CA1154260A - Slurry cast double base propellants - Google Patents
Slurry cast double base propellantsInfo
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- CA1154260A CA1154260A CA000365150A CA365150A CA1154260A CA 1154260 A CA1154260 A CA 1154260A CA 000365150 A CA000365150 A CA 000365150A CA 365150 A CA365150 A CA 365150A CA 1154260 A CA1154260 A CA 1154260A
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- propellant
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
- C06B45/04—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive
- C06B45/06—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component
- C06B45/10—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component the organic component containing a resin
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
- C06B21/0033—Shaping the mixture
- C06B21/0058—Shaping the mixture by casting a curable composition, e.g. of the plastisol type
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B25/00—Compositions containing a nitrated organic compound
- C06B25/18—Compositions containing a nitrated organic compound the compound being nitrocellulose present as 10% or more by weight of the total composition
- C06B25/24—Compositions containing a nitrated organic compound the compound being nitrocellulose present as 10% or more by weight of the total composition with nitroglycerine
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Abstract
Elrick Case 1 SLURRY CAST DOUBLE BASE PROPELLANTS
Abstract of the Disclosure A slurry casting process is described capable of producing crosslinked double base propellant having improved burning rates and high specific impulse. Such propellants can be formulated to be smokeless. Improved burning rates are achieved by incorporating into a slurry of double base composition, casting powder granules containing 20% to 75% by weight of small particle ammonium perchlorate. The casting powder granules substantially retain their identity in the cured propellant matrix. The casting powder granules have a high burning rate and are uniformly distributed throughout the propellant. The granules are responsible for increasing the burning rate of the entire crosslinked double base propellant composition of the invention.
Abstract of the Disclosure A slurry casting process is described capable of producing crosslinked double base propellant having improved burning rates and high specific impulse. Such propellants can be formulated to be smokeless. Improved burning rates are achieved by incorporating into a slurry of double base composition, casting powder granules containing 20% to 75% by weight of small particle ammonium perchlorate. The casting powder granules substantially retain their identity in the cured propellant matrix. The casting powder granules have a high burning rate and are uniformly distributed throughout the propellant. The granules are responsible for increasing the burning rate of the entire crosslinked double base propellant composition of the invention.
Description
This invention relates to slurry cast crosslinked double base propellants having high burning rates, good pressure/rate exponents (n), and producing little or no primary smoke.
Large double base propellant motors are presently pre-pared by ~wo processes, conventional or "in situ" casting and"slurry casting". Each of these processes has advantages depending on the desired properties of the final propellant.
In the "in situ" casting process, casting powder granules comprised of precolloided nitrocellulose are charyecl to a mold and covered with a casting li~uid. The casting powder gran-ules are generally comprised of nitrocellulose, nitroglycerin, ammonium perchlorate, solid nitramine, stastabilizer and bal-listic modifiers. The casting liquid is typically comprised of an explosive li~uid such as nitroglycerin and a nonexplo-sive plasticizer such as triacetin or dibutylphthalate. Thenitrocellulose portion of the casting powder granules absorbs the casting liquid and swells to form a consolidated mass.
In the present crosslinked double base (XhDB~ slurry casting process a pourable slurry of propellant ingredients is prepared and the slurry is cast into a mold and cured. The slurry contains nitrocellulose in solution with other polyols which are crosslinked with polyisocyanates during cure to form a solid propellant. Fine solid oxidizers such as cyclotetra-methylenetetranitramine (HMX) are present in the slurry to increase propellant energy and to reinforce the binder system and thereby improve mechanical properties.
Advantages of the slurry casting process over "in situ"
; methods are relatively short cure times, low processing costs, improved strain capability at low temperatures, increased performance and adaptability of the process to include highly energetic and sensitive propellant ingredients in the li~2 propellant formulation because of relatively mild mixing conditions oE the slurry process.
To increase the burning rate of smokeless crosslinked double base propellants prepared by the slurry casting pro-cess, ballistic modifiers (e.g., metal compounds such as Pb2O3and SnO2 or lead salicylate and lead beta-resorcylate with carbon black) have been added to the propellant matrix during processing. These metal compvunds also aid in maintaining a satisfactory pressure/rate exponent ~n)~ Maximum burning rates of about 0.5 in./sec. at 1000 psi with n values of 0.4 to 0.6 are obtained by using relatively large amounts (2-4%
based on the weight o~ the propellant composition) of these ballistic modifiers.
Ano~her method of increasing burning rate o~ double ba~e crosslinked propellants involves the addition ,of rine ammonium perchlorate to the propellant matrix. When using this method, however, large quantities of ammonium perchlorate are required to boost burning rate. For example, burning rates of 0.37, 0.35, and 0.54 in./sec., respectively, at 1000 psi were ob-tained when 0, 5%, and 15% of 6 microns ammonium perchloratewas added at the expense of cyclotetramethylenetetranitramine (~MX) in preparation of crosslinked double base propellants that used Pb~03/ SnO2, and carbon black as ballistic modi-fiers. A decrease in ammonium perchlorate particle size does not significantly increase burniny rate when ammonium per-chlorate is present in moderate concentrations; burning rates were 0.34 and 0.55 in./sec., respectively, at 1000 psi when 5~ and 10% of 2 microns ammonium perchlorate was employed in the propellant matrix. Additional increases in burning rate have been obtained by further increases in ammonium perchlor-ate content but penalties involving increased impact and friction sensitivity and increased secondary smoke formation have been incurred.
U.S. Patent 4,080,411 describes a slurry casting process in which ~lake casting powder is combined with explosive and nonexplosive plasticizers, a polyglycol adipate-tolylene diisocyanate prepolymer, a stabilizer and a solid nitramine to prepare solid propellants. The flake casting powder described ~ 6 in U.S. Patent 4,080,411 comprises nitrocellulose and is prepared by the solvent process for manufacture of casting powder. In the solvent process a viscous propellant mass com-prising nitrocellulose and solvent is pressed into a block and extruded into small strands of propellant of circular cross-section. These small strands are cut into flakes, dried to remove all solvent, glazed with powdered graphite and screened to proper size. In the process described, uniform distribu tion of ballistic modifiers such as lead beta-resorcylate and lead salicylate in the flake casting powder is readily accom-plished by adding such ballistic modifiers to the viscous propellant mass prior to blocking and extrusion.
