Stabilising effect of derivatives of Khaya seed oil on the thermal degradation of poly(vinyl chloride)

Abstract

Nonoxidative and oxidative degradation studies on poly(vinyl chloride) (PVC) were carried out at various temperatures in the presence of Khaya seed oil, epoxidised Khaya seed oil, and metal soaps of Khaya seed oil and its epoxidised derivative. Rate measurements at 1% degradation, the time required for dehydrochlorination to attain 1% conversion and changes in intrinsic viscosity and levels of unsaturation in the degraded samples were used to assess the effects of the derivatives of Khaya seed oil on the thermal susceptibility of PVC to degradation. It was found that although the values of the rate of dehydrochlorination at 1% conversion were about the same order of magnitude (10 −2% min −1), the values of the rate of dehydrochlorination and of the time required for degradation to attain 1% conversion obtained in the presence of the derivatives of Khaya seed oil were lower (by as much as 70%) and considerably higher (by up to 100%), respectively, than the values obtained in the absence of the additives. The data from solution viscosity measurements and from estimates of the number of double bonds found in the polymer samples degraded in air indicate that metal soaps of Khaya seed oil and of its epoxides exert a stabilising effect on the oxidative degradation of PVC. IR measurements on degraded PVC films containing Khaya seed oil derivatives and thermogravimetric examination of degradation of PVC containing barium and cadmium soaps Khaya seed oil up to 500°C show that the metal soaps of the seed oil are effective in stabilising PVC against thermal degradation.