CN1273572A - Flares having ignition means formed from extrudable igniter compositions - Google Patents

Abstract

The present invention relates to flares and other solid propellant devices, rockets, etc. equipped with an ignition device or ignition system based in part on an extruded ignition rod as a whole. The extruded ignition bar is made with components including a water-soluble or water-swellable binder, at least one oxidizing agent, at least one fuel, and optionally fibers.

Description

Flares having ignition means formed from extrudable igniter compositions

The present invention relates to extrudable igniter compositions and extruded ignition rods derived therefrom for combination with flares or other solid propellant devices such as rockets.

The igniter composition should meet a number of design criteria. The igniter composition should be strong enough when made to remain in operable form until the device to be ignited, such as a flare or other device, is developed.

A commonly proposed ignition system uses solid particles consisting of B/ _KNO3 which, when ignited, initiate the combustion of a composition producing a specific gas.

In the civilian market, other recent efforts have focused on the development of other igniter compositions which are less expensive or which are easier to manufacture. These works include suggestions for the use of hot-melt thermoplastic resin matrices in combination with specific igniter compositions such as _KNO3 . This work attempts to combine commercially available hot-melt adhesives, such as those designed for so-called "glue sprayers", with the usual alkali metal oxidizing agents. Such efforts to improve performance have not been satisfactory. Extrusion and ignition properties proved difficult to control and did not exhibit the required repeatable ballistic properties.

Thus, despite these and other efforts, related objectives have not been achieved. There remains a desire for a simpler, less costly igniter composition for use in flares and decoys or other devices. In particular, efforts are still being made to provide an easily manufactured and sufficiently strong igniter composition which does not require so-called hot melt adhesives and thus avoids the hazards associated with processing pyrotechnic materials at high temperatures.

It would therefore be a great advance to provide an igniter composition which can be used as an ignition device which satisfactorily solves these problems in the industry.

The present invention provides flares, solid propellant rockets, decoy devices, etc., provided with one or more of the ignition rods disclosed herein.

Extrudable ignition devices are easy to manufacture at low cost, resulting in a physically robust product. The ignition device can be fabricated without the use of thermoplastic melt or hot-melt mixing equipment, thus avoiding the potential hazards associated with processing at elevated temperatures. Extrudable igniter compositions that can be made into ignition rods are suitably processed at room temperature to have substantially relatively selectable igniter characteristics. The ignition rod may have other configurations, provided that such configuration is consistent with the purpose disclosed in this specification. The extrudable igniter composition may be used to form a solid or hollow ignition "rod" capable of igniting the flare composition or propellant composition in a flare or other pyrotechnic device.

Figure 1 illustrates an exemplary longitudinal section flare (flare type XM212) including a igniter rod made from an extrudable igniter composition.

Figures 2, 3, 4 and 5 are radial cross-sectional views of flares with ignition rods made from the disclosed extrudable igniter compositions.

The extruded ignition rod is characterized as having a configuration designed for a fast deflagration process at high ignition temperatures. When ignited, the ignition rod is capable of igniting another pyrotechnic composition. In a flare, such as the XM212 flare, the ignition rod is sized to continuously complete ignition, eg, complete flame transition, within a short period of time, eg, less than 10 milliseconds.

The igniter composition capable of being extruded can be characterized as being available in combination with a binder, a water soluble or dispersible oxidizer, a water soluble or dispersible fuel and a selected amount of water. Preferably, the extrudable composition is substantially homogeneous in composition.

The binder is preferably a water-soluble binder, although water-swellable binder materials are not excluded, provided that the remaining solid components of the ignition device are at least substantially sufficiently uniformly distributed therein. Representative binders used in the igniter composition include, for example, water-soluble binders like poly-N-vinylpyrrolidone, polyvinyl alcohol and their copolymers, polyacrylamide, sodium polyacrylate, propylene Amide or sodium acrylate based copolymers, gums and gelatins. These water-soluble binders include, of course, known gums such as guar gum, acacia, modified celluloses and starches. Gums are discussed in detail in C.L. Mantell, The Water-Soluble Gums (Reinhold Publishing Corp., 1947), which is incorporated herein by reference. Water soluble binders are now believed to improve mechanical properties or provide enhanced crush strength. Although water-immiscible binders may be used in the present invention, it is generally preferred to use water-soluble binders that are compatible with the fuel and/or oxidizer suitable for use in formulating the igniter. Suitable fuels and oxidizers may be water soluble or water insoluble. Suitable fuels and oxidants can be inorganic or organic.

