Enhancing the Thermal Stability of Polypropylene by Blending with Low Amounts of Natural Antioxidants

Natural antioxidants are added in very low amounts to protect a polypropylene (PP) matrix against thermo‐oxidative degradation during processing. Thus, PP is melt‐blended with caffeic, chlorogenic, trans‐ferrulic, and p‐coumaric acids, and also with flavone and 3‐hydroxyflavone at 0.1 wt% with respect to the PP matrix. Neat PP and PP blended with three traditional antioxidants are prepared for comparison. A complete structural, thermal, and mechanical characterization is conducted. Ferrulic acid and particularly caffeic acid increases the thermal stability, showing also the highest activation energy. The structural changes of PP‐based films due to the polymer thermal degradation at high temperature (i.e., 400 °C) followed by FTIR reveal that antioxidants effectively delay the thermal degradation process. The wettability and the mechanical performance are also studied to get information regarding the industrial application of such films. While caffeic acid provides a more flexible material, ferrulic acid provides higher water resistance. Finally, AFM‐QNM shows that PP with caffeic acid has the highest miscibility. In order to replace traditional petroleum‐derived antioxidant additives frequently used in the plastic industry, six natural antioxidants are blended with a polypropylene (PP) matrix to protect it against thermo‐oxidative degradation during processing. Among all the antioxidant tested, caffeic acid is the most miscible antioxidant with PP matrix and it provides better thermal protection.