Perchlorate-free red pyrotechnic illuminant compositions

Abstract

The present invention is a red-light-emitting composition based upon a potassium periodate oxidizer formulation, which is useful as the illuminant in the US military's M662 40 mm red star parachute projectile, and which composition is composed of readily commercially available ingredientsingredients that are environmentally friendly. Further, the subject inventive potassium periodate formulation provides significant enhanced illumination and safety versus the current military M662 illuminant which is based upon potassium perchlorate oxidizer formulation.

Claims

1. An environmentally friendly red pyrotechnic illuminant composition with improved luminosity and improved safety consisting of: a. from about 41.1 to about 39.1 weight percent of a first oxidizer, which oxidizer is strontium nitrate; b. from about 30.8 to about 35.8 weight percent of an inorganic fuel, which inorganic fuel is 30/50 magnesium powder; c. about 12.8 weigh percent of a chlorine donor, which chlorine donor is polyvinyl chloride; d. from about 10.3 to about 5.3 of a second oxidizer, which second oxidizer is potassium periodate; and e. from about 5.0 to about 7.0 of binder system; f. wherein said red pyrotechnic illuminant composition provides a luminous intensity of at least 26,471 candela and a friction sensitivity which is at least 240 Newtons.

2. The environmentally friendly red pyrotechnic illuminant composition with improved luminosity and improved safety of claim 1, wherein the binder system is comprised of 80 weight percent of a low viscosity liquid bisphenol-A based epoxy resin diluted with cresyl glycidyl ether and 20 weight percent of a medium to low viscosity, reactive polyamide-based resin solution that cures at room temperature.

3. The environmentally friendly red pyrotechnic illuminant composition with improved luminosity and improved safety of claim 1, wherein the dominant wavelength ranges from 607.2 to 608.4 nm and the spectral purity is at least 86.8 percent.

4. The environmentally friendly red pyrotechnic illuminant composition of claim 1 wherein the potassium periodate mean particle size is about 42.3 m.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention comprises environmentally safe and significantly brighter red pyrotechnic illuminant compositions, useful in U.S. military M662 red star parachute 40 mm projectiles, in which a potassium periodate (KIO.sub.4) oxidizer is substituted for the conventional strong potassium perchlorate (KClO.sub.4) oxidizer. In fact, a potassium periodate based pyrotechnic illuminant of the present inventive formulation (Table 3, Formulation Gbelow) burned 1.39 times brighter, with 1.52 times the luminous efficiency (in [(cd-s)g.sup.1]), and had a longer burn time than the current M662 potassium perchlorate based red pyrotechnic illuminant formulation. Further, the luminosity (in cd) of this particular inventive formulation exceeded the luminosity of the prior art alternative strontium bis-(1-methyl-5-nitriminotetrazolate) monohydrate and 5-AT based formulations.

(2) Alternative embodiments of the present potassium periodate formulations shown in Table 2 above have been selected and detailed in Table 3 below. The performance data relevant to M662 40 mm red star illuminant parachute projectiles for the selected embodiments shown in Table 3 are detailed in Table 4, also shown below. For reference/control purposes, also shown in Table 4 are the same performance characteristics data for the current M662, red star parachute potassium perchlorate based pyrotechnic illuminant formulation.

(3) TABLE-US-00003 TABLE 3 Alternative embodiments of the present invention - Formulations G-J. Ingredient Wt. % Formulation G Sr(NO.sub.3).sub.2 41.1 Mg 30/50 30.8 PVC 12.8 KIO.sub.4 10.3 Epon 813/Versamid 140 5.0 Binder Formulation H Sr(NO.sub.3).sub.2 41.1 Mg 30/50 35.8 PVC 12.8 KIO.sub.4 5.3 Epon 813/Versamid 140 5.0 Binder Formulation I Sr(NO.sub.3).sub.2 39.1 Mg 30/50 30.8 PVC 12.8 KIO.sub.4 10.3 Epon 813/Versamid 140 7.0 Binder Formulation J Sr(NO.sub.3).sub.2 39.1 Mg 30/50 35.8 PVC 12.8 KIO.sub.4 5.3 Epon 813/Versamid 140 7.0 Binder

(4) TABLE-US-00004 TABLE 4 Performance data for alternative embodiments G-J vs. current M662 illuminant. BT.sup.(a) LI.sup.(b) LE.sup.(c) DW.sup.(d) SP.sup.(e) Formulation (s) (cd) ([cd s]g.sup.1) (nm) (%) Current 40.4 19,098 9,572 607.2 86.8 M662 G 43.8 26,471 14,540 607.8 87.0 H 39.7 31,995 15,908 607.2 86.8 I 44.1 23,478 12,964 608.4 86.8 J 42.2 27,307 14,443 608.1 86.8 Wherein: .sup.(a)BT = Burn time; .sup.(b)LI = Luminous intensity; .sup.(c)LE = luminous efficiency; .sup.(d)DW = dominant wavelength; .sup.(e)SP = spectral purity.

