EP0333941B1 - High-energy compositions having castable thermoplastic binders - Google Patents
High-energy compositions having castable thermoplastic binders Download PDFInfo
- Publication number
- EP0333941B1 EP0333941B1 EP19880302462 EP88302462A EP0333941B1 EP 0333941 B1 EP0333941 B1 EP 0333941B1 EP 19880302462 EP19880302462 EP 19880302462 EP 88302462 A EP88302462 A EP 88302462A EP 0333941 B1 EP0333941 B1 EP 0333941B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- polybutadiene
- plasticizer
- composition
- propellant
- binder system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000203 mixture Substances 0.000 title claims description 55
- 239000011230 binding agent Substances 0.000 title claims description 34
- 229920001169 thermoplastic Polymers 0.000 title description 9
- 239000004416 thermosoftening plastic Substances 0.000 title description 9
- 229920002857 polybutadiene Polymers 0.000 claims description 25
- 239000007787 solid Substances 0.000 claims description 24
- 239000005062 Polybutadiene Substances 0.000 claims description 22
- 239000004014 plasticizer Substances 0.000 claims description 19
- 238000002156 mixing Methods 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- 238000005266 casting Methods 0.000 claims description 5
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 claims description 4
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 claims description 4
- 239000000080 wetting agent Substances 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims 2
- WNLRTRBMVRJNCN-UHFFFAOYSA-L adipate(2-) Chemical compound [O-]C(=O)CCCCC([O-])=O WNLRTRBMVRJNCN-UHFFFAOYSA-L 0.000 claims 1
- APSBXTVYXVQYAB-UHFFFAOYSA-M sodium docusate Chemical group [Na+].CCCCC(CC)COC(=O)CC(S([O-])(=O)=O)C(=O)OCC(CC)CCCC APSBXTVYXVQYAB-UHFFFAOYSA-M 0.000 claims 1
- 239000003380 propellant Substances 0.000 description 42
- 238000009472 formulation Methods 0.000 description 15
- 239000002904 solvent Substances 0.000 description 9
- GDDNTTHUKVNJRA-UHFFFAOYSA-N 3-bromo-3,3-difluoroprop-1-ene Chemical compound FC(F)(Br)C=C GDDNTTHUKVNJRA-UHFFFAOYSA-N 0.000 description 8
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- ZFMQKOWCDKKBIF-UHFFFAOYSA-N bis(3,5-difluorophenyl)phosphane Chemical compound FC1=CC(F)=CC(PC=2C=C(F)C=C(F)C=2)=C1 ZFMQKOWCDKKBIF-UHFFFAOYSA-N 0.000 description 5
- 239000002131 composite material Substances 0.000 description 5
- 229920001971 elastomer Polymers 0.000 description 5
- 239000000806 elastomer Substances 0.000 description 5
- 239000000314 lubricant Substances 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 4
- KAKZBPTYRLMSJV-UHFFFAOYSA-N butadiene group Chemical group C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 239000004615 ingredient Substances 0.000 description 4
- 239000007800 oxidant agent Substances 0.000 description 4
- 229920002725 thermoplastic elastomer Polymers 0.000 description 4
- IIZPXYDJLKNOIY-JXPKJXOSSA-N 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine Chemical compound CCCCCCCCCCCCCCCC(=O)OC[C@H](COP([O-])(=O)OCC[N+](C)(C)C)OC(=O)CCC\C=C/C\C=C/C\C=C/C\C=C/CCCCC IIZPXYDJLKNOIY-JXPKJXOSSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- 238000007792 addition Methods 0.000 description 3
- 229920001577 copolymer Polymers 0.000 description 3
- 239000000787 lecithin Substances 0.000 description 3
- 229940067606 lecithin Drugs 0.000 description 3
- 235000010445 lecithin Nutrition 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 2
- 150000001993 dienes Chemical class 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 230000009477 glass transition Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- UZGLIIJVICEWHF-UHFFFAOYSA-N octogen Chemical compound [O-][N+](=O)N1CN([N+]([O-])=O)CN([N+]([O-])=O)CN([N+]([O-])=O)C1 UZGLIIJVICEWHF-UHFFFAOYSA-N 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 238000011020 pilot scale process Methods 0.000 description 2
- 229920002589 poly(vinylethylene) polymer Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 2
- 238000011925 1,2-addition Methods 0.000 description 1
- XTFIVUDBNACUBN-UHFFFAOYSA-N 1,3,5-trinitro-1,3,5-triazinane Chemical compound [O-][N+](=O)N1CN([N+]([O-])=O)CN([N+]([O-])=O)C1 XTFIVUDBNACUBN-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- QNRMTGGDHLBXQZ-UHFFFAOYSA-N buta-1,2-diene Chemical compound CC=C=C QNRMTGGDHLBXQZ-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000002320 enamel (paints) Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 235000019589 hardness Nutrition 0.000 description 1
- 230000003100 immobilizing effect Effects 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000008247 solid mixture Substances 0.000 description 1
- 239000004449 solid propellant Substances 0.000 description 1
- 229920003051 synthetic elastomer Polymers 0.000 description 1
- 239000005061 synthetic rubber Substances 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- 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
- C06B21/005—By a process involving melting at least part of the ingredients
Definitions
- the present invention is directed to castable thermoplastic binders for high-energy compositions, particularly composite solid rocket propellants.
