Degradation of poly(vinyl chloride) by U.V. radiation—I. Kinetics and quantum yields |
| |
Authors: | Christian Decker Michel Balandier |
| |
Affiliation: | Laboratoire de Photochimie Générale, Equipe de Recherche Associée au CNRS, Ecole Nationale Supérieure de Chimie, 68093 Mulhouse Cedex, France |
| |
Abstract: | The kinetics of the photodegradation of films of poly(vinyl chloride) (PVC) has been studied both in the presence and in the absence of oxygen. The value of the quantum yield of hydrogen chloride evolved, φHCl = 0.011, indicates that only one in every 100 photons absorbed induces the dehydrochlorination of PVC, with formation of polyenes. The independence of φHCl on the irradiation time and on the initial amount of unsaturation in the polymer argues in favour of an alkene-photosensitized degradation process. The low rate of degradation observed when Pyrex-filtered light is used results primarily from both low absorbance of the PVC film in the 300–400 nm region and photobleaching of the polyenes by the hydrogen chloride evolved. The decrease of φHCl for extended irradiation times is attributed to the formation of a highly absorbing surface layer consisting of totally degraded PVC. Competitive chain scission and crosslinking processes develop in the PVC film photolyzed either in nitrogen or in oxygen, with a limiting value of 0.5 for the gel fraction. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|