Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Orientador: Celso Valentim Santilli / Coorientador: Sandra Helena Pulcinelli / Banca: Leila Aparecida Chiavacci / Banca: Giancarlo Espósito de Souza Brito / Banca: Márcia Carvalho de Abreu Fantini / Banca: Francisco das Chagas Dantes de Lemos / Resumo: O primeiro objetivo deste trabalho foi investigar os fenômenos de agregação e de gelatinização das suspensões de TiO2 obtidos através do processo sol-gel. Estas suspensões foram preparadas a partir da hidrólise do tetraisopropóxido de titânio Ti(OPri)4 em solução aquosa de ácido para-toluenossulfônico (PTSH). A evolução do tamanho das nanopartículas e o mecanismo de agregação que ocorre nos momentos iniciais da reação foram analisados através da técnica de espalhamento de raios X à baixo ângulo (SAXS). Os resultados de SAXS mostraram que as partículas de TiO2 se agregam irreversivelmente formando partículas de tamanhos maiores nos momentos iniciais da reação. Também foram realizadas medidas de SAXS e reológicas para a suspensão com razão molar [H2O/Ti] = 2,3 e [PTSH/Ti] = 0,34, preparada com diferentes tempos de envelhecimento a 60ºC (0, 12 e 21 horas). Esse estudo revelou a possibilidade de aumentar tanto o tamanho das partículas do sol quanto a temperatura de transição sol-gel com o aumento do tempo de envelhecimento. Os valores de dimensões fractais (Df), obtidos pela técnica de SAXS, indicaram que a cinética de transição sol-gel é consistente com um processo de agregação cluster-cluster limitado por difusão (DLCCA). O segundo objetivo deste trabalho foi demonstrar a viabilidade de obter espumas cerâmicas a partir de emulsões formadas pela mistura dos sóis de TiO2 com o surfactante aniônico Dodecil Sulfato de Sódio (SDS) e não-iônico Pluronic F127 (P-127), juntamente com o óleo miristato de isopropila (MI). Nesta etapa, procurou-se avaliar o papel da natureza iônica e não-iônica dos surfactantes e da razão em massa/massa (m/m) de surfactante e da fase apolar (óleo) nas propriedades estruturais das espumas cerâmicas. O comportamento térmico, as fases cristalinas e a superfície das... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The first aim of this study was to investigate the aggregation and gelatinization of TiO2 suspensions obtained by the sol-gel process. The TiO2 suspensions were achieved by hydrolysis of the titanium tetraisopropoxide Ti(OPri)4 in para-toluene sulfonic acid (PTSH) aqueous solution. The evolution of nanoparticles size and the aggregation mechanism that occurs during the first synthesis step were analyzed by using small-angle X ray scattering (SAXS) technique. SAXS results have shown that TiO2 particles form irreversible aggregates giving rise to large particles during the first synthesis step. SAXS and rheological measurements were also carried out for the suspension prepared at H2O/Ti = 2.3 and PTSH/Ti = 0.34 molar ratios aged at 60 oC for different aging times (0, 12 and 21 h). This study has revealed the possibility to increase both the sol-gel phase transition temperature as well as the particle size by increasing the aging time. The fractal dimensionality (Df) values, estimated from the SAXS analyzes, indicated that particles aggregation is characteristic of a diffusion limited cluster-cluster aggregation (DLCCA) kinetic process. Another aim of this work was to obtain ceramic foams from emulsions formed by the mixture of TiO2 suspensions, the anionic Sodium Dodecyl Sulfate (SDS),or the non-ionic Pluronic F- 127 surfactants and the isopropyl myristate (MI) oil. This study was important to evaluate the role of the ionic or non-ionic nature of these two surfactants on the structural properties of the ceramic foam by varying the weight/weight (w/w) ratio of surfactant and non-polar phase (oil). The thermal behavior, crystalline structure and surface of the ceramic foams were investigated through thermogravimentry (TG), X ray diffraction (DRX), and X-ray photoelectron spectroscopy (XPS) techniques, respectively. These foams... