Investigation of basic zinc cyanurate as a novel thermal stabilizer for poly(vinyl chloride) and its synergistic effect with calcium stearate

Basic zinc cyanurate (Zn 3 (C 3 N 3 O 3 ) 2 ·ZnO, represented as Zn 3 Cy 2 ) was synthesized via a precipitation method, and investigated as a thermal stabilizer for poly(vinyl chloride) (PVC) by thermogravimetric analysis (TGA), Congo red test and discoloration test. The thermal stability of PVC was significantly enhanced with the addition of Zn 3 Cy 2 . Compared with zinc stearate (ZnSt 2 ), it is observed a significant improvement that Zn 3 Cy 2 could delay the “zinc burning” of PVC. This is attributed to the strong ability of the cyanurate anions in Zn 3 Cy 2 to absorb the hydrogen chloride released by the degradation of PVC. Moreover, mixing Zn 3 Cy 2 with calcium stearate (CaSt 2 ) in different mass ratios greatly promoted the thermal stability of PVC. Excellent synergistic effects could be observed when CaSt 2 /Zn 3 Cy 2 combined with some commercial auxiliary stabilizers. Addition of dibenzoylmethane (DBM) brought a remarkable increase in initial color for PVC containing CaSt 2 /Zn 3 Cy 2 while epoxidized soybean oil (ESBO) could improve both initial color and long-term stability.