Patent Application
20140137996
The present disclosure relates to propellant compositions including a stabilized, encapsulated red phosphorus. More specifically, the present disclosure relates to propellant compositions that include the stabilized, encapsulated red phosphorus and at least one energetic binder, a method of forming such propellant compositions and an ordnance element including such propellant compositions.
Propellants including two base components, such as a nitrocellulose (NC) and an energetic plasticizer, are commonly referred to as so-called “double base” propellants and are widely used in munitions, such as rifle and pistol cartridges, rocket motors, mortar shells, shotgun shells and missiles. Examples of energetic plasticizers that may be combined with the nitrocellulose to form the double base propellant include, but are not limited to, nitroglycerine, butanetriol trinitrate and diglycol dinitrate. The nitrocellulose desensitizes the highly unstable energetic plasticizer, preventing the double base propellant from detonating as a high explosive. The energetic plasticizer gelatinizes the nitrocellulose, increasing the energy density of the double base propellant. For example, conventional double base propellants may include, as main ingredients, between about 10% by weight (wt %) and about 90 wt % nitrocellulose and between about 10 wt % and about 90 wt % nitroglycerine. Such double base propellants may be loaded within a cartridge or shell casing used in an ordnance element, along with a primer composition used to initiate or ignite the double base propellant. The double base propellants may also be used in rocket motors and missiles, where they are disposed inside a case to provide thrust upon burning.
For ballistic applications, it is desirable for propellants to burn at a controlled and predictable rate without performance loss. Controlling the ballistic properties of the propellant, such as burn rate, enables proper function of the ordnance element or rocket motor. When the burn rate of the propellant is too high, pressures within the cartridge, shell casing or rocket motor case may exceed design capability, resulting in damage to or destruction of the cartridge, shell casing or rocket motor case. On the other hand, if the burn rate of the propellant is too low, the propellant may not provide sufficient velocity to propel a projectile of the ordnance element or the rocket motor over a desired course.
To tailor the ballistic properties of the propellant, such as the burn rate and the velocity, materials that control ballistic properties, so-called “ballistic modifiers,” may be included in the propellant. Various organometallic salts and various oxides have been used to modify the ballistic properties of propellants, such as double base propellants. Examples of such ballistic modifiers include lead-based compounds, such as, lead salts and lead oxides (e.g., lead salicylate, lead β-resorcylate and lead stearate). The use of lead-based compounds as ballistic modifiers poses a concern for the environment and for personal safety due to the toxic nature of lead when introduced into the atmosphere by propellant manufacture, rocket motor firing and disposal. The presence of these lead-based ballistic modifiers is, therefore, detrimental to the environment when the propellant is burning.
Conventional propellants may also contain ammonium perchlorate (AP), which upon combustion produces the toxic substance hydrochloric acid (HCl). Chloride ions released from hydrochloric acid in the upper atmosphere may react with and destroy ozone.
Other, nontoxic compounds have been investigated as potential replacements for lead-based ballistic modifiers in propellants. For example, copper- and barium-based compounds have been shown to modify the ballistic properties of propellants. However, performance characteristics of the propellants are impaired by the use of these copper- and barium-based compounds. Solid propellants containing copper salts as the ballistic modifier may exhibit a poor aging. Barium salts, being highly soluble in water, are problematic in conventional manufacturing processes used to form the propellants.
Red phosphorus has been investigated as a component in primer compositions for military applications. Red phosphorus is an allotrope of phosphorus that has a network of tetrahedrally arranged groups of four phosphorus atoms linked into chains. White phosphorous is another allotrope that is much more reactive and toxic than red phosphorus. The two allotropes have such unique physical characteristics that they have different CAS numbers, as registered by the Chemical Abstract Service (“CAS”). Red phosphorus is relatively stable in air and is easier to handle than other allotropes of phosphorus. However, if red phosphorus is exposed to oxygen (O2), water (H2O), or mixtures thereof at elevated temperatures, such as during storage, the red phosphorus reacts with the oxygen and water, releasing phosphine (PH3) gas and phosphoric acids (H3PO2, H3PO3, or H3PO4). As is well known, the phosphine is toxic and the phosphoric acids are corrosive. To improve the stability of red phosphorus in environments rich in oxygen or water, dust suppressing agents, stabilizers, or microencapsulating resins have been used. The dust suppressing agents are liquid organic compounds. The stabilizers are typically inorganic salts, such as metal oxides. The microencapsulating resins are thermoset resins, such as epoxy resins or phenolic resins. Currently, microencapsulating resins are not used in military applications. The military specification for phosphorous has been deactivated and is not expected to be updated to include encapsulation.