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-09-12Bitstream added on 2014-06-13T19:21:31Z : No. of bitstreams: 1 silva_rfl_dr_araiq_parcial.pdf: 569879 bytes, checksum: 2457388d6cb16146915d8665b420386c (MD5) Bitstreams deleted on 2014-11-14T12:17:01Z: silva_rfl_dr_araiq_parcial.pdf,Bitstream added on 2014-11-14T12:17:47Z : No. of bitstreams: 1 000709052.pdf: 7363603 bytes, checksum: 2c4871700b9fe823e8770defc7894a0b (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O primeiro objetivo deste trabalho foi investigar os fenômenos de agregação e de gelatinização das suspensões de TiO2 obtidos através do processo sol-gel. Estas suspensões foram preparadas a partir da hidrólise do tetraisopropóxido de titânio Ti(OPri)4 em solução aquosa de ácido para-toluenossulfônico (PTSH). A evolução do tamanho das nanopartículas e o mecanismo de agregação que ocorre nos momentos iniciais da reação foram analisados através da técnica de espalhamento de raios X à baixo ângulo (SAXS). Os resultados de SAXS mostraram que as partículas de TiO2 se agregam irreversivelmente formando partículas de tamanhos maiores nos momentos iniciais da reação. Também foram realizadas medidas de SAXS e reológicas para a suspensão com razão molar [H2O/Ti] = 2,3 e [PTSH/Ti] = 0,34, preparada com diferentes tempos de envelhecimento a 60ºC (0, 12 e 21 horas). Esse estudo revelou a possibilidade de aumentar tanto o tamanho das partículas do sol quanto a temperatura de transição sol-gel com o aumento do tempo de envelhecimento. Os valores de dimensões fractais (Df), obtidos pela técnica de SAXS, indicaram que a cinética de transição sol-gel é consistente com um processo de agregação cluster-cluster limitado por difusão (DLCCA). O segundo objetivo deste trabalho foi demonstrar a viabilidade de obter espumas cerâmicas a partir de emulsões formadas pela mistura dos sóis de TiO2 com o surfactante aniônico Dodecil Sulfato de Sódio (SDS) e não-iônico Pluronic F127 (P-127), juntamente com o óleo miristato de isopropila (MI). Nesta etapa, procurou-se avaliar o papel da natureza iônica e não-iônica dos surfactantes e da razão em massa/massa (m/m) de surfactante e da fase apolar (óleo) nas propriedades estruturais das espumas cerâmicas. O comportamento térmico, as fases cristalinas e a superfície das... / The first aim of this study was to investigate the aggregation and gelatinization of TiO2 suspensions obtained by the sol-gel process. The TiO2 suspensions were achieved by hydrolysis of the titanium tetraisopropoxide Ti(OPri)4 in para-toluene sulfonic acid (PTSH) aqueous solution. The evolution of nanoparticles size and the aggregation mechanism that occurs during the first synthesis step were analyzed by using small-angle X ray scattering (SAXS) technique. SAXS results have shown that TiO2 particles form irreversible aggregates giving rise to large particles during the first synthesis step. SAXS and rheological measurements were also carried out for the suspension prepared at H2O/Ti = 2.3 and PTSH/Ti = 0.34 molar ratios aged at 60 oC for different aging times (0, 12 and 21 h). This study has revealed the possibility to increase both the sol-gel phase transition temperature as well as the particle size by increasing the aging time. The fractal dimensionality (Df) values, estimated from the SAXS analyzes, indicated that particles aggregation is characteristic of a diffusion limited cluster-cluster aggregation (DLCCA) kinetic process. Another aim of this work was to obtain ceramic foams from emulsions formed by the mixture of TiO2 suspensions, the anionic Sodium Dodecyl Sulfate (SDS),or the non-ionic Pluronic F- 127 surfactants and the isopropyl myristate (MI) oil. This study was important to evaluate the role of the ionic or non-ionic nature of these two surfactants on the structural properties of the ceramic foam by varying the weight/weight (w/w) ratio of surfactant and non-polar phase (oil). The thermal behavior, crystalline structure and surface of the ceramic foams were investigated through thermogravimentry (TG), X ray diffraction (DRX), and X-ray photoelectron spectroscopy (XPS) techniques, respectively. These foams... (Complete abstract click electronic access below)

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Due to the rising cost involve with bringing new fields on stream, of producing residual crude from matured fields, and the significant enhancement in oil recovery provided when compared to conventional water-flooding, increasing attention is being given to chemical flooding technologies. This is particular of interest in mature fields that had previously undergone water flooding. These methods entail injecting chemicals such as surfactant, alkali, and polymer often in mixture into reservoirs to improve oil recovery. In this study a sulfonated surfactant was produced from cheap waste vegetable oils and its performance was assessed in terms of thermal stability at reservoir conditions, adsorption on different reservoir materials, gas chromatography characterization and a limited interfacial tension measurement to evaluate its ability to improve the recovery of crude oil. Waste vegetable oils have great potential as a sustainable and low cost feedstock as well as its low toxicity.

