Literatura científica selecionada sobre o tema "Viscosimetric properties"

The effect of resins on solidification of paraffin solutions has been studied by vibration viscosimetry. This technique was used for studies of coagulating liquids, since the sample structure is less affected by mechanical oscillations compared to traditional rotary and linear shears. The installation developed for studies of thermo-induced phase transitions and the measurement procedure are described. The viscosimetric technique allows continuous registration of rheological properties with changing temperature, and has proved to be quite sensitive to small amounts of resins in model paraffin solutions. Measurements have been performed for resins extracted from methane-naphtene crudes of various West Siberia oil deposits. Dependencies of viscosity on temperature have been measured and are presented below for various concentrations of resins (up to 3 %) in paraffin solutions. It is demonstrated that increase of resin concentration results in a shift of the inflexion point on the viscosity-temperature curve to lower temperatures. A positive correlation has been found between depressant activity and average dimensions of aliphatic fragments of the resin molecu.

The present study analyzed experimental data from volumetric and viscosimetric measurements and computational simulations to understand caffeine hydration and aggregation properties in 0.1 mol∙kg−1 of sodium salicylate aqueous solution. Sodium salicylate reduces the bitter taste and increases the solubility of caffeine in water, which is the main reason for their combination in food products. The results noted in volumetric and viscosimetric measurements indicate that sodium salicylate promotes the self-aggregation of caffeine in water. After self-aggregation, the hydration number of caffeine significantly increases. Molecular simulations have allowed us to hypothesize how salicylate increases caffeine solubility. At the molecular level, relocating salicylate moiety from the parallel stacking (π–π) aromatic complex with caffeine and its hydration could be the main reason for increasing the solubility of caffeine in water. The presented study provides clear guidelines on the choice of additives to increase caffeine’s solubility in aqueous media. The choice of salicylate as an additive to increase the solubility of caffeine is very important because caffeine and salicylate are found in combination in a large number of formulations.

With the aim at controlling cellulose degradation phenomena, the natural aging of Whatman paper samples was simulated through different artificial aging processes: thermal oxidation in air at constant temperature, photo-oxidation under Xenon arc lamp, accelerating ageing in climatic chamber, and chemical oxidation with sodium methaperiodate. The cellulose degradation was studied by means of viscosimetric, Fourier transform infrared spectroscopy (FTIR), and wide angle X-ray scattering (WAXS) techniques together with thermogravimetric (TGA), mechanical, and optical analyses. All the treatments carried out were found to significantly modify paper structure and properties, the extent of the deterioration effects depending upon the aging kind. Direct correlations were, nevertheless, assessed among level of cellulose molecular degradation, formation of carboxyl, and/or carbonyl groups and paper strain at break.

It is well known that one of the factors adversely affecting the operational efficiency of infield technological oil pipelines is persistent oil emulsions formed due to the oils watercut. These hardly demulsifible emulsions with abnormal rheological features show non-Newtonian properties. Depending on the temperature and watercut degree, the viscosity of these emulsions varies widely. The specification of viscosity and other physical-chemical properties in oil-field experience is carried out via laboratory testing of oil samples according to the standards. Based on the roto-viscosimetric studies of oil samples with various temperatures, an empiric formula for the specification of oil emulsions viscosity depending on watercut degree is offered. It was defined that the offered formula enables with permissible error to specify the viscosity of abnormal emulsions considering the changing watercut and temperature aspects.

