In-situ control of the morphology of multiphase latex/clay nanocomposites

The key objective of this thesis is the morphology control of latex/clay nanocomposites (LCN) which are of particular interest to water-based coating and adhesive applications. Indeed, the incorporation of inorganic fillers into a polymer matrix generally leads to better performing materials. However, a good dispersion and an alignment of the clay layers as single platelets into the polymer matrix are the prerequisites for the largest property enhancement. Such requirements have been the driving force for the development of many LCN synthetic routes. The inorganic encapsulation technique, using conventional emulsion polymerization was employed in this thesis. The natural occurring montmorrilonite clay particles were used as the inorganic fillers. The primary goal was to make a start in fine tuning the dispersion and orientation of the clay into the polymer matrix by controlling the morphology of the clay-encapsulated latex particles. We realized that with so many parameters involved the potentials of high-throughput experimentation (HTE) and on-line Raman spectroscopy should be explored, so some first attempts in this direction were made. Furthermore this thesis investigated the influence of clay on the morphology of multiphase latex particles. Clay particles are hydrophilic inorganic compounds and must be rendered (partially) hydrophobic in order to be more compatible with the in-situ synthesized polymer. In this thesis, the organic modification of clay was performed using two kinds of titanate coupling agents, titanium IV, (2-propanolato)tris(2-propenoata-O), 2-(2-methoxy-ethoxy) ethanol(KR39DS) and titanium IV, 2-propanolato, tris isooctadecanoato-0 (KRTTS), where the former is unsaturated and the second contains saturated alkyl groups. In Chapter 3, a study of the hydrolytic stability of the organoclays thus synthesized showed that the titanate modifiers used were highly susceptible to hydrolysis in the emulsion polymerization conditions. From the results obtained, it was concluded that successful clay encapsulation does not require the use of unsaturated organic modifiers as previously believed. Furthermore, emulsion polymerizations carried out with pristine clay also led to successful clay encapsulation showing that the modification step could be completely omitted. In addition to the organic modification, the influence of monomer feed composition, i.e. monomer mixtures consisting of different weight ratios of methyl methacrylate/ butyl acrylate, and the process type on the morphology of two-phase LCN was studied. It was shown that the monomer feed composition added under starved conditions strongly influenced the morphology of the LCN. Indeed, when the Tg of the encapsulating (co)polymer was well above the reaction temperature (hard polymer), anisotropic latex particles containing single clay platelets were mainly observed. In contrast, the use of a soft encapsulating polymer led to armored-like latex particles. Furthermore, only starved-feed monomer addition led to successful encapsulation: a batch process generated larger aggregates of clay particles and only a few armored-like latex particles. A heat treatment of the encapsulated clay particles showed that the clay encapsulation process was mainly kinetically controlled: after the heat treatment the clay was again on the outside of the latex particles. A mechanism of encapsulation was proposed, where the clay particles act as seed in the process (polymerization carried out from the surface of the inorganic particle). A systematic study of the effects of clay loading, surfactant concentration and surfactant type on the clay/polymer interaction was performed via a design of experiments. All three parameters were found to have significant effects on the clay/polymer interaction. In Chapter 4, three-phase PMMA/PS/MMT latex particles were synthesized from clay-containing PMMA seeds via (semi-)batch emulsion polymerization of styrene. For the interpretations of the morphologies obtained, the established theories to understand the morphology development of two-phase latex particles could be applied. An interesting observation was that clay platelets could act as physical barriers preventing diffusion of second stage polymers within the seed latex particles. A methodology to successfully conduct batch emulsion copolymerization using a parallel stirred automated synthesizer is described in Chapter 5. The most challenging step for such automated reactions was sampling. Sampling operations and inhibition were found to be the main source of errors in the determination of the partial monomer conversion-time histories. A comparison of the conversion rates of the automated reactions and the analyses of the particle size distributions and the molar mass distributions of the latexes synthesized clearly showed that the automated reactions were highly reproducible. A methodology to successfully conduct batch emulsion copolymerization using an automated parallel synthesizer is described in Chapter 5. The most challenging step for such automated reactions was sampling. Sampling operations and inhibition were found to be the main source of errors in the determination of the partial monomer conversion-time histories. A comparison of the conversion rates of the automated reactions and the analyses of the particle size distributions and the molar mass distributions of the latexes synthesized clearly showed that the automated reactions were highly reproducible. Chapter 5 also clearly demonstrated the potential of a low-cost-low-resolution portable Raman spectrometer to monitor emulsion homopolymerizations. The Raman spectroscopy technique in combination with partial least regression methods requires extensive calibration steps in order to gather large and representative data sets. Low-cost low-resolution portable Raman can be used as a conversion monitoring device and might be easy to integrate in the robotic platform

