Initial reaction steps in the condensed-phase decomposition of propellants

Melius, Carl F.; Piqueras, M.C.

doi:10.1016/s1540-7489(02)80350-9

Cited by 24 publications

(35 citation statements)

References 29 publications

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“…The major ions cited are m/z 14, 15, 16, 17, 18, 27, 28, 29, 30, 31, 43, 44, 45 and 46, which are all seen in our experiment except for m/z 14, 17 and 18. We are currently continuing our studies in developing a mechanism and its comparison with theoretical work by Melius and colleagues which suggests possible condensed‐phase initial reaction steps in nitrate ester decomposition 37. The reaction pathway shows consistencies with our findings, and will be more fully addressed in a future publication.…”

Section: Resultssupporting

confidence: 69%

T‐Jump/time‐of‐flight mass spectrometry for time‐resolved analysis of energetic materials

Zhou

Piekiel

Chowdhury

et al. 2008

Rapid Comm Mass Spectrometry

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We describe a new T-Jump/time-of-flight (TOF) mass spectrometer for the time-resolved analysis of rapid pyrolysis chemistry of solids and liquids, with a focus on energetic materials. The instrument employs a thin wire substrate which can be coated with the material of interest, and can be rapidly heated (10(5) K/s). The T-Jump probe is inserted within the extraction region of a linear TOF mass spectrometer, which enables multiple spectra to be obtained during a single reaction event. By monitoring the electrical characteristics of the heated wire, the temperature could also be obtained and correlated to the mass spectra. As examples, we present time-resolved spectra for the ignition of nitrocellulose and RDX. The fidelity of the instrument is demonstrated in the spectra presented which show the temporal formation and decay of several species in both systems. The simultaneous measurement of temperature enables us to extract the ignition temperature and the characteristic reaction time. The time-resolved mass spectra obtained show that these solid energetic material reactions, under a rapid heating rate, can occur on a time scale of milliseconds or less. While the data sampling rate of 10,000 Hz was used in the present experiments, the instrument is capable of a maximum scanning rate of up to approximately 30 kHz. The capability of high-speed time-resolved measurements offers an additional analytical tool for the characterization of the decomposition, ignition, and combustion of energetic materials.

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Section: Resultssupporting

confidence: 69%

T‐Jump/time‐of‐flight mass spectrometry for time‐resolved analysis of energetic materials

Zhou

Piekiel

Chowdhury

et al. 2008

Rapid Comm Mass Spectrometry

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“…From 2012 to 2014, we conducted thermal studies of NP aging over two years in headspaces containing air, nitrogen, or water to study how that headspace composition impacts the reaction pathway of the NP degradation. Those studies experimentally confirmed the mechanisms of NP degradation proposed by several research groups [33][34][35]39]. It is known that the very first step in NP degradation is HONO formation, which then decomposes into NOx, water, or HNOx depending on the temperature and headspace condition.…”

Section: Part Two: Np Thermal Stability In a Confined Systemsupporting

confidence: 76%

“…The stability of various classes of polynitro compounds has been investigated previously. However, relatively few studies have focused on understanding the decomposition pathways of BDNPA/F at temperatures below 70°C [12,18,19,[22][23][24][25][26]. Also, although numerous studies have focused on the aging behavior of the PBX9501 [12,13,16,[27][28][29][30][31][32], few have focused on the NP alone.…”

Section: Part Two: Np Thermal Stability In a Confined Systemmentioning

confidence: 99%

Comprehensive Data Analysis and Analytic Method Development for PBX9501 Material (FY2019 Annual Report of Aging and Lifetimes Program)

