Particle Charae ter izat ion

A. A. PUNCAN

OCTOBER, NOVEMBER, DECEMBER 1 9 7 0

Development Division

PANTEX PLANT Amarillo,Texas

AZbuquerque Operations Office

PARTICLE CHARACTER I ZATI ON

A. A. Vuncun I

October, November, December, 1970 Endeavor No. 117

A c c ~ . NO. 22-2-44-02-317

ABSTRACT

The study o f the effects o f ro l l milling on Extex was started; the visual results are indicative t h a t a considerable reduction in crystal size occurs during the formulation process.

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 accuracj, 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, process, 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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DISCLAMER

DISCUSSION

In the manufacture of Extex (XTX 8003, 80% PETN, 20% Sylgard s i l icone rubber),

the formulation is mixed f o r about f ive hours. Freon MF i s added i n the

proportions of four pounds Extex to one quart Freon, t o enhance the mixing

a t lower power than would otherwise be the case.

i s milled on a three-roll rubber mill f o r a t o t a l of 25 passes.

After mixing, the formulation

I t has been found t h a t extrudabili ty is related t o milling:

optimum number of passes produces maximum extrudabili ty.

F ig . 1 w h i c h i s a p l o t of mill passes versus extrudabili ty. Extrudability i s

expressed as an integral number found by the trapezoidal rule of the Rossi-

Peakes extrusion t e s t conducted a t 125, 150, 175, 200, 225, 250, 275, and

i t seems t h a t an

This i s shown i n

300 psi.

the results indicate i n both cases tha t extrudabili ty i s improved through 20

passes and tha t an additional five passes was not beneficial; i n the unstored

sample a reversion i n extrudabili ty occurred.

were s milar t o the stored 1069-133 i n t h a t 20 passes improved extrudabili ty

and addi t ional f ive passes were not beneficial.

improvement i n extrudabili ty f o r every case tes ted, including 25 passes.

In one case (batch 1069-133), two samples were milled s ix days apart:

In sample 1069-154, the resul ts

Sample 1069-160 exhibited an

I t has been concluded from these milling t e s t s tha t g r i n d i n g occurs,

a dis t r ibut ion t h a t enhances extrudabili ty up t o a point; additional

produces a f ine r par t ic le s i ze which can be detrimental t o extrudabi

producing

grinding

i ty.

Additional milling parameters (temperature, r o l l e r spacing, and to ta l milling

time) were also evaluated by an extrudabil i t y correlation study o f 28 samples.

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I a

Y x x

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7

f

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0 cu 0

cr)

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0 c

0

The following correlations were found:

Parti a1 Correl a t i on S i gni f i cance Test Coefficients Level

Mi 1 1 Temperature .52730 .01

Feed Roller Gap + .45982 .02

Blade Roller Gap - .70182 .001

Number of Passes * .56014 .001

Total Milling Time - .24017 <.1

From these results, i t can be seen t h a t as the blade r o l l e r gap is reduced,

extrudabi l i ty i s increased.

extrudabili ty.

of passes, there should be an increase i n crystal comminution and possibly a

tendency f o r the par t ic le s ize d i s t r i b u t i o n to peak more sharply a t a s ingle

mode.

s tar ted.

As the number of passes increases, so does

W i t h the reduction i n blade ro l l e r gap and increase i n number

Thus a study to evaluate PETN par t ic le changes d u r i n g milling was

Two methods of evaluating par t ic le s i ze a f t e r m i l l i n g are b e i n g studied:

1. Dissolving away the uncured Sylgard and analyzing surface and pa r t i c l e

s i ze changes

Di lu t ion o f the Sylgard by the addition of Sylgard, Freon MF, or index 2.

of refraction o i l s and then measuring par t ic le s ize by Zeiss analysis.

The di lut ion method appears t o be the bet ter method i n t h a t par t ic le s i ze

reduction o r loss does not occur as i t does i n the solvent method. The use

of Freon MF was not sat isfactory i n t h a t the separation of Sylgard and PETN

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. I

was not achieved without harsh treatment.

Sylgard is sat isfactory; however, the use of index of refraction oils which

sharpen the contrast of PETN (those lower than the index of refraction of

PETN, 1.554) enhance photomicroscopy measurement. Flgs. 2

photomicrographs of PETN before formulation and a f t e r 25 mil 1

can be observed tha t considerable reduction i n par t ic le si

Dilution by adding additional

"a

'P t f

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- Original Mag Q, 320X

F i g . 3 Extex 8309-301-01 P PETN 8306-304-01 P

.. ..

F i g . 4 Extex 8309-301-01 D PETN 8306-304-01 0

F i g . 5 Ex tex 8296-301-01 PETN 8148-304-01, 03, 05

Extex Mag Q 400X

F i g . 6

txrex riag % 4uun

FUTURE WORK

Additional investigation shall be made on the amount of change that occurs during formulation. This shall be done by measuring particle distributions for various batches before and after formulation so that batch differences can be evaluated. The effects of mixing and milling shall also be evaluated.