Composite propellants containing copper compounds as ballistic modifiers

A composite propellant composition consisting essentially of ammonium perchlorate as an oxidizer, a carboxy-terminated polybutadiene binder, ammonium sulfate as a cooling agent, and a small proporation of at least one copper compound which functions as a ballistic modifier to lower the pressure exponent of the propellant over a useful pressure range for combustion of the propellant in a gas generator or other device. The copper compounds also lower the .pi..sub.k value of the composition, particularly at pressures exceeding 3000 psi (about 2000 N/cm.sup.2). Specifically exemplified copper compounds are copper chromite, copper phthalocyanine, and copper stearate.

Technical Field 
The present invention relates to composite propellants which have a low 
combustion temperature, particularly propellants designed for use in gas 
generators. 
Background Art 
A gas generator rapidly generates gas under pressure by burning a 
propellant. Gas generators are used for inflating life rafts, automotive 
airbags, and other structures, for propelling rockets out of their 
canisters, and for other purposes. 
Some relevant design criteria for gas generator propellants are as follows. 
First, the propellant combustion temperature must be low, for example 
below about 2000.degree. F. (1100.degree. C.), to avoid overheating the 
apparatus which is inflated or pressurized by the gas generator. Second, 
the burning rate of the propellant should not vary substantially with 
variations of pressure over the pressure range in which the gas generator 
will operate. The variation of burning rate with pressure is commonly 
expressed by a burning rate equation as follows: 
r = ap.sup.n wherein "r" represents the burning rate, "a" is a variable 
which depends on the initial grain temperature, "p" is the pressure in the 
combustion chamber, and "n" is the pressure exponent. It is very important 
that "n" be as close as possible to zero over the range of pressures for 
which the gas generator is designed. If "n" is positive, the burn rate 
will be unstable because a rise in pressure will increase the burn rate, 
which will in turn increase the pressure. If this positive feedback is 
substantial, the rocket will overpressurize and may explode. One problem 
in the art has been that if a gas generator having a relatively high 
operating pressure range is desired, it is difficult to provide a 
propellant which has a zero pressure exponent over the entire operating 
pressure range, including a safety margin above the intended operating 
pressure. 
Another design criterion of gas generator propellants is that the 
combustion pressure should vary as little as possible with the temperature 
of the propellant composition just before combustion begins. The variation 
in burning pressure resulting from variations in initial propellant 
temperature is indicated by the parameter .pi..sub.k. .pi..sub.k is 
calculated according to the following equation: 
##EQU1## 
wherein P is pressure during combustion, T is temperature just prior to 
combustion, the subscript "1" indicates a first temperature and resulting 
pressure, and the subscript "2" indicates a second temperature and 
resulting pressure. A propellant with a small value of .pi..sub.k will 
provide consistent performance over a wider ambient temperature range than 
would a propellant with a larger value of .pi..sub.k. 
Ballistic modifiers are propellant ingredients which lower the pressure 
exponent of a propellant over a certain range of combustion pressures. 
Ideally, a ballistic modifier would make the pressure exponent zero at all 
pressures likely to be encountered in the combustion chamber, thus 
providing an absolutely constant burn rate. However, in the real world, a 
pressure exponent of zero can be approximated only over a fairly narrow 
range of operating pressures. Typically, above and below the pressure 
range in which the ballistic modifier operates, the pressure exponent is 
positive. 
Furthermore, as the examples will show, the effect of a ballistic modifier 
in a particular formulation is frequently unpredictable. An ingredient 
which is an effective ballistic modifier with one binder, or one curing 
agent, or one distribution of oxidizer particle sizes, or in one 
proportion, may not be an effective ballistic modifier when these other 
parameters are changed. As the characteristic combustion temperature of a 
propellant is lowered substantially, the effect of the ballistic modifier 
can be changed or even eliminated in some cases. One side effect of 
excessive use of many ballistic modifiers is to decrease the burn rate of 
the propellant at all pressures, which is undesirable. Cooling agents 
often interfere with ballistic modifiers. Therefore, it is necessary to 
tailor a particular gas generator formulation by trial and error to 
provide the desired pressure exponent, .pi..sub.k profile, burning 
temperature, burning rate, and other properties simultaneously. 
