Thermochromic photoswitches for localized temperature sensing in hydroxyl-terminated polybutadiene

LT Antron Harper, USN

Abstract: This thesis examines the use of thermally activated photoswitches to analyze localized temperature increase in hydroxyl-terminated polybutadiene (HTPB). HTPB is one of the most widely used polymer binders in US Navy warheads and rocket motors. Currently no method exists to examine the development of temperature localization in HTPB-based formulations. Three thermochromic photoswitches based on a recently developed donor-acceptor Stenhouse adduct (DASA) were synthesized and integrated with HTPB as a means of mapping peak temperatures at the micron scale. A pyroprobe was used to measure the DASA kinetics at heating rates of 20,000 °C per second, comparable to the timescales of heating during high-velocity impact. Photoswitches were found to exhibit zero-order Arrhenius kinetics with activation energies on the order of 10-20 kcal/mol. The photoswitches retain a visible color signature related to the peak temperature of HTPB even after removal from heat. We demonstrate that two DASA variants have sufficiently different activation energies and absorption spectra that their combined use may allow novel post-mortem diagnostics on polymer bonded explosives.

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Jul 07, 2015

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