In the formulation for the manufacture of extruded ignition rods, the binder concentration leads to an extrudate with sufficient mechanical strength. Extrudates such as ignition rods should be able to retain their shape, eg maintain their integrity, until they are ignited. The extruded ignition rod is preferably capable of being contained (inserted) in the pyrotechnic composition, for example in a suitably configured hole (eg central hole) in the propellant composition, and also capable of crushing or breaking up when fired. Typically, the binder may be present, for example, at about 2-10% by weight, more preferably at about 3-7% by weight, based on the dry ingredients of the formulation. The adhesive may consist of more than one adhesive material.

The igniter composition includes at least one oxidizing agent, which is preferably water-soluble or at least water-dispersible. Thus, the oxidizing agent may be organic or inorganic, although inorganic oxidizing agents are presently preferred. Organic oxidants are dispersible in the binder, so that a sufficiently uniform igniter composition can be obtained. Organic oxidants include ammonium nitrate salts, nitro compounds, nitramines, nitrate esters, and ammonium perchlorate, wherein methyl ammonium nitrate , methylamine perchlorate is illustrative. Other alternative substances include RDX and HMX, CL-20 and PETN. Inorganic oxidizing agents include oxidizing ions such as nitrate, nitrite, chlorate, perchlorate, peroxide and superoxide. Representative of these inorganic oxidizing agents are metal nitrates such as potassium nitrate or strontium nitrate, ammonium nitrate, metal perchlorates such as potassium perchlorate, and metal peroxides such as strontium peroxide. Generally, the amount of oxidant is usually effective to ensure oxidation of at least one fuel in the igniter, for example, it may be about 40-90% by weight, more preferably about 70-85% by weight, based on the dry components of the formulation. %(weight).

If the binder in the igniter composition is capable of functioning as the second fuel instead of the first, the igniter composition can be formulated with an additional fuel. These additional fuels include powdered metals such as powdered aluminium, zirconium, magnesium and/or titanium; metal hydrides such as zirconium hydride or titanium hydride; so-called metalloids such as silicon and boron which are well dispersed in the binder. Water-soluble or water-dispersible fuels include, for example, guanidine nitrate, cyano compounds, nitramines (RDX and/or HMX), CL-20, tetranitrocarbazoles, organic nitro compounds, and, if desired, in particle size distribution Aspects can be "multimodal". The water-dispersible material can be added with a substantially average particle size distribution or a multimodal distribution, depending on the desired ignition characteristics.

Preference is given to using finely particulate water-dispersible fuels such as powdered or ground to sufficiently fine particles to ensure adequate distribution during production. At least substantially uniform distribution in the resulting extrusion igniter composition is preferred. Typically, the fuel is in the form of a powder, for example 100 microns or less such as about 1-30 microns. If desired, the particle size range of the powdered metal can be smaller, such as about 1-20 microns, or even smaller, such as 1-about 5 microns. The amount of fuel (other than binder) may be, for example, about 5-30% by weight, more preferably about 10-20% by weight, based on the dry ingredients of the formulation.

Reinforcements can be added to the ignition rod if desired. Appropriate reinforcement can be achieved using fibers such as combustible fibers that strengthen the extruded ignition rod and also improve ignition performance when the reinforcement is properly selected. The ignition rod and its associated solid propellant may contain reinforcements, if desired. Appropriate reinforcement can be achieved using fibers such as combustible fibers that strengthen the extruded ignition rod and also improve ignition performance when the reinforcement is properly selected. The length of the fibers is preferably generally short (low aspect ratio). Examples of fibers added to extrudable ignition formulations include polyolefin fibers, polyamide fibers, polyester fibers, and poly(2,2'-(m-phenylene)-5,5-bisbenzimidazole ("PBI" ) fibers. Polyolefin fibers include polyethylene ("PE") fibers, such as about 0.005 mm or greater in outer diameter, such as about 0.8 mm, and PE fibers from 0.1 to about 3.2 mm in length, an example of which is Spectra manufactured by Allied-Signal 900 brand polyethylene fibers. Suitable polyamide fibers, such as nylon 6 fibers, can have a suitably selected diameter, such as 19 microns, and a length of 1.5 mm to about 6.4 mm. Suitable polyester fibers include high tenacity polyester fibers, Its length is about 1.5-6.4 mm, and a suitable diameter is about 25 microns. PBI fibers include fibers with a length of about 0.8-3.2 mm. Representative enhanced ignition rods and their formulations are listed in the examples.