Copper phthalocyanine has the following molecular formula: 
##STR1## 
Copper phthalocyanine has been used before as a burning rate modifier, but 
not as a ballistic modifier Copper chromites, Which are mixtures of copper 
oxide and chromium oxide, and metal oxides have been used before as 
ballistic modifiers. See Kirk-Othmer Encyclopedia of Chemical Technology, 
Third edition, Volume 9, page 622. U.S. Pat. No. 3,629,019, issued to 
Lawrence on Dec. 21, 1971, discloses oxides of various metals, including 
iron, chromium, and copper, as burn rate catalysts. (Burn rate catalysts 
increase the burning rate of the composition.) In column 4, lines 48-70 of 
Lawrence, copper chromite is taught to increase the burning rate of the 
propellant. No effect on the pressure exponent of the propellant is 
mentioned in Lawrence. Different ratios of copper oxide and chromium oxide 
are illustrated by Lawrence at column 5, lines 5-20 in the table. 
Two patents to Alley, et al., respectively U.S. Pat. Nos. 4,202,714, issued 
May 13, 1980, and 4,243,444, issued Jan. 6, 1981, each disclose the use of 
ballistic modifiers to impart a pressure exponent of about zero to a 
propellant over a wide pressure range and to reduce the temperature 
sensitivity of the propellant. Combinations of copper and lead chelates 
are proposed for this purpose, which is substantially similar to the 
purpose of the present invention. At column 1, lines 17-20 of Alley `714, 
cupric salicylate and lead beta-resorcylate are combined as a ballistic 
modifier. At column 2, lines 51-55, Table I and Table II of Alley `714 
combinations of copper and lead chelates are used as burn rate modifiers. 
Of particular note is column 3, lines 53-55 of Alley `714, which states 
the following: "Based on past experience, the metal, lead, will probably 
be required for it to have ballistic activity." Thus, the reference does 
not disclose the utility of copper chelates in the absence of lead 
chelates as ballistic modifiers. 
Gas generator case materials have improved, so higher combustion chamber 
pressures are obtainable. Thus, there is now a need for propellants which 
have low pressure exponents and low .pi..sub.k values at pressures 
exceeding 3500 psi (about 2400 N/cm.sup.2). These improved properties are 
necessary so a gas generator can be designed to normally operate at a 
pressure of about 3000 psi (about 2000 N/cm.sup.2) or more, with a useful 
margin of safety. Many ballistic modifiers of the prior art do not work in 
this range or do not provide a broad plateau or mesa of zero pressure 
exponent in this range. 
Objects of the Invention 
The objects of this invention are to achieve the following design criteria 
in a gas generator propellant: 
A. a burn rate exponent of substantially zero on a mesa or plateau between 
about 2000 and about 3500 or more psi (about 1375-2400 or more N/cm.sup.2) 
when other conditions of the propellant are optimized. 
B. a .pi..sub.k value of 0.17%/.degree.F. (0.30%/.degree.C.) or less. 
C. no substantial drop in burn rate due to the addition of a ballistic 
modifier to the propellant composition. 
D. a flame temperature less than or equal to about 
2000.degree. F. (about 1100.degree. C.). 
A particularly desired objective is to obtain all these criteria 
simultaneously. 
Summary of the Invention 
The present inventor has discovered that a composite propellant consisting 
essentially of from about 20 to about 88% by weight ammonium perchlorate, 
from about 8 to about 40% by weight of a carboxy-terminated polybutadiene 
binder, from about three to about 20% by weight ammonium sulfate, and from 
about 0.1 to about 2% by weight of at least one copper compound has 
desirable and unexpected properties The present inventor has found that, 
in the context of the other ingredients mentioned above, a wide variety of 
copper compounds can function as ballistic modifiers. 
The selection of a carboxy-terminated polybutadiene binder in a system 
which also contains ammonium sulfate as a cooling agent permits the copper 
compound to modify the ballistics of the composition desirably. If another 
binder is used, particularly hydroxy-terminated polybutadiene, the 
ballistic modifiers disclosed here do not work well in the presence of 
ammonium sulfate. 
Compositions having the broad proportions defined above can readily be 
formulated to have .pi..sub.k values, pressure exponents, burning rates, 
and combustion temperatures within the ranges stated as objects of the 
invention.

Detailed Description 
Propellants according lo the present invention have the basic formulation 
described above in the Summary of the Invention. 
The first ingredient of the propellant is from 20 to about 88% by weight, 
preferably from about 50 to about 70% by weight, ammonium perchlorate. 
