Synergistic effects of antioxidant and silica on enhancing thermo-oxidative resistance of natural rubber: Insights from experiments and molecular simulations

Abstract

In this work, the thermo-oxidative aging performance of antioxidant N-isopropyl-N′-phenyl-p-phenylenediamine (4010NA)/silica (SiO2)/natural rubber (NR) composite was evaluated by the variations of mechanical properties and chemical structure after aging at 100 °C. Compared with 4010NA/carbon black (CB)/NR composite, there existed significant synergistic effects between 4010NA and SiO2 on improving the thermo-oxidative stability of NR material. Then, by combining the results of experiments and molecular simulations, the synergistic stabilization mechanism in 4010NA/SiO2/NR composite could be attributed to the following comprehensive effects. Firstly, the incorporation of silica was capable of improving oxygen (O2) barrier ability of NR and inhibiting the migration of 4010NA. Secondly, antioxidant 4010NA could be prior to terminate peroxy radicals, and its addition enabled 4010NA/SiO2/NR composite to be of an appropriately high cross-linking density due to a vulcanization accelerated effect. As a result, 4010NA/SiO2/NR composite exhibited more preeminent mechanical properties than 4010NA/NR and 4010NA/CB/NR composites during the thermo-oxidative aging process. This means that the combination of 4010NA and SiO2 can be exploited to prepare high performance NR composite with a facile operation. Furthermore, molecular simulation, as a theoretical method, may contribute to our understanding about structure-properties relationship for NR composite in depth. Keywords: Natural rubber (NR) aging, Silica, Antioxidant, Synergistic effect, Molecular simulation