EP0816306B1 - Propellants with a high specific impulsion, containing furazane derivatives - Google Patents

Description

The present invention relates to the field of solid propellants with high specific impulse and / or strong volume impulse. The specific impulse is the thrust developed per unit of flow-weight of the products combustion. The volume pulse is the product of the specific impulse by the density of the solid propellant.

The solid propellants concerned belong to the families of composite propellants or propellants modified double base, they include in particular a binder inert or energetic, at least one energetic charge and possibly conventional additives.

The present invention relates more particularly such solid propellants very discrete called "clean", that is to say, those not containing no constituents whose combustion gives halogenated products or liquid or solid products giving a visible or infrared "signature" important. Ammonium perchlorate whose combustion produces hydrochloric gas and aluminum in particular whose combustion produces alumina are examples of such constituents.

However, propellants containing such constituents which will therefore slightly degrade the propellant discretion, are also part of the invention.

Currently the so-called "clean" propellants have for oxidative or energetic charge essentially of ammonium nitrate, but the specific impulse remains low, more other problems are related to the use of ammonium nitrate. Another type of energy charge, nitramines such as octogen (HMX) or hexogen (RDX) give a boost higher specific but you still have to add aluminum to get impulses important.

The purpose of the present invention is to provide solid propellants, essentially "clean", and strong specific and / or volume impulses.

The present invention relates to solid propellants, with a high specific and / or volume impulse, comprising in particular a binder, at least one energy charge and various additives, characterized in that the energy charge is essentially chosen from the group of dinitrated bifurazanes constituted by 3,3'-azoxybis [4 nitrofurazane] (C ₄ N ₈ O ₇ ), 3,3'-azobis [4 nitrofurazane] (C ₄ N ₈ O ₆ ), 3,3'-bis [4 nitrofurazane] (C ₄ N ₆ O ₆ ).

The solid propellant binder is of the binder type inert or energy binding. The essential charge is chosen from the aforementioned group. It can include also, for various reasons, other charges used moreover, such as nitramines for example. The various additives mentioned here are those conventionally used by those skilled in the art for improve for example chemical stability, kinetics of combustion, mechanical properties, etc ... These additives represent only a few for hundred, by weight, of the propellant.

Advantageously for solid propellants whose binder is of the energy type, the energy charge in dinitrated bifurazane represents at least 55% by weight of the propellant.

The energy binders of the present invention are obtained with oxetane or oxirane polymers substituted, nitraminated or nitrated polymers, polyethers, polyesters. These polymers being possibly plasticized by inert plasticizers or themselves energetic such as in particular oils nitrated.

Advantageously also for solid propellants whose binder is of the energy type, the charge energy in dinitrated bifurazane represents at least 75% by weight of the propellant.

In a particular embodiment of the invention, the energy type binder is based on polymer with pendant chains with azide endings such as for example a glycidyl polyazide (PAG), a polybisazidomethyl oxetane (BAMO), the polyazide of glycidyl being the preferred polymer.

Advantageously for solid propellants whose binder is of inert type the energy load in dinitrated bifurazane represents at least 70% by weight of the propellant.

The inert binders of the present invention are especially those obtained from polybutadian carboxy-telechelic or hydroxytelechelic, optionally grafted.

Advantageously for solid propellants according to the invention when the binder is of inert type the energy load in dinitrated bifurazane represents minus 80% by weight of the propellant.

Possibly solid propellants according to the invention also comprise up to 10% by weight of a powdery metallic filler, such as aluminum, to further increase its specific impulse and by elsewhere remove any instabilities of combustion. However, a metallic charge introduced in such a proportion degrades the discretion of the propellant.

• pour le 3,3'-azoxybis [4 nitrofurazane] (C₄N₈O₇), dans Heteroatom Chemistry - Vol.5 No.5/6 - page 444 (1994), La formule développée de ce composé est :
  
• pour le 3,3'-azobis [4 nitrofurazane] (C₄N₈O₆), dans Journal of Organic Chemistry Vol. 61 pages 1510 à 1511 (1996), La formule développée de ce composé est :
  
• pour le 3,3'bis [4 nitrofurazane] (C₄N₆O₆) dans J. of Heterocyclic Chemistry - Vol.5 - page 83 - (1968), La formule développé de ce composé est :
  

The synthesis of dinitrated bifurazanes used in the present invention is described in the literature:

• for 3,3'-azoxybis [4 nitrofurazane] (C ₄ N ₈ O ₇ ), in Heteroatom Chemistry - Vol.5 No.5 / 6 - page 444 (1994), The structural formula of this compound is:
  
• for 3,3'-azobis [4 nitrofurazane] (C ₄ N ₈ O ₆ ), in Journal of Organic Chemistry Vol. 61 pages 1510 to 1511 (1996), The structural formula of this compound is:
  
• for 3,3'bis [4 nitrofurazane] (C ₄ N ₆ O ₆ ) in J. of Heterocyclic Chemistry - Vol.5 - page 83 - (1968), The developed formula of this compound is:
  

The propellants are produced according to the techniques usual in their family; basically mixing-casting techniques or kneading extrusion.

For various propellants according to the invention, the following examples give the performances: specific pulse and volume pulse. The specific impulse is determined under standard conditions: equilibrium relaxation and relaxation ratio 70/1. The specific pulse is designated by Is, it is expressed in seconds. The volume pulse is the product of the specific pulse by the propellant density: it is designated by p.Is and it is expressed in sgcm ^-3 .