- U.S. Patent No. 4,361,526 proposes to use a thermoplastic elastomeric binder which is a block copolymer of a diene and styrene, the styrene blocks providing a meltable crystal structure and the diene blocks imparting rubbery or elastomeric properties to the copolymer.
- a propellant composition using the copolymer, the copolymer is dissolved in an organic solvent, such as toluene, and the solids and other propellant formulations are added. The solvent is then evaporated, leaving a rubbery solid which may be divided into pellets suitable for casting or other processing.
- a disadvantage of formulating a propellant composition using a thermoplastic elastomeric binder which must be dissolved in a solvent is that the propellant formulation cannot be cast in a conventional manner, e.g., into a rocket motor casing.
- solvent-based processing presents problems with respect to solvent removal and recovery.
- thermoplastic elastomeric binders which can be melted and cast without the need for solvent processing.
- a melt-cast high energy composition comprising energetic particulate solids dispersed in and spatially immobilized in a binder system having between 25 and 50 weight percent of 1,2 syndiotactic polybutadiene and between 50 and 75 weight percent of a plasticizer miscible with said polybutadiene.
- the polybutadiene binder system is useful for spatially immobilizing solid particulates, such as fuel material particulates and oxidizer particulates, in a high-energy formulation such as a propellant.
- the polybutadiene binder is meltable, allowing it to be mixed with other components of the propellant formulation, including the solid particulates and the plasticizer, and is castable, e.g., into a rocket motor shell. No organic solvent is required to prepare or cast the propellant formulation.
- a method of preparing a high-energy composition comprising mixing energetic particulate solids with 1,2 syndiotactic polybutadiene plus a plasticizer that is miscible with said polybutadiene at a temperature whereat said polybutadiene is molten, melt-casting said molten mixture into a mould, and allowing said molten mixture to cool to a solid high-energy composition with said solid particulates dispersed in plasticized polybutadiene.
- High molecular weight syndiotactic 1,2 polybutadiene in combination with a suitable plasticizer is found to provide a suitable elastomeric binder system for solid propellant compositions or the like.
- the polymer is a thermoplastic elastomer which generally melts in the temperature range of from 70°C to 100°C and therefore can be melted in the presence of fuel particulates and oxidizers to form a solvent-free propellant formulation melt.
- the melt is directly castable as a propellant charge into a rocket motor casing or the like.
- Polybutadienes in accordance with the present invention preferably have weight average molecular weight of between 100,000 and 200,000.
- the crystallinities typically range from 10 percent to 35 percent and preferably between 15 and 30%. Densities typically range from 0.90 to 0.91.
- 1,2 butadiene is meant that substantially all, i.e., greater than 90% of monomer addition is by 1,2 polymerization.
- syndiotactic is meant that at least 90% of the 1,2 additions result in the pendant vinyl group extending from the side opposite that of the two flanking pendant vinyl groups.