Influence of Biaxial Stress on Magnetic Behavior of Dual-Phase Steel - Experiments and Modeling

International audienceOnline magnetic NDE of DP steels is made on bands submitted to high multiaxial stress. Extraction of microstructural information from the measurement requires separating the effect of stress and microstructure. Coupled magneto-mechanical mi-cromagnetic modeling is relevant for that purpose. In this paper, magnetic behavior of DP steel under biaxial stress is carried out and compared to the modeling. It is shown that the discrepancies observed between experiments and model can be explained by the 2D assumption

Vers une politique étrangère africaine commune ? Opportunités et contraintes

La diplomatie de l’UA passera par une politique et une doctrine internationales sui generis. La marche des « Afriques » vers une intégration accrue des politiques régionales se conjugue avec les efforts d’insertion du continent dans la gouverne mondiale. Ces efforts, souvent traduits par la quête d’identification d’une seule voix s’exprimant au nom de tous et capable de défendre les positions communes, touche à des questions parmi les plus importantes des dynamiques régionales : la constructi..

Modélisation multidomaine du comportement magnéto-mécanique des aciers dual-phases

La microstructure des aciers dual-phase et leur comportement mécanique sont fortement sensibles aux variations de procédé (traitements thermiques). Un contrôle en ligne par méthode magnétique est envisagé. La méthode de modélisation retenue s'appuie sur un modèle magnéto-mécanique couplé basé sur la partition en domaines magnétiques des matériaux magnétiques. Il s'agit d'un modèle monocristallin explicite représentatif du polycristal isotrope du matériau concerné. Il prend en compte, le chargement mécanique imposé, la nature biphasée de la microstructure et les règles de localisation

Desarrollo local y microfinanzas como estrategias de atención a las necesidades sociales: un acercamiento teórico conceptual

El fenómeno de la pobreza como problema público invita a reflexionar cada vez más sobre la responsabilidad que tiene el Estado frente a la ciudadanía. El objetivo de este artículo es explorar las diferentes aproximaciones teóricas a las nociones de desarrollo local y microfinanzas para establecerlas como herramientas de atención a las necesidades socioeconómicas de las personas con escasos recursos. De ahí que, en este trabajo, partimos de la hipótesis de que el desarrollo local y las microfinanzas son, en efecto, instrumentos fundamentales para dar respuesta a las necesidades sociales, como causas de la pobreza. En realidad, al margen de la banca oficial y de los prestamistas informales, las instituciones de microfinanzas han revolucionado la financiación del desarrollo económico y social, especialmente en Asia, África y América Latina. A través de una revisión analítica de la literatura, llegamos a la conclusión de que la racionalización del microfinanciamiento es una operación conceptual de suma importancia, que debe rebasar el simple deseo de apoyar el desarrollo local y combatir a la pobreza, ya que resulta de un proceso de toma de decisiones con impactos multidimensionales.Poverty as a public issue encourages further thinking about the responsibility that the State has towards its citizens. This article aims to explore the different theoretical approaches to the notions of local development and microfinance, to establish them as tools to deal with the socioeconomic needs of underprivileged people. In this sense, the hypothesis of this paper considers that local development and microfinance are indeed essential tools to solve social needs, as a source of poverty. In fact, apart from the official banks and informal lenders, microfinance institutions have revolutionized the financing of economic and social development, especially in Asia, Africa and Latin America. Through an analytical review of literature we conclude that rationalization of microfinance is a crucial operational and conceptual stage that must transcend the goal of supporting local development and tackling poverty, as it is the outcome of a complex decision-making process with multidimensional impacts

POLÍTICAS PÚBLICAS Y COMBATE A LA POBREZA EN SAN LUIS POTOSÍ.

