Insight into pyrolysis behavior of silicone-phenolic hybrid aerogel through thermal kinetic analysis and ReaxFF MD simulations

Phenolic aerogel matrix nanocomposites are modified to improve their thermal stability and oxidation resistance, while the pyrolysis behavior will become more complex. Herein, the pyrolysis behavior of silicone-phenolic hybrid aerogel, as the pyrolyzable component of the nanocomposites, was investigated by thermal analysis ex-periments (TG-MS, TG-FTIR, and Py-GC/MS), kinetic studies (isoconversional methods and distributed activation energy model (DAEM)), and reactive force field molecular dynamics (ReaxFF MD) simulations. Experimentally, it was found that the main product of silicone-phenolic hybrid aerogel during the first decomposition stage is CH4, which was also validated by ReaxFF MD simulation. The main product CH4 was predominantly formed by hydrogen extraction reaction from silicone aerogel. The main decomposition products and pyrolysis kinetics of silicone-phenolic hybrid aerogel were analyzed by a combination of the multi-DAEM and ReaxFF MD simula-tions. The five-pseudo-components DAEM was utilized to reveal the decomposition of silicone-phenolic hybrid aerogel in five stages, which were in good agreement with the experimental conversion rates. The rearrangement of the Si-O-Si backbone of silicone aerogel at elevated temperatures forms silica-like species with antioxidant performance. This study can provide reliable guidance for the characterization and design of phenolic aerogel matrix nanocomposites and the selection of antioxidant modifiers.

Automated summary

In this study, the pyrolysis behavior of silicone-phenolic hybrid aerogel was investigated using experimental and simulation methods. It was found that CH4 was the main product during the first decomposition stage of the aerogel. The study also revealed the mechanism of structural rearrangement and formation of antioxidant species in the aerogel at elevated temperatures. These findings provide valuable insights for improving the thermal stability and oxidation resistance of phenolic aerogel matrix nanocomposites.