U.S. patent application number 09/735643 was filed with the patent office on 2002-08-29 for extrudable black body decoy flare compositions.
This patent application is currently assigned to CORDANT TECHNOLOGIES INC.. Invention is credited to Lester, Dean M., Nielson, Daniel B..
Application Number | 20020117242 09/735643 |
Document ID | / |
Family ID | 21856715 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020117242 |
Kind Code |
A1 |
Nielson, Daniel B. ; et
al. |
August 29, 2002 |
EXTRUDABLE BLACK BODY DECOY FLARE COMPOSITIONS
Abstract
An extrudable black body decoy flare composition which, when
combusted, provided black body radiation is disclosed. The
compositions generally include from about 40% to about 70% metal
such as magnesium or aluminum, from about 10% to about 40%
polytetrafluoroethylene, and from about 8% to about 30% binder.
Important to the operation of the invention is the production of
carbon upon combustion of the composition. Accordingly,
polyaromatic thermoplastics, such as polystyrene and dimethyl
phthalate, serve as the binder.
Inventors: |
Nielson, Daniel B.; (Brigham
City, UT) ; Lester, Dean M.; (Brigham City,
UT) |
Correspondence
Address: |
Sullivan Law Group
Suite 120
5060 North 40th Street
Phoenix,
AZ
85018
US
|
Assignee: |
CORDANT TECHNOLOGIES INC.
|
Family ID: |
21856715 |
Appl. No.: |
09/735643 |
Filed: |
December 14, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09735643 |
Dec 14, 2000 |
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09311298 |
May 14, 1999 |
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09311298 |
May 14, 1999 |
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PCT/US97/19984 |
Nov 14, 1997 |
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60030922 |
Nov 15, 1996 |
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Current U.S.
Class: |
149/19.3 |
Current CPC
Class: |
C06C 15/00 20130101;
C06B 27/00 20130101 |
Class at
Publication: |
149/19.3 |
International
Class: |
C06B 045/10 |
Claims
1. A method of producing a black body decoy flare, the method
comprising the steps of: a. preparing a mixture comprising
magnesium, polytetrafluoroethylene, and a polyaromatic
thermoplastic binder; and b. extruding the mixture into a flare
grain form.
2. A method of producing a black body decoy flare as defined in
claim 1, wherein the polyaromatic thermoplastic binder comprises a
styrene, said styrene being polystyrene or acrylonitrile butadiene
styrene, and a plasticizer selected from the group consisting of
dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl
phthalate, poly terephthalate, poly ethyl terephthalate, para or
ortho substituted chloropolystyrenes, nitropolystyrenes,
polyacenaphthalene, polyvinylcarbozol, polyvinylfluorene, .alpha.
methylpolystyrenes, .alpha. chloropolystyrenes, .alpha.
alkylpolystyrenes, copolymers of polystyrene, and mixture
thereof.
3. A method of producing a black body decoy flare as defined in
claim 1, wherein the polyaromatic thermoplastic binder comprises
polystyrene and dimethyl phthalate.
4. A method of producing a black body decoy flare as defined in
claim 1, wherein the preparation of the mixture is substantially
free of solvents.
5. A method of producing a black body decoy flare as defined in
claim 1, wherein the magnesium is present from about 40% to about
70% by weight.
6. A method of producing a black body decoy flare as defined in
claim 1, wherein the polytetrafluoroethylene is present from about
10% to about 40% by weight.
7. A method of producing a black body decoy flare as defined in
claim 1, wherein the polyaromatic thermoplastic is present from
about 8% to about 30% by weight.
8. A method of producing a black body decoy flare as defined in
claim 1, wherein a plasticizer is present at up to 80 weight
percent of the polyaromatic thermoplastic binder.
9. A method of producing a black body decoy flare, the method
comprising the steps of: a. preparing a mixture comprising
magnesium present from about 40% to about 70% by weight,
polytetrafluoroethylene present from about 10% to about 40% by
weight, and a polyaromatic thermoplastic binder present from about
8% to about 30% by weight; and b. extruding the mixture into a
flare grain.
