AD-A122 974 2 -PICRYL-5-NITRO TETRAZOLE:SSYNTHESI S ANC EXPLOSIVE

PROPERTIES(U ) MATERIALS RESEARCH LABS ASCOT VALE

(AUSTRALIA) R J SPEAR ET AL. JUL 82 MRL-R-859

,I.J, Acrrrn PG .191 NL

MhENEMONEhE NON

2 lii 2~ 2.

1.0

MRL-R-859 AR-003-042

DEPARTMENT OF DEFENCE SUPPORT

DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION

MATERIALS RESEARCH LABORATORIES

MELBOURNE, VICTORIA

-REPORT

MRL-R-859

2-PICRYL-5-4I1TROTETRA70L-E : SYNTHESIS AND

EXP'LOSIVE PROPERTIES

Robert J. Spear and Paul P. Elischer

Approved for Public Release

=. - ( COMMONWEALTH OF AUSTRALIA 1982

0JULY, 1982

---

DEPARThN OF DEFENCE SUPPORT

MATERIALS RESEARCH LABORATORIES

REPORT

MRL-R-859

7

2-PICRYL-5-NITROTETRAZOLE SYNTHESIS AND ' "

EXPLOSIVE PROPERTIES

Robert J. Spear and Paul P. Elischer

ABSTRACT

2-Picryl-5-nitrotetrazole (PNT) has been synthesised by reaction

of anhydrous sodium 5-nitrotetrazole with picryl chloride and obtained insuitable physical form by crystallisation from acetone-hexane. Impact,thermal and electrostatic sensitivity are all typical of a primary explosive.PNT ignites from match-head or hot wire to a powerful explosion but does notdetonate unless initiated by a strong shock such as from detonatinglead azide. RDX can be detonated by 100 mg of PNT but heavy confinementis required. PNT shows excellent promise as a replacement for tetrazeneas an energetic sensitizer in stab (and percussion) sensitive mixtures.

Approved for Public Release

@ COMMONWEALTH OF AUSTRALIA 1982

POSTAL ADDRESS: Chief Superintendent, Materials Research LaboratoriesP.O. Box 50, Ascot Vale, Victoria 3032, Australia

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REPORT NO. AR NO. REPORT SECURITY CLASSIFICATION

MRL-R-859 AR-003-042 UNCLASSIFIED

TITLE 2-PICRYL-5-NITROTETRAZOLE : SYNTHESIS AND

EXPLOSIVE PROPERTIES

AUTHOR(S) CORPORATE AUTHOR

Materials Research LaboratoriesSPEAR, R.J. and P.O Bo 50,

ELISCHER, P.P. A.o x 50,Ascot Vale, Victoria 3032

REPORT DATE TASK NO. SPONSOR

July, 1982 DST 78/115 DSTO

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Superintendent, MRJ Physical

Chemistry Division

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ANNOUNCEMENT

Announcement of this report is unlimited

KEYWORDS Tetrazoles NitrotetrazolesSensitivity 2-Picryl-5-Nitrotetrazole

PNTSynthesisExplosive properties

COSATI GOUPS1901 0703

ABSTRACT

2-Picryl-5-nitrotetrazole (PNT) has been synthesised by reaction of

anhydrous sodium 5-nitrotetrazole with picryl chloride and obtained insuitable physical form by crystallisation from acetone-hexane. Impact,

thermal and electrostatic sensitivity are all typical of a primary

explosive. PNT ignites from match-bead or hot wire to a powerful explosionbut does not detonate unless initiated by a strong shock such as fromdetonating lead azide. RDX can be detonated by 100 mg of PNT but heavyconfinement is required. PNT shows excellent promise as a replacement fortetrazene as an energetic sensitizer in stab (and percussion) sensitivemixtures.

SECURITY CLASSIFICATION OF THIS PAGE

UNCLASSIFIED

CONTENTS

Page No.

