Abstract: Two kinds of novel ricinoleic diacids were synthesized via the reaction of ricinoleic acid with maleic anhydride, or hexahydrophthalic anhydride. And the corresponding metal soaps of ricinoleic diacid were also prepared. Through the method of Congo red test, conductivity test, and thermogravimetry, the thermal stability of the castor oil base metal soaps, calcium isooctanate, and zinc isooctanate were determined. “Zinc burn” was depressed when adding zinc carboxylates of castor oil diacid to PVC. When the zinc ion content was 2 %, the static and dynamic thermal stability times were 9.8 min and 9.2 min, respectively. The best synergistic effect was achieved between calcium isooctanate and zinc carboxylates of castor oil diacid. The thermal stability was changed with the ratio of Ca/Zn.

Key words: poly (vinyl chloride), plant oil, modified ricinoleic diacid, calcium/zinc thermal stabilizer, thermal stability