10. A method of producing a black body decoy flare as defined in
claim 9, wherein the polyaromatic thermoplastic binder is selected
from the group consisting of polystyrene, dimethyl phthalate, or
mixtures thereof.
11. A method of producing a black body decoy flare as defined in
claim 9, wherein the mixture is substantially free of solvents.
12. A method of producing a black body decoy flare as defined in
claim 9, wherein dimethyl phthalate is present at up to 80 weight
per cent of the polyaromatic thermoplastic binder.
13. An extrudable black body decoy flare composition comprising:
from about 40% to about 70% by weight magnesium; from about 10% to
about 40% by weight polytetrafluoroethylene; and from about 8% to
about 30% by weight polyaromatic thermoplastic binder.
14. An extrudable black body decoy flare composition as defined in
claim 13, wherein the polyaromatic thermoplastic binder comprises:
a styrene present from about 20 to about 100 weight percent of the
binder, said styrene being polystyrene or acrylonitrile butadiene
styrene; and a plasticizer present at up to about 80 weight percent
of the binder, said plasticizer being selected from the group
consisting of dimethyl phthalate, diethyl phthalate, dibutyl
phthalate, dioctyl phthalate, poly terephthalate, poly ethyl
terephthalate, para or ortho substituted chloropolystyrenes,
nitropolystyrenes, polyacenaphthalene, polyvinylcarbozol,
polyvinylfluorene .alpha. methylpolystyrenes, .alpha.
chloropolystyrenes, .alpha. alkylpolystyrenes, copolymers of
polystyrene, and mixtures thereof.
15. An extrudable black body decoy flare composition as defined in
claim 13, wherein the composition is substantially free of
fluorinated ethylene propylene copolymers.
16. An extrudable black body decoy flare composition as defined in
claim 13, wherein the composition is substantially free of
polyolefins.
17. A black body decoy flare composition comprising: from about 40%
to about 70% by weight magnesium, from about 10% to about 40% by
weight polytetrafluoroethylene; and from about 8% to about 30% by
weight binder; wherein the binder comprises polystyrene present
from about 20 to about 100 weight percent of the binder and
dimethyl phthalate present at up to 80 weight percent of the
binder.
18. An extrudable black body decoy flare composition as defined in
claim 17, wherein the composition is substantially free of
fluorinated ethylene propylene copolymers.
19. An extrudable black body decoy flare composition as defined in
claim 17, wherein the composition is substantially free of
polyolefins.
Description
FIELD OF THE INVENTION
[0001] The present invention is related to extrudable black body
decoy flare compositions that dramatically improve processibility
while maintaining the infrared radiation intensity of conventional
decoy flare compositions. More particularly, the present invention
is related to such compositions that are also capable of serving as
a heat-seeking missile decoys for aircraft, tanks, and trucks.
BACKGROUND OF THE INVENTION
[0002] Aircraft-launched flares of various types have been used for
many purposes. For example, it is often desirable to light a
particular area at night. A flare may be used to produce light for
search and rescue operations or for various military purposes. It
is also well known to employ flares as a decoy tactic. That is, a
flare may be used to cover the path of an aircraft through a
particular area. One common situation is when the aircraft is
encountering anti-aircraft fire. The use of a flare can distract
the anti-aircraft fire sufficiently to allow the aircraft to
proceed safely on its course.
[0003] Anti-aircraft missiles are commonly used in modern warfare.
Such missiles may be launched from the ground or they may be
launched from another aircraft. Many of this type of missile are
designed to seek particular types of emissions characteristic of
aircraft. Such emissions often take the form of heat and infrared
light. Thus, "heat-seeking" missiles are often used against
aircraft.
[0004] In this context, it is desirable to provide a flare that
produces the type of emissions sought by the missile in order to
distract the missile from the actual aircraft. Thus, flares that
emit heat and infrared are well known and have been used for many
years.
[0005] Conventional decoy flare materials have been a combination
of magnesium and polytetrafluoroethylene (PTFE or "Teflon.RTM.").
These compositions are known widely as magnesium-Teflon.RTM. flare
compositions. These formulations produce a black body emission
spectrum which has been used as a decoy for jet engines.