The composition in extrudable form can be readily obtained, for example, by mixing the binder, fuel, oxidizer, and a selected amount of water for a period of time such that the fuel (if used) and oxidant are at least substantially uniformly distributed throughout the binder. One method involves mixing a water soluble binder with a selected amount of water to obtain a premix, and then combining the premix with (a) a fuel followed by an oxidizer, or (b) an oxidizer followed by a fuel, or (c ) The oxidant and fuel are combined and mixed. The amount of water is generally such that the resulting product has an extrudable, but preferably non-runny consistency. In principle, larger quantities of water can be used, but some production problems may arise, including an increase in waste water containing varying amounts of pyrotechnic substances (fuel, oxidizer, etc.).

The igniter composition so produced can be extruded to obtain the desired physical geometry.

Ignition rods can be used in conjunction with solid propellant rockets or other devices that require solid propellant to ignite. Other devices include, but are not limited to, flares. Of suitable flares, propelled flares are well known to those skilled in the art, of which the MJU-10 flare is exemplified. Other flares, such as the M-206 flare (which may or may not be spectrally matched), or near-infrared flares, such as the M-278 flare, are also suitable for use in combination with one or more ignition rods. Suitable flares are not limited to the aforementioned MJU-10, M-206 or M-278 flares. For example, so-called standard 2.75 inch (cross-sectional diameter) flares, including visible light flares, are suitable for use with at least one ignition rod. Non-commercial flare variants of standard flares, such as the M-257 flare, are also suitable for configuration with one or more ignition rods. Advantageously, the ignition rod reduces cost, reduces production time, and simplifies the design of flares, including push-type flare ignition systems such as the MJU-10 flare. Igniters may be used in a number of decoy targeting devices, including decoy flares configured to defend against intrusion threats, particularly heat homing missiles. One or more ignition rods can improve the reliability of flare ignition by reducing the number of inappropriate primers, and can also improve the safety of flare production by avoiding the use of flammable solvents commonly used when applying traditional primers. Suitable flares and/or flare compositions for use with at least one ignition rod are described in Encyclopedia of Chemical Technology 20:680-697 (Fourth Edition, 1996), including those listed herein References, the entire contents of which are incorporated into this specification by reference.

Ignition rods can be used with larger sized solid propellant launch vehicles, such as solid propellant rockets. In these larger and more complex systems, the ignition rod can be used as part of the ignition system, for example in a pyrotechnic transmission system as a conduction starter or to initiate ignition conduction. Solid propellant rockets that can be configured with at least one ignition rod as at least part of the ignition system are covered in "Solid Rocket Propulsion Technology" (Pergamon Press, 1st edition, 1993) and "Rocket Propulsion Elements" (Rocket Propulsion Elements) (Wiley Interscience, Fourth Edition, 1976), the entire disclosure of which is incorporated herein by reference. The well known Jane's Handbook describes flares and other solid propulsion devices suitable for use with ignition rods.

Extrusions and extrudates are generally described in "Encyclopedia of Polymer Science and Engineering" (Encyclopedia of Polymer Science and Engineering) 16, 570-631 (Second Edition, 1996), including references listed therein, which The entire content of the text is listed in this specification as a reference.

Figure 1 illustrates a known flare designated as XM212 flare in cross-sectional view. Viewed in longitudinal section, the outer casing is a suitable pressure vessel made of steel or other material capable of being used in flare applications. The cartridge 18 may have a vented shroud 17 . A closed end is defined by the front cover 19 . The opposite end of the XM212 flare includes a rear cover 12, a spacer plate 13, an ignition system 15 with an ignition device, a protective cover 10 and a piston 11. In a preferred embodiment, as shown in FIG. 1, the solidified (extruded) ignition rod 16, which can be solid or hollow, extends longitudinally (in whole or in part) through the propellant grain. Igniter rods can be fabricated by extruding the extrudable igniter composition described above, allowing the extrudate to solidify, and inserting it into propellant grains, preferably before it solidifies. The selected propellant composition 14 surrounds the ignition rod. If desired, so-called fast deflagration cords, such as deflagration cords with loose sleeves, can be installed longitudinally inside the hollow ignition rod. Although not illustrated, more than one ignition rod may be used if desired.

