Studies on photodegradation of poly(vinyl chloride) (part 1)

Abstract

Films prepared from emulsion polymerized poly(viny1 chloride) were subjected at 0°C to accelerated photodegradation in air using a weatherometer. Photooxidation and scission of the main chain took place but dehydrochlorination or formation of polyenes was not observed. The absorption of the carbonyl group indicating oxidation was found at 1 725 cm-in the infrared absorption spectrum. Only when tetrahydrofuran, which had been used for the preparation of films, was left in the films, an absorption was also found at 1770cm-'. Oxidation occurred at the position of the methylene carbon and the cut end of the main chain. As a result of the X-ray photoelectronic spectrum (ESCA) analysis, it was found that the carbonyl concentration was higher in the surface layer of the sample than in the interior thereof. ZUSAMMENFASSUNG:Filme aus Emulsions-PVC wurden in Luft bei 0°C mit Hilfe eines Weatherometers dem beschleunigten Photoabbau unterworfen. Photooxidation und Kettenspaltung wurden beobachtet. Die Abspaltung von HCI oder die Bildung von Polyenen konnte nicht festgestellt werden. Die Oxidation ist gekennzeichnet durch eine Absorption im IR bei 1725cm-'. Nur bei Restgehalten von Tetrahydrofuran in den Folien tritt gleichzeitig eine Bande bei 1770cm-' auf. Die Oxidation findet an Methylengruppen und am Ende der Hauptkette statt. Das Rontgenphotoelektronenspektrum (ESCA) zeigt hohere Carbonylgruppenkonzentrationen an der Oberflache als im lnneren der Folie.

New photostabilizers for polystyrene based on 2,3-dihydro-(5-mercapto-1,3,4-oxadiazol-2-yl)-phenyl-2-(substituted)-1,3,4-oxazepine- 4,7-dione compounds

“…It is worth mentioning that traces of the films with additives are not soluble in chloroform indicating that cross-linking or branching in the PS chain does occur during the course of photolysis (Mori et al 1977). For better support of this view, the number of average chain scission (average number cut per single chain) (S) (Shyichuk & White 2000) was calculated using the equation (8):…”

New stabilizers for polystyrene based on 2‐thioacetic acid benzothiazol complexes

“…It is worth mentioning that traces of the films with additives are not soluble in chloroform, indicating that crosslinking or branching in the PS chain does occur during the course of photolysis 15. For better support of this view, the number of average chain scission ( S ; average number cut per single chain)16 was calculated using the following relation: where ( M v , o ) and ( M v , t ) are viscosity–average molecular weight at initial ( o ) and at irradiation time ( t ), respectively.…”

“…(3) with benzene as a solvent at 25 C. It is worth mentioning that traces of the films with additives are not soluble in chloroform, indicating that crosslinking or branching in the PS chain does occur during the course of photolysis. 15 For better support of this view, the number of average chain scission (S; average number cut per single chain) 16 was calculated using the following relation:…”

Photobleaching of chemically degraded poly(vinyl chloride)

“…This is in contrast to the conclusions of earlier workers28 who believed that carbonyl residues were responsible for that absorption. The assignments by Rabek of important absorbance at 280 nm is confirmed by the work of Mori et al, 29 although these authors do not agree about the assignments of absorptions in the infrared region. They attribute absorptions at 1770 and 1725 cm-l to residual THF and photooxidized PVC, respectively, the latter being formed in the presence of oxygen but in the absence of THF.…”