U.S. Pat. No. 7,857,921 to Busky et al. discloses a primer composition that includes a stabilized, encapsulated red phosphorus and combinations of at least one oxidizer, at least one secondary explosive composition, at least one light metal, or at least one acid resistant binder. The stabilized, encapsulated red phosphorus may include particles of red phosphorus, a metal oxide coating, and a polymer layer.
In some embodiments, the present disclosure includes propellant compositions. For example, such a propellant composition may include nitrocellulose and a stabilized, encapsulated red phosphorous.
In another embodiment, the propellant compositions of the present disclosure may include a propellant comprising an energetic binder and an energetic plasticizer and a stabilized, encapsulated red phosphorus.
In yet another embodiment, the present disclosure includes an ordnance element. The ordnance element may include a propellant composition comprising a stabilized, encapsulated red phosphorus and an energetic binder comprising nitrocellulose and at least one of another explosive and a primer.
In a further embodiment, the present disclosure includes a method of forming a propellant composition. Such a method may include combining a stabilized, encapsulated red phosphorus with a propellant comprising nitrocellulose and an energetic plasticizer.
Propellant compositions that include at least one energetic binder combined with encapsulated, stabilized red phosphorus are disclosed. The propellant compositions may be used in an ordnance element or a weapon system, such as, a cartridge, a shotgun shell, an artillery shell, a rocket motor, or a missile, for example. Upon combustion, the propellant compositions of the present disclosure may exhibit a reduced peak pressure in comparison to conventional propellants while an average pressure of the propellant compositions of the present disclosure is maintained or improved. Thus, the propellant compositions may provide a desirable reduction in mechanical stress on the ordnance element or weapon system while maintaining velocity. Addition of the stabilized, encapsulated red phosphorus may modify the ballistic properties of the propellant compositions, reducing or eliminating the need for conventional (e.g., lead-based) ballistic modifiers. The propellant compositions may, thus, be substantially lead-free, reducing or eliminating environmental issues associated with lead-based compositions. The propellant compositions may include ingredients that are low in toxicity (e.g., green), free of heavy metals, stable to aging and noncorrosive. These ingredients may include elements that are biologically available, have a high concentration tolerance, and are active in known cycles in the environment or biosphere. When combusted, the propellant compositions may generate nontoxic and noncorrosive combustion products and byproducts. By using encapsulated, stabilized red phosphorus in the propellant compositions, a decreased amount of the propellant composition of the present disclosure may be used in the ordnance element relative to the amount of conventional propellant used in the ordnance element to achieve a desired velocity of the ordnance element. Or, an increase in velocity performance of the ordnance element may be achieved using the same amount of the propellant composition of the present disclosure relative to the amount of conventional propellant.
As used herein, the term “burn rate” means and includes a rate at which a propellant composition releases energy during combustion.
As used herein, the term “peak pressure” means and includes the force exerted by a burning propellant within a chamber, such as within a rocket motor case.
As used herein, the term “single base propellant” means and includes a composition that includes an energetic binder, such as nitrocellulose (NC), and at least one additive, such as, a plasticizer, a ballistic modifier, a stabilizer, a flash suppressor, etc.
As used herein, the term “double base propellant” means and includes a composition that includes at least one energetic binder, such as nitrocellulose, and at least one energetic plasticizer, such as a nitrate ester. For example, the double base propellant may include nitrocellulose plasticized with the nitrate ester nitroglycerine (NG).
As used herein, the term “multi base propellant” means and includes a propellant that includes at least one energetic binder, such as nitrocellulose, at least one energetic plasticizer, and an energetic fuel other than nitrocellulose, such as, nitroguanidine.