Figures 2-5 show a cross-sectional "diameter" view of a flare case with propellant and ignition rod. In the diametrical cross-sectional view of FIG. 2, the flare casing 28 may have, if desired, a layer of sprayed foam material 22 (such as a foam nitrocellulose liner) on its inner surface prior to loading of the propellant 24. A central hole 26 of pre-selected geometry encases a hollow ignition rod 20 (eg, quargum cement/B/KNO ₃ , in end view).

In the diametrical cross-sectional view of FIG. 3 , the flare casing 38 has been charged with propellant 34 and is provided with a centrally located hollow ignition rod 36 . Depending on the specific circumstances, additional solid or hollow ignition rods 32 can be configured.

In the diametrical cross-sectional view of FIG. 4, the flare casing 48 has been filled with propellant 44, and a centrally located shaped hole having a preselected geometry. The centrally located hole may have an ignition rod 42 and several ignition rods 46 (in the form of bands) disposed radially in slots away from the hole. These ignition rods are mounted in slots, preferably non-loosely mounted.

In the diametrical cross-sectional view of FIG. 5, the flare casing 58 has been charged with propellant 54 and has a plurality of axial holes in the centrally located firing rod.

If desired, the igniter rod may be fitted with a strippable jacket/sleeve before being inserted into the propellant grain. This protects the ignition rod during production or during storage prior to use.

The ignition rod is preferably inserted into the propellant grain before it solidifies.

Igniter compositions are disclosed in co-pending US Full Application No. _____, filed July 21, 1998, the entire disclosure of which is incorporated herein by reference.

The invention is further described by the following non-limiting examples.

Example 1

A one gallon Baker-Perkins star mixer was charged with 1170 grams (78%) of 35 micron potassium nitrate and 105 grams (7%) of Cytec Cynamer(R ⁾ N-300 brand polyacrylamide (15,000,000 MW). The components were then briefly mixed in the dry state for 1 minute. To this mixture was added 217.5 grams (14.5 parts per hundred parts of igniter formula) of water and mixed for an additional 5 minutes. The mixing paddle and the inside of the mixing tank were scraped with a Velostat (conductive plastic) spatula, followed by an additional 15 minutes of mixing. To the resulting white thick paste was added 225 grams (15%) of amorphous boron powder (90-92% purity) and mixed briefly for 5 minutes. After donning the approved protective clothing, the paddle and groove were again "scratched" by hand and the formula was mixed for an additional 10 minutes. The resulting brown dough-like material was pelletized into -4 mesh and fed to a Haake 25 mm single screw extruder. The ignition formulation was extruded through a 12 point star die with a maximum diameter of 0.33" and a minimum diameter of 0.30". The die consisted of a female ejector pin with a center diameter of 0.08", thus resulting in a hollow rod configuration. The extruded ignition formulation was cut into 7" lengths. Before drying, the diameter is 0.07″ and the length is 7.5″. A Teledyne RDC (Rapid Deflagration Cord) was inserted into a 0.08" diameter hole. The ignition rod was dried overnight at 165°F. The ignition rod was tested to evaluate the performance of the ignition rod in an inflator that is an automatic Safety bag design. The working condition of the ignition rod is satisfactory.

Example 2

A set of extruded ignition rod formulations were prepared containing boron, potassium nitrate, water soluble binder, and optionally reinforcing fibers. These formulations are listed in Table 1. The formulations were mixed first in 10 gram quantities and then in 30 gram quantities to determine their sensitivity to stimuli including impact, friction, electrostatic discharge and heat (Table II). In general, hydrocarbon-based adhesives have the greatest sensitivity to ABL friction. Recipes containing methyl cellulose, guar gum, locust bean gum as binders can also be used to make ignition sticks.