- Syndiotactic 1,2-polybutadiene polymers suitable for use as binders are sold, for example, by the Japanese Synthetic Rubber Company under the trade designations JSR RB-810, JSR RB-820 and JSR RB-830.
- Polybutadienes used in accordance with the present invention have thermal properties which make them especially suitable as propellant binders, the range from the brittle point (glass transition temperature (T g )) to the softening point generally encompassing the ordinary ambient temperature range. Viscat softening points of these compounds range from 35°C to 70°C; melting points range from 70°C to 100°C and brittle points range from -35°C to -40°C.
- T g glass transition temperature
- Viscat softening points of these compounds range from 35°C to 70°C; melting points range from 70°C to 100°C and brittle points range from -35°C to -40°C.
- the thermoplastics are elastomers at ambient temperatures, they can be processed as molten plastics at temperatures far below the temperatures where high-energy solids become unstable.
- the low processing temperatures of 1,2 syndiotactic butadienes is considered an important advantage relative to other thermoplastic elastomers which have been considered for use as propellant
- the polybutadienes have good tensile properties for binders. 300% moduli range from 40 to 80 kg/cm2; Tensile strengths range from 60 to 140 kg/cm2 and elongation ranges from 650 to 800 %. Shore D hardnesses range from 30 to 50.
- the complete binder system includes a plasticizer with which the polymer is miscible.
- Suitable plasticizers include dioctyl adipate (DOA) and dioctyl phthalate (DOP); however, other miscible plasticizers known in the art are also suitable. Mixtures of plasticizers, such as DOA/DOP mixtures are also suitable.
- Particularly suitable plasticizers are naphthenic oils, such as those sold under the trademark Tufflo by Arco, particularly Tufflo-500.
- the plasticizer comprises between 50 and 75 percent by weight of the binder system (binder plus plasticizer) and preferably between 50 and 67 percent by weight.
- the binder system may also include a minor amount of a wetting agent or lubricant, such as lecithin.
- a wetting agent or lubricant enables a higher solids loading.
- the lubricant typically comprises up to 4 weight percent of the total weight of the polybutadiene plus plasticizer.
- a presently preferred lubricant is a coating agent sold under the trade designation FC-430 by 3M.
- a complete propellant formulation includes a high percentage of energetic solid particulates, including fuel material particulates, such as aluminum, and oxidizer particulates, such as ammonium perchlorate (AP), cyclotetramethylene tetranitramine (HMX) and cyclotrimethylene trinitramine (RDX), the solid particulates typically comprising between 70 and 90 wt. percent of the propellant composition and the balance being substantially all binder system.
- the propellant may include minor amounts of additional components, such as a bonding agent and burn rate modifiers.
- the order of mixing propellant formulation ingredients is not considered to be critical. However, for ease of mixing, it is generally preferred that the binder system, including the binder, plasticizer, and any lubricant, be blended under binder melting conditions prior to adding the solids. After the binder system is melted and blended, the solids are added, and mixing is continued to provide a uniform dispersion of solids in binder system. To provide a uniform cast, it is preferred to deaerate the molten formulation and then to cast the melt.
- Cast propellant may be remelted after solidifying. Thus, there is no need to cast the propellant immediately after mixing, although from an energy efficiency standpoint this is generally desirable.
- thermoplastic of the propellant composition provides for its eventual recycle, as opposed to the burning required for disposal of thermoset propellant compositions. Because the thermoplastic propellant does not have a "pot life", there are no limitations to the time of casting, and if any problems develop during casting, the process can be delayed as long as necessary merely by maintaining the propellant formulation in molten form.
- propellants in accordance with the present invention no solvents or other highly volatile substances are required. Accordingly, no special measures or special apparatus are required to contain solvent vapors, to remove solvent from the formulation or to recover solvent for reuse.
- Propellant formulations in accordance with the present invention may be prepared by conventional mixing apparatus without requiring extrusion, although extrusion may be used to prepare certain forms of propellants, such as propellant pellets.
- syndiotactic butadienes for use in propellant binders is their low melting temperatures, and propellant formulations using syndiotactic butadienes are processable in the range of to 120°C. Low processing temperatures help to ensure safety in processing high-energy compounds. Syndiotactic butadienes also have excellent low-temperature properties, typically having glass transition temperatures in the range of -40°F (-40°C). Low-temperature properties are important for propellant systems which might be used at very low temperatures or even exposed to very low temperatures prior to use.