[0006] Current methods of producing magnesium-PTFE flare
compositions require the use of solvents that are ozone-depleting
or flammable. In one currently used method, the composition is
produced by depositing the binder on the pyrotechnic mixture
through solvent loss using, for example, acetone or methyl-ethyl
ketone. The mixture is dried, after which it is consolidated
through pressing or extrusion operations. In a second method, a
binder such as Viton A.RTM., which is a fluorinated ethylene
propylene copolymer sold by DuPont, is deposited on the pyrotechnic
mixture through polymer precipitation methods using hexane and
acetone. The dried pyrotechnic powder is then consolidated through
pressing or extrusion operations. This method requires large
quantities of acetone and hexane, which are flammable, to carry the
Viton A.RTM. binder. The solvents used in these methods have been
the source of many fires during the processing of decoy mixes.
[0007] An additional problem with conventional magnesium-PTFE
compositions is that they are very sensitive. Moreover, such
compositions require extensive operator exposure during mixer
dumping, oven loading, and material break-up operations.
Traditional methods have proven disadvantageous, as the processing
and handling of conventional flare compositions is dangerous and
has resulted in many injuries and even deaths. An additional
problem with conventional magnesium-PTFE compositions is that such
compositions typically require expensive ingredients such as
specialty binders and spherical magnesium.
[0008] Accordingly, it would be a significant advancement in the
art to provide compositions and methods of producing decoy flares
that overcame the identified problems of producing conventional
flares. In particular, it would be an advancement to provide flare
compositions that eliminate the safety risks associated with
handling unconsolidated pyrotechnic powder. It would also be an
advancement in the art to provide flare compositions and methods of
production that eliminate ozone-depleting or flammable solvent
emissions that accompany production. It would be a further
advancement in the art to provide such flare compositions that
could be manufactured using traditional press/extrusion techniques
or using a twin screw extruder.
[0009] It would also be an advancement to provide such compositions
that exceed the radiometric performance of conventional
magnesium-PTFE infrared decoy flare compositions. It would be a
further advancement in the art to provide such compositions that
cost less than conventional flare compositions to produce.
[0010] Such compositions and methods for producing decoy flares are
disclosed and claimed herein.
SUMMARY AND OBJECTS OF THE INVENTION
[0011] The present invention is related to new compositions that
produce black body radiation when ignited. A black body radiator is
generally defined as a material that radiates over a broad
spectrum, as described by the following equation:
M=.epsilon..sigma.T.sup.4 Wcm.sup.-2
[0012] where:
[0013] .epsilon.=emissivity
[0014] T=absolute temperature
[0015] .sigma.=Stefan-Boltzmann constant
[0016] M=exitance
[0017] The novel extrudable black body decoy flare compositions
defined herein function in a manner similar to conventional
magnesium-PTFE infrared decoy flares: heat produced by the flare
decoys the heat-seeking missile away from the target. The principle
difference between a conventional magnesium-PTFE flare composition
and this new flare composition is that the compositions of the
present invention utilize polyaromatic thermoplastics rather than
solvent deposition fluor-polymers (e.g., Viton A.RTM.) or
poly-olefins as the binder component. The polyaromatic
thermoplastic facilitates the processing of the flare material via
extrusion without the use of solvents.
[0018] The primary reaction products of a conventional
magnesium-PTFE flare are solid carbon and liquid magnesium
fluoride. The high emissivities of these reaction products result
in an efficient black body radiating plume. In contrast, the
polyaromatic thermoplastic of the present invention pyrolyzes
during flare combustion to produce carbon particles. This pyrolysis
of the binder results in an efficient black body radiator in the
exhaust plume.
[0019] The present invention relates to the use of polyaromatic
thermoplastic compounds such as polystyrene and dimethyl phthalate
as the binder in a black body decoy flare. The thermoplastic
compounds enable a magnesium-PTFE flare composition to be extruded
without the use of solvents. In addition, the aromatic rings are
reduced to carbon in the fuel rich composition, producing an ideal
incandescent species that augments the signature.
