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U N C L A S S I F I E D U N C L A S S I F I E D Synthesis Improvements of 3,3’ Diaminoazoxy furazan (DAAF) Elizabeth Francois, David Chavez, Mary Sandstrom LA-UR-07-5942
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Synthesis Improvements of 3,3’ Diaminoazoxy furazan
(DAAF)Elizabeth Francois, David Chavez,
Mary Sandstrom
LA-UR-07-5942
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DAAF Outline
• The GOOD, BAD and UGLY of DAAF
• Original Synthesis Method– Features– Factors– Challenges
• DAAF recrystallization– DMSO– Acetonitrile
• Novel Synthesis Path– Features– Future work
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DAAF: The GOOD
• Detonation Velocity 7.93 km/s
(1/2” pellets pressed to ρ= 1.685 g/cm3 neat)
• CJ pressure = 306 kbar
• Critical diameter < 3mm
• Drop height > 320cm, Friction >36 Kg
• Heat of Formation (ΔHf ) +106 kcal/mole
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DAAF: The Bad and the Ugly
• Synthesis intermediates and side products are energetic and have low temperature onsets.
• 2-Step process involving synthesis and recrystallization with DMSO to achieve pure product.
• Significant amounts of highly acidic hazardous waste: 5Kg DAAF yields ~40+ gallons of waste.
• Recrystallized DAAF does not press into pellets easily. Pellets are fragile and have low density, affecting the performance.
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Synthesis of DAAF
NO
N
NHOHH2N
NO
N
NH2H2N H2SO4
NO
N
H2N N N
NO
N
NH2
30% H2O2 NO
N
NH2N O
O
NO
N
NO2H2N
DAAF
Nitroso ANFHydroxylamineDAF
Synthesis scheme
• Important Parameters– Order– Temperature
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Addition Order- DAAF DSC
DSC courtesy of Mary Sandstrom
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Synthesis of DAAF- Impurities
DSC courtesy of Mary Sandstrom
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Recrystallization vs. Precipitation
• DAAF impurities can be easily removed with crash precipitation in DMSO and water. Overall yield is 80%
• Crash precipitation in DMSO creates small (<10μm) particles– Fragile neat pressed pellets– Poor pellet density
– Neat: ρ=1.6 g/cm3, TMD = 1.747– With Binder 3% KEL-F ρ=1.64 g/cm3
• DMSO DAAF can be recrystallized in acetonitrile– Larger particle size, allowing:
– Higher density of pressed pellets (1.69 g/cm3)– Better performance due to higher density– Pressed pellets are less fragile– Becomes 3 step process with 50% yield
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Particle size examples DMSO & ACN
SEM images courtesy of Ed Roemer
DMSO recrystallized DAAF; Particle size <10μm Acetonitrile recrystallized DAAF; particle size ~20μm.
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Performance comparison
DAAF Detonation velocity as a function of density and particle size
7.6
7.65
7.7
7.75
7.8
7.85
7.9
7.95
1.58 1.6 1.62 1.64 1.66 1.68 1.7
Density (g/cm3)
Det
Vel
ocity
(km
/s)
DAAF- 2.99 DMSO NeatDAAF-2.99 ACN NeatDAAF-2.99 ACN Max densityDAAFnov 1/2"DAAF binder Kel-f 97/3
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Novel DAAF Synthesis
• Due to waste issues, new DAAF synthesis was tried.
• DAAF synthesized in water with commercially available oxidizer rather than creating one with H2 O2 and H2 SO4 .
• Amount of oxidizer is controlled with this method.
• Did not initially make pure DAAF– The same impurities found in the original synthesis method were
present.
• By varying the pH of the solution, an improvement in purity is observed.
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pH comparison
DSC courtesy of Mary Sandstrom
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Novel Synthesis Particle Size Improvements
Analysis courtesy of Kien-Yin LeeSEM courtesy of Ed Roemer
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Novel DAAF Synthesis- Comparison
Novel DAAF synthesis• No impurities, high Onset of
Decomposition
• 1-Step process
• Larger particle size (~28μm)
• High pressed density 97% TMD, good performance
• Fast synthesis: 4 Hours
• Non-hazardous waste: “ salty water”
Original DAAF synthesis• Impurities which lower the Onset
of Decomposition
• 2-step process to remove impurities
• Small particle size of final product (<10μm)
• Low pressed density: 91% TMD, poor performance
• Lengthy synthesis process:
100 hours
• Large quantity of hazardous waste
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What’s Next?
• Scale up process to multi kilogram level, maintaining desirable characteristics. – Currently at 150g level with favorable results
• Critical Diameter and Diameter Effect tests in progress.
• Mechanical Strength tests in progress
• Mini-Gap tests to determine particle size effects on shock sensitivity planned
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Acknowledgements• Blaine Asay and Bert Harry• Dave Chavez- Chemistry• Mary Sandstrom- DSC, Design of Experiments• Ed Roemer- SEM imaging• V. Eric Sanders and Joe Lloyd- Performance tests and shot data
analysis• Kien-Yin Lee- Particle size analysis• Bryce Tappan and Dave Oschwald- Critical diameter and diameter
effect tests• Darla Thompson and Racci DeLucca- Mechanical testing• Karen Mehlin- HPLC analysis