Orientadores: Maria Helena Andrade Santana, Maria Vitoria Lopes Badra Bentley / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T23:17:39Z (GMT). No. of bitstreams: 1 Barbosa_RaqueldeMelo_M.pdf: 4198029 bytes, checksum: b5072f7f5d6c82c75879c1717e1946ed (MD5) Previous issue date: 2005 / Resumo: Resumo: Neste trabalho foi estudada a preparação e caracterização de lipossomas elásticos e elástico-magnéticos projetados para facilitar o transporte transdérmico de moléculas bioativas. Os lipossomas preparados foram do tipo unilamelar, compostos de dimiristoilfosfatidilcolina sintética (DMPC), fosfatidilcolina de soja hidrogenada ou fosfatidilcolina de ovo (PCovo) como componentes estruturais e dos tensoativos derivados do ácido láurico: 'C IND. 12¿¿E IND. 5¿ (polioxietilenoglicol-4-dilauril ester) PEG8L (polioxietilenoglicol-8-luril ester), PEG4DL (polioxietilenoglicol-8-dilauril ester), como componentes elásticos. As propriedades magnéticas foram adicionadas aos lipossomas através da incorporação da magnetita coloidal. A incorporação dos tensoativos nos lipossomos foi feita por dois procedimentos: durante a hidratação do filme lipídico ou por incubação com lipossomas pré-formados. Os lipossomas elásticos foram caracterizados através da quantificação do teor de fosfolipídios, diâmetro médio e distribuição de tamanhos, incorporação dos tensoativos, capacidade de permeação em membranas artificiais com poros de 50 e 30nm, elasticidade e estabilidade física de estocagem. Nos lipossomas elástico-magnéticos foi também caracterizada a incorporação da magnetita coloidal. Os resultados experimentais mostraram que a temperatura de transição de fases do fosfolipídio, a fluidez da bicamada lipídica produzida pela incorporação do tensoativo e a preservação da integridade da partícula foram fatores que determinaram o desempenho dos lipossomas elásticos na permeação através de membranas nanoporosas... Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: The purpose of this work was to study the preparation and characterization of elastic and elastic-magnetic liposomes designed to facilitate the transdermal transport of drugs. The prepared liposomes were unilamellar, composed by synthetic dymirystoylphosphatidylcholine (DMPC), hydrogenated soy phosphatidylcholine or egg phosphatidylcholine (PCegg) as structural components and by the derivative lauric acid surfactants: 'C IND. 12¿¿E IND. 5¿(polyoxyethylene-5-lauryl ether), PEG4L (polyethyleneglycol-4-lauryl ester), PEG4DL (polyethylenoglycol-4 dilauryl ester), PEG8L (polyethyleneglycol-8-lauryl ester) e PEG8DL polyethyleneglycol-8- dilauryl ester) as elastic components. Magnetic properties were added to elastic liposomes by incorporation of colloidal magnetite. The incorporation of surfactants to liposomes was done by two procedures: during hydration of lipid film or by incubation with preformed liposomes. The elastic liposomes were characterized through their phospholipid contents, mean diameter and size distribution, incorporation of surfactants, capability for permeation through artificial membranes containing 50 or 30 nm porous, elasticity and storage stability. The incorporation of colloidal magnetite was also characterized in elastic-magnetic liposomes. The experimental results show that the phospholipid phase transition temperature, the fluidity of the lipid bilayer generated by surfactant incorporation and the preservation of particle integrity were factors determining the performance of elastic liposomes on permeation through nanoporous membranes. In this context, DMPC and PCegg phospholipids and the surfactants PEG8L and PEG8DL were the best compounds... Note: The complete abstract is available with the full electronic digital thesis or dissertations / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química

