p. a. urtiew, c m. tamer and r. l. simpson- shock initiation of 2,4-dinitroimidazole (2,4-dni)

8/3/2019 P. A. Urtiew, C M. Tamer and R. L. Simpson- Shock Initiation of 2,4-Dinitroimidazole (2,4-DNI)

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UCRGJC-120140

Shock Initiationof 2,4-Dinitroimidazole (2,4-DNI)

P. A. UrtiewC M. TamerR.L.Simpson

This paperwas prepared forsubmittal o the1995Amer i canPhysical Society Topical Conference

Shock Compressionof Condensed MatterSeattle, WashingtonAugust1348,1995

July19,1995

Thisisa preprint ofapaperintended forpublicationina ouma lorpmeedings. Sincechanges may be made before publication, this preprint is made available with theunderstanding that it will not be cited or reproduced without the permission of theauthor.


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SHOCK INITIATION OF 2,4-DINITROIMIDAZOLE (2,4-DNI)P. A. Urtiew, C. M. Tarver and R. L. Simpson

Lawrence LivennoreNational Laboratory,P.O. Box 808, L-282, Livermore, CA 94551The shock sensitivity of the pressed solid explosive 2,4-dinitroimidazole (2,4-DNI) was determinedusing the embedded manganin pressure gauge technique. At an initial shock pressure of 2 GPa,several microseconds were required before any exothermic reaction was observed. At 4 GPa, 2,4-DNI reacted more rapidly but did not transition to detonation at the 12mm deep gauge position. At6 GPa, detonation occurred in less than 6 mm of shock propagation. Thus, 2,4-DNI is more shocksensitive than TATB-based explosives but is considerably less shock sensitive than HMX-basedexplosives. An Ignition and Growth reactive flow model for 2,4-DNI based on these gauge recordsshowed that 2,4-DNI exhibits shock initiation characteristics similar to TATB but reacts faster. Thechemical structure of 2,4-DNI suggests that it may exhibit thermal decomposition reactions similarto nitroguanine and explosives with similar ring structures, such as ANTA and NTO.

INTRODUCTIONThe five membered ring explosive 2,4-dinitroimidazole (2,4-DNI) was first synthesized byLancini et al. (1) by nitrating 2-nitroimidazole. It

was later obtained by the thermal rearrangement of1,PDNI (2). Currently 2,4-DNI is being made from4-nitroimidazole, which is commercially available(3). This allows 2,4-DNI to be produced in largequantities in a cost effective manner. The goal of thesynthesis project is to produce a relativelyinexpensive explosive that has a higher energydensity than TATB and TNT, yet is still insensitive.The small scale safety properties, thermal explosionbehavior, and detonation velocity versus chargedensity of 2,4-DNI were reported by Jayasuriya et al.(3). In this paper, the shock sensitivity of 2,4-DNIwas measured at three shock pressures usingembedded manganin gauge techniques (4) andcalculated using the Ignition and Growth reactiveflow model ( 5 ) for shock initiation and detonation inthe DYNA2D hydrodynamiccode (6).EXPERIMENTAL

The experimental geometry is shown in Fig. 1.A 12.7 mm thick, 60 mm diameter Lexan flyer plateimpacted a target consisting of a 6 mm thick, 90 mmdiameter Teflon buffer plate and a 25 mm thick, 50.8

mm diameter 2.4-DNI charge. The 2,4-DNI chargewas held in place by a 3 mm thick Lexan ring. Six0.3 mm thick Teflon-insulated manganin gaugeswere placed in pairs along the center line of the 2,4-DNI charge at distances of 0,6, nd 12mm. Threeexperiments were fired in the 100 mm powder gunwith Lexan flyer velocities of 0.979 mdps, 1.518mm/ps and 2.273 m d p s , producing initial shockpressures of approximately 2 GPa, 4 GPa and 6 GPa,respectively. The measured changes in resistance ofthe manganin gauge elements were converted to

