U.S. patent application number 15/832744 was filed with the patent office on 2018-07-12 for radiation curable energetic material compositions and methods of use.
The applicant listed for this patent is Capco, LLC. Invention is credited to Theodore R. Spence, Christopher F. Williams.
Application Number | 20180194699 15/832744 |
Document ID | / |
Family ID | 62782226 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180194699 |
Kind Code |
A1 |
Spence; Theodore R. ; et
al. |
July 12, 2018 |
RADIATION CURABLE ENERGETIC MATERIAL COMPOSITIONS AND METHODS OF
USE
Abstract
A radiation curable energetic composition that can be used, for
example, to form pyrotechnic energetic components. The energetic
composition includes a radiation curable polymer precursor and a
pyrotechnic. The energetic composition may be dispersed in a liquid
vehicle to facilitate deposition of the energetic composition using
direct-write techniques.
Inventors: |
Spence; Theodore R.; (Grand
Junction, CO) ; Williams; Christopher F.; (Grand
Junction, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Capco, LLC |
Grand Junction |
CO |
US |
|
|
Family ID: |
62782226 |
Appl. No.: |
15/832744 |
Filed: |
December 5, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62430198 |
Dec 5, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C06B 33/02 20130101;
C06B 27/00 20130101; C06B 45/10 20130101; C06B 21/0083 20130101;
C06B 33/04 20130101; C06B 45/00 20130101 |
International
Class: |
C06B 33/02 20060101
C06B033/02; C06B 33/04 20060101 C06B033/04; C06B 27/00 20060101
C06B027/00 |
Claims
1. A fluid formulation for the deposition of an energetic
composition, the fluid formulation comprising: a liquid vehicle;
and an energetic composition, the energetic composition comprising;
a radiation curable polymer precursor in an amount of at least
about 0.05 wt. % and not greater than about 10 wt. % of the
energetic composition, and a pyrotechnic in an amount of at least
about 75 wt. % and not greater than about 99 wt. % of the energetic
composition.
2. The fluid formulation recited in claim 1, wherein the
pyrotechnic is substantially insoluble in the liquid vehicle.
3. The fluid formulation recited in claim 1, wherein the liquid
vehicle comprises an alcohol.
4. The fluid formulation recited in claim 1, wherein the liquid
vehicle comprises a compound selected from isopropanol, ethanol,
butanol, methanol, and mixtures thereof.
5. The fluid composition recited in claim 1, wherein the radiation
curable polymer is an ultraviolet curable polymer precursor.
6. The fluid formulation recited in claim 1, wherein the energetic
composition comprises at least about 0.1 wt. % of the radiation
curable polymer precursor.
7. (canceled)
8. (canceled)
9. The fluid formulation recited in claim 1, wherein the energetic
composition comprises not greater than about 7.5 wt. % of the
radiation curable polymer precursor.
10. (canceled)
11. (canceled)
12. The fluid formulation recited in claim 1, wherein the radiation
curable polymer precursor comprises an acrylate monomer.
13. The fluid formulation recited in claim 1, wherein the radiation
curable polymer precursor comprises a monomer selected from the
group consisting of tetraethylene glycol diacrylate, tripropylene
glycol diacrylate, pentaerythritol triacrylate, and hexanediol
diacrylate.
14. (canceled)
15. The fluid formulation recited in claim 1, wherein the
pyrotechnic comprises pyrotechnic particulate constituents.
16-21. (canceled)
22. The fluid formulation recited in claim 1, wherein the
pyrotechnic comprises a fuel and an oxidizer.
23. The fluid formulation recited in claim 22, wherein the fuel
comprises boron.
24. The fluid formulation recited in claim 22, wherein the oxidizer
comprises potassium nitrate.
25. The fluid formulation recited in claim 22, wherein the
pyrotechnic comprises thermite.
26-28. (canceled)
29. The fluid formulation recited in claim 1, wherein the
pyrotechnic comprises an intermetallic pyrotechnic.
30. (canceled)
31. (canceled)
32. The fluid formulation recited in claim 1, wherein the fluid
formulation further comprises a binder.
33. (canceled)
34. (canceled)
35. The fluid composition recited in claim 1, wherein the fluid
composition comprises at least about 1 gram of the energetic
composition per gram of the liquid vehicle.
