Expansive soils are widely found in many parts of the world. Highly active smectite clay mineral Montmorillonite is the major constituent in these clays and can expand or contract up to 15 times of their original volume. Constrained swelling exert large amount of stress causing damage to structures, pavements etc. These clays are also used as barrier materials, Nano-materials in polymer clay Nano composites and drug delivery systems. Several factors influence the swelling potential such as water content, density, voids, electrolyte content and cation exchange capacity. However, molecular scale mechanisms that control swelling behavior in these clays need to be understood. Objectives of this research are to provide an insight into mechanisms that result in swelling of these clays. Molecular modeling is used to build and study solvation of Na-Montmorillonite system. Trajectories of water molecules are captured and the evolutions of interaction energies with swelling are calculated.

<p> The short term (5000 hours) stability of illite and montmorillonite in sea water was studied by suspending 5.00 gm. aliquots of A.P.I. reference clays Montmorillonite # 25b and Illite # 35 in 500 ml. of artificial sea water (tradename "Instant Ocean") . After 5000 hours, in the montmorillonite samples, Ca and Si concentrations had increased (0.490 mmoles/l and 0.289 mmoles/l respectively), the cation exchange capacity had decreased (104.36 meq/100 gms. to 81.42 meq/100 gms.), the pH had decreased (8.40 to 7.94) but no major mineralogical change was observed. After 5000 hours, in the illite samples, Si concentration had increased (0.045 mmoles/l), the cation exchange capacity remained the same, the pH increased (7.22 to 7.60) and no major mineralogical change was observed. The release of Ca in the illite samples was complicated by the dissolution of calcite and significant changes in concentration of other cations (Na, K, Mg) were not observed.</p> <p> The data for Si, cation exchange and exchangeable cations are compared to that of Lewis (1950), Whitehouse and McCarter (1956), Carrol and Starkey (1958), MacKenzie et al (1965) (1967) and Russell (1970), a model developed by Houston (1972) is used to explain the Ca and Si data for the montmorillonite samples, and the implications of the apparent stability of these minerals to the case for authigenic clay formation from detrital material are discussed.</p> / Thesis / Bachelor of Science (BSc)

