Thermal Analysis of Improvised Energetic Chemicals using Laser-Heating Calorimetry
Ashot Nazarian, Cary Presser
Thermal analysis of six improvised energetic chemicals was carried out using laser-heating calorimetry to demonstrate the feasibility of this methodology to provide distinctive thermal signatures and information on the material shelf life. The chemicals evaluated were triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD), urea nitrate, erythritol tetranitrate, R-salt, and poor-man's C-4. The measurement technique records the temperature rise with time, from which one can estimate the material endothermic/exothermic behavior, energy release rate, and total energy release (enthalpy of explosion), as well as the sample mass rate of change. Measurements were carried out in an inert nitrogen environment at laser heating rates up to 60 K/s with steady-state temperatures reaching 1100 K. Sample initial mass was between 1.0 mg and 9.0 mg. Experiments were carried out with freshly prepared samples, as well as refrigerated samples and those stored at room temperature for three years. Results indicated that the samples reacted rapidly between 0.5 s and 0.75 s, being initiated near the material decomposition/detonation-point temperature. The total energy release was calculated and compared to the values available in the literature. It was found that the thermal signatures (temperature-time derivatives with temperature) were different for each chemical, indicating that this laser-heating calorimetry technique can distinguish one chemical from another. Also, the shelf life for TATP and HMTD was found not to loss potency after three years (contrary to the literature), and larger initial sample masses facilitated initiation of chemical reactions.
calorimetry, energetic materials, homemade/improvised explosives, laser-driven thermal reactor, thermal signatures, total specific energy release