Synthesis and Application of Cardanol-Heterocyclic Amines as Photostabilizers and Antioxidants in Polylactic Acid

Due to biophenol being inherently antioxidant inefficient and cost intensive, it has no choice but to modify its chemical structure for large-scale applications. Cardanol-heterocyclic amines (BAOs) were prepared by a two-step method based on the intramolecular synergistic antioxidant effects of cardanol and nitrogen-containing heterocycles. Their thermal properties and antioxidant and photostability properties in polylactic acid (PLA) were analyzed. The cardanol-heterocyclic amines exhibited high initial decomposition temperatures as high as 380 °C. In addition, with the addition of 1% content of them to PLA, the tensile strength retention rate remained at 35% after 48 h of photoaging, which was 2–2.5 times higher than that of commercial antioxidant butylated hydroxytoluene (BHT) and remained at 67% after 144 h of thermal-oxidative aging, which was about 2 times higher than that of BHT. Among four cardanol-heterocyclic amines, BAO4 possessed superior photostability and antioxidant properties, presenting an intramolecular synergy between OH, N, and S.