Conventional Ag/AgX electrodes, responsive to halide X, cannot be used to monitor the addition of a second halide Y since such additions result in a slow chemical conversion of the macroscopic halide coating AgX to AgY. This is a serious problem in the manufacture of photographic emulsions that frequently contain more than one silver halide. The thesis describes a new electrochemical measurement technique with the ability to make appropriate determinations in solutions of mixed halides. In the new technique (termed "clean/coat/measure"), silver electrodes were prepared "in situ" by applying square wave pulses to the electrode. First the previous halide layer was removed, then the electrode was coated in situ with a new layer of silver halide and this was used to measure the open circuit potential before the cycle was repeated. In this way the halide coating reflected the composition of the measurement solution. Existing commercial instrumentation was inappropriate for the proposed measurement sequence. Thus, a range of instrument hardware and software was designed and built by the author and used to study the influences of a multitude of parameters on the measurement performance. 1. A stable and accurate measurement system was designed and fabricated allowing the potentials of eight electrodes to be measured simultaneously in grounded solutions. Data was collected and stored on a PC using custom written software. Calibration curves for conventional silver/silver chloride, bromide and iodide electrodes were obtained over a range of concentrations and temperatures. Silver/silver halides electrodes with small surface areas (< 9 mm2) and thin halide coatings (< 1 nm thick) were studied to ensure that such electrodes performed as conventional large, thickly coated electrodes. Calibration curves showed no deterioration of response due to small surface areas and, over short time scales (< 2 min), no deterioration due to thin layers. 2. A laboratory instrument was designed and built to apply potential pulses, control a rotating disc electrode (RDE) and collect data. The system allowed both controlled potential pulses to be applied to the electrodes and open circuit potentiometric measurements to be made. Measurements of potential and current were collected at a rate of 10,000 measurements per second. The system used custom software running on a PC to control the instrumentation and to store data on the PC. Using this instrumentation a RDE was used to study the new "clean/coat/measure" pulsed technique. Results from the RDE study indicated that an electrode capable of sensing halide could be produced by this technique if an applied potential pulse with sufficient charge was applied. This minimum charge (11 x w-s C cm-2) produced a coating thickness approximately equivalent to a monolayer. The study also indicated that the technique was independent of the speed of rotation of the silver electrode and was successful over a wide range of conditions of pulse time, applied potential and cycle times for solution of potassium bromide in the range 0.001 to 0.05 M. The technique also successfully measured the addition of potassium iodide to a solution of potassium bromide while conventional thickly coated electrodes did not. 3. Two further instrumentation systems were designed and built to be used in a grounded stainless steel emulsion making vessel , one to apply controlled potential pulses and one to apply constant current pulses. Using these instruments and the conditions found for the RDE, static cylindrical electrodes in stirred solutions were investigated using both controlled potential and constant current square wave pulses of between 50 and 500 ms. Both potential step and current step techniques successfully measured the halide concentration of solutions of potassium chloride and bromide (0.001 to 0.5 M) and potassium iodide (0.0001 to 0.5 M). Both methods were also shown to be able to successfully monitor the addition of iodide to bromide and chloride solutions. With respect to future work, modifications to the instrumentation are proposed, including the replacement of the PC by an on-board microprocessor, the design of a multi-channel system and use of intelligent software to determine the optimum potential or current to apply. Areas of work required to be carried out before the system could be used in a production environment are given.

