AU2013206582B2 - Pyrotechnic active composition with a combustion accelerant - Google Patents

Abstract

Abstract The invention relates to a pyrotechnic active composition comprising a combustion fuel, an oxidant for the combustion fuel, a combustion accelerant and optionally a binder, wherein the combustion accelerant is present in the form of particles which are distributed in the active composition, wherein the combustion accelerant is a solid which is expandable at least by a factor of 2 by input of heat.

Description

The invention relates composition comprising a for the combustion fuel, to a pyrotechnic active combustion fuel, an oxidant a combustion accelerant and optionally a binder, wherein the combustion accelerant is present in the form of particles which are distributed in the active composition, wherein the combustion accelerant is a solid which is expandable at least by a factor of 2 by input of heat.

2013206582 28 Jun2013

Pyrotechnic active composition with a combustion accelerant

The invention relates composition comprising a for the combustion fuel, to a pyrotechnic active combustion fuel, an oxidant a combustion accelerant and optionally a binder. Ferrocene is known in the prior art as a catalyst in rocket propellants. However, ferrocene only accelerates combustion of the rocket propellant by at most approx. 20%.

Kinematic pyrotechnic decoys are conventionally constructed such that combustion proceeds in the interior of the active composition. A combustion channel is conventionally arranged for this purpose in the middle of the active composition. The combustion channel reduces the quantity of active composition which can be provided in a specific volume. A more advantageous structure for a kinematic pyrotechnic decoy is one in which the active composition burns from an end face, because such a structure is simpler and, thanks to the omission of the combustion channel, more active composition can be accommodated per unit volume. Such an end-burner functions more reliably and may be ignited more readily and rapidly than an active composition configured as an internal burner. However, an active composition which combusts rapidly enough in such a structure to function as a decoy has not hitherto been available.

A decoy is conventionally approx. 150 mm long and is intended to burn for at most 5 seconds. When the decoy is designed as an end-burner, the combustion rate would therefore have to be at least 30 mm/s in order to comply with the desired combustion time. Conventional active compositions for decoys, however, burn at a rate of at most 12 mm/s. Combustion catalysts may be used to accelerate combustion. The known combustion catalyst

2013206582 28Jun2013 ferrocene, however, only accelerates combustion by approx. 20%. The object of the present invention is accordingly to provide a pyrotechnic active composition with a combustion accelerant which enables faster combustion of the active composition than does the known ferrocene.

Said object is achieved by the features of Claim 1. Convenient developments are revealed by the features of Claims 2 to 13.

The present invention provides a pyrotechnic active composition comprising a combustion fuel, an oxidant for the combustion fuel, a combustion accelerant and optionally a binder. A binder may be omitted if another component of the active composition acts as a binder. The combustion accelerant is here present in the form distributed in the active combustion accelerant is a solid which is expandable at least by a factor of 2 by input of heat. Expansion of the solid does not modify of particles which are composition, wherein the the chemical reaction of combustion thereof, but modifies the structure of the active composition on instead purely physically the active composition on combustion thereof. Expansion of the solid with input of heat causes the active composition to crumble at the burning surface, such that the burning area is enlarged. The larger the burning area, the higher is the mass flow rate of burning active composition. Using the combustion accelerant, it is possible to achieve combustion rates which are considerably higher than those of known chemical combustion catalysts. No chemical modifications to the active composition are required in order to introduce the purely physically active combustion accelerant. The combustion accelerant may consequently be combined with all known active compositions. The active composition according to the

2013206582 28 Jun 2013 invention may be an active composition for a decoy or a propellant.

The combustion accelerant may also be used in 5 combination with chemical or any other catalysts. Still higher combustion rates may be achieved in this manner.

