Recent progress in aging studies of a eutectic mixture of bis(2,2-dinitropropyl) acetal and formal nitroplasticizer
A critical review is given for our past 10 years of research on the thermal degradation of a eutectic mixture of bis(2,2-dinitropropyl) acetal and formal (BDNPA/F), known as nitroplasticizer (NP). Additional experimental and theoretical studies presented here thoroughly investigate the degradation mechanisms of NP as it thermally aged over several years. On the experimental front, a 44-month long experiment was conducted under various aging conditions. To further probe reaction pathways that initiate NP degradation, a 5-month aging experiment was also added. The aged NP samples were fully analyzed using FTIR and NMR spectroscopy, KF titration, TGA, LC-QTOF mass spectrometry, and IC. These results show that NP degradation occurs in two major stages. In the low acidity early stage, HONO elimination followed by decomposition is a key degradation mechanism and leads to the formation of small molecules (e.g., NO, NO+, NO2, NO2+, H2O, N2O, NO3-, H3O+, HNOx) and NP residuals. While HONO, NOx and NO2+ are scavenged by N-phenyl-2-naphthylamine (PBNA) through an initial nitrosation followed by sequential nitration reactions, water accumulates and acidity increases. In the later stage, acid-catalyzed hydrolysis dominates to produce 2,2-dinitropropanol (DNPOH), organic acids, aldehydes, hydrolyzed products of PBNA, and other products. Theoretical calculations using density functional theory (DFT) performed on full molecules of BDNPA/F show that HONO elimination is more energetically favorable than NO2 homolysis and NP hydrolysis and is the initial step in NP degradation under neutral environment and at moderate temperatures. DFT calculations also show that the energetics of NP hydrolysis strongly depend on the polarity of the local environment as well as the proton concentration. In-depth analyses of FTIR data and LC-QTOF data confirm the presence of NO2+ and hydrolyzed products of PBNA in the proposed stages of NP aging. Finally, time-temperature superposition (TTS) analysis was applied to the concentration profiles of dinitro-/trinitro-PBNA and DNPOH species over aging time under various conditions; and the lifetimes of NP stability are predicted accordingly.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 2202510
- Alternate ID(s):
- OSTI ID: 2203403
- Report Number(s):
- LA-UR-23-20852; S0141391023003154; 110565; PII: S0141391023003154
- Journal Information:
- Polymer Degradation and Stability, Journal Name: Polymer Degradation and Stability Vol. 218 Journal Issue: C; ISSN 0141-3910
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United Kingdom
- Language:
- English
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