1. INTRODUCTION I

2. SYNTHESIS 2

3. SENSITIVITY TO INITIATION BY EXTERNAL STIMULI 4

4. EXPLOSIVE PROPERTIES 5

4.1 Initiating Properties 5

4.2 Stab Sensitization Properties 6

5. CONCLUSION 7

6. EXPERIMENTAL 8

7. ACKNOWLEDGEMENTS 12

8. REFERENCES 13

2-PICRYL-5-NITROTETRAZOLE : SYNTHESIS AND

EXPLOSIVE PROPERTIES

1. INTRODUCTION

Primary explosive fillings in service stores are largely based onthree materials: lead azide, tetrazene and lead styphnate. Lead azide andlead styphnate form the main explosive constituent in stab sensitive andpercussion sensitive mixtures such as NOL 130, with tetrazene as the energeticsensitizer. Lead azide is the main primary explosive constituent in

detonators while lead styphnate is commonly used in primers and inelectrically initiated compositions. The increasing demands for these storesto have extended shelf life, to be able to function under a diverse range of

climatic conditions and to be less prone to accidental initiation by externalstimuli cannot be adequately fulfilled given the technical shortcomings ofthese materials. There is consequently a considerable need to develop new

compounds to replace these materials in primary explosive compositions.Specifically, new energetic materials are sought with comparable (or better)

initiating properties but of enhanced thermal and hydrolytic stability and/orreduced susceptibility to electrostatic initiation.

Our approach at MRL has been to systematically screen selectedmaterials for potential as intiating explosives. The compounds selected fallinto two broad categories: those already reported in the literature but whoseexplosive properties have not been studied in detail, and new compoundsstructurally related to materials which have been shown to have someproperties of primary explosive. These materials are synthesised, subjectedto routine sensitivity testing, then explosive properties are assessed.

One class of compounds which has shown the desired characteristics

for providing new candidate primary explosives is the tetrazoles. Tetrazene,as well as the very promising mercuric [1-4] and silver [1,21 salts of5-nitrotetrazole, are included in this class. We have previously reporteddetailed studies of 1- and 2-methyl-5-nitrotetrazole (5,6] and have nowextended these studies to 2-picryl-5-nitrotetrazole (PNT). PNT has beenreported only once, in a conference paper [2], where it was described as being"very explosive and sensitive to friction" and of "doubtful hydrolyticstability". In this report we describe the synthesis of PNT and determinationof its explosive properties. In contrast to ref (2] we have found PNT to be avery promising primary explosive material

NO2 NO2

PNT0 2 N NO 2

2. SYNTHESIS

The preparation of PNT has previously been reported via "reaction ofsodium nitrotetrazole with picryl chloride" [2]. Sodium 5-nitrotetrazole canbe readily prepared by diazotization of tetrazole-5-amine monohydrate in thepresence of cupric ion and excess nitrite followed by reaction of theintermediate copper salt with aqueous sodium hydroxide (41. The product fromthis reaction is the dihydrate (NaNT.2H20) which can be dehydrated to the verysensitive anhydrate (NaNT).

In our hands, reaction of NaNT.2H 20 with dry picryl chloride in dryacetone gave good yields of PNT but there was always contamination by a secondproduct which could not be removed by recrystallisation. This second productcould readily be detected microscopically as long yellowish needles, in markedcontrast to the almost colourless prismatic clusters of PNT. In addition, PNTmelted with thermal decomposition (copious evolution of gas) at 165.5-1680 Cwhile these long needles melted without decomposition at 135-1450C. Picricacid occurs as irregular prisms which melt sharply at 121.5-122.50C, hencethis second product is not picric acid, but is probably a co-crystal orcomplex of picric acid, formed by hydrolysis of picryl chloride or PNT, andPNT. However, the wide melting range suggests that it is not a uniformcompound and its composition was not further investigated. Dehydration ofNaNT.2H 20 by addition of chemical drying agents such as anhydrous sodium ormagnesium sulfate to the acetone solutions of NaNT.2H 20 prior to reaction withpicryl chloride was not successful - the second product still formed. Theproblem was successfully overcome by dehydration of NaNT.2H20 to NaNT at 650Cunder vacuum then dissolution in dry acetone followed by addition of drypicryl chloride. This procedure is detailed below as Scheme 1.

2

iNaNO 2 jH /Ho 6 0

NH2 CUSO 4.HO -NO 2 -5 -) NO22. NaOH H20 73 3 Pa133 Pa

.H20 Na+.2H 2O Na

(NaNT. 2H 20) (NaNT)

ClO2 N NO 2

NaNT + 0 acetone • PNT + NaCl(by product)room temp.

PC

NO2

(picryl chloride)

Scheme 1. Stepwise preparation of PNT.