A further advantage of the active composition according to the invention is that the combustion accelerant contained therein does not react with conventional combustion fuels, oxidants and binders at conventional storage temperatures and thus does not impair the storage life of the active composition. Using the active composition according to the invention, black body decoys can be designed as end-burners. The entire available volume of a decoy may thus be utilized because no recess is required in the active composition for combustion of the active composition as an internal burner and for ignition. An ignition paste, as required in previous decoy active compositions, is not required in the active composition according to the invention. In this way, the safety of a decoy equipped with the active composition according to the invention is increased and production of a decoy containing the active composition is simplified. Moreover, the ignition delay conventional in previous decoy active compositions is considerably shortened, because only a small area need be ignited. Furthermore, expandable solids are generally inexpensive and readily commercially obtainable.

In one development of the active composition according to the invention, the particles are uniformly distributed in the active composition. In this way, rapid combustion which is uniform and predictable is achieved.

2013206582 28 Jun 2013

The particles may have an average grain size in the range from 0.01 mm to 6 mm, in particular 0.1 mm to 5 mm. The combustion accelerant may be a solid which is expandable at least by a factor of 5, 10, 20, 50, 100,

200 or 500 by input of heat. The active composition may contain the combustion accelerant in a proportion of 0.1 to 10 wt.%, in particular of 1 to 5 wt. %.

The combustion accelerant may be an intumescent graphite or a sodium silicate. In addition to its expanding action, as yet unexpanded intumescent graphite, in particular if it is coarse-grained intumescent graphite, has a thermally conductive action. It is capable of conducting heat from the flame into the as yet uncombusted active composition and so further accelerating combustion. A further action of the intumescent graphite is that expanded intumescent graphite forms a thermally insulating layer on the surface of the active composition. This layer retains the heat at the surface and simultaneously glows in a flame which burns above the surface. Both effects and the thermal conduction of the as yet unexpanded intumescent graphite direct heat from the flame back onto the surface of the active composition. In this way, combustion of the active composition is further accelerated.

The active composition may also contain a porous and/or thermally conductive additive. Thermally conductive additives accelerate combustion by conducting heat from the flame into the active composition. The additive may comprise carbon fibres, in particular bundled carbon fibres, charcoal and/or activated carbon. Carbon fibres in each case conduct heat into the active composition with the first end thereof, while the second end thereof is located in the flame. At the same time, a pore is in each case formed in the active composition

2013206582 28Jun2013 in the region of the first ends of the carbon fibres, since the active composition surrounding the respective carbon fibres is gasified by the introduced heat. The pores formed in the active composition enlarge the surface area thereof and consequently accelerate the combustion thereof. In the case of bundled carbon fibres, pore-like cavities are present as a result of the bundling, since the fibres in each case have a round cross-section and are so incapable of lying completely flush against one another. The porosity of the additive further accelerates combustion.

Combustion of the active composition according to the invention may be accelerated by the following 4 effects:

1. mechanical comminution of the burning surface,

2. thermal insulation of the surface and thus higher surface temperature on the combusting active composition,

3. greater reflection onto the surface of the active composition from glowing combustion accelerant and

4. thermal conduction from the flame into the active composition.

The combustion fuel may be a metal, a semimetal or a 30 mixture or alloy of metals and/or semimetals or a mixture or alloy of at least one metal and at least one semimetal. The combustion fuel may comprise aluminium, magnesium, titanium, zirconium, hafnium, calcium, lithium, niobium, tungsten, manganese, iron, nickel, cobalt, zinc, tin, lead, bismuth, tantalum, molybdenum, vanadium, boron, silicon, an alloy or mixture of at least two of these metals or semimetals, a zirconium6

2013206582 28 Jun 2013 nickel alloy or mixture, an aluminium-magnesium alloy or mixture, a lithium-aluminium alloy or mixture, a calcium-aluminium alloy or mixture, an iron-titanium alloy or mixture, a zirconium-titanium alloy or mixture, or a lithium-silicon alloy or mixture.

Titanium, zirconium, hafnium, niobium, tantalum, molybdenum and vanadium can form carbides with the carbon particles or soot particles arising therefrom.

The carbon here acts as oxidant or further oxidant for the stated metals. The resultant carbides assume solid form at the temperatures arising on combustion of the active composition and emit radiation as carbide particles .

