Effect of stabilizers in the thermal treatment of PVC—VI. An I.R. spectroscopic study of the stabilization of PVC with Ba and Cd stearates

Abstract

Infrared spectra (1800-1400 or 2200-1400 cm −1) were studied for PVC films stabilized with Ba, Cd stearate and with their equimolar mixture, and previously subjected to thermal degradation at 180° in air, or in a few cases in nitrogen. At least two types of oxygen-containing products were formed during the degradation. The use of partly deuterated stearates showed that esterification of the PVC chain cannot be regarded as the predominant mechanism of stabilization. On the other hand, the presence of atmospheric oxygen leading to the formation of carbonyl groups on the chain seems to play an essential role in the degradation. Infrared spectroscopy makes it possible to follow the consumption of barium or cadmium stearates during thermal stress on the basis of a band assigned to the antisymmetrical stretching vibration of COO − (1510 or 1550 cm −1).