36. (canceled)
37. The fluid composition recited in claim 1, wherein the fluid
composition has a viscosity of not greater than about 70,000
centipoise.
38. A method for the deposition of an energetic material component,
comprising the steps of: first direct-write printing the fluid
composition recited in claim 1 onto a substrate to form a first
energetic material precursor layer; first exposing the first
energetic material precursor layer to a sufficient quantity of
radiation to polymerize the radiation curable polymer precursor and
form a first intermediate component precursor layer; first removing
the liquid vehicle from the first intermediate component precursor
layer to form at least a first portion of the energetic material
component.
39-42. (canceled)
43. An energetic material component comprising an energetic
composition, the energetic composition comprising: at least about
90 wt. % of a pyrotechnic; and at least about 0.1 wt. % and not
greater than about 5 wt. % of a cured UV polymer.
44-51. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S.
Provisional Application No. 62/430,198, filed on Dec. 5, 2016,
which is incorporated herein by reference in its entirety.
FIELD
[0002] This disclosure relates to the field of energetic materials,
particularly formulations of energetic materials that are
polymerizable by ultraviolet (UV) light. Such UV curable energetic
materials are particularly suitable for pyrotechnic applications,
such as for the additive manufacturing of pyrotechnic
components.
BACKGROUND
[0003] Energetic materials have widespread utilization, especially
in explosive compositions, composite propellants, and pyrotechnic
compositions. Typically, pyrotechnic and solid propellant
compositions are formed from a mixture of a finely divided
oxidizer, a metallic or energetic fuel, and a polymeric binder.
Modifying agents may be added to the compositions to tailor the
desired performance and aid manufacturability and insensitivity.
The performance of energetic material compositions is sensitive to
formulation stoichiometry, particle size, loading density, and
preparation procedures, among other factors.
[0004] Polymers have served extensively as binders and plasticizers
for energetic material compositions, contributing considerably to
technological advancements in the art. The polymers provide desired
physical properties and may act as a primary or secondary fuel
source for the energetic material. Polymers can be used in
propellant compositions and pyrotechnic compositions to achieve
performance metrics, thermal stability, insensitivity, and
shock/vibration resistance. Processing pitfalls of many traditional
polymers used in such compositions are the requirements of heat,
organic solvents, or curing agents (many of which have high
toxicity) to complete polymerization. These pitfalls are compounded
by processing times which can be, e.g., too short for cast-cure
production methods.
SUMMARY
[0005] Energetic material components produced in an additive
manufacturing process (e.g., 3-D printing) are susceptible to
gravitational slumping/deformation of the composition after
deposition, resulting in uncontrollable print geometries and
propagation of print error. According to the present disclosure,
the incorporation of radiation curable polymers, particularly UV
curable polymers, as binders and plasticizers for additive
manufactured energetic compositions may reduce or eliminate some of
these problems. By adding relatively small concentrations of a UV
curable polymer precursor to the primary energetic material and
curing the deposited composition, structural print integrity can be
attained with minimal impact on the performance of the primary
energetic material. UV curable polymers offer several advantages
over traditionally cured polymers in energetic material
applications. Cure times are nearly instant when exposed to UV
radiation and do not require heat. Typical UV curable polymer cure
times are on the order of milliseconds to seconds compared to
traditionally cured polymers which take hours to days. Production
speeds are increased due to reduced set-up times, reduced clean-up
labor, and increased yield since detection of curing problems can
happen immediately. Additionally, UV curable polymers are
formulated without solvents, meeting the green chemistry principle
to reduce hazardous substances, as curing is accomplished by
polymerization rather than evaporation.
[0006] In one embodiment, a fluid formulation for the deposition of
an energetic composition is disclosed. The fluid formulation
includes a liquid vehicle and an energetic composition. The
energetic composition includes a radiation curable polymer
precursor in an amount of at least about 0.05 wt. % and not greater
than about 10 wt. % of the energetic composition, and a pyrotechnic
in an amount of at least about 75 wt. % and not greater than about
99 wt. % of the energetic composition. The liquid vehicle may be,
for example, an alcohol. The radiation curable polymer may, for
example, a UV curable polymer. The UV curable polymer may even be
utilized in an amount of not greater than about 3 wt. % of the
energetic composition, or less. As a result, the polymer will have
little effect on the efficacy of the pyrotechnic.