The binder may comprise a fluoroelastomer, in particular a fluororubber, such as for example Viton® from DuPont Performance Elastomers. The oxidant may be a halogen-containing polymer, in particular polytetrafluoroethylene (PTFE) or polychloroprene. The active composition may furthermore contain a combustion catalyst, in particular ferrocene, iron acetylacetonate or copper phthalocyanine, for accelerating combustion.

The invention is illustrated in greater detail below with reference to exemplary embodiments.

The compositions of Examples 1 to 10 stated below were produced as follows:

The dry components and 5 conductive rubber cubes were mixed for one hour at 120 revolutions/minute by means of a mixer in a 250 ml mixing container. The resultant mixture was transferred into a stainless steel bowl, the rubber cubes removed and 3M Fluorel FC-2175 fluororubber as a 10% solution in acetone was added as binder. The composition was stirred to form a

2013206582 28 Jun 2013 homogeneous dough and mixed until the acetone had evaporated to such an extent that the composition became granular. The resultant granules were dried at 50°C.

g portions of the granules were pressed to form tablets. The pressing tool had an internal diameter of 16.8 mm. The pressing pressure was 1500 bar. The densities of the tablets were between 85 and 95% of the theoretical maximum density (TMD). All the tablets were coated on their cylindrical faces with polychloroprene (Macroplast) and adhesively bonded with polychloroprene to 80x80x5 mm steel plates in order to limit combustion thereof to one free end face. The tablets were left to dry overnight at room temperature.

Examples 11 and 12 relate to cast active compositions and were produced as follows:

All components, amounting in total to 50 g, were processed in a stainless steel bowl with addition of 10 g of dichloromethane to form a uniform dough and then scattered on a PTFE film and dried for one hour at 50°C in order to remove the dichloromethane. The resultant granules were manually compressed in the pressing tool with an internal diameter of 16.8 mm and ejected. A cylindrical body approx. 35 mm in length was produced in this way. Said body was cured for 48 hours at 60°C and then coated on its cylindrical face with polychloroprene in order to inhibit ignition on this face. The body was then adhesively bonded to a 80χ80χ5 mm steel plate so that the cylinder cannot move while the combustion time is being measured. The steel plates with the tablets and the cylindrical bodies were in each case fastened to a stand and ignited on the respective end faces. Combustion was recorded with a video camera. Combustion times were determined from the

2013206582 28 Jun 2013

- 8 video recordings. Combustion rates were then calculated from the length of the tablet or cylinder and the combustion time.

Example 1:

Standard prior art MTV (magnesium-Teflon®-Viton) active composition:

Substance	Grade	wt. %	Misc.
Magnesium	LNR61	60.0
Teflon powder	Dyneon TF 9205	35.0
Viton	3M Fluorel FC-2175	5.0	TMD = 1881

Combustion rate 3.0 mm/s at normal pressure.

Example 2:

Standard MTV active composition with graphite powder:

Substance	Grade	wt. %	Misc.
Magnesium	Ecka Non-ferrum LNR 61	60.0
Teflon powder	Dyneon TF 9205	30.0
Viton	3M Fluorel FC-2175	5.0	TMD = 1852
Graphite powder	Merck 1.04206.2500	5.0

Combustion rate 3.0 mm/s at normal pressure. The graphite has no influence on the combustion rate.

2013206582 28Jun2013

Example 3:

Standard MTV active composition with copper phthalocyanine as combustion catalyst:

Substance	Grade	wt. %	Misc .
Magnesium	Ecka Non-ferrum LNR	60.0
	61
Teflon powder	Dyneon TF 9205	34.0
Viton	3M Fluorel FC-2175	5.0	TMD = 1861
Copper phthalocyanine	BASF Vossenblau	1.0
Combustion rate	3.2 mm/s at normal pressure.
Example 4:
Standard MTV active composition	with ferrocene as
combustion catalyst:
Substance	Grade	wt. %	Misc.
Magnesium	Ecka Non-ferrum LNR	60.0
	61
Teflon powder	Dyneon TF 9205	34.0
Viton	3M Fluorel FC-2175	5.0	TMD = 1859
Ferrocene	Arapahoe Chemicals	1.0

Combustion rate 3.5 mm/s at normal pressure.

