U.S. patent application number 11/271359 was filed with the patent office on 2008-05-01 for reduced sensitivity melt-pourable tritonal replacements.
Invention is credited to Alan G. Allred, Daniel W. Doll, Jami M. Hanks, John B. Niles.
Application Number | 20080099112 11/271359 |
Document ID | / |
Family ID | 27613871 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080099112 |
Kind Code |
A1 |
Doll; Daniel W. ; et
al. |
May 1, 2008 |
Reduced sensitivity melt-pourable Tritonal replacements
Abstract
This melt-pourable explosive composition shares explosive
properties comparable to those of Tritonal and is melt-pourable and
castable under conditions comparable to those of Tritonal, but
experiences equal or less impact, shock, and thermal sensitivity
and avoids the issues of toxicity associated with trinitrotoluene.
The trinitrotoluene component of Tritonal is replaced with one or
more mononitro aromatic and/or dinitro aromatic melt-pourable
binders, such as dinitroanisole, which may be melt poured without
presenting the toxicity drawbacks experienced with the use of TNT.
The melt-pourable binder may also be combined with a processing aid
selected from the group consisting of alkylnitroanilines and
arylnitroanilines. The composition also includes oxidizer
particles, which are preferably inorganic oxidizer particles, and a
reactive metallic fuel, such as aluminum.
Inventors: |
Doll; Daniel W.; (Ogden,
UT) ; Hanks; Jami M.; (Logan, UT) ; Allred;
Alan G.; (Brigham City, UT) ; Niles; John B.;
(Lake Hopatacong, NJ) |
Correspondence
Address: |
TRASKBRITT, P.C./ ALLIANT TECH SYSTEMS
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
27613871 |
Appl. No.: |
11/271359 |
Filed: |
November 9, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09893336 |
Jun 27, 2001 |
6964714 |
|
|
11271359 |
|
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Current U.S.
Class: |
149/19.3 |
Current CPC
Class: |
C06B 21/005 20130101;
C06B 33/08 20130101 |
Class at
Publication: |
149/19.3 |
International
Class: |
C06B 45/10 20060101
C06B045/10 |
Claims
1. A melt-pourable explosive composition comprising: from 30 weight
percent to 70 weight percent of an organic binder selected from the
group consisting of meta-nitrophenol, para-nitrophenol,
2-amino-4-nitrophenol, a mononitroaniline, a dinitroaniline, a
mononitronaphthalene, nitrotoluene and mixtures thereof; from 5
weight percent to 35 weight percent of at least one oxidizer; and
from 5 weight percent to 35 weight percent of at least one reactive
metallic fuel, wherein the melt-pourable explosive composition is
pourable at a temperature in a range of from 80.degree. C. to
115.degree. C.
2. The melt-pourable explosive composition of claim 1, wherein the
organic binder comprises a member selected from the group
consisting of ortho-nitroaniline, meta-nitroaniline,
para-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, and
mixtures thereof.
3. The melt-pourable explosive composition of claim 1, further
comprising at least one processing aid selected from the group
consisting of an N-alkyl-nitroaniline and an
N-aryl-nitroaniline.
4. The melt-pourable explosive composition of claim 3, wherein the
at least one processing aid comprises a member selected from the
group consisting of N-methyl-p-nitroaniline,
N-ethyl-p-nitroaniline, 4-nitrodiphenylamine, 2-nitrodiphenylamine,
and mixtures thereof.
5. The melt-pourable explosive composition of claim 1, further
comprising at least one processing aid selected from the group
consisting of N-alkyl nitroaniline and N-aryl-nitroaniline, the at
least one processing aid accounting for not more than 1 weight
percent of the melt-pourable explosive composition.
6. The melt-pourable explosive composition of claim 1, wherein the
at least one reactive metallic fuel comprises aluminum.
7. The melt-pourable explosive composition of claim 1, wherein the
at least one oxidizer is present in the melt-pourable explosive
composition in a single modal particle size distribution in a range
of from 5 microns to 50 microns, the at least one oxidizer
comprising from 15 weight percent to 20 weight percent of the
melt-pourable explosive composition.
8. The melt-pourable explosive composition of claim 1, wherein the
melt-pourable explosive composition undergoes an onset of thermal
decomposition at a temperature at least 55.5.degree. C. higher than
a temperature at which the melt-pourable explosive composition
becomes pourable.
9. The melt-pourable explosive composition of claim 1, wherein the
at least one oxidizer is at least one inorganic oxidizer.
