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THE 3SCOi71'T" -kTYP'(ES ,~ND

SUSPENiIONS 'A iMOLTE N: EEACHARACTERIST iCS

H. H'. BILLON1 AND X..?R.

* DTICAD-A264 038 ELEC 193

aAPPROVED Commonwedillh of Atisirafti

'FOR PUBLIC RELEASE P o93-10339

M.ATERIALSQ RESEARCH LABORATORYDSTC)

Pubilished by

Materials Researcht LuboratoriyCtorditu Avenuei~, Mnrib':,noingVictoria, 30.32 Aus~traiau

Farx (0.3),118 4536

0 CmoinntvnwLalh t/IofAitraho 1991AR No, 006-377

APPROVED PQR PUBDLIC RSLEASE

"Authors

n,HI Bilion

F-fo~rav ailvi, graiduated froin RMIV in, 1 92 ivt~h aOein Applied P lysies, After working ii tiw, RAAF QuatityAssmiawi Laboratories at Highiit lie /t•d•f MRL hi1.986, He works in, the Explosites Ordtace, Divisiom,His priimai•r areas qt interest are explos•eis rh/ology and

M.A. Parry

A, Pairry 1no lougtr toorks at MRL,

0 Contents

1. INTRODUCTION 7

2. FACTORS INFLUENCING SUSPENSION RHEOLOGY 8

S. EXPERIMENTAL 63.1 Description of Materials 83.2 Description of Viscometric and Mix Apparatus 83.3 Sample Preparation for Viscosity Determination 93.4 Experimental Procedure fyi' Viscostty Determination 9

34.41 Ratativoal Viscometiv 934,2 Efflux Vitpometry 11

3.5 Settling Experhmoitt 11

4, RESULTS AND DISCUSSION 114,1 The Effects qi Va•ying Concentration 124,2 Aging of TATB/TNT In tie Viscometer 114.3 The Effects q/Blending on Flow Behaviour 144.4 Thi Effects V' Thi.xotropy om Shear History and Viscosity 154,5 Tih' Variability ,l &Ma.\imntui Packing Fraction 224.6 Comptariso.is rwith 60:40 lwx/r NT 23

S. CONCLUSIONS AND RECOMMENDATIONS 28

6. REFERENCES 28

7. LIST OF SYMBOLS USED 29

The Viscosity of TATB Types A and BSuspensions in Molten TNT: General

Characteristics

1. Introduction

In recent years there has been increasing emphasis placed on the developmentof explosives that are insensitive to oiccidental hazardous stimuli [1], One of themost important of these explosives has been 1,3,5"triamndno.2,4,6-trinitrobeonene(TATB), which has the added advantage of high thermal stability, PresentlyTATB is in military use in both the US and UK, and Is also an explosivecomponent in some polymer bonded explosive (PBX) compositions le~g.PBX.9502, (TATB / Kel-F chlorotrifluoroethylene polymer 95:5)] used to preparepresscd charges,

Because Australia still has a substantial production capability In melt-castexplosives technology, a desirable way to lower the vulnerability of locallymanufactured ordnance would be to develop insensitive high explosiveformulations that can be processed in existing equipment (perhaps withmodifications), Research is being conducted at MRL on cast-cured PBXs as onemeans of achieving this 12], The other alternative is to replace the RDX incurrently used melt-cast fillings such as Composition B (RDX/TNT/beeswax60:40:1) or H-6 (RDX/TNT/Al/wax) by a less sensitive explosive filler such asTATB.

In a 1969 study in the US on insensitive high explosives and propellants(IHEP) [3], two melt-cast formulations containing TATB were considered:

(1) TATB/TNT 50:50(2) TATB/TNT/A1 40:40:20

However, virtually no information has been reported on these explosivecompositions 14].

As part of our studies of the rheology of molten TNT suspensions [5] andInsensitive high explosives we Investigated the behaviour of TATB in moltenTNT. A characterlsation of the rheology of TATB/TNT suspensions will assistin the development of a composition with maximal solids loading andacceptable rheology. This will enhance processibility and minimize hazard

response, Knowledge of the rheology will also facilitate the design/operationof plant equipment.