Orientador: Eneida de Paula / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-11T08:33:29Z (GMT). No. of bitstreams: 1 Cunha_ElizabethSousada_M.pdf: 3228323 bytes, checksum: 545a2be4ec32cc1a223c4b4337dc369a (MD5) Previous issue date: 2008 / Resumo: A mitocôndria é uma organela vital, pois em células aeróbicas, ela é responsável pela produção da maior parte da energia química necessária para a célula. A síntese de ATP ocorre por fosforilação oxidativa na Fo,F1-ATPase, usando a energia gerada pela cadeia de transporte de elétr ons, uma série de enzimas presentes na membrana mitocondrial interna. A análise de proteínas de membrana pode ser feita pela técnica de eletroforese, tanto em condições nativas quanto desnaturantes. Neste trabalho analisamos a solubilização de proteínas da membrana interna de mitocôndria de músculo de rato, através do uso de surfatantes zwiteriônicos (ASB-14, ASB-16, CHAPS), não-iônicos (Digitonina, C12E8, Triton X- 100) e aniônico (Colato de sódio) na separação por eletroforese em gel nativo e bidimensional. Desenvolvemos um novo protocolo para preparo de eletroforese em gel nativo, mantendo o tampão de amostra descrito no procedimento de BN-PAGE e adaptando as demais etapas da técnica de acordo com o protocolo de Laemmli et al (1970). Os géis assim preparados em temperatura ambiente mostraram melhor resolução que os pelo método BN-PAGE, foram obtidos menor tempo de corrida (1- 2 horas), sem troca de tampões e com emprego de reagentes de menor custo. Quanto a eficiência dos diferentes surfatantes, usados em uma mesma concentração (43,2 mM), o zwiteriônico ASB-16 foi o melhor solubilizador das proteínas de MMI, tanto em relação a quantidade total de proteína solubilizada como em relação a número de ¿spots¿ visualizados na eletroforese bidimensional, seguido pelo não-iônico Triton X-100. O surfatante não-iônico dodecil maltosídeo foi usado na preparações dos géis 2D em concentrações menores inferiores (20%) do que as indicadas na literatura (10% ou 195,8 mM), sem prejuízo da eficiência de solubilização protéica. Os resultados obtidos com géis nativos mostraram que todos os surfatantes estudados podem ser usados para separar os complexos protéicos da MMI, mas apresentam seletividade específica pelos complexos da Cadeia Respiratória, devendo esse parâmetro ser melhor estudado futuramente, para a determinação de protocolos específicos para isolamento dos diferentes tipos de complexos / Abstract: The majority of the chemical energy produced inside aerobic cells is a result of the oxidative phosphorylation of ATP, inside the mitochondria. A great part of mitochondria proteins are organized into complexes located in the inner mitochondria membrane. Isolation and identification of those proteins have been conducted by electrophoresis, both in native as in denaturant condition. In this work we analysed solubilization of the inner mitochondrial membrane proteins of rat¿s gastrocnemius muscles, through the use of zwitterionic (ASB-14, ASB-16, CHAPS), non-ionic (Digitonin, C12E8, Triton X-100) and anionic (sodium cholate), by native and two-dimensional electrophoresis. We have developed a new protocol for the native gel electrophoresis, using the buffer sample described in BN-PAGE but changing other steps of the technique according to the protocol of Laemmli et al (1970). With this novel protocol, the gels prepared at ambient temperature had a better resolution than the classic BNPAGE technique; with low costs and short-time runs (1-2 hours). As for the effectiveness of surfactants studied to solubilize inner mitochondrial membrane proteins, when used at the same concentration (43.2 mM), the zwitterionic ASB-16 was the best, both accordingly to the total amount of solubilized protein, as for the number of "spots" detected in the two-dimensional electrophoresis, followed by non-ionic Triton X-100. The non-ionic surfactant dodecyl maltoside was used in the 2D electophoresys preparation at lower concentrations (20%) than that recommended in the literature (10% or 195.8 mM) without prejudice in the efficiency of protein solubilization. The results with native gels proved that all the studied surfactants can be used to separate the proteins of MMI, but with different selectivity for each enzymatic complex. This specificity should be better studied in the future, looking for the determination of specific protocols for better isolation of each types of MMI complex / Mestrado / Bioquimica / Mestre em Biologia Funcional e Molecular

