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Author: Subject: Testing Electical Stimulation in Energetic Materials
quicksilver
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[*] posted on 19-4-2010 at 11:15
Testing Electical Stimulation in Energetic Materials


Concept: The testing of energetic materials sensitivity to electrical ignition

Proposal:
It has long been noted that energetic materials have sensitivity to static electrical discharge as well as simple electrical stimulation. The concept of a method to testing will be explored using a variety of methods to record that sensitivity. The recording of same can exist in Joules, current / voltage on a continuum or as a pulse or burst.

Device Concepts:
Simplicity in testing can be expanded upon by the use of static electrical devices (Van De Graf generators) or directly in the form of AC/DC power supplies. The actual device would be similar to a metallic spoon with several electrodes above the spoon-like holding platform or one where a single electrode is elevated up or down toward the sample held within the “spoon” shaped device. This allows for various degrees of energy to be brought into play and the recording of same can be displayed upon either a simple DIMM or more elaborate device. Elevation should also provide for contact with the energetic material.

There is every reason to believe that most energetic materials may be stimulated to ignition or detonation by electrical discharge. The complication is that some materials may be extremely sensitive to even low levels of current (static) and others may demand substantial levels of electrical discharge. Many years ago Gary W. Purrington (FireFox) developed a means to manufacture a bridge-wireless ignition composition that incorporated a mixture of graphite, conductive lamp black, lead oxide, chlorate and a binder. This composition worked very effectively as it produced a “resistor” of sorts that responded to the electrical energy of a battery whereupon it ignited for purposes of lighting a rocket motor or various pyrotechnic devices. Quite some many years before Gary – a patented device incorporating lead styphnate and graphite was used for the same bridge-wireless device to ignite a blasting cap (see attached info). Testing the resistive element needed only a DIMM and a level of current that sufficiently rose in temperature to a degree sufficient to ignite the chlorate within. However, the need to test the levels of electrical stimulation of various materials could be a boon to those who work with energetic materials in determining their sensitivity to unwanted ignition. Sufficient testing had been devised to preclude unwanted ignition via friction, impact, heat, etc. But the need for understanding electrical stimulation evaded the hobbyist and accident ensued on countless occasions with materials such as flash powder.

Modern manufacturing techniques have such dramatically sensitive mechanisms; often costing substantial amounts of money. The quest therefore for hobbyist purposes is to provide such a device at cost levels available to the consumer / amateur. It is my proposal therefore to develop such a testing device. Input is very welcome.

The concept of using a “spoon & electrode” platform had been well thought through to provide a mechanism to both contact the material and to provide an easily available arc or spark end-tool for the input of energy so as to stimulate energetic materials to ignition. Such a tool should have a means to provide both static electrical means as well as high-level energy from both capacitive discharge, transformer provided, and common battery level sources. Elevation of the electrode is mandatory as the level of electric stimulation may be quite high in some cases; extremely low in others. The well known sensitivity of some materials is occasionally taken to mean that they are “unstable”. But this has been shown not to be the case. Most energetic materials may be stored IF they can be provided a means to eliminate the stimulation necessary for their ignition. Too often that stimulation has been in the single Joule range static discharge and assessed as to be unexplained. The purpose therefore, of this testing medium is to eliminate the often unseen causation of ignition in various materials. These are not only the energetic peroxides but FAE scenarios in grain silos, etc.

Additionally, the means to test resistive compositions directly will enhance the bridge-wireless design feature with more of a standardization & surety. Device design & testing may be diagrammed.

There is every reason to believe that two areas of exploration can be surmised from this topic.
The bridge-wireless ignition & the testing of certain materials to determine whether they would ever be truly safe in conditions outside the lab.

It is my contention that testing may shed some light on energetic peroxides that actually cannot be guaranteed to a safety level comparable with other energetic materials & therefore the hazards of handling outside a professional setting really do not exist. Secondly, the concept of a bride-wireless ignition device may be expounded upon to the degree that testing may reveal a level of surety of ignition (& perhaps safety) that would make for a level of practicality for the hobbyist in model rocketry, etc.

{More to follow}


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[Edited on 19-4-2010 by quicksilver]
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[*] posted on 19-4-2010 at 11:43


Below is the actual composition that Gary Purrington had used with success in a bridge-wireless ignitor. This was sold as a "kit" to manufacture same.
Taken from notes on electrical match construction (PGI 1995)

Potassium Chlorate (ultra fine: 5-10um) - 50.00%

Graphite powder ( 2-9um) 25.00%

Al, atomized (2-5um) 5.00%

Charcoal (air float) 5.00%

lead dioxide 9.00%

Ferrotitanium 100 mesh 5.00%

Manganese dioxide (special prep 5um) 1.00%

Cellulose acetate in acetone (binder slurry, special prep)

If resistance too high add conductive lampblack to graphite (1-1.5ohms via 1amp, carrier 9Vdc)

Please note that both the lead styphnate/graphite composition as well as the above - has been tested quite a few times & preforms quite well, with no "misfires". However the need for measurement of resistance and the exact proportions need to be maintained. Substitutions of binder material or prep elements will cause failure



[Edited on 19-4-2010 by quicksilver]
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[*] posted on 19-4-2010 at 13:33


Quote: Originally posted by quicksilver  
Concept: The testing of energetic materials sensitivity to electrical ignition

Proposal:
It has long been noted that energetic materials have sensitivity to static electrical discharge as well as simple electrical stimulation. The concept of a method to testing will be explored using a variety of methods to record that sensitivity. The recording of same can exist in Joules, current / voltage on a continuum or as a pulse or burst.