This paper Is a summary of the general rheological charq;teott i ti i"ATO Inmolten TNT-as well as a discussion of problems encounteread w,.recommendations for further research,

2. Factors Influencing Suspension Rheology

Evaluating the rheology of suspensions usually includes acquiring a knowledgeof the followingI

(1) the volume fraction of the disperse phase,(2) the shear rate (stress) applied to the suspension,(3) the particle size distribution of the disperse phase,(4) the particle shape of the disperse phase, and(5) the maximum packing fraction of the disperse phase

It should be noted that (5) Is dutLrmtinud by (3) and (4).Viscoelasticitv can be Important in somot. coses but Is apporvintly unLimportant

In TATB/TNT mixes as there is no signiflcant recoil In pouring, 'rherheological behaviour of suspensions li often complicated by timuwdeptu=dentbehaviour (thlxotropy), If the material Is thixutropic the ilow behaviour mustbe modelled thoroughly to enable prediction of oven simple tluws, SomeTATB/TNT suspensions are thixotropic (see later) but thlxotropic modellingwas not attempted In this study,

3. Experimental

3.1 Description of Materials

Type A and type B TATB were used, Both types were generously donated byRoyal Armaments Research and Development Establishmenit (RARDE),Sovenoaks, Kent, UK (now DRA Military Division), The TNT was commercialgrade from Albion Explosives Factory, The median diameters of types A and Bwere 40 pm and 20 pm respectively. RDX Grade B with a median diameter of140 pm was also used In some experiments,

3.2 Description of Viscometric and Mix Apparatus

A Haake RV2 rotational viscometer was used, A Hoake PG 142 programmerdrove the viscometer under a given speed regime, The sensor system waseither a smooth surfaced MVII or a profiled SVIIP system. The bob radii of the

8

• I i

MVII and SVIIP systems (Fig, 1) are 18A4 mm and 10,1 mm respectively andboth have a cup to bob radius ratio of 1.14. The samples were enclosed by awater jacket and held at 95,00 k 0,018C by a Haake N3 bath.

A jacketed melt and mix kettle of 95 mm internal diameter and 0.5 L capacitywas used for sample preparation, Incorporation was by a 12-vaned impeller of63 mm, diameter driven by a lank* and Kunkel stirrer, The kettle was held at95.00*C by the N3 bath.

3,3 Sample Preparation for Viscosity Determination

The solids (TATS or RDX) were incrementally added to molten TNT In thekettle at 95'C and incorporated by the impeller turning at 200 r/min. After thesolids seemed well dispersed In the TNT a further 30 min of stirring wasperformed at 200 r/mIn to ensure that no aggregates of solids and resolidlfiedTNT remained, The sample was then transferred to the viscortnter,Incorporation of the TATB and RDX into molten TNT required 60 min and40 min respectively,

3.4 Experimental Proceduure for Viscosity Determination

3.4,1 Rotational Viscometry

The bob and cup of the appropriate senior system were kept In an oven at atemperature of 100 to 105C. *rhe cup was then filled with the mix from thekettle, The bob was attached to the measuring head and the cup inserted intothe temperature.controlled water jacket of the viscometer,

R, RR iP

F•gre ti Depiction of (a) Haake MVII sensor system, (b) Haneke SVIIP sensorsystem

3,42 Efflux Viscome fry

This co~nsisted of recording the, time taken for 23 mL of iaMple to flow through

an orifice of radius 3.2 mm and depth 15 mm (6),

3.5 Settling Experiments

A TATB.blend was mixed with powdered TNT, -This was placed In A 10 MLmeasuring cylinder in a jacketed kettle filled with silicone fluid at 9MC, Thekettle was Agitated on a vibrating table until the TATO bulk volume wasconstant. The maximum packing fraction was calculated from this volume.

4. Results and Discussion

4.2 The Effects of Varying Concentration

TATD/TNT suspensions tit low concentrations exhibit Newtonian behaviour.This Can be seen in Figure 2 (a) and (b) for A suspension of 20 wt 0% TATB typeB In, TNT, The flow curve In 2 Mb was obtained 1.5 h after that In 2 W.) Theobserved 'bends' in the flow curves can be correlated with transitions fromlamninar behaviour at high rotation opt-eds. They are sirmlir to those found inmolten TNT 171. The product (diunily) k ("bend" r/ min) /(Oviosi ty) Isproportional to the Reynolds number and is 23.3 for curve 2 (a) and 24.1 forcurve 2 (b) (assuming density a 1.53 g/mL). Thus the Reynolds number Isapproximately co~nstant tindicating that these "bends" are the result of departuresfrom laminar flow.

