Abstract: Using lauric acid, tetradecane diacid, citric acid and lanthanum nitrate as precursors, a composite carboxylic lanthanum was synthesized, which was used in PVC as thermal stabilizer. By Congo red and torque rheometer, the static and dynamic thermal stability of PVC was tested. The results showed that the products behaved good thermal stability for PVC and good synergistic effect with additives. FT-IR showed that, when heated, coordination of lanthanum ion was the major factor for reducing degradation of PVC. Meanwhile, the carboxylate also could absorbed HCl. UV showed that lauric acid lanthanum was a early stage thermal stabilizer, but tetradecane diacid lanthanum and citric acid lanthanum behaved a long-term thermal stability.

Key words: carboxylic acid, lanthanum, thermal stabilizer