Os PCBs, do inglês Polychlorinated Biphenyls (bifenilas policloradas), é o nome genérico dado à classe de compostos organoclorados resultante da reação do grupo bifenila com cloro anidro na presença de catalisador. São tóxicos, persistentes, bioacumulativos e representam o risco de provocar efeitos nocivos à saúde humana e ao meio ambiente. Grandes quantidades de PCBs foram produzidos em vários países entre 1927 e 1977. Nos Estados Unidos a proibição ocorreu em 1977. Utilizados como fluidos dielétricos em transformadores elétricos e capacitores em todo o mundo, comercialmente conhecidos como Ascarel, dentre outras denominações, tais como Aroclor, Pyralene, Clorophen, Inerteen, Asbestol e Kneclor. Devido à alta toxicidade, a produção e comercialização dos PCBs foram proibidas no mundo todo a partir de 1980. No Brasil, transformadores que tiveram o óleo mineral isolante, contaminado por PCBs, estando em uso ou em armazenamento, segundo os critérios da Norma ABNT NBR 13882, a destinação final do óleo isolante deverá ser feita por incineração e ou descontaminação a valores inferiores a 50mg/kg. Neste trabalho realizado no Instituto de Química de São Carlos - Universidade de São Paulo, desenvolveu-se um procedimento para a descontaminação de óleo contaminado com valor conhecido acima de 50mg/kg, por percolação em coluna contendo espuma de poliuretano derivada de óleo de mamona, produzida pelo Laboratório de Química Analítica e Tecnologia de Polímeros (GQATP), obtendo-se uma redução de 55% dos níveis de PCBs em óleo contaminado. As espumas foram funcionalizadas com tiodiglicol e polissulfeto de amônio, obtendo-se respectivamente 24% e 11% de redução dos níveis de PCBs em óleo contaminado. Observou-se que a espuma de poliuretano produzida pelo GQATP, funciona como um adsorvente eficaz na remoção de PCBs, e que a utilização de n-hexano na dessorção da espuma, permite remover praticamente todos os PCBs adsorvidos. Portanto, esses tipos de espumas podem servir como adsorventes altamente eficazes na remoção dos PCBs presentes nos óleos minerais isolantes e, portanto, contribuir significativamente para a proteção do meio ambiente. / PCBs, (polychlorinated biphenyls), is the generic name given to the class of organochlorine compounds resulting from the reaction of the biphenyl group with anhydrous chlorine in the presence of catalyst. They are toxic, persistent, bioaccumulative and pose the risk of causing harm to human health and the environment. Large quantities of PCBs were produced in several countries between 1927 and 1977. In the United States the prohibition occurred in 1977. Used as dielectric fluids in electrical transformers and capacitors in the world, commercially known as Ascarel, among other names such as Aroclor, Pyralene, Clorophen, Inerteen, and Asbestol Kneclor. Due to high toxicity, production and marketing of PCBs have been banned worldwide since 1980. In Brazil, transformers that had insulating mineral oil, contaminated with PCBs, while in use or in storage, according to the criteria of the Standard NBR 13,882, the final destination of insulating oil should be by incineration or decontamination and the values below 50mg/kg. In a previous work carried out at the Chemistry Institute of Sao Carlos - University of Sao Paulo, a procedure was developed for the decontamination of oil contaminated with known value above 50 mg / kg of percolation column containing polyurethane foam derived from castor oil produced Laboratory of Analytical Chemistry and Technology of Polymers (GQATP), resulting in a 55% reduction in the levels of PCBs in contaminated oil. Foams were functionalized with thiodiglycol and Ammonium polysulfide, yielding respectively 24% and 11% reduction in the levels of PCBs in contaminated oil. It was observed that the polyurethane foam produced by GQATP function as an effective adsorbent for removal of PCBs, and that the use of n-hexane desorption of the foam allows to remove virtually all PCBs adsorbed. So these types of foam can serve as highly efficient adsorbents for the removal of PCBs present in the insulating mineral oil, and thus contribute significantly to environmental protection.