No description available.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The investigation of the barrier properties of highly filled polymer-clay hybrid latex films is described. Montmorillonite (MMT) clay contents ranging from 10–30 wt.% were effectively incorporated into polystyrene-butyl acrylate (PSBA) random copolymers, via miniemulsion polymerization. The optical properties of the films were evaluated using UV-Vis spectroscopy. Compared to the neat films, the PSBA nanocomposites retained remarkable visual properties. The light transmittance for PSBA films with styrene/n-butyl acrylate (S/BA) comonomer contents of 40:60 and 50:50 (mol.%) only decreased from 70% in the neat films to 50% in the nanocomposite films containing 30 wt.% clay. The best optical properties were observed in the films with S/BA comonomer contents of 30:70 (mol.%), the light transmittance only decreased from 85% (neat film) to 60% in the nanocomposite films containing 30 wt.% clay. The improved optical properties for the PSBA-30:70 films (compared to the PSBA-40:60 and PSBA-50:50 counterparts) were attributed to an increase in the low UV-absorbing butyl acrylate component of the copolymer, which at the same time has a low Tg that probably facilitated dispersion of the rigid MMT platelets in the matrix. In this study, the overall water vapour transport behaviour was governed by the MMT clay presence and less affected by the copolymer composition variation. The lower diffusion coefficients in the polymer clay nanocomposites (PCNs) were a result of the impermeable clay platelets which forced the water vapour molecules to follow longer and more tortuous paths to diffuse through the nanocomposite films. The irregular shape in the PSBA-40:60 and PSBA-30:70 neat latex particles was lost in the hybrid particles and well defined, dumb-bell shaped particles were observed. This was because of the faceting effect of the rigid MMT clay platelets. The MMT clay platelets were predominantly adhered to the surface of the PSBA latex particles because MMT clay particles have a larger size than the effective size of the copolymer particles. The stable overall transport coefficients in the PSBA-30:70-MMT films were attributed to the morphological organization of clay platelets in the matrix. The storage modulus of the materials decreased with an increase in clay content. This was attributed to the dual role played by the organoclay, firstly as nanofiller and reinforcing agent leading to the increase in storage modulus, and secondly as a plasticizer leading to a decrease of storage modulus. / AFRIKAANSE OPSOMMING: Die versperringseienskappe van hoogsgevulde polimeer-klei saamgestelde latekslae is beskryf. „n 10–30 wt % Montmorilloniet (MMT) klei inhoud is inkorporeer in polistireenbutielakrilaat (PSBA) onreëlmatige kopolimere, via miniemulsie polimerisasie. Die optiese eienskappe van die lae is bepaal m.b.v. UV-Vis spektroskopie. In vergelyking met die lae sonder klei (sogenaamde „neat films‟), het die PSBA nanosamestellings interressante visuele eienskappe getoon. Die ligtransmissie van die PSBA lae met „n stireeen/n-butielakrilaat (S/BA) komonomeerinhoud van 40:60 en 50:50 (mol %) het slegs afgeneem vanaf 70% in die „neat films‟ tot 50% in the nanosaamgestelde lae wat 30% klei bevat het. Die beste optiese eienskappe is waargeneem vir die lae wat „n 30:70 (mol %) S/BA komonomeerinhoud bevat het; die transmissie het slegs afgeneem vanaf 85% in die „neat films‟ to 60% in the nanosaamgestelde lae wat 30% klei bevat het. Die verbeterde optiese eienskappe van die PSBA-30:70 films (in vergelyking met die -40:60 and -50:50 films) is toegeskryf aan „n toename in die lae UV-absorberende butielakrilaat komponent van die kopolimeer. Terselfdetyd het laasgenoemde „n lae Tg-waarde, wat dispersie van die onbuigbare MMT kleiplaatjies in die matriks gefasiliteer het. In hierdie studie is die algehele waterdampvervoer deur die teenwoordigheid van die MMT klei beheer; dit is minder geaffekteer deur variasie in die samestelling van die kopolimeer. Die lae diffusiekoëffisiënte in die polimeer-klei nanosamestellings is as gevolg van die ondeurdringbare kleiplaatjies, wat die waterdampmolekules dwing om langs langer en meer gekronkelde paaie te diffundeer deur die nanosaamgestelde lae. Die onreëlmatige vorm wat gesien is in die PSBA-40:60 and PSBA-30:70 latekspartikels (sonder klei) het geleidelik verdwyn in die saamgestelde partikels, en goed-gedefineerde partikels met die vorm van handgewigte is waargeneem (in TEM beelde). Die rede hiervoor is die sogenaamde „faceting‟ effek, wat deur die onbuigbare MMT kleiplaatjies veroorsaak is. Die MMT kleiplaatjies sit hoofsaaklik aan die oppervlaktes van die PSBA latekspartikels. Die rede hiervoor is dat die MMT kleipartikels groter is as die effektiewe grootte van die kopolimeerpartikels. Die stabiele vervoerkoëffisiënte in die PSBA-30:70-MMT films is aan die unieke morfologiese eienskappe toegeskryf. Die bergingsmodulus van die materiale het monotonies afgeneem met „n toename in klei-inhoud. Dit is toegeskryf aan die tweedelige rol wat die organoklei speel – eerstens as 'n nanovuller en versterkingsmiddel, wat „n toename in bergingsmodulus tot gevolg het, en tweedens as „n plastiseerder, wat „n afname in bergingsmodulus tot gevolg het.

