Synergistic Effect of Thermal Stabilization and Plasticization of Epoxidized Cardanol Esters on PVC

The development of a heat stabilizer with good thermal stability, plasticizing performance, and migration resistance for polyvinyl chloride (PVC) is still a notable challenge. In this work, two bio-based heat stabilizers, epoxidized cardanol oleate (ECD-OA) and epoxidized cardanol myristate (ECD-MA), were designed and synthesized with different lengths of their alkyl chains and different epoxy contents to provide outstanding compatibility with PVC. After confirming the chemical structures of ECD-OA and ECD-MA by proton nuclear magnetic resonance and Fourier-transform infrared spectroscopy, the thermal stabilizing effects of both epoxidized cardanol esters were compared with those of the traditional CaSt 2 /ZnSt 2 stabilizer and bio-based epoxidized soybean oil. Then, the effects of four different heat stabilizers on the mechanical, thermal, rheological, and optical properties of PVC films were fully studied. The results suggested that the ECD-MA showed the best thermal stability, and the PVC/30DOP/5ECD-MA film did not turn black after 2 h of thermal aging at 200 °C. In addition, the ECD-MA had good compatibility with PVC, and it had a synergistic plasticizing effect, which caused the film to have a high ductility and tensile strength (320.1% and 19.8 MPa, respectively).