RO135740B1 - Spectral pyrotechnical compositions for thermal countermeasures of flare type and process for preparing the same - Google Patents

Description

RO 135740 Β1

The invention refers to various pyrotechnic compositions intended for the realization of aerial thermal countermeasures of the FLARE type and a process for obtaining them, which present clearly superior advantages compared to the already existing compositions used worldwide.

FLARE thermal countermeasures are intended for both military and civilian aircraft, potential targets of terrorist attacks, against IR guided missiles. The missile's detection system identifies the aircraft's hot spot (the exhaust pipes at the tail of the aircraft) and heads for it. Countermeasures are launched automatically or manually by the pilot. Their ignition causes the appearance of a maximum of the radiant emission, the intensity of which can be an order of magnitude higher than the intensity of the thermal footprint of the aircraft. Separation of the FLARE from the launch pad must be very rapid so that the heat trap reaches maximum intensity before leaving the missile's field of view. After launch, the FLARE countermeasures leave the aircraft trajectory, following their ballistic trajectory. in addition, weight loss due to mass burning and aerodynamic braking decrease their speed. Due to the radiant emission of the FLARE, the missile's detection system changes its target, moving towards the heat trap and away from the aircraft.

There are many known pyrotechnic compositions intended for aerial countermeasures of the FLARE type [1-9], Spectrophotometric measurements showed that most of the compositions emit, during combustion, predominantly radiation in the a band (1.5-2.5 pm), radiation characteristic of the black body or gray, this being associated with high temperatures (over 1500 K) [10-12], Their main disadvantage is obtaining a spectral ratio θ _β/α = Ι _β/|α < 1 (Ι _α - radiation intensity in band a; Ι _β - the intensity of radiation in the β band), being easily identified as false targets by the latest generation thermo-guided missiles. In order to obtain a higher spectral ratio, those raw materials must be selected which, through combustion, lead to the emission of radiation in the β band (3.5-5 pm), The most important emitter in the β band is CO ₂ , having a factor of 10 times higher than CO and H ₂ O.

It is known from the article, C. Epure, T. Țigănescu, O. lorga, A. Marin, etc. "Fuel ratio and additives influence on the combustion parameters of new polyurethane-based flares", Mater. Flat. 57 (4), 2020,109-124, FLARE-type pyrotechnic compositions. The pyrotechnic formulations are made of a polymer matrix obtained by solvent-free crosslinking of a polyol based on castor oil - Sethatane D1150 with diphenylmethane diisocyanate - Desmodur VL in a ratio of 2:1 by weight. The oxidizer used is potassium perchlorate (purity 98%, average particle size 100 pm), Magnalium fuel (Al:Mg =1:1 alloy by weight, average particle size 63 pm) and powdered chlorinated rubber. The plasticizer is dioctyl phthalate (purity 98%) and the solvent is acetone (purity 98%). All the powder materials were sieved and dried for 24 h at 60°C. Potassium perchlorate was mortared together with liquid dioctyl phthalate. After 2 min of mixing, the fuel was gradually added while continuing to mix. in parallel, the liquid polyurethane binder was prepared, together with 2 g of acetone, mixing continuously for 10 min. The material obtained was pressed into molds and allowed to harden for 24 h at 40°C.

It is known from the article A. Elsaidy et al, "The Infrared Spectra of customlzed Magnesium/Teflon/Viton (MTV) Decoy Flares to Thermal Slgnature of Jet Engine", 17 ^th International Conference on Aerospace Science & Aviation technology, April 11-13, 2017 different pyrotechnic compositions of flares that are obtained from MTV materials. Materials used in the manufacture of the compositions include oxidizer which may be Teflon, metallic fuel and Viton type binders. Teflon can act as a binder and oxidizer; Viton A can act as a plasticizer and binder, in different concentrations. The procedure for obtaining a

