THERMAL DEGRADATION OF POLYVINYLCHLORIDE IN SOLUTION .V. EFFECT OF DIMETHYLFORMAMIDE AS SOLVENT

The thermal degradation of polyvinylchloride (PVC) at 12·5 g/l. in dimethylformamide (DMF) has been studied at 130° by following the changes which occur in the u.v. and visible absorption spectra of the solutions. Degradations in vacuo and under nitrogen gave similar spectra having broad absorption bands with maxima at 478 mμ, while those carried out in air, or in an atmosphere of oxygen, gave spectra in which the absorbance was at a maximum at around 320-340 mμ, and fell off rapidly with increase in wavelength. A distinct change in spectral pattern was observed when oxygen was admitted to a solution which had been partially degraded in vacuo: the effect was not so pronounced when the process was reversed. During the degradations no hydrogen chloride gas was liberated: it dissolved in the DMF to form a complex which decomposed yielding dimethylamine hydrochloride which was found to be a catalyst for the degradation. Viscosity measurements on vacuum degraded solutions through which oxygen had been passed for various periods at 70°, indicate that the degradation occurs mainly at the ends of the polymer chains. © 1968.