E N G I N E E R S AN D CO N T R A C T 0 R S S I N C E 1 8 2 7

Pontex Plant

THERMAL PROPERTIES & CHEMICAL REACTIVITY

SANL 712-005 CPn- MRr)

R . S. Wilson

January, February, March 1970

DEVELOPMENT DIVISION

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THERMAL PROPERTIES 8 CHEMICAL REACTIVITY

R. S . @&on

January , February, March 1970 SANL 712-005

ABSTRACT

A method u s i n g a chromatograph for a quantitative determination of the FEFO content of LX-09 was investigated. The accuracy of the i n i t i a l resul ts was variable. t o fluctuations of unknown origin i n the FEFO peak. Results are given of a sample analysi s of LX-09.

A modification of the procedure for determining purity with the DSC-1 i s dis- cussed.

Difficulty has been experienced i n o b t a i n i n g reproducible d a t a dbe

The molar heats of dscomposition of PETN, diPEHN, t r i P E O N , and tetraPEDN were measured and correlated w i t h the number of n i t r a t e and ether branches present i n each type o f molecule and the effect ive contribution of each branch t o the total heat of decomposition was obtained. The heats of fusion and decomposi- tion f o r each compound are reported.

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, proccss, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recorn- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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FEFO Determination i n LX-09

The possibi l i ty of using a gas chromatograph t o determine the concentration of

FEFO i n LX-09 has been investigated,

establish a method which would require smaller amounts of material and be simpler

and more readily reproducible than the fluoride analysis method] presently i n use,

The primary purpose of this work was t o

A Hewlett Packard 5750-B chromatograph equipped w i t h dual f l ame ionization

detectors was used.

t u b i n g packed w i t h O V - 3 on Chromosorb-W.

integrator,

w i t h a one-minute post-injection interval

The columns were 1/8-inch x 1 meter long stain!ess s t ee l

Peak area was measured with a d ig i ta l

The column oven was programed from 50 t o 250LC a t 40' per minute

The FEFO was dissolved i n chloroform from a finely ground LX-09 sample. Chemical

t e s t s on the residue showed greater than 98% of the FEFO was removed, N-butyl

ether was added as an internal standard, The ether readily separated from the

solvent and FEFO peaks and showed no observable e f fec t on the sample or evapora-

t ion loss d u r i n g the analysis.

The r a t i o of ether t o FEFO peak areas from this solution was compared w i t h the

r a t i o produced from a standard solution containing measured amounts of ethec and

FEFO in chloroform.

magnitude of response from the detector as d i d the LX-09 solut;,.l .

These amounts were chosen t o gSve approximately the same

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The procedure .was .developed using col umns we1 1 conditioned f o r FEFO Ini t i a1

resul ts indicated the repeatabil i ty o f the r a t io of peak areas had a standard

devia t ion of about 2.5%. Table I shows the resul ts of an evaluation of the

absol Ute accuracy obtained u s i n g two standard sol utions. Calculated t o the

number of s ign i f icant figures available, the indicated FEFO concentration was

exact.

The original columns soon showed signs of deterioration and new ones were pre-

pared us ing the same packing.

the newly packed columns; the FEFO peak showed large and apparently random

fluctuations in size. T h i s condition has been alleviated somewhat by continued

use of the columns, b u t the resul ts are s t i l l not as consistent as those obtained

w i t h the original col.umns.

showed results i n .error by 8.7%. Table I1 shows the best data obtained from an

analysis of LX-09, Lot 94-7.

Considerable d i f f icu l ty was experienced usi ng

A check o f the absolute accuracy of these columns

This method shows promise o f obtaining accuracy comparable t o the fluoride

analysis method, and .i.t .is def ini te ly simpler. . A fur ther attempt will be made c c

improve the stabi1.ity of the FEFO peak by varying the operating parameters as

well as investigating the possibi l i ty o f us-ing different l i q u i d phases and

supports.