The remainder of the formula was mixed in 325 gram quantities in a pint Baker-Perkins star mixer. Potassium nitrate and corresponding water-soluble binder were slightly dry mixed for 1 minute. To this blend, the corresponding amount of water (Table III) was added and the slurry was allowed to mix for an additional 5 minutes. As in Example 1, "scratch" the grooves and paddles. At this point, the fiber was added to the fiber-containing formula and the dough was mixed for an additional 5 minutes. All formulations were mixed for an additional 10 minutes before adding boron. At this point half of the boron is added and mixing is continued for an additional 5 minutes. The remainder of the boron was then added followed by an additional 5 minutes of mixing. After the final "scratch out", the formulation was mixed for an additional 10 minutes. The resulting tan doughy material was pelletized to -4 mesh and fed to a Haake 25mm single screw extruder. The ignition rod formulation was extruded through a 12 point star die with a maximum diameter of 0.33" and a minimum diameter of 0.305". The die consisted of a centrally located die ejector pin with a diameter of 0.08". The extruded ignition formulation was cut into 7" lengths. Before drying, the diameter is 0.07″ and the length is 7.5″. Insert Teledyne RDC (Rapid Deflagration Cord). Extrude 10 more 2" lengths. Pilot sticks were dried overnight at 165°F.

Important factors in determining a useful formulation include the quality of the propellant grain after drying, its actual performance as an ignition agent, and the rate of drying. Some formulations may see the mixture of KNO ₃ and binder bleed out of the grain surface when drying. Penetration into the pores is not desired. Leaching was lowest in formulations containing tragacanth, ^Cyanamer® A-370 and ^Cyanamer® P-21 (Table III). The results of the evaluation of ignition rods made from formulations containing ^Cyanamer® A-370 and ^Cyanamer® P-21 met the requirements for inflator devices. The corresponding drying rates were calculated to be 10:1.7:1 for formulations containing ^Cyanamer® N-300, ^Cyanamer® P-21 and ^Cyanamer® A-370, respectively. Thus, it was shown that formulations containing Cyanamer ^(R) A-370 dried faster with minimal _KNO3 leaching, resulting in propellant grains capable of igniting gaseous products with minimal ignition delay.

It is important to develop extruded ignition rods for flares and other solid propulsion devices that can withstand decades of shaking and vibration during service before deployment. Therefore, a durability test method for extruded ignition rods has been developed. Durability tests were performed in 3-point bending using a load applied in the middle of the span. Bending is chosen because tension, compression, and shear stresses all exist. In addition, the sample structure is suitable for this type of loading. Using a 1.5" span, apply the load using 1/8 to 1/4" diameter concealed nails. Apply a nominal preload of 0.7 lbs. The samples were then subjected to 1000 load cycles under the following conditions: cycle amplitude 0.003 inch, frequency 10 Hz. After cyclic loading, test the sample to break at a travel rate of 0.2 inches per minute. The durability of each sample is reported as the area under the load-movement curve. For simplicity, the units are in corrected units (lb-force for load, mil for displacement). Therefore, the reported durability units are mil-pounds. All tests were performed at ambient laboratory temperature (75° ± 5°F). Durability test results show that extrusion ignition formulations containing fibers, such as formulations #13 and #15 in Table III, have high durability.

Table I

Examples of ignition formulations designed for extrusion with water formula# % _KNO3 %boron Adhesive % binder fiber %fiber 1 78.00 15.00 ^Cyanamer® N-300 ¹ 7.00 none 0.00 2 77.50 15.50 Methylcellulose 7.00 none 0.00 3 76.30 16.70 ^Cyanamer® A-370 7.00 none 0.00 4 77.80 15.20 ^Cyanamer® P-21 7.00 none 0.00 5 78.00 15.00 ^Cyanamer® N-300LMW 7.00 none 0.00 6 76.50 16.50 Tragacanth Gum 7.00 none 0.00 7 76.50 16.50 Locust Bean Gum 7.00 none 0.00 8 76.50 16.50 Karaya gum 7.00 none 0.00 9 78.00 15.00 PAM 10000MW 7.00 none 0.00 10 76.50 16.50 Guar Gum, FG-1, HV 7.00 none 0.00 11 77.00 16.00 gelatin, leather 7.00 none 0.00 12 78.50 12.50 ^Cyanamer® N-300 7 C fiber 2.00 13 78.50 12.50 ^Cyanamer® N-300 7.00 C fiber 2.00 14 78.50 12.50 ^Cyanamer® N-300 7.00 SiC 2.00 15 75.70 14.50 ^Cyanamer® N-300 6.80 saffil® ^type 2.00 ¹ Cyanamer is a registered trademark of Cytec Industries Inc. Polyacrylamide Specific Polymer, Sodium Polyacrylate or Copolymers thereof.