Ammonium perchlorate functions as an oxidizer in the propellant. It is 
contemplated that other oxidizers, such as ammonium nitrate or potassium 
nitrate, can also function herein. However, ammonium perchlorate is by far 
the preferred oxidizer unless special properties, such as reduced smoke 
generation, are necessary. Ammonium perchlorate is conventionally supplied 
as a mixture of feedstocks having different average particle sizes Under 
certain circumstances, illustrated in the examples and in FIG. 6, certain 
ratios of 90 micron and 18 micron particles, preferably a ratio of 70 
parts of 90 micron particles and 30 parts of 18 micron particles, increase 
the range of pressures at which the pressure exponent is nearly zero. 
Ammonium perchlorate is typically the dominant ingredient in composite 
propellants. The other ingredients can be thought of as modifiers which 
provide desirabIe characteristics to ammonium perchlorate. Taken by 
itself, ammonium perchlorate has a burn rate exponent of about 0.4 to 0.5 
over the range of from about 1000 to 3000 or more psi (from about 690 to 
about 2000 N/cm.sup.2). 
The second ingredient of the propellant contemplated herein is from about 
8% to about 40% by weight, preferably from about 15% to about 30% by 
weight, of a carboxy-terminated polybutadiene binder. While other binders, 
particularly hydroxy-terminated polybutadiene, are more frequently used in 
propellant compositions, in the present system carboxy-terminated 
polybutadienes have been found to be superior binders because they do not 
interfere with the effect of copper compounds as ballistic modifiers. The 
general structure of carboxy-terminated polybutadienes is disclosed in 
U.S. Patent No. 4,624,885, issued to Mumford, et al., on Nov. 25, 1986. 
See in particular the text from column 3, line 48 to column 4, line 35, 
which describes chain-extended carboxy-terminated poly-1,2-butadienes 
useful herein. The organic peroxides and azo curing agents which are 
associated with carboxy-terminated polybutadienes are described from 
column 4, line 54 to column 5, line 13 of the same patent. The portions of 
U.S. Pat. No. 4,624,885 discussed above are hereby incorporated herein by 
reference. A particular carboxy-terminated polybutadiene useful herein is 
described in the examples. 
The third principal component of the present propellant composition is from 
about 3% to about 20% by weight, preferably from about 8% to about 17% by 
weight, ammonium sulfate, which functions as a cooling agent. Ammonium 
sulfate is an interfering ingredient which prevents ballistic modifiers 
from operating in systems bound with hydroxy-terminated polybutadiene. The 
amount of ammonium sulfate used is regulated by the presence of other 
cooling ingredients and the degree of cooling desired. Other known cooling 
agents, such as DHG (dihydroxylglyoxime) and DAG (diaminoglyoxime) can 
also be used. The presence of substantial proportions of cooling agents 
distinguishes the present gas generator composition from rocket propellant 
compositions, which typically function at a much higher temperature. 
The fourth essential ingredient of the present propellant compositions is 
from about 0.1% to about 2% of at least one copper compound. A first class 
of copper compounds contemplated herein is copper chelates. The Alley et 
al Patents previously cited, for example the `714 patent, column 2, lines 
51-55 and Tables I and II, describe a variety of copper chelates. A 
preferred copper chelate for use herein is copper phthalocyanine. As 
mentioned before, copper phthalocyanine is known as a burn rate modifier. 
Burn rate suppression is not desired in the present propellants, so the 
amount of copper phthalocyanine used is preferably regulated so the 
burning rate is not substantially reduced by addition of this ingredient. 
In the case of copper phthalocyanine in the present system, the preferred 
proportions are from 0.5% to 2% by weight, most preferably from about 1% 
to about 1.5% by weight. 
A second category of copper compounds useful herein is salts of fatty acids 
or lower alkyl carboxylic acids. The carboxylic acids contemplated herein 
are mono- or polyoarboxylic acids having from about 1 to about 22 carbon 
atoms. One particular such compound, the copper salt of stearic acid, has 
been found particularly useful herein About 0.5% to about 2% copper 
stearate is preferred for use herein. 
A third category of copper compounds useful as ballistic modifiers herein 
is inorganic copper salts and salt mixtures containing the same. One 
particular compound contemplated herein is copper chromite. Although 
copper (I) chromite is assigned the exact formula Cu.sub.2 Cr.sub.2 
O.sub.4 in the CRC Handbook of Chemistry and Physics, 49th edition, 
1968-1969, the copper chromite contemplated herein is a mixture having 
different proportions of copper oxide, Cu.sub.2 O, and chromium oxide, 
Cr.sub.2 O.sub.3. U.S. Pat. No. 3,629,019, cited previously, in column 4, 
lines 48-70 and column 5, lines 5-20, shows different ratios of copper 
oxide and chromium oxide and the utility of the mixtures as a catalyst. 
