Evaluating two stages of silicone-containing arylene resin oxidation via experiment and molecular simulation

Abstract

Silicon-containing aryl acetylene resin (PSA) is a new type of high-temperature resistant resin with excellent oxidation resistance, whereas antioxidant reaction mechanism of PSA resin under ultra-high temperatures still remains unclear. Herein, the oxidation behavior and mechanisms of PSA resin are systematically investigated combining kinetic analysis and ReaxFF molecular dynamics (MD) simulations. Thermogravimetric analysis indicates that the oxidation process of PSA resin undergoes two main steps: oxidative weight gain and oxidative degradation. The Distributed Activation Energy Model (DAEM) is employed for describing oxidation processes and the best-fit one is obtained using genetic algorithms and differential evolution. DAEM model demonstrates that the oxidative weight gain stage is dominated by two virtual reactants and the oxidative degradation stage consists of three virtual reactants. Correspondingly, the observation of MD reaction pathways indicates that oxygen oxidation of unsaturated structures occurs in the initial stage, which results in the formation of PSA resin oxides. Furthermore, cracked pieces react with O2 to generate CO and other chemicals in the second step. The resin matrix's great antioxidation resilience is illustrated by the formation of SiO2. The analysis based on MD simulations exhibits an efficient computational proof with the experiments and DAEM methods. Based on the results, a two-stage reaction mechanism is proposed, which provides important theoretical support for the subsequent study of the oxidation behavior of silica-based resins.