10. The melt-pourable explosive composition of claim 1, wherein the
at least one oxidizer comprises a member selected from the group
consisting of ammonium perchlorate, strontium perchlorate, sodium
perchlorate, potassium perchlorate, ammonium nitrate, sodium
nitrate, strontium nitrate, potassium nitrate, copper nitrate,
hydroxylammonium nitrate, ammonium dinitramide, hydrazinium
nitroformate, and mixtures thereof.
11. The melt-pourable explosive composition of claim 1, wherein the
at least one oxidizer has an average particle size ranging from 3
microns to 60 microns.
12. The melt-pourable explosive composition of claim 1, wherein the
at least one oxidizer has an average particle size ranging from 5
microns to 20 microns.
13. The melt-pourable explosive composition of claim 1, wherein at
least 95 weight percent of the melt-pourable explosive composition
comprises a combination of the organic binder, the at least one
oxidizer, and the at least one reactive metallic fuel.
14. The melt-pourable explosive composition of claim 1, wherein at
least 99 weight percent of the melt-pourable explosive composition
comprises a combination of the organic binder, the at least one
oxidizer, and the at least one reactive metallic fuel.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of application Ser. No.
09/893,336, filed Jun. 27, 2001, pending.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to explosives and, in particular,
this invention relates to explosives that are melt-pourable and may
function as excellent replacements for Tritonal. In a currently
preferred aspect, this invention relates to Tritonal replacement
compositions that exhibit similar melting characteristics,
comparable energetic performance, and either comparable or reduced
shock and thermal sensitivities to Tritonal. This invention also
relates to mortars, grenades, artillery, warheads, and
antipersonnel mines containing the melt-pourable Tritonal
replacement compositions.
[0004] 2. State of the Art
[0005] The melt-pourable explosive composition Tritonal usually
consists of 60-80 weight percent 2,4,6-trinitrotoluene (TNT) and
20-40 weight percent aluminum (Al). Tritonal has been used in a
wide array of military applications, although perhaps its most
frequent use is as a general bomb fill. One of the reasons for the
wide acceptance of Tritonal is that its binder component, TNT, has
a relative low melting point of 81.degree. C., which makes Tritonal
suitable for pouring into shells or casings of munitions.
[0006] However, Tritonal has several drawbacks attributable to its
TNT binder. One of the most prominent of these drawbacks is the
toxicity of TNT. During synthesis of TNT, undesirable isomers are
produced. Without wishing to be bound by any theory, it is believed
that meta isomers produced during the nitration of toluene react
with the sodium sulfite to produce water-soluble, sulfated
nitrotoluene that is red and highly toxic. Waste streams containing
these isomers are known as red and pink water and are considerably
toxic and hazardous to workers and the environment. Consequently,
stringent domestic environmental regulations have been imposed to
protect worker safety and prevent against adverse ecological impact
caused by the waste streams. However, waste stream cleanup is
laborious and expensive. These regulations and safety precautions
have also increased manufacturing costs and slowed production
rates, thereby making Tritonal and TNT production largely
uneconomical and leading to cessation of domestic TNT production by
most, if not all, domestic manufacturers.
[0007] The generation of undesirable isomers during TNT synthesis
has the additional drawback of increasing the exudation of TNT from
the ordnance. Many isomers generated during TNT synthesis have
melting points lower than that of TNT. These isomers tend to exude
under high storage temperature requirements, such as about
74.degree. C. (165.degree. F.). The exudation of TNT isomers from
Tritonal raises concerns that the isomers might enter into areas of
munitions that are not designed for exposure to energetic
materials. In such an event, the sensitivity, vulnerability, and
ability to handle and transport the munitions safely may be
compromised.
BRIEF SUMMARY OF THE INVENTION
[0008] Accordingly, the present invention provides a Tritonal
replacement composition that exhibits comparable energetic and
pouring properties to Tritonal, in particular, similar energies of
detonation and melting points for melt-pouring procedures, but may
be produced without as severe toxicity issues as encountered in TNT
production and substantially without undesirable isomers that
substantially lower the melting point of TNT and cause
exudation.
[0009] The present invention also provides a Tritonal replacement
that exhibits energetic and pouring properties comparable to
Tritonal but increases process safety by exhibiting substantially
reduced shock sensitivity and/or either comparable or reduced
thermal sensitivity compared to Tritonal. For example, reduced
sensitivity of the Tritonal replacement may mean a lower
vulnerability to physical and thermal stimuli such as, for example,
bullet and fragment impact, fast and slow cook-off, and/or
sympathetic denotation.