Example 1

This example relates to propellants whose binder, of energy type, is based on glycidyl polyazide (PAG) 24% by weight, crosslinked with 6% of trimer of hexamethylene diisocyanate, the binder is highly plasticized, 66%, with a mixture of trimethylol ethane trinitrate and butanetriol trinitrate in the proportions 70/30, the complement comprising various additives (antioxidants, ...). The energy charge is 3,3'-azoxybis [4 nitrofurazane]; for the reference propellant the energy load is octogen (HMX).
Table 1 gives the results.

At a charge rate equal to or higher than that of the reference propellant, the propellant according to the invention has a specific pulse and a volume pulse superior. The energy charge rate can be decreased to around 55% while still retaining a higher specific impulse, on the other hand the impulse volume tends to decrease. The energy charge rate may be 15% less than that of the propellant of reference while having a specific impulse and a volume pulse at least equal.

Example 2

This example always relates to propellants with an energy-type binder; the binder, called G, is produced from a polyester: 20% by weight of diethylene glycol polyadipate crosslinked by 4% of trimer of diisocyante hexamethylene, plasticized with 71% of a mixture of nitroglycerin and butanetriol trinitrate in the 80/20 proportions, the complement comprising various feasibility and stability additives. These propellants, except one, additionally contain various additives in small quantities. The reference propellant is loaded with octogen and additives. Table 2 gives the results, [A] corresponding to the designation [4 nitrofurazane].

Specific impulses and impulses volumes of the propellants according to the invention are significantly higher than those of the propellant of reference.

Example 3

This example relates to composite propellants with an inert binder; it is a binder based on 70% by weight of hydroxytelechelic polybutadiene (PBHT, type R45M) crosslinked with 6.5% methylene cyclohexyl diisocyanate all plasticized with 23% dioctyl azelaate. The reference propellant has an 85% octogen charge. Table 3 gives the results obtained. Binder Energy charge Is (s) ρ Is sg cm ^-3 15% PBHT 85% HMX 130 380 30% PBHT 70% 3,3'-azoxybis [4 nitrofurazane] 234 340 20% PBHT 80% 3,3'-azoxybis [4 nitrofurazane] 250 390 15% PBHT 85% 3,3'-axozybis [4 nitrofurazane] 260 430 15% PBHT 85% 3,3'-azobis [4 nitrofurazane] 254 387 15% PBHT 85% 3.3 'bis [4 nitrofurazane] 259 426 10% PBHT 90% 3,3'-azoxybis [4 nitrofurazane] 274 470

For the same charge rate, the different dinitrated bifurazans give propellants including the specific impulse is considerably higher, from 20 to 30s, to that of the reference propellant. It the same is true for the volume pulse. The rate of energy charge can be reduced up to around 75% retaining high specific impulses and comparable volume pulses.

Example 4

The examples below relate to aluminized propellants whose binder is of the energy type based on a glycidyl polyazide (PAG), identical to that of Example 1; the energy charge of the reference propellant is octogen (HMX). Table 4 gives the results obtained, [A] corresponding to the designation [4 nitrofurazafne]. Binder PAG% Energy charge aluminum (%) Is (s) ρIs sg cm ^-3 25% PAG 65% HMX 10% 270 485 25% PAG 65% 3,3'-azoxybis [A] 10% 281 505 25% PAG 70% 3,3'-azoxybis [A] 5% 280 500 15% PAG 80% 3,3'-azoxybis [A] 5% 282 515 20% PAG 70% 3,3'-azoxybis [A] 10% 282 512 15% PAG 75% 3,3'-azoxybis [A] 10% 282 525

The addition of aluminum, to the propellants according to the invention (see also Table 1), to the detriment of the energy charge improves or at least maintains the performance, in particular the volume impulse. performances are clearly superior to those of propellant with the same aluminum charge rate but of which the energy charge is octogen. The addition aluminum, if it degrades the discretion of the propellant may be necessary to remove any combustion instabilities for example.

Claims (9)

1. Solid propergol with a high specific impulse comprising in particular a binder, at least one energetic charge and various additives, characterized in that the energetic charge is substantially selected from the group of dinitrated bifurazanes consisting of 3,3'-azoxybis [4 nitrofurazane] (C₄N₈O₇), 3,3'-azobis [4 nitrofurazane] (C₄N₈O₆) and 3,3' bis [4 nitrofurazane] (C₄N₆O₆).
2. Solid propergol according to claim 1, characterized in that the binder is an energetic binder and that the energetic charge of dinitrated bifurazane represents at least 55 % of the weight of the propergol.
3. Solid propergol according to claim 2, characterized in that the energetic charge of dinitrated bifurazane represents at least 75 % by weight of the propergol.
4. Solid propergol according to claim 2 or 3 characterized in that the energetic binder is based on a polyether or a polyester plasticised by at least one nitrated oil.
5. Solid propergol according to claim 2 or 3, characterized in that the energetic binder is based on a polymer with pendant chains having azide endings.
6. Solid propergol according to claim 2 or 3, characterized in that it also includes up to 10 % by weight of a powdered metallic fuel.
7. Solid propergol according to claim 1, characterized in that the binder is an inert binder and that the energetic charge of dinitrated bifurazane represents at least 70 % of the weight of the propergol.
8. Solid propergol according to claim 7, characterized in that the energetic charge of dinitrated bifurazane represents at least 80 % by weight of the propergol.
9. Solid propergol according to claim 7 or 8 characterized in that it also includes up to 10 % by weight of a powdered metallic fuel.