Table II

Safety Features of Extrusion Ignition Formulations formula# Adhesive fiber ABL ABL Sliding 1 ^Cyanamer® N-300 none 80GL 800@8 ft/s GL 2 Methylcellulose none 6.9GL 240@6 ft/s YL 3 ^Cyanamer® A-370 none 21GL 800@8 ft/s GL 4 ^Cyanamer® P-21 none 21GL 800@8 ft/s GL 6 Tragacanth Gum none 21GL 320@8 ft/s GL 7 Locust Bean Gum none 13GL 180@6 ft/s YL 8 Karaya gum none 21GL 240@8 ft/s GL 9 PAM 10000MW none 41GL 800@8 ft/s GL 10 Guar Gum, FG-1 none 11GL 100@6 ft/s YL 11 gelatin, leather none 33GL 800@8 ft/s GL 12 ^Cyanamer® N-300 C fiber, Fortafil® ^F5C 33GL 800@8 ft/s GL 13 ^Cyanamer® N-300 C fiber, Pyrograph ^™ III 41GL 800@8 ft/s GL 14 Cyanamer® ^- 300 SiC whiskers, Silar ^® 41GL 800@8 ft/s GL 15 Cyanamer® ^- 300 ^Saffil® Type 590 51GL 420@8 ft/s GL 1- The unit is centimeters. 2- The unit is in pounds.

Table III

Extruded ignition rod test results formula# Adhesive ID Additive ID water ¹ Durability ² Hole plugging % ³ 1 ^Cyanamer® N-300 none 14.5 55 100 3 ^Cyanamer® A-370 none 12.5 40 9 4 ^Cyanamer® P-21 none 11.5 34 45 5 ^Cyanamer® N-300LMW none 14.5 69 100 6 Tragacanth Gum none 19 32 33 8 Karaya gum none 14.5 25 100 9 PAM 10000MW ⁴ none 14 NA NA 11 gelatin, leather none 10.5 44 100 12 ^Cyanamer® N-300 C fiber 16.5 69 100 13 ^Cyanamer® N-300 C fiber 16.5 97 83 14 ^Cyanamer® N-300 SiC whiskers 17.5 51 100 15 Cyanamer® ^- 300 Saffil® ^type 15.5 94 100 1 Parts per 100 parts of water required to add to formulation for efficient completion of single-screw extrusion 2 Units are mil-pounds. 3 Percent plugged holes determined from six or more 0.33"OD, 0.88"ID, 2"L ignition rods. 4 Formulation No. 9 did not extrude well. Example 3

As can be seen from Table IV, a set of igniters containing fibers was formulated with the goal of increasing the durability of the extruded ignition rods. All formulations have favorable safety profiles. A sample (325 grams) of each formulation was mixed at 13.5 parts per 100 parts water in a Baker-Perkins pinto mixer. After 1 minute of dry blending of KNO ₃ and ^Cyanamer® A-370, water was added followed by 5 minutes of mixing. The fiber was then added in two additions, and the boron was added in three additions, mixing for 3 minutes after each addition. After the final "scratch out", the formulation was mixed for an additional 10 minutes. The resulting tan doughy material was made into -4 mesh pellets which were fed to a Haake 25 mm single-screw extruder. The igniter formulation was extruded through a 12 point star die with a maximum diameter of 0.33" and a minimum diameter of 0.305". The die consisted of a centrally located 0.15" diameter female ejector pin. The extruded ignition formulation was cut into 7" lengths. Extrude another 10 2" long. Pilot sticks were dried overnight at 165°F.

There was no evidence of any _KNO3 /binder oozing out of the igniter grain after drying. The charge was ignited using smoke injection from an ES013 squib facing a 0.15" ID hole in the charge. The igniter charge was placed in a 0.4" ID, 0.49" wall cylindrical fixture with approximately 95 cells along its length and diameter. Evenly spaced 0.109" ID holes drilled in direction. The times required for the flame to travel from the front to the opposite end of the charge after ignition with the squib are given in Table V. Time is measured with 1000 frames per second television. Typically, only a few milliseconds are required. The durability of the 2" long grain was determined as described in Example 2. The results are shown in Table V. The formulation containing 2% polyethylene fiber had the greatest durability so far. The powders were ignited with formulations #3 and #19 The column was fired with an RDC inserted into a 0.15" hole. Formulation #19 with polyethylene fibers caused minimal delay before igniting the pyrotechnic composition.