[0007] In another embodiment, a method for the deposition of an
energetic material component is disclosed. The method includes the
steps of direct-write printing a fluid composition as disclosed
herein onto a substrate to form a first energetic material
precursor layer. The first energetic material precursor layer is
then exposed to a sufficient quantity of radiation (e.g., UV
radiation) to polymerize the radiation curable polymer precursor
and form a first intermediate component precursor layer.
Thereafter, the liquid vehicle is substantially removed from the
first intermediate component precursor layer (e.g., under a partial
vacuum) to form at least a first portion of the energetic material
component.
[0008] In another embodiment, an energetic material component is
disclosed. The component comprises an energetic composition
including a pyrotechnic and a polymer, where the concentration of
the pyrotechnic in the composition may be greater than about 90 wt.
% and where the concentration of the polymer may be not greater
than about 5 wt. %
DESCRIPTION OF THE EMBODIMENTS
[0009] The present disclosure is directed to the fluid formulations
for the deposition of an energetic composition, methods for the
deposition of an energetic material component, such as a
pyrotechnic, and to the deposited energetic material components.
The formulations, and methods include the use of relatively small
concentrations of a radiation curable polymer to minimize slumping
of a component that is deposited by a direct-write deposition
technique. As a result, energetic components may be formed having
an extremely high degree of accuracy and precision.
[0010] According to one embodiment of the present disclosure, a
fluid formulation for the deposition of an energetic composition is
disclosed. The fluid formulation includes a liquid vehicle and the
energetic composition. The energetic composition includes a
radiation curable polymer precursor and a pyrotechnic. The fluid
composition may advantageously have a viscosity that is
sufficiently low such that the fluid composition can be deposited,
e.g. onto a substrate, using a direct-write deposition technique,
including a 3-D printing technique. Such techniques are commonly
referred to as additive manufacturing techniques.
[0011] Although the fluid formulations and methods described herein
may be applicable to many types of energetic materials (e.g., high
explosives, propellants, etc.), the formulations and methods are
particularly useful for the formation of pyrotechnic components.
Thus, the remaining description will refer primarily to pyrotechnic
compositions, although his be understood that the present
disclosure may be applicable to other types of energetic
compositions.
[0012] The energetic composition in the fluid formulation includes
at least a first radiation curable polymer precursor. Different
types of polymers may be cured using different types of radiation,
however it is currently most expedient to utilize UV radiation as
this is the most efficient technology for the radiation curing of
such polymers. UV curable polymers undergo induced polymerization
when exposed to light in the UV region of the electromagnetic
spectrum, e.g., UVA, UVB, or UVC, where UVA, UVB, and UVC are
generally between the wavelengths of 400-315 nm, 315-280 nm, and
280-100 nm, respectively. The following description refers
primarily to UV curable polymer precursors, although other types of
polymer precursors that are curable using other types of radiation
are also contemplated.
[0013] By way of example, the UV curable polymer precursor may
comprise oligomers, monomers, and/or photoinitiators. The physical
and chemical properties of the UV curable polymer, e.g., curing
rate, chemical resistance, structural properties, viscosity, and
adhesion, are generally governed by the oligomers and monomers.
Oligomers and monomers can be monofunctional or multifunctional.
Examples include, but are not limited to, epoxies, polyesters,
acrylics, acrylated silicones, aliphatic urethanes, aromatic
urethanes, and precursors to acrylate polymers, such as acrylic
acrylate-based polymers, aliphatic urethane acrylate-based
polymers, aromatic urethane acrylate-based polymers,
fluoroacrylates, polyester acrylate-based polymers, epoxy
acrylate-based polymers and the like. Specific examples include,
but are not limited to, tetraethylene glycol diacrylate, ethylene
glycol diacrylate, phosphoric acid diacrylate, tripropylene glycol
diacrylate, pentaerythritol triacrylate, hexanediol diacrylate,
isobutyl methacrylate, tetrahydrofurfuryl methacrylate, and octyl
methacrylate, aliphatic urethane diacrylate, bisphenol A diglycidyl
ether diacrylate, pentaerythritol methacrylate, pentaerythritol
triacrylate, isocyanurate triacrylate, isobornyl acrylate, and
trimethylol propane triacrylate.