[Edited on 19-4-2010 by quicksilver]





Testing expls for Electrical Spark Sensitivity has been
de rigeuer for years. Test specification are well documented.

Simply - voltage and rise time are varied.

The test are standard - the results, however, are not.

You may find this interesting. The sonic shock theory of electrical spark ignition.


Creator/Author Searcy, J.Q.
Publication Date 1977 Nov 01
OSTI Identifier OSTI ID: 5275524
Report Number(s) SAND-77-1649
DOE Contract Number EY-76-C-04-0789
Resource Type Technical Report
Research Org Sandia Labs., Albuquerque, N.Mex. (USA)
Subject 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ELECTRIC SPARKS; SOLIDS; CHEMICAL REACTIONS; COMBUSTION; ENERGY TRANSFER; GASES; SHOCK WAVES; ELECTRIC DISCHARGES; FLUIDS; OXIDATION
Description/Abstract A conceptual model for spark initiation of reactive solids is proposed in this report in order to focus on an understanding of spark initiation that can lead to the development of more-desirable components. The proposed model is a direct extension of a model previously developed by others for initiation of gas phase reactions, therefore a review of earlier work is given. In the model, energy coupling from the spark channel into the reactive solid is modeled by a two wave structure--a shock wave, followed by a subsonic blast wave. Detonation is initiated in most cases if the shock wave is energetic, or a deflagration is initiated if the shock wave is weak and the blast wave is energetic. The division of energy between the two waves is determined by the rise-time (or frequency) of the spark during arc development. The amount of energy delivered into the spark channel for a given test circuit is a function of the apparent spark resistance during arc development, and the apparent spark resistance is influenced by the conductive nature of the reactive solid. No new data are presented in this report, but suggestions are made for further work that could directly impact component design.
Country of Publication United States
Language English
Format Medium: X; Size: Pages: 22
Availability Dep. NTIS, PC A02/MF A01.
System Entry Date 2008 Feb 06

Translating into English :

Availability Dep. NTIS, PC A02/MF A01. = $$$





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[*] posted on 20-4-2010 at 07:15


Quote: Originally posted by The WiZard is In  
Quote: Originally posted by quicksilver  
Concept: The testing of energetic materials sensitivity to electrical ignition

Proposal:
It has long been noted that energetic materials have sensitivity to static electrical discharge as well as simple electrical stimulation. The concept of a method to testing will be explored using a variety of methods to record that sensitivity. The recording of same can exist in Joules, current / voltage on a continuum or as a pulse or burst.


[Edited on 19-4-2010 by quicksilver]


Testing expls for Electrical Spark Sensitivity has been
de rigeuer for years. Test specification are well documented.


Attachment: Pyro Lovold.pdf (892kB)
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[*] posted on 20-4-2010 at 09:03


Quote: Originally posted by quicksilver  
Concept: The testing of energetic materials sensitivity to electrical ignition

Proposal:
It has long been noted that energetic materials have sensitivity to static electrical discharge as well as simple electrical stimulation. The concept of a method to testing will be explored using a variety of methods to record that sensitivity. The recording of same can exist in Joules, current / voltage on a continuum or as a pulse or burst.
[Edited on 19-4-2010 by quicksilver]



I have had zero success in loading this as PDF's, so
I turned it into a PDF.

Dyda - I find no requirement of a static test in the mentioned
TB 900-2 (5 January 1998) which I have as a PDF, however,
it is over the 2meg limit.


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[*] posted on 20-4-2010 at 09:19


Testing for static electricity may be simply and conveniently accomplished by the use of surface testing equipment:

http://www.trifield.com/SurfaceDCVoltmeter.htm

Testing for static ignition is absolutely imperative in design and engineering elements of energetic materials & their implementation in various fields.
The proposal for a lab equipped method for determining static's level of ignition would be accomplished by either a standing generative mechanism (Van De Graf generator) or simplistic means.

Such a testing mechanism would relieve the guesswork from such issues as the supposedly inexplicable "instability" of energetic peroxides or flash made with fast release oxidizers.

In fact the well know company FLUKE makes some portable testers (DIMM) that are sensitive enough to gather some static from existing fields (metallic) & as many today, have means to record results in memory. By no means is the use of a standard DIMM in the same league as the above mentioned testing equipment (TriField) but a starting point could be assessed.
Too many times, negligence has resulted in blown off fingers, eyes, hands, etc. It's time to put an end to that issue as the means to deal with it are simple. Most people know to ground themselves prior to any contact with certain materials and various patents have existed to produce a "self grounding" blasting cap.