RO 135740 Β1 of the compositions has the following steps: sieving solid particles to a fine powder smaller than 1 300 pm, size distribution of Mg and Teflon particles, mixing them with oxidizer, fuel and binder, then granulation to preserve the homogeneity of the composition, introduction 3 of the mixture obtained in a mold, the final product was made by applying a pressure of 200 atm. 5

It is known from S. Elbasuney et al. 2020, "Superior spectral performance of compositional decoy flares via inclusion of graphite as a black body emitter", IOP 7

Conference Series: Materials Science and Engineering, 975, 2020, a study of the spectral properties of pyrotechnic compositions. Graphite particles have been used together 9 with various reactive metal fuels, including Mg, Al, and Mg-Al alloy. Various metal powders were used as fuels, including Mg, Al and Mg-AI alloy, Teflon as oxidizer; 11 Viton A was used as a plasticizer, and graphite as an emitter, achieving different concentrations. The obtaining process was the following: sieving the solid particles to a fine powder, Teflon as an 13 oxidizer and the binder together with Viton A were dissolved in acetone, then granulation followed to ensure the homogeneity of the composition, and the final product was obtained by pressing in a 15 mold of aluminum.

The objective technical problem that the invention solves is to obtain 17 pyrotechnic compositions with improved mechanical properties with superior spectral ratios, thus improving the operational effectiveness of Fiare-type countermeasures. 19

The pyrotechnic composition intended for thermal countermeasures type ammunition removes the above disadvantages, in that it consists of:21

a. 35...55% oxidizer, potassium perchlorate with grain size < 90 pm;

b. 20...45% fuel, Mg-AI alloy, with grain size < 63 pm;23

c. 2...8% plasticizer, di-butyl-phthalate, di-octyl-phthalate, di-isooctyl-phthalate, di-isononyl-phthalate, dibutyl-maleate, di-isobutyl-maleate;25

d. 10...15% polyurethane binder, made up of:

i. polyol based on castor oil, without solvent;27 ii. aromatic polyisocyanate based on di-phenyl-methane-diisocyanate, solvent-free;

e. 2...8% halogenated binder, polytetrafluoroethylene powder -(C ₂ F ₄ ) _n -; fluorinated copolymer powder 29 of hexafluoropropene or tetrafluoroethylene with vinyl fluoride or vinylidene; chlorinated rubber powder with a degree of chlorination of 40...60% - monocomponent system; 31

f. 3...6% organic solvent, 99.5% purity acetone, the percentages being mass.

The requirements for a pyrotechnic composition to be used as an aerial thermal countermeasure 33 are:

- not to ignite inside the launcher on the aircraft; 35

- the sensitivity should be reduced, so that it cannot be initiated under the action of accidental external stimuli; 37

- to be launched at high speed;

- the ignition should be carried out a few seconds after launch; 39

- during combustion to develop temperatures above 1000°C;

- the burning speed should be high enough, so that it is effective for about 10 s; 41 - to be observable during combustion from at least 500 m, etc.

Pyrotechnic compositions are made up of the following raw materials: 43

- metallic fuels, which, through oxidation, release a large amount of energy: Al, Mg, etc. or their alloys; 45

- organic oxidants:

- oxygenated compounds: chlorates (KCIO ₃ ), perchlorates (KCIO ₄ ), etc.;47

- halogenated organic compounds: fluorinated (C ₂ F ₄ )n;

RO 135740 Β1

- synthetic binders with the role of maintaining the homogeneity of the composition and to cover and protect the particles of the component materials, especially metals, which can react with oxygen or moisture from the surrounding atmosphere.

These can be: polyester, epoxy, polyamide, polyurethane resins, polyvinyl chloride and derivatives, chlorinated rubber, thiocolic, etc. Sometimes organic compounds are used with a double role, of oxidant and binder: fluorinated compounds of the Teflon type (polytetrafluoroethylene -(C ₂ F ₄ ) _n -), Viton (fluoro-elastomer of the copolymer type of hexafluoropropene or tetrafluoroethylene with vinyl or vinylidene fluorides ).

