Preparation of rare-earth terephthalic acid stabilizer and its effect on thermal stability of polyvinyl chloride

Lanthanum terephthalate (LTP) was synthesized using lanthanum nitrate, p -phthalic acid, and sodium hydroxide as raw materials. The products were characterized by elemental analysis and FTIR. LTP was compounded with other stabilizers for a better effect. The effects of LTP on the thermal stability and discoloration of polyvinyl chloride (PVC) were studied by the Congo red experiment and thermal aging test. The dynamic thermal stability was studied through electrical conductivity and torque rheological tests, and the mechanical properties of the material were tested through the tensile test. Using LTP as the heat stabilizer for PVC, the anti-discoloration performance was poor, but the long-term stability was satisfactory (up to 24 min). LTP was used as the main stabilizer and mixed with calcium stearate, zinc stearate (ZnSt 2 ), and pentaerythritol (PER) to obtain the best compound rare-earth thermal stabilizer. When the compounding scheme was LTP:ZnSt 2 :PER = 3:1:1, the stabilizer exhibited excellent antidiscoloration and long-term static stability (up to 39 min), which ensured excellent dynamic thermal stability, processing, and mechanical properties. The thermal stability mechanism results confirmed that LTP could absorb HCl gas freed by the decay of PVC to generate LaCl 3 , which lessened the catalysis of the HCl gas, thereby inhibiting PVC degradation. Graphical abstract