The behaviour of suspensions at high concentrations is Yery different.Figure 3 (a) depicts A 5153 wt 41 TATB type B suspentiion 4ind Figure 3i (b)depicts a 51.5 wt 0% TATB type A suspension In TNT. Both thixotropy and thepresence of a yield point are evident as Is the lack of flowv curvL linearity,

4.2 Aging of TATB/TNT in the Viscometer

TATB/TNT suspensions do not thicken noticeably when held In the viscometerf~r long timne intervals, Figure 4 depites transient stress curves taken I h apart.The curves were obtainted by shearing the sample to constant stress. There isno significant change In apparent viscosity on aging because the low solubilityof TATS In molten TNT at 9M9 prevents significant dynamic recrystaillisation.

10

l0

00 72 144 216 210 360

D, I/$

I0

8a

m 6cu

2 (b)

00 72 14I 216 288 n60

0, 1/u

Fg•gure 2: (a) First flow curve, (b) stconud flow curvefor a TArB/'rNr 20/80suispensione at 95°C. Samtple, sh¢ardfromn u to 400 r/min in 4 min, held at 400 r/min

,bfr 0, min then lback to 0 r/odnin in4 m•n. MVII sunior systemn.

!1

300

240

m ISO

S120

"60

00 70 140 210 280 3500. I/t

300

240

S120

(b)60

0 - - I I .. , , . .. I ._.- .,.0 70 140 210 280 350

0, I/i

Fillft 3' Plow cluivgswbr (a) TATB type B, (b) TATB type A stspenlios rit 9511C,TATB/rTNT 51,5/48,5 sunspenr•ions slharsilfrom 0 to 231 r/miin in 2 min, held at231 r/mnin for 0,1 nIlift thten back to 0 r/nilf in 2 ilim," SVIIP gelsor sitqtelfm,

12

400

200

100

0 tOO 200 300 400 B0oTime, s

FIgurit 4: P-onsient stress eurves oblainnl 7 hi apart at 95"C. TATWfNT 70/30sample shteared to L'qllJibriallat 12 728 r/Ptin, TATB type A. SVIIP jelsor System.

4.3 The Effects of Blending on Flowo Behaviour

To determine the effects of blending the two types of TATB experiments wvereconducted on weight ratios of types A to B of 100:0, 75:25, 50:50, 25:75, Ind0:100. The wt, ratio of TATB to TNT was held constant at 51,5:415. As areference system for cormparimm rhoologicnI properties 60:40 RDX/TNT was alsoinvestigated; It is almost Identical to Composition B which Is used for fillingmunitions,

The flow curves obtained immediately after incorporating and stirring theTATB into the molten TNT are the most important. This Is because they afforda more accurate assessment of the flow properties than subsequent flow curveswhich may be Affected by sedimentation, and also, in the case of RDX/TNT, bythickening due to recrystallisation [5], Figures 5 and 6 depict apparent shearrate flow curves for the mixes mentioned above, rhese flow curves wereobtained immediately after transferring the sample from the kettle to theviscometer. After baseline correction of the raw data a number of features wereobserved:

1. After stirring, the mixes containing only type A or type B TATS anld the75/23 and 25/75 A/B blends possessed yield points, while the 50/50 A/Band the RDX/TNT mixes did not, ucnder these test conditions.

2. The yield points on the initial curve and return curves do not coincide formixes with A;B ratios of 100:0, 73:25 and 25:75,

3, Blending the two types of TATB results In a viscosity decrease at constantsolids level, This decrease in viscosity with blending waS also observed Inearlier work (81 (T•ble 1).

13

4. TATB/TNT suspensions which possess more apparent thixotropy (l.e.larger area of hysteresis loop) contain the greatust amounts of: type ATATE, iLe, the 100!0 A/B and 75:25 mixes.

300

240

60

0 70 140 210 2801 350

3O0

240

0 12 0 140020 28

000

20

a..