U.S. Patent 3,813,45~ describes a slurry casting process for manufacture of double base propellant in which metallic staple is distributed throughout the propellant to increase the propellant burning rate. The slurry casting process of U.S. Patent 3,813,458 employs both casting powder granules containing ammoniumn perchlorate and densified (plastisol) nitrocellulose as two sources of nitrocellulose in the pro-pellant. The casting powder granules are primarily included within the slurry to for~ interstices throughout the slurry which interstices are intended to trap metallic staple in the mixing process to provide uniform distribution of metallic staple throughout the propellant.
In accordance with this invention, a high specific im-pulse crosslinked double base propellant having a high burning rate is prepared by a slurry casting process comprising form-ing a propellant slurry comprising nitrocellulose, explosive plasticizer, curing agents and oxidizers. Casting powder granules are admixed with said slurry , said casting powder granules comprising from about 10% to about 25% by weight based on the weight of the propellant slurry of a double base casting powder composition which contains from about 20~ to about 75% by weight of ammonium perchlorate particles having a particle size range of from about 0.5 micron to about 3.0 microns. I'he resulting propellant composition of this inven-tion is cast and cured. Upon curing, the propellant contains casting powder particles which substantially retain their . .
r-L~
~4--identity as granules except for a slight absorption of plasti-cizer and curing agent which results in a slight size increase of the granules and except for a reaction of nitrocellulose in the propellant granule with the curing agents employed in the slurry. Because of the mixing action imparted in preparing the slurry/ discrete par~icles o~ casting powder having a high burning rate are uniformly dispersed throughout the propellant.
The castin~ powder granules which are employed in prepar-ing the propellant composition of this invention are of the double base type (contain nitrocellulose and explosive plasti-cizer) containing fine particle ammonium perchlorate and are prepared in the usual manner employed in smokeless powder man-ufacture save that anhydrous conditions and non-solvents for ammonium perchlorate are used to prevent ammonium perchlorate growth during processing. Anhydrous conditions are achieved by removal of trace quantities of moisture in nitrocellulose by azeotropic distillation of nitrocellulose with hexane.
Ethyl acetate and hexane are used as processing solvents because they are not solvents for ammonium perchlorate. The amount of fine particle ammonium perchlorate employed is limited by factors involving processability and sensitivity.
The casting powder granules can contain from about 20% to about 75% by weight of ammonium perchlorate. The particle size of the ammonium perchlorate is from about 0.5 micron to about 3.0 microns. The maximum amount of ammonium perchlorate solids which can be readily incorporated in the casting powder granules will decrease with decreasing ammonium perchlorate particle size~ Thus, up to about 75% by weight o~ ammonium perchlorate solids having a 2.0 micron particle size can be employed in casting powder granules. Above about 75%, ; processability becomes extremely difficult. When employing 0.5 micron ammonium perchlorate in a casting powder granule, about 65~ by weight of such ammonium perchlorate is the maximum amount which can be processed. The casting powder granules are employed in amounts of from about 10~ to about 25% by weight of the propellant composition.
The casting powder granules are preferably as small as is reasonably practicable, preferably the diameter and length measurements of the casting powder granules being approxi-mately equal. The length and diameter of the casting powder granules may range from about 10 mils to about 50 mils but preferably the length and diameter of the granules are about 30 mils each or less.
The nitrocellulose component of the casting powder gran-ules is preferably nitrocellulose having a nitrogen content of 12.6% N and having a 10-20 second viscosity as measured by a falling ball method (MIL-N-244A) employing a solution compris-ing 10% nitrocellulose, 10% denatured alcohol and 80% acetone.
Other grades of nitrocellulose which can also be used include those with nitrogen contents of 11.8% to 13.4% and viscositie~
of 18 centipoise (cp) to about 6000 seconds. The viscosity of 13.4~ N nitrocellulose is determined using the military speci-- fication (MIL-N-244A). Viscosities of other nitrocellulose types are determined using another falling ball method defined in ASTM D 301-56 employing a solution comprising 25% denatured alcohol, 55% toluene and 20% ethyl acetate. The nitrocellu-lose concentration employed in determining viscosity varies with the type nitrocellulose being tested. Such concentra-tions are 12.2% for 5 second or higher nitrocellulose, 20% for 1/2 and 3/4 second nitrocellulose and 25~ for 18-25 cp, 30-35 cp, 1/4 second and 3/8 second nitrocelluloses. Nitrocellulose comprises from about 5~ to about 40% by weight of the casting powder granula.
Plasticizers employed in preparations of the casting powder granules are explosive liquids such as nitroglycerin, butanetriol trinitrate, trimetriol trinitrate, and the like.
These plasticizers are employed in the casting powder granules in amounts of from about 10% to about 40~ by weight.
In addition to ammonium perchlorate, nitrocellulose and plasticizer, additional ingredients such as other polyols, aluminum oxide, ballistic modifiers, graphite linters, alumi-num or zirconium staples, carbon black and various stabiizers can be included in the casting powder granules. The concen-tration ranges of these optional inyredients (weight percent) f~
which can be employed are set forth in Table I below.
Table I
Polyol (other than Nitrocellulose) 0-40%
Al23 0-3%
Ballistic Modifiers 0-4%
Graphite Linters or Metal Staples 0-5%
Carbon Black (powder) 0-0.5~
Stabilizers 1-3.0%
The initial slurry of the propellant, i.e., th~ propel-lant slurry excluding the casting powder granules, is prepared from nitrocellulose, polyol, curing agent, organic oxidizers, explosive plasticizers, stabilizers and minor amounts of other ingredients. The preferred nitrocellulose is low viscosity nitrocellulose containing 12% ~ and having a viscosity of 18 cps-25 cps (measured at 25C. using 25~ nitrocellulose and a solvent containing 25% ethanol, 55% toluene and 20% ethyl-acetate? and an approximate intrinsic viscosity of 0.4 deciliters/gram (determined using acetone solvent). Other nitrocellulose types with viscosities of up to 5 seconds can also be used. Viscosity of 5 second nitrocellulose is determined using the above solvent at 12.2% nitrocellulose concentration.
