共查询到20条相似文献,搜索用时 15 毫秒
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The report concerns a special kind of anomalous flow of latices being familiar to rheopexy. The rheological properties are characterized by a sudden increase in viscosity of 2 to 3 orders of magnitude within a narrow range of shear rate. The viscosity then decreases again with increasing shear rate with a gradient of —1, corresponding to a maximum shear stress of appx. 0.1 kp · cm?2. The increase of viscosity and the shear rate at which this increase occurs, depend on the concentration and the temperature of the polymer dispersion. The rheopexy is due to the presence of groups at the surface of the latex particles being able to form hydrogen bonds. At a definite shear rate these groups interact to give a network structure of the latex particles. The network could be demonstrated by electron microscopy. 相似文献
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Eckhart Blaß 《化学,工程师,技术》1988,60(12):935-947
Formation and coalescence of bubbles and droplets. Generation and coalescence of bubbles and droplets are essential requirements for technical reactions and exchange processes. The paper deals with the dispersion of gases and liquids with the aid of single orifices and of sieve plates in liquids of various viscosities under gravity and centrifugal conditions and furthermore with the mechanical foam separation and with the coalescence of drops on inclined plates. The paper summarizes results from the literature as well as from the Sonderforschungsbereich (SFB) 153 at the Technical University of Munich. 相似文献
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C. Bellmann 《化学,工程师,技术》2003,75(6):662-668
Stability of Dispersions The importance of production and application of disperse systems in the industry is steadily growing. On the other site colloidale systems surround us every day (for example foodstuffs, pharmaceutica, and so on). With the knowledge about the mechanism of interaction forces we are able to develope new materials and improve available systems. The stability of such systems is one of the central point of research. One of the well known physical models of colloid stability is given by DLVO‐Theory. With this theory we have a tool to influence the stability of such dispersion systems. In this paper electrokinetic methods are used to investigate interaction forces in disperse systems. The influence of pH‐value, electrolyte concentration, and valency is shown. But, not in all cases the DLVO‐model works satisfactoryly. Some reasons of this behavior will be discussed. 相似文献
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The image analysis of dispersion layers in a vertical separator is realized by the development of an evaluation routine. The influence on the dispersion layer of the volume flow and hydrostatic pressure is investigated in continuous and discontinuous settling tests. A direct relationship between volumetric flow / hydrostatic pressure and dispersion layer height can be determined. The observed properties of the dispersion layer are explained by the underlying coalescence and sedimentation processes. The modeling of the dispersion layer is analyzed using four different model approaches. 相似文献
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D. A. Kouremenos 《化学,工程师,技术》1967,39(15):907-909
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Robert Weser Dr.‐Ing. Benno Wessely Sebastian Wöckel Dr.‐Ing. Ulrike Hempel 《化学,工程师,技术》2013,85(5):753-757
A new method for inline characterization of particles in high concentrated dispersions by ultrasonic backscattering is described, that is sensitive against particle size and concentration. Analyzing the backscattering signal yields the sound attenuation as well as a scattering intensity equivalent. The measurement can be performed without sampling and minimally invasive directly in the process. 相似文献
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Rheological Properties of Metal Soaps in Concentrate Aqueous Dispersions The rheological behavior and the particle size distributions of calcium stearate dispersions were examined. From these investigations it is possible to propose a suitable quality profile for metal soap dispersions. For the handling of the dispersions it is advantageous if these products have a newtonic up to a slight pseudoplastic flow behavior with an average of particle size clear under 10 microns. A quality control should comprise the analysis of alcalinity, water content, rheological behavior and particle size distribution. 相似文献
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For dispersions of anionic polyurethanes with sulfonate groups it was found that the number of particles N formed was directly proportional to the ion concentration: a is a constant containing an ion-specific factor, [SO?3]0 is considered as that amount of sulfonate groups which forms water-soluble electrolytes and polyelectrolytes not contributing to the stabilization. In addition to ionomers and water-soluble products polymer molecules without ionic groups are formed. An equation developed by Flory has been adapted to calculate the molecular weight distribution. The mean particle diameter of the resulting dispersion can be controlled not only by the amount of introduced ions but also by addition of neutral salts. 相似文献
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This review shows the relationship which exists between certain applications related and physical properties of dispersions. It also presents the possibilities at our disposal for determining such properties and influencing them in a desired manner. However, the available knowledge and methods are not sufficient for complete prediction of applications-related properties. Gaps in our knowledge and in the experimental possibilities are indicated. What is feasible is demonstrated with the aid of some typical examples. The example are selected so that certain properties of the dispersions, such as particle size, rheological behaviour, or charge behaviour exert a pronounced influence on the applications-related properties. The examples cover various material systems, such as emulsions, polymer dispersions, dispersions of active principles, and inoganic pigments. In conclusion, the article considers what knowledge and methods will be required in the future for more purooseful product develooment. 相似文献
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Polyoxymethylenes with hydrophilic groups or hydrophilic polymer sequences incorporated are dispersable in water. Especially copolymers of trioxane with free carboxylic groups can be used for this purpose. These copolymers are prepared by saponification of the corresponding estergroups containing polymers. The incorporation of estergroups in polytrioxane is possible by copolymerization, by chain transfer reactions or by grafting reactions. Polyoxymethylenes where the ionic groups are replaced by nonionic hydrophilic polymer sequences are also dispersable in water. To prepare a dispersion the polymers are dissolved under pressure in a low boiling solvent, water and, if needed, a dispersing agent are added and the solvent is evaporated. 相似文献