Les mousses liquides soumises à du cisaillement présentent une très grande viscosité, mais l'origine locale de la dissipation se produisant pendant cette déformation est encore mal comprise. Dans le but d'apporter quelques éléments de réponses à cette importante question ouverte, notre travail décrit le comportement observé sur quelques films connectés lorsqu'une déformation leur est appliquée. Nous avons créé un montage permettant de fabriquer un pattern élémentaire de mousse, et de modifier la taille de chaque film en contrôlant la géométrie du cadre qui le supporte. Ce montage original, auquel s'ajoute une combinaison d'appareils optiques, nous permet de révéler les processus se produisant dans le film, notamment la compétition entre son allongement ou compression, et l'extraction d'un nouveau film depuis les ménisques raccordant les films. Nous montrons de plus que cette compétition dynamique dans un film donné est affectée par la déformation de ses premiers et seconds films voisins. La géométrie particulière du montage nous a également permis de découvrir et de décrire pour la première fois une instabilité gravitationnelle se produisant lorsqu'un film épais se situe au-dessus d'un film plus mince. Nous avons mesuré la longueur d'onde de l'instabilité et l'avons comparée à des prédictions théoriques en régime linéaire. Ces différents écoulements affectent la distribution d'épaisseur dans le film, et peuvent ainsi jouer un rôle important sur la viscosité ou sur la stabilité des mousses 3D. Finalement, le montage utilisé pourra s'avérer utile à l'avenir comme rhéomètre de films liquides. / Liquid foams under shearing exhibit a large effective viscosity, and the understanding of the local origin of the dissipation occurring during deformation is unknown. In the aim to contribute to this important open problem, we tried to describe the behavior of a few connected films under deformation. We created a setup allowing to make an elementary foam sample and to modify each film size by controlling the shape of the deformable frame supporting the films. This original setup together with a combination of optical devices allowed us to reveal processes happening in the film, and especially the competition between film stretch or compression, and extraction of a new film from the menisci connecting the films. Importantly, we show that this dynamical competition in a given film is affected by the deformation of its first and even second neighbors. The unique geometry of the setup gave us the opportunity to discover and describe for the first time a gravitational instability which takes place when a thicker film is on top of a thinner one. We measured the wavelength and compared it to theoretical predictions in the linear regime. These different flows affect the thickness distribution, and may thus play an important role in the viscosity or in the stability of 3D foams. As a perspective, the designed setup could prove to be useful as a liquid film rheometer.

Les mousses sont des matériaux très largement utilisés dans l'industrie par exemple dans l'agroalimentaire ou la cosmétique. Ce sont des matériaux instables qui vieillissent au cours du temps à cause du mûrissement dû à la diffusion du gaz entre les bulles, de la coalescence qui est la fusion de deux bulles après rupture du film les séparant et du drainage dû à l'écoulement de liquide entre les bulles par gravité. Ces trois processus sont en compétition dans les mousses. Au cours de ma thèse, j'ai réalisé différentes expériences dans le but d'éliminer le drainage et d'étudier le mûrissement, la coalescence et la compétition entre les deux. Après un rappel sur la structure, le vieillissement des mousses et la description du dispositif expérimentale que j'ai mis au point pour contrôler la quantité de liquide dans la mousse, je me suis intéressée au mûrissement et à la coalescence de mousses 2D horizontales. J'ai montré tout d'abord grâce à l'analyse d'image qu'il est possible de différencier les mousses évoluant principalement par mûrissement de celles évoluant par coalescence en introduisant un paramètre de convexité sur les bulles composant la mousse. Les mousses ayant mûri sont alors utilisées pour étudier l'impact de l'humidité des mousses sur la perméabilité des films. La perméabilité est calculée à l'aide d'une nouvelle théorie prenant en compte l'humidité de la mousse. Les mousses qui coalescent, quant à elles, sont utilisées pour étudier l'impact de la fraction liquide, de la pression capillaire et de la taille des bulles sur la coalescence dans les mousses 2D. Cette étude permet