A Dual Analytical Approach Using Evolved Gas Analysis and Pyrolysis-GC-MS to Separate and Identify PAHs Generated during Neat HTPB Pyrolysis

This study employs a dual analytical approach to separate and identify the polycyclic aromatic hydrocarbons (PAHs) generated from the thermal decomposition of hydroxyl-terminated polybutadiene (HTPB), a common propellant binder. Our methodology combines a temperature-resolved gas evolution technique with a true chromatographic separation method. First, Evolved Gas Analysis (EGA) was utilized to resolve the gas evolution based on temperature, providing a time- and temperature-dependent profile of PAH formation. This non-chromatographic approach demonstrated that PAH production begins within 15 seconds of heating and that the temperature profile is a key determinant: lower temperatures lead to the evolution of smaller aromatic molecules, while higher temperatures favor heavier PAHs.

Subsequently, Pyrolysis–Gas Chromatography–Mass Spectrometry (Pyr-GC-MS) was employed to perform the definitive chromatographic separation and structural identification of the evolved products. The high-resolution GC column provided a detailed product distribution, identifying naphthalene and indene as key intermediates and confirming the dominance of hydrogen-atom-assisted cyclization and aromatization (HACA) mechanisms.

By combining the temperature-resolved data from EGA with the detailed chromatographic separation of Pyr-GC-MS, this research provides a comprehensive and unambiguous understanding of PAH generation pathways. These findings underscore how both temperature profile and residence time govern the thermal decomposition process and the resulting product distribution, showcasing the power of a combined separation and resolution approach in complex chemical analysis.