Synthesis and Study of Zinc Orotate and Its Synergistic Effect with Commercial Stabilizers for Stabilizing Poly(Vinyl Chloride)

Zinc orotate (ZnOr(2)), which is a new kind of poly(vinyl chloride) (PVC) stabilizer, is prepared in this work through the precipitation method, and its impact on the thermal stability of PVC is measured by thermogravimetric analysis (TG), Congo red test, and discoloration test. The results exhibit that the thermal stability of PVC is positively enhanced after the addition of ZnOr(2). In contrast with a commercial thermal stabilizer, zinc stearate (ZnSt(2)), a noteworthy improvement was observed that ZnOr(2) could postpone the "zinc burning" of PVC. This is principally ascribed to the Or anion in the structure of ZnOr(2) being able to absorb the HCl released by PVC, and to supersede unstable chlorine atoms in the structure of PVC. In addition, blending ZnOr(2) with calcium stearate (CaSt(2)) in diverse mass ratios can significantly accelerate the thermal stability of PVC. Optimum performance was achieved with a CaSt(2):ZnOr(2) ratio of 1.8:1.2. Moreover, an outstanding synergistic effect can be observed when CaSt(2)/ZnOr(2) is coupled with other commercial auxiliary stabilizers. The initial color and long-term stability of PVC including CaSt(2)/ZnOr(2) is significantly increased when pentaerythritol (PER) is added, while dibenzoylmethane (DBM) can only improve its long-term thermal stability.