Theoretical and experimental investigations into the pyrolysis mechanisms of silicon-modified phenolic resin under high temperatures

ReaxFF molecular dynamics (ReaxFF-MD) simulations and X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman, Fourier transform infrared spectroscopy (FT-IR), Si-29 NMR were used to investigate the temperature-dependent pyrolysis gas release behavior, dynamic evolution of microstructure, and fundamental carbonization mechanism of silicon-modified phenolic resin (SiPR). An improved and effective algorithm for model building was used to construct the cross-linked SiPR simulation model by considering three reactions in the actual experimental cross-linking process with adjustable occurrence rates. Tracking and analysis of the structures showed that with the continuous release of pyrolysis gas, the residual Si and C-containing components decomposed, rearranged, and aggregated into different phase structures. The Si-units agglomerated and underwent phase separation stages. The carbonization process was divided into three periods: initial aromatization, merging and flattening, and residual healing. These findings may shed light on the polysilicon phase distribution and carbonization mechanism of SiPR.