2013206582 28 Jun 2013

Example 5:

MTV active composition according to the invention with intumescent graphite as combustion accelerant:

Substance	Grade	wt. %	Misc .
Magnesium	Ecka Non-ferrum LNR 61	60.0
Teflon powder	Dyneon TF 9205	30.0
Viton	3M Fluorel FC-2175	5.0	TMD = 1852
Intumescent graphite	NGS ExEF-80	5.0

Combustion rate 8.0 mm/s at normal pressure.

Example 6:

MTV active composition according to the invention with intumescent graphite as combustion accelerant and ferrocene as combustion catalyst:

Substance	Grade	wt. %	Misc .
Magnesium	Ecka Non-ferrum LNR	60.0
Teflon powder	61 Dyneon TF 9205	30.0
Viton	3M Fluorel FC-2175	5.0	TMD = 1850
Intumescent	NGS ExEF-80	4.0
graphite Ferrocene	Arapahoe Chemicals	1.0

Combustion rate 10.0 mm/s at normal pressure.

2013206582 28 Jun2013

Example 7:

Quick-burning standard black body set with ferrocene as combustion catalyst:

Substance	Grade	wt. %	Misc.
Magnesium	SFM MGP-325	55.0
Teflon	Fluon G163	18.0	TMD = 1844
Boron	1 pm	8.0
Titanium	Chemetall grade E pm	6.0
Ferrocene	Arapahoe Chemicals	1.0
Viton	3M Fluorel FC-2175	12.0

Combustion rate 11.0 mm/s at normal pressure.

Example 8:

Quick-burning black body set according to the invention with intumescent graphite as combustion accelerant and ferrocene as combustion catalyst:

Substance	Grade	wt. %	Misc .
Magnesium	SFM MGP-325	50.0
Intumescent	NGS ExEF-150	5.0
graphite
Teflon	Fluon G163	18.0	TMD = 1867
Boron	1 pm	8.0
Titanium	Chemetall grade E	6.0
Ferrocene	Arapahoe Chemicals	1.0
Viton	3M Fluorel FC-2175	12.0

Combustion rate 24 mm/s at normal pressure.

2013206582 28 Jun2013

Example 9:
Quick-burning black	body set	with	ferrocene as
combustion catalyst	and carbon	fibres	as thermally
5 conductive additive:

Substance	Grade	wt. %	Misc .
Magnesium	SFM MGP-325	53.0
Graphite	Edelgraphit GmbH	22.0	TMD = 1963
fluoride	white CFi.i
Boron	1 pm	4.0
Titanium	Svenska kemi	7.0
	0-100 pm
Chopped carbon	Furthfil 150 3 mm	8.0
fibre
Ferrocene	Arapahoe Chemicals	1.0
Viton	3M Fluorel FC-2175	5.0

Combustion rate 16.0 mm/s at normal pressure.

2013206582 28 Jun 2013

Example 10:

Quick-burning black body set according to the invention with intumescent graphite as combustion accelerant, carbon fibres as thermally conductive additive and ferrocene as combustion catalyst:

Substance	Grade	wt. %	Misc.
Magnesium	SFM MGP-325	48.0
Intumescent	NGS ExEF-80	5.0
graphite
Graphite	Edelgraphit GmbH	22.0	TMD = 1970
fluoride	white CFi.i
Boron	1 pm	4.0
Titanium	Svenska kemi	7.0
	0-100 pm
Chopped carbon	Furthfil 150 3 mm	8.0
fibre
Ferrocene	Arapahoe Chemicals	1.0
Viton	3M Fluorel FC-2175	5.0

Combustion rate 100 mm/s at normal pressure.