de montrer qu'une analyse de ces paramètres à l'échelle de la mousse n'est pas suffisante pour conclure sur leur réel impact sur la coalescence et qu'il est nécessaire d'analyser ces paramètres à l'échelle de la bulle afin de différencier leurs effets. Pour ce faire, j'ai mis au point un programme qui permet d'isoler chaque évènement de coalescence. Ainsi, il existe une fraction liquide critique à partir de laquelle il n'y a plus de coalescence car les films entre les bulles n'existent plus. A 3D, j'ai commencé par établir un lien entre les fractions liquides surface et volumique donnant une nouvelle manière de de mesurer la fraction liquide volumique à partir d'une image de la surface. Ensuite, j'ai étudié le mûrissement de mousses humides 3D. Un des buts était de mettre en évidence la transition entre le régime sec où le rayon moyen croit comme le temps avec un exposant β =1/2 et le régime très humide où β = 1/3. J'ai réalisé des expériences de diffusion multiple de la lumière, sur des mousses confinées et trouvé de valeurs de β voisine de 1/2. Néanmoins, la mesure β dans les mousses très humides n'a pas été possible. Pour parer à cela, le projet "Soft Matter Dynamics" vise à étudier le mûrissement et le réarrangement des bulles dans les mousses humides en microgravité dans la station spatiale internationales (ISS). Mon implication dans ce projet a consisté à réaliser des protocoles de remplissage et de nettoyage de cellules en collaboration avec Airbus, à créer un programme d'automatisation de la mesure de la taille des bulles et à participer à une campagne de test du système de génération des mousses. / Foams are materials widely used in the industry, like in food industry or cosmetics industry for example. These are unstable materials that age over time by coarsening which is gas diffusion between bubbles, by coalescence which is the fusion of two bubbles after rupture of the film between them or by drainage which is the liquid flow between the bubbles due to gravity. These three processes are in competition in foams. During my thesis, I carried out various experiments in order to eliminate drainage and study coarsening, coalescence and the competition between them. After a quick reminder on foam structure and aging and a description of the experimental set-up that I made allowing to control the liquid content of the foam, I present coarsening and coalescence experiments of horizontal 2D foams. First, I show that it is possible to differentiate foams which evolved mainly by coarsening from those which evolved by coalescence. This is done using a convexity parameter that compares the convexity of the bubbles in the foams. The foams which coarsen are then used to study the impact of foam humidity on the films permeability. The permeability is calculated with the help of a new theory which takes into account the humidity of the foam. The coalescing foams are used to study the impact of the liquid fraction, the capillary pressure and the bubbles' size on coalescence in 2D foams. This study shows that an analysis of these parameters at the scale of the foam does not allow to conclude on their real impact on coalescence and that it is necessary to analyze these parameters at the scale of each bubble in order to differentiate their effects. To this end, I have developed a program that follow-up these bubbles and which isolate each event of coalescence. There is a critical liquid fraction above which there is no more coalescence because the films between the bubbles no longer exist. In 3D, I began by establishing link between surface and volume liquid fractions giving a new method to measure the volume liquid fraction from an image of the surface. Then, I studied coarsening of 3D wet foams. One of the goals was to show the transition between the dry regime where le mean radius increase with time as a power law, with an exponent β in the dry regime β =1/2 and the very wet regime where β = 1/3. I carried out multiple light scattering experiments on confined foams and found the values of $eta$ to be near $1/2. Nevertheless, the measurement of β in very wet foams wasn't possible. To counter this, the "Soft Matter Dynamics" project aims to study the coarsening and bubbles' rearrangement of wet foams in microgravity in the international space station (ISS). My involvement in this project consisted in the realisation of cell filling and cleaning protocols in collaboration with Airbus, the creation of a program for the automatisation of the bubbles' size measurement and the participation in a test campaign on the foam generation system.