(5) As can be seen from Table 4, and as stated above, inventive embodiment Formulation H provided almost 13,000 additional candela or luminous intensitya 67.5% increase in luminositywith only a reduction in burn time from the current 40.4 to 39.7 seconds versus the current M662 potassium perchlorate based formulation. Further, as stated above, inventive embodiment Formulation Gbelow) burned 1.39 times brighter, with 1.52 times the luminous efficiency (in [(cd-s)g.sup.1]), and had a 3.4 second, or over 8.4% greater/longer burn time than the current M662 potassium perchlorate based red pyrotechnic illuminant formulation. Further still, the dominant wavelength and spectral purities of all tested inventive potassium periodate based red pyrotechnic embodiments were well within the U.S. military specifications for the M662 red pyrotechnic illuminanti.e. 620+/20 nanometers and a minimal 76% purity. All of the performance measurement results are not only significantbut, surprisingly so.

(6) Critical to military applications, such as the subject inventive M662 potassium periodate based red pyrotechnic illuminant formulations, is the safety in manufacture, handling, and storage of the particular pyrotechnic material. The subject inventive formulations proved significantly and surprisingly less sensitive to friction ignition than the current M662 potassium perchlorate based materialas stated above, the friction sensitivity of embodiment I of the inventive formulation proved to be greater than 360 Newtons (N) versus only 80 N for the current M662 potassium perchlorate based red pyrotechnic materialan increase of 450%. Further, the inventive formulations also exhibited a high level of thermal stability and were found to be insensitive to electrostatic discharge. Table 5, below, shows a comparison of the current M662 potassium perchlorate based material vs. selected alternative embodiments of the present invention (i.e. alternative embodiment H is omittedas it has a shorter burn time than the current potassium perchlorate material and hence doesn't meet the standard for burn time for the M662 40 mm red star parachute illuminant).

(7) TABLE-US-00005 TABLE 5 Sensitivity of the current and inventive illuminants. Impact Friction Electrostatic Sensitivity.sup.1 Sensitivity.sup.2 Discharge Formulation (J) (N) Sensitivity.sup.3 (J) Current M662 6.86 80 >0.25 G 7.35 240 >0.25 I 7.35 >360 >0.25 J 5.88 240 >0.25 Note 1. NATO Standardization Agreement (STANAG) 4489, Ed. 1 Explosives, Impact Sensitivity Tests. 17 Sep. 1999. Note 2. NATO Standardization Agreement (STANAG) 4487, Ed. 1 Explosives, Friction Sensitivity Tests, 22 Aug. 2002. Note 3. NATO Standardization Agreement (STANAG) 4490, Ed. 1. Explosives, Electrostatic Discharge Sensitivity Tests, 19 Feb. 2001.

(8) As summarized above, in formulating the present inventive pyrotechnic illuminant compositions, useful as a red M662 40 mm parachute illuminant, an embodiment of the ingredients detailed in Table 2 are mixed under ambient condition. More specifically, a preferred method is to perform the mixing using a Hobart air mixing bowl, Hobart, Troy, N.Y., where the Hobart mixer is equipped with a B-Blade. As further detailed above, preferably the binder is first added to the Hobart mixer and mixed with the magnesium; the potassium periodate is then mixed in; the PVC and strontium nitrate are then mixed in (which two ingredients can be premixed and added together)all mixing is done until a uniform mixture is obtained (wherein about 10 to about 20 minutes mixing can be required to obtain a uniform mixture). With the use of the preferred Epon 813/Versamid 140 binder system, the final unpacked mixture should be allowed to sit and dry, unconsolidated for about 1 to about 3 hourswhereupon it can be packed into the desired illuminant form and preferably cured in an oven, at about 60 degrees C. overnight, i.e. for a period of about 12 hours. It is important to note that there is a difference between these drying and curing steps;

(9) wherein, drying is just a physical process and curing is chemical (i.e. growth of cross-linked chains). Finally, the consolidation must be done before oven curing, and for example, may involve an 80 g increment, preferably with a dead load of about 10,000 pounds, for a dwell time of at least about 10 seconds.

(10) The particular ingredients useful in the present inventive red pyrotechnic illuminant are all commercially available. Specifically, the strontium nitrate (Sr(NO.sub.3).sub.2) oxidizer, with a preferred volume-based mean particle size of about 23.3 m, and the polyvinyl chloride (PVC) chlorine donor, with a preferred volume-based mean particle size of about 123.4 m, are available from Hummel Croton, located in South Plainfield, N.J. The second oxidizer, potassium periodate, with a preferred volume-based mean particle size of about 42.3 m, is available from Ashland Chemical Company, which has a location in Budd Lake, N.J. The 30 to 50 mesh inorganic fuel/gray body emitter magnesium (Mg 30/50), with a preferred volume-based mean particle size of about 523.44 m, is available from Magnesium Elektron, located in Manchester, N.J. The Epon 813 component of the binder system (80%) is available from Momentive, located in Columbus, OH. And the Versamid 140 component of the binder system (20%) is available from BASF, located in Cincinnati, Ohio.