Example 11:

Conventional rocket propellant with iron acetylacetonate as combustion catalyst:

Substance	Grade	wt. %	Misc .
Ammonium perchlorate	100 pm	85.50
HTPB	R45HT-M M = 2800	13.47
IPDI Iron acetylacetonate		1.01 0.02	TMD = 1678

HTPB = hydroxy-terminated polybutadiene

2013206582 28 Jun 2013

IPDI = isophorone diisocyanate

Combustion rate 1.6 mm/s at normal pressure.

Example 12:

Rocket propellant according to the invention with iron acetylacetonate as combustion catalyst and intumescent graphite as combustion accelerant:

Substance	Grade	wt. %	Misc.
Ammonium	100 pm	84.50
perchlorate
HTPB	R45HT-M M = 2800	11.63
IPDI		0.87	TMD = 1711
Intumescent	NGS Ex 150 SC	3.0
graphite
Iron		0.02
acetylacetonate

Combustion rate 4.5 mm/s at normal pressure.

2013206582 17 Nov 2017

Claims (17)

1. Claims

   1. Pyrotechnic active composition comprising a combustion fuel, an oxidant for the combustion fuel and a combustion accelerant, wherein the combustion accelerant is present in the fonn of particles distributed in the active composition, wherein the combustion accelerant is a solid which is expandable at least by a factor of 2 by input of heat, and wherein the combustion accelerant is present in the active composition in a proportion of 1 to 5 wt.%.
2. 2. The active composition according to Claim 1, wherein the particles are uniformly distributed in the active composition.
3. 3. The active composition according to one of the preceding claims, wherein the particles have an average grain size in the range from 0.01 mm to 6 mm.
4. 4. The active composition according to one of the preceding claims, wherein the particles have an average grain size in the range from 0.1 mm to 5 mm.
5. 5. The active composition according to one of the preceding claims, wherein the combustion accelerant is a solid expandable at least by a factor of 5, 10, 20, 50, 100, 200 or 500 by input of heat.
6. 6. The active composition according to one of the preceding claims, wherein the combustion accelerant is an intumescent graphite or a sodium silicate.
7. 7. The active composition according to one of the preceding claims, wherein the active composition contains a porous and/or thermally conductive additive.
8. 8. The active composition according to Claim 7, wherein the additive comprises carbon fibres, in particular bundled carbon fibres, charcoal and/or activated carbon.
9. 9. The active composition according to one of the preceding claims, wherein the combustion fuel comprises a metal, a semimetal, or a mixture or alloy of metals and/or semimetals or a mixture or alloy of at least one metal and at least one semimetal.
10. 10. The active composition according to one of the preceding claims, wherein the combustion fuel comprises aluminium, magnesium, titanium, zirconium, hafnium, calcium, lithium, niobium, tungsten, manganese, iron, nickel, cobalt, zinc, tin, lead, bismuth, tantalum, molybdenum, vanadium, boron, silicon, an alloy or mixture of at least two of these metals or semimetals, a zirconiumnickel alloy or mixture, an aluminium-magnesium alloy or mixture, a lithiumaluminium alloy or mixture, a calciumaluminium alloy or mixture, an irontitanium alloy or mixture, a zirconium-titanium alloy or mixture, or a lithiumsilicon alloy or mixture.
11. 11. The active composition according to any one of the preceding claims further comprising a binder.

    3430639v1

    2013206582 17 Nov 2017
12. 12. The active composition according to claim 11, wherein the binder is a fluoroelastomer.
13. 13. The active composition according to claim 11 or claim 12, wherein the binder is a fluororubber.
14. 14. The active composition according to one of the preceding claims, wherein the oxidant is a halogen-containing polymer.
15. 15. The active composition according to claim 14, wherein the halogenatedcontaining polymer is polytetrafluoroethylene (PTFE) or polychloroprene.
16. 16. The active composition according to one of the preceding claims further comprising a combustion catalyst.
17. 17. The active composition according to claim 16, wherein the combustion catalyst is ferrocene, iron acetylacetonate or copper phthalocyanine.

    3430639v1