The asymmetrical arrangement of cellular structure allows for an accurate functional adaptation at all levels of hierarchy, which derives excellent features for the development of new materials. The main objective of introducing a hierarchy into cellular structures is to improve the mechanical behaviour of the material while maintaining its elastic properties. A part of this work is devoted to the literature review related to the lightened cellular polymeric materials with hierarchical cellular structure. The rest is focused on the preparation of PLA based polymer structures using 3D printing, followed by a saturation in CO2 and a foaming in a silicon oil at elevated temperature. Samples were prepared from natural and white PLA filaments. Based on a series of experiments, optimal conditions for the saturation and foaming process were identified. Through 3D printing and foaming, a one-, two- and three-level hierarchy was introduced into the beam-shaped samples and the effect of the internal cell arrangement on the strain response of the material was examined by the means of a mechanical three-point bending test. Increasing the level of the hierarchy led to an increase in material resistance, which resulted in high values of strength and strain energy (toughness) based on the samples density. The best results were achieved by samples with “sandwich” structure with three levels of hierarchy and 30% filling. Despite the shorter plateau, there was a significant increase in strength and strain energy compared to gradient structures. At the same time, the contribution of the polymer structures prepared in this field of research was demonstrated by comparison with the theoretical model.

Syntactic foams are hollow particles-filled lightweight composites that are widely used in areas that require high strength while maintaining low weight and density. These foams are highly tailorable materials whose properties can be altered during the manufacturing process by changing various parameters like matrix and microballoon material type, size, distribution, as well as the volume fraction and wall thickness of microballoons. Therefore, understanding the effect of these parameter changes in the behavior of syntactic foams is very important to manufacture the foam for different applications. In the present study, syntactic foams of various volume fractions of microballoons were fabricated and different mechanical testing was conducted to study their elastic and viscoelastic behavior. Moreover, density, void content, and microstructure of the syntactic foam with varying volume fractions of microballoons were also studied to better characterize these foams. Results show that changes in the volume fraction of the microballoons had a significant impact on the elastic and viscoelastic behavior of the foams. The introduction of the microballoons into the epoxy resin decreased the density of the epoxy resin by up to 43.36% and at the same time increasing the specific modulus by up to 21.059%. In addition, representative 3D models of these syntactic foams were also developed to further study the elastic behavior of these materials which were found to be in good agreement with the experimental results. These findings will help in designing and optimizing the material properties of the syntactic foam required for different applications.

This diploma thesis deals with the preparation of solid hydrophilic sponges made of acetalized PVAl. The sponges were produced by foaming by gaseous reaction by-product. The experimental work also includes the study of active compound immobilization into the sponge (finely ground lignite as a heavy metal sorbent).

The main goal of this work is to search for new stable porous carbon-based materials, which have the ability to accommodate and store hydrogen gas. Theoretical and experimental studies suggest a close relation between the nano-scale structure of the material and its storage capacity. In order to design materials with a high storage capacity, a compromise between the size and the shape of the nanopores must be considered. Therefore, a number of different carbon-based materials have been investigated: carbon foams, dislocated graphite, graphite intercalated by C60 molecules, and metal-organic frameworks. The structures of interest include experimentally well-known as well as hypothetical systems. The studies were focused on the determination of important properties and special features, which may result in high storage capacities. Although the variety of possible pure carbon structures and metal-organic frameworks is almost infinite, the materials described in this work possess the main structural characteristics, which are important for gas storage.