Polyols that can be employed in the initial slurry of the propellant are polyester polyols, polyethylene glycols, poly(oxyethylene-butylene) glycols, and polycaprolactones.
The polyols employed generally have a molecular weight range of from about 2000 to about 6000 and a hydroxyl functionality of from about 2 to about 3. Polyester diols which can be employed can be prepared by reaction of monomeric dialcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol hexamethylene glycol, mixtures thereof and the like, with dibasic acids such as adipic acid, succinic acid, azelaic acid, sebacic acid, oxadibutyric acid, mixtures thereof, and the like. Polyglycol adipate is a preferred polyol to be employed with nitrocellulose in the initial slurry of the propellant.
The combination oE nitrocellulose and polyols comprises Erom about 5% to about 12% by weight of the initial propellant slurry. The nitrocellulose content can be from 0~ to about 4%
~f~ 6V
and the polyol from about 1~ to about 12~. The preferred initial slurry contains from a~out 0.4% to 2.0% nitrocellulose and from about 4% to about 7% polyol, preferably polyglycol adipate.
Plasticizers employed in preparations of the initial slurry are explosive liquids such as nitroglycerin, butane-triol trinitrate, trimetriol trinitrate, and the like. These plasticizers are employed in the initial slurry in amounts of from about 5% to about 50~ by wei-ght.
Polyfunctional isocyanates are employed as curing agents for the nitrocellulose and polyols which form the binder of the propellant compositions of this invention. The polyfunc-tional isocyanates which can be employed have an NCO function-ality of two or more. Illustrative polyfunctional isocyanates which can be employed include tolylene diisocyanate, hexa-methylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexaneisocyanate, isocyanates having a functionality Orc 3 or more prepared by reaction of diisocyanates such as hexa-methylene diisocyanates and water, and the like. Curing agents are generally employed in amounts of from about 0O8%
to about 2% based on the weight of the initial slurry, but greater and smaller concentrations can be employed. In addi-tion to the polyfunctional isocyanate curing agent, a curing catalyst is preferably employed to speed the rate of cure of the propellant by catalyzing the reaction of isocyanate groups with hydroxyl groups. Il~ustrative curing catalysts include triphenyl bismuth (TPB), dibutyl tin diacetate (DBTDA), and dibutyl tin diluarate.
Organic oxidizer solids can be employed in the propellant slurry. Illustrative organic o~idizers include cyclotetra-methylenetetranitramine (HMX); cyclotrimethylenetrinitramine (RDXl; solid nitramines such as 2,5-dinitrazahexane and solid nitro compounds such as hexanitrostilbene and nitroguanidine.
The solid organic oxidizers employed must have a small par-ticle size so that they can be dispersed readily through thepropellant mass ancl remain uniformly dispersed after mixing has been completed. Organic oxidizers comprise from about l~Ci~
30% to about 50% by weight of the initial slurry/ but greater and smaller concentrations can be employed.
The following examples further illustrate this invention.
In the examples and throughout this specification, percentages are by weight unless specified otherwise.
Exam~les 1-4 Casting powder granules employed in the slurry process of this invention are prepared as follows:
Hexane~wet nitrocellulose, nitroglycerin, ammonium per-chlorate, stabilizer, ultrafine carbon black and 1/2 inchlength graphite linters are mixed in a sigma blade mixer using a mixture of hexane and ethyl acetate as processing solvents in sufficient quantities to produce a propellant dough. The resulting dough is pressed through 30 mil dies to obtain strands which are cut into 27 mil length casting powder.
Residual solvents are removed by oven drying to obtain casting powder, composi~ion A. Composi~ion ~ is prepared in the same manner as composition A blt it contains A12O3~ The casting powder compositions are se~ forth in Table II below.
Table II
Castin~_~owder Composition (~) A B
Nitrocellulose 29.00 28.00 (12.6%, 10 sec.) Nitroglycerin 25.24 25.24 Stabilizer 2.76 2.76 Ammonium perchlorate (2 ) 40.00 40.00 Graphite linters(a) 3.00 3.00 A123 1.00 (a) Graphite linters, nominal diameter of 10 , Type HMS
manufactured ~y Hercules Incorporated.
Slurries containing casting powder granu]~es of composi-tions A and B are prepared by forming an initial slurry by mixing of ingredients, i e.l a lacquer containing 18-~5 cp nitrocellulose and nitroglycerin, additional nitroglycerin, stabilizers, a polyglycol adipate, small particle sized HMX
and cure catalysts (TPB and DBTDA) at reduced pressure ( 15 mm Hg) adding hexamethylene diisocyanate curing agent and then adding casting powder granules to the slurry and mixing again at the reduced pressure of 15 mm Hg. Additional ballistic modifiers are also added to the propellant slurry in preparing the propellant composition of Example 2. The initial propel-lant slurries, i.e., prior to addition of the casting powder granules have the compositions set forth in Table III:
Table III
-Example No. 1 2 3 4 Casting Powder Comp. Comp. Comp. Comp.
"A" "A" "B" "A"
Slurry Composition (parts) Nitrocellulose,1.29 1.29 1.29 1.29 12% N (18-25 cp) Nitroglycerin 35.92 35.92 35.92 35.92 Polyglycol 5.46 5.38 5.51 5.~3 adipate Stabilizer-l 0.86 0.86 0.86 0.84 Stabilizer-2 0.36 0.36 0.36 0.3~
Hexamethylene 0.99 1.07 0.94 0.81 diisocyanate HMX (5 microns)40.12 38.25 40.12 37.76 SnO2 - 0.85 - _ Pb23 - 0.85 - _ 3~ Carbon black(a) _ 0.17 TPB (added)(b) 0.02 0.0~ 0.02 0.02 DBTDA X104 (c) 8 8 8 7 (a) Ultrafine carbon black having a surface area of 1125 m2/gram.
(b) TPB is triphenyl bismuth.
(c) DBTDA is dibutyl tin diacetate.