- a pilot scale mix of a composite propellant with a thermoplastic elastomeric binder is described in this example.
- 240 grams of a composite propellant were made from the following ingredients: Ingredient Weight Percent Syndiotactic Polybutadiene RB-810 8.3 Dioctyl Adipate 15.9 Lecithin 0.8 Unground Ammonium Perchlorate (AP) 200 ⁇ 50.0 Ground Ammonium Perchlorate (AP) 18 ⁇ 25.0 The ingredients were mixed in a Baker Perkins twin blade vertical mixer with a working capacity of approximately 0.5 liters.
- the propellant was removed from it and cut into 6.35 mm ( 1 4 ⁇ ) diameter by 10.2 cm (4 ⁇ ) long cylindrical stands for testing of burn rate.
- Four strands were prepared and inhibited on all but one circular face with black enamel paint. These strands were then burned in a pressurized bomb to determine propellant burn rate. Two strands were burned at an average pressure of 6.998 MPa (1015 psig) and had an average burn rate of 6.27 mm/sec (0.247 in/sec). The other two were burned at a pressure of 3.516 MPa (510 psig) and had an average burn rate of 4.65 mm/sec (0.183 in/sec).
- novel binder system has been described primarily in terms of its use in propellants, the binder system is applicable to other solid, high-energy compositions, such as explosives and gasifiers.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Dispersion Chemistry (AREA)
- Molecular Biology (AREA)
- Crystallography & Structural Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
Description
- The present invention is directed to castable thermoplastic binders for high-energy compositions, particularly composite solid rocket propellants.
- Conventional solid composite propellants utilize chemically cross-linked elastomers in which prepolymers are cross-linked by chemical curing agents. As outlined in detail in U.S. Patent No. 4,361,526, there are important disadvantages to cross-linked elastomers. Cross-linked elastomers must be cast within a short period of time after addition of the curative, which time period is known as the "pot life". Disposal of a cast cross-linked propellant composition is difficult except by burning which poses environmental problems.
- As an alternative to cross-linked binders, U.S. Patent No. 4,361,526 proposes to use a thermoplastic elastomeric binder which is a block copolymer of a diene and styrene, the styrene blocks providing a meltable crystal structure and the diene blocks imparting rubbery or elastomeric properties to the copolymer. In order to prepare a propellant composition using the copolymer, the copolymer is dissolved in an organic solvent, such as toluene, and the solids and other propellant formulations are added. The solvent is then evaporated, leaving a rubbery solid which may be divided into pellets suitable for casting or other processing.
- A disadvantage of formulating a propellant composition using a thermoplastic elastomeric binder which must be dissolved in a solvent is that the propellant formulation cannot be cast in a conventional manner, e.g., into a rocket motor casing. Furthermore, solvent-based processing presents problems with respect to solvent removal and recovery. Organic solvents, such as toluene, present certain hazards both to the immediate work area and to the larger environment, necessitating various precautions to be taken with respect to processing such propellant formulations.
- It would be desirable to have propellants and other high-energy solid compositions which include thermoplastic elastomeric binders which can be melted and cast without the need for solvent processing.
- In accordance with a first aspect of the invention, there is provided a melt-cast high energy composition comprising energetic particulate solids dispersed in and spatially immobilized in a binder system having between 25 and 50 weight percent of 1,2 syndiotactic polybutadiene and between 50 and 75 weight percent of a plasticizer miscible with said polybutadiene. The polybutadiene binder system is useful for spatially immobilizing solid particulates, such as fuel material particulates and oxidizer particulates, in a high-energy formulation such as a propellant. The polybutadiene binder is meltable, allowing it to be mixed with other components of the propellant formulation, including the solid particulates and the plasticizer, and is castable, e.g., into a rocket motor shell. No organic solvent is required to prepare or cast the propellant formulation.
