Substituent-Driven Thermal Stabilization of PVC via Dual-Anion Benzoate Zinc Salts

Three efficient and environmentally friendly double-anion zinc salts—zinc p-tert-butylbenzoate arginine (PAZA), zinc benzoate arginine (BZA), and zinc p-nitrobenzoate arginine (NAZA)-were designed and synthesized. This study elucidated how the substituent groups in these benzoic acid derivatives influence the thermal stability of PVC. Structural confirmation of the synthesized salts was carried out using FTIR, XPS, TGA, and DSC. The Congo red test, as well as static and dynamic thermal aging tests, revealed that PAZA, BZA, and NAZA significantly outperformed single-anion zinc salts in stabilizing PVC. The superior performance was attributed to a dual mechanism: the progressive replacement of unstable chlorine atoms by two types of anions and the complexation of ZnCl 2 and scavenging of HCl by amino groups. Furthermore, Gaussian calculations and Hansen solubility parameters were employed to investigate the dissociation energy of benzoic acid-derived anions from zinc and their compatibility with the PVC matrix.