Particle Nucleation is the forcing function in the Emulsion Polymerization processes and it plays an important role in dictating the final properties of the latex produced. Identification of the main nucleation sites and characterizing them in terms of their size and composition is important for elucidating the mechanism of particle nucleation. This research focuses on identifying the most likely nucleation locus in emulsion polymerization processes by characterizing the initial conditions of the reaction mixture. In order to achieve this objective, a methodology was devised, which used a non-reacting model emulsion system instead of the original emulsion. The model emulsion system selected has the same dispersion properties as that of the monomer emulsion system, but different optical properties. The model emulsion system enabled the study of the distribution of the emulsifier using Uv vis spectroscopy. This approach also eliminated the time constraint associated with sampling during a polymerization reaction. A quantitative deconvolution using the turbidity equation, was done on the transmission Uv vis spectra of the emulsions. This enabled the characterization of the emulsions in terms of their particle size distribution, particle number and the composition of the droplet populations comprising them. The studies conducted provide the experimental evidence for a previously unidentified nano-droplet population of size range 30 to 100nm in diameter. To further support this experimental evidence, calculations were performed to obtain the emulsifier distribution over the nano-droplet population. The calculations suggest the probability of existence of the nano-droplet population to be much higher than the probability of the existence of the swollen micelles. The results, depending upon the emulsification conditions, indicate the presence of about 15 % to 80% of the dispersed phase in the nano-droplet population. The large interfacial area offered by the nano-droplet population due to their high particle numbers and high percentage of the dispersed oil phase in them, make them the most probable particle nucleation loci in emulsion polymerization processes. Designed experiments were performed to experimentally observe the changes in the nano-droplet populations. The effects of the process variables, namely pH, surfactant concentration and temperature, on the size and compositional characteristics of the nano-droplet population were investigated. The results suggested that the surfactant to oil ratio was the dominating factor governing the size and the weight percent of the dispersed phase in the nano-droplet population.

Includes vita. / Title from PDF of title page. / Document formatted into pages; contains 224 pages. / Thesis (Ph.D.)--University of South Florida, 2004. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Particle Nucleation is the forcing function in the Emulsion Polymerization processes and it plays an important role in dictating the final properties of the latex produced. Identification of the main nucleation sites and characterizing them in terms of their size and composition is important for elucidating the mechanism of particle nucleation. This research focuses on identifying the most likely nucleation locus in emulsion polymerization processes by characterizing the initial conditions of the reaction mixture. In order to achieve this objective, a methodology was devised, which used a non-reacting model emulsion system instead of the original emulsion. The model emulsion system selected has the same dispersion properties as that of the monomer emulsion system, but different optical properties. The model emulsion system enabled the study of the distribution of the emulsifier using Uv vis spectroscopy. / ABSTRACT: This approach also eliminated the time constraint associated with sampling during a polymerization reaction. A quantitative deconvolution using the turbidity equation, was done on the transmission Uv vis spectra of the emulsions. This enabled the characterization of the emulsions in terms of their particle size distribution, particle number and the composition of the droplet populations comprising them. The studies conducted provide the experimental evidence for a previously unidentified nano-droplet population of size range 30 to 100nm in diameter. To further support this experimental evidence, calculations were performed to obtain the emulsifier distribution over the nano-droplet population. The calculations suggest the probability of existence of the nano-droplet population to be much higher than the probability of the existence of the swollen micelles. / ABSTRACT: The results, depending upon the emulsification conditions, indicate the presence of about 15 % to 80% of the dispersed phase in the nano-droplet population. The large interfacial area offered by the nano-droplet population due to their high particle numbers and high percentage of the dispersed oil phase in them, make them the most probable particle nucleation loci in emulsion polymerization processes. Designed experiments were performed to experimentally observe the changes in the nano-droplet populations. The effects of the process variables, namely pH, surfactant concentration and temperature, on the size and compositional characteristics of the nano-droplet population were investigated. The results suggested that the surfactant to oil ratio was the dominating factor governing the size and the weight percent of the dispersed phase in the nano-droplet population. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

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L’effet thermocapillaire (ou Marangoni) est la résultante mécanique d’un gradient de tensioninterfaciale induit par la présence d’un gradient de température sur une interface fluide. Il semanifeste par (i) la migration d’un objet fini (goutte, bulle) immergé, et (ii) une déflexion del’interface. Sa nature interfaciale le rend particulièrement pertinent à petite échelle, notammenten microfluidique diphasique. Ce travail de thèse montre comment un effet thermocapillaireinduit localement par chauffage laser peut être utilisé pour produire des composants optofluidiquesélémentaires (vanne, aiguillage, échantillonneur), et en présente une étude quantitative.La déstabilisation d’un jet microfluidique forcée par laser, conduisant à sa rupture, est égalementprésentée et caractérisée. Cette « boîte à outils » optique fournit ainsi une approche sans contact,pour produire et manipuler des gouttes en microfluidique digitale sans nécessité d’une microfabricationdédiée. Par ailleurs, afin de caractériser sur des temps longs les gouttes produites,et ainsi considérer des populations statistiquement significatives, un dispositif optoélectroniquesimple pour mesurer les gouttes et leur vitesse en temps réel a également été développé. / The thermocapillary (or Marangoni) effect is the mechanical result of an interfacial tension gradientinduced by a temperature gradient on a fluid interface. This effect manifests itself byinducing (i) the migration of an immersed finite-size object (droplet, bubble), and (ii) a deflexionof the interface. Due to its interfacial nature, the Marangoni effect is particularly relevantat small length scales, especially in the context of two-phase microfluidics. This thesis aims atapplying the thermocapillary effect locally induced by laser heating, in order to create some basicoptofluidic actuators (valve, switch, sampler). A quantitative study of these actuators is presented.The laser-forced destabilization of a co-flowing microfluidic jet, leading to its breakup,is also investigated. This “optical toolbox” represents a non-contacting, and microfabricationfreeapproach for the production and handling of droplets in digital microfluidics. Moreover, tocharacterize these droplet over long times, thus considering statistically significant populations,a simple optoelectronic device has been developed for measuring the size and velocity of thedroplets in real time.

Dans les 50 dernières années, les avancées dans le domaine de la protection des plantes ont contribué à augmenter les rendements et à assurer une large production. Facile à utiliser et plutôt bon marché à l’époque, les pesticides ont prouvé leur efficacité. Cependant, quand ils sont appliqués aux cultures, une partie du produit n’atteint pas sa cible et est perdu dans l’air ou au sol. Par conséquent, des efforts ont été consentis pour améliorer leur efficacité et leur innocuité sanitaire, souvent grâce à des lois environnementales internationales. Les produits sont appliqués à partir de matériels combinant type de buse/pression induisant des gammes de vitesses et de tailles de gouttelettes très diverses (Chapitre 2). Une mesure simultanée de ces vitesses et tailles est ainsi d’une grande importance dans le processus de pulvérisation. Il existe de nombreuses méthodes pour la mesure des caractéristiques des gouttelettes qui peuvent être divisées en trois catégories: mécaniques, électriques et optiques. Ces dernières apparaissent comme les plus pertinentes puisqu’étant non invasives et en perturbant donc pas le processus de pulvérisation. Les améliorations récentes dans le domaine du traitement des images et la réduction du coût des systèmes d’imagerie ont ainsi accru l’intérêt des techniques d’imagerie rapide pour les applications agricoles telles que la pulvérisation de pesticides. Cette thèse s’est donc focalisée sur le développement d’une telle technique pour la caractérisation des sprays (micro et macro). Les travaux effectués ont permis de démontrer que les caractéristiques d’un jet de pesticides peuvent être correctement et précisément mesurées par des techniques d’imagerie non-invasives couplées à des traitements spécifiques. Les travaux à venir consisteraient notamment en l’amélioration de la précision des mesures effectuées: précision sub-pixellique, calcul des profondeurs de champ, mesure de particules non sphériques. / In recent years, advances in plant protection have contributed considerably to increasing crop yields in a sustainable way. Easy to apply and rather inexpensive, pesticides have proven to be very efficient. However, when pesticides are applied to crops some of