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PREDICTED PERFORMANCE OF ENERGETIC PLASTICIZER FORMULATIONS.(U)jUN 80 L P DAVIS. R A HILDRETH

UNCLASSIFrEO FJSRL-TR-80-0015 NL

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FJSRL TECHNICAL REPORT 80"0015

JUNE 1980

00

PREDICTED PERFORMANCE OF ENERGETICPLASTICIZER FORMULATIONS

LARRY P. DAVIS

ROBERT As HILDRETH O

M4ELVIN Lo DRUELItIGER

PRWJECT 20

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FJSRL-TR-80-O015

PREDICTED PERFORMANCE OF ENERGETIC

PLASTICIZER FORMULATIONS

By

Capt Larry P. Davis - LECTE

Capt Robert A. Hildreth S AU 8 8 MD

Dr. Melvin L. Druelinger C

TECHNICAL REPORT FJSRL-TR-80-O015

. JUNE 1980

Approved for public release; distribution unlimited.

Directorate of Chemical SciencesFrank J. Seiler Research Laboratory

Air Force Systems CommandU. S. Air Force Academy, Colorado 80840

SECURITY CLASSIFICATION OF THIS PAGE ( e Da.Sa.,d ___________________

READ INSTRUCTIONISREPORT DOCUMENTA.TION PAGE BEFORE COMPLETING FORM

4, JKQRT NMBER2. GOVT ACCESSION NO: S. RECIPIENT'$ CATALOG NUMBER

/4/ FJSRL-TR-8on% ADAO*7 ______-e___

TLE (And Sublifle) - - V.

Predicted Performance of Energetic_________

7. AT0.CNREORGATMN a

/0 arry P. /avis

I. ER MG RGNIZT N NMEANDA ESS SO. PROGRAM ELEMENT. PROJECT. TASK

Frank J. Seiler Research Laboratory (AFSC) 6K71

It. CONTROLLING OFFICE NAME AND ADDRESS

Frank J. Seiler Research Laboratory (AFSC) AE

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Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (*I the abetrect entered in Block 2.It different 1000 Report)

1S. SUPPLEMENTARY NOTES

IS. KEY WORDS (Continue on revue, side it necoevuv ad Identify by block numbet)

energetic plasticizers bis-fluorodinitroethyl alkyl ethersenergetic polymers dinitropropylvinylether polymerheats of formation M4DO calculationsspecific impulse

40 ABSTRACT (Centinue an revevee Side iI nOCeewmend Identli by block monke)

Calculations of heats of formation (MNDO) and specific impulse for a series ofbis-fluorodinitroethyl alkyl ethers have been made. This series also includedoxygen and sulfur hetero atoms, N-HI N-NO" and CFN0- substituents. These calcu-lations reveal a trend toward decreasing isp values as the hydrocarbon chainincreases. The results suggest that ideal target molecules for synthetic effortare the smaller members of this family of compounds, and that such compounds

DD , 0"" 1473 amvion OP I NovS I9S1 OBSOLETE UNCLASSIFIEDSECURITY CLASSIFICATION OF THIS PAGE DM

I,

T uvir @8WFICI@N

OryIsos PASt~bme Pi emed

could be of value in applications as energetic plasticizers in propellant/

munition formulations. The results also indicate that these compounds are

promising in view of their increased performance compared to formulations using

non-energetic plasticizers.

UNrLASSIFIEDSSCURITY CLASSFICATIOM oF V-1- PAMEfMWe, Dea atMO

LIST OF FIQIRIS

PAGE

Figure 1 ....... .... ..... ..... .......... 2

Figure 2. .. .... ......... ........ ... 9

LIST OF TABLES

Table I.. .. ........ ........ ........ 7

TableZ................. . . ... ... .. .. .. .. ....

Table 3. .. .... ......... ........ ... 10

Acession ForN'TIS GBA.&IUnannoun~cedJuzsti1'ic :t~l_____

A .