The resulting slurries to which the casting powder has been added ar~ each mixed for 15-20 minutes at 100-110F. at reduced pressure. The propellants are then cast into molds and cured for 4 days at 50-70F. and 7 days at 120F. The initial low temperature cure is used to permit some exchange of plasticizers between slurry and casting powder and to per-mit some absorption of curing agent into the casting powder while the 120F. cure is used primarily to allow curing agent to react with functional hydroxyl groups in nitrocellulose and polyglycol adipate and thereby solidify the propellant.
The composition of each of the resulting propellants is given in Table IV.
Table IV
Ex.l Ex.2 E~.3 Ex.4 Composition Nitrocellulose 4.35 4.35 4u205.80 (12.6~ N, 10 sec.) Nitrocellulose 1.29 1.29 1.291.22 ~ 25 cp) Polyglycol 0 5.38 0 0 adipate (a) Polyglycol 5.46 0 5.515.23 adipate (b) Nitroglycerin 39.70 39.70 39.7038.85 Stabilizer 0.55 0.55 0.550.59 Stabilizer 0.94 0.94 0.940.91 Stabilizer 0.15 0.15 0.150.20 Hexamethylene 0.99 1.07 0.940.84 diisocyanate HMX ~5 microns) 40.12 38.25 40.1237.76 Ammonium 6.00 6.00 6.008.00 perchlorate (2 microns) Graphite hinters (c) 0.45 G.45 0.45 0.60 Carbon Bla-ck (d) 0 0.17 0 0 SnO2 0 0.85 0 0 Pb23 0 0O85 0 0 A12O3 (0.1 micron) 0 0 0.15 0 (a) Polyglycol adipate, hydroxyl functionality of about 2.7, molecular weight of about 2400.
(b) Polyglycol adipate, hydroxyl functionality of about 2.7, molecular weight of about 4,000.
(c) See footnote (a), Table II.
(d) Ultra~ine carbon black having a surface area of about 1125 m2/gram.
; 35 The propellant compositions of Examples 1-4 were evalu-ated for rheological properties, ballistic data and mechanical properties. Results of these evaluation tests are set orth in Table V.
.., ~5 Table V
Ex.l Ex.2 Ex.3 Ex.4 Rheolo~ical Properties Viscosity ~kp~(a) 3.7 3.4 4.0 4.2 n~(b) 0.39 0.45 0.47 0.56 Pot Life (hours~ 4~ (c) (c) 5 Strand Ballistic Data . .
rlooo (in./sec.~ 0.87 0.95 0O94 1.05 n from 500-1000 p~i 0.65 0.61 0.77 0.69 n from 1000-1500 psi 0.65 0.61 0.50 0.69 n from 1500-2000 psi 0.78 0.61 - 0.69 Mechanical Properties at 77F. at 0.74 in./in./min. (Instron Tester) Tensile 76 88 78 92 Strength (psi) Elongation ~) 26 42 39 30 Modulus (psi~ 440 360 340 540 (a) Viscosity at 32C. at 0.57 sec.~l (b) Flow behavior index (dimensionless) ~0 (c) Not determined Of the foregoing examples, the propellants of Examples 1 and 4 illustrate preferred embodiments because their compo-sitions do not contain metal oxides as do the propellants of Examples 2 and 3. The compositions of Examples 1, 3 and 4 do not produce primary smoke upon combustion. Primary smoke is visible because of the presence of particles of metal reaction products in the propellant exhaust. Lead compounds which further augment the burning rate of the propellant composi-tions of this invention react during combustion forming lead chloride which augments smoke visibility. In order to main-tain smokelessness, metals are preferably omltted from the propellant compositions of this invention or employed in small amounts, say of less than 2~ by weight of the propellant composition.
Secondary smoke is a contrail of visible water crystals or droplets which form as a result oE the hygroscopic action of hydrogen chloride in the exhaust with water vapor. The visibility of secondary smoke is increased by decreasing temperature or by increasing relative humidity. Propellants containing ammonium perchlorate produce some secondary smoke.
The propellants of this invention exhibit high burning rates but employ comparatively low amounts of ammonium perchlorate and, therefore, produce low amounts of secondary smoke. Com-posite propellants are comprised almost entirely of ammoniumperchlorate and secondary smoke evolution of composite propellants is high.
The propellant compositions of this invention have a rel-atively high specific impulse largely because of the presence of a relatively large amount o solid organizer, such as cyclotetramethylene tetranitramine (HMX) in the propellant.
High burning rates can be obtained despite the presence of the large amounts of the solid organic oxidizers such as HMX which tend to depress the burning rate. Burning rate is high be-cause of the relatively high concentration of ammoniump~rchlorate in discrete areas which are uniformly distributed throughout the propellant.
Propellants of this invention have advantages over pro-pellants prepared by a slurry casting process containing fIake - 20 casting powder. Burning rates are higher and pot life is longer for propellants of this invention. Propellant slurries of this invention can have a pot life in excess of ive hours ; compared to a 20-60 minute pot life or slurries containing flake casting powder.
Large double base propellant motors are presently pre-pared by ~wo processes, conventional or "in situ" casting and"slurry casting". Each of these processes has advantages depending on the desired properties of the final propellant.
In the "in situ" casting process, casting powder granules comprised of precolloided nitrocellulose are charyecl to a mold and covered with a casting li~uid. The casting powder gran-ules are generally comprised of nitrocellulose, nitroglycerin, ammonium perchlorate, solid nitramine, stastabilizer and bal-listic modifiers. The casting liquid is typically comprised of an explosive li~uid such as nitroglycerin and a nonexplo-sive plasticizer such as triacetin or dibutylphthalate. Thenitrocellulose portion of the casting powder granules absorbs the casting liquid and swells to form a consolidated mass.
In the present crosslinked double base (XhDB~ slurry casting process a pourable slurry of propellant ingredients is prepared and the slurry is cast into a mold and cured. The slurry contains nitrocellulose in solution with other polyols which are crosslinked with polyisocyanates during cure to form a solid propellant. Fine solid oxidizers such as cyclotetra-methylenetetranitramine (HMX) are present in the slurry to increase propellant energy and to reinforce the binder system and thereby improve mechanical properties.
