Experimental Study of the Oxidative Degradation of PBX 9501 and its Components

Abstract

The results of the constituent aging study (CAS) are given, where low‐temperature (T<64 °C) aging experiments were performed on over 1100 closed‐container samples of various combinations of the components of the plastic‐bonded explosive PBX 9501. Experiments were performed on the various combinations both in the absence and presence of free‐radical stabilizers. The product gases were identified and quantified as a function of aging time. The gas data show diverse chemistry between CAS samples and initial linear increases in product gas formation. Temperature analysis of the initial production rates of gas products shows straight Arrhenius plots. The extracted activation energies and frequency factors for the formation of the individual gas products yield a single linear kinetic compensation plot suggesting a common degradation pathway for PBX 9501 and combinations of constituents that contained nitroplasticizer (a eutectic mixture of bis‐2,2‐dintropropyl acetal and bis‐2,2‐dintropropyl formal).

Thermal stability of a eutectic mixture of bis(2,2-dinitropropyl) acetal and formal: Part A. Degradation mechanisms in air and under nitrogen atmosphere

“…[14] In closed-drum storage at ambient temperature, the chemical purity of BDNPA/F has been tested periodically to ensure it remained within material specifications. [14,15,27,28] Once received, the NP container was stored in a refrigerator at 4 °C. Since this NP sample was used as a starting material, we designate it as a baseline sample, but recognize its age.…”

“…Although thermal stabilities were investigated for various classes of polynitro compounds, relatively few studies focused on the understanding of the decomposition pathways of BDNPA/F [11][12][13][14] and the effects of their aging at temperatures below 70 °C. [15][16][17][18] Of those studies, the most extensive one is a constituent aging study (CAS) of over 1100 samples comprised of various combinations of the components used in the PBX 9501 formula, performed at temperatures below 64 °C. [15] One of the goals of that work was to study the correlation between the chemical degradation of PBX 9501 and the amount and type of gases evolved in the aging process of PBX 9501.…”

“…[15][16][17][18] Of those studies, the most extensive one is a constituent aging study (CAS) of over 1100 samples comprised of various combinations of the components used in the PBX 9501 formula, performed at temperatures below 64 °C. [15] One of the goals of that work was to study the correlation between the chemical degradation of PBX 9501 and the amount and type of gases evolved in the aging process of PBX 9501. For the samples containing no NP, which showed high stability, the GC-mass spectroscopy analysis revealed low concentration of the evolved gases.…”

“…[4,[15][16][17][18][19][20][21][22] One of the limitations of the CAS study was that the changes in the compositions of the condensed phase materials were not evaluated. [15] Furthermore, the CAS study and similar aging experiments focused on global properties of the composite, rather than its components, making it difficult to evaluate the stability, mechanism, and kinetics of decomposition of the NP itself. Other studies investigated the thermal stability of BDNPA/F mixture, but were conducted at relative high temperatures (>150 °C).…”

Diffusion and sorption of nitroplasticizers in vinyl copolymer elastomer and its composites

“…In the BDNPA/F form, its boiling point, melting point and density are 150°C, −15°C, and 1.383–1.397 g cm −3 , respectively . NP is commonly used in polymer‐bonded explosive (PBX) and gun propellant formulations . One problem with the plasticizers is that they are generally low molecular weight chemicals and have a tendency to migrate from one material to another.…”