A novel liquid Ca/Zn thermal stabilizer synthesized from tung-maleic anhydride and its effects on thermal stability and mechanical properties of PVC

A novel liquid Ca/Zn thermal stabilizer was synthesized from tung-maleic anhydride (TMA) as feedstock and evaluated for its stabilizing effects on poly (vinyl chloride) (PVC). First, N-(3-amino-benzoic acid) tung-maleamic acid (ABTMA) was prepared from the ammonolysis of TMA and para-aminobenzoic acid (PABA). Then its complex calcium salt (ABTMA-Ca) and zinc salt (ABTMA-Zn) were synthesized through a one-step method, and investigated by Fourier transform infrared spectroscopy and elemental analysis. ABTMA-Ca and ABTMA-Zn were separately treated with diethylene glycol monobutyl ether at 120 °C for 3 h to form liquid ABTMA-Ca (LABTMA-Ca) and liquid ABTMA-Zn (LABTMA-Zn). The effects of LABTMA-Ca/LABTMA-Zn, CaSt2/ZnSt2 and C36DA-Ca/C36DA-Zn on thermal stability of PVC were studied through Congo Red test, discoloration tests and dynamic thermal stability analysis. The LABTMA-Ca/LABTMA-Zn thermal stabilizer exhibit excellent long-term stability. Analysis of tensile and dynamic mechanical properties shows PVC samples stabilized with LABTMA-Ca/LABTMA-Zn and the other two Ca/Zn systems all display comparable strength, modulus and glass transition. A common stabilizing mechanism of LABTMA-Ca/LABTMA-Zn system and its radical mechanism were presented, respectively.