Thermal Stability of a Eutectic Mixture of Bis(2,2‐dinitropropyl) Acetal and Formal: Part C. Kinetic Compensation Effect

Abstract

The aging behavior of a eutectic mixture of bis (2,2-dinitropropyl) acetal and formal [called NP here] has been studied in various atmospheres [dry (air or nitrogen) versus wet] at temperatures 70°C and below. The properties of aged samples were analyzed using Fourier transform infrared (FTIR) spectroscopy, Karl Fischer (KF) titration, liquid chromatography/mass spectrometry (LC/MS), and thermogravimetric analysis (TGA) over a period of three years. The results indicate that at aging temperatures up to 55°C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO 2 follows a 1 st order rate law and the rate constants follow an Arrhenius law as a function of temperature. The activation energies and pre-factors for water and volatiles production yield a single linear kinetic compensation plot, suggesting a common degradation pathway between NP and the various combinations of its constituents. Within a narrow temperature range, around 55°C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55°C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NO x , water, and HNO 3 serve as catalysts to auto-catalyze (kinetics beyond the 1 st order) and further degrade NP. The effect of headspace volume on this auto-catalytic process will be discussed.

Liquid Chromatography Mass Spectrometry Study of a Eutectic Mixture of bis(2,2‐Dinitropropyl) Acetal/Formal

“…A stock of BDNPA and BDNPF, synthesized via the ter Meer process as described by Rindone et al 2000, and stored at Los Alamos National Laboratory was used as source material for the NP samples [11,15]. Aged NP samples were obtained from previous long term aging studies [9][10][11]15]. The aged samples were thermally treated for up to 44 months under four isothermal conditions (38 °C, 45 °C, 55 °C, and 64 °C).…”

“…Together with an approximately equal mass to NP, they act as a binder in the formulation of some PBX materials. There have been numerous studies on the thermal stability of NP, which have stimulated further examination of the materials used in these explosive systems [1][2][3][4][5][6][7][8][9][10][11]. In this ongoing study, a set of aged NP samples are characterized using several techniques, including mass spectrometry (MS) [8][9][10][11][12].…”

“…There have been numerous studies on the thermal stability of NP, which have stimulated further examination of the materials used in these explosive systems [1][2][3][4][5][6][7][8][9][10][11]. In this ongoing study, a set of aged NP samples are characterized using several techniques, including mass spectrometry (MS) [8][9][10][11][12]. Among these results, the thermal and chemical characterizations reveal environmental conditions significantly alter the aging behavior of NP; and also suggest the first step in NP degradation is likely occurring through À CÀ NÀ cleavage to form nitrous acid (HONO), followed by water and NO x generation.…”

“…Among these results, the thermal and chemical characterizations reveal environmental conditions significantly alter the aging behavior of NP; and also suggest the first step in NP degradation is likely occurring through À CÀ NÀ cleavage to form nitrous acid (HONO), followed by water and NO x generation. The combination of HONO formation followed by its decomposition is called HONO elimination [9][10]. In previous MS work, a Waters® Micromass® ZQ™ single quadruple mass spectrometer was used without an HPLC column.…”

“…However, no open literature was found detailing an analysis methodology for this instrumentation to study NP. NP degradation can be very complex and many products are highly reactive [8][9][10]. Whereas to conduct full characterization, while not introducing erroneous signals during LC-QTOF analysis, an optimized methodology has to be developed.…”