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Table I

Accuracy Determination wi t h Original Columns

Sample I

1.8 u1 FEFO

1.0 p l n-butyl e ther

SamDle I 1

1.4 FEFO

1.0 ;1 n-butyl e ther

Ratio o f Ether t o FEFO Peak Areas

Run No. 1 2.050 2.525

2 2.012 2.621

3 2.024 2.739

4 2.146 2 746

Average 2.058

l a 2,5%

2.658

3,4%

Indicated FEFO content i n Sample I1 using Sample I as a reference: 1 - 4 u l e

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Run No. 1

2

3

4

5

6

Average

l a

Table I1

Quantitative Analysis of FEFO i n LX-09

Calibration Sample

1.6 p1 FEFO

1.0 p1 n-butyl ether

1 m l chloroform

LX-09 Sample

0.1416 g LX-09 ( L o t 94-7)

1.0 p1 n-butyl ether

1 ml chloroform

2.38

2.39

2.48

2.31

2.32

2.36

2.37

2.4%

Ratio of Ether t o FEFO Peak Areas

2.10

2.09

2.12

2.11

2.11

0.5%

Indicated FEFO concentration i n LX-09: 2.2%

FEFO concentration obtained from fluoride analysis method: 2.3%

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Determi nati on of PETN Purity by DSC- 1

An automatic switching c i r cu i t was b u i l t and interfaced between the DSC-1 and

analog t o d ig i ta l converter units used for purity analysis as previously

described. This permits adding simultaneous temperature recordings t o the

DSC-1 o u t p u t , thereby eliminating the need for manually recording the temper-

ature and permitting a more accurate determination of the melting p o i n t .

A new computer program was writ ten t o handle this additional capabili ty and t o

do a more sophisticated analysis than previously was done. An attempt t o a d a p t

th is program t o the PDP-8 computer was n o t successful because o f the very limited

storage available on the machine here.

t o permit d i rec t use of the punched paper tape by the IBM 360.

Therefore, an ALC routine was developed

T h i s system is now operating and has been used successfully on PETN. A check

of the accuracy of the analysis method i s planned for the near future.

Decomposition of PETN Homo1 ogs

An e f f o r t was made t o re la te the molar heats of decomposition of PETN, diPEHN,

t r iPEON, and tetraPEDN to the number of various types of molecular groups

present i n each molecule and t o thereby determine the contribution o f each g r o u p

t o the total heat .of decomposition. Only two groups may be considered i n this

analysis as an attempt t o evaluate any higher number leads t o a r indeterminate

s e t o f four equations. T h i s r e s t r i c t s the choice of groups to the n i t r a t e branch

and the ether linkage. In th i s case, a s e t of four- eqtiations i s ob, >ed, any

two of which may be considered independent,

rections to the heats of decomposition t o obtain a unique solution.

T h i s necessitates applying small cor-

........................ 2Pantex QumterZy Report f o r J m m , February, March 1968,

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Data were obtained from the DSC-1 with samples enclosed i n sealed containers

perforated t o release pressure. Results from a minimum o f four runs of each

compound are shown i n Table 111.

A good correlation was obtained fo r diPEHN, triPEON, and tetraPEDN; however,

PETN differed s ignif icant ly from these and was not included in the calculations.

Since PETN i s fundamentally d i f fe ren t from the higher order homologs in t h a t i t

contains no e ther l ink , th i s r e su l t was n o t unexpected.

The following values were calculated from the adjusted heats of decomposition as

shown in Table 111.

Contribution t o .the .molar heat of decomposition of the PETN homologs:

E the r group

Nitrate group

Nitrate group (from PETN)

119.4 kcal/mole

15.4 kcal /mol e

19.4 kcal /mol e

The adjusted values .were obtained by applying t o each heat of decomposition a

correction proportional i n magnitude t o .the heat and such t h a t the equations

yielded a unique solution.

0.25%.

In each case the required correction was less t h a n

In view of the s imilar s t ructures of the ether and n i t r a t e groups. -he large

difference i n heats o f decomposi t i o n as indicated above i s somewhat ?r is ing.

I t suggests the possibi l i ty t h a t energy from the n i t r a t e groups catalyzes the

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PETN

d i PEHN

tri PEON

tetraPEDN

Table 111

DSC-1 Analysis of PETN Homologs

Observed Heat Observed Heat Adjusted Heat of Fusion of Decomposition of Decomposi t i on

Std. Dev. S t d . Dev. kcal /mol e (%) kcal/mol e (%) kcal /mol e

11.1 4.5 77.4 5.4 - 11.1 4.0 212.4 5.1 211.9

13.6 7.6 361.4 6.6 362.2

20.2 7.4 513.7 6.6 512.6

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reaction of the ether l ink.

decomposition of the n i t r a t e groups i n PETN, which has no ether linkage. However,

more detailed informati on than is presently avail able concerning the nature of

the reactions would be required to make a def ini te evaluation.

This could also account for. the higher heat of