[0010] In accordance with this invention as embodied and broadly
described in this document, according to a first aspect of this
invention, there is provided a melt-pourable explosive composition
comprising 30 weight percent to 70 weight percent of one or more
organic binders selected from the group consisting of mononitro
aromatics and dinitro aromatics, 5 weight percent to 35 weight
percent of one or more oxidizer, and 5 weight percent to 35 weight
percent of one or more reactive metallic fuels. The aromatic binder
or collection of aromatic binders exhibits an energy of detonation
that is lower than TNT and collectively has a total melting point
in a range of 80.degree. C. to 115.degree. C. The melt-pourable
explosive composition is formulated to become melt-pourable at a
temperature in a range of 80.degree. C. to 115.degree. C.
[0011] In accordance with a second aspect of this invention, a
melt-pourable explosive composition comprises 30 weight percent to
70 weight percent of one or more organic binders selected from the
group consisting of mononitro aromatics and dinitro aromatics, 5
weight percent to 35 weight percent of one or more inorganic
oxidizers, and 5 weight percent to 35 weight percent of one or more
reactive metallic fuels, preferably aluminum. The organic binder or
collection of organic binders exhibits a total energy of detonation
lower than TNT and collectively has a total melting point in a
range of 80.degree. C. to 115.degree. C. The inorganic oxidizer(s)
preferably comprise at least one member selected from the group
consisting of perchlorates and nitrates and preferably have an
average particle size of 3 microns to 60 microns, more preferably 5
microns to 20 microns. It is still more preferable that the
mononitro/dinitro aromatic compound(s), the inorganic oxidizer(s),
and the metallic fuel(s) collectively account for at least 95
weight percent, more preferably at least 99 weight percent of the
total weight of the explosive composition. The composition is
preferably essentially free of TNT. As in the case of the first
aspect, in this second aspect, the melt-pourable explosive
composition is formulated to become melt-pourable at a temperature
in a range of 80.degree. C. to 115.degree. C.
[0012] In accordance with this invention, a fundamental and
well-accepted component of Tritonal, 2,4,6-trinitrotoluene, is
replaced with one or more aromatic binders, each preferably having
one or two nitro groups, more preferably nitrocarbon (C--NO.sub.2)
moieties, and an oxidizer, preferably an inorganic oxidizer. It has
been discovered that mononitro and dinitro aromatics such as
dinitroanisole may be melt-poured without presenting the same
degree of the toxicity drawbacks experienced with the use of TNT.
Additionally, many mononitro and dinitro aromatics are lower in
cost and more widely available than TNT. Mononitro and dinitro
aromatics are less detonable than trinitrated aromatics. Therefore,
the mononitro and dinitro aromatics do not require the explosive
transportation, storage, and packaging infrastructure that
trinitrated compounds, such as TNT, mandate.
[0013] Generally, the use of mononitro and dinitro aromatics in
place of TNT in the Tritonal formulation has been disfavored (if
not overlooked) in the melt-pouring art due to their low energetic
oxygen content compared to TNT. This drawback is overcome by the
addition of oxidizer particles to the melt-pourable Tritonal
replacement composition. The oxidizer particles are preferably
inorganic and preferably have relatively fine particle sizes. The
oxidizer particles compensate for the energy loss experienced by
the replacement of TNT with the less energetic mononitro and/or
dinitro aromatic melt-pourable binders.
[0014] Additionally, the different melting points that mononitro
and dinitro aromatics possess compared to TNT have also disfavored
the melt-pourable binder substitution. Melt pouring requires
heating of the binder to a temperature higher than its melting
point, so that the binder may be mixed with the energetic filler,
which is typically at ambient temperature, and poured by melting. A
typical and useful melting point range for the melt or pour process
is 80.degree. C. to 115.degree. C. However, melt-pourable Tritonal
replacement compositions should not be heated close to or above
their exothermic decomposition temperatures, because exothermic
decomposition may cause the Tritonal replacement composition to
ignite automatically and generate an exothermic deflagration or
explosion. Preferably, a relatively wide "safety margin" is present
between the melt temperature of the Tritonal replacement
composition and the temperature at which the composition
experiences an onset of exothermic decomposition. TNT has a melting
point of about 80.9.degree. C. and is believed to experience an
onset of exothermic decomposition at about 185.degree. C., giving a
relatively wide safety margin between the binder melting
temperature and the autoignition temperature. On the other hand,
many mononitro and dinitro aromatics have melting points exceeding
that of TNT, narrowing the safety margin for melt pouring. For
example, dinitroanisole has a melting point of 94.degree. C.