Yang

Edgar

Adams

et al. 2020

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In the polymer bonded explosive (PBX) 9501, a binder consisting of 2.5 wt% nitroplasticizer (NP) and 2.5 wt% Estane Ò 5703 (Estane) is combined with 94.9 wt% of the high-explosive HMX and 0.1 wt% stabilizer. Because of its flexibility and tensile strength, this binder lowers the sensitivity and improves the manufacturability of PBX 9501. However, like many plasticizers comprised of low molecular weight components, NP has a tendency to diffuse out of the PBX 9501 matrix and can decompose at moderate temperatures into reactive byproducts, such as NO, NO2, H2O, and HNOx. Through oxidation and hydrolysis, these molecules can further degrade NP and Estane, ultimately degrading the properties of PBX 9501. While gaseous molecules can readily diffuse out of the PBX 9501 charges, the intermediates with lower volatility are more likely trapped in the condensed phase inside the charges and, in a closed system, will co-exist with Estane for an extended period of time creating an ongoing reactive environment. Understanding the rates of formation for these volatiles and intermediates during the NP degradation is therefore a critical prerequisite for understanding the long-term stability of polymeric binders used in munition systems. To work toward this ultimate goal, in the past year, we have conducted comprehensive studies on the physical properties of NP and finished three-year long aging experiment to understand the aging behavior of NP under thermal treatment. Important results are summarized in this annual report. Although NP is widely used in the DOE complex, their physical properties are rather scattered and inconsistent in the open literature. For example, there are at least two widely different values, 14.5°C and-15°C, for the melting point of NP. Although it is known that NP is a eutectic 50:50 mixture of BDNPA and BDNPF, their eutectic phase diagram is not well documented. Furthermore, the effect of temperature on the miscibility between water and eutectic BDNPA/F mixture is rarely reported. To fill these knowledge gaps, a large set of BDNPA/F mixtures with BDNPA concentration ranging from 0 to 100 wt% was analyzed using DSC techniques. In addition to determining the eutectic melt point as-25°C, a phase diagram of the BDNPA/F system was constructed from-30°C to 45°C. With this phase diagram, the phase transition temperatures and composition can be readily found for the BDNPA/F mixtures with various mass ratios. The results are summarized in Part One. During PBX 9501 production and its late characterization, the material is often directly in contact with water. While extensive characterization has been conducted on aged PBX 9501 as a whole, how NP degrades in direct contact with water has been rarely reported, therefore NP was aged in direct contact with water molecules in this study. To study the miscibility between NP and water, a large set of NP/water samples with water concentration ranging from 500 to 5800 ppm was fully characterized using coulometric Karl Fischer (KF) titration, TGA, DSC, and Near-IR Spectrosco...

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“…This is consistent with earlier findings for the decomposition of methylnitramine, a prototype material of nitramines. 7,14 An extension of the equatorial NÀNO 2 bond also leads to the bond breaking. However, due to a small attraction between the C 4 H 8 N 7 O 6 radical and the NO 2 , the structural relaxation causes the NO 2 to rebind with the rest of the molecule.…”

Section: Decomposition Mechanismsmentioning

confidence: 99%

Modeling Thermal Decomposition Mechanisms in Gaseous and Crystalline Molecular Materials: Application to β-HMX

Sharia

Kuklja

2011

J. Phys. Chem. B

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Exploration of initiation of chemistry in materials is especially challenging when several coexisting chemical mechanisms are possible and many reactions' products are produced. It is even more difficult for complex materials, such as molecular, supramolecular, and hierarchical materials and systems. A strategy to draw a complete picture of the earliest stages of rapid decomposition reactions in molecular materials is presented in this study. The strategy is based on theoretical and computational modeling of chemical decomposition reactions in the gaseous and crystalline molecular material that has been performed by means of combined density functional theory and transition state theory. This study reveals how a crystalline field affects materials chemical degradation. We also demonstrate how incomplete results, which are often used due to difficulties in obtaining comprehensive data, can lead to erroneous conclusions and predictions. We discuss our approach in the context of the obtained reaction energies, activation barriers, structures of transition states, and reaction rates with the example of a representative molecular material, β-HMX, which tends to decompose violently with large energy release upon an external perturbation. The performed analysis helps to provide a consistent interpretation of available experimental data. The article illustrates that the complete picture of decomposition reactions of complex molecular materials, while theoretically challenging and computationally demanding, is possible and even practical at this point in time.

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Initial reaction steps in the condensed-phase decomposition of propellants

Abstract: Word count: 5420 = 3250 words + 420 (eqn) + 350 (ref) + 1 table (400) + 5 figures (1 000

Cited by 24 publications

References 29 publications

T‐Jump/time‐of‐flight mass spectrometry for time‐resolved analysis of energetic materials

T‐Jump/time‐of‐flight mass spectrometry for time‐resolved analysis of energetic materials

Comprehensive Data Analysis and Analytic Method Development for PBX9501 Material (FY2019 Annual Report of Aging and Lifetimes Program)

Modeling Thermal Decomposition Mechanisms in Gaseous and Crystalline Molecular Materials: Application to β-HMX

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