[0014] The radiation curable polymer precursor may also include one
or more unimolecular and/or bimolecular photoinitiators. The
photoinitiator determines the UV wavelength and minimum UV
radiation energy necessary to initiate the photochemical reaction
that cures the polymer. Examples of useful cationic and free
radical photoinitiators include, but are not limited to
benzophenone, benzyl dimethyl ketal, 4-benzoyl-4-methyl diphenyl
sulphide, methylbenzoylformate, diphenyl
(2,3,6-trimethylbenzoyl)-phosphine oxide,
2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone,
alpha-dimethoxy-alpha-phenylacetophenone,
1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-methyl-propiophenone,
2-isopropyl thioxanthone, 2-ethyl anthraquinone, 2-4-diethyl
thioxanthone, 4-pheyl benzophenone, 4-chloro benzophenone,
methyl-2-benzoylbenzoate, isoamyl 4-(dimethylamino) benzoate,
ethyl-4-(dimethylamino) benzoate, and n-phenyl glycine.
[0015] In addition to monomers, oligomers and/or photoinitiators,
small concentrations of plasticizers and cure catalysts can be
added to the UV curable polymer precursor to modify the physical
properties of the polymer.
[0016] The energetic composition also comprises a pyrotechnic.
Pyrotechnics are materials capable of undergoing self-sustained
exothermic chemical reactions for the production of heat, light,
gas, smoke and/or sound. Pyrotechnics include materials that
utilize fuels and oxidizers to yield the exothermic reaction(s).
Pyrotechnic fuel/oxidizer formulations may comprise inorganic
and/or organic fuels and oxidizers. Pyrotechnic thermites comprise
only inorganic fuels and oxidizers. Pyrotechnic intermetallics
comprise only inorganic fuels without any oxidizers.
[0017] Thus, in one embodiment, the pyrotechnic includes a fuel and
oxidizer. Examples of a fuel include, but are not limited to,
inorganics (e.g., boron, aluminum, beryllium, titanium, zirconium,
magnesium, iron, zinc, sulfur, silicon, cobalt, calcium, manganese,
nickel, and copper) and organics (e.g., carbon, hexamine, sucrose,
sorbitol, polyurethane, polyisobutylene, terephthalic acid,
polyethylene, and polysulfide). Among these, aluminum and boron may
be particularly useful for some applications. Examples of oxidizers
include, but are not limited to, metal oxides. Examples of metal
oxide oxidizers include, but are not limited to, copper oxide
(e.g., cupric oxide or cuprous oxide), manganese dioxide, iron
oxide (e.g., ferric oxide or ferrous oxide) and the like. Examples
of other oxidizers include, but are not limited to, chlorates
(e.g., ammonium perchlorate, potassium chlorate, potassium
perchlorate), nitrates (e.g., ammonium nitrate, potassium nitrate,
strontium nitrate), hexanitroethane and ammonium dinitramide.
Examples of organic oxidizers include, but are not limited to,
polytetrafluorethylene (PTFE), graphite fluoride, graphite oxide,
picric acid, picryl chloride, ethylenedinitramine,
cyclotrimethylenetrinitramine (RDX), cyclotetramethylene
tetranitramine (HMX), hexanitrohexaazaisowurtzitane (CL-20),
triacetone triperoxide (TATP), methyl ethyl ketone peroxide,
oxtanitrocubane.
[0018] In another embodiment, the pyrotechnic includes an
intermetallic. Examples of useful pyrotechnic intermetallics
include, but are not limited to, titanium/boron, aluminum/boron,
aluminum/titanium, aluminum/zirconium, aluminum/cobalt,
boron/cerium, boron/vanadium, beryllium/carbon, carbon/hafnium,
carbon/silicon, calcium/tin, and magnesium/sulfur. A titanium/born
intermetallic may be particularly useful for some applications.
[0019] The pyrotechnic may be present in the form of a solid.
Advantageously, to facilitate the direct-write deposition of the
fluid composition, the pyrotechnic is in the form of particulates.
For example, the particulates may have a mean (D50) particle size
of not greater than about 200 .mu.m, such as not greater than about
100 .mu.m, such as not greater than about 75 .mu.m, such as not
greater than about 50 .mu.m. In other applications, the mean (D50)
particle size may be at least about 0.5 .mu.m and not greater than
about 30 .mu.m, such as at least about 1 .mu.m and not greater than
about 20 .mu.m. For many applications, the pyrotechnic will have a
mean (D50) particle size of at least about 0.3 .mu.m, such as at
least about 1 .mu.m. In some applications, nano-sized particulates
may be useful, such as where the particulates have a mean (D50)
particle size of at least about 10 nm, such as at least about 20
nm, and not greater than about 200 nm, such as not greater than
about 100 nm.