PNT was isolated directly from the reaction mixture by filtration ofthe by-product sodium chloride, reducing the volume of the acetone filtratethen addition of hexane. PNT was isolated in three crops, overall yield66.0%, as small clusters of almost colourless prisms. Although the recoveryin each recrystallisation is not particularly high, it was easily the best ofa number of solvent systems which were investigated. Increase in the hexane-acetone ratio led to separation into two immiscible layers upon cooling andlower recovery of product. The product was analytically pure (C, H, Nmicroanalysis). It exhibited only a single peak at 69.58 ppm in the protonnmr spectrum, indicating that it was also isomerically pure. However, we canonly tentatively assign PNT as the 2-picryl isomer. Tetrazolate anions withelectronegative substituents at C5 overwhelmingly undergo alkylation andacylation at N2 in preference to NI (7]. In the absence of a second isomer,which could not be detected even in the crude reaction mixture, picrylation is

assumed by analogy to have occurred at N2.

Three experimental batches of PNT (Batches A, B, C) were preparedfor testing. Batch A (6.2 g) was prepared from the products of a number ofsmall scale preparations by recrystallisation from acetone-hexane. Batch C(12.1 g) was identical with Batch A and was prepared directly from a largescale preparation of PNT. Batch B was obtained by crystallisation of theBatch A filtrate, which had been contaminated by condensed water, from ethylacetate-hexane. Batch B consisted of yellowish clumps of tiny crystalscontaminated by needles of the hydrolysis product referred to above. The

3

appearance of hydrolysis products which were not present in the crude reactionmixture or Batch A certainly cast doubts upon the hydrolytic stability ofPNT. However, a sample of Batch A has been stored in a loosely stopperedcontainer under normal atomspheric conditions for over 2 years and shows nodeterioration measurable by hot stage microscopy or DSC. a more completeinvestigation of the hydrolytic (and thermal) stability of PNT is currentlybeing undertaken.

3. SENSITIVITY TO INITIATION BY EXTERNAL STIMULI

PNT was subjected to the standard sensitivity tests for primary

explosives: ball and disc then Rotter impact (impact sensitivity), electric

spark test (sensitivity to electrostatic initiation) and temperature ofignition (T of I, thermal sensitivity). The results for these tests aredetailed in Table 1. Sensitivity to friction could not be assessed due tounavailability of appropriate test eqoipment.

The sensitivity of PNT to mechanical stimuli is typical of a primaryexplosive. The value for the figure of insensitiveness (F of I) of 13indicates that PNT is very sensitive to mechanical impact; it is comparablewith lead styphnate (12) and lower than lead azide (20) [81*. The inabilityto initiate in the ball and disc test, where susceptibility to pinching actionrather than direct impact is tested, suggests from our experience that PNT isa relatively soft material.

Sensitivity to electrostatic initiation is also typical of a primaryexplosive. PNT ignites consistently at spark energies of 0.045 J, comparablewith lead styphnate under these test conditions. However the ignitionthreshold of lead styphnate using the more sensitive approaching needle testis 8 J [9]. A more accurate description of the electrostatic sensitivity ofPNT must await availability of equipment for the approaching needle test.

PNT ignites to a violent explosion above 150*C (T of I test,Table 1). Variations in the T of I values for Batches A-C are small andprobably result from variations in particle size distributions. The DSC traceconsists of a single sharp exotherm (Table 1) and samples larger than 0.35 mgbuild up to a runaway explosive reaction. Explosion of samples during T of Itesting is not unexpected since the sample sizes (50 mg) are quite sufficientto build up to a self propagating explosive reaction. However explosion of

The F of I values for lead styphnate and lead azide were obtained relative

to lead 2,4-dinitroresorcinate = 11 [8]. Our testing method gives valuesrelative to RDX = 80, hence the values quoted in [81 may not be directlycomparable to our result for PNT.

4

such small samples under DSC conditions is much less common and is a strongindication that PNT readily propagates from ignition to explosion.

In summary, PNT functions as a primary explosive in the sensitivitytests employed here and should accordingly be handled with extreme caution.The previous report that PNT was "very sensitive to friction" [2] (although nodata was given) will be checked upon availability of suitable instrumentation.

4. EXPLOSIVE PROPERTIES

4.1 Initiating Properties

The initiating properties of PNT were assessed using a serie3 ofexperimental detonators. The results are listed in Table 2, entries 1-15.

The ability of PNT to initiate under normal firing conditions wasassessed as detailed in entries 1-4. The results show that PNT initiatesreadily either from match-head igniter (entries 1,2) or hot wire resultingfrom capacitor discharge of 0.08 J (entry 3). Although a powerful explosionwas observed in all cases, evidenced by fragmentation of the detonator tubes,no denting or cratering of the brass witness block was observed. The factthat the witness blocks were not marked (dented) is indicative of an explosionrather than a detonation. The possibility that the length of the PNT columnin entry 1 was insufficient to ensure build-up to detonation was notsubstantiated by the result for the larger column (entry 2). Increase ofconfinement by pressing into a mild steel detonator tube again resulted in apowerful explosion but not detonation (entry 4).

