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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Prostaglandins 17 (1979), S. 451-459 
    ISSN: 0090-6980
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1147-1158 
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: Treatment of cellulose by different concentrations of alkali, namely, 5-30% NaOH, changed its fine structure and transferred cellulose I into cellulose II. The decreased crystallinity due to alkali treatment and the transformation of cellulose I into cellulose II lowered the reactivity of cellulose toward the grafting polymerization reactions. Compactness of the structure as a result of the treatment of cellulose with 5% sodium hydroxide concentration decreased the rate of the grafting reaction and the grafting yield. On the other hand, such treatment of cellulose with different concentrations of alkali increased the rate of ceric consumption, i.e., increased the rate of oxidation of cellulose. Thus, the termination reaction of the grafting polymerization process may occur as a result of such oxidation and because of the increase of the active sites onto cellulose, leading to a decrease of the grafting yields and rate of grafting polymerization reaction by using the free-radical grafting process. The use of the ionic-xanthate method of grafting polyvinyl- and polyallyl-on alkali-treated cellulose shows an increase of grafting efficiency and grafting yields. Maximum grafting efficiency and yields were achieved when cellulose was treated with sodium hydroxide concentration below 15%, and maximum crystallinity indices were obtained. Using 15-25% sodium hydroxide lowered the indices of crystallinity, and lower grafting yields and grafting efficiency were achieved. Thus, transformation of cellulose I into cellulose II decreased the reactivity of these treated celluloses toward graft polymerization reactions by the use of the ionic-xanthate method. In our opinion, termination reactions may also occur and affect the results.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 40 (1989), S. 251-256 
    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: Das Redoxsystem Cellulosexanthogenat-Wasserstoffperoxid wurde mit der ionischen Xanthatmethode zur Pfropfung von Cellulose verglichen. Es wurde festgestellt, daß die Art der Zugabe des Wasserstoffperoxids zum Cellulosexanthogenat eine Rolle spielt. Die Pfropfausbeuten und die Reaktivitäten der Monomere hängen von der Konzentration des Wasserstoffperoxids ab. Weiterhin wurde die Temperaturabhängigkeit der Pfropfreaktion untersucht. Eine maximale Pfropfausbeute wird bei einer bestimmten Temperatur und Konzentration des Wasserstoffperoxids erhalten. Bei Anwesenheit von Luft in dem Reaktionssystem sinkt die Brutto-Pfropfausbeute.
    Notes: The redox system cellulose xanthogenate - hydrogen peroxide was compared with the ionic xanthate method of grafting of cellulose. It was revealed that the manner of the addition of hydrogen peroxide to the cellulose xanthate plays a role. The graft yields and the reactivities of the monomers depend on the concentration of hydrogen peroxide. The temperature dependence of the grafting reaction was also investigated, and it was found that maximum graft yields are obtained at definite temperature (ceiling temperature) and concentration of hydrogen peroxide. The presence of occluded air in the reaction mixture decreases the crude graft yield.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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