The thermal decomposition of polyphenolic resins was studied by reactive molecular dynamics (RMD) simulation at elevated temperatures. Atomistic models of the polyphenolic resins to be used in the RMD were constructed using an automatic method which calls routines from the software package Materials Studio. In order to validate the models, simulated densities and heat capacities were compared with experimental values. The most suitable combination of force field and thermostat for this system was the Forcite force field with the Nosé-Hoover thermostat, which gave values of heat capacity closest to those of the experimental values. Simulated densities approached a final density of 1.05-1.08 g/cm 3 which compared favorably with the experimental values of 1.16-1.21 g/cm 3 for phenol-formaldehyde resins. The RMD calculations were run using LAMMPS software at temperatures of 1250 K and 3000 K using the ReaxFF force field and employing an in-house routine for removal of products of condensation. The species produced during RMD correlated with those found experimentally for polyphenolic systems and rearrangements to form cyclopropane moieties were observed. At the end of the RMD simulations a glassy carbon char resulted. mixtures were also investigated by van Duin [13]. A new force field was derived for Pt-O systems by Fantauzzi et al. [14], and an organic mechanistic study was carried out on polymerization by Schoenfelder [15]. Adaptive accelerated RMD on hydrogen was published by Goddard et al. [16], and an implementation of RMD on GPU's was developed by Kylasa et al. [17]. The second generation of RMD methods were reviewed by Farah et al. in 2012 [18], which used empirical reactive force fields to generate the new species. Recently, a transferable reactive force field was developed by Xiao, Shi, Hao, Liao, Zhang, and Chen for phosphorous and hydrogen which showed a distinct improvement in predicting the mechanical properties of pristine-and defect-laden black phosphorous [19]. In this study we concentrate on phenol-formaldehyde resins (PFRs), also known as phenolic resins, which are a subclass of synthetically derived thermosetting polymers obtained from a reaction of phenol with formaldehyde ( Figure 1).