Two experimental detonators were prepared with an initial incrementof lead azide R01343 then an increment of PNT (entries 5,6). The aim here wasto determine whether PNT could be induced to detonate, the powerful shock fromdetonating lead azide providing the initiation means. Firing of bothdetonators resulted in cratering of the witness block while a detonator filledwith lead azide then methyl cellulose (entry 7), chosen to provide an inertfilling of comparable density to PNT, did not dent the wintess block uponfiring. The markings on the witness block in entries 5 and 6 were comparablewith a single increment lead azide detonator but substantially less than alead azide - RDX detonator [6]. Clearly PNT will detonate but the poweroutput upon detonation is considerably lower than RDX.

A series of detonators were then prepared in perspex tubes with anincrement of PNT followed by an increment of the shock sensitive secondaryexplosives RDX or tetryl. The aim here was to assess whether the powerproduced by explosion of PNT was sufficient to induce secondary explosives todetonation. The results are detailed in Table 2, entries 8-14. In all casesa powerful explosion resulted with denting but not cratering of the witness

5

block. The dents were substantially les- th-in f-, a comorable lead azide-RUXdetonator [6] while a detonator with i ;,-ondary t [ling of inert leadmonoxide produced no dent in the witress i,]-ock (entry 10). Increase of thePNT increment up to 400 my st 11 ii !,t r , nit in deton,,tion of the secondary

although an enhanced explosion does result (entries 12-14). Confinement ofthe PNT-RDX charge in a mild steel tube (entry 15) resilted in a detonationwith destruction of the tube and a distinct Ieep indentation of the witnessblock, comparable with a simi Lar Lead ,--ide-RDX charge. The ability of PNT todietonate sensitive secondaries is clearly very dependent up)on confinement.Lack of sufficient confinement cannot be overcomet or compensated for byincraasing the quantity of PNT up to 400 mr, .f. only 100 rq which was used inthe more con-f ined char.;,-.

A number Df ex-em!ntal detonators were fired with Batch B PNT asfilling dnd -,n enprall perf -rm-1i similarly to --ompiarable detonators containingtihe purer Bat-ues A -,r 2. Howover, in one case a detonator containing 400 mgof Hatch B and 1W, rir3 of RDX only deflagrated - a loud "whooshing" sound (andnJ 'xo? . ,'P. heard, the tube was not fragmented, and the contents wereconsumi 1xivinj a black residue -'f. entries 12, 13, Table 2). Since Batch F

mltain s ia ,uantiti.es of ydroly;is products, this result suggests thatS v"n inpu'ities could markedly eftect explosive properties of PNT although anyi.rmt cr onclusions must await mere detailed studies.

4.2 Stri Sens.i t.zation Prn~ertics

The ability of PNT to function as an energetic sensitizer in stab

s.ensitive com)ositions was assessed using admixtures of Batch A with leadazide RD 1343. Experimental detonators were prepared by pressing an incrementof lead monoxide (250-300 mg) then the experimental composition (35-52 mg)into mild] steel tubes at 600 MPa. The lead monoxide functions as an inertodesk f l ing and ensir-s that nit LatIon results directly from the needle,on.trating the explosive increment, and not by processes such as cracking orfriction b,tween the exolosiv- and a hard backing surface. The experimentaldetonators difftred from conventional stab detonators in that they were notfitted with a closing disc nor were they spotted with varnish.

St~b initiation ,onergies were determined by the use of a freefallinq needle of a similar design to strikers used in fuzes. Each experimentwas assessed as fire or no fire by sound (very loud!) and close visualinspection of the detonator tube. no partial ignitions which failed toptopagate were detected even under microscopic examination. At least 25detorators were tested for each composition. The data were analysed using theBruceton method [10] and the results represent the 50% fire level. The stabinitiation energies are listed in Table 3 together with results for comparablelead azide RD 1343 - tetrazene admixtures.

