Ballistic modification is accomplished by incorporation oxides of lead and in in nitramine double-base propellants.
Combustion catalysts, in the form of organo-metallic and inorganic salts have been employed as ballistic modifiers to obtain the above ballistic effects in double base propellants of low, intermediate, and high energy for a considerable period of time. However, most efficient ballistic modification (stability of burning rate to variations in temperature and pressure) has been realized with double base systems of low to intermediate energy (Q, heat of explosion approximately 640 to 950 cal./gr.), which do not contain explosive crystalline filler, and double base systems of low energy (Q, heat of explosion approximately 600 to 800 cal./gr.) which contain nitramine (cyclotrimethylenetrinitramine, cyclotetramethylene tetra nitramine, etc.) energetic crystalline fillers. All efforts to modify the ballistics of high energy extruded and pourable propellants (Q, heat of explosion 950 cal./gr. and above) containing crystalline nitramines with organo-metallic and inorganic salts have produced systems with only minimal ballistic properties.
It is therefore an object of this invention to provide improved ballistic modification to a high energy nitramine double base propellant.
A further object of this invention is to provide a method of incorporation of the ballistic modifier into the high energy nitramine double base propellant.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description.
According to this invention improved ballistic modification is obtained by incorporation of a mixture of lead and tin oxides into a nitramine double base propellant.
DETAILED DESCRIPTION OF THE INVENTION
A preferred method of incorporating the oxides of tin and lead into a cross-linked or uncross-linked nitramine double base propellant is described below:
1. To casting solvent x, hereinafter described, add resorcinol (if required) and type B fluid ball powder, hereinafter described, and let stand overnight at 70.degree. F.
2. Add the resultant mixture to a vertical sigma blade mixer.
3. Add HMX (cyclotetramethylene tetranitramine), the selected modifier mixture of lead and tin oxides, quick gel (Type C) fluid ball powder, hereinafter described, and 2,4-tolylene diisocyanate (if required) with mixing between additions.
4. Mix for approximately two hours at about 25.degree. to 50.degree. C under a vacuum of 2-4 mm Hg.
5. Cast at a viscosity of approximately 30,000 cps and cure at 60.degree. C for three days.
The fluid ball powders, trademark products of Olin Mathieson Chemical Corporation, having an average particle size of about 7 microns, have the following compositions:
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% Composition Type B Type C
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Nitrocellulose, 12.6% N
90.0 74.0
Nitroglycerin 8.0 24.0
2-Nitrodiphenylamine
2.0 2.0
Dioctylphthalate, added
0.2 0.1
Carbon Black, added
0.01 - 0.03 --
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The composition of casting solvent x is as follows:
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Composition % by Weight
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Triethylene glycol dinitrate
65.0
Butanetriol trinitrate
34.0
2-Nitrodiphenylamine 1.0
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The composition of a typical nitramine double base propellant as prepared above is:
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Composition % by Weight
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Fluid Ball Powder B 18.5
Fluid Ball Powder C 1.0
Casting Solvent "x" 46.5
HMX 30.0
Modifier 4.0
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The resorcinol and 2,4-tolylene diisocyanate are added to the above formulation when cross-linking of the propellant is desired.
