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USNSWC ltr, 4 Dec 1974

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NOLTR 71-192

0) DEVELOPMENT OF INERT SIMULANTS FOR

m CASTABLE PLASTIC BONDED EXPLOSIVES

OC0

Bycz B-y.Wayne L. Elban

18 NOVEMBER 1971 ., .D O7

NOLNAVAL ORDNANCE LABORATORY, WHITE OAK, SILVER SPRING, MARYLANDS-1 •o/o

DISTRIBUTION LIMITED TO U.S. GOVERNMENT

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IUNVLASSIP33DNOLIR 71-192

DEVELOPMENT OF INERT SIMULANTS FORCASTABLE PLASTIC BONDED EXPLOSIVES (U)

Prepared by:Wayne L. Elban

ABSTRACT: This report describes the development and evaluation ofinert simulants for two new castable explosives developed by NOL,namely, PBXW-106 and PBXN-103. The simulants closely duplicated theloaded density, processability, machinability, ultimate tensilestrength and cured hardness of each explosive. Each simulant has abinder system consisting of an oil extended, hydroxyl-terminated poly-butadiene resin that reacts with toluene diisocyanate to form a solidpolyurethane polymer. Glass beads were the primary filler Ingredientbut a small amount of zinc powder was incorporated in the PBXN-103i simulant to attain the high density and low casting viscosity require-

Sments. Using the basic solids-loaded polymer system selected forthis work it is possible to formulate a simulant with a density thatwould closely match the density of most explosives of military interest.

Nj

Approved by: A. B. DIETEANN, ChiefChemical Engineering DivisionChemistry Research Department

U. 3S • NAVAL ORDNANCE LABORATORYWHITE OAK, MARYLAND

UNCLASSIFIED

%4

IUCLAS8IIP3DD

NOLTR 71-192 18 November 1971

Development of Inert Simulants for Castable Plastic BondedExplosives (U)

This report describes the development of inert simulants for twoexplosives developed by NOL, namely, PBXW-106 and PBXN-103. Thiswork was supported under Task ORD-332-OO1/092-1/UF17--354-313.

ROBERT WILLIAMSON IICaptain, USNCommander

ALBET LIW(*ODYBy direction

UNCLASSIFIED

If t'MCLA.SSIPIEDNOLTR 71-192

C ONTENTS Pg

K. 1. INTRODIJCTION ........ ....................... 1

2. MATERIALS . .om os . o. . . . . . . . . . . . . . .2.1 Simulant Composition... 12.2 Polymer System ..................................2.3 Filler Materials . .................... 2

3. EXPERI AL ..... ............... . . . . .3.1 Processing .............. ....... . . 23.2 Simulant Properties Determination .......... .

3.2.1 Density u n ... .......... 33.2.2 Density Distribtion ......... 33.2.3 Viscosity.. ......................... 33.2.4 Workable Pot Life ..............3.2.5 Mechanical Properties ...............

4. RESULTS AND DISCUSSION . ......... ........ 4

5. SUMMARY............... . . . . . . .......... 5

ACKNOWLEDGEMENTS .................... ............ 6

REFERENCES ....... . . .......... . . . . 7

APPENDIX A A- 1APPENDIX B . . . . . . . . . . . . . . . . . . . . . . . . B- 1

APPENDIX C ..................................... C-1

TABLES

Table Title Page

1 Comparison of PBXW-106 and Simulant Properties . . . . . 82 Comparison of PBXN-103 and Simulant Properties . . . . . 93 Composition and Properties of PBXW-106 Simulants . . . . 104 Composition and Properties of PBXN-103 Simulants . . . . 11

9 ~UNCLAI'VIED

UNCLASSIFIES~NOLTH 71-192

1. 1IATODUCTION

A program was undertaken at the Naval Ordnance Laboratory (NOL),'dhite Oak, Maryland, to develop inert simulants for the castable,plastic-bonded explosives PBXW-106 (Refs. (1) and (2)) and PBXN-103(Ref3. (3) and (4)). Both FBX's are based on elastomeric polymerbinders filled with various powdered explosives, oxidizera, and fuels.The testing and evaluation of weapons systems for characterlsticsother than explosive performance, sensitivity, and lethality areusually conducted with inert-loaded warheads. The use of explosivesimulants simplifies certain phases of a warhead test program bygreatly reducing safety requirements. Ordnance devices loaded withenergetic materials make costly facilities and precautions essentialfor handling explosives; the same warhead, inert-loaded, may betested without such limitations.