[0015] This drawback may be overcome by adding a processing aid to
the melt-pourable Tritonal replacement composition. The processing
aid is preferably also a mononitro or dinitro aromatic and, more
preferably, is selected from the group consisting of
alkylnitroanilines and arylnitroanilines. The processing aid lowers
the overall melting temperature of the energetic composition,
preferably into a range of from 80.degree. C. to 115.degree. C.,
while preferably raising the onset of the exothermic decomposition
temperature, preferably to at least 55.degree. C. higher than the
melting temperature to widen the safety margin.
[0016] This invention is also directed to ordnances and munitions
in which the melt-pourable Tritonal replacement composition of this
invention may be used, including, by way of example, mortars,
grenades, artillery shells, warheads, and antipersonnel mines.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Reference will now be made in detail to the presently
preferred embodiments and methods of the invention. It should be
noted, however, that the invention in its broader aspects is not
limited to the specific details, representative devices and
methods, and illustrative examples shown and described in this
section in connection with the preferred embodiments and methods.
The invention according to its various aspects is particularly
pointed out and distinctly claimed in the attached claims read in
view of this specification and appropriate equivalents.
[0018] It is to be noted that, as used in the specification and the
appended claims, the singular forms "a," "an," and "the" include
plural referents unless the context clearly dictates otherwise.
[0019] Generally, the melt-pourable binder or binders constitute
from 30 weight percent to 70 weight percent, more preferably from
40 weight percent to 60 weight percent, of the total weight of the
Tritonal replacement composition. It is preferred that the binder
or binders include nitrocarbon (C--NO.sub.2) moieties, although the
nitro moieties may include nitramines (N--NO.sub.2). Exemplary
melt-pourable binders suitable for this invention include
mononitro-substituted and dinitro-substituted phenyl alkyl ethers
having the following formula:
##STR00001##
wherein one or two members selected from R.sub.1, R.sub.2, R.sub.3,
R.sub.4, and R.sub.5 are nitro (--NO.sub.2) groups, the remaining
of R.sub.1 to R.sub.5 are the same or different and are preferably
selected from --H, --OH, --NH.sub.2, NR.sub.7R.sub.8, an aryl
group, or an -alkyl group (such as methyl), R.sub.6 is an alkyl
group (preferably a methyl, ethyl, or propyl group), R.sub.7 is
hydrogen or an alkyl or aryl group, and R.sub.8 is hydrogen or an
alkyl group.
[0020] 2,4-dinitroanisole (2,4-dinitrophenyl-methyl-ether) and
2,4-dinitrophenetole (2,4-dinitrophenyl-ethyl-ether) are examples
of dinitro-substituted phenyl alkyl ethers suitable for use in the
present melt-pourable explosive composition, while
4-methoxy-2-nitrophenol is an example of a preferred
mononitro-substituted phenyl alkyl ether.
##STR00002##
[0021] As referred to herein, aromatics include phenols and aryl
amines. For example, mononitro and dinitro aromatic binders
suitable for use with this invention include nitrophenols, such as
meta-nitrophenol, para-nitrophenol, and 2-amino-4-nitrophenol;
dinitrophenols, such as 2,4-dinitrophenol and 4,6-dinitro-o-cresol;
nitrotoluene and dinitrotoluenes, such as 2,4-dinitrotoluene;
mononitroanilines, such as ortho-nitroaniline, meta-nitroaniline,
and para-nitroaniline; and dinitroanilines, such as
2,4-dinitroaniline and 2,6-dinitroaniline. As referred to herein,
aromatics also include polycyclic benzenoid aromatics, such as
mononitronaphthalenes and dinitronaphthalenes (e.g.,
1,5-dinitronapthalene). It is also within the scope of the
invention to use one or more heterocyclic binders, such as
4-chloro-7-nitrobenzofurazon, 5-nitro-2-furaldehyde diacetate,
5-nitro-isoquinoline, and methyl-5-nitro-2-furoate.
[0022] Other mononitro and dinitro aromatic binders that may be
considered include the following: [0023] 4-nitrobenzaldehyde;
[0024] 4-nitroacetophenone; [0025] 2-nitrobenzonitrile; [0026]
3-nitrobenzophenone; [0027] 4-nitrobenzyl alcohol; [0028]
4-nitrobenzyl bromide; [0029] 5-nitroisoquinoline; [0030]
4-nitrophenyl acetate; [0031] 2-nitrophenyl acetonitrile; [0032]
3-nitrophenyldisulfide; [0033] 4-nitrophenyl chloroformate; [0034]
1-(2-nitrophenyl)-1,2-ethanoldiol; [0035] 4-nitrophenyl
trimethylacetate; [0036] 8-nitroquinoline; [0037]
2-nitro-4-(trifluoromethyl)aniline; [0038]
4-chloro-3-nitroacetophenone; [0039]
methyl-3-hydroxy-4-nitrobenzoate; [0040] methyl-3-nitrobenzoate;
[0041] methyl-4-nitrobenzoate; [0042] 2-methyl-5-nitrobenzonitrile;
and [0043] 3-methyl-4-nitrobenzonitrile.
