Synthesis of zinc Schiff base complex and its application as highly efficient thermal stabilizer for flexible poly (vinyl chloride)

N, N'-bis (salicylaldehyde) ethyldiamino-zinc (BSE-Zn) was synthesized from salicylaldehyde and ethylenediamine. Its structure was analyzed by FT-IR, 1H NMR and elemental analysis. The thermal properties of PVC samples were studied by thermal aging oven test, Congo red test, conductivity test, thermogravimetric analysis (TGA) and UV–Visible spectroscopy (UV–Vis). The thermal stability of BSE-Zn stabilized PVC samples was better than the calcium zinc soaps used in industry. The thermal stability time can be as long as 90 min, which proved that BSE-Zn was a long-term thermal stabilizer. By blending CaSt2 and BSE-Zn stabilizer in different proportions, the thermal stability of PVC was significantly improved while improving the initial color. When the compound ratio is CaSt2/BSE-Zn=2:1, the thermal stability of PVC sample was best and didn't age until 120 min. In addition, it was verified by tensile test that the PVC sample stabilized by BSE-Zn had the highest tensile strength and elongation at break, which could improve the mechanical properties of PVC and make the PVC film have better toughness and elasticity. the quantum chemical calculation of BSE-Zn and vinyl chloride models was carried out, and the thermal stability mechanism of BSE-Zn on PVC was analyzed accurately, mainly the absorption mechanism of HCl and the replacement mechanism of unstable chlorine atoms.