The properties that the weapon designer may specify fop a givenexplosive simulant are many and varied. They include:

a. Densityb. Mechanical propertiesc. Magnetic propertiesd. Acoustic propertiese. Coefficient of thermal expansionf. Resistance to temperature extremesg. Thermal conductivity and specific heath. Pot life and viscosity of uncured simulantsi. Machinability of cured material

As a practical matter only those properties desired for a particularapplication are simulated.

The most important properties of both PBXW-106 and PBXN-103 which.ere to be simulated are given in Tables 1 and 2. Other importantproperties were homogeneity, good processing and casting character-istics, and machinability.

2. MATERIALS

2.i 3imulant Composition: The basic composition chosen to simu-late the non-explosive properties of both explosives consisted of acomnercially-available pclyurethane binder filled with solid glassspheres.

2.2 Polymer System: The binder was made by reacting hydrocarbonoil extended-eoly bd*hydroxyl-terminated liquid resins (Refs. (5) and(6)) with curing agents such as conventional di and polyisocyanates.The butadiene bacvbone of Poly bd resins is structurally similar tosolid, general purpose diene rubbers; hence polymers formulated withthese resins respond to solids reinforcement in an analogous manner.

*Trademark

1M1CLASSIFIED

UNCLASSI IFDNOLTR 71-192

propeller mixer to stir the ingredients until homogeneous. Mostcritical during this operation is adequate dispersion of the finely-,divided, solid catalyst; mixing should be continued until agglomer-ates are no longer visible.

A typical batch mixing procedure was as follows:

The glass spheres were added to the premix in several increments andmixed until homogeneous. If more than one particle size was used,the fine material was added first. Then TDI was added and thor-oughlymixed. Typical mixing cycles were 20 minutes in a one quart (5cc cc

maximum mixing capacity) Atlantic Research Corporation ARC) verticalmixer operating at 50 r.p.m. and 25 ± 2*C. Mixing under vacuum wasunnecessary because the viscosity was sufficiently low so that en-trapped air was easily removed during vacuum casting. The materialwas cured at 50 ± 5%C for 24 hours.

3.2 Simulant Properties Determination

3.2.1 Density: The density sample was vacuum cast into a5 cm I.D. cylindrical split mould. Once cured, the speciman was re-moved and machined to a nominal height of 2.5 cm. The density wascalculated from the measured dimensions and weight of the sample.

3.2.2 Density Distribution: A two-fold approach was takenin determining the extent of solids settling. Initially, indentationhardness of opposite faces of the density sample was measured using aShore durometer (Ref. (12)). Any appreciable density gradient shouldmanifest itself as a measurable difference in the Shore hardness ofthe top and bottom faces. A second technique involved determiningthe density of a series of slabs sectioned from a 15 cm diameter by30 cm long cylinder of material. Density data for various sectionsof the casting gave a clear indication of the degree of solidssettling.

3.2.3 Viscosity: In view of the large emnhasis on the com-positions' processability, a Brookfield viscometer (Model HAO) placedon a Helipath stand was utilized to determine viscosity. The Heli-path stand with accompanying bar-type spindles served to minimize thechanneling effect as the spindle was rotated and translated in ahelical path. Measurements were made at room temperature (25 ± 2"C)approximately 30 minutes after the addition of TDI; the viscometeroperated at a constant 1 r.p.m. for all compositions. Readings weretaken as the spindle was lowered and then reversed.

3.2.4 Workable Pot Life: Workable pot life is the timeduration that the viscosity of a ready-to-cast compositicn remainssufficiently low to allow acceptable processability. A SunshineScientific gel time meter was used to evaluate the time from the addi-tion of TDI to the time when the viscosity reached 10,000 poise, atthe casting temperature (25 ± 2 0 C). Although chosen arbitrarily,material with a 10,000 poise viscosity is still castable and henceconsidered to be completely manageable.

