Synergistic Effect of Acetonedicarboxylic Acid Diethyl Ester and Calcium/Zinc Stearates on Poly(vinyl chloride) Thermal Stability

Acetonedicarboxylic acid diethyl ester (AADE) is obtained by the interaction of ethanol with acetonedicarboxylic acid that is prepared from anhydrous citric acid. The thermal stabilizing effect of calcium and zinc stearates (CaSt(2)/ZnSt(2)) combined with AADE on poly (vinyl chloride) (PVC) is evaluated by the Congo red test, conductivity test, thermal aging test, and thermogravimetric analysis. The results of thermal stability tests show that the addition of AADE can improve not only the thermal stability but also the color stability of PVC. The improvement in stabilizing effectiveness is ascribed to the synergistic effect between CaSt(2)/ZnSt(2) and AADE. The thermal stability mechanism of AADE is also under discussion with the help of quantum chemical calculations. The results of quantum chemical calculations indicate that, besides having the ability to form complexes with zinc ion, AADE has an evident tendency to replace the allyl chloride of the PVC. The results of the thermal aging test and quantum chemical calculations show that the thermal stabilizing effectiveness of AADE is higher than that of stearoyl benzoyl methane (beta-Diketones). (C) 2014 Society of Plastics Engineers