Binary amide-containing tung-oil-based Ca/Zn stabilizers: effects on thermal stability and plasticization performance of poly(vinyl chloride) and mechanism of thermal stabilization

N-(2-amino ethyl) tung maleamic acid (AETMA) and N-(2-amino phenyl) tung maleamic acid (APTMA) were prepared from the ammonolysis of ethidene diamine (ED) and p-phenylenediamine (PPD) respectively with tung-maleic anhydride (TMA). Then LAETMA-Ca, LAPTMA-Ca, LABTMA-Zn and LAPTMA-Zn were separately synthesized through a one-step method and characterized by Fourier transform infrared spectrometry (FTIR), 1 H nuclear magnetic resonance (NMR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). LAETMA-Ca/LAETMA-Zn and LAPTMA-Ca/LAPTMA-Zn were both used as thermal stabilizers of polyvinyl chloride (PVC) and investigated using Congo red test, thermal aging test, ultraviolet-visible spectrometry, thermogravimetric analysis (TGA), TGA-FTIR, and TGA–mass spectrometry (MS). Their stabilizing efficiencies were compared with other common stabilizers. Dynamic mechanical of the PVC compounds were also studied. The LAPTMA-Ca/LAPTMA-Zn exhibits excellent long-term stability and better plasticization performance for PVC than other stabilizers, and thus can partly replace di(2-ethylhexyl) terephthalate in the processing of PVC. The mechanism underlying the stabilizing action of LAPTMA-Ca/LAPTMA-Zn is suggested.