I240

60

0 70 140 2I0 280 ago

type A, 0.I/

Figure 5:Floto cirves fir TA7"B/T'NT 51-5/48,5 sum pensions at 956C, (a) TATBtpA,(b) TAT8 A:8 a 75:25, Wc TATB A-B a 50:50 Samples sheared fromt

0 to 231 r/inn in 2 min, held at 231 r~min for 0. 1 min then back to 0 r/tnln in 2 min.'ft'eflow curves: solid lines, Apparentsflow curve: broken lines. SVIIP senisorsystem,

14

12-

60,

0 70 140 210 280 350

300

240 -b

60

00 70 140 210 280 390

0. IUS

300

ýZ10 .S

~I0

0 70 140 210 280 IS00. /

fture 61 Flow curves for (a) TATB/TNT 52.5148A3 T-ATB A-8 u 25. 75,(b) TATB/TNT 315/148,5, TArD type 8, (C) RDXINT 0/140, RDX grade 8suspensions at 959C. Sam ples sheared from 0 to 231 r/mln in 2 Dni", held at231 r/lmin for 0. 1 i then back to 0 r/min in 2 min. True flow ourws: solid lines.Apparentk flow curvev: brokevu lines. S VIIi' sensor system,.

2)1iW : b U~x Viscosity Results for TATB/TNT at 85*C

TATB/TNT AV. ifflu~xRun No oýuto Tm a Rom rks

(Std. Div.)

10(A)/90 I Sedimetto

99' 20(A)/8O 1.2 Some sedimentation

100 30(B)/70 1.7 Some sedimentation (Stirred at200 r/min)

101 30(A)/70 118 Stirred at 300 rimin

102 40(A)/60 9A ST decrease with stirring

103 40(A)/60 91 ST decrease with. stirring

104 50(A)/O 47.3 TATO added over 40 min tit 300 r/min,lMeadings: 79,3 a, 39.5 %, 23.3 a

105 S0(A)/S 40.3 Stirring Increased to 600 r/min for 15 miiibefore lot readin$ and during re~adings.Readings: 64 so 35 a. 22.3 a

106 40(0)/60 3,2

107 40(0)/60 317 Pellet analysed 36.5 wt IX TATO(suggesting sedimuntation)

108 50(B/0 50.6 (3-6) P~ellet 48,9 wt 411 TATU (stirring at300 r/min)

109 500S/50 5015 1 I. 1)

110 25(A):2S(B)/50 20.1 (314) H~T decrease 25...- lth.8 a with stirring3 h 10 minalt 300 r/niun. (Pellot wt%TAT&~ 493, 49.0, 49AO 49.0, 49. 1)

III 25(AOM(B/50 18. 1 (4,0) CT decritase 24.3.- 13.5 1 with stirring4 hi 40 min at 300 r/mn,in (l'cllet wt %YTATB: 49-.0 48.7, 48.9, 48.8, 49.2)

Proceduret TNT wats melted at MIC, TATO was then added over about 0.5 hr whilestirring at 200 r/mln and was then stirred at 300 r/min (stirring speed was varied). Asample was then tok~en and the efflux time (EIT) measured alter about 25 -30 min andthen over about 6 hr (varied).

4.4 The Efeto of Thixotropy on Shear His tory andViscosity

Tb determine true shear rate from the data in section 4.3, plots of log w(angulAr velocity) versus log t (shear stress) were made (Pigs 7 and 111). Lineswere fitted to the straight sections of these plots. The fit regression coefficients

16

always exceeded 0.94 and were usually greater than 0.99. The true shear rate(in the absence of yield stress) could then be determined by two methods, Thefirst employed the gradients of the log o versus log ! plots as the flowbehaviour index n in a power law approximation which uses the followingequation for the shear rate of a system with radius ratio e

D 2 2(w 1m) i I(t I" - t 1

The second used the Krieger and Elrod technique [9]. The derivatives weredetermined from the fits to the log w versus log r plots, The discrepancybetween the two methods was usually less than 0.1%. Only power law shearrates were used because of ease of determination,

The presence of a yield stress T, complicated shear rate determination for thecame when:

". (2)

In this case the true shear rate at the bob Is given by:

D - (3)

where N a the slope of the plot of log w versus log t 110),The experiments involved programming the rotation speed from 0 r/min to