A propellant composition of the present disclosure may include an energetic binder and a stabilized, encapsulated form of red phosphorus. As used herein, the term “stabilized, encapsulated” refers to red phosphorus having improved stability to oxidation relative to red phosphorus that lacks stabilization and encapsulation. For instance, when the stabilized, encapsulated red phosphorus is exposed to an environment that includes oxygen (O2), water (H2O), or mixtures thereof, the stabilized, encapsulated red phosphorus does not readily react with the oxygen or water, in contrast to red phosphorus that lacks stabilization. The stabilized, encapsulated red phosphorus may have an increased useful lifetime in the propellant composition compared to red phosphorus that lacks stabilization. The stabilized, encapsulated red phosphorus may account for up to about 10 wt % of a total weight of the propellant composition, more particularly, between about 0.1 wt % of the total weight of the propellant composition and about 5 wt % of the total weight of the propellant composition.
The red phosphorus may be stabilized by coating the red phosphorus with a metal oxide, such as a metal hydroxide, such as by coating particles of the red phosphorus. The metal oxide may be precipitated on a surface of the red phosphorus. The metal oxide coating functions as a stabilizer to buffer traces of acids that form upon oxidation of the red phosphorus. The metal oxide may be aluminum hydroxide, bismuth hydroxide, cadmium hydroxide, cerium hydroxide, chromium hydroxide, germanium hydroxide, magnesium hydroxide, manganese hydroxide, niobium hydroxide, silicon hydroxide, tin hydroxide, titanium hydroxide, zinc hydroxide, zirconium hydroxide, or mixtures thereof. The metal oxide may be present in the stabilized, encapsulated red phosphorus in a total quantity of between about 0.1 wt % and about 5 wt % and, more particularly, about 2 wt %, based on the quantity of red phosphorus.
Once stabilized, the red phosphorus may be encapsulated by coating the red phosphorus with a polymer, such as a thermoset resin. Encapsulating particles of the stabilized, red phosphorus reduces their active surface and provides the stabilized, red phosphorus with water repellency and acid resistance. Examples of polymers that may be used to encapsulate the stabilized, red phosphorus include, but are not limited to, an epoxy resin, melamine resin, phenol formaldehyde resin, polyurethane resin, or mixtures thereof. The polymer may be present in the stabilized, encapsulated red phosphorus in a total quantity of between about 1 wt % and about 5 wt % based on the quantity of red phosphorus. The metal oxide and the polymer may be present in a total quantity of between about 1.1% wt % and about 8 wt % based on the quantity of red phosphorus.
The red phosphorus may be coated with the metal oxide by mixing an aqueous suspension of the particles of the red phosphorus with a water-soluble metal salt. The pH of the aqueous suspension may be adjusted, precipitating the metal oxide on the red phosphorus. An aqueous solution of a preliminary condensation product of the polymer may be prepared and added, with mixing, to the coated red phosphorus. The solution and the coated red phosphorus may be reacted for a period of time that ranges from approximately 0.5 hours to approximately 3 hours at a temperature ranging from approximately 40° C. to approximately 100° C., enabling the preliminary condensation product to polymerize and harden around the coated red phosphorus. The particles of the stabilized, encapsulated red phosphorus may then be filtered and dried at an elevated temperature, such as at a temperature ranging from approximately 80° C. to approximately 120° C., in a stream of nitrogen. Stabilized, encapsulated red phosphorus is commercially available, such as from Clariant GmbH (Frankfurt, Germany). In one embodiment, the stabilized, encapsulated red phosphorus is Red Phosphorus HB 801 (TP), which is available from Clariant GmbH.
The at least one energetic binder used to form the propellant composition may include, for example, nitrocellulose (e.g., plastisol nitrocellulose), cyclodextrin nitrate (CDN), polyvinyl nitrate (PVN), dinitropropylacrylate polymers, polymeric nitroethylenes, and mixtures and combinations thereof. Relative amounts of the stabilized, encapsulated form of red phosphorus and the energetic binder may be adjusted to achieve desired properties of the propellant composition upon combustion.