Advantages of the slurry casting process over "in situ"
; methods are relatively short cure times, low processing costs, improved strain capability at low temperatures, increased performance and adaptability of the process to include highly energetic and sensitive propellant ingredients in the li~2 propellant formulation because of relatively mild mixing conditions oE the slurry process.
To increase the burning rate of smokeless crosslinked double base propellants prepared by the slurry casting pro-cess, ballistic modifiers (e.g., metal compounds such as Pb2O3and SnO2 or lead salicylate and lead beta-resorcylate with carbon black) have been added to the propellant matrix during processing. These metal compvunds also aid in maintaining a satisfactory pressure/rate exponent ~n)~ Maximum burning rates of about 0.5 in./sec. at 1000 psi with n values of 0.4 to 0.6 are obtained by using relatively large amounts (2-4%
based on the weight o~ the propellant composition) of these ballistic modifiers.
Ano~her method of increasing burning rate o~ double ba~e crosslinked propellants involves the addition ,of rine ammonium perchlorate to the propellant matrix. When using this method, however, large quantities of ammonium perchlorate are required to boost burning rate. For example, burning rates of 0.37, 0.35, and 0.54 in./sec., respectively, at 1000 psi were ob-tained when 0, 5%, and 15% of 6 microns ammonium perchloratewas added at the expense of cyclotetramethylenetetranitramine (~MX) in preparation of crosslinked double base propellants that used Pb~03/ SnO2, and carbon black as ballistic modi-fiers. A decrease in ammonium perchlorate particle size does not significantly increase burniny rate when ammonium per-chlorate is present in moderate concentrations; burning rates were 0.34 and 0.55 in./sec., respectively, at 1000 psi when 5~ and 10% of 2 microns ammonium perchlorate was employed in the propellant matrix. Additional increases in burning rate have been obtained by further increases in ammonium perchlor-ate content but penalties involving increased impact and friction sensitivity and increased secondary smoke formation have been incurred.
U.S. Patent 4,080,411 describes a slurry casting process in which ~lake casting powder is combined with explosive and nonexplosive plasticizers, a polyglycol adipate-tolylene diisocyanate prepolymer, a stabilizer and a solid nitramine to prepare solid propellants. The flake casting powder described ~ 6 in U.S. Patent 4,080,411 comprises nitrocellulose and is prepared by the solvent process for manufacture of casting powder. In the solvent process a viscous propellant mass com-prising nitrocellulose and solvent is pressed into a block and extruded into small strands of propellant of circular cross-section. These small strands are cut into flakes, dried to remove all solvent, glazed with powdered graphite and screened to proper size. In the process described, uniform distribu tion of ballistic modifiers such as lead beta-resorcylate and lead salicylate in the flake casting powder is readily accom-plished by adding such ballistic modifiers to the viscous propellant mass prior to blocking and extrusion.
U.S. Patent 3,813,45~ describes a slurry casting process for manufacture of double base propellant in which metallic staple is distributed throughout the propellant to increase the propellant burning rate. The slurry casting process of U.S. Patent 3,813,458 employs both casting powder granules containing ammoniumn perchlorate and densified (plastisol) nitrocellulose as two sources of nitrocellulose in the pro-pellant. The casting powder granules are primarily included within the slurry to for~ interstices throughout the slurry which interstices are intended to trap metallic staple in the mixing process to provide uniform distribution of metallic staple throughout the propellant.
In accordance with this invention, a high specific im-pulse crosslinked double base propellant having a high burning rate is prepared by a slurry casting process comprising form-ing a propellant slurry comprising nitrocellulose, explosive plasticizer, curing agents and oxidizers. Casting powder granules are admixed with said slurry , said casting powder granules comprising from about 10% to about 25% by weight based on the weight of the propellant slurry of a double base casting powder composition which contains from about 20~ to about 75% by weight of ammonium perchlorate particles having a particle size range of from about 0.5 micron to about 3.0 microns. I'he resulting propellant composition of this inven-tion is cast and cured. Upon curing, the propellant contains casting powder particles which substantially retain their . .
r-L~
~4--identity as granules except for a slight absorption of plasti-cizer and curing agent which results in a slight size increase of the granules and except for a reaction of nitrocellulose in the propellant granule with the curing agents employed in the slurry. Because of the mixing action imparted in preparing the slurry/ discrete par~icles o~ casting powder having a high burning rate are uniformly dispersed throughout the propellant.
The castin~ powder granules which are employed in prepar-ing the propellant composition of this invention are of the double base type (contain nitrocellulose and explosive plasti-cizer) containing fine particle ammonium perchlorate and are prepared in the usual manner employed in smokeless powder man-ufacture save that anhydrous conditions and non-solvents for ammonium perchlorate are used to prevent ammonium perchlorate growth during processing. Anhydrous conditions are achieved by removal of trace quantities of moisture in nitrocellulose by azeotropic distillation of nitrocellulose with hexane.
Ethyl acetate and hexane are used as processing solvents because they are not solvents for ammonium perchlorate. The amount of fine particle ammonium perchlorate employed is limited by factors involving processability and sensitivity.
The casting powder granules can contain from about 20% to about 75% by weight of ammonium perchlorate. The particle size of the ammonium perchlorate is from about 0.5 micron to about 3.0 microns. The maximum amount of ammonium perchlorate solids which can be readily incorporated in the casting powder granules will decrease with decreasing ammonium perchlorate particle size~ Thus, up to about 75% by weight o~ ammonium perchlorate solids having a 2.0 micron particle size can be employed in casting powder granules. Above about 75%, ; processability becomes extremely difficult. When employing 0.5 micron ammonium perchlorate in a casting powder granule, about 65~ by weight of such ammonium perchlorate is the maximum amount which can be processed. The casting powder granules are employed in amounts of from about 10~ to about 25% by weight of the propellant composition.
The casting powder granules are preferably as small as is reasonably practicable, preferably the diameter and length measurements of the casting powder granules being approxi-mately equal. The length and diameter of the casting powder granules may range from about 10 mils to about 50 mils but preferably the length and diameter of the granules are about 30 mils each or less.