231 r/min in 2 min, holding at 231 r/min for 0,1 min and then programmingdown again to 0 r/mln in 2 min, Thus all the test conditions were nominallythe same, But on plotting the true shear rate as a function of time it was foundthat this was not really the case, Figures 9 and 10 reveal that the true shearhistory of a mix can bear little resemblance to the apparent shear history(calculated from the manufacturer-supplied constant) which Is linear,

It is notable that the shear rate Is not constant during the 0,1 min when therotation speed Is held constant at 231 r/min, but drops as listed In Table 2.This observation illustrates the common error of confusing constant rotationspeed with constant shear rate for thixotropic substances, Both viscosity andshear rate can change while stirring at constant speed 1101, Figures 11 and 12indicate a general decrease in viscosity for the return curve compared with theInitial curve. However the viscosity increases at 231 r/min (Table 3).

Hysteresis loops for the true flow curves in Figures 3 and 6 are open andcross over, This phenomenon, absent In the apparent flow curves, stems fromshear rate variation at constant rotation speed.

The shear rate analysis is Incomplete because the Krieger and Elrod method[9], used for determining the true shear rate, was developed fortime-independent samples, However the analysis indicates the stress and theviscosity changes with shear rate and characterises the differences betweenapparent and true shear rates,

+ , ' ' '. :" . J~I-

4I0 -- I

o I 2 3

Log w

2 (b)

La wo I 2 3 4 ,

Log w

Apre h LoS , - og plots of shear stres vs anjullar velocity for TATRITNT 31.5148,5suspnitsons at 984C, (a) TATB type A, (b) TATH A.-B 75:25, W€ TATR A:B

I.I..

S! I !

sol-so.

St

6W

0 o 23 4Log W

6

1b)

04oLo w

Log w

Piptere Ot Log log plots for (a) TATB/rNT 51,5/48A5 TATB8 A:845,.'75,(b) TATB.PrNT 51.3/48A5 TATU type 8, (C) RDX/rNr 60140, RVX grade Bmus pvisionte at 936C.

19

Table* 2: Drop in Shear Rate. at Constant Rotation Speed of 231 r/ini.

TATB Sample (A:8 Shear Rate Ot Start of Shear Rate at Find ofRatio) 01mh0.1 min

10010 30720

M232 230 206

30:50 236 213

253:7 234 223

01100 231 222

Tlibte .3: l1'Lrease in: Viscositii at 23l1 i/mmn

TATI Sla mpl IU Initial VlwCOIowty (Pr) Final Vlscosltv ('A's)

I100:0 078 1.13

75:25 0.69 0.81

50:50 0,63 0.70

25175 0.63 U.68

0:100 0,86 0.90

4.5 The VaP1abilityj of Maximum Packing Fraction

A significant parameter proportional to the viscosity of suspensions Is themobility parameter 111]:

(4)

Here 0 a Solids volume fractionOMa Maximumn packing fraction

0 is the total solids volume divided by the total sample volume and Oim Is themuaximum value of 0.

Little correlation occurs between experimental 0m values (Table 4) andviscosity variations, However, experimental 0m values cannot predict solidsloadings obtained In this laboratory, 0 values of 0.45 have been obtained inpractice for all the TATB blends listed in the tables althoulh Table 4 Indicatesthat thils is Impossible for the 100:0, 50:50 end 0W10 blends. * values of 0,48,0.53 and 0,64 have also been obtained for type A TAT8 in TNT suspension

20

although from Table 4 0m," 0.43, These higher values of 0 were obtained byusing the technique described in section 3.3. The discrepancies betweenpredicted and observed 6b seem to be a manifestation of the theory that Om Isshear dependent [12], since TATB incorporation involved shearing the mix,Particle orientation, particle migration leading to optimal packing and aggregatebreakup have all been suggested as reasons for the observed shear dependenceof 0m112] but the mechanisrms causing the effect in this study are unknown.