Abstract Moisture content control is a very effective way of protecting timber. Treatments with environment-friendly, biodegradable tall oil are known to reduce the capillary water uptake of pine sapwood greatly, but despite the good results achieved there have been two problems that limit the use of tall oil for wood protection, the large amount of oil needed and the tendency for the oil to exude from the wood. This work was undertaken in order to obtain an understanding of the mechanism of wood protection by means of crude tall oil (CTO) and to find technical solutions to the main problems limiting its use for industrial wood protection. It is shown that the emulsion technique is one way of solving the first problem, as it provides high water-repellent efficiency at considerably lower oil retention levels. The fact that water is used as a thinner in this technique instead of the commonly used organic solvents is beneficial from environmental, economic and safety points of view. It is also shown that although the drying properties of CTO are inadequate for use as such in wood preservation, its oxidation and polymerization can be accelerated considerably by means of iron catalysts, which prevent the oil from exuding out of the wood. This also increases the water repellent efficiency of CTO treatment. Most impregnation oils do not dry when applied in large quantities, because they hinder the diffusion of air through the wood, which supplies the necessary oxygen. Limiting of the oil uptake by the means of the emulsion technique disturbs the airflow to a lesser extent, and thus enhances the drying process. Hence, both the emulsion technique and the use of an iron catalyst improve both the water-repellent efficiency of tall oil treatment and the rate of drying of the oil, thus solving the two main problems related to wood impregnation with tall oil in one single-stage treatment which can be used in existing wood preservation plants. This is advantageous from both an industrial and an economic point of view.

Les émulsions sont très utilisées dans le domaine des cosmétiques, notamment pour les crèmes et les lotions. En fonction de leur composition, elles présentent diverses propriétés en matière de stabilité, de texture, de microstructure et de macrostructure. Il n’existe pas, à l’heure actuelle, d’étude dans la littérature qui se soit intéressée à l’effet de la composition sur ces différentes propriétés et aux relations qui peuvent exister entre celles-ci, tout en mettant en œuvre une maîtrise de la formulation. Pour répondre à cette double problématique, quatorze émulsions huile-dans-eau ont été formulées, avec un protocole maîtrisé, pour lesquelles les concentrations en phase grasse, en gomme acacia et en xanthane varient. Des solutions de xanthane et de gomme acacia ont également été préparées pour comparer l’effet des gommes en émulsion et en phase aqueuse seule. Les produits ont été ensuite caractérisés, de façon la plus complète et objective possible, pour mettre en évidence l’influence de la composition sur les propriétés de l’émulsion et leurs interactions. De nombreux paramètres ont ainsi été collectés par : analyse sensorielle, des observations microscopiques et des mesures en granulométrie laser, des mesures rhéologiques et mécaniques. On peut en conclure que chacun des paramètres de l’émulsion impacte ses propriétés, avec des différences notables, la teneur en phase grasse étant, globalement, prépondérante. Des relations entre l’ensemble des données ont été mises en évidence et permettent de proposer des hypothèses quant à l’impact de la formulation sur les propriétés tactiles des crèmes cosmétiques. / Emulsions are widely used in cosmetics. Depending on their composition, they exhibit various properties in terms of stability, texture, microstructure and macrostructure. At the present time, there a few to no studies in the literature interested in the effect of the emulsions composition on these different properties and the existing link between these characteristics that are implementing a command of the formulation. To address this dual problem, fourteen oil-in-water emulsions were formulated, with a controlled formulation protocol, for which the concentration of oil phase, acacia gum and xanthan gum evolve. Solutions of xanthan and acacia gums were also prepared to compare the effect of the gums on emulsions to the one on aqueous phase alone. The products were then characterized, in the most complete and objective way possible, to illustrate the influence of the composition on the properties of the emulsions and how these interact. Numerous parameters were collected through : ensory analysis, mcroscopic observations and static light scattering measurements, rhlogical and instrumental texture analyses. t can be concluded that the emulsions are well differentiates and that each of the emulsion parameter impacts its properties with significant differences, the oil phase content being preponderant overall. elationships between the data set were highlighted and suggest hypotheses about the impact of the formulation on the tactile properties of cosmetic creams.