[0020] The energetic composition should include a sufficient
concentration of radiation curable polymer precursor such that,
upon exposure to the radiation, the deposited feature resists
slumping, e.g., resists deformation due to the force of gravity.
Thus, in one embodiment, the energetic composition includes at
least about 0.05 wt. % of the radiation curable polymer precursor,
such as at least about 0.1 wt. % of the radiation curable polymer
precursor, such as at least about 0.5 wt. %, or at least about 1.0
wt. % of the radiation curable polymer precursor. However, it is an
advantage of the energetic compositions disclosed herein that the
concentration of the radiation curable polymer precursor is
relatively low as compared to the concentration of the pyrotechnic.
Thus, the energetic composition advantageously may comprise not
greater than about 10 wt. % of the radiation curable polymer
precursor, such as not greater than about 7.5 wt. % of the
radiation curable polymer precursor, such as not greater than about
5 wt. % of the radiation curable polymer precursor, or even not
greater than about 3 wt. % of the radiation curable polymer
precursor, or even not greater than about 2 wt. % of the radiation
curable polymer. One advantage of utilizing low concentrations of
the polymer precursor, e.g., low concentrations of the polymer in
the deposited energetic composition, is that the dilution effect of
the polymer on the pyrotechnic is reduced, that is, the energetic
composition may include a very high concentration of the
pyrotechnic.
[0021] Thus, the energetic composition may include at least about
75 wt. % of the pyrotechnic, such as at least about 80 wt. %
pyrotechnic, such as at least about 85 wt. % pyrotechnic, such as
at least about 90 wt. % pyrotechnic, such as at least about 95 wt.
% pyrotechnic, or even at least about 98 wt. % of the pyrotechnic.
Stated another way, the weight ratio of the pyrotechnic to the
polymer in the deposited feature may be at least about 15:1, such
as at least about 25:1, such as at least about 30:1, or even at
least about 40:1. As a practical matter, the energetic composition
will typically include not greater than about 99.5 wt. % of the
pyrotechnic, such as not greater than about 99 wt. % of the
pyrotechnic.
[0022] The energetic composition may also include other additives,
such as binders, plasticizers, burn rate modifiers, dyes and
colorants, and the like. Such additional additives may be included
in the energetic composition in concentrations of not greater than
about 10 wt. %, such as not greater than about 5 wt. %. Examples of
useful binders include elastomeric binders, such as a fluorocarbon
binder. Depending on the end use of the energetic composition, the
selection and stoichiometry of fuels, oxidizers and modifying
agents, if any, may be altered to achieve the desired performance
and physical properties.
[0023] The liquid carrier utilized in the fluid composition may be
selected such that the pyrotechnic is substantially insoluble in
the liquid carrier, e.g., does not substantially dissolve or
otherwise degrade in the liquid carrier. Further, the liquid
carrier may be a liquid that may be rapidly removed from the
deposited component, e.g., by natural or induced evaporation. In
one characterization, the liquid carrier may be an alcohol.
Examples of particularly useful liquid carriers include, but are
not limited to, isopropanol, ethanol, butanol, methanol, and
mixtures thereof.
[0024] The components of the fluid composition may be combined and
mixed to ensure homogeneity of the components in the composition,
including the particulate pyrotechnic. For example, the components
may be combined in a high shear mixer, dual asymmetric centrifugal
mixer, acoustic mixer, sonicator, paddle mixer, sigma blade mixer,
tumble blender, v-mixer or the like. When the radiation curable
polymer precursor is homogenously mixed in the composition, the
deposited composition (e.g., a slurry) will retain its structural
integrity when irradiated to cure the polymer, while remaining wet
due to the presence of the liquid carrier.
[0025] The fluid compositions may include a sufficient amount of
the energetic composition (e.g., the particulate pyrotechnic and
the polymer precursor) to form a deposited layer that may be
rapidly cured by UV radiation before slumping or otherwise
deforming significantly. This requirement must be balanced with the
desire to have a sufficiently low viscosity to permit direct-write
deposition of the formulation by the selected direct-write tool. In
one characterization, the fluid composition includes at least about
1 gram of the energetic composition per gram of the liquid vehicle.
