Thermal Stabilization of Poly(vinyl chloride) by Metal Carboxylates of Ximenia americana Seed Oil Under Inert Condition

The kinetics of thermal degradation of poly(vinyl chloride), (PVC) in the presence of lead, cadmium, barium, calcium and zinc soaps of Ximenia americana seed oil (XSO) was investigated under nitrogen atmosphere in the temperature range, 170-190oC. The stabilizing effects of the metal soaps were assessed by measurements of the time for degradation to attain 1% conversion, tDH and of the corresponding rate of degradation, RDH. PVC was stabilized by the metal soaps with exception of the zinc derivative, and showed a relative order of stabilization of PbXSO>BaXSO>CaXSO>CdXSO. The latter was corroborated by measurements of intrinsic viscosity of degraded PVC samples and thermogravimetric analysis. The zinc soap accentuated the degradation of PVC at a rate 5-fold higher than the value in the absence of additive at 190 oC. The calculated activation energies for the degradation process are in the range 79.76 - 85.3 kJmol-1 for PVC alone and PVC/Ba-XSO composition. Binary mixtures of Ca/Zn and Ba/Cd carboxylates both at 9:1 ratio exhibited synergistic effect on PVC stabilization.