[0020] Pyrotechnic art teaches that the radiometric output of
traditional flare formulations is directly tied to the binder
content of the flare. Low binder levels (4%) produce the greatest
radiometric output and high binder levels (8%) produce lower
radiometric output. One traditional method for augmenting the
radiometric output of a flare formulation when higher binder levels
are required is to use a fluorocarbon (such as Viton A.RTM.) or
high energy binder (e.g., a polyoxetane binder such as BAMO/AMMO).
This increases the oxidative potential of the binder component.
Therefore, it was unexpected that high polyaromatic binder (16%)
content flares produced an increased output when compared to a
standard magnesium-PTFE flare.
[0021] Some of the primary benefits of the present invention are
enhanced processibility, increased performance, elimination of
solvents, and reduction in material and labor costs. Extrusion of
flares containing polyaromatic thermoplastic binders increases
processibility over traditional pressed flares by eliminating oven
cure time, increasing processing line speed, decreasing labor
costs, and significantly reducing the risk to operators from
unconsolidated pyrotechnic exposure. The radiometric output of the
flare is improved over traditional pressed magnesium-PTFE flares.
The use of thermoplastic binders eliminates the need to use
solvents to process the flare compositions. The solvents
traditionally used are ozone-depleting or flammable. Elimination of
solvents increases the environmental friendliness of the process
and safety to operators. Polyaromatic thermoplastics are commonly
used in the manufacture of a wide variety of products ranging from
coffee cups to children's toys. These materials are far less
expensive than halocarbons such as Viton A.RTM. or specialty
binders commonly used in the manufacture of infrared flares.
[0022] Flares manufactured using compositions of the present
invention are more easily demilitarized than flares manufactured
using conventional compositions. Compositions utilizing
polyaromatic thermoplastic binders may be removed from the flare
casing by heating. This is to be contrasted with conventional flare
materials which can be demilitarized only by complex and expensive
mechanical or chemical processes.
[0023] These and other objects and advantages of the invention will
become apparent upon reading the following detailed description and
appended claims, and upon reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a graph illustrating the radiometric data
generated by burning a pressed baseline magnesium-PTFE decoy flare
composition.
[0025] FIG. 2 is a graph illustrating the radiometric data
generated by burning a composition within the scope of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The present invention provides improved extrudable black
body decoy flare compositions and methods of use. The compositions
are capable of producing significant amounts of black body
radiation. At the same time, the compositions avoid some of the
problems encountered with conventional flare compositions,
including the handling of unconsolidated pyrotechnic powder and
solvent emissions. Additionally, flares produced according to the
method of the present invention cost less to produce than
conventional flares.
[0027] Accordingly, the compositions of the present invention
comprise a metal fuel, PTFE as the main oxidizer, and a
polyaromatic thermoplastic binder. Other additives, including
curing agents and burn rate modifiers, are used as is known in the
art to tailor other characteristics of the composition. In summary,
the present invention provides new and useful extrudable black body
flare compositions.
[0028] A typical flare composition according to the present
invention includes the following components in the following
percentages by weight:
1 Ingredient Weight Percent Magnesium 40 to 70 Teflon .RTM. 10 to
40 Polyaromatic Thermoplastic Binder 8 to 30 Plasticizer 0 to
24
[0029] Magnesium is the fuel of choice, although other metals, such
as aluminum and mixtures of aluminum and magnesium, could also be
used. Magnesium is easily ignited and has a strong capability to
after-burn in the plume behind the flare. This after-burning is
important to augment the infrared signature of the plume without
increasing the combustion chamber's internal temperature. Magnesium
used in the compositions of the present invention may be chipped,
spherical, or a mixture of chipped and spherical. Chipped magnesium
is less expensive than spherical magnesium.
[0030] It is presently preferred that the metal be in the range of
from about 40% to about 70% by weight. Most formulations falling
within the scope of the present invention will have metal in the
range of from about 45% to about 65% by weight. Generally, good
results have been obtained with formulations in which magnesium is
present at from about 64% to about 66% by weight.
