Pomegranate extract for the processing stabilization of polyethylene

Active components with antioxidant activity were extracted from the powder of pomegranate peel and added to polyethylene at 1000 ppm. The stabilization effect of the extract was studied also in compounds containing a phosphorous secondary antioxidant. A commercial hindered phenolic antioxidant with and without a secondary stabilizer was used as reference. The polymer was processed in multiple extrusions, and its functional group content, processability, residual stability, and color were determined by Fourier-transform infrared (FTIR) spectroscopy, melt flow rate (MFR), and oxidation induction time (OIT) measurements as well as by the determination of the yellowness index. The pomegranate peel extract (POM) has very strong melt stabilization effect, which is comparable or better than that of the commercial hindered phenolic antioxidant used as reference. The extract hinders the reactions of the unsaturated groups of the polymer and prevents the formation of long-chain branches. Similar to the phenolic antioxidant, it hinders also oxidation, thus preventing the formation of carbonyl groups. On the other hand, the extract does not offer sufficient residual stability and the polymer stabilized with it cannot be used in long-term applications. The extract discolors the polymer somewhat that further limits its application possibilities. The contradiction of excellent processing stabilization and poor residual stability needs further study and explanation.