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
-1 3
7
f
‘ 2 ‘I I
I I I
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.
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