the spray may not reach the target, but move outside the intended spray area. This can cause serious economic and environmental problems. Most of the pesticides are applied using agricultural sprayers. These sprayers use hydraulic nozzles which break the liquid into droplets with a wide range of droplet sizes and velocities and determine the spray pattern. Small droplets are prone to wind drift, while large droplets can runoff from the target surface and deposit on the soil. Therefore, efforts are being undertaken to come to a more sustainable use of pesticides which is more and more regulated by international environmental laws. One of the main challenges is to reduce spray losses and maximize spray deposition and efficacy by improving the spray characteristics and the spray application process. Because mechanisms of droplets leaving a hydraulic spray nozzle are very complex and difficult to quantify or model, there is a need for accurate quantification techniques. The recent improvements in digital image processing, sensitivity of imaging systems and cost reduction have increased the interest in high-speed (HS) imaging techniques for agricultural applications in general and for pesticide applications in specific. This thesis focused on the development and application of high speed imaging techniques to measure micro (droplet size and velocity) and macro (spray angle and shape, liquid sheet length) spray characteristics.The general aim was to show that the spray characteristics from agricultural spray nozzles can be measured correctly with the developed imaging techniques in a non-intrusive way. After a review of the spray application process and techniques for spray characterization (Chapter 2), two image acquisition systems were developed in Chapter 3 based on single droplet experiments using a high speed camera and a piezoelectric droplet generator. 58 combinations of lenses, light sources, diffusers, and exposure times were tested using shadowgraph (background) imaging and evaluated based on image quality parameters (signal to noise rate, entropy ratio and contrast ratio), light stability and overexposure ratio and the accuracy of the droplet size measurement. These resulted into development of two image acquisition systems for measuring the macro and micro spray characteristics. The HS camera with a macro video zoom lens at a working distance of 143 mm with a larger field of view (FOV) of 88 mm x 110 mm in combination with a halogen spotlight and a diffuser was selected for measuring the macro spray characteristics (spray angle, spray shape and liquid sheet length). The optimal set-up for measuring micro spray characteristics (droplet size and velocity) consisted of a high speed camera with a 6 μs exposure time, a microscope lens at a working distance of 430 mm resulting in a FOV of 10.5 mm x 8.4 mm, and a xenon light source used as a backlight without diffuser. In Chapter 4 image analysis and processing algorithms were developed for measuring single droplet characteristics (size and velocity) and different approaches for image segmentation were presented. With the set-up for micro spray characterization and using these dedicated image analysis algorithms (Chapter 4), measurements using a single droplet generator in droplet on demand (DOD) and continuous mode were performed in Chapter 5. The effects of the operating parameters, including voltage pulse width and pulse amplitude with 4 nozzle orifice sizes (261 μm, 123 μm, 87 μm and 67 μm) on droplet diameter and droplet velocity have been characterized (...)

[ES] La industria y la comunidad investigadora están trabajando para desarrollar herramientas y tecnologías que contribuyan a la reducción de emisiones contaminantes. Uno de los sectores afectados por la normativa anticontaminación es el transporte. Nuevas tecnologías están evolucionando, especialmente componentes de los sistemas de inyección, diseño de cámaras de combustión, elementos de postratamiento, la hibridación, entre otros. Los sistemas de reducción catalítica selectiva (SCR) han sido una de las claves para alcanzar los objetivos de las normativas de emisiones, especialmente de Óxidos Nitrosos (NO𝑥). La tecnología SCR se emplea para eliminar los NO𝑥 presentes en los gases de escape de un motor. El proceso de inyección de la solución de urea-agua (UWS) determina las condiciones iniciales para la mezcla y evaporación del fluido en el sistema de reducción catalítica selectiva. Para un correcto funcionamiento, el inyector UWS debe dosificar una cantidad adecuada de líquido en el tubo de escape para evitar la formación de depósitos y garantizar la eficiencia del post-tratamiento. Esta tarea requiere la caracterización hidráulica del inyector y de la evolución del spray. El objetivo de esta tesis es la comprensión de los procesos de inyección de solución urea-agua en condiciones de funcionamiento realistas, similares a las que se encuentran en un tubo de escape de motor. Para ello, este trabajo se centra en el desarrollo de nuevas instalaciones experimentales que permitan realizar la caracterización hidráulica combinando medidas de flujo de