L’encapsulation est une technique employée couramment par le milieu industriel, notamment dans le domaine du médical, de la parfumerie ou de la cosmétique. Afin de répondre aux attentes et de proposer des capsules modulables pour tous types d’applications, des capsules de type coeur-écorce ont été élaborées au cours de cette thèse. Elles sont obtenues à partir d’émulsion dont le coeur huileux est enrobé par une coque de silice, via la minéralisation de l’interface eau-huile. Les émulsions de Pickering, stabilisées par des particules colloïdales, sont particulièrement stables et intéressantes pour cette étude. Le but de cette thèse est de comprendre, dans un premier temps, les mécanismes fondamentaux impliqués dans le processus de fabrication. Cela a permis d’élaborer, par la suite, des matériaux hybrides complexes à différentes échelles, du micrométrique au nanométrique,mais également d’établir les mécanismes de libération par un stimulus externe. Enfin, une encapsulation maîtrisée permet d’allier stabilité au stockage et destruction rapide ou contrôlée à l’utilisation. Ainsi, par diverses méthodes définies dès la formulation de l’émulsion initiale, le contenu huileux des capsules peut être libéré de manière provoquée par une action mécanique ou par l’augmentation de la température (macroscopique ou local par hyperthermie magnétique). / Encapsulation is a technique used in the industry, in particular in the field of medical,perfumery or cosmetics. In order to meet the expectations and propose adaptable capsules for all types of applications, core-shell capsules type were developed during this thesis.There were based on emulsions science with an oily core coated by a silica shell,synthetized by sol-gel chemistry at the oil-water interface. Pickering emulsions, which are emulsions stabilized by colloidal particles, are particularly stable and interesting for this study. The aim of this thesis is to understand, at first, the fundamental mechanisms involved in the manufacturing process. This made it possible to develop complex hybrid materials at different scales, from micrometric to nanometric, but also to establish the releasing mechanisms by an external stimulus. Thanks to a controlled encapsulation, it is possible to combine stability (storage) and rapid or controlled destruction when used. Thus, by various method, defined from the formulation of the initial emulsion, the releasing of the oily contentcan be caused by mechanical action or by an temperature increased (macroscopically orlocally by magnetic hyperthermia).

The aims of this thesis were two-fold: A) To use high internal phase emulsion (HIPE) templated materials to produce a chromatographic stationary phase for the size separation of engendered nanoparticles (NPs). B) To produce well characterised lanthanide doped polymer NPs with a potential use as analytical standards. Initially, silica materials were prepared from oil-in-water HIPEs by a two stage acid/base catalysed sol gel process. As well as presenting the expected macroporosity typical of HIPE templated materials, it was also found that micro- and meso-porosity could be influenced by surfactant choice and reaction with iron (III) chloride or copper (I) chloride which had been included in the HIPE. However, the resulting silica materials were deemed inappropriate for the desired chromatography. Monolithic columns were prepared from HIPE templated polymers (polyHIPEs) and incorporated into a HPLC system. Poly(styrene-co-divinylbenzene) and poly(ethylene glycol dimethacrylate) polyHIPE columns were able to separate sub-micron polystyrene latexes, detected by UV absorption, and dysprosium doped polystyrene latex particles and gold nanoparticles detected by inductively coupled plasma mass spectrometry (ICP-MS).Dysprosium, gadolinium and neodymium doped polystyrene NPs were prepared by micro-emulsion polymerisation. Particle size was controlled (over a 40 – 160 nm range) by tailoring of surfactant and initiator concentrations. Particles were characterised by dynamic light scattering, differential centrifugal sedimentation, transition electron microscopy and hydrodynamic chromatography (HDC)-ICP-MS. Also, particle surface change, lanthanide content and solids content were analysed. The latter two appear related to particle size. As far as the author is aware there are no cases of the use of polyHIPE columns size separation in the literature. Nor are there any cases of encapsulation of metals within polymer nanoparticles by micro-emulsion polymerisation reported.

