Kinetics of HMX and CP Decomposition and Their Extrapolation for Lifetime Assessment

Abstract

Decomposition kinetics are determined for HMX (nitramine octahydro-1,3,5,7tetranitro-1,3,5,7-tetrazocine) and CP (2-(5-cyanotetrazalato) pentaammine cobalt (III) perchlorate) separately and together. For high levels of thermal stress, the two materials decompose faster as a mixture than individually. This effect is observed both in hightemperature thermal analysis experiments and in long-term thermal aging experiments. An Arrhenius plot of the 10% level of HMX decomposition by itself from a diverse set of experiments is linear from 120 to 260 o C, with an apparent activation energy of 165 kJ/mol. Similar but less extensive thermal analysis data for the mixture suggests a slightly lower activation energy for the mixture, and an analogous extrapolation is consistent with the amount of gas observed in the long-term detonator aging experiments, which is about 30 times greater than expected from HMX by itself for 50 months at 100 o C. Even with this acceleration, however, it would take ~10,000 years to achieve 10% decomposition at ~30 o C. Correspondingly, negligible decomposition is predicted by this kinetic model for a few decades aging at temperatures slightly above ambient. This prediction is consistent with additional sealed-tube aging experiments at 100-120 o C, which are estimated to have an effective thermal dose greater than that from decades of exposure to temperatures slightly above ambient.

Thermal Decomposition Kinetics of HMX

“…That would shift the activation energy above its correct value, with a compensating increase in the frequency factor. Comparison of literature values of rate constants and kinetic parameters, leading to the conclusion that a activation energy of ~165 kJ/mol is both consistent with the reaction rate over a wide temperature range [3] (left) but also in the middle (filled square) of those reported in the literature, as compiled by Brill et al [9] (right). Figure 9 shows how the results in this paper fit in with the large body of literature on HMX thermal decomposition kinetics.…”

“…Finally, we show based on an additional comparison to lower temperature decomposition work by Behrens and Bulusu [2] and Burnham et al [3] that the global activation energy for HMX decomposition is probably about 165 kJ/mol for a reaction extent of 10%. Although the activation energies from any particular study may be higher or lower, this activation energy fits data from sealed tube experiments at 120 o C over 5 years to thermal analysis experiment taking a few minutes at temperatures up to 270 o C.…”

“…Figure 9 shows how the results in this paper fit in with the large body of literature on HMX thermal decomposition kinetics. The left-hand figure is adapted from Burnham et al [3], which shows how rate constants at 10% conversion from this work and from lower temperature work by Sandia workers fit on a straight line over six orders of magnitude and indicate an activation energy of ~165 kJ/mol. This is essentially the same energy as determined by nonlinear regression in Figure 8.…”

Caustic-Side Solvent Extraction Chemical and Physical Properties: Equilibrium Modeling of Distribution Behavior

“…While the CTE of RX-55-AE-5 is between the two TATB formulations at -25˚C, its weaker temperature dependence makes its CTE substantially smaller than either LX-17 or PBX 9502 at 75˚C. [16]. TATB compounds are well known for their stability towards heat and are known to decompose at higher temperatures from 370 to 385˚C.…”

Exploring the physical, chemical and thermal characteristics of a new potentially insensitive high explosive RX-55-AE-5

“…Table 7 compares the Small Scale Safety Test (SST) values for RX-55-AE-5, LLM-105, TATB, LX-17 and PBX 9502 that were determined in this work. Thermal decomposition is used to determine the thermal stability of a material with respect to temperature [16]. TATB compounds are well known for their stability towards heat and are known to decompose at temperatures that range from approximately 370˚C to 385˚C when heated at rates of 3˚C per/min.…”