ReaxFF-based Reactive Molecular Dynamics Simulation of Pyrolysis of Polyurethane/Vinyl Ester Resin Used for Wind Turbine Blades

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 O-O bonds, the branched chains including C-N 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 (H-2), 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.