Influence of Zeolitic imidazolate framework-8 on the thermal stabilization of poly(vinyl chloride)

A zeolitic imidazolate framework material (ZIF-8) was prepared from stoichiometric zinc nitrate and 2-methylimidazole at room temperature in the presence of ammonium hydroxide. The material was characterized by a series of methods and used as a thermal stabilizer for poly (vinyl chloride) (PVC) film. The properties of the stabilized PVC were investigated using Congo red test, thermal aging test and thermal gravimetric analysis (TGA). Compared with the stabilizing efficiencies of some commonly-used reference stabilizers (e.g. CaSt 2 and ZnSt 2 ), the stabilizers including ZIF-8 [such as CaSt 2 /ZnSt 2 /ZIF-8 and ZnSt 2 /ZIF-8] exhibit better initial color stability and long-term thermal stability for PVC. The static thermal stability time was significantly prolonged from 33.13 min for PVC/CaSt 2 /ZnSt 2 to about 128.92 min for PVC/ZIF-8/ZnSt 2 at 180 °C. The superior performance is attributed to the synergistic effect of ZIF-8 and ZnSt 2 . The imidazole ligand of ZIF-8 can strongly absorb hydrogen chloride and form complexes with ZnCl 2 generated from ZnSt 2 in the PVC degradation process. In addition, the double bonds of ZIF-8 may help to form stable compounds with polyenes to further retard the PVC degradation. Dynamic mechanical and tensile properties of the PVC films were also studied.