- Thus, according to a further aspect of the invention there is provided a method of preparing a high-energy composition comprising mixing energetic particulate solids with 1,2 syndiotactic polybutadiene plus a plasticizer that is miscible with said polybutadiene at a temperature whereat said polybutadiene is molten, melt-casting said molten mixture into a mould, and allowing said molten mixture to cool to a solid high-energy composition with said solid particulates dispersed in plasticized polybutadiene.
- High molecular weight syndiotactic 1,2 polybutadiene in combination with a suitable plasticizer, is found to provide a suitable elastomeric binder system for solid propellant compositions or the like. The polymer is a thermoplastic elastomer which generally melts in the temperature range of from 70°C to 100°C and therefore can be melted in the presence of fuel particulates and oxidizers to form a solvent-free propellant formulation melt. The melt is directly castable as a propellant charge into a rocket motor casing or the like.
- Polybutadienes in accordance with the present invention preferably have weight average molecular weight of between 100,000 and 200,000. The crystallinities typically range from 10 percent to 35 percent and preferably between 15 and 30%. Densities typically range from 0.90 to 0.91. By 1,2 butadiene is meant that substantially all, i.e., greater than 90% of monomer addition is by 1,2 polymerization. By syndiotactic is meant that at least 90% of the 1,2 additions result in the pendant vinyl group extending from the side opposite that of the two flanking pendant vinyl groups. Syndiotactic 1,2-polybutadiene polymers suitable for use as binders are sold, for example, by the Japanese Synthetic Rubber Company under the trade designations JSR RB-810, JSR RB-820 and JSR RB-830.
- Polybutadienes used in accordance with the present invention have thermal properties which make them especially suitable as propellant binders, the range from the brittle point (glass transition temperature (Tg)) to the softening point generally encompassing the ordinary ambient temperature range. Viscat softening points of these compounds range from 35°C to 70°C; melting points range from 70°C to 100°C and brittle points range from -35°C to -40°C. Thus while the thermoplastics are elastomers at ambient temperatures, they can be processed as molten plastics at temperatures far below the temperatures where high-energy solids become unstable. The low processing temperatures of 1,2 syndiotactic butadienes is considered an important advantage relative to other thermoplastic elastomers which have been considered for use as propellant binders.
- The polybutadienes have good tensile properties for binders. 300% moduli range from 40 to 80 kg/cm²; Tensile strengths range from 60 to 140 kg/cm² and elongation ranges from 650 to 800 %. Shore D hardnesses range from 30 to 50.
- To provide the polymer with suitable elastomeric properties to serve as a binder, the complete binder system includes a plasticizer with which the polymer is miscible. Suitable plasticizers include dioctyl adipate (DOA) and dioctyl phthalate (DOP); however, other miscible plasticizers known in the art are also suitable. Mixtures of plasticizers, such as DOA/DOP mixtures are also suitable. Particularly suitable plasticizers are naphthenic oils, such as those sold under the trademark Tufflo by Arco, particularly Tufflo-500. The plasticizer comprises between 50 and 75 percent by weight of the binder system (binder plus plasticizer) and preferably between 50 and 67 percent by weight.
- The binder system may also include a minor amount of a wetting agent or lubricant, such as lecithin. The wetting agent or lubricant enables a higher solids loading. The lubricant typically comprises up to 4 weight percent of the total weight of the polybutadiene plus plasticizer. A presently preferred lubricant is a coating agent sold under the trade designation FC-430 by 3M.
- A complete propellant formulation includes a high percentage of energetic solid particulates, including fuel material particulates, such as aluminum, and oxidizer particulates, such as ammonium perchlorate (AP), cyclotetramethylene tetranitramine (HMX) and cyclotrimethylene trinitramine (RDX), the solid particulates typically comprising between 70 and 90 wt. percent of the propellant composition and the balance being substantially all binder system. In addition, the propellant may include minor amounts of additional components, such as a bonding agent and burn rate modifiers.
- Because the thermoplastic elastomer does not have a "pot life" in the sense of cross-linked elastomers, the order of mixing propellant formulation ingredients is not considered to be critical. However, for ease of mixing, it is generally preferred that the binder system, including the binder, plasticizer, and any lubricant, be blended under binder melting conditions prior to adding the solids. After the binder system is melted and blended, the solids are added, and mixing is continued to provide a uniform dispersion of solids in binder system. To provide a uniform cast, it is preferred to deaerate the molten formulation and then to cast the melt.