Able 4: Maximum Packing Fraction Valuesbfr the TATB Blends, ResultsDetermined by Settling Experiments in Molten TNT at 93C,

Composition of Sample Maximum Packing

A:B TATB Fraction

100:0 0.43

50:50 0.43

2S:75 0.47

0:100 0.43

4,6 Comparisons with 60:40 RDXITNT

RDX/TNT suspunsions exhibit constidL.rable long term thickening 15] absent InTATO/TNT The 60:40 RI)/TNT sl hpka uad no yield point. The shear ratedrop during 0.1 min at 231 r/min was from 269/s tu 204/4 aind the viscosityIncrease was from 0.34 Pas to 0,43 Pa~s at 231 r/min (cf. Tables 2 and 3),

The 60:40 RDX/TNT mix possesses the lowest overall viscosity of all themixes. However, at shear rates less than 50/s (which probably includes theshear rates which occur on pouring), the 25:75 A/B, 50:50 A/B and 75125 A/Bmixes may be brought into approximately the same viscosity range as 60:40RDX/TNT with little additional energy, This is because most of the thixotropicbreakdown takes place at shear rates below 150/s, a practically achievable shearrate,

The 100:0 A/B mix and the 75:25 A/B mix possess the greatest thixotropy andthese compositions would require Increased power consumption to reduceviscosity. The viscosity of the 0:100 A/B mix cannot be reduced to the samerange as 60:40 RDX/TNT at shear rates lower than 50/s after shearing to 231/sand back to 0/s,

21

350

2180 (b)

. 140

70

0

0 50 100 150 200 2507', .

2SO

210

01'

70

00 s0 100 150 200 250

T, u

S210 2

70

0 0 I00 '150 200 250T, .

Fijiare Pt Shyer hletoriie for TATB4/rNT 51,5/48,5 sue penutons at 95C, (a) TATOtj.pe A, (b) TATB A:B m 75,35, (c) TATB A:B a 5O:50. Sample. .iieare4 from0 to 231 r/nln In 2 min, hlucd at 231 r/mln fo 0! mmn then track to C) rhnin in 2 •nu,SVlIP sensor system,

22

350280 -.

S210

d 140

70

0 I:0 so 100 1I0 200 250

7, 3

280 Ib)

,. 140

70

00 50 100 Igo 200 250

7, 3

350280 (It

, 140

700

0 50 100 150 , 200 250T. U

FltPe 20 A Shtetr hlatorPe jr (a) TATBO/TNT 51.5/48,5, TATB A:B 25,75,(b) TATB/RNT SINK/4S,, TATO type B (,) RDX/TNT d0/40, RVX grade B11sppenllon na 95T. Sn, $plen sheared ftom 0 to 231 e/nle ln 2 mit, held aI 231r/mln fi 0.1 min then back to 0 *imun in 2 uit. S VlIP Netsor system.

23

I. '

S2

0 70 140 210 250 3500, I/|

S(bI'.

00 70 140 210 280 350

0. I/u

6

0 70 140 210 280 3500. /

Figure Ili Viacostty vo true shiea ratefor TATB/RNT 51.5/48,5 suspmnsions at934C. (a) TATB type A, (b) TATB A:B . 75,25, (c) TATS A:B a 50:50., $amplesMandfthim 0 to 231 r1rin in 2 W", held at 231 rlnin for 0.1 m•n thenh back to 0Pimin in 2 mit. SVUP sensor System.

24

6

.4

00 70 140 210 250 350

0, I/1

6 "

Ib)II

CL 4

""2

0 . . .0 70 140 210 250 350

6=. 0.

CLC

0 70 140 210 280 3500. 1//

FiAure 12: Viscosity ve tr•ue shr rite lor (a) TATBIrNT SINU45, rATBAKB a 25:75, (W) 7ATS/BTNT 51.5/485, TATS type B, (c) RDX/TNT 60/40, RDXgrade B suspension. at 954C. Samples shetired frovn 0 to 231 r/pln hi 2 inin, hield at231 r1/il for 0,1 mnitm the" back to 0 r/mit hi 2 mti.t, SVIIP sensor system,

25

5. Conclusions and Recommendations

We conclude that the viscosity of TATB/TNT suspensions may be improved byblending the various types of TATS available, It has been shown thatsuspensions containing as high as 70 wt percent of TATB type A In molten TNTare possible (this corresponds to thee u 0.64 composition described in section4.5). This study shows that the solids loadings and viscosities of suchconcentrated suspensions can be Improved over a rang. of practical shear ratesby appropriately blending type A and type 8 TATB. The maximum packingfractions of blends of the two types of TATS are shear-dependent and Incapableof prediction by standard settling experiments,

It is not possible to give a unique value for the viscosity of a given blend,The reason Is that concentrated TATB/TNT suopensions (ire thixiatropic, ix.etheir viscosities depend significantly on shear rate and Shear application time,Therefore a full characterisation of their flow properties requires thixotropicmodelling and this should be conducted to determine processing conditions foroptimal viscosity,