Pyrotechnic compositions are made of the following raw materials:

- metallic fuels, which, through oxidation, release a large amount of energy: Al, Mg, etc. or alloys thereof;

- organic oxidants:

- oxygenated compounds: chlorates (KCIO ₃ ), perchlorates (KCIO ₄ ), etc.;

- halogenated organic compounds: iluoriated (C ₂ H ₄ ) _n ;

- synthetic binders with the role of maintaining the homogeneity of the composition and to cover and protect the particles of the component materials, especially metals, which can react with oxygen or moisture from the surrounding atmosphere. These can be: polyester, epoxy, polyamide, polyurethane resins, polyvinyl chloride and derivatives, chlorinated rubber, thiocolic, etc. Sometimes organic compounds are used with a double role, of oxidant and binder: fluorinated compounds of the Teflon type (polytetrafluoroethylene -(C ₂ F ₄ ) _n -), Viton (fluoro-elastomer of the copolymer type of hexafluoropropene or tetrafluoroethylene with vinyl or vinylidene fluorides ).

Compared to already existing compositions, these compositions present the following advantages:

- the polymer matrix formed gradually reticulates, generating pyrotechnic compositions with improved mechanical properties (tensile and compression resistance);

- pyrotechnic compositions are resistant to the action of external environmental and destructive factors (moisture, oxygen, UV radiation, chemical agents, thermal shocks, etc.), thanks to the protection provided by the polymer binder;

- the elasto-plastic behavior of the composition determines the low sensitivity to friction, electrostatic discharges or impact of pyrotechnic compositions;

- by facilitating total oxidation reactions during the combustion of pyrotechnic compositions, increased spectral ratios are obtained, thus improving the operational effectiveness of FLARE type countermeasures;

- the possibility of obtaining complex forms of the pyrotechnic material (rectangular, of different sizes, with textured surfaces), through simple, cheap, safe procedures.

An example of the invention is presented below:

Example

The potassium perchlorate is dried at 80°C for 24 h and then sieved through a sieve with a maximum mesh size of 300 µm.

A homogeneous mixture of metal powders, halogenated binder and plasticizer is prepared, on top of which potassium perchlorate is added and mixed gently. Add the acetone and the polyurethane binder, homogenizing in a mixer with chicane screws. The polyurethane binder is prepared separately by mixing the polyol with the polyisocyanate, a maximum of 15 min before addition.

RO 135740 Β1

Bibliography 1

[1], Koch E., Metal-Fluorocarbon Based Energetic Materials, Wiley-VCH Verlag 3 GmbH &Co., KgaA, 2012;

[2], Koch E. C., 2006-2008 Annual Review on Aerial Infrared Decoy Flares, 5 Propellants Explos. Pyrotech, 34, 2009, p. 6-12, doi:10.1002/prep.200700219;

[3], Li JS &all, Combustion Rate and LightEmission of Mg/NaNO ₃ /Na ₂ C ₂ O4/Binder 7 -Flares, Propellants Explos. Pyrotech., 43 (5), 2018, 1-11, doi: 10.1002/prep.201700257;

[4], Nielson D. B., D Lester M., Blackbody Decoy Fiare Compositions for Thrusted 9 Applications and Methods of Use, US Patent 5834680, Cordant Technologies Inc., USA, 1998;11

[5], CallawayJ., SutliefT., Infra-Red Emitting Decoy Animals, US2004/0011235 A1, GB, 2004;13

[6], Weiser V. & all, Pyroorganic Flares - A New Approach For Aircraft Protection, in proc. 9th International Congress of Pyrotechnics, Beaune France, 2007, p. 785;15

[7], Koch E.C., Metal-fluorocarbon pyrolants: VIII. Behavior of bubble rate and radiometric performance of two Magnesium/Teflon/Viton (MTV) formulations upon addition 17 of graphite, J. Pyrotech, 27 (38), 2008;

