Design and synthesis of polyol ester-based zinc metal alkoxides as a bi-functional thermal stabilizer for poly(vinyl chloride)

Abstract

The durability of poly(vinyl chloride) (PVC) under long term exposure to heat and ultraviolet ray can be enhanced by adding an additive to improve its thermal stability. In this work, three types of cis-1,2-cyclohexanedicarboxylic acid di-mannitol ester (CAME)-based zinc metal alkoxides with different zinc contents (i.e., CAME-Zn-1, CAME-Zn-2, and CAME-Zn-3 containing 2:1, 1:1, and 1:2 CAME:Zn(O2CCH3)2 molar ratio, respectively) were characterized for the first time as PVC thermal stabilizer additives. Fourier-transform Infrared spectroscopy (FT-IR), elemental analyses results, and thermogravimetric analysis (TGA) results confirmed the formation of Zn-O bonds in CAME-Zn; that the Zn, C, H, and O contents on the as-prepared CAME-Zn are close to the targeted contents; and that CAME-Zn-2 has the highest decomposition temperature. Congo red tests, conductivity tests, and thermal aging tests subsequently revealed that relative to pure PVC, the thermal stability for the stabilized PVC was enhanced by adding thermal stabilizer in the order of ZnSt2/CaSt2 (1:1), CAME-Zn-3, CAME-Zn-1, and CAME-Zn-2. The best thermal stabilizer, i.e., CAME-Zn-2 can resist the color change from white to grey upon heated at 180 °C for up to 60 min. Torque rheological tests showed that CAME-Zn-2 contributes plasticizing effect to PVC. CAME-Zn-2 thus effectively contributes bi-functional roles, i.e., as thermal stabilizer and plasticizer to PVC.