Short timescale high temperature pyrolysis products of hydroxyl-terminated polybutadiene

Pyrolysis of hydroxyl-terminated polybutadiene was previously studied at temperatures up to 850 degrees C, in some cases at heating rates approaching 103 degrees C/s. The temperatures are relevant to rocket motor conditions but the heating rates likely fall short, even at the highest values previously achieved. Using pulsed laser surface heating to effect pyrolysis, we have been able to detect pyrolytic products at roughly comparable temperatures but with much more rapid heating timescales, approaching-106 degrees C/s. Unlike earlier results obtained in the 800-850 degrees C range, where benzene and toluene were detected as substantial products, we detected little or none. By contrast, several mechanistically important radical species were observed; they process further in time, stabilized by both hydrogenation and dehydrogenation. Furthermore, hydrocarbon species containing three carbon atoms were abundant compared to prior studies, at the expense of higher-MW products, particularly 4-vinylcyclohexane. Evidence for rapid feedstock deoxygenation was obtained. Differences from prior results likely are due pri-marily to higher heating rates, resulting in short reaction times. Our ability to detect radical species helps to facilitate nuanced mechanistic schemes to explain the results, starting from the onset of pyrolysis.