The synergistic mechanism of thermally reduced graphene oxide and antioxidant in improving the thermo-oxidative stability of polypropylene

The feasibility of using thermally reduced graphene oxide (TrGO) to improve the antioxidative efficiency of commercial antioxidant (3,5-di-tert-butyl-4-hydroxycinnamic acid, AO) on unstabilized polypropylene (PP) was evaluated in terms of the oxidation induction time (OIT) and the initial degradation temperature (T_i). It was found that a synergistic effect exist between AO and TrGO in retarding the degradation of PP in oxygen-containing atmosphere. Compared with that of PP/AO (100/0.5) sample, the OIT value of PP/AO/TrGO (100/0.5/1) composite was almost doubled at 180 °C and the value of T_i in air was improved by 37.2 °C. As verified by using radical scavenging assay with the 1,1-diphenyl-2-picrylhydrazyl radical, the TrGO sheets exhibited a good radical scavenging capacity. The synergistic stabilization mechanism was attributed to the enhanced dispersion of TrGO sheets in the PP matrix in the presence of 0.5 wt.% AO, which could improve the oxygen barrier effect and radical scavenging efficiency of TrGO. This synergistic effect between AO and TrGO can efficiently reduce the concentrations of oxygen and peroxy radicals in the PP matrix, leading to the significant improvement in thermo-oxidative stability of PP/AO/TrG composite.