Iexan Flyer PlateII Lexan Buffer PlateLexanRing 2,4-DNI xx L a n g a n i n

GaugesIFIGURE 1. Experimental geometry fo r the shock


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pressure histories and compared to Ignition andGrowth reactive flow calculations.REACTIVE FLOW MODELING

The Ignition and Growth reactive flow model (5)has been incorporated into several hydrodynamiccodes and used to solve many explosive andpropellant safety and performance problems (7). Themodel uses two Jones-Wilkins-Lee (JWL) equationsof state, one for the unreacted explosive and anotherone for the reaction products, in the temperaturedependent form:p = A e-R + B e-R2V+wCvT (1)

where p is pressure in Megabars, V is relativevolume, T is temperature, o is the Gruneisencoefficient,C, s the average heat capacity, and A, B,R1 and R2 are constants. The equations of state arefitted to the available shock Hugoniot data. Thereaction rate law is:

dF/dt= I(l-F)b(p/po-l-a)X+Gi(1-F)CFdpYOeFeFigmax OeF


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$e!1,e!v)a

10-

8-

6 -

4-

2 -

Calculation /

Omm 6mm 12mmO+-J J m . A

I I I 1

FIGURE 2. Pressure histories fo r 2,4-DNI impacted at0.979 m d p y a Lexan flyer plate

rose slowly to 3 GPa over the next ps before thegauges failed. The 6 mm deep gauges recorded nopressure increase for the first 3 ps, followed by acontinuous growth to over 10GPa in the next 5 ps.The 12 mm deep gauges recorded similar pressurehistories. The Ignition and Growth model pressurehistories exhibit similar continuous energy releasesup to about 8 to 9 GPa, corresponding toapproximately 50% reaction. At this shock pressure,TATB-based explosives do not react (8), and HMX-based explosives exhibit a faster growth of reactionbehind the shock front than does 2,4-DNI(9)..Figure 3 shows the experimental and calculatedpressure histories for 2.4-DNI impacted by Lexan at1.518 mm/j.ls, creating a 4 GPa shock. At thisshock amplitude, TATB-based explosives do notreact, while HMX-based explosives transition todetonation at r u n distances of less than 10 mm (IO).The gauge records in Fig. 3 clearly show that 2,4-DNI is not close to detonating at the 12 mm gaugeposition. Although the 0 mm gauge records are notvery good, the other 4 gauges clearly show someshock front amplitude increase at the 6 and 12 mmdepths, followed by a pressure growth to 1 1 GPaover the next 3 ps at the 12 mm gauges. TheIgnition and Growth model calculates these increasesaccurately by allowing about 3% reaction duringshock compression (ignition) and a subsequentreaction rate with a p1 dependence.

dPe!1,2UIa

1 6 11412108

Calculation /-.

1 2 3 4 5Time-us

6 7 8

FIGURE 3. Pressure histories in 2.4-DNI impacted at1.518 m d p s by a Lexan flyer

The experimental and calculated results for thehighest Lexan flyer velocity experiment, 2.273mm/ps, producing a 6 GPa shock are shown in Fig.4. The 0 mm gauges record a rapid growth reactionto 12 GPa over 2 ps. The 6 and 12 mm gaugesrecord high pressures characteristic of a detonationwave. The Ignition and Growth calculations agreeclosely with the gauge records and predict thatdetonation occurs just before the reactive shockreaches the 6 mm gauge. At a shock pressure of 6GPa, HMX-based explosives detonate in about 4mm, while TATB-based explosives do notdecompose to an y significantdegree. Therefore,2,4-DNI is much more reactive than TATB at 6 GPa, butbut not asreactive asmost explosive molecules.S U M M A R Y

The shock sensitivity of 2,4-DNI has beendetermined using embedded manganin pressure gaugesand the Ignition and Growth reactive flow model. Itsshock initiation characteristics have been shown tobe similar to TATB-based explosives in that a shockof sufficient strength to ignite a few percent of thecharge then exhibits some amplitude growth as itpropagates through the charge, followed by a growthof reaction that can be modeled with a linear pressuredependence. The transition to detonation then occursin the usual fashion when the growing pulse pulseovertakes the leading shock front. Since it reacts


