Optimal design, characterization, and thermal stability of bio-based Ca/Na/Zn composite stabilizer derived from myrcene for poly(vinyl chloride)

Abstract

An adduct of myrcene and maleic anhydride (AMMA) was synthesized using a Diels-Alder reaction. The adduct was transformed into the corresponding sodium, calcium salt and zinc salts (Na-AMMA, Ca-AMMA, and Zn-AMMA) using a metathesis reaction. The chemical structures of AMMA, Na-AMMA, Ca-AMMA, and Zn-AMMA were confirmed with Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma-atomic emission spectrometry (ICP-AES), 1H and 13C nuclear magnetic resonance (1H NMR and 13C NMR), and X-Ray Diffraction (XRD). Mixed Ca/Na/Zn salts from AMMA provided thermal stabilization for poly (vinyl chloride) (PVC). The thermal and mechanical properties of the PVC samples were investigated using discoloration and Congo red tests, scanning electron microscopy analysis (SEM), thermal gravity analysis (TGA), TGA–FTIR analysis, thermal gravity-mass spectrometer analysis (TGA-MS), and dynamic mechanical analysis (DMA). Optimal design of the Ca/Na/Zn-AMMA formulation was studied. The application of Ca/Na/Zn-AMMA in an optimized formulation for a biobased, primary thermal stabilizer for PVC could significantly improve PVC thermal stability. The optimized Ca/Na/Zn-AMMA formulation had higher thermal stability, higher storage modulus, and lower glass transition temperatures than PVC blends without any thermal stabilizers and using commercial CaSt2/ZnSt2. The weights of the Ca/Na/Zn-AMMA samples were 33.3–75.0% that of CaSt2/ZnSt2, but provided higher thermal stability. Myrcene-derived Ca/Na/Zn-AMMA was shown to have strong potential as a primary PVC thermal stabilizer.