Le pétrole est à la base du développement de notre société moderne, offrant accès à une source d'énergie abondante, bon marché et facilement transportable. Il est utilisé aussi bien pour la production d'électricité que pour les transports et représente la première source de matières premières pour l'industrie chimique. La production de pétrole est généralement assurée par des réservoirs matures exploités par injection d'eau dans un but de maintien de pression ou de balayage du réservoir. Pour améliorer l'efficacité de balayage du réservoir par l'eau injectée, la technique d'injection de polymères hydrosolubles a été développée. L'addition de polymère augmente la viscosité de l'eau injectée du pétrole par un balayage plus efficace du réservoir. Il est ainsi possible d'augmenter la production de pétrole tout en diminuant l'emprunte carbone. Les principaux polymères utilisés pour cette application sont de la famille des polyacrylamides. L'optimisation du procédé requiert une connaissance précise des relations structures-propriétés des polymères utilisés afin de mieux appréhender leurs propriétés viscosifiantes et de transport en milieu poreux. L'objectif est de mettre en place des méthodes analytiques pour la détermination de la distribution en masse molaire et du taux de ramification des polymères étudiés afin de pouvoir corréler les résultats obtenus aux propriétés rhéologiques et au comportement en filtration de leurs solutions. C'est pourquoi, dans le cadre de la thèse, quatre volets (WP pour work packaging) sont abordés afin de répondre au mieux à cette problématique concernant sa structure. Le premier volet (WP1) consiste à caractériser les différents polymères industriels à travers différents outils analytiques qui sont la Chromatographie d'Exclusion Stérique (Size Exclusion Chromatography (SEC)) couplée à un détecteur de diffusion de lumière multi-angle (Multi-Angle Light Scattering (MALS)) pour la taille (masse molaire, Mw, et rayon de giration, Rg), et la rhéologie capillaire pour la viscosité intrinsèque et les courbes d'écoulement (rhéogramme). Ensuite, vient le second volet (WP2) qui a pour but d'étudier le taux de ramification des polymères. Pour ce faire, deux approches analytiques vont être utilisées. La première est la Py-GC/MS, la pyrolyse (Py) couplée à la Chromatographie en Phase Gazeuse (Gaz Chromatography (GC)) couplée elle aussi à la Spectrométrie de Masse (Mass Spectrometry (MS)) afin d'évaluer la microstructure du polymère. La deuxième partie de ce volet est la comparaison des paramètres structuraux (Mw, Rg et viscosité intrinsèque) obtenus par analyses SEC-MALS, diffusion de la lumière (MALS) et rhéologie capillaire. Un système de mélange continu automatique (Automatic Continuous Mixing (ACM)) couplé au rhéomètre capillaire et au MALS sera développé pour faire des analyses en ligne de viscosité intrinsèque et de masse molaire. Ce développement instrumental fait l'objet du troisième volet (WP3). Pour finir, le quatrième volet (WP4) consiste à étudier les propriétés des polymères pendant la filtration
The knowledge of the dimensional properties (Mw, Rg, and the distributions), the viscosimetric properties ([η]), as well as, the branching rate of polymers is primordial for the implementation of a satisfactory Enhanced Oil Recovery (EOR) via polymer flooding. The principal objective of this thesis was to develop analytical methods in order to determine the characteristics of an optimized macromolecule developed by the SNF company, the poly(sodium 2-acrylamido-2-methylpropane sulfonate) (P(ATBS)). Two categories of P(ATBS) were studied: the models and the industrials. The models of high molar masses (1-6 million g/mol) were synthetized by Controlled Radical Polymerization (CRP), for which the branching was controlled by the addition of a crosslinking agent. While the industrials of higher molar masses (8-19 million g/mol) were obtained by Radical Polymerization (RP), for which the branching could be induced by chain transfer reactions. The characterization of the dimensional/viscosimetric properties and the branching rate for both P(ATBS) categories was performed by Size Exclusion Chromatography (SEC), Frit-Inlet Asymmetric Flow Field-Flow Fractionation (FIA4F), capillary viscometry and Multi-Angle Light Scattering (MALS). A correlation of the physico-chemical properties was done to understand the behaviour of the P(ATBS) in solution. A related study was done by Pyrolysis coupled to a Gaz Chromatography and a Mass Spectrometer (Py-GC/MS) for the qualitative and quantitative analyses of the P(ATBS). To this day, the P(ATBS) has never been studied by this technique

Gelification des pectines amidees en presence de calcium. Etude de modeles simplifies (acides pectiques amides). Les pko dependent du parametre de densite de charge et non pas du taux d'amidation/repartition non aleatoire des fonctions amides. La sensibilite au calcium des pectines amidees resulte de l'alternance de blocs de fonctions acides libres et methyles reparties aleatoirement et de fonctions amides, generateurs de liaisons h intermoleculaires, provenant de leur synthese concentre en ammoniac et en pectine