DEGRADATION OF ORIENTED POLY(VINYL CHLORIDE) FILMS IN THE PRESENCE OF METAL CHLORIDES

Films of poly(vinyl chloride) containing added stannous chloride and stretched at 90-degrees-C to elongations up to 600% discolour, in shades from purple to grey, when heated at 110-degrees-C. The electronic and resonance Raman spectra of such films show characteristic features, which are a function of sample preparation conditions, particularly the time of annealing at 110-degrees-C. Resonance Raman spectra show the presence of conjugated polyene sequences, as long as 30 units for the most extensively annealed samples. The electronic spectra are not explicable on this basis, and are probably indicative of a polyene-metal salt complex of the type proposed by Owen and Msayib in the case of poly(vinyl chloride) thermally decomposed in the presence of zinc chloride. Substitution of zinc chloride for stannous chloride with the present degradation conditions gives very similar electronic spectra, though substantially different from those reported by Owen and Msayib. This result is tentatively explained in terms of the very different degradation conditions.