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  • 1
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Determination of the particle size in PVC latices at average particle diameters smaller than 40 nm is achieved by ultracentrifugation combined with strioscopic detection. Bimodal distributions having maxima above and below 40 nm can be characterized by ultracentrifugation and separate detection by turbidimetric and strioscopic methods. Ultracentrifugation, electron microscopy, light scattering and turbidimetry provide comparable particle diameters of monomodal latices for corresponding average values.
    Notes: Die Bestimmung der Größe von PVC-Latexteilchen mit mittleren Teilchendurchmessern kleiner 40 nm gelingt durch Ultrazentrifugation mit schlierenoptischer Detektion. Bimodale Latices mit Verteilungsmaxima oberhalb und unterhalb 40 nm können durch Ultrazentrifugation und getrennte Detektion mittels Trübungsmessung und Schlierenoptik charakterisiert werden. Ultrazentrifugation, Elektronenmikroskopie, Lichtstreuung und Trübungsmessung führen bei monomodalen Latices für vergleichbare Mittelwerte zu gleichen mittleren Teilchendurchmessern.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 31 (1980), S. 338-339 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1974), S. 1073-1080 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Diaminopropanes exhibit strong elimination of amines from the molecular ions upon electron-impact. This is followed by secondary reactions in the course of which a substituent from the C-2 of the propane unit is eliminated and also a N-substituent to a smaller degree. Lowering the electron density at only one nitrogen atom by appropriate substituents causes a decrease in the intensity of both [M-amine]+· ions. The corresponding fragmentation processes were investigated by means of deuterium labelling.
    Notes: 1,3-Diaminopropane spalten beim Elektronestoßinduzierten Zerfall in starkem Maße aus den Molekülionen Amine ab. Dem schließen sich Folgereaktionen an, in deren Verlauf Vorzugsweise ein Substituent vom C-2 der Propankette, in geringerem Maße jedoch auch ein N-Substituent eliminiert werden. Erniedrigung der Elektronendichte an nur einem Stickstoffaton durch geeignete Substituenten führt Zu einem Intensitätsabfall beider [M-Amin]+· Ionen. Die zugrun-deliegenden Fragmentierungsprozesse wurden mit Hilfe deuterierter Verbindungen untersucht.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 452-454 
    ISSN: 1042-7147
    Keywords: emulsion polymerization ; AIBN ; monomeric emulsifiers ; latex characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Monomeric emulsifiers with different copolymerization reactivities were used as stabilizers in emulsion polymerization of styrene initiated by 2,2′ azobisisobutyronitrile (AIBN). A significant change in emulsifier function was observed between equal micellar concentrations of surface-active sodium sulfopropyl alkyl maleates and the corresponding sodium sulfopropyl dodecyl fumarate. In the presence of less reactive maleates, copolymerization mainly occurs in the interface of the monomer swollen particles, while copolymerization with the fumarate in the first period of emulsion polymerization leads to polyelectrolyte formation in the water phase.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 185-192 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The latex particles formed in the emulsion polymerization of vinyl chloride contain strong and weak acid ionic end groups on the surface and within the particles as well. After purifying the latices in mixing bed ion exchangers the different surface end groups can be determined in one experiment by conductometric titration. The determination of the overall end group content was carried out by conductometric titration of solutions of the polymer in dimethylformamide. At concentration values of 1.0 10-6 val/g surface end groups and 1.9 10-6 val/g total of end groups the errors in determination ranged between 3% and 13%. By comparative investigations the surface charge density of the latices was found to increase in the initial stage of polymerization. Further, these investigations suggest transfer reactions to the emulsifier and incorporation of the tenside into the polymer.
    Notes: Bei der Emulsionspolymerisation von Vinylchlorid gebildete Latices enthalten sowohl an der Oberfläche der Latexteilchen als auch im Innern der Partikel stark und schwach saure ionische Endgruppen. Die verschiedenen Oberflächenendgruppen können nach Reinigung der Latices an Mischbettionenaustauschern durch konduktometrische Titration in einem Arbeitsgang bestimmt werden. Die Erfassung des Gesamtgehalts an Endgruppen erfolgt durch konduktometrische Titration von Lösungen des Polymers in Dimethylformamid. Bei Konzentrationen von 1,0 · 10-6 val/g Oberflächenendgruppen bzw. 1,9 · 10-6 val/g Gesamtendgruppen liegen die einzelnen Bestimmungsfehler zwischen ±3% und 13%. Vergleichende Untersuchungen ergaben, daß die Oberflächenladungsdichte der Latices in der Anfangsphase der Polymerisation zunimmt. Sie liefern ferner Hinweise auf Übertragungsreaktionen zum Emulgator und den Einbau des Tensids in das Polymer.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 32 (1981), S. 117-119 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 49-62 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In emulsion polymerization of vinyl chloride (initial emulsifier concentration above the critical micell concentration) considerable decrease of latex particles is observed, particularly at the beginning of the reaction. The particle coalescence, as demonstrated by latex titration and ultracentrifugation, cannot be explained by insufficient electrolyte stability of the particles. The particle concentration remains constant if the polymerization process is terminated by addition of inhibitors or by monomer consumption. These results and, additionally, model calculations on the colloid stability based on the DLVO theory indicate kinetic and mechanistic relationships between polymerization reactions and particle coalescence. The particle coalescence is suggested to be caused by increased emulsifier desorption from polymerizing particles and by formation of bridges between the particles.
    Notes: Bei der Emulsionspolymerisation von Vinylchlorid (Anfangsemulgatorkonzentration oberhalb der KMK) erfolgt insbesondere zu Beginn der Reaktion eine erhebliche Abnahme der Zahl der Latexteilchen. Die durch Latextitration und Ultrazentrifugation nachgewiesene Teilchenvereinigung ist nicht auf unzureichende Elektrolytstabilität der Partikel zurückführbar. Die Teilchenkonzentrationen bleiben konstant, wenn die Polymerisation durch Inhabitorzusatz oder Monomerverbrauch unterbrochen wird. Diese Befunde und Modellrechungen zur Kolloidstabilität auf Basis der DLVO-Theorie weisen aus, daß Polymerisationsreaktion und Teilchenvereinigung in einem mechanistischen und kinetischen Zusammenhang stehen. Als mögliche Ursachen der Teilchenvereinigung werden erhöhte Emulgatordesorption von den polymerisierenden Teilchen sowie Brückenbildung zwischen Partikeln diskutiert.
    Additional Material: 18 Ill.
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  • 9
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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