UNCLA31IFIE

UICLAS ISOMDNOMTf 71-192

3.2.5 Mechanical Properties: The mechanical properties ofPBXW-l06 and PBXN-103 desired to be most closely simulated were ulti-mate tensile st-ength, elongation and elastic modulus. These prop-erties were determined in accordance with American Society for Test-ing and Materials (ASTM) procedure D 638-67T using Type I specimendimensions (Ref. (13)). All testing was conducted using a BaldwinUniversal Testing Machine operating at a crosshead speed of 5 cm perminute.

4. RESULTS AND DISCUSSION

A single lot of R-45M resin was used in all formulations for thisprogram. The analysis accompanying this material listed a Brookfieldviscosity at 30% of 52 poise and a hydroxyl value of 0.73 meq/gm.The formulations for the inert simulant of FBxW-106 are given inTable 3, along with pertinent physical properties. The measureddensities of these compositions were close to theoretical and fol-lowed the relation:

where: 91 - solids loading weight fraction of the ith filler

a omponantOf - density of the ith filler component

•b - binder density

on e - simulant density

The density and processability of the selected simulant compositionclosely match PBXW-106. No measurable difference in indentation hard-ness was detected for the opposite faces of the simulant densitysample; it was concluded that solids settling didn't occur in thismaterial. In addition to being homogeneous, no voids were observedin any of samples of this material.

Table 4 lists the compositions and properties of simulants forPBXN-103. Again, measured densities closely approached maximum theo-retical given by Kq(l). Processing characteristics of the chosen com-position would allow this material to be made in the same equipmentused for PBXN-103. Density values for a number of slabs sectionedfrom a 15 cm diameter by 30 cm high right cylinder ranged from 1.89to 1.88 gm/cm3 from top to bottom. Hence, in addition to offering ex-cellent agreement with explosive density and viscosity, no solidssettling was evident.

4UNCLASSIFIED

=1CLA,k3DJPMIHOUR 71-192

1.Machining characteristics of the cured simulants were very simi-lar to those of their respective explosive. Both materials wereeasily cut with standard machining tools and had abcut the saine sur-face finish as either explosive.

Excellent reproducibility was obtained between Shore hardnessvalues of each simulant and respective explosive. However, exarnina-tion of tensile properties revealed some disparity. While there was7good agreement between ultimate tensile strength, elongation atbreal- was low by approximately a factor of four for each simulant.Also erratic stress-strain behavior made evaluation of the elasticnodulus of the simulants impractical. It is concluded, however, thatthe modulus of each simulant Is considerably higher than the corres-pondln; explosive. A comparison of the properties of the selectedsi.nulants with PBXCW-106 and PBXN-103 properties is given in Tables 1and 2 respectively.

5. MU IARY

Inert Simulants for the castable plastic-bonded explosives EX-106 and PBXN-103 have been developed and tested yielding compositionswhich have a number of non-explosive properties closely correspondingto those of the explosive. In addition to similar processing charac-"teristics, both simulants closely conformed to the loaded density,machinability, ultimate tensile strength, and Shore hardness of theirrespective explosives. The simulant for PBXZ-106 consisted of 73.60%"class beads and 26.40% polyurethane binder. Using the same bindersystem, the PBXN-103 simulant contained 77.59% of a bimodal blend ofglass beads and 5.00% zinc powder.

UL 35SUNCLASSIFIED

UNCLAS.SZ1DNOLTR 71-192

ACKNOWLEDGEMENTS

The able work of Edward T. Dyer in performing the mechanicalproperty tests is gratefully acknowledged. The numerous helpfuland enlightening discussions with Vernon D. Ringbloom is also grate-fully acknowledged.