cantidad de movimiento y masa inyectada. Posteriormente, el chorro de UWS se visualiza aplicando técnicas ópticas a varios niveles de temperatura y flujo másico de aire, en un banco de pruebas diseñado para este propósito. En cuanto a la caracterización hidráulica del inyector de UWS, el método se basa en medir el flujo de cantidad de movimiento para comprender la influencia de diferentes variables como el fluido inyectado, la presión de inyección, entre otros. Las medidas se realizaron utilizando una instalación experimental desarrollada en CMT-Motores Térmicos para la determinación del flujo de cantidad de movimiento, la cual fue modificada para cumplir con los requisitos de operación de estos inyectores. Además, la masa inyectada se obtiene experimentalmente para las mismas condiciones de funcionamiento. La metodología propuesta permitió calcular el flujo másico de estos atomizadores de baja presión, así como el coeficiente de descarga, que son datos útiles para futuras actividades de modelado. Se diseñó una instalación experimental para estudiar la atomización del fluido UWS en condiciones similares a las del tubo de escape del motor. La evolución del spray se caracterizó desde el punto de vista macroscópico, desarrollando una metodología para la determinación de la penetración y del ángulo del chorro. El método se basa en la configuración óptica conocida como diffused-back-light en una configuración de campo lejano. La penetración del spray se dividió en dos zonas: el inicio del chorro y el cuerpo principal. Se observó que la parte inicial del spray inyectado no se ve particularmente afectada por la presión de inyección sino más bien por la temperatura de la camisa de enfriamiento del inyector. El proceso de atomización se investigó mediante la misma técnica de diagnóstico óptico, diffused-back-lighting, acoplado a una lente microscópica especial. Se cuantificó la distribución del diámetro de las gotas y la velocidad de las gotas (en los componentes axial y tangencial) del chorro, en diferentes niveles de presión de inyección y flujo de aire. Se empleó una cámara de alta velocidad para capturar las imágenes de la fase líquida, comparando las gotas de líquido atomizado en tres regiones diferentes del chorro. Como resultado de este estudio, se puede observar que una mayor presión de inyección produce más gotas con diámetros menores favoreciendo el proceso de atomización. / [CA] Noves tecnologies estan evolucionant, especialment components dels sistemes d'injecció, disseny de cambres de combustió, elements de posttractament, la hibridació, entre altres. Els sistemes de reducció catalítica selectiva (SCR) han sigut una de les claus per a aconseguir els objectius de les normatives d'emissions, especialment d'Òxids Nitrosos (NO𝑥). La tecnologia SCR s'empra per a eliminar els NO𝑥 presents en els gasos de fuita d'un motor. El procés d'injecció de la solució d'urea aigua (UWS) determina les condicions inicials per a la mescla i evaporació del fluid en el sistema de reducció catalítica selectiva. Per a un correcte funcionament, l'injector UWS ha de dosar una quantitat adequada de líquid en el tub d'escapament per a evitar la formació de depòsits i garantir l'eficiència del post-tractament. Aquesta tasca requereix la caracterització hidràulica de l'injector i de l'evolució de l'esprai. L'objectiu d'aquesta tesi és la comprensió dels processos d'injecció de solució urea-aigua en condicions de funcionament realistes, similars a les que es troben en un tub d'escapament de motor. Per a això, aquest treball se centra en el desenvolupament de noves instal·lacions experimentals que permeten realitzar la caracterització hidràulica combinant mesures de flux de quantitat de moviment i massa injectada. Posteriorment, el doll de UWS es visualitza aplicant tècniques òptiques a diversos nivells de temperatura i flux màssic d'aire, en un banc de proves dissenyat per a aquest propòsit. Quant a la caracterització hidràulica de l'injector de UWS, el mètode es basa a mesurar el flux de quantitat de moviment per a comprendre la influencia de diferents variables com el fluid injectat, la pressió d'injecció, la contrapressió i la temperatura del sistema sobre les característiques del flux. Les mesures es van realitzar utilitzant una instal·lació experimental desenvolupada en CMT-Motores Térmicos per a la determinació del flux de quantitat de moviment, la qual va ser modificada per a complir amb els requisits d'operació d'aquests injectors. A més, la massa injectada s'obté experimentalment per a les mateixes condicions de funcionament. La metodologia proposada va permetre calcular el flux màssic d'aquests atomitzadors de baixa pressió, així com el coeficient de descàrrega, que són dades útils per a futures activitats de modelatge. Es va dissenyar una instal·lació experimental per a estudiar l'atomització del fluid UWS en condicions similars a les del tub d'escapament del motor. L'evolució de l'esprai es va caracteritzar des del punt de vista macroscòpic, desenvolupant una metodologia per a la determinació de la penetració i de l'angle del doll. El mètode es basa en la configuració