Nitrogen-alloyed austenitic stainless steels are becoming increasingly popular, mainly due to their excellent combination of strength and toughness. Nitrogen desorption to the atmosphere during the autogenous welding of these steels is often a major problem, resulting in porosity and nitrogen losses from the weld. In order to counteract this problem, the addition of nitrogen to the shielding gas has been proposed. This study deals with the absorption and desorption of nitrogen during the autogenous arc welding of a number of experimental stainless steels. These steels are similar in composition to type 310 stainless steel, but with varying levels of nitrogen and sulphur. The project investigated the influence of the base metal nitrogen content, the nitrogen partial pressure in the shielding gas and the weld surface active element concentration on the nitrogen content of autogenous welds. The results confirm that Sievert's law is not obeyed during welding. The weld nitrogen content increases with an increase in the shielding gas nitrogen content at low nitrogen partial pressures, but at higher partial pressures a dynamic equilibrium is created where the amount of nitrogen absorbed by the weld metal is balanced by the amount of nitrogen evolved from the weld pool. In alloys with low sulphur contents, this steady-state nitrogen content is not influenced to any significant extent by the base metal nitrogen content, but in high sulphur alloys, an increase in the initial nitrogen concentration results in higher weld nitrogen contents over the entire range of nitrogen partial pressures evaluated. A kinetic model can be used to describe nitrogen absorption and desorption during welding. The nitrogen desorption rate constant decreases with an increase in the sulphur concentration. This is consistent with a site blockage model, where surface active elements occupy a fraction of the available surface sites. The absorption rate constant is, however, not a strong function of the surface active element concentration. Alloys with higher base metal nitrogen contents require increased levels of supersaturation prior to the onset of nitrogen evolution as bubbles. These increased levels of supersaturation for the higher-nitrogen alloys is probably related to the higher rate of nitrogen removal as N2 the onset of bubble formation. Given that nitrogen bubble formation and detachment require nucleation and growth, it is assumed that a higher nitrogen removal rate would require a higher degree of supersaturation. Nitrogen losses from nitrogen-alloyed stainless steels can be expected during welding in pure argon shielding gas. Small amounts of nitrogen can be added to the shielding gas to counteract this effect, but this should be done with care to avoid bubble formation. Supersaturation before bubble formation does, however, extend the range of shielding gas compositions which can be used. Due to the lower desorption rates associated with higher surface active element concentrations, these elements have a beneficial influence during the welding of high nitrogen stainless steels. Although higher sulphur contents may not be viable in practice, small amounts of oxygen added to the shielding gas during welding will have a similar effect. / Dissertation (PHD)--University of Pretoria, 2004. / Materials Science and Metallurgical Engineering / unrestricted

This work was performed in the framework of an interdisciplinary graduate program that focuses on the establishment and extension of innovative compounds for the packaging of electronic systems. Such chemically or biotechnologically tailored compounds can be used for the direct patterning of optically, magnetically or biologically functional structures in nano- and biotechnical products. In order to organize matter at the nanometer scale, imprinting litho-graphy techniques or self-organization processes are appropriate. Fine-tuning of numerous engineering processes requires continuous and high precision monitoring as well as control of diverse parameters. These demands are only partially met by physical or chemical components since they use surrogate parameters, measure off-line, or provide insufficient performances. Biological compounds, in particular protein-based feedback systems, fulfill certain system requirements to a considerable degree. Hydrophobins and S-layer proteins are surface active proteins, produced by filamentous fungi or bacteria. In nature, these (self )assembly proteins form highly ordered and robust structures. In addition, their