Los materiales porosos están atrayendo mucha atención tanto en la Academia como en la industria por su amplia gama de aplicaciones y potenciales de desarrollo. Debido a sus superiores propiedades intrínsecas y funcionales, se han incrementado los esfuerzos para desarrollar materiales con diferente estructura, tamaño de poro y distribución, con el fin de satisfacer los requisitos en numerosas áreas de aplicación. Se pueden enunciar como ejemplos la gestión del calor, la biomedicina, la filtración, los procesos de separación, el catalizador o el soporte, el almacenamiento, el control acústico, el tratamiento del agua, entre otros. Sin embargo, una parte considerable de la investigación se ha centrado en materiales con una distribución uniforme del tamaño de los poros. No obstante, los estudios actuales sobre materiales multi-porosos indican que, con un diseño metodológico adecuado, es posible adaptar y controlar la microestructura en función de los fines de la aplicación y dar diferentes funciones a cada nivel de porosidad introduciendo diferentes tamaños de poros en la estructura unimodal. Dado que estos materiales multi-porosos bien diseñados (es decir, con distribución bimodal, trimodal y jerárquica) reducen las limitaciones debidas a la difusión con sus distintos niveles de porosidad, son excepcionalmente preferidos en aplicaciones en las que se requiere contener el flujo de fluidos y una elevada superficie. Aunque la atención en el diseño de estructuras multiporosas ha aumentado en los últimos años, los estudios sobre estos materiales multifuncionales ajustables han sido limitados. Esto se debe a que la relación entre la microestructura y las propiedades funcionales es difícil de comprender y controlar. Así pues, el diseño de materiales multi-porosos sigue siendo una tarea difícil en el mundo científico. Teniendo en cuenta la insuficiencia de estudios sobre la síntesis y caracterización de materiales multi-porosos en la literatura, se necesita especialmente la investigación más profunda y detallada de la influencia de los diferentes tamaños de poros en una misma estructura sobre las propiedades funcionales. De acuerdo con este propósito en esta tesis se sintetizaron materiales con porosidad única y múltiple siguiendo métodos de fabricación tanto novedosos como convencionales. Comparando el rendimiento de los materiales con porosidad simple y múltiple, se investigó la influencia de la microestructura en las propiedades y su relación desde diferentes perspectivas. En conclusión, los objetivos específicos de esta tesis son: i) diseñar dos nuevos enfoques experimentales para fabricar espumas metálicas de celdas-abiertas interconectadas multi-porosas utilizando metodologías conocidas y sus combinaciones. ii) demostrar el efecto de la multi-porosidad en un solo cuerpo sobre las propiedades de las espumas fabricadas y demostrar que superan, junto con los nuevos enfoques, a sus homólogos convencionales. iii) presentar nuevos hallazgos científicos y nuevos enfoques sobre la relación entre las propiedades funcionales y estructurales (porosidad, tamaño y distribución de los poros, etc.) mediante una amplia gama de caracterizaciones. iv) Ofrecer metodologías reproducibles de vanguardia para la síntesis de materiales multi-porosos que puedan aplicarse a diferentes tipos de materiales e inspirar futuros trabajos en la comunidad científica. Este estudio de tesis consta de 6 capítulos. El Capítulo 1 explica brevemente la motivación y los objetivos de la tesis. En este capítulo se expone la información sobre los materiales multi-porosos que se pretenden fabricar y el alcance de la tesis. El Capítulo 2 ofrece una introducción a los materiales multi-porosos y sus métodos de fabricación en perspectiva. Se ha realizado un amplio estudio bibliográfico y desde el pasado hasta el presente se presentan los avances y trabajos recientes realizados en la fabricación de estos materiales. En este capítulo se ha prestado especial atención a la producción de espumas metálicas monomodales, bimodales y jerárquicas mediante métodos de replicación, dealeación, plantillas, sinterización y sus combinaciones. En el Capítulo 3 se explican todas las metodologías, montajes experimentales, materiales, parámetros de funcionamiento y maquinaria/dispositivos seguidos en esta tesis sobre la fabricación y caracterización de materiales y se presenta la información teórica relevante. El Capítulo 4, en primer lugar, resume la literatura