Property Estimates for Hydroxyl-Terminated Polybutadiene (HTPB) Type R45M Derived from Atomistic Molecular Dynamics Simulations

Author(s):

Jeffrey D Veals, Chiung-Chu Chen, In-Chul Yeh, Christopher P Stone, Michael J McQuaid, and Claresta Dennis

Abstract:

Seeking to parameterize models for simulating the deflagration of hydroxyl-terminated polybutadiene type R45M, we employed atomistic molecular dynamics (MD) methods to obtain estimates for some of R45M’s transport and thermophysical properties. Estimates for densities, enthalpies of vaporization, and self-diffusion coefficients were derived from simulations of hydroxyl-terminated 6-ethenenyl 2,8,12,16-octadecatetraene (EODT, C₂₀H₃₂) oligomer systems. The dependencies of the predictions on the number of monomers per oligomer (n), system size, simulation temporal duration, and force-field type were evaluated. Comparisons to measured values indicate the predictions’ merit. In addition, we coupled MD-based estimates for the HO–(EODT)ₙ–OH systems’ enthalpies of vaporization with estimates for their gas-phase enthalpies to estimate R45M’s enthalpy of formation and heat capacity as a function of temperature. The enthalpy of formation estimates at 298 K were observed to be in reasonable agreement with a recently published aggregation of such values. Heat capacity estimates were in reasonable agreement with values we measured. The potential to employ the self-diffusion coefficient predictions as a basis for parameterizing a theorized framework for modeling condensed-phase chemical kinetics is discussed.