The nitrocellulose component of the casting powder gran-ules is preferably nitrocellulose having a nitrogen content of 12.6% N and having a 10-20 second viscosity as measured by a falling ball method (MIL-N-244A) employing a solution compris-ing 10% nitrocellulose, 10% denatured alcohol and 80% acetone.
Other grades of nitrocellulose which can also be used include those with nitrogen contents of 11.8% to 13.4% and viscositie~
of 18 centipoise (cp) to about 6000 seconds. The viscosity of 13.4~ N nitrocellulose is determined using the military speci-- fication (MIL-N-244A). Viscosities of other nitrocellulose types are determined using another falling ball method defined in ASTM D 301-56 employing a solution comprising 25% denatured alcohol, 55% toluene and 20% ethyl acetate. The nitrocellu-lose concentration employed in determining viscosity varies with the type nitrocellulose being tested. Such concentra-tions are 12.2% for 5 second or higher nitrocellulose, 20% for 1/2 and 3/4 second nitrocellulose and 25~ for 18-25 cp, 30-35 cp, 1/4 second and 3/8 second nitrocelluloses. Nitrocellulose comprises from about 5~ to about 40% by weight of the casting powder granula.
Plasticizers employed in preparations of the casting powder granules are explosive liquids such as nitroglycerin, butanetriol trinitrate, trimetriol trinitrate, and the like.
These plasticizers are employed in the casting powder granules in amounts of from about 10% to about 40~ by weight.
In addition to ammonium perchlorate, nitrocellulose and plasticizer, additional ingredients such as other polyols, aluminum oxide, ballistic modifiers, graphite linters, alumi-num or zirconium staples, carbon black and various stabiizers can be included in the casting powder granules. The concen-tration ranges of these optional inyredients (weight percent) f~
which can be employed are set forth in Table I below.
Table I
Polyol (other than Nitrocellulose) 0-40%
Al23 0-3%
Ballistic Modifiers 0-4%
Graphite Linters or Metal Staples 0-5%
Carbon Black (powder) 0-0.5~
Stabilizers 1-3.0%
The initial slurry of the propellant, i.e., th~ propel-lant slurry excluding the casting powder granules, is prepared from nitrocellulose, polyol, curing agent, organic oxidizers, explosive plasticizers, stabilizers and minor amounts of other ingredients. The preferred nitrocellulose is low viscosity nitrocellulose containing 12% ~ and having a viscosity of 18 cps-25 cps (measured at 25C. using 25~ nitrocellulose and a solvent containing 25% ethanol, 55% toluene and 20% ethyl-acetate? and an approximate intrinsic viscosity of 0.4 deciliters/gram (determined using acetone solvent). Other nitrocellulose types with viscosities of up to 5 seconds can also be used. Viscosity of 5 second nitrocellulose is determined using the above solvent at 12.2% nitrocellulose concentration.
Polyols that can be employed in the initial slurry of the propellant are polyester polyols, polyethylene glycols, poly(oxyethylene-butylene) glycols, and polycaprolactones.
The polyols employed generally have a molecular weight range of from about 2000 to about 6000 and a hydroxyl functionality of from about 2 to about 3. Polyester diols which can be employed can be prepared by reaction of monomeric dialcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol hexamethylene glycol, mixtures thereof and the like, with dibasic acids such as adipic acid, succinic acid, azelaic acid, sebacic acid, oxadibutyric acid, mixtures thereof, and the like. Polyglycol adipate is a preferred polyol to be employed with nitrocellulose in the initial slurry of the propellant.
The combination oE nitrocellulose and polyols comprises Erom about 5% to about 12% by weight of the initial propellant slurry. The nitrocellulose content can be from 0~ to about 4%
~f~ 6V
and the polyol from about 1~ to about 12~. The preferred initial slurry contains from a~out 0.4% to 2.0% nitrocellulose and from about 4% to about 7% polyol, preferably polyglycol adipate.
Plasticizers employed in preparations of the initial slurry are explosive liquids such as nitroglycerin, butane-triol trinitrate, trimetriol trinitrate, and the like. These plasticizers are employed in the initial slurry in amounts of from about 5% to about 50~ by wei-ght.
Polyfunctional isocyanates are employed as curing agents for the nitrocellulose and polyols which form the binder of the propellant compositions of this invention. The polyfunc-tional isocyanates which can be employed have an NCO function-ality of two or more. Illustrative polyfunctional isocyanates which can be employed include tolylene diisocyanate, hexa-methylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexaneisocyanate, isocyanates having a functionality Orc 3 or more prepared by reaction of diisocyanates such as hexa-methylene diisocyanates and water, and the like. Curing agents are generally employed in amounts of from about 0O8%
to about 2% based on the weight of the initial slurry, but greater and smaller concentrations can be employed. In addi-tion to the polyfunctional isocyanate curing agent, a curing catalyst is preferably employed to speed the rate of cure of the propellant by catalyzing the reaction of isocyanate groups with hydroxyl groups. Il~ustrative curing catalysts include triphenyl bismuth (TPB), dibutyl tin diacetate (DBTDA), and dibutyl tin diluarate.
Organic oxidizer solids can be employed in the propellant slurry. Illustrative organic o~idizers include cyclotetra-methylenetetranitramine (HMX); cyclotrimethylenetrinitramine (RDXl; solid nitramines such as 2,5-dinitrazahexane and solid nitro compounds such as hexanitrostilbene and nitroguanidine.
The solid organic oxidizers employed must have a small par-ticle size so that they can be dispersed readily through thepropellant mass ancl remain uniformly dispersed after mixing has been completed. Organic oxidizers comprise from about l~Ci~
30% to about 50% by weight of the initial slurry/ but greater and smaller concentrations can be employed.
The following examples further illustrate this invention.
In the examples and throughout this specification, percentages are by weight unless specified otherwise.
Exam~les 1-4 Casting powder granules employed in the slurry process of this invention are prepared as follows:
Hexane~wet nitrocellulose, nitroglycerin, ammonium per-chlorate, stabilizer, ultrafine carbon black and 1/2 inchlength graphite linters are mixed in a sigma blade mixer using a mixture of hexane and ethyl acetate as processing solvents in sufficient quantities to produce a propellant dough. The resulting dough is pressed through 30 mil dies to obtain strands which are cut into 27 mil length casting powder.