This study (Wassell & Young 2007; Wassell et al., 2010a) shows that behenic (C22:0) fatty acid rich Monoacylglycerol (MAG), or its significant inclusion, has a pronounced effect on crystallisation (Wassell et al., 2010b; 2012; Young et al., 2008) and interfacial kinetics (3.0; 4.0). New interfacial measurements demonstrate an unusual surface-interactive relationship of long chain MAG compositions, with and without Polyglycerol Polyricinoleate (PGPR). A novel MAG synthesised from Moringa oleifera Triacylglycerol (TAG) influenced textural behaviour of water-in-oil (W/O) emulsions and anhydrous TAG systems (4.0: 5.0; 6.0). Emulsifier mixtures of PGPR and MAG rich in C18:1 / 18:2 and C16:0 / C18:0 do not decrease interfacial tension compared with PGPR alone. Only those containing MAG with significant proportion of C22:0 impacted interfacial behaviour. A mixture of C22:0 based MAG and PGPR results with decreasing tension from ~20°C and is initially dominated by PGPR, then through rearrangement, the surface is rapidly dominated by C22:0 fatty acids. A Moringa oleifera based MAG showed unusual decreased interfacial behaviour not dissimilar to PGPR. All other tested MAG (excluding a C22:0 based MAG), irrespective of fatty acid composition resulted with high interfacial tension values across the measured temperature spectrum (50°C to 5°C). A relative decrease of interfacial tension, with decreased temperature, was greater, the longer the chain length (Krog & Larsson 1992). Moreover, results from bulk and interfacial rheology showed that the presence of C22:0 based MAG has a pronounced effect on both elastic modulus (G’) and viscous modulus (G’’). Through a multidisciplinary approach, results were verified in relevant product applications. By means of ultrasonic velocity profiling with pressure difference (UVP-PD) technique, it was possible to examine the effect of a C22:0 based MAG in an anhydrous TAG system whilst in a dynamic non-isothermal condition (3.0). The non-invasive UVP-PD technique conclusively validated structural events. The application of a Moringa oleifera based MAG in low TAG (35% - 41%), W/O emulsions, results in high emulsion stability without a co-surfactant (PGPR). The bi-functional behaviour of Moringa oleifera based MAG is probably attributed to miscibility (Ueno et al., 1994) of its fatty acids, ranging ~30% of saturated fatty acids (SAFA), with ~70% of C18:1 (5.0). It is concluded that the surface-interactive behaviour of Moringa oleifera based MAG, is attributed to approximately 10% of its SAFA commencing from C20:0. When examined separately and compared, results showed that physical effect of a Moringa oleifera based MAG was not dissimilar to PGPR, influencing the crystallisation kinetics of the particular anhydrous TAG system. When either was combined with a C22:0 rich MAG, enhanced gelation onset and strong propensity to form dendrite structure occurred (5.0). Macrobeam and synchrotron radiation microbeam small angle x-ray diffraction (SR-μ-SAXD) was utilized (6.0) to assess behavior of C22:0 rich MAG, with and without PGPR (Wassell et al., 2012). The C22:0 based MAG combined with PGPR promoted TAG crystallisation as observed by differential scanning calorimetry (DSC). Polarised optical microscopy (POM) observations indicated that C22:0 based MAG eliminates formation of large crystal aggregates, resulting in the likely formation of tiny Pickering TAG / MAG crystals (6.0). It is concluded that the presence and interactive behaviour of Pickering surface-active MAG, is strongly linked to increased fatty acid chain length, which induce increased textural resilience owing to viscoelasticity (4.0; 5.0). A multidisciplinary approach was able to verify structuring behaviour (4.0; 5.0), using multiple analyses (Wassell et al., 2010b; 2012; Young et al., 2008). Novel structuring solutions in reduced TAG based systems have been provided (4.0; 5.0). This study both enhances current understanding of structuring in low TAG W/O emulsions and has led to novel MAG compositions, which address emulsification, structuring and texture in TAG based food systems (Wassell et al., 2010a; 2012a; 2012b; 2012c; 2012d; 2012e; Bech et al., 2013).

No description available.

