Antioxidant behavior of a novel sulfur-bearing hindered phenolic antioxidant with a high molecular weight in polypropylene

A novel sulfur-bearing hindered phenolic antioxidant with a molecular weight of 1305.9 (SAO) was successfully synthesized via thiol-acrylate Michael addition reaction and its structure was clarified by nuclear magnetic resonance (NMR) and fourier transform infrared spectra (FTIR). The short-term oxidation induction time (OIT) of polypropylene (PP) compounds obtained at 210 °C showed that the OIT value of SAO-containing PP was higher than that of PP using Chinox 1035 with a molecular weight of 642.9 as a stabilizer. Long-term accelerated thermal aging test of PP compounds in an air oven at 150 °C, however, exhibited that the aging resistance of SAO-stabilizing PP was inferior to that of 1035-containing PP, quite contrary to their respective short-term effect on PP stabilization. The possible reasons of this contradiction were discussed from the viewpoint of the antioxidants' molecular structure and the limitations of the OIT approach in lifetime prediction.