RADIATION CURABLE ENERGETIC MATERIAL COMPOSITIONS AND METHODS OF USE
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.
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.
FIELDThis 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.
BACKGROUNDEnergetic 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.
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.
SUMMARYEnergetic 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.
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.
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.
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 EMBODIMENTSThe 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 μm, such as not greater than about 100 μm, such as not greater than about 75 μm, such as not greater than about 50 μm. In other applications, the mean (D50) particle size may be at least about 0.5 μm and not greater than about 30 μm, such as at least about 1 μm and not greater than about 20 μm. For many applications, the pyrotechnic will have a mean (D50) particle size of at least about 0.3 μm, such as at least about 1 μm. 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.
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.
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.
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.
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.
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.
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.
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.
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.
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 μm, such as not greater than about 500 μm, such as not greater than about 200 μm, such as not greater than about 100 μm, or even not greater than about 50 μm. In one characterization, the layer has a thickness of at least about 25 μm. 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 μm. Micro fluidic valves, mechanical syringes, and peristaltic pumps are suitable for layer thicknesses of greater than about 25 μm.
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.
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.
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.
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.
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.
EXAMPLESThe following examples provided an illustration of the compositions and methods of the present invention.
Example 1Some 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.
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.
The fluid formulation is placed in a 3-D printer having a nozzle orifice of about 340 μm 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.
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 2Table 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.
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.
The fluid formulation is placed in a 3-D printer having a nozzle orifice of about 1600 μm 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.
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 3Table 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.
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.
The fluid formulation is placed in a 3-D printer having a nozzle orifice of about 260 μm 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.
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 4Some 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.
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.
The fluid formulation is placed in a 3-D printer having a nozzle orifice of about 600 μm 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.
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.
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.
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)
Type: Application
Filed: Dec 5, 2017
Publication Date: Jul 12, 2018
Inventors: Theodore R. Spence (Grand Junction, CO), Christopher F. Williams (Grand Junction, CO)
Application Number: 15/832,744