[0044] The above examples of representative binders are not meant
to be exhaustive. Rather, other aromatic binders may be suitable
for this invention. Suitability of the binder is determined by
balancing of various features and binder characteristics. For
example, the binder preferably may be characterized by several or
all of the following attributes: nontoxic, nonhygroscopic,
nonmutagenic, light insensitive, air insensitive, noncorrosive, not
a lachrymator, moisture insensitive, temperature insensitive
between -54.degree. C. and 140.degree. C., melting point between
80.degree. C. and 115.degree. C., and viscosity of lower than 0.64
kp (kilopoise), more preferably lower than 0.16 kp within the pour
temperature range of 80.degree. C. to 115.degree. C.
[0045] The mononitro and dinitro aromatics generally have a much
lower toxicity than TNT, particularly when the aromatics do not
contain --OH and/or --NH.sub.2 functionalities. Thus, in many
instances, the use of mononitro and dinitro aromatics often
simplifies handling and reduces the costs associated with
manufacturing the Tritonal replacement explosive.
[0046] The processing aid of this invention preferably is a
mononitro or dinitro aromatic and, more preferably, is one or more
N-alkyl-nitroanilines and/or N-aryl-nitroanilines having the
following formula:
##STR00003##
wherein R.sub.6 is hydrogen, R.sub.7 is an unsubstituted or
substituted hydrocarbon (e.g., straight-chain alkyl, branched
alkyl, cyclic alkyl, or aryl group), at least one of R.sub.1 to
R.sub.5 is a nitro group, the remaining of R.sub.1 to R.sub.5 are
the same or different and are preferably selected from --H, --OH,
--NH.sub.2, NR.sub.8R.sub.9, an aryl group, or an -alkyl group
(such as methyl), R.sub.8 is hydrogen or an alkyl or aryl group,
and R.sub.9 is hydrogen or an alkyl group. Exemplary
N-alkyl-nitroaniline processing aids include the following:
##STR00004##
[0047] Examples of aryl-nitroaniline processing aids include the
following:
##STR00005##
[0048] The concentration of the processing aid is selected in order
to widen the "safety margin" at which the melt-pourable Tritonal
replacement composition may be melt poured without significant
threat of an onset of exothermic decomposition and auto-ignition of
the Tritonal replacement composition. The processing aid preferably
acts to lower the melting point of the composition towards (but not
necessarily to) its eutectic point. By controlling the amount of
the processing aid, the melting point of the mixture of binder and
processing aid may be adjusted into a range of 80.degree. C. to
115.degree. C. that generally characterizes melt-pourable
materials. More preferably, the melting point is adjusted to
80.degree. C. to 110.degree. C., more preferably 80.degree. C. to
90.degree. C. Simultaneously, the processing aid preferably raises
the temperature at which the composition experiences an onset of
exothermic decomposition, widening the safety margin between the
melting temperature and the auto-ignition temperature of the
Tritonal replacement composition.
[0049] The concentration of the processing aid may be selected by
taking into account the amount of melt-pourable binder in the
overall melt-pourable Tritonal replacement composition, the purity
of the binder, and the nitrogen content of the binder. Generally,
the Tritonal replacement composition may include, for example, from
about 0.15 weight percent to about 1 weight percent of the
processing aid based on the total weight of the Tritonal
replacement composition. Using more than about 1 weight percent of
the processing aid may lower the pour temperature of the
melt-pourable Tritonal replacement composition to below about
80.degree. C.
[0050] Representative inorganic oxidizers suitable for the present
melt-pourable Tritonal replacement composition include
perchlorates, such as potassium perchlorate, sodium perchlorate,
strontium perchlorate, and ammonium perchlorate; and nitrates, such
as potassium nitrate, sodium nitrate, strontium nitrate, ammonium
nitrate, copper nitrate (Cu.sub.2(OH).sub.3NO.sub.3), and
hydroxylammonium nitrate (HAN); ammonium dinitramide (ADN); and
hydrazinium nitroformate (HNF). Organic oxidizers having excess
amounts of oxygen available for oxidizing the binder may also be
used, although preferably the oxidizers consist of inorganic
compounds. Examples of suitable organic oxidizers include
nitramines, such as CL-20. In the event an organic oxidizer is used
in the melt-pourable explosive composition, the organic oxidizer is
preferably present in less than 20 weight percent, more preferably
less than 10 weight percent, still more preferably less than 5
weight percent, and most preferably no more than 1 weight percent
based on the total weight of the explosive composition.