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ExDeriment20-15-

22 10-a

5 -

1 2 3 4 5Time-us

FIGURE 4. Pressure histories fo r 2,4-DNI impacted at2.273 m d p s by a Lexan flyer

relatively slowly at 2 and 4 GPa shock pressures,2,4-DNI is definitely less shock sensitive than HMX.Since it reacts slowly at 2 and 4 GPa and detonateswithin 6 mm at 6 GPa, 2,4-DNI is more shocksensitive than TATB. However, since most hazardscenarios involve shock pressures well below 6 GPa,2,4-DNI may be shock insensitive enough for manyapplications.Williams et al. (11) have studied the thermaldecomposition of several explosives with ringstructures similar to that of 2,4-DNI, such as3-nitro-1,2,4-triazol-5-one (NTO) and 3-amino-S-nitro-l,2,4-triazole (ANTA), and found that these compoundspartially decompose forming a polymer-like residuecalled melon. Thus 2,4-DNI should decompose in asimilar manner. Since at least one of thesecompounds, nitroguanidine, exhibits Group 2explosive behavior (12), 2,4-DNI may also fall intothis category.ACKNOWLEDGEMENTS

The authors would like to thank Dr. K.Jayasuriya and Dr. R. Damauarapu of the ArmyResearch and Development Center for furnishing the2,4-DNI used in this study. The authors also wouldlike to thank Frank Garcia for firing the 100mm gunshots and Leona Meegan fo r assembling theembedded gauge meets.

This work was performed under the auspices ofthe U.S. Dept. of Energy by Lawrence LivermoreNational Laboratory under contract No. W-7405-ENG-48.REFERENCES1. Lanc ini, G. C., Maggi, N., and Sensi, P.. Furmaco (puvia),Ed.Sci.. 18,390-395 (1963).2. Sharnin, G. ., Fassakhov, R. Kh.. and Orlov. P. P., USSRPatient 458553 (1975).3. Jayasuriya, K.,Dam auarapu . R.. Sim pson. R. L., Coon. C. L.,and Colburn. M. D.. "2.4-Dinitroimidazole: A PracticalInsensitive High Explosive," Lawrence Livermore NationalLaboratory Report UCRL-JC-ID-113364. March 1993.4. Urtiew, P. A., Erickson, L. M., Hayes, B., and Parker, N. L.,Combustion, &pf05iOnmd Shock Waves 22,597-614 (1986).5. Tarver. C. M.. Hallquist, J. 0..nd Ericks on, L. M.. in EighthSymposium (International) on Detonation, Naval SurfaceWeapons Center NSWC 86-194. Albuquerque. NM, 1985. pp.6. Whirley, R. G., Engelmann. B. E., and Hallquist, J. 0.."DYNA2D User Manual," Lawrence Livermore NationalLaboratory Report UCRL-MA-110630. Apri l 1992.7. Tarver, C. M.. Urtiew , P. A., Chidester. S. K.. an d Green, L.G., Propellants. Explosives, Pyrotechnics 18, 117-127 (1993).8. Tarver, C. M., Propellants. Explosives, Pyrotechnics 15, 132-142 (1990).

951 -961.

9. Lee, E.L. nd Tarver, C.M.,Phys. Fluids 23, 2362-2372(1980).10. D o b m B. M. and Crawford, P. C., "LLNL ExplosivesHandbook," Lawrence Livemore National Laboratory Repon11. Williams, G. K., Palopolli S.E. nd Brill, T. B., Combustionmd Flame 98 , 197-204 (1994).UCRL-52997, January 1985.

12. Price. D., C lairm ont, A. R., and Erkman. . 0.. ombustionmd Flame 17,323-336 (1971).

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p. a. urtiew, c m. tamer and r. l. simpson- shock initiation of 2,4-dinitroimidazole (2,4-dni)

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