6,INCLASS IElID

UNCLASSIIPID

MOM 71-192

REFMENCES

1. Heller, H., "High Temperature Bomb Explosives," (U), Chemistryand Explosions Research Departments Technical Progress Reportson Explosives Research (1 Oct - 31 Dec 1970) NOLTR 71-34,P. A-11-14 (Confidential)

2. NOL ltr 233:HH:Jcb Ser 0645 of 31 Mar 1971 to NOSC

3. Stosz, M., "The Development of Nitrasol as a New and SuperiorUnderwater Explosive (U)," NOLTR 62-204, 1963 (Confidential)

4. NOL confidential ltr 233:MJS:ba Ser 0193 of 5 Feb 1971 to NOSC

5. ARCO Chemical Company Product Bulletin BD-I: "Poly bd LiquidResins"

6. ARCO Chemical Company Product Bulletin BD-2: "Reinforcement ofUrethane Elastomers Based on Poly bd Liquid Resins"

7. Harville, R. L., Ignatowski, A. J., and Parker, C. 0., "Advancesin Propellants Based on Sinclair's Poly bd Prepolymer (U)," Rohmand Haas Company, Technical Report S-240, 1969 (Confidential)

3. Anderson, S. E., Harmon, D. K., and Willetts, T. L., "Developmentand Application of HTPB Composite Propellants " (U), 26th JANNAFSolid Propulsion Meeting, Vol. 1 (Jul 1970), P. 707-731 (Confidential)

9. Hamner, J. W., Hightower, J. 0., Davis, R. T., and J. D. Byrd,"Review of Propellant Research and Development with HTPB Binders"(U), 26th JANNAP Solid Propulsion Meeting, Vol. 1 (Jul 1970),P. 735-755 (Confidential)

10. ARCO Chemical Company Product Bulletin: "Tufflo Process Oilsfor the Rubber and Plastics Industries"

11. Potters Bros. Inc. Product Bulletin PB 24-1: "Glass Spheres as

Reinforcement/Fillers for Plastics"

12. 1968 Book of ASTM Standards, Part 27, ASTM Designation D2240-64T

13. 1968 Book of ASTM Standards, Part 27, ASTM Designation D638-67T

7UNCLASSIFIRD

UNCLASSIY3EDNOLR 71-192

TABLE 1

Comparison of PBXW-106 and Simulant Properties

Property PBXW- 106 Simulant

Density, gm/CM3 1.65 1.65 ± 0.01

Ultimate Tensile Strength,kg/cm 2 2.97(psi) (40) (42.29)

Elongation at Break, % 13 3.3

Shore Hardness, A/I sec dwell 25 Minimum 32

Workable Pot Life, hrs at25- C 4-6 8

Viscosity, poise at 259C 2,000-4,000 200

8UNCLA.S8IF lED

UNCLASS IFXZDNOLIR 71-192

TABLE 2

Comparison of PBXN-103 and Simulant Properties

Property PBXN-103 Simulant

Density,-gm/cm3 1.89 1.89 + O.C1

Ultimatl Tensile Strength,

(psi) (104) (106.59)

Elongation at Break, % 11 2.q

Shore Hardness, A/I see dwell 33 71

Workable Pot Life, hrs at25-C 48 5.5

Viscosity, poise at 25*C 350-1250 880

UNCLAAMW ED

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UNCLASSIFIED

UNCLASSIFIEDNOLTR 71-192

APPENDIX A

Glossary of Symbols

rensity, gm/cm3

a Ultimate tensile strength, kg/cm2 (psi)

eb Eiongatton at oreak, %

E Eiastic modulus, kg/cm (psi)

SH Shore hardness, A/1 sec dwell

PH Workable pot life, hrs at 250C

Viscosity, poise at 25*C

A-iUNCLASSIFIED

UNCIA331FIEDNOLTR 71-192

APPENDIX P

auidelines for Formulating Simulants with Different Densities

With the solids loaded polymer system chosen for this work, it

is possible to produce a simulant whose density would closely match

the density of almost any explosive of military interest. To

determine the amount of filler needed to obtain a simulant of

desired density one uses Eq(l). A sample calculation is given below

for a simulant utilizing the same ingredients in the PBXW-106

simulant and having a density of 1.75 gm/cml

Pa Pr, = 1 (1)Pe Pf Ps

where 0 = Binder weight fractionof = Filler weight fractionPe = Binder densityp = Filler densityPs - Simulant density

In applying Eq. (1) the theoretical maximum density of the filler

is used rather than bulk density. The unfilled cured binder whose

composition is

Wt %

R-45M Resin 32.50Tufflo 100 Extender Oil 65.00TDI 2.50

has a measured density of 0.905 gm/cm3 while the reported density1 1

for the glass spheres is 2.40 gm/cm3 . These values are Substituted

into Eq. (1)while making use of the relation

S- - r,(2)

Hence

1+ = (3)

0.905 2.40 1.75

Solving one obtains o. = 0.78.