[0051] The oxidizer particles preferably have particle diameters
of, on average, 3 microns to 60 microns, more preferably 5 microns
to 20 microns. It is possible to use bimodal distributions, such as
a combination of coarse particles (200 microns to 400 microns) and
fine particles (less than 20 microns). More preferred, however, is
a single modal distribution of 5 microns to 50 microns. In the
event that a single modal distribution in this particle size range
is selected, the content of inorganic oxidizer in the energetic
composition is preferably in a range of 15 weight percent to 20
weight percent.
[0052] Representative reactive metallic fuels that may be used in
this invention include one or more of the following: aluminum,
magnesium, boron, titanium, zirconium, and mixtures thereof. Of
these, aluminum is preferred. The particles may have an average
particle size of, for example, 3 microns to 60 microns and, more
preferably, 5 microns to 20 microns. The metallic fuel preferably
constitutes from 5 weight percent to 35 weight percent of the
Tritonal replacement composition and, more preferably, from 15
weight percent to 20 weight percent. Preferably, the inorganic
oxidizer and metallic fuel are present in a weight ratio of about
1:1.
[0053] Preferably, the melt-pourable Tritonal replacement
composition of this invention is substantially free of polymeric
binders conventionally found in pressable and extrudable energetic
materials, since an undue amount of these polymeric binders may
lower the energy (especially for nonenergetic polymer binders) and
reduce the melt pourability (by increasing the viscosity) of the
melt-pourable explosive.
[0054] A process of making the melt-pourable Tritonal replacement
composition will now be described in more detail below. It should
be understood that various modifications and alterations to the
process and equipment described below are possible and encompassed
by this invention.
[0055] The binder and optional processing aid are loaded into a
pressurized, steam-heated melt kettle having a surrounding jacket.
The kettle is heated to a temperature far enough above the melting
temperature of the binder and processing aid to prevent
solidification of the binder during the subsequent addition of
ambient-temperature particles, but not so high as to cause an onset
of exothermic decomposition. For example, the kettle may be heated
to from about 90.degree. C. to 100.degree. C., preferably
95.degree. C. The oxidizer and fuel are then added by metering,
i.e., adding the oxidizer and fuel either in stages or continuously
so as not to lower the temperature of the melt phase below its
melting temperature. Preferably, the oxidizer is added prior to the
fuel. Constant stirring is preferably performed throughout the mix
cycle. Stirring is preferably sufficiently rapid to wet the
oxidizer particles and achieve homogeneity in a relatively short
time period. The mixture is then poured or cast, usually into a
case of munitions or the like.
[0056] As mentioned above, the melt-pourable composition of
preferred aspects of this invention exhibits comparable energetic
and pouring properties to Tritonal but increases process safety by
exhibiting substantially reduced shock sensitivity compared to
Tritonal.
[0057] An indicator of thermal stability is the temperature at
which an explosive composition experiences an exotherm, or
exothermic decomposition. A test known as Stimulated Bulk
Autoignition Test, or SBAT, may be used to determine this
temperature. Essentially, the SBAT simulates the thermal response
of a large mass of energetic material using only a small quantity
of material. The test sample is placed in a Pyrex tube and
insulated, and then placed in metal blocks in an oven. An
identically insulated nonreactive sample, such as an aluminum
block, is placed in the oven alongside of the test sample for
temperature comparisons. The samples are heated from 38.degree. C.
(100.degree. F.) to 260.degree. C. (500.degree. F.) over a 16 hour
period at a rate of 13.3.degree. C./hr (24.degree. F./hr). The
temperatures of the energetic material and control are monitored
through thermocouples and recorded on a chart until the test is
complete. The reaction is recorded along with the onset
temperature, which is the temperature at which the data trace of
the energetic material first leaves the baseline, i.e., that of the
control.
[0058] Energetic materials with high autoignition temperatures are
desirable because they are less likely to explode or detonate when
exposed to elevated temperatures. The energetic composition of this
invention preferably experiences an onset of thermal decomposition
that is at least 55.degree. C., more preferably at least
100.degree. C., higher than the temperature at which the energetic
composition becomes melt-pourable.