In another characterization, the fluid composition includes not
greater than about 6 grams of the energetic composition per gram of
the liquid vehicle. In another characterization, the fluid
composition has a viscosity that is not greater than about 70,000
centipoise, such as not greater than about 50,000 centipoise, such
as not greater than about 20,000 centipoise. For many direct-write
tools, the fluid composition will have a viscosity of not greater
than about 10,000 centipoise, such as not greater than about 8,000
centipoise, or even not greater than about 5,000 centipoise.
[0026] The UV curable energetic material can advantageously be used
for the additive manufacturing of pyrotechnic components. A common
issue experienced with the additive manufacturing of such
components is gravitational slumping/deformation of the print after
deposition, resulting in uncontrollable print geometries and
propagation of print error. However, by adding small concentrations
of the UV curable polymer to the composition and rapidly curing the
deposited print, structural print integrity can be attained with
minimal impact on the efficacy of the energetic material.
[0027] Thus, one embodiment of the present disclosure is directed
to a method for the deposition of energetic material component. The
method includes direct-write deposition of a fluid composition that
includes a radiation curable polymer and a pyrotechnic, as is
disclosed in detail above. The fluid composition may be deposited
onto a substrate to form a first energetic material precursor
layer, e.g., a layer including the liquid vehicle, the radiation
curable polymer precursor and the pyrotechnic. Soon after
deposition of the fluid composition, the energetic material
precursor layer is exposed to a sufficient quantity of radiation,
e.g., UV or electron beam radiation, for a sufficient time to
polymerize the radiation curable polymer precursor and form a first
intermediate component precursor layer. As a result, slumping of
the deposited feature is mitigated or minimized until such time as
the remaining liquid carrier can be removed from the intermediate
layer. Thus, the first intermediate component precursor layer
includes the cured polymer, the pyrotechnic and the remaining
liquid carrier. After the intermediate component precursor layer is
formed, the liquid vehicle is removed from the intermediate layer
to form at least a portion of the energetic material component, at
least one layer of the energetic material component. Depending on
the characteristics of the liquid vehicle (e.g., the vapor
pressure), the liquid vehicle can be removed by evaporation, either
naturally or assisted by a partial vacuum and/or by applying heat
to the intermediate layer.
[0028] The thus-formed energetic material component may have a
small size and a precise configuration as a result of the
direct-write deposition process. For example, the layer may have a
thickness (e.g., a height) of not greater than about 1000 .mu.m,
such as not greater than about 500 .mu.m, such as not greater than
about 200 .mu.m, such as not greater than about 100 .mu.m, or even
not greater than about 50 .mu.m. In one characterization, the layer
has a thickness of at least about 25 .mu.m. The direct-writing of
the fluid composition can be carried out using a range of know
direct-write tools, including, but not limited to, ink-jet
printers, aerosol jet printers, micro fluidic valves, mechanical
syringes, peristaltic pumps and the like. Ink-jet and aerosol jet
printers are suitable for layer thicknesses of less than about 25
.mu.m. Micro fluidic valves, mechanical syringes, and peristaltic
pumps are suitable for layer thicknesses of greater than about 25
.mu.m.
[0029] The process described above can be repeated to form
additional layers, e.g., second, third, fourth, etc. layers that
wholly or partially overlap the first portion of the energetic
material component, e.g., that wholly or partially overlap the
first layer. For example, the layers can be deposited and cured
before deposition of the next layer. In this manner, and through
the application of precise numerical control of the direct-write
tool, pyrotechnic components having complex geometries may be
fabricated.
[0030] The use of direct-write deposition tools to deposit the
fluid formulations disclosed herein may also be used to form a
functionally-graded pyrotechnic component, e.g., a pyrotechnic
component including two or more different layers, e.g., layers of
different energetic compositions having different pyrotechnics
and/or different densities of pyrotechnic. Direct-write deposition
tools can also be utilized for the additive manufacture of
components having various, high-precision structural features, such
as voids.