The propellant composition may further include at least one energetic plasticizer, such as at least one nitrate ester. Examples of such energetic plasticizers include, but are not limited to, nitroglycerine, trinitroglycerine (TNG), metriol trinitrate (MTN), trimethylolethane trinitrate (TMETN), diglycol dinitrate, triethylene glycol dinitrate (TEGDN), butanetriol trinitrate (BTTN), diethyleneglycol dinitrate (DEGDN), propylene glycol dinitrate (PGDN), ethylene glycol dinitrate (EGDN), butyl-2-nitratoethyl-nitramine, methyl-2-nitratoethyl-nitramine and ethyl-2-nitratoethyl-nitramine. The energetic binder may be plasticized with the energetic plasticizer, increasing the energy density of the propellant composition.
By way of example and not limitation, the energetic binder may be present in an amount of between about 10 wt % of the total weight of the propellant composition and about 90 wt % of the total weight of the propellant composition and the energetic plasticizer may be present in an amount of between about 10 wt % of the total weight of the propellant composition and about 90 wt % of the total weight of the propellant composition. The propellant composition may optionally include at least one additive, such as, processing agents and chemical modifiers.
For example, the propellant composition may optionally include at least one inert liquid. Examples of such inert liquids include, but are not limited to, alkyl acetates, phthalates (e.g., dibutyl phthalate, diisoamyl phthalate, diethyl phthalate, dioctylphthalate, dipropylphthalate and dimethyl phthalate), adipates (e.g., polyester adipate, di-2-ethyl hexyl adipate, di-n-propyl adipate and diisooctyl adipate), triacetin, citric acid esters, phosphoric acid esters and urethane. For example, the at least one inert liquid may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 20 wt % of the total weight of the propellant composition. As a non-limiting example, the propellant composition may include between about 0 wt % and about 10 wt % of each of dibutyl phthalate and polyester adipate as inert liquids.
The propellant composition may optionally include at least one carbon compound, such as graphite, carbon fibers and/or carbon black. As a non-limiting example, the carbon black may be a high surface area carbon black having a surface area of greater than or equal to about 25 m2/g. For example, the least one carbon compound may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 5 wt % of the total weight of the propellant composition. As a non-limiting example, between about 0.02 wt % of the total weight of the propellant composition and about 1 wt % of the total weight of the propellant composition may include graphite as the at least one carbon compound.
The propellant composition may optionally include at least one solvent. Examples of such solvents include, but are not limited to, acetone, dinitrotoluene, methyl ethyl ketone, ethyl acetate, butyl acetate, propyl acetate, methyl t-butyl ether, methyl t-amyl ether and tetrahydrofuran. For example, at least one solvent may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 5 wt % of the total weight of the propellant composition. As a non-limiting example, between about 0 wt % of the total weight of the propellant composition and about 1 wt % of the total weight of the propellant composition may include ethyl acetate as the at least one solvent.
The propellant composition may optionally include at least one stabilizer. Examples of such stabilizers include, but are not limited to, 1,3-diethyl-1,3-diphenylurea (so-called “ethyl centralite” or “carbamite”), diphenylamine, N-nitrosodiphenylamine, carbonates (e.g., calcium carbonate), N-methyl-p-nitroaniline (MNA) and combinations thereof. For example, the at least one stabilizer may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 15 wt % of the total weight of the propellant composition. As a non-limiting example, between about 0 wt % of the total weight of the propellant composition and about 10 wt % of the total weight of the propellant composition may include 1,3-diethyl-1,3-diphenylurea, between about 0.3 wt % of the total weight of the propellant composition and about 1.5 wt % of the total weight of the propellant composition may include diphenylamine, between about 1 wt % of the total weight of the propellant composition and about 1.5 wt % of the total weight of the propellant composition may include N-nitrosodiphenylamine and between about 0 wt % of the total weight of the propellant composition and about 1 wt % of the total weight of the propellant composition may comprise calcium carbonate.
The propellant composition may optionally include at least one surfactant, such as rosin. For example, the at least one surfactant may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 5 wt % of the total weight of the propellant composition.
