On Modeling the Pyrolysis of Hydroxyl-Terminated Polybutadiene (HTPB) Type R45M at Temperatures in the Range 465‒600 °C

Author(s):

Michael J McQuaid, Chiung-Chu Chen, Christopher Stone, and Jeffrey D Veals

Abstract:

Seeking additional validation of a paradigm for modeling the deflagration of hydroxyl-terminated polybutadiene type R45M that is predicated on the nascent gaseous products of its pyrolysis being represented by 6-ethenyl-2,8,12,16-octadecetetraene (EODT, C₂₀H₃₂), we formulated a model for simulating EODT’s pyrolysis in T-jump experiments performed by Arisawa and Brill (A&B). The model produced results that raised questions concerning A&B’s reduction of their data and some of the conclusions they drew from them. Those findings notwithstanding, the study corroborated A&B’s conclusion that the sum of the mass fractions of products with eight or more carbon atoms would approach or exceed 0.50 under the conditions of the experiments. In addition, simulations were performed to predict the degree to which a subsurface layer EODT would decompose prior to reaching the surface of grains burning in opposed-flow diffusion flame (OFDF) experiments. At the low end of the reported burning rates, less than 15 wt% of the starting mass was decomposed at the surface, and at higher burning rates the percentages were less. As such, they provided further evidence that EODT is more representative of the gaseous products desorbing from the surface of R45M strands burning in OFDF experiments than 1,3-butadiene.