Herein two novel synthetic strategies for the synthesis of sub-millimetre sized core–shell particles comprising a polyelectrolyte core and a porous hydrophobic shell are presented. In the first method, a water-in-oil-in-water (W/O/W) double-emulsion was used as a template for the simultaneous polymerisation of both the internal aqueous and the intermediate oil phases, via suspension polymerisation, leading to the formation of a cross-linked poly(acrylic acid-co-bisacrylamide) core contained in a porous poly(4-tert-butylstyrene-co-divinylbenzene) shell. It was found that the formation of core–shell morphology was favoured by the effect of acrylic acid which was responsible for the selective destabilization of the internal aqueous/oil (W/O) interface. It was found that rapid internal phase coarsening promoted the formation of single-core structures. A rapid gel-point of the oil phase, on the other hand, reduced the internal aqueous phase diffusion towards the external phase. The detrimental effect over internal emulsion stability was replicated using ethanol, 2-propanol, n-butanol and propionic acid which were used as a co-solvent in the internal aqueous phase to promote core/shell morphology formation. The second method involved the use of a flow-focusing device for the formation of monodisperse W/O/W emulsion droplets which were photo-polymerised. Anionic poly(sodium acrylate), poly(sodium vinyl sulfonate), and cationic poly(3-acrylamidopropyl)trimethylammonium chloride) hydrogels were encapsulated within a porous poly(trimethylolpropane triacrylate-co-methyl methacrylate) shell. Control over both particle diameter and shell thickness was achieved by tuning the flow rates of the different phases. The use of these novel hydrogel core/shell particles as novel material for environmental applications, including the scavenging of radionuclides, was investigated. It was found that hydrophilic substances including dyes and metal ions were rapidly adsorbed and encapsulated within the core region after diffusing through the permeable porous shell. Part of the results obtained in this work have been published in the article J. Mater. Chem. A, 2013, 1, 12553-12559.

M.Sc. / Emulsions are not widely used in industry for wear-metal-in-oil determinations and this study was undertaken in order to evaluate such a possibility. The use of emulsified standards was compared to aqueous standards for the calibration of an emulsified used lubricating oil sample. The traditionally used methods of ashing in a muffle furnace and dilution with the organic solvent, xylene were also evaluated in comparison with the emulsion methodology. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the wear-metal-in-oil analysis. The performance characteristics of each method were compared for the following metals: AI, Cr, Cu, Fe, Ni, and Pb. The used oil sample and emulsified standards were acid treated and emulsified in water {1% wlw) using tetralin as solvent and triton X-100 as surfactant. This evaluation included the calibration characteristics, precision and accuracy obtained, as well as the results of recovery studies. The emulsification method was found to be comparable to the ashing and dilution methods in terms of calibration and only Cr, Cu, Fe and Pb concentrations were found. The precision of the emulsification method was found, in general, to be close to or less than 2% RSD. The used oil matrix also contained leaked petroleum from a problem car engine. An accurate determination of lead was consequently impossible since the high lead content led to sedimentation. The use of the internal standard, indium, was evaluated for its effectiveness in correcting possible matrix effects that were evident from the results obtained in the recovery studies. The recovery studies showed the Cr and Pb determinations to be adversely affected by internal standardization. An alternative approach for matrix effect correction, the common analyte internal standardization (CAIS) method was also investigated. This method held promise for allowing the use of aqueous standards, instead of oil or emulsion standards, for the calibration of the emulsified oil samples. Three different applications of the CAIS technique were investigated and all proved unsuccessful.

Orientador: Rosiane Lopes da Cunha / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-27T01:07:13Z (GMT). No. of bitstreams: 1 Costa_AnaLeticiaRodrigues_M.pdf: 3081485 bytes, checksum: 44ad03cd2e14d1ef00c3251b254983eb (MD5) Previous issue date: 2015 / Resumo: A técnica de emulsificação em dispositivos de microfluídica é utilizada para a produção de gotas de diâmetro reduzido e distribuição de tamanho monodispersa. A gelificação da fase dispersa de emulsões água em óleo pode levar à formação de microgéis com elevado potencial para encapsulação de compostos ativos. Do ponto de vista tecnológico, a utilização de partículas de tamanho reduzido permite entrega mais fácil e liberação do bioativo de forma mais eficiente no local alvo. Este trabalho teve como objetivo estudar o processo de formação de microgéis de goma gelana em dispositivos