In this paper, the concept of poverty is taken up from the different approaches of the organizations in the world. We emphasize the situation of poverty in the state of San Luis Potosi in Mexico. This research allows the public to know that the government implements strategies to reduce poverty in San Luis Potosi, focusing on a program "National Crusade against Hunger" and its diffusion and impact on the beneficiaries thereof. It discusses the different events, from the implementation of this program, presenting the most important achievements and results to determine their effectiveness. This basic research is documentary; it is based on journal publications and review of literature and especially the officials of the "National Crusade against Hunger"

THE STATE MANAGEMENT CAPACITY INDEX IN MEXICO: A TOOL FOR MEASURING PUBLIC POLICIES IN LOCAL GOVERNMENTS

The main purpose of this paper is to present the results of the construction of a methodological instrument called the Subnational Local Governance Index (ISGL). This Index was built to contribute to the assessments of institutional capacities of local governments, in order to resolve public problems in Mexico. The construction of the Index was founded on four main features: 1) The lack of public policy in education, health, public services and housing quality, measured by the level of social backwardness, 2) the structure of government and administration, measured by the institutional capacities, 3) the quality of local government, measured by the level of credibility of the citizens through subnational governance and 4) the local financial capacity, measured by the ability to generate income and to manage the public debt. Basically, the following questions have been used to build the Index: What is the level of social backwardness at the local level? What kind of institutional structure exists at the local level? What is the profile of the public policy managers at the local level? What is the capacity to generate income? What is the level of citizens’ confidence in local governance

L’Afrique est-elle partie ? Introduction

Plus d’un milliard d’habitants, soit 25 % de la population mondiale à l’horizon 2030-2040 ; une institution pan-continentale (l’Union africaine) fédérant 54 membres ; deuxième rang derrière l’Asie de l’Est pour la rapidité de la progression de son PIB pour 2015 : l’Afrique est-elle partie ? Le bilan accablant que René Dumont (1962) dressa jadis à tout le moins en ce qui est de l’Afrique noire est-il à classer dans le musée de la désuétude ? Pour bien d’observateurs, aujourd’hui l’Afrique semb..

Towards an Analytical Habitability Grid for Heritage: the Medina of Mostaganem as a Case Study

Conservation of historic cities is limited in many countries to valorization and safeguarding which is performed utilizing several types of interventions. Many countries aware of the importance of their heritage in the development of human life, are currently concerned with their inhabitants’ participatory role in conservation. The historic cities in Algeria are not immune to this fact. Nowadays, particular attention is paid to the quality of life in historic Algerian cities which are in continuous transformation. It has become an urgent issue to inquire into the state of these medinas. The aim of this article is to design an analysis grid of habitability for these historical cities in order to interpret the quality of life, as well as the understanding of the man-made quest for ideal livability. The adopted methodology is divided into two parts: first, making the grid and second, its projection and analysis. Application of the grid requires very diverse data and a field of study. For this purpose, several tools were mobilized: a questionnaire survey, field measurements and direct diagnosis. For a positive outcome to the research, fieldwork is essential. This is the case study of the Medina of Mostaganem.La conservazione delle città storiche è limitata, in molti Paesi, alla valorizzazione e alla salvaguardia che viene eseguita utilizzando diversi tipi di interventi. Molti Paesi, consapevoli dell'importanza del loro patrimonio nello sviluppo della vita umana, sono attualmente interessati al ruolo partecipativo dei loro abitanti nella conservazione. Le città storiche in Algeria non sono immuni da questo fatto.Oggigiorno, particolare attenzione è rivolta alla qualità della vita nelle città storiche algerine che sono in continua trasformazione. Analizzare lo stato di queste città storiche è diventato un problema urgente. Lo scopo di questo articolo è di progettare una metodologia di analisi di abitabilità al fine di interpretare la qualità della vita e comprendere gli standard di vivibilità ideale.La metodologia adottata è divisa in due parti: la griglia e la sua proiezione e analisi. L'applicazione della griglia richiede dati molto diversi e un settore di studio. A tal fine, sono stati utilizzati diversi strumenti: un questionario, misurazioni sul campo e analisi diretta. Per il positivo risultato della ricerca è essenziale il lavoro sul campo: il caso studio presentato é relativo alla città di Mostaganem