The results in Table 3 demonstrate the potential of PNT as asensitizing agent. Pure lead azide RD 1343 is relatively insensitive to stabinitiation and requires initiation energies of about 1000 mJ. Addition of PNTdramatically lowers the energy required for initiation, the minimum being 8.6

I6

mJ for 2% PNT. Increase in the percentage content of PNT from 2% increasesthe stab initiation energies, and this is co-.sistent with PNT being arelatively soft material (like tetrazene) which desensiti.:es the hard leadazide particles to friction from impact of the needle. Results for thetetrazene - lead azide admixtures show a similar trend. The minimuminitiation energy, 3.5 mJ, corresponding to 2-10% tetrazene, is significantlylower than for PNT and most probably reflects the relative ignitiontemperatures: tetrazene, 136 0C, PNT 1561C (Batch A). Sensitization of otherhard primary explosives by PNT will be assessed in the near future,particularly silver azide, with which tetrazene is incompatible 121, andmercuric 5-nitrotetrazole.

The stab initiation energy for pure PNT compacted at 600 MPa is 75.2mJ. Compacted pure tetrazene is even less impact sensitive and will notinitiate at impact energies of 280 mJ. Since an initiation energy of 75.2 mJis far too high for practical use, a series of detonators were prepared bypressing PNT at a range of pressing loads in the anticipation that theinitiation energies could be substantially lowered. Experimentally determinedinitiation energies are listed in Table 4. The results do not differ withinexperimental error and indicate that the initiation energy for pressed PNT isindependent of pressing load over the ranges studied here. There is noevidence that PNT has a tendency to dead press.

5. CONCLUSION

The synthesis of 2-picryl-5-nitrotetrazole (PNT) from readilyavailable starting materials in good overall yield has been demonstrated. Thehigh sensitivity to impact (F of I 13), low ignition temperature(T of I 155 0C) with ignition leading to a violet explosion, and ignition byelectrostatic discharge at energies as low as 0.045 J are all typical of aprimary explosive and clearly demonstrate the need to handle PNT withcaution. PNT readily ignites from match-head or hot wire to a powerfulexplosion but will not detonate under any of the conditions of confinementstudied here. RDX can be detonated in a normal detonator geometry using 100mg of PNT but heavy confinement is required. Compacted admixtures of PNT withlead azide display high sensitivity to stab initiation (initiation energies aslow as 8.6 mJ) while compacts of pure PNT require stab initiation energies of65-75 mJ, a value far too high for practical use. PNT thus demonstrates goodpotential as an initiating explosive and particularly as an energeticsensitizer for stab and percussion sensitive compositions. Although there isno apparent deterioration of PNT stored under normal atomspheric conditionsfor over 2 years, hydrolytic stability in solution appears to be suspect. Adetailed study of the hydrolytic and thermal stability of PNT has commencedand the results will be reported in a future publication.

7

6. EXPERIMENTrAL

A! I -herni 'a Is :i~ n the ''!,thj~sd~ wi're avd i lable* commero7i il ly o'r from provi ',-, stu iies. I nfrre r,-irr Ie- o n a

,Inicam SP 1000 spee-tro-ph )t-)mettr ind! nrti rn'.x e spectra Were-rec)r~ei i' C' MHz on a '.'ar i -in H4~I h.t.rI.*~ ramethy is i lane as

i nt,-r!-.i ' r,'teronc. Mi cro)ana lyq4s ra I'a :i ~r i, ' an

u 71 'In i.ro ~t r 1z Ii t,- .i hydrait'- T~ -~< rm ttraznl.-5-iio ~ ~ ~ ~ ~ ~ ~ ~ 4 t h o - i1 i:r '4. Th e

-~" I rVOlii'0 t2 t on y ad a! Vo*i'.I 'lume ofi*' and. ~iLt rat inn, 'he tjr,- jr: i :'ru3ineAi as

- rr,, ta~

._1.1 5-ni trot.otrazotate anhy.irjte, it-p- !o.: -1;.'.ration of thej)i a- C(5)C andA 133 ?a for 24 h, wi 4~1eoi t,,fr acetone

0 r35., st-t -lP~i,>os~ra for :'i - ' i it. tilli'sscorplett. Dry -ci -rvl chloride (5 ie in one

%efLaSk Was reS topfper-3 and then aLI ~ iri i r 48 h. Ther(e 1: or: -1 1 +h chloride)~

I, vol& ol -Dtiri. Me, ild thIe -*;c,.ntrated tor v idl 'tet sr,~ - illisationi!wa iroop Ietei hy ;ia: ;t The r'roduct

A'v ''' 1 1 -,)-; iti 'V i-' Wt cetone-hexane(tlive Pw~ (3. 2 qI -is Vi- ery -;mall almost