Burning rate data for nitramine double base propellants containing various mixtures of lead and tin oxides and 0 to 50% HMX are given in the following table:
TABLE I
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Fluid Ball Powder B
27.4
25.9
24.4
23.0
21.6
20.0
18.5
17.2
16.6 15.1 13.6
Fluid Ball Powder C
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 -- -- --
Casting Solvent "x"
67.6
64.1
60.6
57.0
53.4
50.0
46.5
42.8
39.4 35.9 32.4
HMX 0.0 5.0 10.0
15.0
20.0
25.0
30.0
35.0
40.0 45.0 50.0
Modifier 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
30/70 PbO/SnO.sub.2 :
Burning Rate, in/sec
0.36
0.33
0.41
0.41
0.42
0.40
0.40
0.37
0.34 0.33 0.31
70.degree. F, 1000 psi
Slope, "n" 0.38
0.53
0.25
0.18
0.06
0.14
0.11
0.23
0.26 0.24 0.27
.pi..sub.p/r, % /.degree. F, 160.degree. F to -40.degree. F
0.33
0.58
0.44
0.27
0.15
0.15
0.11
0.15
0.10 0.08 0.10
30/70 PbO.sub.2 /SnO.sub.2 :
Burning Rate, in/sec
0.38
0.41
0.40
0.36
0.43
0.41
0.38
0.38
0.34 0.31 0.29
70.degree. F, 1000 psi
Slope "n" 0.40
0.46
0.20
0.15
0.04
0.00
0.15
0.09
0.06 0.06 0.12
.pi..sub.p/r, % /.degree. F, 160.degree. F to -40.degree. F
0.35
0.41
0.25
0.23
0.17
0.11
0.15
0.10
0.045
0.025
0.00
30/70 Pb.sub.2 O.sub.3 /SnO.sub.2 :
Burning Rate, in/sec
0.36
0.39
0.33
0.36
0.41
0.40
0.40
0.38
0.36 0.32 0.30
70.degree. F, 1000 psi
Slope "n" 0.49
0.40
-- 0.28
0.19
0.11
0.06
0.10
0.10 0.11 0.08
.pi..sub.p/r, % /.degree. F, 160.degree. F to -40.degree. F
0.46
0.42
0.27
0.30
0.17
0.12
0.08
0.05
0.04 0.025
0.00
30/70 Pb.sub.3 O.sub.4 /SnO.sub.2 :
Burning Rate, in/sec
0.35
0.36
0.37
0.35
0.36
0.36
0.34
0.32
0.34 0.31 0.29
70.degree. F, 1000 psi
Slope "n" 0.51
0.49
0.36
0.36
0.29
0.26
0.20
0.24
0.24 0.26 0.29
.pi..sub.p/r, % /.degree. F, 160.degree. F to -40.degree. F
0.43
0.38
0.27
0.26
0.20
0.16
0.08
0.10
0.10 0.06 0.065
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It is readily apparent from the above Table that as the percentage of crystalline filler (in this case, HMX) is increased in the propellant composition the n or slope of the burning rate isotherm decreases along with the temperature coefficient (.pi..sub.p/r, %/.degree. F). Thusly a more ballistically stable, reliable high energy propellant is produced.
FIGS. 1-12 represent the burning rate pressure .times. 100 (psi) curves of a high energy nitramine (30% HMX) double base propellant incorporating mixtures of four different oxides of lead and stannic oxide in various ratios. The following table is an interpretation of the curves in the above figures.
TABLE II
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Ratio-Oxide of Lead/Stannic Oxide
"n" Value
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FIG. 1:
1. 100/0 PbO/SnO.sub.2
0.75
2. 90/10 PbO/SnO.sub.2
0.68
3. 80/20 PbO/SnO.sub.2
0.60
4. 70/30 PbO/SnO.sub.2
0.53
5. 60/40 PbO/SnO.sub.2
0.38
FIG. 2:
6. 50/50 PbO/SnO.sub.2
0.12
7. 40/60 PbO/SnO.sub.2
0.04
8. 30/70 PbO/SnO.sub.2
0.02
9. 20/80 PbO/SnO.sub.2
0.09
FIG. 3:
10. 10/90 PbO/SnO.sub.2
0.25
11. 0/100 PbO/SnO.sub.2
0.93
FIG. 4:
