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22 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A viscoelastic viscoplastic damage model (VPVD)

This report documents the development, implementation, and parameter estimation procedures for aviscoelastic-viscoplastic-viscodamage model. This model is being developed to improve the predictive accuracy of simulations involving plastic bonded explosives (PBX). A representative PBX is PBX9501, which is 95% by weight HMX, 2.5% estane binder and 2.5% nitroplasticizer. Mechanical deformation of this material is primarily accommodated by straining of the polymer binder and rearranging the relatively rigid HMX crystals.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2022

Aging and Lifetimes Program Annual Report - Part I: Update to BDNPA-BDNPF phase diagram (FY2022)

The eutectic mixture nitroplasticizer (NP) contains water, without exception, on the order of hundreds to thousands of parts per million depending on the exposure conditions. Therefore, to evaluate the properties of NP, one must consider that NP is not simply comprised of two constituents. Here we supplement previous work on the physical properties of NP (Edgar et al., 2020) by expanding on the experimental work therein and addressing inaccuracies detailed in a subsequent comment article (Brown, 2021). Specifically, the purpose of this work is to clarify and modify the phase diagram of the bis(2,2-dinitropropyl) acetal with bis(2,2-dinitropropyl) formal eutectic mixture by considering the effect of water concentrations on the nucleation process.

36 MATERIALS SCIENCE↗
DOE OSTI2020

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

Here, 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 1st 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 1st order) and further degrade NP. The effect of headspace volume on this auto-catalytic process will be discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Comment on the paper “Physical characterization of Bis(2,2-dinitropropyl) acetal and Bis(2,2-dinitropropyl) formal” by Alexander Edgar, Justine Yang, Manuel Chavez, Michelle Yang & Dali Yang

Errors are noted in the construction of the binary phase diagram in the paper “Physical characterization of Bis(2,2-dinitropropyl) acetal and Bis(2,2-dinitropropyl) formal” by Alexander Edgar, Justine Yang, Manuel Chavez, Michelle Yang & Dali Yang. The authors of that paper misinterpret differential scanning calorimetry (DSC) thermal features. All of the DSC data show features consistent with samples that are supercooled during testing. Such samples do not show solidus points and may not show liquidus points, rendering the constructed phase diagram invalid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