PREFACE

This document, FJSRL-TR-80-O015, summarizes computer calculations

(INDO) of heats of formations and resultant specific impulse data on

formulations including energetic plasticizers. This work was done under

Work Unit 2303-PS-0! and was not previously published by the authors.

j1

TABLE OF CONTENTS

SECTION PAGE

Preface . .j

List of Figures.......... ... .. .. .. .. .. . . .....

List of Tables.......... ... .. .. .. .. .. .. . ...

Introduction............ ...... .. .. .. .. .....

Calculational. Procedures. .. ........ ........ 4

Results and Discussion. .. ........ ......... 4

fConclusion .. .. .. .. ............... ... 6

Acknowledgements .. .... ......... ........ 11

References. .. ........ ........ ...... 12

r . ..... . ..n_ .....

Composite energetic materials (explosives and propollants) in use today

are composed of approximately 80-85% energetic materials and 15-20% low

energy materials. These low energy materials are generally comprised of

10-15% plasticizer and other additives. In order to improve the energy

content of such composites, work is being done to increase the energy com-

tent of the low energy materials fraction.

Recent work at the Seller Laboratory and Los Alamo Scientific Labors-

tory (LASL) resulted In the development of a new class of polymitoethyl-

vinylether polymrs1 . Dinitropropylvinylother polymer (DWVU), Am in

Figure 1, was found to have excellent thermal (ITA - 2209C. eso.).phsical n

and chemical properties. The immrpeoration of such energetic binder4

(polymer) Ingredients Into solid propellant mad explosive forilationa isa

an excellent concept for increasing the eotery output during the combustin

and detonation processes. Subsequent work on DWWVP revealed a critical.

lack of available plasticizers that would plasticize this energetic binder2 .

Two energetic plasticizer available, 3M (Figure 1) and nitroglycerin (NO).

suffer from thermal stability and sensitivity problems for applications at

the higher operating temperatures projected for future systems. Thus, syn-

thesis of a new class of energetic plasticizers was initiated at this

laboratory.

This new class of energetic plasticizers was odeled after the structural

features present in the energetic binder WNPVDP. These bis-fluorodinitro-

ethyl alkyl ethers (FPOE, Pigure 1) have very similar chemical fuactiomali-

ties to the DNPP including ether linkages and polynitroethyl side chas.

During'the synthesis of examples of this class3 , we decided to investiate

FIGURE 1. FORMULATION INGREDIENTS

* ENERGETIC PLASTICIZERS

F-Cj-CH20CH2OCH2-C-F

NO2 NO2

FEFO (ACETAL)N0 2 N02.

F-C-CH20(CH2)NOCH1-C-F N =2-6,8

NO2 NO2

FEME (ETHER)

9 ENERGETIC BINDER

(CH2-CH)N

N02 N =VERY LARGE

OCH2-C-CH3 (F)

402

DNPVEP (ETHER)

I FUEL

2

FIGURE 1 (CONTINUED)$ FORMULATION INGREDIENTS

o AMMONIUM PERCHLORATE (AP)

NH4CLO4

o NITROGLYCERIN (NG)

CH ONO12 2LH2ONO2

CH2ONO2

o DIOCTYL ADIPATE

C8H1702C(CH2)4CO2C8H17

o HYDROXY TERMINATED POLYBUTADIENE (HTPB)

HO(CH2-CH=CH-CH2)NOH

o POLYETHYLENE GLYCOL 4000 (PEG 4000)

HO-(CH2CH20)iH

J3

calculated energy content Imrovements in formilat ions utilizing the em.,-

getic plasticizers compared to formulations using non-energetic plasticizers.

In addition to the carbon chain examples, various potential energetic plas-

ticizers, heteroatoms and nitro substituents were investigated.

II. CALCULATIONAL PROCEDURES

Experimental heats of formation are not available for the FMB series

of plasticizers, so the WDO molecular orbital computer program developed by

M. J. S. Dewar at the University of Texas4 was used to calculate heats of

formation for the various plasticizers. The calculation was performed with

complete geometry optimization of the molecule. Previous calculations with

?'tDO have shown that for molecules of this size, the calculated heat of

formation is usually too high. However, actual trends mong the various

plasticizers should be reproduced well by the calculated heats of formation.