Residual solvents are removed by oven drying to obtain casting powder, composi~ion A. Composi~ion ~ is prepared in the same manner as composition A blt it contains A12O3~ The casting powder compositions are se~ forth in Table II below.
Table II
Castin~_~owder Composition (~) A B
Nitrocellulose 29.00 28.00 (12.6%, 10 sec.) Nitroglycerin 25.24 25.24 Stabilizer 2.76 2.76 Ammonium perchlorate (2 ) 40.00 40.00 Graphite linters(a) 3.00 3.00 A123 1.00 (a) Graphite linters, nominal diameter of 10 , Type HMS
manufactured ~y Hercules Incorporated.
Slurries containing casting powder granu]~es of composi-tions A and B are prepared by forming an initial slurry by mixing of ingredients, i e.l a lacquer containing 18-~5 cp nitrocellulose and nitroglycerin, additional nitroglycerin, stabilizers, a polyglycol adipate, small particle sized HMX
and cure catalysts (TPB and DBTDA) at reduced pressure ( 15 mm Hg) adding hexamethylene diisocyanate curing agent and then adding casting powder granules to the slurry and mixing again at the reduced pressure of 15 mm Hg. Additional ballistic modifiers are also added to the propellant slurry in preparing the propellant composition of Example 2. The initial propel-lant slurries, i.e., prior to addition of the casting powder granules have the compositions set forth in Table III:
Table III
-Example No. 1 2 3 4 Casting Powder Comp. Comp. Comp. Comp.
"A" "A" "B" "A"
Slurry Composition (parts) Nitrocellulose,1.29 1.29 1.29 1.29 12% N (18-25 cp) Nitroglycerin 35.92 35.92 35.92 35.92 Polyglycol 5.46 5.38 5.51 5.~3 adipate Stabilizer-l 0.86 0.86 0.86 0.84 Stabilizer-2 0.36 0.36 0.36 0.3~
Hexamethylene 0.99 1.07 0.94 0.81 diisocyanate HMX (5 microns)40.12 38.25 40.12 37.76 SnO2 - 0.85 - _ Pb23 - 0.85 - _ 3~ Carbon black(a) _ 0.17 TPB (added)(b) 0.02 0.0~ 0.02 0.02 DBTDA X104 (c) 8 8 8 7 (a) Ultrafine carbon black having a surface area of 1125 m2/gram.
(b) TPB is triphenyl bismuth.
(c) DBTDA is dibutyl tin diacetate.
The resulting slurries to which the casting powder has been added ar~ each mixed for 15-20 minutes at 100-110F. at reduced pressure. The propellants are then cast into molds and cured for 4 days at 50-70F. and 7 days at 120F. The initial low temperature cure is used to permit some exchange of plasticizers between slurry and casting powder and to per-mit some absorption of curing agent into the casting powder while the 120F. cure is used primarily to allow curing agent to react with functional hydroxyl groups in nitrocellulose and polyglycol adipate and thereby solidify the propellant.
The composition of each of the resulting propellants is given in Table IV.
Table IV
Ex.l Ex.2 E~.3 Ex.4 Composition Nitrocellulose 4.35 4.35 4u205.80 (12.6~ N, 10 sec.) Nitrocellulose 1.29 1.29 1.291.22 ~ 25 cp) Polyglycol 0 5.38 0 0 adipate (a) Polyglycol 5.46 0 5.515.23 adipate (b) Nitroglycerin 39.70 39.70 39.7038.85 Stabilizer 0.55 0.55 0.550.59 Stabilizer 0.94 0.94 0.940.91 Stabilizer 0.15 0.15 0.150.20 Hexamethylene 0.99 1.07 0.940.84 diisocyanate HMX ~5 microns) 40.12 38.25 40.1237.76 Ammonium 6.00 6.00 6.008.00 perchlorate (2 microns) Graphite hinters (c) 0.45 G.45 0.45 0.60 Carbon Bla-ck (d) 0 0.17 0 0 SnO2 0 0.85 0 0 Pb23 0 0O85 0 0 A12O3 (0.1 micron) 0 0 0.15 0 (a) Polyglycol adipate, hydroxyl functionality of about 2.7, molecular weight of about 2400.
(b) Polyglycol adipate, hydroxyl functionality of about 2.7, molecular weight of about 4,000.
(c) See footnote (a), Table II.
(d) Ultra~ine carbon black having a surface area of about 1125 m2/gram.
; 35 The propellant compositions of Examples 1-4 were evalu-ated for rheological properties, ballistic data and mechanical properties. Results of these evaluation tests are set orth in Table V.
.., ~5 Table V
Ex.l Ex.2 Ex.3 Ex.4 Rheolo~ical Properties Viscosity ~kp~(a) 3.7 3.4 4.0 4.2 n~(b) 0.39 0.45 0.47 0.56 Pot Life (hours~ 4~ (c) (c) 5 Strand Ballistic Data . .
rlooo (in./sec.~ 0.87 0.95 0O94 1.05 n from 500-1000 p~i 0.65 0.61 0.77 0.69 n from 1000-1500 psi 0.65 0.61 0.50 0.69 n from 1500-2000 psi 0.78 0.61 - 0.69 Mechanical Properties at 77F. at 0.74 in./in./min. (Instron Tester) Tensile 76 88 78 92 Strength (psi) Elongation ~) 26 42 39 30 Modulus (psi~ 440 360 340 540 (a) Viscosity at 32C. at 0.57 sec.~l (b) Flow behavior index (dimensionless) ~0 (c) Not determined Of the foregoing examples, the propellants of Examples 1 and 4 illustrate preferred embodiments because their compo-sitions do not contain metal oxides as do the propellants of Examples 2 and 3. The compositions of Examples 1, 3 and 4 do not produce primary smoke upon combustion. Primary smoke is visible because of the presence of particles of metal reaction products in the propellant exhaust. Lead compounds which further augment the burning rate of the propellant composi-tions of this invention react during combustion forming lead chloride which augments smoke visibility. In order to main-tain smokelessness, metals are preferably omltted from the propellant compositions of this invention or employed in small amounts, say of less than 2~ by weight of the propellant composition.
