Stability, mechanism and unique “zinc burning” inhibition synergistic effect of zinc dehydroacetate as thermal stabilizer for poly(vinyl chloride)

A novel kind of poly(vinyl chloride) (PVC) thermal stabilizer, zinc dehydroacetate (ZnL2), was designed and synthesized using zinc acetate and dehydroacetic acid (DA) as raw materials, which had a unique "zinc burning" inhibition synergistic effect with calcium stearate (CaSt2) that was 8 times greater than that of the CaSt2/ZnSt2 combination reference stabilizer. The structure and stability of ZnL2 were confirmed by Fourier-transform infrared, elemental analysis, and thermogravimetric analysis. The stability distinction of ZnL2 and ZnSt2, and the stable effect of the two systems after being combined with CaSt2, were investigated by the Congo red test, solution acidity test, and discoloration test. The results showed that in the Congo red test the stability time of ZnL2 was 8.9 min, which was 1.3 times that of ZnSt2, and the stability time of ZnL2/CaSt2 was 13 min, which was 1.4 times that of a traditional Ca/Zn stabilizer. Furthermore, the stability time of ZnL2 was 36 min in the solution acidity test, which was 2 times higher than that of ZnSt2, and the stability time was increased to 196 min after combining it with CaSt2, which was 8 times greater than that of the Ca/Zn stabilizer. Moreover, the dehydrochlorination rate of PVC stabilized with ZnL2 was slower than with other stabilizers. The system with ZnL2/CaSt2 could effectively delay “zinc burning” because of the excellent synergistic effect in the thermal aging test, with a stability time as long as 140 min. At the same time, the mechanism of PVC stabilization by ZnL2 was studied in two simple experiments, and the stabilization mechanism of ZnL2 in PVC degradation was speculated on.