Synthesis of Multifunctional Heat Stabilizer Bio-Based Ade-Zn and Its Application in PVC.

Thermal stability is a critical challenge in the application of polyvinyl chloride (PVC). This study aims to develop a bio-based multifunctional thermal stabilizer and biological compound system. Adenine was reacted with anhydrous zinc acetate to synthesize the adenine-zinc complex (Ade-Zn), and its successful synthesis was confirmed using infrared spectroscopy, elemental analysis, and TGA. The thermal stability of Ade-Zn was evaluated through oven-aging tests, thermogravimetric analysis, conductivity measurements, and Congo red tests, demonstrating its superior performance. Results showed that Ade-Zn extended the complete discoloration time of PVC at high temperatures to 2 h. Additionally, its thermal weight loss rate was significantly lower than that of commercial zinc stearate, with reductions of 3.84% and 1.75% in the first and second weight loss stages, respectively. Furthermore, UV absorption spectroscopy confirmed that Ade-Zn inhibits the formation of conjugated double bonds during PVC thermal degradation. The composite system of Ade-Zn and theophylline (Tph) was also investigated. It doubled the retention time of initial whiteness and enhanced HCl absorption capacity, antioxidant activity, and antibacterial performance to varying degrees. Transition state analysis confirmed that Ade-Zn inhibits the thermal degradation of PVC and promotes alternative reactions with lower energy barriers, leading to more thermodynamically stable products.