ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
In research on the kinetics of the inhibition of the thermal polymerization of styrene, we came to the conclusion that quinones participate not only in the inhibition reaction but also in the copolymerization. We carried out the derivation of the basic kinetic equations of the process in two ways: (1) Using the usual simplifying assumptions of the theory of copolymerization (Melville-Watson method) and (2) using the stationary state method. The kinetic equations derived by the second method transform under certain conditions to the corresponding equations of simple inhibition, while the equations from the first method lead to contradictions. On the basis of the kinetic analysis it was found that the inhibition period during copolymerization of the inhibitor does not increase linearly within increasing concentration of the inhibitor, and that on the curve of conversion versus time there is an inflection point if the concentration of inhibitor is higher than a certain value. The curve of initial polymerization velocity against concentration of inhibitor has a minimum at a certain concentration (“inhibition optimum”). Experiments carried out with p-benzoquinone at 90, 105, 120, and 135°C. completely agree with what has been stated above. At the lower temperatures, except for a slight shortening of the inhibition period, no significant indications of copolymerization are apparent; the course of these experiments is well described by the equation of simple inhibition. At 120 and 135°C. copolymerization occurs to a marked extent and is well characterized by the equations derived by the second method. Finally, from the temperature dependence of the appropriate velocity constants, we determined the activation energy of the inhibition reaction (4.3 kcal./mol.) and the activation energy of copolymerization of quinone (9.4 kcal./mole).
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1958.1203012127
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