DE2644211B2 - Composite solid propellant - Google Patents

Description

The present invention relates to composite solid propellants with stable burn-off from ammonium perchlorate, polymeric binder, hardener, plasticizer and burn-up moderators.

Solid propellants as energy suppliers are becoming more and more as the rocket technology continues to develop more important. A significant disadvantage of the known composite fuels based on ammonium perchlorate are the hydrochloric acid or hydrogen chloride gases produced during combustion. These combustion products not only lead to corrosive phenomena on metal parts in the area of the exhaust gases lie, such as B. launchers, vehicles, but also lead to physiological stress and damage Operating personnel and people who get caught in the clouds of exhaust gases carried by the wind. The possible uses of composite solid propellants could be expanded significantly if the Hydrochloric acid or hydrogen chloride emission in the exhaust gas could be achieved.

The choice of a fuel is determined by performance, safety, life and cost factors. The performance factors include momentum, density, thermal expansion properties, mechanical Properties, rate of burn and erosion ability. The safety factors are both Manufacturing and processing aspects as well as handling and bullet safety of the finished Device to be taken into account. If a device is produced in large numbers, such as B. for artillery missiles, material costs are of particular importance. The fuel types proposed so far can eo do not satisfactorily meet one or more of the above factors.

Therefore, it is an object of the invention to provide a composite solid propellant to create whose exhaust gases are essentially free of corrosive and toxic substances. Another object of the invention is to provide a fuel taking the above into account Factors such as high performance, safety, service life and low cost. This goal will according to the invention achieved in that at least one alkali and / or alkaline earth nitrate as a further oxidation salt is present and the binder is made from telomeric polybutadienes or copolymers of butadiene and Acrylonitrile with functional groups consists.

Examples of the further oxidation salt are lithium, sodium and potassium nitrate as polymer Binders are those with functional groups, either terminally or randomly can be distributed along the chain. Typical examples are carboxyl-terminated polybutadienes, hydroxyl-terminated ones Polybutadienes or copolymers. e of butadiene / acrylic acid (PBAA) and terpolymers of Butadiene / Acrylic Acid / Acrylonitrile (PBAN).

Of particular importance for the combustion products of composite fuels with mixed oxidizers is the mixing ratio. To avoid corrosive and toxic exhaust gases, the Oxidators used in a nearly stoichiometric ratio d. H. when using 1 mole of ammonium perchlorate at least 1 mole of alkali nitrate must be added. According to a preferred embodiment of the invention, the ratio is Equivalent weights of perchlorate to nitrate 1: 1 to 1: 1.2, preferably 1: 1 to 1: 1.05. The oxidizers can ground and / or unground are used.

If the functional group of the binder consists of a carboxyl group, these polymers can with the different aziridines, epoxides or amines. Polymers with hydroxyl groups are cured with aromatic or aliphatic di- or polyisocyanates. Depending on the reactivity of the Curing accelerators or curing inhibitors are added to the isocyanate used.

The binder system can of course also be modified by components that are not directly on the Hardening process are involved, such as aliphatic or aromatic hydrocarbons and esters with a plasticizer function, Process aids, antioxidants, etc.

In a further embodiment of the invention, the fuel contains one or more to increase performance Light metals and / or their alloys in finely divided form in amounts of 0 to 25% by weight, preferably 16 to 20% by weight. Suitable light metals are, for. B. aluminum, magnesium, beryllium. Instead of the light metals or, in addition, a semi-metal, such as. B. boron can be used.

The light metal or metals or their alloys have a grain size of 5 to 30 μm, preferably 5 to 15 μίτι, on.

The fuel composition has the following basic formula:

60 to 90% oxidizer mixture,

0 to 25% metal addition,

10 to 20% binder,

0 to 5% burn moderators.

To check the proposed concept, thermodynamic calculations were carried out with the help of the NASA program. Two recipes were calculated, which differ mainly in the molar ratio of ammonium perchlorate to sodium nitrate. In the first formulation, a molar ratio of NH ₄ CIO ₄ ZNaNO ₃ = 1: 1 was used; from Table I it can be seen that the formation of HCl is only 1.44% by weight at an expansion of 69/1 bar or 0.964

Wt .-% HC! at a relaxation of 130/1 bar

Table I.

