Assessing pyrolysis behavior of silicon-containing arylacetylene resin via experiments and ReaxFF MD simulations

Silicon-containing arylacetylene resin (PSA), a thermosetting organic-inorganic hybrid resin of high heat-resistance performs well in ablation process, whereas its pyrolysis behavior under high temperature has not been fully interpreted. Herein, the PSA pyrolysis process was in-depth investigated by experiments and ReaxFF molecular dynamics simulation (ReaxFF-MD). TG results show that the temperature of 5% weight loss (Td5) is above 600 ℃, and the residue at 900 ℃ surpass 85%, demonstrating PSA has excellent heat resistance and thermal stability. The on-line FTIR and out-line gas quantify analysis reveals that H2 and CH4 are dominant gaseous products, which are also unveiled by ReaxFF-MD simulation. Molecular reaction tracking indicates PSA pyrolysis is initiated by the cleavage of skeleton in benzene ring, the cleavage of C-C bond and C-Si bond in main chain at elevated temperature. Hydrogen abstraction reactions are primary formation pathways of CH4 and H2, together with conquering high energy barriers. The activation energy of PSA pyrolysis in experiments is 155 kJ/mol, agreeing well with that from ReaxFF MD simulations (144 kJ/mol), which further confirms the thermochemical stability of cured PSA that rich in highly crosslinked aromatic structure. Besides, the influence of silicon side-groups on PSA pyrolysis is screened by MD and results indicate that gases evolution depended largely on side-groups types and decreasing side phenyl groups in PSA is benefit for improving its thermal stability. This work deepens the understanding of PSA pyrolysis mechanism and provides theoretical guidance for improving its heat resistance. ●The pyrolysis behavior of silicon-containing arylacetylene resin is studied.●The initial degradation pathway of material and formation mechanism of pyrolysis products were investigated.●The activation energy extracted from simulations is in good agreement with experiment results.●The effect of silicon side-groups on silicon-containing arylacetylene resin pyrolysis were discussed.