The reference does not mention an effect on pressure exponent. The recited 
portions of the `019 patent are hereby incorporated herein by reference. 
The preferred proportions of copper chromite in the present system are 
from 0.5% to 0.7% by weight. 
Since an inorganic copper compound, a simple aliphatic copper salt, and a 
complex copper chelate have each been found to act as a ballistic 
modifiers in the present propellant system, it is more broadly 
contemplated that any copper compound which is a source of copper in 
complexed or ionic form has utility as a ballistic modifier in the present 
system. 
A wide variety of usual additional ingredients is contemplated for use 
herein. In the event a more energetic propellant is desired, from about 1% 
to about 20% by weight of a metal powder selected from aluminum, 
magnesium, boron, zinc, beryllium, mixtures thereof, and other metals 
commonly used as fuels in propellants is contemplated herein. Only minor 
proportions of such ingredients are preferred herein, however, to keep the 
flame temperature low. 
Other modifying ingredients are also contemplated herein. Burn rate 
catalysts such as ferric oxide and chromium octoate can be used. 
Propellant bonding agents such as a propylene imine adduct of isophthalyl 
chloride are contemplated, for example. Other ballistic modifiers can also 
be combined with the copper compounds of the present invention. In one 
embodiment of the invention, lead compounds can be present as disclosed in 
the prior art, although another embodiment of the invention is essentially 
free of lead compounds. Any of the other known propellant ingredients are 
also useful herein, with the proviso that if a low temperature propellant 
is desired the proportions of highly energetic ingredients such as HMX, 
RDX, nitrate esters, and the like should be minimal. 
Examples 
The propellant compositions set forth in Tables 1, 2, and 3 below were 
prepared as follows. First, the propellant ingredients other than the 
curing agents (DDI or ERL-0510), cure catalysts (such as chromium 
octoate), and ammonium perchlorate were thoroughly mixed in a mixing bowl 
at 90.degree. F. .+-. 5.degree. F. (32.degree. C. .+-. 3.degree. C.). The 
ammonium perchlorate was added and mixed in four increments. These 
ingredients were mixed thoroughly for at least 35 minutes. Then the cure 
catalyst was added and mixed for 20 minutes. 
For the compositions A-W of TabIe 1, the complete propellant was cast into 
a container and cut into strands. The burning rate and pressure plots of 
FIGS. 2-7 were generated by burning the strands. 
Trials X - AC of Table 2 were carried out by casting each of the respective 
compositions into a four inch (10 cm) diameter by 12 inch (30 cm) long 
phenolic cylinder. The cylinder was removed, leaving a casting. The 
casting was cut into six four inch (10 cm) diameter, 2 inch high 
cylindrical grains. Each grain was machined to form a one pound (0.45 kg) 
grain of uniform size and shape, then potted into a test motor which was 
static fired. 
The propellant of Table 3 was cast. Samples were taken from the casting, 
aged for the indicated time, and evaluated for mechanical properties. 
FIG. 1 is taken from page 58 of Foster, et al., Low Exponent Teohnology, 
Report No AFRPL-TR-81-95 of the Air Force Rocket Propulsion Laboratory, 
Edwards Air Force Base, California, U.S.A (February, 1982). Plot A is for 
a formulation which contained 0.5% copper phthalocyanine and employed a 
hydroxy-terminated polybutadiene binder cured with isophorone diisocyanate 
-- IPDI. The positive and steadily increasing slope of the curve indicates 
a positive pressure exponent, which is undesirable. Plot B is for a 
similar composition which also contained 0.5% copper phthalocyanine, but 
used DDI as a curing agent. Plot B is close to horizontal in the range 
between about 600 psi (414 N/cm.sup.2) and 2000 psi (1379 N/cm.sup.2), 
shows a substantially greater but still moderate pressure exponent between 
2000 and 4000 psi (1379 to 2758 N/cm.sup.2), and shows a sharp break or 
increase in the pressure exponent above 4000 psi. This illustrates the 
unpredictability of the value of copper phthalocyanine as a ballistic 
modifier if other ingredients of the composition are changed. It should 
also be noted that the propellants characterized in FIG. 1 are rocket 
propellants which do not contain ammonium sulfate or other cooling agents. 
