RDX solubility in TNT at high temperatures
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RDX solubility in TNT at high temperatures Michael L. Hobbs1 · Michael J. Kaneshige2 · Steven N. Todd3 · Thomas R. Krawietz4 Received: 24 July 2019 / Accepted: 13 October 2019 © This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2019
Abstract The solubility of RDX (hexahydro-1,3,5-tri-nitro-1,3,5-triazine) in TNT (2,4,6-trinitrotoluene) at elevated temperatures is required to accurately predict the response of Comp-B3 (60:40 RDX:TNT) during accidents involving fire. As the temperature increases, the TNT component melts, the RDX partially dissolves in the liquid TNT, and the remaining RDX melts (203 ◦ C) as the Comp-B thermally ignites. In the current work, we used a differential scanning calorimeter (DSC) to estimate the solubility of RDX in TNT at the melting point of RDX. Most DSC measurements of Comp-B3 do not show an RDX melt endotherm. The absence of an endotherm associated with the RDX melt has been interpreted as RDX being completely dissolved in TNT before reaching the melting point. We have observed that the endotherm is not absent, but is masked by exothermic reactions occurring at these elevated temperatures. We have inhibited the exothermic reactions by venting our DSC samples and measuring the RDX melt endotherm in our Comp-B3 samples at about 203 ◦ C. Using the measured heat flow associated with the RDX melt and the latent melting enthalpy of RDX, we have approximated the solubility of RDX in TNT to be roughly 50–100 gRDX per 100 gTNT . The broad range is based on corrections for exothermic reactions occurring as the RDX melts. Keywords TG/DSC · RDX · TNT · Comp-B3 · Solubility · Cookoff
Introduction
* Michael L. Hobbs [email protected] Michael J. Kaneshige [email protected] Steven N. Todd [email protected] Thomas R. Krawietz [email protected] 1
Engineering Sciences Center, Sandia National Laboratories, P. O. Box 5800 MS‑0836, Albuquerque, NM 87185, USA
2
Component Science, Engineering, and Production, Sandia National Laboratories, P. O. Box 5800 MS‑1454, Albuquerque, NM 87185, USA
3
Energetic Systems Research Department, Sandia National Laboratories, P. O. Box 5800 MS‑1134, Albuquerque, NM 87185, USA
4
Munitions Directorate, Ordnance Division, Energetic Materials Branch, Air Force Research Laboratory, 101 West Eglin Boulevard, Eglin AFB, FL 32542, USA
Understanding the solubility of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) in TNT (2,4,6-trinitrotoluene) is required for safety analysis of heated Comp-B, which is a melt-castable explosive nominally composed of 63/36/1 by mass of RDX, TNT, and wax. The wax is used as a desensitizing agent and does not influence cookoff behavior. A slightly modified composition known as Comp-B3 has a nominal composition of 60/40 RDX/TNT. We have performed several TG–DSC (thermogravimetric and differential scanning calorimeter) and PDSC (pressurized DSC) experiments using purified TNT, purified RDX, and a mixture of 60:40 RDX:TNT (Comp-B3) made using our purified TN
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