- Cast propellant may be remelted after solidifying. Thus, there is no need to cast the propellant immediately after mixing, although from an energy efficiency standpoint this is generally desirable.
- An important advantage of having a propellant which is meltable is that the propellant from an outdated missile can be melted down and reused. At the time of such remelting, the propellant might be reformulated, e.g., by addition of additional fuel or oxidizer particulates. Accordingly, the thermoplastic of the propellant composition provides for its eventual recycle, as opposed to the burning required for disposal of thermoset propellant compositions. Because the thermoplastic propellant does not have a "pot life", there are no limitations to the time of casting, and if any problems develop during casting, the process can be delayed as long as necessary merely by maintaining the propellant formulation in molten form.
- In preparing propellants in accordance with the present invention, no solvents or other highly volatile substances are required. Accordingly, no special measures or special apparatus are required to contain solvent vapors, to remove solvent from the formulation or to recover solvent for reuse. Propellant formulations in accordance with the present invention may be prepared by conventional mixing apparatus without requiring extrusion, although extrusion may be used to prepare certain forms of propellants, such as propellant pellets.
- An important advantage of syndiotactic butadienes for use in propellant binders is their low melting temperatures, and propellant formulations using syndiotactic butadienes are processable in the range of to 120°C. Low processing temperatures help to ensure safety in processing high-energy compounds. Syndiotactic butadienes also have excellent low-temperature properties, typically having glass transition temperatures in the range of -40°F (-40°C). Low-temperature properties are important for propellant systems which might be used at very low temperatures or even exposed to very low temperatures prior to use.
- The invention will now be described in greater detail by way of specific examples.
- A pilot scale mix of a composite propellant with a thermoplastic elastomeric binder is described in this example. 240 grams of a composite propellant were made from the following ingredients:
Ingredient Weight Percent Syndiotactic Polybutadiene RB-810 8.3 Dioctyl Adipate 15.9 Lecithin 0.8 Unground Ammonium Perchlorate (AP) 200µ 50.0 Ground Ammonium Perchlorate (AP) 18µ 25.0
The ingredients were mixed in a Baker Perkins twin blade vertical mixer with a working capacity of approximately 0.5 liters. First the polybutadiene, dioctyl adipate, and lecithin were added to the mix bowl and mixed for a total of 70 minutes with stops after 10, 20, 40 and 60 minutes for scrape down of the mixer blades. A water/ethylene glycol mixture at 99°C (210°F) was circulated through the mixer jacket in order to heat the mixture. After 70 minutes of mix time, the mix temperature had climbed to 71°C (160°F) and the polybutadiene was partially melted. At this point, one half of the unground AP was added to the mix bowl and mixed for 20 minutes. After 130 minutes total of mix time, the mixing was complete and the batch was uniform in appearance. The mix temperature was 80.6°C (177°F) and its viscosity was 8 Kp. The mix was then deaerated and cast into a rectangular mold by letting it drop through a funnel and slit plate into a vacuum bell. - After the mold had cooled, the propellant was removed from it and cut into 6.35 mm (
- Nine more pilot scale batches of composite propellants using the thermoplastic elastomer binder were made and cast substantially the same manner as described in Example 1. The level of AP oxidizer was varied from 75% to 85% of the total mixture by weight. Both RB-810 and RB-820 grades of JSR syndiotactic polybutadiene were used and plasticizer to polymer ratio was varied between 2 to 1 and 1 to 1. The table below indicates the batch numbers, formulation and processing results for these batches. JANNAF Class C uniaxial tensiles were prepared from the finished batches and tested at a constant strain rate of 5.08 cm/min (2.0 in/min) at a temperature of 25°C (77°F). Maximum stress, strain at maximum stress and elastic modulus were calculated from these tests and are presented in the table.
- Although the novel binder system according to the present invention has been described primarily in terms of its use in propellants, the binder system is applicable to other solid, high-energy compositions, such as explosives and gasifiers.