A quitosana tem se mostrado muito atrativa para a indústria farmacêutica, visando principalmente matrizes de liberação controlada com fármacos amplamente utilizados pela população em altas dosagens ou em períodos prolongada tal como o Ibuprofeno. O uso de combinado de polímeros e materiais como a argila é uma opção interessante, unindo as propriedades de ambos os materiais, minimizando o efeito colateral do fármaco. No presente trabalho descreve-se a preparação de um complexo iônico contendo quitosana e ibuprofeno por meio de uma reação ácido base entre ambos. Em uma segunda etapa, foi preparado um nanocompósito de montmorilonita/quitosana contendo o fármaco ibuprofeno. As matrizes foram caracterizadas por diferentes técnicas, incluindo análise elementar, ressonância magnética nuclear (RMN) de 13C e 1H, termogravimetria (TG), calorimetria exploratória diferencial (DSC), difração de raios X (DRX) e espectroscopia de infravermelho com transformada de Fourrier (FTIR). O grau de desacetilação (GD) da quitosana obtido por titulação potenciométrica foi de 80,0%. Esses resultados foram confirmados por medidas de RMN 1H e RMN 13C. O estudo dissociação do fármaco, na presença e na ausência de argila, foi avaliado por cromatografia líquida de alta eficiência (CLAE) e por espectroscopia de absorção eletrônica UV-VIS. A dissociação do fármaco em meio aquoso foi avaliada em pH 2 e 7, que correspondem aos valores encontrados no estômago e no intestino, respectivamente. Os resultados indicaram que a dissociação do ibuprofeno das matrizes é dependente do pH e que a presença da argila retarda a dissociação do fármaco na matriz. / Due to its interesting properties chitosan has attracted interest regarding several applications including drug carrier in pharmaceutical industry, mainly for actives consumed in high doses for long periods, as Ibuprofen. The combined use of materials such as polymers and the clay is an interesting option, combining the properties of both materials while minimizing the side effects of the drug. A chitosan-ibuprofen ionic complex had been prepared from the acid-base reaction between both of them. In a second step a montmorilonite/chitosan nanocomposite containing ibuprofen was also prepared. The complex and the nacomposite containing ibuprofen had been characterized by several techniques including elemental analysis, 13C e 1H, nuclear magnetic resonance (NMR), thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourrier transform infrared spectroscopy (FTIR). The chitosan degree of deacetylation (DD) was determined by potentiometry as 80.0%. These results were confirmed by 13C e 1H NMR. The dissociation of the pharmaceutical from the complex and nanocomposite was investigated by high performance liquid chromatography (HPLC) and electronic spectroscopy in the UV-vis (UV-vis). The dissociation of the pharmaceutical from the complex in aqueous media was evaluated in pH 2 and 7, corresponding to the stomach and intestines respectively. Results revealed that such dissociation is dependent of the pH of the medium as well as that release of Ibuprofen from the matrices is dependent on the pH and the presence of the clay slows the dissociation of the drug from the matrix.

Nanocomposites are a new class of mineral-field plastics that contain relatively small amounts (&lt / 10%) of nanometer-sized clay particles. The particles, due to their extremely high aspect ratios (about 100-15000), and high surface area (in excess of 750-800 m2/g) promise to improve structural, mechanical, flame retardant, thermal and barrier properties without substantially increasing the density or reducing the light transmission properties of the base polymer. Production of thermoplastic based nanocomposites involves melt mixing the base polymer and layered silicate powders that have been modified with hydroxyl terminated quaternary ammonium salt. During mixing, polymer chains diffuse from the bulk polymer into the van der Waals galleries between the silicate layers. In this study, new nanocomposite materials were produced from the components of recycled thermoplastic as the matrix and montmorillonite as the filler by using a co-rotating twin screw extruder. During the study, recycled poly(ethylene terepthalate), R-PET, was mixed with organically modified quaternary alkylammonium montmorillonite in the contents of 1, 2, and 5 weight %. Three types of clays were evaluated during the studies. For comparison, 2 weight % clay containing samples were prepared with three different clay types, Cloisite 15A, 25A, 30B. The nanocomposites were prepared at three different screw speeds, 150, 350, 500 rpm, in order to observe the property changes with the screw speed. Mechanical tests, scanning electron microscopy and melt flow index measurements were used to characterize the nanocomposites. The clay type of 25A having long alkyl sidegroups gave the best results in general. Owing to its branched nature, in nanocomposites with 25A mixing characteristics were enhanced leading to better dispersion of clay platelets. This effect was observed in the SEM micrographs as higher degrees of clay exfoliation. Nearly all the mechanical properties were found to increase with the processing speed of 350 rpm. In the studies, it was seen that the highest processing speed of 500 rpm does not give the material performance enhancements due to higher shear intensity which causes defect points in the structure. Also the residence time is smaller at high screw speeds, thus there is not enough time for exfoliation. In general, the MFI values showed minimum, thus the viscosity showed a maximum at the intermediate speed of 350 rpm. At this processing speed, maximum exfoliation took place giving rise to maximum viscosity. Also, the clay type of 25A produced the lowest MFI value at this speed, indicating the highest degree of exfoliation, highest viscosity, and best mechanical properties.