Turning to Table 1 and FIG. 2, compositions C and D were within the scope 
of the present invention, as they employed a carboxy-terminated 
polybutadiene binder, ammonium sulfate as a curing agent, and ammonium 
perchlorate as the oxidizer. Compositions C and D also contained a copper 
compound as a ballistic modifier. Plot C, for a composition employing 
copper chromite as a ballistic modifier, shows a substantially flat 
pressure exponent between about 1500 psi (1000 N/cm.sup.2) and about 3200 
psi (about 2200 N/cm.sup.2). Curve C breaks sharply upward above this 
pressure region, but is very flat Within it. In the trial of plot D the 
propellant contained 0.5% copper phthalocyanine, and showed similar 
results between 1000 and about 3300 psi (about 1700 to 2200 N/cm.sup.2), 
although the central region is not quite as flat as for curve C. However, 
curve D remains substantially flat, representing a substantially zero 
exponent, up to a pressure of about 4200 psi (nearly 3000 N/cm.sup.2). 
Copper phthalocyanine thus provided a wider plateau of zero exponent 
behavior in the propellant, and thus a higher safe operating pressure. 
Propellant E differed from propellant D only in the use of a 
hydroxy-terminated polybutadiene binding agent instead of a 
carboxy-terminated polybutadiene binding agent. Curve E shows a clearly 
unsatisfactory propellant from the point of view of ballistics. The curve 
has a short plateau from about 1000 psi to 1500 psi (700 N/cm.sup.2 to 
1100 N/cm.sup.2), and another plateau between about 3200 psi and 5000 psi 
(about 2200 to 4000 N/cm.sup.2). The lower plateau is clearly at a 
pressure too low to provide a satisfactory gas generator, particularly one 
in which the combustion pressure is intended to be maximized. The high 
plateau is too high for a practical gas generator, since the case would 
have to withstand an extremely high pressure to operate in this range. 
FIG. 2 thus also establishes the criticality of other ingredients to the 
utility of copper phthalocyanine or copper chromite as ballistic modifiers 
when ammonium sulfate is present. The presence of ammonium sulfate was the 
primary distinction between the compositions of curve E of FIG. 2 and 
curve B of FIG. 1 (each being cured with DDI). Curves B and E will be 
noted to have a similar shape, although the shape is not as clearly 
apparent in FIG. 1. 
FIG. 3 compares copper chromite, copper phthalocyanine, and copper stearate 
at identical 0.5% levels in a propellant which also contains 17% ammonium 
sulfate and a carboxy-terminated polybutadiene binder. Curve F employing 
copper chromite shows the highest burn rate, but has a flat pressure 
exponent plot only from 1500 to 3200 psi (about 1070 to 2200 N/cm.sup.2). 
However, the pressure exponent is almost exactly zero in this range, 
before breaking upward above that pressure region. Curve G represents a 
propellant containing copper stearate and has a moderately negative 
exponent from 1500 to 3700 psi about 1070 to over 2500 N/om.sup.2). While 
a zero exponent is preferred to a negative exponent, a negative exponent 
is preferred to a positive exponent because the burn rate of a negative 
exponent propellant will tend to moderate when pressure increases, thus 
counteracting the increase of burn rate. Curve H employs copper 
phthalocyanine, and in this particular formulation reduces burn rate 
somewhat, but provides a substantially zero pressure exponent from 2200 to 
3700 psi (about 1500 to 2500N/cm.sup.2), and probably below that range as 
well, although this data was not taken. Curve H breaks upward at about the 
same point as curve G, but its region of best pressure exponent is a 
substantially flat plateau instead of a negative exponent. Each of these 
curves represents a propellant with a theoretical flame temperature of 
1855.degree. F. (1013.degree. C.), resulting from the incorporation in 
each of 17% ammonium sulfate. Curves F, G, and H all exhibit much better 
pressure exponent performance than curve E for most practical gas 
generators. FIG. 3 thus demonstrates that a variety of different copper 
compounds can provide the benefits of the present invention in an ammonium 
sulfate cooled carboxy-terminated polybutadiene bound propellant. 
Turning to FIG. 4, these propellants contained a smaller quantity of 
ammonium sulfate and thus have a much higher burning rate. 0.1% copper 
chromite (Curve M) provided a flat pressure exponent between about 2300 
and 3300 psi (about 1600 to 2250 N/cm.sup.2). Burning rates and pressures 
were not measured below the lower end of the curve in this example. Thus, 
as little as 0.1% copper chromite provided at least some of the benefit of 
the invention. Curve I, for a propellant employing 0.3% copper chromite, 
does not show a region of flat pressure exponent, and so composition I was 
not a particularly desirable propellant The propellant characterized by 
Curve K contained 0.5% copper chromite. It provided a region of 
substantially zero pressure exponent between 1500 and about 3300 psi 
(about 1050 to 2350 N/cm.sup.2). Its burning rate was also substantially 
better than that of composition M, which contained 0.1% copper chromite, 
and thus composition K was the most preferred of the M, I, and K 
compositions. Plot L has a similar shape to plot M, but at a higher 
burning rate. The same can be said of plot J, in which 1% copper chromite 
was employed in the propellant composition. Since curve I is a formulation 
having an intermediate amount of copper chromite, and is the only one 
which differs from the shape of the family of curves, it would appear that 
experimental error has affected plot I. All the other curves demonstrate 
the value of copper chromite as a ballistic modifier which produces a 
region of flat pressure exponent in a useful pressure range. 