The propellant composition may optionally include at least one oxidizer. Examples of such oxidizers include, but are not limited to, nitrate compounds (e.g., potassium nitrate, lithium nitrate, beryllium nitrate, sodium nitrate, magnesium nitrate, calcium nitrate, rubidium nitrate, strontium nitrate and cesium nitrate), ammonium perchlorate (AP), ammonium nitrate (AN), hydroxylammonium nitrate (HAN), ammonium dinitramide (AND), potassium dinitramide (KDN), potassium perchlorate (KP), and combinations thereof. The at least one oxidizer may be present as a powder or in a particulate form. For example, the at least one oxidizer may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 50 wt % of the total weight of the propellant composition. As a non-limiting example, the propellant composition may include between about 0 wt % and about 1.5 wt % of the potassium nitrate as the at least one oxidizer.
The propellant composition may optionally include at least one flash suppressor, such as potassium sulfate. As a non-limiting example, between about 0 wt % of the total weight of the propellant composition and about 1.5 wt % of the total weight of the propellant composition may include potassium sulfate as the at least one flash suppressor.
The propellant composition may optionally include at least one inorganic fuel, such as a metal or metal oxide compound. Examples of such inorganic fuels include, but are not limited to, tin, iron, aluminum, copper, boron, magnesium, manganese, silicon, titanium, cobalt, zirconium, hafnium, tungsten, chromium, vanadium, nickel, oxides of iron (e.g., Fe2O3, Fe3O4, etc.), aluminum oxide (Al2O3), magnesium oxide (MgO), titanium oxide (TiO2), copper oxide (CuO), boron oxide (B2O3), silicon dioxide (SiO2), and manganese oxides (e.g., MnO, MnO2, etc.). The inorganic fuels may be present as a powder or as a particulate material. For example, the at least one inorganic fuel may be present in an amount of between about 0 wt % of the total weight of the propellant composition and about 50 wt % of the total weight of the propellant composition. As a non-limiting example, between about 0 wt % of the total weight of the propellant composition and about 1.5 wt % of the total weight of the propellant composition may include tin oxide as the at least one inorganic fuel.
Thus, the propellant composition may optionally include at least one of an inert liquid, an oxidizer, a flash suppressor, a metal fuel, a carbon compound, a solvent, a stabilizer, a surfactant and an inorganic fuel.
For example, the stabilized, encapsulated red phosphorus may be used to modify a conventional single base, double base or multi base propellant that includes the at least one energetic binder, such as nitrocellulose.
As a non-limiting example, the propellant composition may be formed by mixing or otherwise combining the stabilized, encapsulated red phosphorous with a single base propellant that includes nitrocellulose. The single base propellant may be, for example, an IMR® powder (e.g., IMR 3031™, IMR 4007SSC™, IMR 4064®, IMR 4198™, IMR 4227™, IMR 4320 ™, IMR 4350™, IMR 4576™, IMR 4759™, IMR 4831™, IMR 4895™, SR7625™ IMR 7828™, PB™ and IMR 7828SSC™), or a conventional smokeless powder (e.g., H4227®, H4895®, H4198®, VARGET®, H4350®, H50MBG®, H4831®, H4831SC®, H1000®, RETUMBO®, H322® and BENCHMARK®), each of which is commercially available from Hodgdon Powder Company, Inc. (Shawnee Mission, Kans.). For example, the single base propellant may include between about 80 wt % and about 100 wt % nitrocellulose, between about 1 wt % and about 2 wt % diphenylamine, between about 4 wt % and about 12 wt % dinitrotoluene, about 0.5 wt % potassium sulfate and less than about 1 wt % graphite.
As a non-limiting example, the propellant composition may be formed by mixing or otherwise combining the stabilized, encapsulated red phosphorous with a double base propellant that includes nitrocellulose plasticized with the energetic plasticizer. The double base propellant may be, for example, a military propellant powder (e.g., M1, M2, M7, M8, M9, WC 844, WC 860 and SMP 842). The double base propellant may include, for example, between about 10 wt % and about 90 wt % of the nitrocellulose and between about 10 wt % and about 90 wt % of the energetic plasticizer, and more particularly, between about 40 wt % and about 70 wt % of the nitrocellulose and between about 30 wt % and about 60 wt % of the energetic plasticizer.