The heat of formation is used along with the density and chemical com-

position as input to the performance program ISP5 . This program calculates

an equilibrium isentropic expaw-ion from the rocket motor chamber to any

arbitrary exit pressure. The Isp's calculated in this report were those

for the expansion to sea level, 14.696 psi., Compositions of the propellant

with and without the energetic plasticizers were used as input in order to

make performance comparisons. These compositions were varied to achieve

maximum Isp, but were kept within reasonable bounds for a standard aluminized

6solid propellant . Densities of the energetic plasticizers were assumed to

be the same as that of FEFO, 1.595g/cc.

III. RESULTS

Table I gives the calculated heats of formation for the various plasti-

cizers. Included for comparison is a second theoretical value for FEFO

4

*-J4

apparently based on a group-addivity calculation6 . The group additivity

scheme will probably produce a heat of formation lower than the true one

since it does not take into account destabilizing steric interference which

will be present among the nitro groups. Thus the true heat of formation

probably lies between the MNDO result and the group additivity result.

Because of uncertainty in the heat of formation, a sensitivity study

was performed in order to calculate its effect on the predicted performance.

Table II, which gives the calculated performances of the various plasticizer

compositions based on derivatives of FEME-3, shows that there is a difference

of about 2.5 sec in the Isp between the two different heats of formation for

FEME-3. One heat of formation is the MNDO-calculated number, and the other

is the group additivity estimated one for FEFO. (The two extra methylene

groups make little difference in the heat of formation.) Thus the best

value for Isp probably lies between the two given in the table.

Figure 2 shows the trend in predicted performance as the number of

methylene groups in the plasticizer increases. Note that there is a slow

decrease of about 0.2 sec/methylene group. These calculations are based on

the group additivity calculated heats of formation and may, therefore, be

somewhat pessimistic. It is obvious, however, that the predicted per-

formances for the energetic plasticizer formulations are several seconds

higher than the standard non-energetic formulation and approach the per-

formance given by using nitroglycerin as a plasticizer (See Table III for

these compositions).

Table III gives the compositions used to achieve the best Isp's shown in

the previous table and Figure 2. Recall that these compositions were kept

within reasonable bounds for an aluminized solid propellant. The compositions

which give the best Isp are identical for all of the FEND-3 derivatives,

and vary in a regular fashion as the number of methylene groups increase.

Note the large differences In composition between the standard propellant

composition and the energetic plasticizer combinations.

IV. CONCLUSIONS

The Isp calculations indicate that these energetic plasticizers have

promise as useful additives to propellant and explosive formulations. The

results reveal a trend toward decreasing Isp values as the hydrocarbon chain

increases. The improvement in calculated Isp values (4-6 seconds) over non-

energetic plasticizer formulations are high enough that these energetic

plasticizers should warrant serious consideration for future applications.

In addition, if an energetic binder were included in the formulations used

in these calculations the total improvement in specific impulse would probably

be on the order of 6-8 seconds.

It is important to note that these calculations were not totally opti-

mized for formulation composition, but were based on reasonable estimates.

Also, it should be noted that the ISP program assumes ideal combustion and

expansion, and, thus non-ideal combustion or expansion could change the

results somewhat.

However, these results are deinitely encouraging and the Isp technique

should be used as a guide for the synthesis of other potential energetic

plasticizers. To verify these calculated improvements, experimental work on

actual formulations and measured performance should be done.

6

TABLE I

CALCULATED HEATS OF FORMA&TION

(Kcal/mol)

COMPOUND AHf

FC(N0 2) 2 CH 2OCH2 OCH 2C(N0 2)2 F -89.0, 178.81

FEFO (FEME-1)

PC (NO 2)2 CH 2OCH 2CH 2OCH2 (NO2) 2F 9.