Z '0, r 1 3i ;I e-S -n t~ , -' a idci A h, ie r-oi it inq s)lidi was;-h v- .~-r~ hot fi !.tra ion -hen addit-ion of

cro 0' PN T (CW q) 4 if-rti - I ,,i'- tio f irst crop. A

0.ic-- 3 q 1-) Ir bc J-'i~aneJI 1,y- reneatiin. thercrsai>ato on thewi-ti"n ~ i-. e r Lt x~ two 7r op s mel-dwith viqTorous thermal

iccOr ~ 'o a I65- ,-0C hile the third kcrio; n idrw~nt this process at153-it Toc-al yield of I-'NT = 4.35 q, 66. 0%. "O11.r, 25.8%; H, 0.7; N,

34. 0. H,!No0 reqju res C, 25. 8; H, 0.;N, 34. 3. Tr (K~r disc): 3030,J'Q1- 1 50 1530, 1 348, 1 320), 1 31 3, 1 290, 1073, 9'79, 971 , 895, 814 cm 1 . Nmr

8

i'reparation of Experimental Batches of tNi

The first experimental batch of PNT, referred to as Batch A in thetext, was obtained by recrystallisation ot the combined products from a numberof small scale preparations. Thus PNT (13.9 g) was dissolved in hot acetone(85 ml), hot filtered and the filtrate reduced to 60 ml. Addition of hexane(60 ml) followed by standing overnight gave PNT (6.2 g) as almost colourlesscrystals which could be seen by microscopy to be clumps of tiny prismaticcrystals.

A second batch, referred to as Batch B in the text, was obtainedfrom the filtrate from the Batch A preparation. The filtrate was allowed to

evaporate and it was noticed that water had condensed into the crude crystalmass. Purification was by dissolution in hot ethyl acetate (45 ml), removalof water by pipette and then hot filtration followed by addition of hexane(55 ml). After standing overnight, the product was filtered off (5.8 g) andconsisted of small yellowish clumps of crystals which could be seen bymicroscopy to be small clusteres of prisms contaminated by a few yellowneedles of the hydrolysis product (see Section 2).

A third batch, referred to as Batch C in the text, was obtained byperforming the standard preparation on a larger scale. Batches A and C wereidentical with each other and with the first two crops described above in the

standari preparation.

Lead azfde was type RD 1343 and was obtained as a single batch (Batch 7) fromMFF St. Marys, NSW.

Lead st';phnate was type RD 1303 obtained from MFF St. Marys, NSW.

RDX was an experimental batch of type RD 1347 prepared at MRL.

Tetry! was stock held at MRL, originally obtained from US sources.

Sensitivlti Tests

The instruments used for Ball and Disc, Rotter Impact, the ElectricSpark Test and Temperature of Ignition (T of I) measurements were constructed

in this establishment to test specifications.

Sensitivity to impact was initially assessed by the Ball and Disctest but no ignitions were observed at the maximum drop height (30 cm).Rotter Impact was conducted on samples of 27 mg using a 2 kg weight fallingfrom heights of 30-55 cm over 5 cm intervals. The figure of insensitivity (Fof I) was calculated by comaprison with a sample of RDX (F of I = 80)determined using a 5 kg drop weight.

9

SelIt iivi tY to Lc~t.str: ifli t-iat-iii was assessed by the f-lIectriespark test and vi )Itlent explcjoi- n jc cur redi at: il t#estirnq enerqies :4.5,

Thermal behavio)ur was initially studied at a heating rate of1 UC'in sii 1 a Leitz Ortholux ri-roscone with an attached Mettler FP-2 hot

stdtqte, and isqunl by iiffer-,ntial icanninci cailo-rir- I:y (DSC) using aPe-rkin Elmer !)72.Experimental rfn iiitions we re vented a luminium pans uindera f lo.wt nq 'iitroot-n itmo--phere (1 5 ml /mi ), heati nq rate 1 0'C/ii-in. Ignitiontemprtirrs! wedre d.- ter~np frei a in i n-*rlm-nt- hot i~t to sp ci fications for theFRbE V ot I rs. -amples of ~&mt wi hec~ttd at 5 C/ni n arid~ measurements

Ex\P-ri-men' t: ie-oritors W-r-! firf-i rem(,tply using an 18 V, 0.08 Ji:* oi0 - t '; r rI. ni h- x wniich is-h ir(T".; e c-her t-.rough a match-headA

,r t< in lri ';ir-. The, 1-rformkance of -a-h experimentalr -, 1, ,*: ai rass; wi toiss lock, with partircl,lar

iaportan'Ce- be.:,. -i 1e IUpor wb'-the-r a letonation. occurred. The dent impartedto a wi roiess hP i-k by aieomtc has a li-stinctly cratered appearance with

s:lai iga thle ide.Teaie~ f a lent or the presence of a slightntle'tatl ) -4 hich ;lopes jr-iually in from.T the edges- in licates that an

,xp -, -,has c cu rretl *-u t hui il-up to(: Ietona ti on has not been achieved.1 tough 1--troo ly a qua Li 1 i-nive tes t, depth of dient studies have been used to

!, teriri ne It.nator per'-iormaince andi a number of experimental variables whichaft-~ !lie depth have been identified [11].