[8], Smit K.J., Hancox R.I, Hatt D.J., Murphy S.P., De Yong L.V., Infrared-Emitting 19 Species Identified in the Combustion of Boron-Based Pyrotechnic Compositions, Appl. Spectrosc, 51 (9), 1997, 1400-1404; 21

[9], Hawass A., Awad M., Binary Mixture Based on Epoxy for Spectrally Adapted Decoy Animals, Adv. J. Chem. A, 3(5), 2020, p. 692-700; 23

[10], Boulet P. & all, Experimental Investigation of Radiation Emitted Optically Thick

Wildland Flames, J. Comb., 2011, 1-8, doi: 10.1155/2011/137437;25

[11], LeeW., HanK, HahnJ. W., Direct Determination of EffectiveSpectral Emissivity of Hot Burat Gas using Absolutely Calibrated Radiometric Spectrometer, Propellants Explos. 27 Pyrotech., 42 (5), 2017, p. 1-9;

[12], Tanner J. E., Naval Ammunition Depot, Effect of binder oxygen content on 29 adiabatic flame temperature of pyrotechnic flares, Defense Technical Information Center, Virginia, 1972, p. 19.31

Claims (5)

RO 135740 Β1 demand 1. Pyrotechnic composition intended for thermal countermeasures ammunition, characterized by the fact that it consists of: a. 35...55% oxidizer, potassium perchlorate with grain size < 90 pm; b. 20...45% fuel, Mg-AI alloy, with grain size < 63 pm; c. 2...8% plasticizer, di-butyl-phthalate, di-octyl-phthalate, di-isooctyl-phthalate, di-isononyl-phthalate, di-butyl-maleate, di-isobutyl-maleate; d. 10...15% polyurethane binder, made up of: i. polyol based on castor oil, solvent-free; ii. aromatic polyisocyanate based on di-phenyl-methane-diisocyanate, solvent-free; e. 2...8% halogenated binder, polytetrafluoroethylene powder -(C ₂ F ₄ ) _n -; fluorinated copolymer powder of hexafluoropropene or tetrafluoroethylene with vinyl fluoride or vinylidene; chlorinated rubber powder with a degree of chlorination of 40...60% - monocomponent system; f. 3...6% organic solvent, 99.5% purity acetone, the percentages being mass. 2. Pyrotechnic composition according to claim 1, characterized in that, instead of Mg-AI alloy, Al powder with a grain size of 4...5 pm and plasticizer: di-2-ethyl-hexyl-phthalate, di-2 -ethyl-hexyl-adipate. 3. Pyrotechnic composition according to claim 1, characterized in that a mixture of Mg powder with a grain size < 63 µm and Al with a grain size of 4...5 µm is used, at a mixing ratio of 50...50% , with plasticizer: di-isodecyl-phthalate, di-isobutyl sebacate, and fluorinated binder with grain size < 60 pm. 4. Pyrotechnic composition according to claim 1, characterized in that, instead of Mg-AI alloy, Mg powder with a grain size < 63 pm, plasticizer di-isononyl phthalate, di-butyl-maleate, di-isobutyl-maleate, and fluorinated binder with grain size < 60 pm. 5. Process for obtaining the pyrotechnic compositions defined in claim 1, characterized in that it has the following steps: drying the potassium perchlorate at 80°C for 24 h and then sieving, through a mesh sieve with a maximum of 300 µm, the preparation to a homogeneous mixture of metal powders, halogenated binder and plasticizer, over which potassium perchlorate is added and light mixing, then addition of acetone and polyurethane binder, homogenization in a mixer with chicane screws, separation of the polyurethane binder separated by mixing the polyol with the polyisocyanate , with a maximum of 15 min before the addition, and finally pouring the homogeneous mixture into molds, where it is kept for 24 h. Editing and computerized techno-editing - OSIM Printed at the State Office for Inventions and Trademarks under order no. 352/2024