Abstract
In this thesis, a novel method for simulating the complete pyrolysis and charring process of phenol-formaldehyde resins using reactive molecular dynamics and targeted pyrolysis product removal was demonstrated. This method was able to produce fully carbonised structures within 2 ns of simulation time (where 6 ns simulations without product removal showed no significant formation of carbon clusters). Simulated pyrolysis was carried out on a series of models of phenol-formaldehyde resin, a polymer used in spacecraft ablative thermal protection systems. Pyrolysis was carried out at 1500 K, 2500 K and 3500 K using a hydrocarbon oxidation parameter set for the ReaxFF forcefield. The reactions occurring during the thermal decomposition of the polymer structures were investigated using detailed atomic trajectories and connectivity data, allowing elucidation of the mechanisms of pyrolysis and thermal decomposition at the atomic scale. The evolution of the structure of the resin and char during pyrolysis was reported and the effects of structure size, degree of cure, and curing algorithm were quantified. Six major stages of phenol-formaldehyde resin pyrolysis were highlighted. Predictions of elastic moduli, specific heat capacities and thermal conductivities of phenol- formaldehyde resin (and the chars obtained from pyrolysis) were also made using various simulation techniques.