Long chain branched polypropylene (LCBPP) crystallizes rapidly and with high nucleation density. The origin of this fast crystallization process is not well understood. It has been attributed to its complicated molecular architecture. In this research, we explore isothermal crystallization of LCBPP, 5%LCBPP and linear polypropylene (LPP) through rheological, thermal, microscopy and optical measurements at different experimental temperatures. The time resolved mechanical spectroscopy technique was used to predict the liquid-to-solid transition (gel point) at different crystallization temperatures (supercooling rates) in order to understand the structure during the crystallization process. The crystallization process of LCBPP was completed in time scale less than that of 5%LCBPP and LPP at different supercooling rates. This has been observed in all crystallization experiments using DSC, SALS and Rheometery. LCBPP exhibit stiff behavior at gel point compared to 5%LCBPP and LPP which imply that the small spherulites observed under polarized microscopy are stiff. Understanding of the rheological behavior during crystallization process will help to develop polymer with different processing conditions and applications.

La formation d'émulsions eau-dans-huile stables est un problème majeur rencontré par les pétroliers au niveau de la production mais aussi du raffinage. Afin d'essayer de prévoir ce phénomène, Total a développé une méthode de classement des huiles qui permet, à partir de leurs propriétés physico-chimiques, de déterminer a priori leur capacité à former ou non des émulsions stables. Cependant, les mécanismes interfaciaux sous-jacents ainsi que l’influence des molécules tensioactives du brut sur la stabilité des émulsions n’est pas très clair. Notre travail a consisté à étudier la contribution des acides naphténiques et des asphaltènes dans les phénomènes observés. L’étude d’huiles réelles a permis d’établir un lien entre la stabilité des émulsions et la formation à l'interface d'un gel 2D. Les études menées sur les huiles réelles dont les acides naphténiques ont été extraits ont permis de montrer que ces derniers, en compagnie de leurs formes ionisées, les naphténates, ont la capacité de réduire la stabilité des émulsions en diminuant la résistance du gel interfacial, ou même en empêchant sa formation. Les expériences réalisées sur les huiles réelles dépourvues d’asphaltènes ont permis de confirmer le rôle stabilisant des asphaltènes. Les résultats obtenus suggèrent que les asphaltènes s’adsorbent sur le gel 2D déjà formé par des tensioactifs passés de l’huile vers l’eau et le rapprochent ainsi de sa transition vitreuse. La résistance du gel interfacial s'en trouve alors augmentée, ce qui conduit à la formation d'émulsions plus stables. En croisant le classement industriel des bruts opéré par Total et les résultats de l’étude, un mécanisme global, régi par la compétition entre les acides naphténiques, les naphténates et les asphaltènes à l’interface E/H est proposé pour expliquer les différences de stabilité observées avec les différentes huiles. Lorsque les acides et les naphténates sont suffisamment concentrés, ils empêchent la formation du gel interfacial et les émulsions sont peu stables. Lorsqu’ils sont moins concentrés le rôle des asphaltènes peut alors devenir prépondérant en donnant une cohésion plus importante au gel qui se rapproche de sa transition vitreuse, ce qui conduit en général au renforcement de la stabilité des émulsions formées. / Water-in-crude oil emulsions are a major issue for oil companies in both production and refining facilities. Thanks to physical and chemical characterizations, Total set a classification which allows the decision of a crude oil ability to create stable emulsions. However the interfacial mechanisms implied and the influence of the indigenous surfactants of crude oil remain unclear. Our work consists in studying the naphthenic acids and asphaltenes contribution to the w/o emulsion stability. The study of realistic crude oils enabled the discovery of a link between the emulsion stability with the formation of a very particular interfacial behavior: a two-imensional gel. Experiments with desacidified oils have proven the destabilizing ability of naphthenic acids and their ionized form, naphthenates. They actually decrease the interfacial gel strength and can even prevent the gel formation. Asphaltenes-free crude oils have permitted to confirm the stabilizing role of asphaltenes. Rather than adsorbing directly on the interface, asphaltenes seem to adsorb on the interfacial gel already formed. The gel strength is thus increased and lead to higher emulsion stability. Thanks to these results and the industrial classification of crude oil developed by Total, a global mechanism explaining the emulsion stability process has been proposed. This mechanism is governed by the competition between asphaltenes, naphthenates and naphthenic acids at the water/oil interface. If the concentration of naphthenic acids and naphthenates is high enough, the interfacial gel cannot be formed and the emulsions are unstable. If the crude oil is not acidic enough, the asphaltenes influence increases dramatically and implies the strengthening of the gel which becomes closer to his glass transition. This generally leads to the formation of more stable emulsions.

A mathematical model of two-phase systems, such as clay suspensions, consists of a set of partial differential equations which reflect both the general laws of mechanics and the relations connecting the involved characteristics of the particular system under consideration. The latter equations are known as constitutive relations. The aim of this study was to find the constitutive relations for kaolin suspensions that are necessary when solving forward problems of fine sludge thickening processes. The task was to design and carry out experimental research of the given suspension and to find a convenient method of utilizing the results for the sake of getting the sought relationships. It follows from the applied mathematical theory of two-phase systems that the sought relationships are hydraulic conductivity of the suspension as a function of the solid-phase concentration and the dependence of the solid-phase concentration on the solid-phase stress. The first part of this study describes the experimental research. Since both the characteristics are difficult to measure, it was necessary to analyze the suspension's characteristics and their measurability. Subsequently, the process of the suspension preparation and the method of laboratory measurements were determined. The following sections present...