[0031] In another embodiment of the present disclosure, an
energetic material component comprising an energetic composition is
disclosed. The energetic composition includes a pyrotechnic and a
cured UV polymer, e.g., a pyrotechnic and a polymer formed from the
UV curable polymer precursors described in detail above. In one
characterization, the component is fabricated from a fluid
composition as is disclosed above, and/or by using a direct-write
deposition technique as is disclosed above.
[0032] Thus, in one characterization, energetic material component
includes an energetic composition that comprises at least about 95
wt. % of the pyrotechnic, such as at least about 98 wt. % of the
pyrotechnic. In another characterization, the energetic composition
comprises not greater than about 5 wt. % of the cured polymer, such
as not greater than about 3 wt. % of the cured polymer. In another
characterization, the weight ratio of the pyrotechnic to the cured
polymer in the energetic composition is at least about 25:1, such
as at least about 30:1, or even at least about 40:1.
[0033] Common pyrotechnic applications include countermeasure
flares, electro-explosive devices, explosive bolts/nuts, fuzes,
illuminating flares, impulse cartridges, percussion primers,
pyrotechnic actuators, pyrotechnic cutters, pyrotechnic gas
generators, pyrotechnic ignitors, pyrotechnic inflators,
pyrotechnic initiators, pyrotechnic pin pullers/pushers,
pyrotechnic signals, pyrotechnic smokes/obscurants, pyrotechnic
valves, safe & arm devices, and sequencing time delays. The
compositions and methods disclosed herein can be utilized to
manufacture these and other devices.
EXAMPLES
[0034] The following examples provided an illustration of the
compositions and methods of the present invention.
Example 1
[0035] Some pyrotechnics include a fuel and an oxidizer. An example
of an energetic composition according to the present disclosure
including such a pyrotechnic is illustrated in Table I.
TABLE-US-00001 TABLE I Mean Type Component Wt. % Particle Size Fuel
Boron 79 750 nm Oxidizer Potassium Nitrate 19 3 um UV Curable
Polymer tetraethylene glycol 2 N/A Precursor diacrylate
[0036] 500 grams of the energetic composition listed in Table I is
mixed with 250 mL of isopropanol in a high shear mixer to form the
fluid formulation, e.g., a slurry of boron and potassium nitrate
particles dispersed with the UV curable polymer precursor in the
isopropanol. When the mixing is complete, the fluid formulation has
a viscosity of about 1100 centipoise.
[0037] The fluid formulation is placed in a 3-D printer having a
nozzle orifice of about 340 .mu.m in diameter. The fluid
formulation is then deposited onto an aluminum substrate as the
nozzle moves over the substrate in a controlled manner, e.g., using
digital control, to form an energetic material precursor layer.
After deposition of the fluid formulation, the formulation is
immediately exposed to ultraviolet radiation to rapidly cure the
polymer precursor and form an intermediate component precursor
layer. By virtue of the UV curing of the polymer, the intermediate
precursor layer resists slumping or otherwise deforming due to the
simple effect of gravity.
[0038] After UV curing, the isopropanol is removed from the
intermediate precursor layer by applying a partial vacuum to the
layer. Upon removal of the isopropanol, an energetic material
component is formed.
Example 2
[0039] Table II illustrates another example of an energetic
composition that includes a pyrotechnic comprising a fuel and an
oxidizer. The pyrotechnic composition illustrated in Table II is a
type of pyrotechnic referred to as a thermite.
TABLE-US-00002 TABLE II Type Component Wt. % Mean Particle Size
Fuel Aluminum 45 5 .mu.m Oxidizer Copper (II) Oxide 52 15 .mu.m UV
Curable Polymer ethylene glycol 2.95 N/A Precursor diacrylate
Plasticizer Ethylene 0.05 N/A carbonate
[0040] 100 grams of the energetic composition (fuel, oxidizer and
polymer precursor) listed in Table II is mixed with 30 mL of
ethanol in a dual asymmetric centrifugal mixer. During mixing, the
plasticizer is added to the mixer. When the mixing is complete, the
fluid formulation has a viscosity of about 4600 centipoise.
[0041] The fluid formulation is placed in a 3-D printer having a
nozzle orifice of about 1600 .mu.m in diameter. The fluid
formulation is then deposited onto a glass substrate as the nozzle
moves over the substrate in a controlled manner, e.g., using
digital control, to form an energetic material precursor layer.
