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

Abstract Zinc urate (Zn 3 Ur 2 ) 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 Zn 3 Ur 2 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 Zn 3 Ur 2 is added. Compared with traditional commercial thermal stabilizer such as ZnSt 2 , Zn 3 Ur 2 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 Zn 3 Ur 2 , 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 Zn 3 Ur 2 and calcium stearate (CaSt 2 ) can signally promote the long-term thermal stability of PVC. The thermal stability of PVC reaches the optimal state when the ratio of CaSt 2 /Zn 3 Ur 2 is 1.8/1.2 and its total black time arrives at 210 min. In addition, an excellent synergistic effect can be observed when CaSt 2 /Zn 3 Ur 2 is combined with other commercial assistant stabilizers. The initial color and long-term stability of PVC containing CaSt 2 /Zn 3 Ur 2 is markedly improved when Dibenzoylmethane (DBM) is added while Pentaerythritol (PER) can only increase its long-term stability.