Microsecond-scale molecular dynamics simulation of phenolic resin precursor pyrolysis at realistic temperatures

Understanding pyrolysis of phenolic resin is key for predicting the material response of phenol-based thermal protection systems (TPS), such as the Phenolic Impregnated Carbon Ablator (PICA). Experiments provide data at realistic reentry conditions but lack microscopic insight, while Molecular Dynamics (MD) studies provide microscopic insight but only up to a few nanoseconds, typically at unrealistically high temperatures. To address this problem, we present the first Accelerated Molecular Dynamics study of the pyrolysis of a phenolic resin precursor molecule using Parallel Replica Dynamics (PRD). We build and validate a PRD framework applicable to the study of small phenolic resin systems and achieve timescales of several microseconds at temperatures as low as 1600 K, representing a 1000-fold increase in simulation time compared to past MD studies at comparable conditions. Our simulations reveal that phenolic resin undergoes intense competition between carbon dissociation and formation reactions, occasionally entering kinetic traps. These processes ultimately lead to planar graphene-like structures similar to Basic Structural Units (BSU), the fundamental building blocks driving graphitization of bulk phenolic resin. We extract Arrhenius parameters for eight distinct reaction classes, identify the dominant role of hydrogen transfer at lower temperatures, and demonstrate that C–C bond formation becomes increasingly competitive with decomposition below 2000 K. These findings provide a microscopic foundation for developing next-generation pyrolysis models for thermal protection materials.