FEME-2

PC(NO 2)2 CH 2 OCH 2CH 2CH 2OCH 2C(N0 2)2 ' -9.9.0

FEME-3

FC (NO2) 2CH OCH OCH OCH C (NO2) 2F -127.7

FENE-3-0

PC (NO 2)2 CH 2OCH 2SCH 2OCH 2 C(NO 2)2 F -85.6

FEt4E-3-S

FC (NO) 2CH OCH 2NC 2 d 2 (N 2 F -83.5

FEME-3-NH

FC(N0 2) 2CH2OCH2 N(N0 2)CH2OC(N0 2)2 F -54.3

FEME-3-NNO 2

PC (NO2) 2CH OCH CP(NO )HOCH 2CNO)F -118.1

FEI4E-3-CFNO2

1Based-on group additivity value.

.7

TABLE II

CALCULATED PERFORN4ANCE FOR VARIOUS COIPOSITIONS1

Composition Maximum Sea Level Isp(sec) 2

Standard 267.7

Nitroglycerine Plasticizer 274.0

FEME-3 271.1 (Group additivity.f

FEME-3 273.6

FDE-3-0 273.6

FE E-3-S 272.0

FENE-3-NH 274.1

FEME-3-NNO2 274.9

FEME-3-CFNO2 273.9

See Table III for compositions

2 Unless specified, based on MND heat of formation

q• 8

Soa Level lop (eocode)

* * 10 '4 '4 '4 '4 '0,4 SI0- Ml

i I II.

I I

5 1

Sa I- U

0 S!

oS

L ~ .+ ....... .... ....*11

TABLE II!

CoMWOITIONS OF MAXINU PERFORNACE

Formulatiqn WeiEht Fraction

HNX AP Al Binder I Plasticizer2

Standard (DOA Plasticizer) .27 .43 .22 .06S(HTPB) .015(DOA)

Nitroglycerin Plasticizer .61 .01 .20 .04 .14(Nitroglycerin)

PEPO .9 .03 .18 .Os .15

PEW-33 .54 .08 .18 .Os .15

FP36-3 .60 .04 .16 .0S .15

PENE-53 .49 .13 .18 .05 .1S

iME-83 .43 .19 .18 .05 .15

P136-3-0 .60 .04 .16 .0S .15

PE3-3-S .60 .04 .16 .05 .15

PE13-3-NH .60 .04 .16 .05 .15

FEWE-3-NNO2 .60 .04 .16 .0S .JS

FEME-3-CFNO2 .60 .04 .16 .05 .15

I2

Unless specified, binder is PEG4000

2 Unless specified, plasticizer is FEME plasticizer

Composition for group additivity AHf

10

We would like to acknowledge Mr. Robert Hall of AFRPL for providing us

with a copy of their ISP program and Capt Fred yes of AMlIPL for providing

guidnce on propellant compositious and for helpful discussions. we Would

also like to acknowledge Mrs. Betty Darcy for typing this manuscript.

)11

1. S. A. Shackelford, R. R. 4cGuire, R. E. Cochoy, M. D. Coburn and

G. J. Marchand, "Nov Energetic Binder Breakthrough: One-Step Monomer

Synthesis and Polymer Characterization", Proceedings of the 1977 APA

Syposim on Processing Propellants. RVlosives and Ingrediants, Monterey, CA

p. 4.1-1.

2. Private commication with Dr. Mike Coburn of LASL.

3. R. A. Hildreth, R. L. Wallace, 4. L. DInulinger and B. A. Loving, 'New

Energetic Plasticizers: Synthesis, Characterization and Potential Applica-

tions", Proceedings of the 1978 Joint Air Force Systems Coinand-NMval

Materials Comand Science and Enginerig Symposium, San Diego, CA, p. 9%I.

4. 4. J. S. Dewar and W. Thiel, J. Amer. Chen. Soc., 99, 4499 (1977).

S. C. Selph and R. Hall, Theoretical ISP Program, Air Force Rocet Propulsion

Laboratory (AFRPL), Edwards, CA.

6. Capt Fred Myers, Air Force Rocket Propulsion Laboratory, private

comunication.

12

I