Reactive force field (ReaxFF) molecular dynamics simulation was adopted to study the pyrolysis mechanism of polyurethane/vinyl ester resin (PU/VER) at an atomic level.The reaction systems

containing 1395 atoms

were simulated at various heating rates and temperatures

ranging from 100 K/ps to 500 K/ps and 2800 K to 4800 K respectively.The relevance between the simulation results and the experimental observations was also discussed.In the pyrolysis process

due to the initial dissociation of the PU-modified OO bonds

the branched chains including CN were separated from the main chains.Then the oxygen-bridge bonds in the main chains broke subsequently

which presented the primary cause of vinyl resin main-chain scission.Hence

the consecutive chain reaction would ultimately lead to the de-polymerization of the entire polymer structure.Because of intensive activity of the carbon-carbon double bonds

the vinyl (H2C=CH) at the end of PU/VER main chains was involved in the generation process of the final three dominant products

including hydrogen (H2)

carbon dioxide (CO2) and acetylene (C2H2).Furthermore

the primary products and the corresponding generation paths of PU/VER pyrolysis extracted from the ReaxFF simulations coincided well with the experimental observations.The proposed research demonstrates that

the ReaxFF-based simulation methodology can provide deep insight into the chemical reaction mechanisms in polymer pyrolysis.