In this work, models are based on physical experiments in conjunction with computational simulation. Simultaneous thermogravimetric analysis / differential scanning calorimetry (TGA/DSC) gives overall mass loss kinetics based on volatilization rates, while DSC can detect changes that do not release products, such as melting points, glass-point transitions, and chain scission into large fragments. POM homopolymer displayed starkly different degradation patterns with changed heating rates, while copolymer (with extra -CH2- groups) has higher onset degradation temperatures and different decomposition patterns than the homopolymer. A quantitative lumped model is developed and presented.
A valuable complement to the experiments Reactive Molecular Dynamics (RMD), using ReaxFF and LAMMPS to simulate the bond-breaking and physical strains that lead to bond scission. Our previous work has demonstrated that RMD can predict bond-breaking activation energies for high-density polyethylene [1]. Results are presented for POM homopolymer and copolymer with varying chain lengths and different common end groups, including bond-breaking activation energies, pyrolysis products, and mass-loss data from these simulations and comparing them to experimental results. These physical and computational techniques will be used to develop detailed, structure-specific mechanisms for thermal pyrolysis of POM, then for more complex polymeric solid fuels.
[1] K. D. Smith, M. Bruns, S. I. Stoliarov, M. R. Nyden, O. A. Ezekoye, and P. R. Westmoreland, “Assessing the effect of molecular weight on the kinetics of backbone scission reactions in polyethylene using Reactive Molecular Dynamics,” Polymer, vol. 52, no. 14, pp. 3104–3111, Jun. 2011, doi: 10.1016/j.polymer.2011.04.035.
This research was funded by the USDoD/ONR+AFOSR as a Multi-University Research Initiative: Combustion of Solid Fuels in High Enthalpy Flow, award N00014-23-1-2501