ISSN:
0021-8995
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
For a commercial polyvinyl chloride (PVC), polymerized in suspension, decomposition kinetics were studied in a nitrogen atmosphere and isothermal conditions, from 150 to 250°C., by measuring simultaneously loss of hydrochloric acid and loss of weight. Below 200°C., hydrochloric acid is the only volatile product freed; reaction is zero order and activation energy is 20 kcal./mole HCl. Active centers are mainly end chains of unsaturated structures. The reaction is terminated by mutual destruction of radicals, creating crosslinks. Above 200°C., when the degree of dehydrochlorination is high enough, a minor difference is observed between loss of weight and hydrochloric acid loss. The reaction is autoaccelerated and can be classified as a degenerated branching chain reaction. It is suggested that activation of irregular structures, initially present or created during the course of the reaction, and thus responsible for autocatalysis, provides active centers for chain dehydrochlorination. Some of these structures are active at temperatures lower than that of their formation. Each kind of structure is believed to be at the origin of a radical zero-order chain reaction; its activation energy depends on its type. The reaction chains are terminated by inactivate irregular structures.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/app.1962.070061912
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