FIG. 5 shows the result of using various amounts of copper phthalocyanine 
in a propellant composition bound with carboxy-terminated polybutadiene 
and containing 17% ammonium sulfate as a cooling agent. While all the 
curves demonstrate a useful region of zero pressure exponent, curves O and 
P representing 1 to 1.5% copper phthalocyanine show a higher burning rate 
at lower pressures and a lower burning rate at higher pressures, and thus 
a very flat pressure exponent curve between about 2200 and 5000 psi (about 
1500 to over 3500 N/cm.sup.2) (particularly for plot P). Plot Q, 
representing 2% copper hthalocyanine, shows a flat pressure exponent 
region of nearly similar breadth, but at a lower burning rate. For that 
reason composition Q would usually be less desirable than composition P. 
In FIG. 6 the compositions have identical proportions chemically. However, 
as shown in Table 1, for composition R the ratio of 90 micron (weight mean 
diameter) ammonium perchlorate to 18 micron ammonium perchlorate was 50% 
to 50%, in composition S the ratio was 60% to 40%, and in composition T 
the ratio was 70% to 30%. Curve T provides the best result, thus 
illustrating the superiority of a 70/30 mixture of a 90 micron and 18 
micron ammonium perchlorate in the present compositions. Plot T is 
substantially flat from about 2250 to 4300 psi (about 1500 to 3000 
N/cm.sup.2). Curve S provides a similarly low pressure exponent over a 
somewhat narrower range, providing a lower break point. Curve R does not 
show particularly good performance, as the entire curve is sloped 
substantially. All these curves are better than they Would be if a 
different ballistic modifier or no ballistic modifier was present. 
FIG. 7 shows the results obtained from comparable formulations in which 
much of the ammonium sulfate was replaced with other cooling agents -- DHG 
or DAG. These propellants also contained 0.5% ferric oxide as a burn rate 
catalyst. Only curve W represents a composition containing a copper 
compound as a ballistic modifier -- copper phthalocyanine. First, the 
curves demonstrate some benefit of using the copper compound as a 
ballistic modifier, as curve W has a somewhat higher break point (about 
4200 psi or 2900 N/cm.sup.2) defining the end of its region of 
substantially zero pressure exponent. The break point of curve V is at 
about 3700 psi (about 2500 N/cm.sup.2), and the break point of curve U 
appears to be at about the same point. In fact. curve V slopes positively 
over its entire length. FIG. 7 also demonstrates that when less ammonium 
sulfate is used as a cooling agent (as noted from Table 1 for compositions 
U, V, and W), copper phthalocyanine seems to have a less pronounced effect 
on the ballistics of the compositions. (Compare curves and compositions V 
and W.) 
Table 2 shows the compositions and .pi..sub.k values for propellant 
compositions X - AC. To obtain .pi..sub.k values, a series of 1 lb. (.45 
kg) end-burner motors were made and fired at two different initial 
propellant temperatures (obtained by conditioning the unburned motor at 
the desired propellant temperature for long enough to reach equilibrium at 
that temperature). Here, T.sub.2 was 125.degree. F. (52.degree. C.) and 
T.sub.1 was -15.degree. F. (-26.degree. C.). The pressures given in the 
table are the actual P values at which .pi..sub.k was measured. First 
comparing compositions X and Y containing different proportions of copper 
phthalocyanine, at lower pressures a greater proportion of copper 
phthalocyanine provided a higher .pi..sub.k, which is less desirable. At a 
pressure which exceeded 3000 psi (2000 N/cm.sup.2), however, the higher 
amount of copper phthalocyanine provided a lower .pi..sub.k. To put this 
in perspective, no low flame temperature gas generator composite 
propellant has previously been developed with a .pi..sub.k value of less 
than 0.2% per .degree.F. (0.36% per .degree.C.) for a pressure greater 
than 3000 psi (about 2000 N/cm.sup.2). Thus, both formulation X and 
formulation Y exhibit the desirable .pi..sub.k benefit of the present 
invention. 
