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  • Polymer and Materials Science  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1377-1384 
    ISSN: 0887-624X
    Schlagwort(e): ozonization ; grafting ; kinetics ; radical polymerization ; EVAg-styrene ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polymers can be ozonized with an ozone/oxygen mixture to create peroxides and hydroperoxides on the polymer chain. These heat-sensitive functional groups can be used to initiate radical polymerization of vinyl monomers and give graft copolymers. The properties of these copolymers are well described in literature; however, we notice that available data concerning decomposition rate constants are inconsistent. Decomposition rate measurements, time of assay of free radicals and stability of the ozonized polymers do not give the same results. In this work, we studied the kinetics of the styrene polymerization initiated by an ozonized ethylene vinyl acetate copolymer. Consequently, the f·kd product can be calculated (f is the efficiency and kd the decomposition rate constant). The ozonized copolymer is not similar to usual radical initiators. The initial viscosity of the solution has an important effect on the calculation of the kinetic values. Activation energy and Arrhenius coefficient are different than the one obtained for the usual initiators. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polymers can be treated with an ozone/oxygen mixture to create peroxide and hydroperoxide groups on the polymer chain. These heat-sensitive functional groups can serve to initiate radical polymerization of vinyl monomers to form graft copolymers. The efficiency and the decomposition rate constant of an ozonized ethylene-vinyl acetate copolymer (EVA) are determined using the polymerization rate of styrene. The thermal polymerization of styrene is studied in the presence of non-ozonized EVA. The thermal polymerization has no effect on the polymerization of styrene at the beginning of the reaction. Transfer reactions between the growing polystyrene radical and the EVA chain are negligible. The activation energy of the decomposition rate of ozonized EVA is calculated and reaches 46 kJ/mol. The entropy variation of the decomposition reaction is also calculated. The result obtained shows an important decrease (-45 cal · mol-1 · K-1) of the entropy which is opposite to the common behaviour (-6 to +13 cal · mol-1 · K-1) expected. The efficiency observed for the ozonized polymers is low and reaches only 20% at 100°C, this can be explained by the lack of mobility of the created radicals.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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