Just as with firearms, there is no "accidental discharge".
There are "negligent discharges"! And as such, if hobbyists have a means to deal with ignition stimulus - there is no reason not to do so. Any individual dealing with primary or highly sensitive energetic materials should welcome an opportunity to diminish or eliminate the results of such negligence.

The useful example of a bridge-wireless ignition system demands such an understanding. Additionally, even the habitual grounding of an individual when in proximity to such a composition should be a habit; the same as the electrical worker who uses the "one hand-in-pocket" technique.



[Edited on 20-4-2010 by quicksilver]
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[*] posted on 20-4-2010 at 10:34


Quote: Originally posted by quicksilver  
Testing for static electricity may be simply and conveniently accomplished by the use of surface testing equipment:
Too many times, negligence has resulted in blown off fingers, eyes, hands, etc. It's time to put an end to that issue as the means to deal with it are simple. Most people know to ground themselves prior to any contact with certain materials and various patents have existed to produce a "self grounding" blasting cap.

[Edited on 20-4-2010 by quicksilver]


---------
poca favilla gran flamma seconda. Dante

HYDRAULIC CAKE-PRESSES

Ebonite plates are decidedly preferable to those of copper, they are not so easily
bent out of shape and always retain a plain smooth surface, and also because they
have sufficient elasticity to transmit the pressure evenly all over the layer of powder,
even should they get out of the horizontal. On the other hand , they have the
disadvantage of becoming easily electrified; in fact, alternate layers of ebonite and
powder really form an electric pile. It is quite possible that by excessive friction, and
still more so in the case of a thunderstorm, the whole pile may become charged with
electricity. A case came to the author's knowledge where a workman, just as he had
finished charging the press and had opened the water-pressure valve, saw a
thunderstorm approaching. According to his instructions, he left the building, leaving
in the meantime the powder under pressure. After the thunderstorm had passed
over he returned to the house, and was about to discharge the press when it
exploded. Before his death the man stated that when he was about to empty the
press a spark about four inches long passed from it to his finger. This points to the
advisability of providing presses with an earth connection in order to prevent
accumulation of electricity.

Oscar Guttmann
The Manufacture of Explosives
New York McMillan and Co. 1895


Letter to — Pyrotechnica IX April, 1984
By /djh/

The report in the Reactions section Of PYROTECHNICA VIII of the death of Mr. Cost
Mifsud which was attributed to his working with a potassium chlorate-antimony trisulfide
salute mixture raises questions as to the sensitivity of various compositions to static
ignition.

There is little in the literature is to the spark sensitivity of pyrotechnic compositions
other than those used by the military. Recently, however, information has been pub-
lished on two mixtures used in the production of fireworks: black powder, and the
potassium chloride-antimony trisulfide salute mixture.

Work has been performed by Li and Wang, at the Beijing Institute of Technology,
Beijing, People's Republic of China, as reported in the Journal of Electrostatics, 1982,
11(3), 319-32, (also see Chemical Abstracts, 97:25936a). They found the minimum
value for energy required to cause the ignition of black powder 50% of the time to be
26.4 mJ (millijoules).

K. Lovold and T. Middleton, in their article "Ignition of Explosive Powders by Electric
Sparks" (Foredrag vid Pyroteknikdagen, 1977, pp. 137-171) report that "of particular
interest is the result obtained for the meal powder, which ignited at energies down to 45
mJ . . . The results of these tests cannot be considered minimum ignition energies for
the tested samples."

It has been reported that the human body is capable of generating sparks with
energy in the 20 mJ range with ease; therefore, one would be wise to exercise caution
when dealing with meal powder or with compositions containing meal powder
ingredients, such as fountains, rockets, drivers, etc.

Potassium chlorate-antimony trisulfide mixtures have long been known to b4
dangerous. Faber (1919) points out that ". . . it is also of such susceptibility that
extraordinary care is required in the handling of it, or a premature explosion may result."
K. Lovold and T. Middleton in their article, "Characterization of the Sensitivity of
Explosive Powders to Electric Sparks, a Proposed Testing Method" (Pyroteknikdagen,
1980, pp. 49-85) noted that ". . . two of the compositions (2 and 5) [2] Sb2S3 + KCl03,
[5] Zr + Pb02) showed high frequencies of ignition for short duration (1-10
microseconds) sparks with energies in the range of 0.1 - 1.0 mJ . . . Spark energies in
this range would be barely noticeable as static electric discharges from a person."

There would appear to be little excuse to use potassium chlorate-antimony trisulfide
salute mixtures since good substitutes are available. The use of meal powder and meal
powder-type mixtures is another problem and is best handled by making sure that all
guards against the generation of stray sparks are in place; i.e., non-sparking tools, elec-
trical grounds to all metal in the shop, cotton socks and clothing, maintenance of high
humidity, and not petting the cat while working!

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