Impact of calcium soap derived from soy wax as a thermal stabilizer on discoloration and color stability of polyvinyl chloride composite

In this study, the effect of calcium soap synthesized from soybean wax, a hydrogenation product of soybean oil, on the thermal stability of polyvinyl chloride (PVC) was investigated by thermogravimetric and colorimetric methods.The calcium soap was prepared via precipitation in aqueous and alcoholic media, and its molecular structure was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR).FT-IR analysis indicated successful soap synthesis but also showed the presence of un-saponified oil residues.A commercial calcium-zinc stearate stabilizer was used for comparison.PVC mixtures containing different stabilizers and a control sample without stabilizer were processed using a heated press.Thermogravimetric analysis demonstrated that both the bio-based calcium soap and the commercial stabilizer delayed PVC thermal degradation effectively.Additional samples with titanium dioxide were also prepared to evaluate color stability.Colorimetric analysis using a portable colorimeter revealed that all PVC samples darkened after thermal exposure.The least color change was observed in samples with the commercial stabilizer, while the most significant darkening occurred in the control and bio-based calcium soap samples.These findings suggest that calcium soap synthesized from soybean wax can neutralize hydrogen chloride evolved during degradation but cannot fully prevent formation of conjugated double bonds responsible for color darkening.Therefore, it is more effective when combined with other stabilizers instead of being used alone