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  • 1
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Linear and nonlinear viscoelasticity of semidilute aqueous solutions of an unmodified reference polyacrylamide (PAM) and of a hydrophobically modified polyacrylamide (HM-PAM) in the presence of various amounts of sodium dodecyl sulfate (SDS) and at different temperatures have been examined. Oscillatory shear experiments in the linear viscoelastic domain revealed significant polymer-surfactant interaction for the HM-PAM-SDS system at a surfactant concentration of ca. 8 mmol/kg, whereas practically no surfactant effect is observed for the PAM-SDS system. The rheological features for the HM-PAM-SDS system are found to be strongly dependent upon the level of surfactant addition, with first an increase and then a decrease in the values of parameters such as the dynamic viscosity. While the position of the maximum of the viscosity curve, with regard to the surfactant concentration, is independent of polymer concentration and temperature, the strength of the network is promoted by increasing polymer content and decreasing temperature. At higher surfactant concentrations, a breakdown of chain associations occurred. A non-Newtonian shear thinning behavior, as well as a thixotropy, is detected for HM-PAM solutions in the presence of surfactant. These effects are most pronounced at ca. 8 mmol/kg SDS at the lowest temperature. The rheological features reveal that the hydrophobic associations, induced by HM-PAM-SDS interactions, play an important role for the viscoelastic properties of the system.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel method for preparation of stable emulsions of slightly water soluble compounds is described. The method implies that the slightly water soluble compound diffuses through water and becomes absorbed into polymer particles which in a previous step have been brought to absorb a water insoluble, relatively low molecular weight compound. By this two step swelling process the polymer particles can be brought to absorb more than 100 times their own volume of the low molecular weight compounds to form stable o/w emulsions of the latter, with high oil content, and with a droplet size and size distribution which is completely determined by the size of the polymer particles in the latex applied initially. Monodisperse emulsions with large droplet size could easily be prepared. When the slightly water soluble compound added in the second step is a vinyl monomer which may subsequently be polymerized, the method represents a seed technique which is especially favourable for preparation of latexes with large particles size, including monodisperse latexes, with high solid content.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2423-2434 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of desorption of monomer radicals from particles on the particle number generated in interval I of an emulsion polymerization is calculated by means of a semi steady state model. It is shown that desorption leads to an increase in the particle number, and at the same time the orders of particle number with respect to emulsifier and initiator are changing. The general equation of Nomura N∝Sz0ϱ1-zi is found to apply, z increasing from 0,6 to 1,0 with increasing desorption. The values of z and N are dependent on the exact reaction mechanisms in the monomer/polymer system and on rate constants of chemical reactions and diffusion processes involved in the particle formation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Teil 1 beschreibt die Emulgierung von Styrol mit Mischungen von Natrium-hexadecylsulfat (SHS) und Hexadecanol (HD). Zusatz von HD führte zu viel besserer Emulgierung als mit anionischem Emulgator allein. Der Effekt der Fettalkohole hing stark von der Methode ab, nach der die Emulsion bereitet wurde. Um eine feine Emulsion von Styrol zu erreichen, war es erforderlich, den anionischen Emulgator und Fettalkohol mit Wasser bei höherer Temperatur vor dem Zusatz von Styrol zu behandeln. Auf diese Weise konnten Emulsionen mit einer Tröpfchengröße von 0,5-1,0 μm mit relativ kleinen Mengen Fettalkohol unter mäßigem Rühren hergestellt werden.Die feinverteilten Monomeremulsionen, die nach dieser Methode hergestellt wurden, waren imstande, den größten Teil anionischen Emulgators zu adsorbieren.Teil 2 beschreibt die Emulsionspolymerisation mit Mischungen von SHS und HD. Mit den wirksamsten Emulgatorsystemen fand die Polymerisation hauptsächlich in den Monomertröpfchen statt. Einen Beweis dieser Hypothese lieferte die bimodale Dispersion der Latex-Partikeln, von denen der Hauptteil eine Größenverteilung besitzt, die derjenigen der Monomertröpfchen-Emulsion ähnlich ist.Die Resultate der kinetischen Messungen brachten weitere Argumente für die Initiierung und Polymerisation in den Monomertröpfchen.
    Notes: Part 1 describes the emulsification of styrene with mixtures of sodium hexadecyl sulphate (SHS), and hexadecanol (HD). Addition of HD led to a much better emulsification than with the anionic emulsifier alone. The effect of the fatty alcohol depended strongly upon the method of preparation of the emulsion. To obtain a fine dispersion of styrene it was necessary to treat the anionic emulsifier and the fatty alcohol with water at an elevated temperature prior to the addition of styrene. In this way emulsions with droplet sizes in the range of 0,5-1 μm could be prepared with relatively small amounts of fatty alcohol and with moderate stirring. The finely dispersed monomer emulsions produced by this method were capable of adsorbing the major part of the anionic emulsifier.Part 2 describes emulsion polymerization experiments with mixtures of SHS and HD. With emulsifier systems providing the most effective emulsification, the monomer droplets became the main loci for particle initiation and polymerization. Evidence for this hypothesis was provided by the bimodal dispersion of the latex particles, the major part being particles with a size distribution similar to that of the monomer droplet emulsion. The results of the kinetic investigations provided additional arguments for a mechanism involving initiation and polymerization in monomer droplets.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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