de microfluídica utilizando a técnica de focalização hidrodinâmica. Foram avaliadas as concentrações da goma gelana de 0,5 a 0,7% (m/m) e do agente gelificante acetato de cálcio nas concentrações de 0,5 e 2,0% (m/m) para formação dos microgéis. Na primeira etapa, emulsões simples água em óleo, sendo a fase dispersa constituída de água ou dispersões aquosas de goma gelana e fase contínua constituída por uma mistura composta por óleo de soja e o emulsificante polirricinoleato de poliglicerol (PGPR), foram avaliadas quanto ao regime de formação de gotas em diferentes vazões das fases e razões entre as vazões das fases dispersa e contínua. Também foram determinadas as velocidades reais das fases dentro dos dispositivos de microfluídica e os números adimensionais de Reynolds, Capilar e Weber que descrevem o escoamento dos fluidos no microcanais. Com o controle da condição de processo, vazão de entrada das fases dispersa e contínua, foi possível observar as variações no regime de formação de gotas, que variou desde o gotejamento até o jateamento. Em geral, todas as vazões calculadas (reais) das fases foram menores do que aquelas aplicadas na bomba, sendo este resultado relacionado às limitações das dimensões dos canais e alta viscosidade das fases. Desta forma, os números de Reynolds, Capilar e de Weber calculados a partir das velocidades reais das fases foram menores quando comparados com os valores obtidos usando as velocidades impostas na bomba. Na etapa seguinte, microgéis de goma gelana foram produzidos nos microcanais e caracterizados pela distribuição de tamanho de gotas e microscopia ótica. Os microgéis possuíam formato regular e esférico e distribuição de tamanho altamente monodispersa. O potencial da utilização de microgéis de goma gelana na encapsulação de compostos ativos foi avaliado adicionando o corante hidrofílico Rhodamina B na fase aquosa. As partículas obtidas na saída do dispositivo possuíam coloração vermelha, referente à boa retenção do corante hidrofílico. Desta forma, conclui-se que os microgéis obtidos pela técnica da microfluídica poderão ser utilizados na encapsulação de compostos hidrofílicos, inclusive aqueles sensíveis à temperatura, como as vitaminas e probióticos, na imobilização de proteínas e enzimas, bem como, na entrega de drogas, pois além de apresentarem baixa polidispersidade na distribuição de tamanho das partículas mostraram elevada capacidade de retenção do corante utilizado para simular o composto ativo de interesse / Abstract: Emulsification in microfluidic devices is used for the production of droplets with reduced diameter and monodisperse particle size distribution. Gelation of the disperse phase of water in oil emulsions leads to formation of microgels with high potential for the encapsulation of active compounds. Small particle size allows more efficient release of the bioactive at the target site. This work aimed to study the production of gellan microgel using microfluidic devices through flow- focusing technique. Gellan gum concentration of 0.6% (w/w) and calcium acetate (gelling agent) in concentrations of 0.5 and 2.0% (w/w) were used for the formation of microgels. In the first step, it was evaluated of the droplets formation regime at different flow rates of the phases and flow rate ratio of the dispersed and continuous phases of water-in-oil emulsions, composed by dispersed phase of water or gellan aqueous solutions and continuous phase constituted of a mixture composed of soybean oil and the emulsifier polyglycerol polyricinoleate (PGPR). The real velocity of the phases within the microfluidic devices and dimensionless numbers of Reynols, Capilar and Weber that describe the flow of fluids in microchannels were also evaluated. By controlling the process conditions and the input flow rate of dispersed and continuous phases, variations in the drop formation regime were observed which varied from dripping to the jetting regime, such variation exerted strong influence on droplet size. In general, the real flow rate (calculated values) was lower than those applied by pump, which was related with limitations of the size of channels and high viscosity of the phases. Reynolds, Capilar and Weber numbers calculated from the real velocity were smaller compared with the values obtained using the speed imposed by pump. In the next step, gellan microgels were produced the microchannel and characterized by droplet size distribution and optical microscopy. The microgels exhibit uniform and spherical shape and highly monodisperse distribution size. Potential use as gellan microgels as encapsulating matriz of active compounds was evaluated by adding the hidrophilic dye, Rhodamine B, in the aqueous phase. Results showed a low polydispersity and high hidrophilic compound retention capacity, indicating that microgels obtained by microfluidic technique may be used for the encapsulation of hydrophilic compounds that are sensitive to temperature, such as vitamins, probiotics and immobilization of proteins and enzymes, as well as in drug delivery / Mestrado / Engenharia de Alimentos / Mestra em Engenharia de Alimentos