1. 100/0 PbO.sub.2 /SnO.sub.2
0.87
2. 90/10 PbO.sub.2 /Sn0 2
0.68
3. 80/20 PbO.sub.2 /SnO.sub.2
0.62
4. 70/30 pbo.sub.2 /Sno.sub.2
0.74
5. 60/40 PbO.sub.2 /SnO.sub.2
0.64
FIG. 5:
6. 50/50 PbO.sub.2 /SnO.sub.2
0.55
7. 40/60 PbO.sub.2 /SnO.sub.2
0.09
8. 30/70 PbO.sub.2 /SnO.sub.2
0.06
9. 20/80 PbO.sub.2 /SnO.sub.2
0.055
FIG. 6:
10. 10/90 PbO.sub.2 /SnO.sub.2
0.47
11. 0/100 PbO.sub.2 /SnO.sub.2
0.93
FIG. 7:
1. 100/0 Pb.sub.2 O.sub.3 /SnO.sub.2
0.92
2. 90/10 Pb.sub.2 O.sub.3 /SnO.sub.2
0.90
3. 80/20 Pb.sub.2 O.sub.3 /SnO.sub. 2
0.80
4. 70/30 Pb.sub.2 O.sub.3 /SnO.sub.2
0.69
5. 60/40 Pb.sub.2 O.sub.3 /SnO.sub.2
0.50
FIG. 8:
6. 50/50 Pb.sub.2 O.sub.3 /SnO.sub.2
0.15
7. 40/60 Pb.sub.2 O.sub.3 /SnO.sub.2
0.11
8. 30/70 Pb.sub.2 O.sub.3 /SnO.sub.2
0.12
9. 20/80 Pb.sub.2 O.sub.3 /SnO.sub.2
0.12
FIG. 9:
10. 10/90 Pb.sub.2 O.sub.3 /SnO.sub.2
0.42
11. 0/100 Pb.sub.2 O.sub.3 /SnO.sub.2
0.93
FIG. 10:
1. 100/0 Pb.sub.3 O.sub.4 /SnO.sub.2
0.84
2. 90/10 Pb.sub.3 O.sub.4 /SnO.sub.2
0.85
3. 80/20 Pb.sub.3 O.sub.4 /SnO.sub.2
0.94
4. 70/30 Pb.sub.3 O.sub.4 /SnO.sub.2
0.66
5. 60/40 Pb.sub.3 O.sub.4 /SnO.sub.2
0.55
FIG. 11:
6. 50/50 Pb.sub.3 O.sub.4 /SnO.sub.2
0.49
7. 40/60 Pb.sub.3 O.sub.4 /SnO.sub.2
0.29
8. 30/70 Pb.sub.3 O.sub.4 /SnO.sub.2
0.28
9. 20/80 Pb.sub.3 O.sub.4 /SnO.sub.2
0.32
FIG. 12:
10. 10/90 Pb.sub.3 O.sub.4 /SnO.sub.2
0.46
11. 0/100 Pb.sub.3 O.sub.4 /SnO.sub.2
0.93
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From these burning rate curves and n values it is apparent that as the concentration of the selected oxide of lead decreased in the lead oxide/tin oxide modifier employed, the propellant burning rate increased and the pressure exponent (n) decreased, that is, the propellant burning rate became less dependent to variations in pressure. Optimum modifying activity in the propellants is effected with mixtures of selected oxides of lead and stannic oxide in ratios ranging from 20/80 to 50/50 oxide of lead/oxide of tin. In general, however, modifying activity takes place from 90/10 to 10/90 oxide of lead/oxide of tin.
The percentage of modifier added to the propellant composition may be varied from about 1 to 5% by weight with optimum modification occurring when about 4% modifier is added.
High energy nitramine propellants which may be modified according to this invention include any double base propellant which incorporates a high energy crystalline filler such as tetryl (2,4,6-trinitrophenyl methyl nitramine), haleite (ethylene dinitramine), RDX (cyclotrimethylenetrinitramine), HMX (cyclotetramethylene tetranitramine) and diethanol nitramine dinitrate in amounts ranging from 10 - 50% of the propellant compositions.
Thusly through the practice of my invention, ballistic modification of high energy nitramine propellants may be obtained such that reliability of performance is increased.
I wish it to be understood that I do not desire to be limited to the exact detail of construction shown and described, for obvious modification will occur to a person skilled in the art.
