preparations were made from human extracted teeth. After the roots were sectioned and the coronal pulp removed, the crown segments were connected to an automatic flow-recording device (Flodec-System, De Marco Engineering, Switzerland). Fluid conductance was measured before and after the bonding procedures with the adhesives Single Bond -3M ESPE, One UP Bond F -Tokuyama Inc and AdheSe- Ivoclar Vivadent. Specimens were prepared and tested after the surface had been bonded according to manufacturer?s instructions (SBF,ADF and OBF groups) , in a experimental way (ADE and OBE groups) or integrating with a oxalate desensitizer gel (SBO, ADO and OBO groups). For each specimen, fluid flow across the smear-layer and bonded dentin was expressed as a percentage of acidetched dentin, which was assigned a value of 100% flow rate. After the hydraulic conductance measures, impressions were taken from the crown segments and epoxy resin replicas were produced for SEM examination. Two-Way ANOVA reveled that the adhesive systems reduced dentin permeability significantly (p< 0.05) compared to acid etched dentin, but no bonding system was able to eliminate the fluid flow though dentin. For the three bonding systems tested, treating the acid-etched dentin with potassium oxalate prior to the application of the adhesive was the most effective in reducing the hydraulic conductance of the specimens, and this difference was significant (p< 0.05) when comparing to the other treatments. There were no significant differences among the adhesives in their ability to reduce dentin permeability (p> 0.05). SEM micrographs of resin replicas showed that transudation of dentinal fluid droplets could be identified on the surfaces of all replicas examined.