For example, the double base propellant may be BALL POWDER® propellant, which is commercially available from St. Marks Powder, Inc. (St. Marks, Fla.), and which includes between about 0 wt % and about 42 wt % of nitroglycerin, between about 0 wt % to about 10 wt % of dibutyl phthalate, between about 0 wt % and about 10 wt % of polyester adipate, between about 0 wt % and about 10 wt % of ethyl centralite, between about 0 wt % and about 5 wt % of rosin, between about 0 wt % and about 2 wt % of ethyl acetate, between about 0.3 wt % and about 1.5 wt % of diphenylamine, between about 0 wt % and about 1.5 wt % of N-nitrosodiphenylamine, between about 0 wt % and about 1.5 wt % of potassium nitrate, between about 0 wt % and about 3 wt % of potassium sulfate, between about 0 wt % and about 1.5 wt % of tin dioxide, between about 0.02 wt % and about 1 wt % graphite, between about 0 wt % and about 1 wt % calcium carbonate and the remainder to 100 wt % of nitrocellulose.
As another non-limiting example, the double base propellant may be RELOADER® 50 smokeless powder or RELOADER® 15 smokeless powder, each of which is commercially available from Alliant Powder, Inc. (Radford, Va.). The RELOADER® 50 smokeless powder includes nitroglycerin, nitrocellulose and ARKARDIT II stabilizer (i.e., 3-methyl-1,1-diphenylurea commercially available from Synthesia, a.s. (Czech Republic). The RELOADER® 15 smokeless powder includes nitroglycerine, nitrocellulose, diphenylamine, diisoamyl phthalate and ethyl centralite.
By way of example and not limitation, the propellant composition may include between about 0.1 wt % and about 5 wt % of the stabilized, encapsulated red phosphorous (e.g., Red Phosphorus HB 801 (TP)) and between about 99.5 wt % and about 95 wt % of the double base propellant (e.g., BALL POWDER® propellant).
As another non-limiting example, the propellant composition may be formed by combining the stabilized, encapsulated red phosphorous with a multi base propellant that includes nitrocellulose plasticized with at least one energetic plasticizer, such as nitroglycerine, in addition to an energetic fuel. The energetic fuel may include at least one of nitroguanidine and a nitramine (e.g., 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo-[5.5.5.0.05,903,11]-dodecane (TEX), 1,3,5-trinitro-1,3,5-triaza-cyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraaza-cycloocatane (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.05,903,11]dodecane (CL-20), 3-nitro-1,2,4-triazol-5-one (NTO), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 1,1-diamino-2,2-dinitro ethane (DADNE), ammonium dinitramide (AND) and 1,3,3-trinitroazetidine (TNAZ)). The energetic fuel may be present in the propellant composition in an amount of between about 10 wt % of the total weight of the propellant composition and about 60 wt % of the total weight of the propellant composition.
As another non-limiting example, the propellant composition may be formed by combining the stabilized, encapsulated red phosphorous with a composite-modified multi base propellant, which includes nitrocellulose as a binder to immobilize oxidizer particles (e.g., ammonium perchlorate), inorganic fuel (e.g., aluminum) particles or binders and plasticizers. Such binders and plasticizers may include at least one of hydroxyl-terminated polybutadiene (HTPB); carboxy-terminated polybutadiene (CTB); glycidyl azide polymer (GAP); glycidyl azide polymer-based binders; oxetane polymers (e.g., 3-nitratomethyl-3-methyl oxetane (NMMO), 3,3-bis(azidomethyl)oxetane (BAMO) and 3-azidomethyl-3-methyl oxetane (AMMO)); and oxirane polymers (e.g., polyglycidyl nitrate (PGN), polyglycidyl nitrate-based polymers, polycaprolactone polymer (PCP), polybutadiene-acrylonitrile-acrylic acid terpolymer (PBAN), polyethylene glycol (PEG), polyethylene glycol-based polymers and diethyleneglycol triethyleneglycol nitraminodiacetic acid terpolymer (9DT-NIDA)).
