A semi-detailed chemical kinetic model of polybutadiene pyrolysis

Polybutadiene (PB) is an important polymer with various applications including next-generation solid fuel propellants. Understanding its pyrolysis behavior under various conditions is essential for tuning to these applications. In this study, pyrolysis of polybutadiene with a well-defined 20 % vinyl and 80 % cis + trans composition is investigated using thermogravimetric analysis at heating rates from 10 °C min−1 to 100 °C min−1. Gas speciation was measured via py-GC/MS to identify and quantify products. The CRECK condensed-phase kinetics framework for polymer pyrolysis is extended to predict decomposition mechanisms and product distributions of PB. The model incorporates 50 species and 415 reactions. Experimental results reveal two distinct decomposition steps occurring at 350 °C and 475 °C across all investigated heating rates, responsible for 5 wt% and 95 wt% loss, respectively. The model reproduces mass loss profiles to within 6 wt% accuracy, though early decomposition stages show deviations attributed to the exclusion of cis–trans isomerization reactions. An important result is the primary production of 4-vinylcyclohexene from 0 to 5 % mass loss, butadiene after 5 % mass loss, followed by dimers and trimers respectively in order of net rates of production of gas phase species. Predictions of chemical product speciation capture the butadiene to 4-vinylcyclohexene ratio, and the butadiene to five-carbon cyclic species ratio from an average of literature sources to within 55 % and 37 % respectively. This work provides new, high-quality experimental data, including the measurement of 34 gaseous products, and an extended kinetic framework, advancing the understanding of PB thermal degradation and supporting its application in thermal recycling and advanced energetic materials.