Claims (10)
- A melt-cast high energy composition comprising energetic particulate solids dispersed in and spatially immobilized in a binder system having between 25 and 50 weight percent of 1,2 syndiotactic polybutadiene and between 50 and 75 weight percent of a plasticizer miscible with said polybutadiene.
- A composition in accordance with Claim 1 comprising between 70 and 90% energetic particulate solids, balance said binder system.
- A composition in accordance with Claim 1 or Claim 2 wherein said 1,2 syndiotactic polybutadiene has a weight average molecular weight of between 100,000 and 200,000.
- A composition in accordance with any preceding claim wherein said plasticizer is selected from dioctyl, adipate, dioctyl phthalate and mixtures thereof.
- A composition according to any preceding claim wherein said binder system includes up to 4 wt. percent of a wetting agent based upon the total weight of plasticizer and polybutadiene in said binder system.
- A method of preparing a high-energy composition comprising mixing energetic particulate solids with 1,2 syndiotactic polybutadiene plus a plasticizer that is miscible with said polybutadiene at a temperature whereat said polybutadiene is molten, melt-casting said molten mixture into a mould, and allowing said molten mixture to cool to a solid high-energy composition with said solid particulates dispersed in plasticized polybutadiene.
- A method according to Claim 6 wherein said molten mixture is deaerated before cooling.
- A method according to Claim 7 wherein said molten mixture is cast after deaeration and prior to cooling.
- A method according to any one of Claims 6 to 8 wherein said temperature is at least 90°C.
- A method according to any one of Claims 6 to 9 wherein said polybutadiene and said plasticizer are blended at said temperature and then said energetic solids are added.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19880302462 EP0333941B1 (en) | 1988-03-21 | 1988-03-21 | High-energy compositions having castable thermoplastic binders |
DE8888302462T DE3872380D1 (en) | 1988-03-21 | 1988-03-21 | HIGH-ENERGY COMPOSITIONS WITH A POWLABLE THERMOPLASTIC BINDER. |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19880302462 EP0333941B1 (en) | 1988-03-21 | 1988-03-21 | High-energy compositions having castable thermoplastic binders |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0333941A1 EP0333941A1 (en) | 1989-09-27 |
EP0333941B1 true EP0333941B1 (en) | 1992-06-24 |
Family
ID=8199995
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19880302462 Expired EP0333941B1 (en) | 1988-03-21 | 1988-03-21 | High-energy compositions having castable thermoplastic binders |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0333941B1 (en) |
DE (1) | DE3872380D1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2714374B1 (en) * | 1993-12-29 | 1996-01-26 | Poudres & Explosifs Ste Nale | Solid pyrotechnic compositions with thermoplastic binder and silylferrocene polybutadiene plasticizer. |
WO2000007962A2 (en) * | 1998-07-10 | 2000-02-17 | Cordant Technologies, Inc. | Improved composite solid propellants including a hydroxy-functional polybutadiene binder and a rocket motor including same |
DE102010044344A1 (en) * | 2010-09-03 | 2012-03-08 | Rheinmetall Waffe Munition Gmbh | Plastic-bound explosive formulation |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2995431A (en) * | 1958-06-20 | 1961-08-08 | Phillips Petroleum Co | Composite ammonium nitrate propellants containing boron |
US4042619A (en) * | 1965-05-03 | 1977-08-16 | E. I. Du Pont De Nemours And Company | Derivatives of carboxy-terminated polybutadienes |
US3986910A (en) * | 1974-04-12 | 1976-10-19 | The United States Of America As Represented By The Secretary Of The Navy | Composite propellants containing critical pressure increasing additives |
DE2529432C2 (en) * | 1975-07-02 | 1985-10-17 | Dynamit Nobel Ag, 5210 Troisdorf | Process for the production of flexible molded explosives |
US4384066A (en) * | 1980-11-24 | 1983-05-17 | Uniroyal, Inc. | Ionic elastomer blends with syndiotactic polybutadiene |
-
1988
- 1988-03-21 DE DE8888302462T patent/DE3872380D1/en not_active Expired - Lifetime
- 1988-03-21 EP EP19880302462 patent/EP0333941B1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
DE3872380D1 (en) | 1992-07-30 |
EP0333941A1 (en) | 1989-09-27 |
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