Thermodynamic calculations at a Nr ^ CKVNaNCb molar ratio of 1: 1

AJAd

Ivak Up

bar
bar
K
K

m / s
m / s
m / s

69.083

1,000

3398

2191

36.648

1.161

10.769

1395.4

2504.5

2286.7

130,000

1,000

3442

2023

36.853

1.1629

17,549

1399.0

2606.5

2418.2

IO

Main combustion products in mole fractions

Al ₂ O ₃ (in the solid state) 0.09437 0.09464

CO 0.28765 0.28691

CO ₃ 0.01196 0.01355

HCl 0.00571 0.00268

H ₂ 0.34393 0.34818

H ₂ O 0.06287 0.06161

N ₂ 0.09449 0.09473

NaCl 0.08395 0.08530

Main combustion products in mole fractions

Al ₂ O ₃ (in the solid state) 0.10893 0.10929

CO 0.34053 0.34042

CO ₂ 0.01527 0.01657

HCl 0.01298 0.00868

H ₂ 0.24514 0.25005

H ₂ O 0.05688 0.05605

N ₂ 0.10799 0.10833

NaCl 0.09220 0.09701

15th

20th

25th

30th

Table H shows the thermodynamic calculations of a fuel _{formulation with a molar ratio NH 4} CIO / NaNO ₃ of 1: 1.05, it can be seen that the HCl concentration in the exhaust gases could be reduced even further.

Table II

Thermodynamic calculations with an NH ₄ ClO ₄ / NaNO3 molar ratio of 1: 1.05

45

50

55

Ρκ bar 69.083 130,000 P ' bar 1,000 1,000 Tk K 3203 3237 T ₈ K 1965 1792 M. 31,331 31,440 y 1.1759 1.1823 10,347 16.740 C * m / s 1457.2 1460.3 hook m / s 2608.5 2709.5 Isp m / s 2389.7 2521.2

Explanation of terms for Tables I and II

Pk combustion chamber pressure (K = chamber)

P _a pressure after relaxation (a = exit)

Tk flame temperature in the combustion chamber

T ₈ flame temperature after relaxation

SJ Average molecular weight of the combustion products

γ ratio of the spec. Heat at p = const, resp.

b0

Cp / CV

Area ratio of the nozzle cross-section to the narrowest nozzle shark cross-section

(a = exit, D = nozzle shark cross section) c * Characteristic speed

Ivak spec. Momentum in vacuum
Isp spec. Impulse upon relaxation to I bar The following exemplary embodiments serve to further clarify the invention.

example 1

29.387% NaNO ₃

40.613% ammonium perchlorate 16.000% aluminum-magnesium (10:90) 9.018% carboxyl terminated polybutadiene, 4.508% dioctyl sebacate

0.474% epoxy / aziridine hardener

The components are ^{mixed at 70 °} C. to form a pourable mass which, after 10 days at 80 ^° C., has hardened to form a rubber-elastic mass. The burning rate at 20 ^° C. and 120 bar is 7.0 mm / s.

Example 2

27.875% sodium nitrate
38.525% ammonium perchlorate 18.000% aluminum

9.944% carboxyl terminated polybutadiene, 3.508% isodecyl pelargonate

0.548% epoxy / aziridine hardener 1.600% burn moderator

Processing takes place as in Example 1, and a rubber-elastic composite fuel is obtained with a burning rate at 20 ^° C. and 120 bar of 10.8 mm / s. The pressure exponent over the pressure range from 70 to 250 bar is 0.36.

Example 3

27.708% sodium nitrate
38.292% ammonium perchlorate 20.000% magnesium

9.018% carboxyl terminated polybutadiene, 4.508% dioctyl sebacate

0.474% epoxy / aziridine hardener

The burn rate of the fuel is 7.0 mm / s at 20 ° C and 120 bar.