The Advanced Fuel Cycle Initiative (AFCI) is a Department of Energy (DOE) program, that has been investigating technologies to improve fuel cycle sustainability and proliferation resistance. One of the program's goals is to reduce the amount of radioactive waste requiring repository disposal. Cesium and strontium are two primary heat sources during the first 300 years of spent nuclear fuel's decay, specifically isotopes Cs-137 and Sr-90. Removal of these isotopes from spent nuclear fuel will reduce the activity of the bulk spent fuel, reducing the heat given off by the waste. Once the cesium and strontium are separated from the bulk of the spent nuclear fuel, the isotopes must be immobilized. This study is focused on a method to immobilize a cesium- and strontium-bearing radioactive liquid waste stream. While there are various schemes to remove these isotopes from spent fuel, this study has focused on a nitric acid based liquid waste. The waste liquid was mixed with the bentonite, dried then sintered. To be effective sintering temperatures from 1100 to 1200 degrees C were required, and waste concentrations must be at least 25 wt%. The product is a leach resistant ceramic solid with the waste elements embedded within alumino-silicates and a silicon rich phase. The cesium is primarily incorporated into pollucite and the strontium into a monoclinic feldspar. The simulated waste was prepared from nitrate salts of stable ions. These ions were limited to cesium, strontium, barium and rubidium. Barium and rubidium will be co-extracted during separation due to similar chemical properties to cesium and strontium. The waste liquid was added to the bentonite clay incrementally with drying steps between each addition. The dry powder was pressed and then sintered at various temperatures. The maximum loading tested is 32 wt. percent waste, which refers to 13.9 wt. percent cesium, 12.2 wt. percent barium, 4.1 wt. percent strontium, and 2.0 wt. percent rubidium. Lower loadings of waste were also tested. The final solid product was a hard dense ceramic with a density that varied from 2.12 g/cm3 for a 19% waste loading with a 1200 degrees C sintering temperature to 3.03 g/cm3 with a 29% waste loading and sintered at 1100 degrees C. Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA) of the loaded bentonite displayed mass loss steps which were consistent with water losses in pure bentonite. Water losses were complete after dehydroxylation at ~650 degrees C. No mass losses were evident beyond the dehydroxylation. The ceramic melts at temperatures greater than 1300 degrees C. Light flash analysis found heat capacities of the ceramic to be comparable to those of strontium and barium feldspars as well as pollucite. Thermal conductivity improved with higher sintering temperatures, attributed to lower porosity. Porosity was minimized in 1200 degrees C sinterings. Ceramics with waste loadings less than 25 wt% displayed slump, the lowest waste loading, 15 wt% bloated at a 1200 degrees C sintering. Waste loading above 25 wt% produced smooth uniform ceramics when sintered >1100 degrees C. Sintered bentonite may provide a simple alternative to vitrification and other engineered radioactive waste-forms.

Thesis (M.S. in Ch. E.)--School of Chemical Engineering, Georgia Institute of Technology, 2004. Directed by John D. Muzzy. / Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 30, 2007) Vita. Includes bibliographical references.

Thesis (M.S.)--University of North Texas, May, 2008. / Title from title page display. Includes bibliographical references.