Now compare trials X and Z, which differ only in that ferric oxide was 
added to Z. Only the medium and high pressure .pi..sub.k values were 
measured. The composition containing ferric oxide performed somewhat 
better than the composition without ferric oxide, even though the actual 
pressures of measurement of .pi..sub.k for formula Z were slightly higher. 
Formulation Z thus appears to be even better than formulas X or Y, 
although all three are among the best ever reported. 
Trials AA and AC are respectively formulations which lack or contain 0.5% 
copper phthalocyanine and otherwise are substantially identical. The 
medium pressure measurement of .pi..sub.k for compositions AA and AC shows 
that the presence of copper phthalocyanine lowers the .pi..sub.k value 
substantially, providing a value of 0.136% per .degree.F. (0.24% per 
.degree. C). For the high pressure .pi..sub.k, even more dramatic results 
are achieved. Composition AA burst the test motor, and thus .pi..sub.k was 
not measurable. Composition AC had a very low .pi..sub.k value of 0.1% per 
.degree.F. (0.18% per .degree.C.). Thus, without the copper compound the 
propellant failed, and with the copper compound it provided exceedingly 
good performance. Comparing compositions AA and AB, which were the same 
except for the choice of different cooling agents, composition AB had a 
substantially higher .pi..sub.k at moderate pressure than did composition 
AC. 
Table 3 shows a formulation within the scope of the present invention and 
Table 4 shows the mechanical properties of the composition of Table 3. The 
properties changed substantially at first as curing continued, but became 
substantially consistent after several weeks. These properties are 
satisfactory for use of the present compositions in gas generators. 
TABLE 1 
__________________________________________________________________________ 
Plot: A.sup.15 
B.sup.15 
C D E F G H I J K L M 
__________________________________________________________________________ 
Prior 
Prior 
Ingredient (wt. %) 
Art Art 
Ammonium 57.50 
57.50 
57.50 
57.50 
57.50 
57.50 
66.70 
66.00 
66.50 
66.30 
66.90 
perchlorate.sup.1 
HTPB.sup.2 x x -- -- 20.62 
-- -- -- -- -- -- -- -- 
IPDI.sup.14 
x -- -- -- -- -- -- -- -- -- -- -- -- 
DDI.sup.3 x -- -- 4.08 
-- -- -- -- -- -- -- -- 
HX-752.sup.4 -- -- 0.30 
-- -- -- -- -- -- -- -- 
CTPB.sup.5 23.94 
23.94 
-- 23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
ERL-0510.sup.6 1.05 
1.05 
-- 1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
Chromium 0.01 
0.01 
-- 0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
octate 
Ammonium 17.00 
17.00 
17.00 
17.00 
17.00 
17.00 
8.00 
8.00 
8.00 
8.00 
8.00 
sulfate 
DHG.sup.7 -- -- -- -- -- -- -- -- -- -- -- 
DAG.sup.8 -- -- -- -- -- -- -- -- -- -- -- 
Copper 0.5 0.5 -- 0.50 
0.50 
-- -- 0.50 
-- -- -- -- -- 
phthalocyanine 
Copper 0.50 
-- -- 0.50 
-- -- 0.30 
1.00 
0.50 
0.70 
0.10 
chromite.sup.9 
Copper -- -- -- -- 0.50 
-- -- -- -- -- -- 
stearate 
Ferric 
oxide 
Total 100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
__________________________________________________________________________ 
1 
Plot: N O P Q R S T U V W 
__________________________________________________________________________ 
Ingredient (wt. %) 
Ammonium 57.50 
57.00 
56.50 
56.00 
57.00 
57.00 
57.00 
49.50 
49.50 
49.00 
perchlorate.sup.1 (50/50).sup.10 
(60/40).sup.11 
(70/30).sup.12 
HTPB.sup.2 
-- -- -- -- -- -- -- -- -- -- 
IPDI.sup.14 
-- -- -- -- -- -- -- -- -- -- 
DDI.sup.3 -- -- -- -- -- -- -- -- -- -- 
HX-752.sup.4 
-- -- -- -- -- -- -- -- -- -- 
CTPB.sup.5 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
ERL-0510.sup.6 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
1.05 
Chromium 0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
octoate 
Ammonium 17.00 
17.00 
17.00 
17.00 
17.00 
17.00 
17.00 
5.00 
5.00 
5.0 
sulfate 
DHG.sup.7 -- -- -- -- -- -- -- 0 20 20 
DAG.sup.8 -- -- -- -- -- -- -- 20 0 0 
Copper 0.50 
1.00 
1.50 
2.00 
1.00 
1.00 
1.00 
-- -- 0.50 
phthalocyanine 
Copper -- -- -- -- -- -- -- -- -- -- 
chromite.sup.9 
Copper -- -- -- -- -- -- -- -- -- -- 
stearate 
Ferric -- -- -- 0.50 
0.50 
0.50 
oxide 
Total 100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
__________________________________________________________________________ 
5 
Note: Footnotes are in the last table. 