tolerance for different sequence manipulations and chemical modifications allows extensive functionalization of these nanometer-sized proteins. Hence, these surface active proteins can also be fused with other protein domains to create chimera, which retain function of both original proteins. In conclusion, both hydrophobins and S-layer proteins represent a versatile tool in numerous fields of applied biotechnology, medicine or diagnostics. But until now, efficient in vitro operation in molecular designed protein coatings is strongly restricted due to their complex assembly mechanism. In the first phase of this work, it was demonstrated, that representatives of class I and class II hydrophobins tend to form multilayered structures on solid surfaces. It was found that only two protein orientations seems to be preferentially formed. In the process of assembly, the orientation of the first hydrophobin layer strictly depends on the substrate wettability. Consequently, each of the following hydrophobin layers is inverse oriented to the layer before. This alternating assembly mechanism has to be taken into account, when working with functionalized hydrophobins, because a hydrophobin-fused functional protein domain is exclusively located on one side of the protein. Due to the densely packed structure of surface active proteins, a fused functional domain, embedded between two hydrophobins is barely available for external reagents. Basically, the simultaneous existence of a broad spectrum of ordered and disordered assembly structures, demonstrated the need of an uniform protein film assembly for applications in fine-diagnostics or biomedicine. With regard to molecular designed protein coatings, this work further aimed at establishing conditions to develop a method for a ‘layer-by-layer’ assembly of protein chimeras. Based on their amphiphilic character, self-assembly behavior of surface active proteins can be influenced by conventional ionic surfactants. In order to study the effect of surfactants on the composition and morphology of adsorbed protein films, contact angle measurements, nulling ellipsometry, SEM, AFM and AFAM were performed. It was found that the layer thickness of assembled protein films is strictly dependent on the amount of added surfactant. At certain threshold surfactant concentrations, hydrophobins and S-layer proteins assemble in uniform layers, which are as thick as expected for a protein monolayer or a bilayer. Assembled protein films are covered by a smooth surfactant layer, which prevents further protein assembly. AFAM measurements reveal the formation of well defined lattice structures under the coverage of surfactants. Even the removal of the surfactant layer is possible without inter-fering with protein specific secondary structures. Solvent accessibility and functionality of protein-fused domains was successfully demonstrated. As compared to conventional assembly techniques, this novel protein deposition method offers a possibility for a ‘directed’ protein coating on solid surfaces. In addition, it guarantees broadly ranged homogeneous assembly of protein chimeras on non-planar or even porous surfaces independent of their position. Finally, a prototype for an interfacial FRET was developed in a close collaboration with the Institute of Physical Chemistry (TUD). This innovative FRET between semiconducting nano-particles and illuminating protein chimeras takes place across an oil/water interface. Hydro-phobins were used to stabilize artificial oil droplets in aqueous solution. These small proteins possess the ability to attach fused functional domains very close to an oil/water interface. When, in addition to this, an optically active nanostructure directly docks to the hydrophobin, the distance of a protein-fused domain and the nanostructure are in the range of the FÖRSTER radius. It was successfully demonstrated that quantum dots and fluorescent proteins fulfill the spectroscopic requirements of such a donor/acceptor pair. The FRET performance of these excitable oil droplets was examined as a ‘proof of concept’. Due to its modular design, this signal amplification setup could be exploited in numerous fields of technical application ranging from quantification of micronutrient to photothermal cancer therapy.