[0059] One test for measuring shock sensitivity is known in the art
as the Large Scale Gap Test (LSGT), in which a test material is
placed into a metal tube on top of a witness plate. A predetermined
number of PMMA (polymethylmethacrylate) cards are placed between
the top of the metal tube and a booster material, which typically
consists of 50 wt % PETN (pentaerythritol tetranitrate) and 50 wt %
TNT (trinitrotoluene), available as Pentolite. The distance between
the booster and the metal tube is expressed in cards, where 1 card
is equal to 0.0254 cm (0.01 inch), such that 100 cards equal 2.54
cm (1 inch). A card gap measurement is the minimum number of cards
required to prevent the booster from detonating the explosive
sample, so that the sample does not blow a hole through the witness
plate. Thus, the lower the card value, the lower the shock
sensitivity.
[0060] The LSGT (or NOL Card Pipe Test) is more fully described in
Joint Technical Bulletin, Navy document number NAVSEA INST 8020.8B,
Air Force technical order 11A-1-47, Defense Logistics Agency
regulation DLAR 8220.1, and Army technical bulletin TB700-2.
[0061] Tritonal has a measured card gap value of 127. The explosive
composition of this invention preferably has a card gap value that
is less than 127, more preferably less than 105, and still more
preferably less than 85.
[0062] Energetic performance of an explosive may be evaluated
through use of calculated properties, such as total energy of
detonation, theoretical maximum density (TMD), detonation pressure,
shock velocity, cylinder expansion energy, and the like. These
properties may be calculated based on the software CHEETAH,
available through Lawrence Livermore National Laboratory of
Livermore, Calif. This software is well known and used in the art,
including by those having ordinary skill in the art of explosive
development.
[0063] Tritonal has a total energy of detonation of 12.9 kJ/cc. In
an especially preferred embodiment of this invention, the
melt-pourable explosive composition has a total energy of
detonation within 10 percent of 12.9 kJ/cc, i.e., 11.6 kJ/cc to
14.2 kJ/cc.
[0064] A measurable property for determining energetic performance
of an explosive is dent depth. Dent depth measurements are
conducted by placing a 350 gram sample in a metal tube, identical
to the one discussed above and used for the NOL card gap test,
having exposed ends. The metal tube sits on a 1018 steel plate
having a thickness of 5.08 cm (2 inches) and a width and height of
15.24.times.15.24 cm (6.times.6 inches), so that one of the ends of
the tube is in contact with the steel plate. A Pentolite booster is
placed on top of the metal tube and in operative association with
the sample. The explosive is detonated in the pipe by activating
the booster. The detonation products from the explosion form an
indentation in the steel plate. The depth of this indentation is
measured and recorded as the dent depth, which represents the
amount of work performed by the explosive.
[0065] The dent depth of Tritonal is about 0.793 cm (0.312 inch).
The dent depth of the explosive composition of this invention is
preferably within 10 percent of that of Tritonal, i.e., 0.713 cm to
0.872 cm.
EXAMPLES
[0066] The following examples illustrate embodiments that have been
made in accordance with the present invention. Also set forth are
comparative examples prepared for comparison purposes. The
inventive embodiments are not exhaustive or exclusive but merely
representative of the invention.
[0067] Unless otherwise indicated, all parts are by weight.
Example 1
[0068] In a pressurized, steam-heated melt kettle, dinitroanisole
(DNAN) and N-methyl-p-nitroaniline (MNA) were introduced and heated
above their melting temperatures and stirred until melted and
homogeneous. Fifty micron particles of ammonium perchlorate and
then 3 micron particles of aluminum were metered into the kettle
while maintaining constant stirring. The explosive composition was
then melt poured onto a flaker, cooled at room temperature, and
then broken into small flake-like solid pieces, nominally 0.64 cm
(0.25 inch) thick by 1.27.times.1.27 cm (0.5.times.0.5 inch). The
flakes were then remelted in the melt kettle and poured into the
ordnance. The explosive composition comprised 49.75 weight percent
DNAN, 0.25 weight percent MNA, 30 weight percent ammonium
perchlorate, and 20 weight percent aluminum. When tested, the
composition exhibited a dent depth of 0.808 cm, a card gap of less
than 90, and an exotherm of 207.degree. C.
Example 2
[0069] In a pressurized, steam-heated melt kettle, dinitroanisole
(DNAN) and N-methyl-p-nitroaniline (MNA) were introduced and heated
above their melting temperatures and stirred until melted and
homogeneous. Nine micron particles of ammonium perchlorate and 3
micron particles of aluminum were sequentially metered into the
kettle while maintaining constant stirring. The explosive
composition was then melt poured onto a flaker, cooled at room
temperature, and then broken into small flake-like solid pieces,
nominally 0.64 cm (0.25 inch) thick by 1.27.times.1.27 cm
(0.5.times.0.5 inch). The explosive composition comprised 49.75
weight percent DNAN, 0.25 weight percent MNA, 30 weight percent
ammonium perchlorate, and 20 weight percent. When tested, the
composition exhibited a dent depth of 0.876 cm, a card gap of 40,
and an exotherm of 209.degree. C.