The propellant composition may be prepared using conventional techniques, which are not described in detail herein. For example, double base and multi base propellants may be formed from nitrocellulose using conventional solventless processes or cast molding processes. Pelletized nitrocellulose (also referred to as plastisol nitrocellulose), which is available from various sources, including the U.S. Department of the Navy, may be used to form the double base and multi base propellants. Pelletized nitrocellulose includes nitrocellulose configured as pellets, as well as nitrocellulose having other configurations, including but not limited to, granular and/or particle-like (e.g., spherical) configurations. The pellets of nitrocellulose may have average diameters of between about 1 μm and about 50 μm, more particularly, between about 1 μm and about 20 μm.
The single base propellants may be formed using conventional slurry mixing techniques in which the nitrocellulose and is combined with the other ingredients.
In some embodiments, such double base and multi base propellants may be formed using a conventional slurry mixing technique in which nitrocellulose is processed by forming a slurry and the slurry is then poured, in an uncured state, into casting molds or rocket motors in a casting step. The slurry may be prepared by dispersing pelletized nitrocellulose having an average diameter of between about 1 μm and about 20 μm in a diluent, such as heptane. The energetic plasticizer (e.g., nitroglycerine) may then be added to the slurry. Optional processing agents, such as the inert liquid, the solvent, the stabilizer and the surfactant, may be added to the slurry at this stage. After removing a portion of the heptane, mixing is performed under vacuum conditions to remove additional heptane from the slurry. Optionally, the stabilized, encapsulated red phosphorus may then be added to and mixed into the slurry at this stage. Optional additives, such as the carbon compound, the oxidizer, the flash suppressor and the inorganic fuel, may also be mixed with the slurry at this stage. As a non-limiting example, after thoroughly mixing the propellant composition, a suitable cross-linker (e.g., a diisocyanate) may be added and the propellant composition may be cast and cured. As another non-limiting example, the stabilized, encapsulated red phosphorus may optionally be added to the slurry during or after addition of the cross-linker. The propellant composition may be combined to form a mixture of the stabilized, encapsulated red phosphorus and the double or multi base propellant or until the ingredients are homogeneous. For example, the stabilized, encapsulated red phosphorus may be homogeneously dispersed in the double or multi base propellant. As a non-limiting example, the propellant composition may be cast into the desired shapes, or a monolithic block of the cast propellant may be comminuted to form pieces of the desired size.
In other embodiments, the propellant composition may be formed by mixing a single, double or multi base propellant or the composite-modified multi base propellant with the desired amount of the stabilized, encapsulated red phosphorus. The mixing may be performed until a propellant composition including a combination or mixture of the stabilized, encapsulated red phosphorus and the single, double or multi base propellant or composite-modified multi base propellant with the desired amount of stabilized, encapsulated red phosphorus is formed. For example, the stabilized, encapsulated red phosphorus may be homogeneously dispersed in the single, double or multi base propellant or composite-modified multi base propellant.
Once produced, the propellant composition may be loaded into a cartridge for used in various types of ordnance, such as small arms ammunition, grenade, mortar fuse, or detcord initiator. As non-limiting examples, the propellant composition is used in a centerfire gun cartridge, a rimfire gun cartridge, or a shot shell. The propellant composition may be loaded into the cartridge using conventional techniques, such as those used in loading conventional double base propellant compositions, which are not described in detail herein.
For example, the cartridge may be a conventional military cartridge for use with a rifle, such as an M14, an M16 or an AK-47 rifle. As shown in
The propellant composition 106 may be substantially evenly distributed within the casing 104 of the cartridge 100. The propellant composition 106 may be positioned in an aperture within the casing 104, as shown in
The following examples serve to explain embodiments of the propellant composition in more detail. These examples are not to be construed as being exhaustive or exclusive as to the scope of this disclosure.
A propellant composition was prepared by mixing stabilized, encapsulated red phosphorus with a double base propellant (BALL POWDER® propellant) including nitrocellulose plasticized with nitroglycerine. The components of the double base propellant (BALL POWDER® propellant) are shown in Table 1.