[0031] As in conventional magnesium-PTFE flare compositions, PTFE
("Teflon.RTM.") is the oxidizer in compositions of the present
invention. It is presently preferred that PTFE be present in the
range of from about 10% to about 40% by weight. Most formulations
falling within the scope of the present invention will have PTFE in
the range of from about 20% to about 35% by weight. Generally, good
results have been obtained with formulations in which PTFE is
present at about 25% by weight.
[0032] The flare formulations also include a polyaromatic
thermoplastic binder. In certain presently preferred embodiments,
the polyaromatic thermoplastic binder is comprised of polystyrene,
which is commercially available, for example, from Amoco.
Acrylonitrile butadiene styrenes (ABS) may be substituted for
polystyrene. The polystyrene or ABS may be plasticized using
phthalates, including dimethyl phthalate, diethyl phthalate,
dibutyl phthalate, dioctyl phthalate, poly terephthalate, and poly
ethyl terephthalate. Also usable are para or ortho substituted
chloropolystyrenes, nitropolystyrenes, polyacenaphthalene,
polyvinylcarbozol, polyvinylfluorene, other polyvinylaromatics,
.alpha. methylpolystyrenes, .alpha. chloropolystyrenes, .alpha.
alkylpolystyrenes, and copolymers of polystyrene, with, for
example, butadiene acrylonitrile, and acrylic acid. In certain
presently preferred embodiments, the polyaromatic thermoplastic is
dimethyl phthalate-plasticized polystyrene.
[0033] The amount and content of the plasticizer may be varied to
adjust the melting point of a flare composition. The melting point
of the composition may be chosen to increase the ease of production
or to meet the requirements of a specific tactical environment
(e.g., a composition may be designed for long-term storage in a
warm climate). Generally, the melting point of a composition
decreases as the amount of plasticizer increases. Compositions with
low melting points are easier to handle than compositions with
higher melting points. However, compositions with low melting
points do not maintain their mechanical properties as well as
higher melting point compositions during high temperature (up to
about 165.degree. F.) storage. It is presently preferred that the
plasticizer be present at up to about 80 weight percent of the
polyaromatic thermoplastic binder. More particularly, the
plasticizer is present at about 50 weight percent of the
binder.
[0034] It is presently preferred that the polyaromatic
thermoplastic binder be present at from about 8% to about 30% by
weight. More particularly, the binder is present in the range of
from about 10% to about 20% by weight. Generally, good results have
been obtained with formulations in which the binder is present at
about 14% to about 16% by weight.
[0035] The compositions of the present invention may also include
conductive carbon fibrils, which reduce the composition's
susceptibility to electrostatic discharge.
EXAMPLES
[0036] The following examples are given to illustrate various
embodiments which have been made or may be made in accordance with
the present invention. These examples are given by way of example
only, and it is to be understood that the following examples are
not comprehensive or exhaustive of the many types of embodiments of
the present invention which can be prepared in accordance with the
present invention.
Example 1
[0037]
2 Ingredient Weight Percent Magnesium (spherical) 66.0 Teflon .RTM.
20.0 Polystyrene 7.0 Dimethyl phthalate 7.0
[0038] This composition exceeds the radiometric performance of
fielded magnesium-PTFE decoy flares. FIG. 1 illustrates the
radiometric data generated by burning a pressed baseline
magnesium-PTFE decoy flare composition that is within the scope of
the prior art. FIG. 2 illustrates the radiometric data generated by
burning this composition. A comparison of these figures
demonstrates that the radiometric output of this composition
exceeds the radiometric output of the conventional composition.
Example 2
[0039]
3 Ingredient Weight Percent Magnesium 64.0 (spherical or a 50-50
mixture of spherical and chipped) Teflon .RTM. 20.0 Polystyrene 8.0
Dimethyl phthalate 8.0
[0040] This composition was extruded using a ram extruder, although
this composition could also be extruded using a single or twin
screw extruder.
[0041] Summary
[0042] In summary, the present invention provides new and useful
black body decoy compositions and methods of use. These
compositions may be extruded without the use of solvents. Such
compositions overcome some of the major drawbacks of decoy flare
compositions. Thus, the flare compositions of the present invention
represent a significant advancement in the art.
[0043] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *