Abstract: Lanthanum tyrosine was synthesized with tyrosine, lanthanum nitrate and sodium hydroxide as the raw materials. Thermal stability of lanthanum tyrosine and its compound with calcium stearate and zinc stearate was studied by means of Congo red testing method, thermal aging oven method, conductivity method, and torque rheometer. Stabilization mechanism of lanthanum tyrosine was also studied by infrared spectrum. The results indicated that lanthanum tyrosine alone had good thermal stability for PVC. Thermal degradation of PVC was slowed down by coordination of lanthanum and chlorine, and the reaction of amidogen and HCl. The composite of lanthanum tyrosine, calcium stearate, and zinc stearate could extend greatly thermal stability time and delay color change of PVC.

Key words: poly(vinyl chloride), amino acid, rare earths, calcium/zinc thermal stabilizer, synergism