Journal
PROPELLANTS EXPLOSIVES PYROTECHNICS
Volume 34, Issue 5, Pages 406-414Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/prep.200800031
Keywords
Kel-F 800; LX-17; Ratchet Growth; TATB; Temperature Cycling; UFTATB; USAXS
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Funding
- Laboratory Directed Research and Development Program [06-SI-005]
- U. S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC520-7NA27344]
- U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC020-6CH11357, LLNL-JRNL-401946]
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TATB (1,3,5 triamino-2,4,6-trinitrobenzene), an extremely insensitive explosive, is used both in polymer-bound explosives (PBXs) and as an ultra-fine pressed powder (UFTATB). Many TATB-based explosives, including LX-17, a mixture of TATB and Kel-F 800 binder, experience an irreversible expansion with temperature cycling known as ratchet growth. Additional voids, with sizes hundreds of nanometers to a few micrometers, account for much of the volume expansion. Measuring these voids is important feedback for hot-spot theory and for determining the relationship between void size distributions and detonation properties. Also, understanding mechanisms for ratchet growth allows future choice of explosive/binder mixtures to minimize these types of changes, further extending PBX shelf life. This paper presents the void size distributions of LX-17, UFTATB, and PBXs using commercially available Cytop M, Cytop A, and Hyflon AD60 binders during temperature cycling between -55 and 70 degrees C. These void size distributions are derived from ultrasmall-angle X-ray scattering (USAXS), a technique sensitive to structures from about 2 nm to about 2 mu m. Structures with these sizes do not appreciably change in UFTATB. Compared to TATB/ Kel-F 800, Cytop M and Cytop A show relatively small increases in void Volume from 0.9 to 1.3% and 0.6 to 1.1%, respectively, while Hyflon fails to prevent irreversible volume expansion (1.2-4.6%). Computational mesoscale models combined with experimental results indicate both high glass transition temperature as well as TATB binder adhesion and wetting are important to minimize ratchet growth.
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