òptica coneguda com diffusedback-light en una configuració de camp llunyà. La penetració de l'esprai es va dividir en dues zones: l'inici del doll i el cos principal. Es va observar que la part inicial de l'esprai injectat no es veu particularment afectada per la pressió d'injecció sinó més aviat per la temperatura de la camisa de refredament de l'injector. El procés d'atomització es va investigar mitjançant la mateixa tècnica de diagnòstic òptic, diffused-back-lighting, acoblat a una lent microscòpica especial. Es va quantificar la distribució del diàmetre de les gotes i la velocitat de les gotes (en els components axial i tangencial) del doll, en diferents nivells de pressió d'injecció i flux d'aire. Es va emprar una càmera d'alta velocitat per a capturar les imatges de la fase líquida, comparant les gotes de líquid atomitzat en tres regions diferents del doll: la primera prop de l'eixida de la tovera i les altres dues a la regió desenvolupada de l'esprai, una alineada amb l'eix de l'injector i l'altra en la perifèria del mateix. Com a resultat d'aquest estudi, es pot observar que una major pressió d'injecció produeix més gotes amb diàmetres menors afavorint el procés d'atomització. / [EN] One of the sectors affected by the anti-pollution regulations is the transportation, since it is responsible for around 20% of the green house gases emissions production. New technologies are evolving, especially subsystems as fuel injection components, combustion design, after-treatment and hybridization. The SCR has been one of the most important to reach the emission targets, specially for Nitrous Oxides (NO𝑥). The SCR technology is employed in the elimination of the NO𝑥 present in the exhaust gases of a combustion engine. The injection process of the urea-water solution (UWS) determines the initial conditions for the mixing and evaporation of the fluid in the selective catalytic reduction system. For a proper operation, the UWS injector must dose an adequate amount of liquid into the exhaust pipe to avoid deposit formation and to guarantee the SCR system efficiency. This task requires the knowledge of the performance of the injector and the evolution of the spray. The goal of this thesis is the comprehension of the urea-water solution injection processes under realistic operating conditions, similar to those of an engine exhaust pipe. To this end, this work focuses on the development of new experimental facilities that enable to perform the hydraulic characterization combining momentum flux measurements and injected mass. Afterwards, the UWS jet is visualized by applying optical techniques at various levels of air temperature and mass flow, in a novel test rig designed for this purpose. Regarding to the hydraulic performance of the UWS injector, the approach is based on measuring the spray momentum flux in order to understand the influence of different variables as injected mass, injection pressure, back pressure and cooling temperature on the flow characteristics. The measurements were carried out using an experimental facility developed at CMT-Motores Térmicos for the determination of spray momentum flux, where the configuration of the system was customized to fulfill the injector operation requirements. Also, the injected mass is obtained experimentally for the same operating conditions. The proposed methodology allowed to calculate the mass flow rate of this low pressure atomizers and the discharge coefficients, which are useful data for future computer modeling activities. A dedicated test facility was designed to study UWS spray under conditions that resemble those of the engine exhaust pipe. The liquid spray evolution is characterized from the macroscopic point of view, developing a methodology for the determination of the spray penetration and spreading angle. The method is based on the optical setup known as back-light in a far-field configuration. The spray penetration was divided in two zones, the spray burst and the body, where it was observed that the initial part of the injected spray is not particularly affected by the injection pressure but was rather influenced by the cooling temperature of the injector. Besides, the liquid atomization process of the UWS dosing system is investigated using optical diagnosis through back-light imaging coupled with a special lens. The droplet diameter distribution and the droplet velocity (in the injector axial and tangential components) of the liquid spray are quantified under different air flow and injection pressure levels. A high-speed camera was used for capturing the liquid phase images, comparing the atomized liquid drops in three different regions of the plume: the first one near the nozzle exit, and the other two in the developed region of the spray, one aligned with the injector axis and the other at the spray periphery. The results of this study demonstrated that injection pressure produces more droplets with smaller diameters favoring the atomization process. / Moreno, AE. (2022). Experimental Study of the Urea-Water Solution Injection Process [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181637