Thus a simulant having a density of 1.75 gm/cm3 required 78% glass

heads and 22% polyurethane binder. To process materials of this

nature it is suggested that the procedure given in Section 3.1 of

B-iUNCLASSIFIED

AUNCLT33PIlDNoLm 71-192

this report be used as a guide. It is possible to greatly alter

the processing and casting characteristics by varying the particle

size distribution of bhe filler. The amount of hydrocarbon oil can

drastically change the mechanical properties of reinforced Poly bd

based elastomers. The table• below gives some indication of the

effect of oil-extension.

Formulation Parts by We;Zht

R4K100 100R-45MlO o O

TDI (-NCO/-OH- .1) 7.7 7.7 7.7

Stannous Octoate 0.2 0.1 0

Tufflo 6054 oil 3- 25 50

Zinc Oxide 300 300 300

Physical Properties

Ultimate Tensile Strength, kg/cm2 72a42 52.73 35.86

(psi) (1030) (750) (510)

Elongation at break, % 160 240 650

Elastic Modulus, kg/mcu 62.57 40.08 15.47

(psi) (890) (570) (220)

Shore Hardness, A/l sec dwell 82 73 49

B-2

UNCLASSIFIED

UNCLASSIFIRDNOL'1R 71-192

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DEVELOPMENT OF INERT SIMUIANTS FOR CASTABLE PLASTIC BONDED EXPLOSIVES(U)

4 ,ENRiP riV E NO TE5 (-yp f et report a.d inuu a~i diteI)

i Au rýOm, imi11 ~lu*,,d t. e 1ts, last issnia)

WAYNE L. ELBkN

6, L~PORT CATE Ia. TOTAL NO, Olt PAGES b NO OF REFS

18 November 1971 23 13C CONTR•ACT OR GRANT NO 9a, ORIGINATOR'S REPORT tIMU IEI•S)

., roJEcrNO. NNL TR 71-192

ORD-332-001/092-1/UF17-354-313C% US. OTNER REPORT NOISI (Any other rnunibetr that may be *asained

tht. report)

It DISTR1 BUTION STATDistribution lited to U.S. Government Agencies only; Test & Evaluation.Date ZttL nxll i Aýu.deu Vc 1, i2L7i. vu~ner requests for this publication must be.efcrred to "OL Ccde 237

It 5',JP- MEN'•T A•Y NOTES eI . SPONSORING MILITARY ACTIVITY

Naval Ordnance Systems CommandWashington, D.C.

13 AISTTRACT

(U) This report describes the development and evaluation of inertsimulants for two new castable explosives developed by NOL, namely,PBXW-106 and PBXN-103. The simulants closely duplicated the loadeddensity, processablility, machinability, ultimate tensile strength andcured hardness of each explosive. Each simulant has a binder systemconsisting of an oil extended, hydroxyl-terminated polybutadiene resinthat reacts with toluene diisocyanate to form a solid polyurethane pol-ymer.* Glass beads were the primary filler ingredient but a small amountof zinc powder was incorporated in the PBXN-103 simulant to attain thehigh density and low casting viscosity requirements. Using the basicsolids-loaded polymer system selected for this" work it is possible toformulate a simulant with a density that would closely match the densityof most explosives of military interest.

DDFORM 1473 (PAGE 1) UNCIASSIFIEDSiN 01070.807- 6801 Securitv Cla~si(ication

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Explosive Simulant

Plastic Bonded Explosive

Poly bd Hydroxyl - terminatedliquid resin

DD P°.(OOM 1473 ' UNCIASSIFIED