The synergistic effect of zinc urate with calcium stearate and commercial assistant stabilizers for stabilizing poly(vinyl chloride)

Zinc urate (Zn3Ur2) is synthesized by the reaction of uric acid and zinc acetate, and the structure of the complex is confirmed by Elemental analysis (EA), Thermogravimetric analysis (TGA) and Infrared spectroscopy (FTIR). The thermal stability effect of Zn3Ur2 with its assistant thermal stabilizers about calcium stearate, β-diketones and polyols on Poly (vinyl chloride) (PVC) is investigated by TG, Congo red test and Discoloration test. The results show that the thermal stability of PVC is increased significantly after Zn3Ur2 is added. Compared with traditional commercial thermal stabilizer such as ZnSt2, Zn3Ur2 can observably delay the “Zinc burning” of PVC and the complete discoloration time is improved to 150 min. This is mainly attributed to the anions in the structure of Zn3Ur2, which could efficiently absorb the HCl released by PVC and have ability to replace unstable chlorine atoms on structure of PVC. Moreover, the mixing of Zn3Ur2 and calcium stearate (CaSt2) can signally promote the long-term thermal stability of PVC. The thermal stability of PVC reaches the optimal state when the ratio of CaSt2/Zn3Ur2 is 1.8/1.2 and its total black time arrives at 210 min. In addition, an excellent synergistic effect can be observed when CaSt2/Zn3Ur2 is combined with other commercial assistant stabilizers. The initial color and long-term stability of PVC containing CaSt2/Zn3Ur2 is markedly improved when Dibenzoylmethane (DBM) is added while Pentaerythritol (PER) can only increase its long-term stability.