necesaria sobre la fabricación de espumas metálicas, la infiltración con el método de replicación, las espumas de aluminio y sus áreas de aplicación, y los métodos de caracterización. También se presenta en este capítulo la extensa revisión de la literatura sobre la relación entre las características microestructurales y las propiedades funcionales de los materiales porosos. Se expone cómo, mediante el método de replicación, se fabricaron espumas de aluminio interconectadas de célula abierta con una distribución monomodal y bimodal del tamaño de los poros. Después de la fabricación, se caracterizaron en detalle las propiedades estructurales (densidad, porosidad, distribución del tamaño de los poros, etc.), el comportamiento del flujo de fluidos (caída de presión, permeabilidad, coeficiente de arrastre, regímenes de flujo, etc.) y el comportamiento térmico (coeficiente de transferencia de calor, conductividad térmica) de las espumas. (coeficiente de transferencia de calor, conductividad térmica) de las espumas. El Capítulo 5 presenta un método novedoso para fabricar espumas de plata con eficacia antibacteriana y distribución jerárquica del tamaño de los poros. Para ello, se ha utilizado la combinación de métodos de templado, replicación y dealeación. Con esta combinación y el diseño adecuado de las metodologías se introdujeron micro-, meso- y macroporos en las estructuras de las espumas. Para comparar las propiedades y el rendimiento de las espumas jerárquicas, se fabricaron espumas de plata con porosidad uniforme mediante el método de replicación y el proceso de sinterización, y espumas de plata con solamente nanoporos mediante el método de dealeación. Se llevaron a cabo estudios de caracterización para todas las espumas fabricadas en el sentido de la distribución del tamaño de los poros, la porosidad, la superficie específica, la eficacia antibacteriana, además de la modelización y la estimación de la superficie específica y la distribución del tamaño de los poros. Además de los pasos de las estrategias experimentales, se presentó una información de fondo detallada sobre los principios rectores de los métodos utilizados en este capítulo. En el Capítulo 6 se evaluaron todos los estudios realizados, se resumieron los resultados y las conclusiones, y se presentaron recomendaciones y estrategias para futuros estudios. / Financial support from the Spanish “Agencia Estatal de Investigación” (AEI) and European Union (FEDER funds) through grant MAT2016-77742-C2-2-P. “Santiago Grisolía” grant (GRISOLIA/2017/187) financed by Generalitat Valenciana.

Decreasing the carbon footprint through use of renewable materials has environmental and societal impact. Foams are a valuable constituent in buildings by themselves or as a core in sandwich composites. Kenaf is a Southeast USA plant that provides renewable filler. The core of the kenaf is porous with a cell size in a 5-10 micrometer range. The use of kenaf core in foams represents a novel multiscalar cellular structural composite. Rigid polyurethane foams were made using free foaming expansion with kenaf core as filler with loadings of 5, 10 and 15 %. Free foaming was found to negatively affect the mechanical properties. An innovative process was developed to introduce a constraint to expansion during foaming. Two expansion ratios were examined: 40 and 60 % (decreasing expansion ratio). MicroCT and SEM analysis showed a varying structure of open and closed cell pores. The mechanical, thermal insulation, acoustic properties were measured. Pure PU foam showed improved cell size uniformity. Introducing kenaf core resulted in decreasing the PU performance in the free expansion case. This was reversed by introducing constraints. To understand the combined impact of having a mixed close cell and open cell architecture, finite element modeling was done using ANSYS. Models were created with varying percentages of open, closed, and bulk cells to encompass entire range of foam porosities. Net zero energy building information modelling was conducted using EnergyPlus was conducted using natural fiber composite skins. Environmental impacts for instance global warming potential, acidification, eutrophication, fossil fuel consumption, ozone depletion, and smog potential of the materials used in construction was studied using life cycle assessment. The results showed improvement on energy consumption and carbon footprint.

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