Experimental dletonrit-rs were prepared by pressing weighed amounts ofexulosivr- into flat bottom alumi nium ICI eoao tuibes, 5.57 mm i .l

aproximate wall thickness 0.3i -im, using an Elror press at a pressure of 90.7Ipa. A type i~ICI match-heai was then c:rimpedl into the detonator tube.

0. :; tat.,n OtIS US2,O kot-"- re

Experimental detonators were prepared from detonator tubesconstructed either of perspex of mild steel to which had been fitted abridge-wire device using Eastman 910 adhesive. The bridgewire levice wasconstructed of bakelite with copper terminals across wh"ch had been spotwel.-ded a 0.038 mm diameter platinum wire. The entire assembly is showniiaglrammatically in Figure 1 and a more detailed description can be found inref. [61. Explosive charqjes were prepared by pressing weighed amounts ofexplosive directly into the detonator tubes using an Eltor press. Where twoincrements were used, the initiating charge was pressed in first then thesecondary charge was added and pressed on top. The pressing pressures were166 MPa for the 4.12 mm i.d. tuhes and 90.7 MPa fur the 5.57 mm i.di. tubes.

10

,1 77 1 1 2It ( t jT If .'O't~ t I v t 1

a. Pr'rrlti of) 0! t !zed Mixture

The PNT was cautiously crushed betwe,.n filter paper using a woodenspatula and then sieved remotely through a 300 mic-ron sieve to break upaggireqates and ensure reasonable homogeneity of particle sizes. No problemswere encountered during this procedure. Explosive compositions were preparedby adding PNT to lead aide RD 1343 in the appropriate ratios to achieve abatch size of 1-1.5 q, eq. lead azide RD 1 343 [1.00 q), PNT (0.20 q) for the16.6% composition. Mixinq was achieved by fold mixing on a sheet of paper andappea red to be very good with n1 ) tendency to !;,eparate upon sta niin-.

Experimental detonators were prepared in ml i steel tubes, 6 mmo.d., 3.2 mm i.d., longth 6 mm, prepared from commercially availahl., tihing.A back filling of lead monoxide was first pressed into the tifbe in twoincrements using ai remotely controlled Pongrass press at a pressure of 600MPa. The overall column length of lead monoxide was 4 mm, requiring a mass of250-300 mg; variations resulted from small variation in diameter of thetubes. The experimental composition was then ad,lie on top and the unitrepressed. In the case of the sensiti:zed mixtures of lead azide and PNT, themixture was also pressed on at 600 MPa. Detonat,)rs using pure PNT wereprepared by pressing the PNT onto the lead monoxide at a number of pressuresrankging from 650 MPa to 320 MPa. In all cases; sufficient composition or PNTwas added to result in an explosive compact which was visually flat and almoStflush with the top of the detonator tube. The masses ranged from - 20 mq ofpure PNT at the lower pressing loads to - 52 mg of lead azi de containino 1-5%PNT. In one instance a detonator containing 35 ng of the 40% PNT - R!) 1343composition exploded in the mouli durin press ing. Damage to both meull anddrift was not appreciable.

Dot rns:inat ton oi Stuil I;i:t '*,t ic . i n 'r :;,:

The experimental set up, consisting of a drop tower test riq fittedwith a quick release mechanism, has previously ben described in detail[12]. Three strikers were used: 14.5 q for most ieterminations, 55.2 q whereinitiation energies in excess of 55 mJ were required, and 135 ( for pure leadazide RD 1343. The striker body was refitted with a new neddle after everytest whether or not a fire occurred. The needle was silver steel hardened to650 HV with a 0.08-0.20 mm flat on the tip. In each experiment tie strikerwas released from a pre-set height to impact on the experimental detonatorsupported in an aluminium holder held in a mild steel base. Each testing wasassessed as fire or no fire by sound (very loud for a positive fire) andvisual inspection of the detonator tubes. A fire resulted in splaying andcracking of the tube and ejection of much of the lead monoxide. A no fireresulted only in an obvious indentation into the compacted explosive. Thedetonators were not retested after a no fire and were destroyed chemically.

