The effect of different plasticizers on thermal stability, transparency, and migration resistance of the PVC stabilized with zinc arginine [Zn(Arg)2] was investigated. The thermal stability, migration resistance, and transparency of PVC with tributyl citrate (TBC) were better than PVC with dioctyl phthalate (DOP) characterized by oven aging method, migration test, and near infrared-visible-ultraviolet spectrophotometer. At the same time, the longer the carbon chain in citric acid esters, the better the thermal stability and transparency of PVC sample. The hydroxyl group in citric acid esters is helpful to improve the thermal stability of PVC samples. However, the elongation at break and Tg value of PVC containing DOP were very close to those of PVC containing TBC. The calculation results of Hansen solubility parameters also illustrated that DOP had better compatibility with PVC than TBC. Therefore, the excellent transparency and thermal stability of TBC plasticized PVC were attributed to the good compatibility between TBC and Zn(Arg)2, which was verified by the solubility test. Lastly, the mixture of dioctyl terephthalate (DOTP) and TBC was used as plasticizers for Zn(Arg)2 stabilized PVC. When the ratio of TBC and DOTP was 1:1, the transparency, thermal stability, and migration resistance of Zn(Arg)2 stabilized PVC samples were better than those of PVC plasticized by DOP or TBC alone. The mechanism was that the compatibility between Zn(Arg)2 and PVC was greatly improved by the synergetic effect of TBC and DOTP, resulting in the improvement of thermal stability, migration resistance, and transparency of PVC samples.

A new kind of highly efficient organic zinc thermal stabilizer for polyvinyl chloride (PVC), zinc arginine stearate [Zn(Arg)(St)], is designed by introducing the arginine and stearate to the same zinc atoms to regulate the binding energy between anions and cation. Gaussian soft is used to calculate the binding energy.The results of Fourier transform infrared spectra, elemental analysis, thermogravimetric analysis, and differential scanning calorimetry show that Zn(Arg)(St) has been successfully synthesized. Zn(Arg)(St) stabilized PVC displays excellent Congo red, static and dynamic thermal stability time, especially the excellent initial whiteness and whiteness retention time. The thermal stability mechanism of Zn(Arg)(St) attributes to the different binding energy between the two anions and zinc cation, which results in Zn(Arg)(St) continuously replacing the unstable chlorine atoms step by step by Arg and St anions. Moreover, the amino group in Arg could complex ZnCl 2 to inhibit the "zinc burning" effect, and the guanidine group could absorb HCl to inhibit the "autocatalytic effect" of HCl. In addition, Zn(Arg) (St) has a remarkable lubrication effect, which also enhances the thermal stability of PVC. Thus, Zn(Arg)(St) is an environmentally friendly thermal stabilizer for PVC with an excellent thermal stability effect. Importantly, this work also proposes a new method to design highly efficient thermal stabilizers for PVC.

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