Abstract: In this paper，the thermal stabilizer of Ca/Zn system for rigid PVC was studied by static and dynamic experiments and compared with four commercial ones. Its synergistic effect with organic auxiliary heat stabilizer and functional assistant was determined. It was found that the initial color and long-term thermal stability depended mainly on the ratio of calcium and zinc stearates. When the two stearates were heated at 180 ℃ for 5 minutes, the synergistic effect was enhanced and a dynamic thermal stabilizing time of 30 min was observed. PVC materials containing such stabilizing system possessed good processablity.

Key words: poly(vinyl chloride), thermal stability, synergistic effect, calcium stearate, zinc stearate