Physical characterization of Bis(2,2-dinitropropyl) acetal and Bis(2,2-dinitropropyl) formal

Propellants Explo Pyrotec

Torres

et al. 2020

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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.

Section: Resultssupporting

confidence: 91%

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

Propellants Explo Pyrotec

Torres

et al. 2020

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“…To resolve these discrepancies, the Tms of the eutectic BDNPA/F mixtures and the phase diagram of the BDNPA/F system were carefully determined. Since the detailed description of this work is given in one of our recent manuscripts [8], only the brief description of their physical properties is given below.…”

Section: Part One: Comprehensive Characterization Of Nitroplasticizermentioning

confidence: 99%

“…With this phase diagram, the phase transition temperatures and composition can be readily found for the BDNPA/F system with various mass ratios. The detailed description on how this phase diagram was constructed can be found in reference [8].…”

Section: Heat Fusion Of Bdnpa and Bdnpfmentioning

confidence: 99%

“…As water sorption in both HMX and Estane have been studied previously [17], this study focuses on the miscibility of water in NP and water solubility in NP, specifically in constructing the NP rich NP-water phase diagram. Again, since the detailed description how to construct this phase diagram is given in one of our recent manuscripts [8], only the phase diagram of NP and water is presented below. From the phase diagram of NP and water mixtures, it was found the miscibility between NP and water changes significantly with temperature and mixing conditions.…”

Section: The Phase Diagram Of Np and Np Rich-water Mixturementioning

confidence: 99%

“…Using a set of NP/water standard solutions with pre-determined water concentrations, we constructed a calibration curve relating the areas of the water peaks in the NIR spectra to the water concentrations. The detailed description of construction of this calibration curve has been described in our earlier manuscripts elsewhere [8,37]. This calibration curve, as shown in an inset in Fig.…”

Section: Nir Spectroscopymentioning

confidence: 99%

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

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...

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

Wong

Propellants Explo Pyrotec

2021

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This study is the first attempt to document methodology development undergone using liquid chromatography tandem quadrupole time of flight mass spectrometry (LC-QTOF) to investigate degradation products of eutectic bis(2,2-dinitropropyl) acetal/formal nitroplasticizer (called NP here). Method properties investigated are: desolvation temperature (°C) and spray voltage (V) of the electrospray ionization source, and the development of an acetone system rinse to prevent any residual contamination between sample injections. Details are given on why it is essential to investigate method optimization with changes shown in MS/MS analysis in addition to MS results. Trends in MS/MS analytic results reveal important relationships between baseline and aged materials. In addition to verification of previously proposed fragments, insights offered by this newly developed methodology will also identify new degradation products and shed light on the complexity of NP degradation chemistry.