Example 3
[0070] In a pressurized, steam-heated melt kettle, dinitroanisole
(DNAN) and N-methyl-p-nitroaniline (MNA) were introduced and heated
above their melting temperatures and stirred until melted and
homogeneous. Fifty micron particles of ammonium perchlorate and 20
micron particles of aluminum were metered into the kettle while
maintaining constant stirring. The explosive composition was then
melt poured onto a flaker, cooled at room temperature, and then
broken into small flake-like solid pieces, nominally 0.64 cm (0.25
inch) thick by 1.27.times.1.27 cm (0.5.times.0.5 inch). The
explosive composition comprised 49.75 weight percent DNAN, 0.25
weight percent MNA, 30 weight percent ammonium perchlorate, and 20
weight percent aluminum. When tested, the composition exhibited a
dent depth of 0.785 cm, a card gap of 58, and an exotherm of
218.degree. C.
Example 4
[0071] In a pressurized, steam-heated melt kettle, dinitroanisole
(DNAN) and N-methyl-p-nitroaniline (MNA) were introduced and heated
above their melting temperatures and stirred until melted and
homogeneous. Nine micron particles of ammonium perchlorate and 20
micron particles of aluminum were metered into the kettle while
maintaining constant stirring. The explosive composition was then
melt poured onto a flaker, cooled at room temperature, and then
broken into small flake-like solid pieces, nominally 0.64 cm (0.25
inch) thick by 1.27.times.1.27 cm (0.5.times.0.5 inch). The
explosive composition comprised 49.75 weight percent DNAN, 0.25
weight percent MNA, 30 weight percent ammonium perchlorate, and 20
weight percent aluminum. When tested, the composition exhibited a
dent depth of 0.84 cm, a card gap of 60, and an exotherm of
218.degree. C.
Example 5
[0072] In a pressurized, steam-heated melt kettle, dinitroanisole
(DNAN) and N-methyl-p-nitroaniline (MNA) were introduced and heated
above their melting temperatures and stirred until melted and
homogeneous. Fifty micron particles of ammonium perchlorate and 3
micron particles of aluminum were metered into the kettle while
maintaining constant stirring. The explosive composition was then
melt poured onto a flaker, cooled at room temperature, and then
broken into small flake-like solid pieces, nominally 0.64 cm (0.25
inch) thick by 1.27.times.1.27 cm (0.5.times.0.5 inch). The
explosive composition comprised 59.75 weight percent DNAN, 0.25
weight percent MNA, 17 weight percent ammonium perchlorate, and 23
weight percent aluminum. When tested, the composition exhibited a
dent depth of 0.792 cm, a card gap of less than 50, and an exotherm
of 242.degree. C.
Example 6
[0073] In a pressurized, steam-heated melt kettle, dinitroanisole
(DNAN) and N-methyl-p-nitroaniline (MNA) were introduced and heated
above their melting temperatures and stirred until melted and
homogeneous. Fifty micron particles of ammonium perchlorate and 20
micron particles of aluminum were sequentially metered into the
kettle while maintaining constant stirring. The explosive
composition was then melt poured onto a flaker, cooled at room
temperature, and then broken into small flake-like solid pieces,
nominally 0.64 cm (0.25 inch) thick by 1.27.times.1.27 cm
(0.5.times.0.5 inch). The explosive composition comprised 59.75
weight percent DNAN, 0.25 weight percent MNA, 17 weight percent
ammonium perchlorate, and 23 weight percent aluminum. When tested,
the composition exhibited a dent depth of 0.747 cm, a card gap of
69, and an exotherm of 204.degree. C.
[0074] Each of Examples 1 and 3-6 exhibited dent depths falling
within 10 percent of the dent depth of Tritonal. Example 2 was
outside the range by a negligible amount of 0.004 cm. Examples 1-6
also exhibited card gaps well below that of Tritonal.
[0075] The foregoing detailed description of the preferred
embodiments of the invention has been provided for the purpose of
explaining the principles of the invention and its practical
application, enabling others skilled in the art to understand the
invention for various embodiments and with various modifications as
are suited to the particular use contemplated. The foregoing
detailed description is not intended to be exhaustive or to limit
the invention to the precise embodiments disclosed. Modifications
and equivalents will be apparent to practitioners skilled in this
art and are encompassed within the spirit and scope of the appended
claims.
* * * * *