Secondary smoke is a contrail of visible water crystals or droplets which form as a result oE the hygroscopic action of hydrogen chloride in the exhaust with water vapor. The visibility of secondary smoke is increased by decreasing temperature or by increasing relative humidity. Propellants containing ammonium perchlorate produce some secondary smoke.
The propellants of this invention exhibit high burning rates but employ comparatively low amounts of ammonium perchlorate and, therefore, produce low amounts of secondary smoke. Com-posite propellants are comprised almost entirely of ammoniumperchlorate and secondary smoke evolution of composite propellants is high.
The propellant compositions of this invention have a rel-atively high specific impulse largely because of the presence of a relatively large amount o solid organizer, such as cyclotetramethylene tetranitramine (HMX) in the propellant.
High burning rates can be obtained despite the presence of the large amounts of the solid organic oxidizers such as HMX which tend to depress the burning rate. Burning rate is high be-cause of the relatively high concentration of ammoniump~rchlorate in discrete areas which are uniformly distributed throughout the propellant.
Propellants of this invention have advantages over pro-pellants prepared by a slurry casting process containing fIake - 20 casting powder. Burning rates are higher and pot life is longer for propellants of this invention. Propellant slurries of this invention can have a pot life in excess of ive hours ; compared to a 20-60 minute pot life or slurries containing flake casting powder.
Claims (5)
- The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
l. A process for preparation of slurry cast propellant compositions which exhibit improved burning rates, said process comprising (a) preparing an initial propellant slurry comprising a casting solvent, low viscosity nitrocellulose containing 12.0% nitrogen, a polyol having a molecular weight of from about 2000 to about 6000 and a hydroxyl functionality of from about 2 to about 3, a polyfunctional isocyanate cross-linking agent, and solid oxidizing agents selected front organic nitramines and organic nitro compounds; (b) admixing double base casting powder granules with said propellant slurry, said casting powder granules comprising from about 10%
to about 25% by weight, based on the weight of the resulting propellant slurry, said casting powder granules containing from about 20% to about 75% ammonium perchlorate having a par-ticle size range of from about 0.5 micron to about 3.0 microns provided that if about 50% of the ammonium perchlorate in said granules has a particle size of about 0.5 micron the total ammonium perchlorate content of said casting powder shall not exceed 65% by weight; (c) casting the slurry of step (b); and (d) curing said slurry forming a crosslinked double base propellant composition. - 2. The process of claim l in which the initial propel-lant slurry of step (a) comprises from about 5% to about 50%
of nitroglycerin, from about 5% to about 12% of nitrocellulose containing 12% N and having a viscosity of 18-25 centipoises and polyglycol adipate, from about 0.8% to about 2.0% of crosslinking agent, and from about 30% to about 50% of solid organic oxidizer. - 3. The process of claim 2 in which the casting powder granules of step (b) comprises from about 20% to about 75% of ammonium perchlorate, from about 5% to about 40% of nitrocellulose containing 12.6% N and having a viscosity of 10-20 seconds, and from about 10% to about 40% of explosive plasticizer.
- 4. A crosslinked double base propellant composition prepared by a slurry casting process comprising a cured admixture of a propellant matrix containing casting powder identifiable as discrete particles within said cured propellant matrix, said propellant matrix comprising an explosive plasticizer, nitrocellulose contain-ing 12.0% N and having a viscosity of from 12 cp to about 25 cp, a polyol having a molecular weight of from about 2000 to about 6000 and a hydroxyl functionality of from about 2 to 3, a polyfunctional isocyanate crosslinking agent and solid oxidizing agents selected from organic nitramines and organic nitro compounds, and a multi-plicity of casting powder granules uniformly distributed throughout to about 25% by weight propellant composition, said casting powder granules containing from about 20% to about 75% ammonium perchlorate having a particle size range of from about 0.5 micron to about 3.0 microns, provided that if about 50% of the ammonium perchlorate has a particle size of about 0.5 micron the total ammonium perchlorate content shall not exceed about 65% by weight of the casting powder granule.
- 5. The smokeless, crosslinked double base propellant composition of claim 4 in which the nitrocellulose employed has a viscosity of from 12 to 18 centipoise, the polyol employed is polyglycoladipate and the solid oxidizing agent is cyclotetram-ethylene tetranitramine.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10826879A | 1979-12-28 | 1979-12-28 | |
| US108,268 | 1979-12-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154260A true CA1154260A (en) | 1983-09-27 |
Family
ID=22321207
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000365150A Expired CA1154260A (en) | 1979-12-28 | 1980-11-20 | Slurry cast double base propellants |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0031682A3 (en) |
| JP (1) | JPS56100194A (en) |
| CA (1) | CA1154260A (en) |
| NO (1) | NO803572L (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5864297A (en) * | 1981-10-09 | 1983-04-16 | 日産自動車株式会社 | Composite propellant |
| FR2680783B1 (en) * | 1983-06-30 | 1994-05-06 | Poudres Explosifs Ste Nale | PROCESS FOR IMPROVING THE MECHANICAL PROPERTIES OF A DOUBLE COMPOSITE BASED PROPERGOL OBTAINED BY THE MOLDING METHOD AND PROPERGOL THUS OBTAINED. |
| GB2152920B (en) * | 1983-08-12 | 1987-06-24 | Secr Defence | Propellant composition |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3813458A (en) * | 1968-06-05 | 1974-05-28 | Hercules Inc | Random orientation of staple in slurry-cast propellants |
-
1980
- 1980-11-20 CA CA000365150A patent/CA1154260A/en not_active Expired
- 1980-11-26 NO NO803572A patent/NO803572L/en unknown
- 1980-12-18 EP EP80304590A patent/EP0031682A3/en not_active Ceased
- 1980-12-29 JP JP18942780A patent/JPS56100194A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS56100194A (en) | 1981-08-11 |
| EP0031682A3 (en) | 1981-08-26 |
| EP0031682A2 (en) | 1981-07-08 |
| NO803572L (en) | 1981-06-29 |
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