11

Pita I ri nary Iettermi naticns were conduhctod at a nuimbe-r of hei ghts to,ohtain in approxiimato 5096 fire levelI. Thie nteedle height was then varied usingroegular interval,: of approximately 10% of this fire level. A minimum of 25

otonators or te. tedi for *,ach experimental compos iti on. Results were

irnalysedi by the Bruceton method [10I and represent the 50% fire level.StaIniir.1 deviations have riot been included; the, Bruceton method of analysisis designed to give an o'Efrall estimate of the population from a limitednumber of samples. Statistical interpretation of the results derived from,;ample sizes used here qive a reliable es.timatp o~f 50% functioning levels but

riot for standard deviations-.

ACKN,)WLE)GE.MEN'rS

The ocrcl s-rn. of Mr A.M. Pitt is gratefullya'krmo~g Wd '~,?-i also like t~t think Mr J.R. Bentley and Mr R. Bird for

~ I f- o.Mr R.J. :owinton is thainked for his careful attention in* ~t. -. uu 2 s tivit- tests.

12

8. REFERENCES

1. Jenkins, J.M. and White, J.R. (1970). ERDE TN 21.

2. Bates, L.R. and Jenkins. J.M. (1975). "Search for New Detonants,"Proc. Int. Conf. on Primary Explosives, ERDE, Waltham Abbey, UK.

3. Scott, C.L. (1975). "Mercuric 5-Nitrotetrazole as a Lead AzideReplacement", Proc. Int. Conf. on Primary Explosives, ERDE, Waltham

Abbey, UK.

4. Gilligan, W.H. and Kamlet, M.J. (1976). NSWC/WOL/TR 76-146.

Microfiche AD-A036 086.

5. Spear, R.J. (1980). MRL-R-780.

6. Spear, R.J., Elischer, P.P. and Bird, R. (1980). MRL-R-771.

7. Butler, R.N. (1969). Leicester Chem. Rev., 10, 12; Butler, R.N.(1977). Adv. Heterocyclic Chem., 21, 323.

8. Mortlock, H.N. and Wilby, J. (1966). Explosivestoffe, 3, 49.

9. Jenkins, J.M. (1975). "Improvements in Delay and Priming Compositions",Institut fur Chemie der Treib- und Explosivestoffe, I.C.T., 6th.Annual Conf., June 11-13.

10. Culling, H.P. (1953). NAVORD Report 2101, US Naval Ordnance

Laboratory, Whiteoak, Maryland.

11. Savitt, J. (1979). "The Steel Dent Test and Santa Cruz FacilityHNS I End Tips", Proc. 10th. Symp. on Explcsives and Pyrotechnics,

San Francisco, Calif., USA, and earlier references cited therein.

12. Bentley, J.R. and Elischer, P.P. (1981). MRL-R-776.

13

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c

TABLE 3 STAB INITIATION FOR ADMIXTURES OF PNT AND

TETRAZENE WITH LEAD AZIDE RD 1343

a

PARTS PNT OR TETRAZENE : LEAD AZIDE % PNT OR STAB INITIATION ENERIES (mJ)TETRAZENE

PNT TETRAZENE

100 0 100 75.2 >280

1 1 50 7.9

40 60 40 24.3-

30 100 23.1 4.7

20 100 16.7 23.4 -

10 100 9.1 11.1 3.3

5 100 4.8 9.4 3.5

2 100 2.0 8.6 3.6

1 100 1.0 13.6 6.1

0.5 100 0.5 14.6-

0 100 0 " 1000 -1000

a Pressing load 600 MPa for all detonators

b Batch C. All other entries refer t Batch A

TABLE 4 STAB INITIATION ENERGIES FOR EXPERIMENTAL

DETONATORS OF PNT PRESSED AT VARIOUS

PRESSING LOADS

Pressing Load (MPa) Stab Inltlatlo Energy (mJ)

320 7 1.8A 7 4 . 9 _b

400 70.0

450 71.7 .

560 75.2 b

650 6 5 .8a

a Batch A PNT

b Batch C PNT

35m

2.29mm -- w1.78mm 10.00 or

7 1900m____ ', 12 or

!557mmrr

7.62mm 61mm12.5 2 mmdjam diam

0.82mm diarn 0.038mm diamCu wire Pt wire

Bakelite

Perspex or Mild Steel

FIG. 1. Schematic diagram of detonator tubeand bridgewire device assembly used inexperimental detonators.

MRL-R-859

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