TABLE 2 
__________________________________________________________________________ 
Example: X Y Z AA AB AC 
__________________________________________________________________________ 
Ingredient (wt. %) 
Ammonium 57.50 
57.00 
57.00 
57.50 
57.50 
57.00 
perchlorate.sup.1 
CTPB.sup.5 23.94 
23.94 
23.94 
23.94 
23.94 
23.94 
ERL-0510.sup.6 
1.05 
1.05 
1.05 
1.05 
1.05 
1.50 
Chromium 0.01 
0.01 
0.01 
0.01 
0.01 
0.01 
octate 
Ammonium 17.00 
17.00 
17.00 
5.00 
5.00 
5.00 
sulfate 
DHG.sup.7 -- -- -- 20.00 
-- 20.00 
DAG.sup.8 -- -- -- -- 20.00 
-- 
Copper 0.50 
1.00 
0.50 
-- -- 0.50 
phthalocyanine 
Ferric -- -- 0.5 0.5 0.5 0.5 
oxide 
Total 100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
.eta..sub.k, %/.degree.C. 
0.27 0.76 
-- -- -- 0.32 
pressure, N/cm.sup.2 
1614 1577 
-- -- -- 1704 
.eta..sub.k, %/.degree.C. 
0.32 0.41 
0.26 0.31 
0.51 0.24 
pressure, N/cm.sup.2 
1828 1870 
1966 1833 
1869 1992 
.eta..sub.k, %/.degree.C. 
0.36 0.28 
0.28 Burst.sup.13 
Burst.sup.13 
0.18 
pressure, N/cm.sup.2 
2070 2164 
2359 -- -- 2234 
__________________________________________________________________________ 
Note: Footnotes are in the last table. 
TABLE 3 
______________________________________ 
Example: AD 
______________________________________ 
Ingredient (wt. %) 
Ammonium 57.50 
perchlorate.sup.1 
CTPB.sup.5 23.94 
ERL-0510.sup.6 1.05 
Chromium 0.01 
octoate 
Ammonium 17.00 
sulfate 
Copper 0.50 
phthalocyanine 
Total 100.00 
______________________________________ 
Note: Footnotes are in the last table. 
TABLE 4 
______________________________________ 
Time at 66.degree. C. 
Modulus E.sub.0 
Stress (cm) Strain, % 
(weeks) N/cm.sup.2 N/cm.sup.2 Em/E.sub.R 
______________________________________ 
0 647 123 48/50 
2 949 136 24/32 
4 982 142 25/30 
6 1110 151 24/28 
8 1240 155 16/18 
10 1360 140 20/22 
______________________________________ 
Footnotes to Tables 
1. 70 wt. % 90 micron particles, 30 wt. % 18 micron particles (unless 
otherwise specified). 
2. hydroxy-terminated polybutadiene; sold under the trade designation R45M 
by Arco Chemical Co., Philadelphia, Pa. 
3. Tradename for a proprietary aliphatic diisocyanate sold by Henkel Corp., 
Minneapolis, Minn. 
4. propylene imine adduct of isophthalyl chloride; acts as a bonding agent. 
5. carboxy-terminated polybutadiene, equivalent weight 1923 grams; sold 
under the tradename HC-434 by Thiokol Corp., Ogden, Utah. 
6. triglycidyl ether adduct of p-aminophenol equivalent weight 97 grams. 
dihydroxyglyoxime 
8. diaminoglyoxime 
9. CuO:Cr.sub.2 O.sub.3 ratio is 17%:83% (unless otherwise specified). 
10. indicates a mixture of 50% 90micron weight mean diameter ammonium 
perchlorate and 50% 18 micron weight mean diameter ammonium perchlorate. 
11. similar to 10, with 60% 90 micron ammonium perchlorate and 40% 18 
micron ammonium perchlorate 
12. similar to 11, with 70/30 ratio. 
13. case burst due to overpressure during combustion. 
14. isophorone diisocyanate. 
15. ingredients marked "x" are those identified by prior art. Their 
proportions are not known except as indicated, and other ingredients were 
probably present.