M.Cur. (Intensive General Nursing) / The purpose of this study is to identify nursing guide-lines for the nursing of babies that received exogenous surfactant. In view of the fact that the exogenous surfactant therapy is still a very new therapeutic approach for the treatment of hyaline membrane disease there is still a lot to learn about the complications of the treatment. The professional nurse monitors the baby after medication was given, and it is therefore necessary to set out nursing guidelines to guide her in her treatment of the baby. Ten case-studies were done on 10 babies that have already been submitted to the therapy. They were selected from Provincial hospitals in the Johannesburg region. Recurrent events/incidents were identified and used as data from which nursing guide-lines were compiled. A literature study was done to consult other authors' findings on this topic. Recommendations were made at the end of the study concerning applications to practise, education and further research needed.

In industry the effective mixing and de-agglomeration of two solid particles is vital in applications that require the intimate contact of homogeneously mixed reagents. One such application is in the preparation of pyrotechnic delay elements with reproducible burn speeds. The concept of surfactant assisted particle micro-mixing is proposed. This theory is based in the use of two amphiphilic polymeric surfactants to form two separate stable dispersions of the two solid particles to be mixed, but with the subsequent requirement that the dispersants are able to interact with each other. The formation of the individual dispersions allows for the deagglomeration of the particles and thus their preparation for homogeneous mixing, which is facilitated by the interacting surfactants. Low molecular mass block copolymers of styrene and acrylic acid and poly( ethylene oxide)-poly(propylene oxide) (PEO-PPO) surfactants are the proposed dispersants which will allow for the surfactant interaction by means of hydrogen bonding between the poly(acrylic acid) block and the PEO. The poly(styrene-co-acrylic acid) block copolymer will be synthesised via Atom Transfer Radical Polymerisation (ATRP) and subsequently used in the dispersion experiments. The synthesis of the polystyrene macroinitiators to initiate the block copolymerisation of the t-butyl acrylate was carried out satisfactorily, with good molecular masses and molecular mass distributions. In addition, lH-NMR analysis carried out on the polystyrene macroinitiators confirmed their synthesis. The use of the polystyrene macroinitiators was successful in synthesising poly(styrene-co-t-butyl acrylate) block copolymers with slightly higher polydispersities in comparison to the macroinitiatiators themselves, but acceptable. Hydrolysis of the poly(styrene-co-t-butyl acrylate) block copolymer to poly(styrene-co-acrylic acid) was successful in the presence of trifluoroacetic acid as catalyst. Attempts to hydrolyse in basic conditions (NaOH) and alternatively in acidic conditions (HCI) were not successful. Use of the poly(styrene-co-acrylic acid) amphiphilic block copolymer to emulsion polymerise styrene requires the ionised form of the polymer and was therefore not favourable to observe surfactant-surfactant hydrogen bonding. In addition, attempts to synthesise a wax emulsion stabilised by a PEO containing surfactant proved to be unsuccessful. Subsequently, the micro-mixing experiments were carried out by using a poly(acrylic acid) stabilised melamine dispersion and a commercially available PEO containing surfactant stabilised wax emulsion. The interaction between the melamine and the poly(acrylic acid) allows for the formation of a stable melamine dispersion at above 7% poly(acrylic acid) : melamine ratio (mass basis). Analysis by SEM shows that without the poly( acrylic acid) dispersant no wax particles are found to occur on the melamine particle surface. However, in an attempt to determine whether the amount of wax interaction increases with poly(acrylic acid) content, it was found that in the absence of poly(acrylic acid) dispersant, the most amount of wax precipitated out with the melamine. This is possibly attributable to the preferential occlusion of the wax particles between the melamine particles rather than surface attachment. Introduction of the poly(acrylic acid), however, shows via SEM analysis that the hydrogen bond interaction between the acrylic acid group and the ethylene oxide group does occur, since the attachment of the wax particles on the melamine particle surface is observed. Although results show that the surfactant-surfactant interaction allows for the micro¬mixing of particles, some refinement is required with respect to the systems that this phenomenon can be applied to. In addition, factors such as particle type, particle size and surfactant type will influence the micro-mixing interaction. It is therefore recommended that these factors be investigated in order to completely identify the micro-mixing phenomenon. / Dissertation (M Eng (Chemical Engineering))--University of Pretoria, 2006. / Chemical Engineering / unrestricted