After deposition of the fluid formulation, the formulation is
immediately exposed to ultraviolet radiation to rapidly cure the
polymer precursor and form an intermediate component precursor
layer. By virtue of the UV curing of the polymer, the intermediate
precursor layer resists slumping or otherwise deforming due to the
simple effect of gravity.
[0042] After UV curing, the ethanol is removed from the
intermediate precursor layer by applying a partial vacuum to the
layer. Upon removal of the ethanol, an energetic material component
is formed.
Example 3
[0043] Table Ill illustrates another example of an energetic
composition that includes a type of thermite pyrotechnic. In this
example, the thermite components have a particle size in the
nanometer range, e.g., a nano-thermite.
TABLE-US-00003 TABLE III Mean Type Component Wt. % Particle Size
Fuel Aluminum 28 50 nm Oxidizer Manganese Dioxide 61 80 nm UV
Curable Polymer pentaerythritol triacrylate 5 N/A Precursor Binder
Fluoroelastomer 6 N/A
[0044] 5 kilograms of the thermite pyrotechnic composition (fuel,
oxidizer, and binder) listed in Table Ill is mixed with 12.5
kilograms of acetone in a high shear mixer. The fluoroelastomer
binder, which is soluble in acetone, is coated onto the fuel and
oxidizer particles via the addition of 20.9 kilograms of hexane,
resulting in precipitation of the coated particles. The supernatant
acetone/hexane solution is decanted and the resulting slurry is
dried. After drying, the polymer precursor and 3 kg of butanol are
added to the coated particles and the formulation is mixed again in
a high shear mixer. When the mixing is complete, the fluid
formulation has a viscosity of about 800 centipoise.
[0045] The fluid formulation is placed in a 3-D printer having a
nozzle orifice of about 260 .mu.m in diameter. The fluid
formulation is then deposited onto a polyvinyl acetate-coated glass
substrate as the nozzle moves over the substrate in a controlled
manner, e.g., using digital control, to form an energetic material
precursor layer. After deposition of the fluid formulation, the
formulation is immediately exposed to ultraviolet radiation to
rapidly cure the polymer precursor and form an intermediate
component precursor layer. By virtue of the UV curing of the
polymer, the intermediate precursor layer resists slumping or
otherwise deforming due to the simple effect of gravity.
[0046] After UV curing, the butanol is removed from the
intermediate precursor layer by applying a partial vacuum to the
layer. Upon removal of the butanol, an energetic material component
is formed.
Example 4
[0047] Some pyrotechnics include two or more metallic materials
that combine to form an intermetallic material in a highly
exothermic reaction. An example of an energetic composition
according to the present disclosure including such a pyrotechnic is
illustrated in Table IV.
TABLE-US-00004 TABLE IV Type Component Wt. % Mean Particle Size
Fuel Titanium 72 3 .mu.m Fuel Boron 26 1 .mu.m UV Curable isobornyl
acrylate 2 N/A Polymer Precursor
[0048] 25 grams of the intermetallic pyrotechnic composition (fuels
and polymer precursor) listed in Table IV is mixed with 16 mL of
methanol in a resonant frequency mixer. When the mixing is
complete, the fluid formulation has a viscosity of about 3200
centipoise.
[0049] The fluid formulation is placed in a 3-D printer having a
nozzle orifice of about 600 .mu.m in diameter. The fluid
formulation is then deposited onto a temperature controlled glass
substrate as the nozzle moves over the substrate in a controlled
manner, e.g., using digital control, to form an energetic material
precursor layer. After deposition of the fluid formulation, the
formulation is immediately exposed to ultraviolet radiation to
rapidly cure the polymer precursor and form an intermediate
component precursor layer. By virtue of the UV curing of the
polymer, the intermediate precursor layer resists slumping or
otherwise deforming due to the simple effect of gravity.
[0050] After UV curing, the ethanol is removed from the
intermediate precursor layer by applying heat to the print bed.
Upon removal of the methanol, an energetic material component is
formed.
[0051] While various embodiments of fluid compositions of energetic
materials, methods for making the composition, methods for
depositing the compositions and components formed thereby have been
described in detail, it is apparent that modifications and
adaptations of those embodiments will occur to those skilled in the
art. However, it is to be expressly understood that such
modifications and adaptations are within the spirit and scope of
the present disclosure.
* * * * *