The compositions with the greatest apparent thixotropy contained the largestproportions of type A TATE, A further observation Is that compositionscontaining the 25:75, 50:50 and 75:25 tpot A /type B blunds can bu brought Into

00 approximately the samne viscositY range as WAO4 RDX/TNT by applicaltion of oshear rate below 150/s,

Performance and vulnerability issussmvnts should be carried out onl'rATB/TNT castinss to provide data on the ability of these manterials to meetInsensitive munitions requirements,

6.Rfrences

1. Spear, Rj, and Davis, L.M. (1989),An Aiustraliant hiseflsIV'tiitive nnitios polhi'it: a working paper prepared for tiltAustralian Ordnance Council, (MRL Goneral Document MRL-GD.00120WMaribyrnong, Vic,: Materials Research Labora tory,

2. Spear, R.I. (1990).1Insensitive munitions: Current Australian R&D, 40te Getn PropellantConference, Mulwala, October 23 to 25.

3. US Dept. of Defense / Dept. of Energy (1969).DoD/DOE htudyv of insensaitive high explosives aind propellants, Final Report,Study Summary, March 1969,

4. Dobratz, 0,M. and Finger, M, et al. (1979),Selectird senvitivity tests of triatninotrinitrobenzent (T..TB) and TATBfiormulations and their evaluation, (Report UCID - 18026) Livermore, CA.:Lawrence Livermore National Laboratory.

26

5. Parry, M,A, and Dillon, HH, (1987),The viscosity of (Molten) RDX/TNT suspensions, paper 57.1, 28thInternational Annusal Conference of ICT, Karlsruhe, FRG,

6. Eadle, J. and Milne, DJ. (1971).The viscosity of RDX/'NT suspensions, D.S.L, Report 431.

7. Parry, M,A, and Billon, HH (1987),The viscosity of molten TNT, (M.RL. Report MRL-R-1100), Maribyrnong,Vic.: Materials Research Laboratory,

8. Parry, M,A, (unpublished work)

9. Kreger, LM, and Elrod, H, (1953).Journal t' Applied Phlincs 2d, 134.

10, Nguyen, QD, and lDoger, DV (1987).Rheolokica Acta 2, 50$.

11, Dabak, T and Yucel, 0, (1986).Rheologica Arta a 527.

12. Wildemuth, CR, and Williams, MC, (1984).Rheo/oica Acla U., 627,

7. List of Symbols Used

Symbol Meaning

T Timec) Angular velocity of the vsicometer bobT Shear stressnl Viscosity9 Ratio of the viscometer cup to bob radiusn Flow behaviour index for a power law fluidT Yield stress

Shear rateN Slope in a plot of log u versus log vo Solids volume fraction*m Maximum packIng fraction, le the maximum value of 0

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REPORT NO. AR NO, REPORT SECURITY CLASSIFICATIONMRL-TR-91-24 AR-006.3717 Unclassified

TITLEThe Viscosity of TATB Types A and B Suspensions in Molten TNT: General Characteristics

AUTHOR(S) CORPORATE AUTHORH,H, Billon and M,A, Parry Materials Research Laboratory

PO Box 50.Ascot Vale Victoria 3032

REPORT DATE TASK NO. SPONSORDecember, 1991 DST 88/090 DSTO

FILE NO, REFERENCES PAGESG6/4/8-3949 10 28

CLASSIFICATION/LIMITATION REVIEW DATE CLASSIFICATION/RELUASE AUTHORITYChief, Explosives Ordnance Division

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Approved fur public release

ANNOUNCEMENT

Announcement of this report is unlimited

KBYWORDS

Viscometry

ABSTRACT

As part of a program of research into insensitive explosives, an investigation has been conducted Into theflow properties of suspensions of TATS types A and B in molten TNT. Low concentration TATB/TNTsuspensions are shown to be Newtonian while high concentration suspensions were found to bethixotropic and to exhibit yield point behaviour, The maximum packing fractions of blends of the twotypes of TATS are shown to be shear-dependent and incapable of prediction by standard settlingexperiments. The effects on the flow properties of blending the two types of TATB are discussed,Future directions for research are outlined,

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