Table IV

Ignition Formula Containing ^Cyanamer® A-370 and Selected Fibers formula % _KNO3 %boron % ^Cyanamer® A-370 Fiber ID %fiber 3 76.30 16.70 7.00 none 0.00 16 76.70 14.30 7.00 Pyrograph ^™ III, Micro 2.00 17 74.80 16.20 7.00 ^Saffil® Type590, Micro 2.00 18 74.80 16.20 7.00 ^Nextel® 1/8″Ceramic 2.00 19 77.20 13.80 7.00 Allied, Spectra 900, 1/8″ 2.00 20 76.50 14.50 7.00 Celanese 1/8″PBI 2.00

Table V

Compilation of Test Results for Possible Extrusion Ignition Agents Containing Fibers formula Fiber ID ignition ignition Durability ³ coefficient 3 none 2 2 96 39 3 ¹ None, 0.125″ ID 9 8 101 25 16 Pyrograph ^™ III, Micro 5 65 39 17 ^Saffil® Type590, Micro 1 107 4 18 ^Nextel® 1/8″Ceramic 3 76 69 19 Allied, Spectra 900, 1/8″ 17 1 357 17 20 Celanese 1/8″PBI 13 126 twenty two ¹ Formulation 3 with grains of 0.125" ID instead of the nominal 0.15" ID. ² Time required for the flame front on a 7" grain lit at one end to reach the opposite end. This time is in milliseconds. This data was obtained as described in Example 3. ³ Same as footnote 1, but cured at the opposite end from which ignition was initiated Epoxy seals the 0.15" ID holes. ⁴ Units are mil-pounds.

In formulations 16, 17, 18, 19 or 20, the "fiber ID" can be characterized by carbon fiber, alumina fiber, aluminosilicate, polyethylene and polybenzimidazole, respectively.

Example 4

By making a premix of guar gum (5.0% by weight, 0.25 g) and water (deionized water, 15.0% by weight, 1.75 g), the premix was mixed with potassium nitrate (average particle size about 26 microns) , 75% (weight), 3.75 g) combined, and adding fuel, boron (amorphous; 20.0% (weight), 1.00 g) to give an extrudable igniter composition.

Example 5

An extrudable igniter composition was obtained as in Example 4, but using 20.0% by weight water.

Example 6

Obtain extrudable igniter composition as in Example 4, but the amount of fuel, boron is increased to 22.0% (weight) (1.10 grams), and the amount of binding agent, guar gum is reduced to 3.0% (weight) (0.15 grams).

Example 7

An extrudable igniter composition was prepared according to the procedure of Example 4, but the binder was polyacrylamide (cyanamer "N-300", 5.0% by weight, 0.25 g, produced by Cyanamid, USA).

Example 8

By adding potassium nitrate (210 grams) and polyacrylamide (14 grams, cyanamer "N-300" produced by Cyanamid, USA) to the tank, add water (44.8 grams) to the tank and mix for 1 minute, then add boron (amorphous, 56.0 grams), followed by mixing for about 4 minutes to prepare an extrudable igniter mixture.

Example 9

An extrudable igniter composition was prepared as in Example 8, but with 50.4 grams of water, by first dry mixing together potassium nitrate and binder, followed by water mixing for 1 minute. Powdered boron was then added and mixing continued for 4 minutes.

Example 10

The igniter composition prepared according to Example 8 was pelletized, dried, and compressed into pellets 1/2 inch in diameter and 1 inch long. The pellet was then sealed on all but one side and burned by igniting the unsealed side in a closed pressurized vessel at 1000, 2000 and 3000 ^psi . The burn rates were observed to be 4.16 in/sec, 4.32 in/sec, 4.42 in/sec, respectively.

Example 11

A portion of the wet igniter composition prepared as described in Example 9 was placed in a 2 inch diameter piston extruder and forced through a suitable die to give a cylindrical extrudate about 0.3 inch in diameter with a central hole , the diameter of the hole is about 0.06 inches. The extrudate was partially dried and cut into 7 inch lengths before final drying. The resulting ignition rods were then tested in a gas generating apparatus consisting of a tubular metal cylinder, 8 inches long, approximately 2 inches in diameter, closed at both ends, provided with radial ports. One closed end is also fitted with a starter squib. The ignition rod remains in the center of the tube and a 7 inch long rapid detonation cord (RDC) is placed in the center hole of the rod. The gas-generating pellets were then loaded into the gas-generating apparatus and tested in a closed tank. Similar results were obtained with the ignition rod as with a conventional fire transmission system in which the open-hole metal tube contained the same amount of ignition charge, and the RDC replaced the ignition rod/RDC combination. In all cases, ignition of the gas-generating pellet was observed within 8 milliseconds.