0-1.5
0-1.5
0-1.5
0-1.5
The propellant composition was formed to include about 99 wt % of the double base propellant and about 1 wt % of the stabilized, encapsulated red phosphorus. The propellant composition was mixed by conventional techniques. The propellant composition is referred to herein as “composition A.”
Test articles were prepared by loading each of the propellant composition of Example 1 (composition A) and the double base propellant (BALL POWDER® propellant) into conventional cartridges with a primer, as that shown in
In the figures, the lead-based primer is referred to as “LB primer,” the stabilized, encapsulated red phosphorous-based primer is referred to as the “ERP primer,” and the double base propellant (BALL POWDER® propellant) is referred to as “DBP.” Electronic pressure velocity and action time (EPVAT) testing was performed for approximately 27 grain charge weight to determine the ballistic properties of composition A and the double base propellant in combination with either the lead-based primer or the stabilized, encapsulated red phosphorous-based primer. The ballistic properties were then compared to determine the effects of using the stabilized, encapsulated red phosphorus in the double based propellant composition and in the primer. The ballistic properties were measured at a mid-case position, a case-mouth position and a port position.
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The ballistic properties measured at the case mouth position demonstrate that the test article including composition A provides a significant reduction in the peak pressure, the time to peak pressure and the pressure impulse without a significant reduction in the average pressure. The previously discussed data show that the effects of adding the stabilized, encapsulated red phosphorus to the double base propellant results in a greater change in the ballistic properties than does adding the stabilized, encapsulated red phosphorus to the primer alone. While not wishing to be bound by any particular theory, it is believed that the magnitude of the difference between the ballistic properties of composition A and the stabilized, encapsulated red phosphorus-based primer alone suggests that changes in the ballistic properties resulting from addition of the stabilized, encapsulated red phosphorus may be mass dependent.
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Thus, as with the mid-case and case mouth pressures, the test articles including composition A provided a significant reduction in the peak pressure, the time to peak pressure and the pressure impulse in comparison to the test articles including the double based propellant. Test articles including composition A additionally provided a reduction in average port pressure in comparison to the test articles including the double based propellant. These data suggest that the reactions that reduce the pressure are still occurring as the projectile passes the port.
A mean velocity was determined for test articles including composition A and the double base propellant in combination with one of the lead-based primer and the stabilized, red phosphorus primer. As shown in
Addition of the stabilized, encapsulated red phosphorus to the double base propellant significantly modified the ballistic properties measured. More specifically, the peak pressure, the time to peak pressure and the pressure impulse were all reduced without significantly reducing the average pressure. While not wishing to be bound by any particular theory, it believed that this suggests that the stabilized, encapsulated red phosphorus may be used to reduce strain on an ordnance device or weapon system by combustion of the propellant. Addition of the stabilized, encapsulated red phosphorus to the double base propellant may also reduce the velocity provided by the propellant.
While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the following appended claims and their legal equivalents. For example, elements and features disclosed in relation to one embodiment may be combined with elements and features disclosed in relation to other embodiments of the present invention.
This application is a divisional of U.S. patent application Ser. No. 13/222,751, filed Aug. 31, 2011, pending, which is related to U.S. patent application Ser. No. 11/367,000, filed Mar. 2, 2006, now U.S. Pat. No. 7,857,921, issued Dec. 28, 2010; to U.S. patent application Ser. No. 12/978,080, filed Dec. 23, 2010, now U.S. Pat. No. 8,524,018, issued Sep. 3, 2013, entitled “Nontoxic, Noncorrosive Phosphorus-Based Primer Composition, a Percussion Cap Primer Comprising the Same, and Ordnance Including the Same;” and to U.S. patent application Ser. No. 12/194,437, filed Aug. 19, 2008, now U.S. Pat. No. 8,540,828, issued Sep. 24, 2013, and entitled “Nontoxic, Noncorrosive Phosphorus-Based Primer Compositions and an Ordnance Element Including the Same.”
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13222751 | Aug 2011 | US |
| Child | 14166521 | US |