Example 4

28.422% sodium nitrate
39.278% ammonium perchlorate 18.000% aluminum

7.961% hydroxyl terminated polybutadiene, 4.402% plasticizer

1.637% diisocyanate

0.300% copper chromite

The components are mixed in suitable mixers at 40 ^° C. and result in a pourable mass which, after 12 days at 50 ^° C., has hardened to form a rubber-elastic mass. The burning rate at 20 ° C and 120 bar is 9.0 mm / s.

Example 5

28.664% sodium nitrate

37.736% ammonium perchlorate

18,000% aluminum

8.874% hydroxyl terminated polybutadiene

3.503% plasticizer

1.723% diisocyanate

1,500% burn moderator

The processing of the fuel is carried out as in Example 4. The burn rate at 20 ° C and 120 bar is 10.5 mm / s and the pressure exponent is 0.37.

Example 6

27.301% calcium nitrate

39.099% ammonium perchlorate

18,000% aluminum

8.874% hydroxyl terminated polybutadiene

3.503% plasticizer

1.723% diisocyanate

1,500% burn moderator

To clarify the quality and handling safety of the proposed fuels are given in Table III for their mechanical properties and in Table IV shows their safety values.

Table III

Mechanical properties of CTPB or HTPB solid propellants

2) -40X (σ / ε) « (σ / ε) _β + 20 ° C. (ole) R (ο / ε) β + 50X (σ / ε) « (Olf) B density E ₀ 2.26 / 67 2.35 / 51 Eo 0.70 / 82 0.74 / 65 Eo 0.54 / 87 0.55 / 72 g / cm ³ CTPB-FTS 4) 13.9 1.86 1.28 1,798 (according to the example 1.47 / 80 1.67 / 50 0.54 / 67 0.57 / 61 0.45 / 64 0.46 / 58 HTPB-FTS 5.59 1.37 1.08 1,800 (according to the example

Explanation:

CTPB = carboxyl-terminated polybutadiene.

HTPB = hydroxyl terminated polybutadiene.

FTS = solid rocket propellant.

Eo = modulus of elasticity in N / mm ² at 0% elongation.

ο = tensile strength R at break in N / mm ² .

ε = elongation B at maximum tensile strength in%

Table IV

Safety values of CTPB or HTPB solid propellants (on three tests each)

Sensitivity to friction 4 kg 6 kg

8 kg impact sensitivity

24.5 J 29.4 J 36.8 J

39.2

49.0]

CTPB-FTS
(according to example 2)
HTPB-FTS
(according to example 4)
Comparison AGVs *) none

reaction

no reaction no reaction

Crackle

Crackle no reaction Crackle no reaction

no explo-

Reaction sion

explosion

explosion

·) Consists of 66.4% ammonium perchlorate, 9.9% carboxyl-terminated polybutadiene, 18.0% aluminum. 3.5% plasticizer, 0.5% hardener and 1.6% combustion moderator.

The mechanical properties in Table III represent values for fuels as in the examples are described, represent; You can of course in wide areas, according to the respective requirements, can be varied.

The composite fuels on which the invention is based have been used in engines of various sizes burned down. In addition to the proof of a stable burn and the erosibility of the fuel was able to use various analytical methods, such as infrared spectroscopy (I R), nuclear magnetic resonance spectroscopy (NMR) and wet chemical analysis, no hydrochloric acid or hydrogen chloride gas can be found.

Claims (4)

Patent claims: 1. Composite solid propellant with stable combustion made of ammonium perchlorate, polymer! Binder, hardener, Plasticizers and burn moderators, characterized in that as a further Oxidation salt at least one alkali and / or alkaline earth nitrate is present and the binder is off telomeric polybutadienes or copolymers of butadiene and acrylonitrile and functional groups consists. 2. composite solid propellant according to claim 1, characterized in that the ratio of Equivalent weights of perchlorate to nitrate are 1: 1 to 1: 1.2, preferably 1: 1 to 1: 1.05. 3. composite solid propellant according to claim 1 and 2, characterized in that one or more Light metals and / or their alloys in finely divided form in amounts of 0 to 25% by weight, preferably from 16 to 20% by weight, are present. 4. composite solid propellant according to claims 1 to 3, characterized in that the or the light metals and / or their alloys have a grain size of 5 to 30 μm, preferably 5 to 15 μπι have.