Example 12

Two 50 gram portions were prepared using 20% boron, 75% potassium nitrate, 5% Cytec Cynamer ^(R) N-300 brand polyacrylamide (15,000,000 molecular weight) and 17.5% by weight water. The mixture was combined and loaded into a 2.0 inch diameter piston extruder. The piston extruder was pressurized to 300 ^psi and the ignition rod was extruded. The igniter composition was initially extruded as a 0.100 inch diameter solid rod and also as a 0.100 inch diameter ignition rod with a 0.030 inch diameter central hole. Pilot sticks were cut into 6-inch lengths and dried overnight at 135°F before use. The center hole ignition rod was successfully demonstrated in the XM-212 false target flare. Two XM 212 grains were produced. One with a traditional slurry detonator, and the other with a three-hole igniter rod. Figure 1 shows the structure of the flare with the ignition rod.

Example 13

Also add the ignition rod to the main ignition system of the MJU-10 false target flare. The MJU-10 flare requires a larger ignition system than the XM-212 flare. Accordingly, the ignition formulation was extruded through a 12 point star die having a maximum diameter of 0.33 inches and a minimum diameter of 0.30 inches. The extrusion die also included a 0.80 inch diameter die ejector pin used to produce a center hole grain. Extruded ignition rods were cut into 5.0 inch lengths and then dried at 135°F for 24 hours. Then insert the ignition rod into the center hole of the propellant grain of the MJU-10 flare. The MJU-10 flare was successfully ignited with an ignition rod.

Considering the foregoing, the ignition rod would reduce cost, reduce production time, and simplify the design of the push-on MJU-10 flare ignition system.

Considering the circumstances of the embodiment, the ignition rod can be used for a large number of false target flare devices. They help to improve the reliability of flare ignition by reducing the number of improper initiators, while improving the safety of flare production by avoiding the flammable solvents commonly used when using conventional initiators.

Claims (9)

CLAIMS 1. A flare comprising a housing, a propellant contained in said housing, an ignition system for igniting said propellant, said ignition system comprising an extruded ignition element mounted in said propellant, said Extruded ignition elements are made from components comprising a water-soluble or water-dispersible binder, at least one oxidizing agent, at least one fuel, and optionally fibers. 2. The flare according to claim 1, wherein the binder comprises at least one of poly-N-vinylpyrrolidone, polyvinyl alcohol or copolymers thereof, polyacrylamide, sodium polyacrylate, or gum. 3. A flare according to claim 1 or 2, wherein the adhesive comprises at least one polyacrylamide or at least one gum. 4. The flare according to any one of claims 1-3, wherein said oxidizing agent is present in an amount of about 40-90% by weight relative to the dry ingredients used to formulate said extrudable igniter composition . 5. The flare according to any one of claims 1-4, wherein said oxidizing agent comprises an organic oxidizing agent. 6. The flare according to any one of claims 1-5, wherein said oxidizing agent contains at least one ion selected from the group consisting of nitrates, nitrites, chlorates, perchlorates, peroxides and superoxides form. 7. A flare according to any one of claims 1-6, wherein said extruded ignition element comprises fibres. 8. The flare according to any one of claims 1-7, wherein said fibers comprise polyolefin fibers, polyamide fibers, polyester fibers or poly(2,2'(m-phenylene)-5,5- At least one fiber in the bisbenzimidazole fiber. 9. The flare of claim 1, wherein (a) the binder comprises at least one of poly-N-vinylpyrrolidone, polyvinyl alcohol or copolymers thereof, polyacrylamide, sodium polyacrylate, or gum; (b) The oxidizing agent is present in an amount of about 40-90% by weight relative to the dry components used to formulate the ignition element, and the oxidizing agent contains at least one selected from the group consisting of nitrates, nitrites, chloric acid ionic forms of salts, perchlorates, peroxides and superoxides; (c) the extruded ignition element contains polyolefin fibers, polyamide fibers, polyester fibers or poly(2,2'(m- A low-aspect-ratio fiber consisting of at least one of phenylene)-5,5-bisbenzimidazole fibers.

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