US3798088A

US3798088A - Cocrystallization of ammonium perchlorate and stabilization of solid propellants

Info

Publication number: US3798088A
Application number: US00338127A
Authority: US
Inventors: E Lindsay
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1973-03-05
Filing date: 1973-03-05
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19

Abstract

A method of improving the thermal stability of double-base propellants containing ammonium perchlorate (AP) by cocrystallization of AP with resorcinol before formation of the propellant grain. AP is dissolved in a solution of liquid ammonia; resorcinol is added to the solution. After evaporation and drying the resulting cocrystals are ground and, in the conventional manner, incorporated into a propellant matrix.

Description

United States Patent [191 Lindsay COCRYSTALLIZATION OF AMMONIUM PERCHLORATE AND STABILIZATION OF SOLID PROPELLANTS [75] Inventor: Edward K. Lindsay, Cumberland,

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Mar. 5, 1973 [21] Appl. No.: 338,127

[52] US. Cl 149/20, 149/42, 149/76, 149/98, 423/386 [51] Int. Cl C06b 11/00 [58] Field of Search 149/20, 76, 42, 98; 423/386 [56] References Cited UNITED STATES PATENTS 3.172.793 3/1965 Markowitz 149/76X Mar. 19, 1974 Rice 149/76 Morrow 149/76 X Primary ExaminerStephen J. Lechert, Jr. Attorney, Agent, or FirmP. Schneider; R. S. Sciascia 5 7] ABSTRACT 13 Claims, No Drawings COCRYSTALLIZATION OF AMMONIUM PERCHLORATE AND STABILIZATION OF SOLID PROPELLANTS BACKGROUND OF THE INVENTION This invention relates generally to a method of stabilizing the deterioration of solid propellants and more specifically to a method of cocrystallizing AP and resorcinol to improve the stability of double-base propellants employing AP.

Solid propellants typically contain at least two of the following ingredients: an oxidizer, typically a nideate or perchlorate; a fuel, such as an organic resin or plastic; and a compound combining both fuel and oxidizer qualities, such as nitrocellulose or nitroglycerine. Those propellants which include nitrocellulose and/or nitroglycerine, which are capable of combustion in the absence of all other materials, are called double-base propellants.

One of the great advantages of solid propellants over liquid propellants is the longer storage capability of the former. However, many solid propellants do deteriorate over periods of time. Some experience a low-order chemical reaction during storage, and in various double-base propellants the decomposition is selfcatalyzing. This decomposition can have extreme effects on the energy potential of the grain, and potentially disastrous effects on grain structure.

In the case of double-base propellants containing AP, a reaction between the nitrate esters and AP leads to the formation of gases in the propellant grain. These gases create voids or pockets in the grain which can have an adverse effect on the burning rate. Moreover, during prolonged storage periods, the formation of gas may produce cracks in the grain which may ultimately cause total failure of a missile. Generally, stabilizers employed to inhibit the decomposition of the nitrate esters have been added as discrete particles to the propellant matrix while it was in a workable plastic state. The resultant particle distribution and stabilizer effect were therefore dependent upon mechanical mixing efficiency.

SUMMARY OF THE INVENTION The present invention improves the ability of a stabilizer, resorcinol, to inhibit the reaction between AP and the nitrate esters in a double-base solid propellant grain by cocrystalizing the stabilizer with the AP before incorporation of both into the propellant matrix. The homeomorphism of the crystals and the intimacy of the admixture improve efficiency of stabilization due to the close proximity of AP and the stabilizer. Cocrystallization will also inhibit sublimation of the resorcinol.

OBJECTS OF THE INVENTION An object of the present invention is to inhibit the reaction between the nitrate esters in a double base propellant and AP incorporated into the propellant matrix.

Another object is to cocrystallize AP and resorcinol.

A further object of the invention is to inhibit the sublimation of resorcinol.

Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cocrystallization of AP and resorcinol is best accomplished by employing a liquid ammonia bath. Pressurized ammonia gas can be liquified in a cold-trap submerged in a solid carbon dioxide-acetone mixture. To produce an immediate solution AP was added to the liquid ammonia to achieve substantially a 1.5 ml/g (Nl-I /AP) volume-to-weight ratio. Resorcinol was then added to the solution. By weight the resorcinol is l to 10 percent of the AP and resorcinol added to the ammonia, although 3 percent is preferred.

The solution is allowed to evaporate at room temperature until the resulting cocrystals are clamp. The crystals are then dryed at l0O-l50F for one-half to one hour. Finally the cocrystals were placed in a subatmospheric chamber at 25 millimeters of mercury at room temperature for 16-72 hours. After these drying steps the cocrystals are ground and used to prepare a double base solid propellant grain in the conventional manner.

In order that one skilled in the art may practice the present invention, the following table sets forth an example of ingredients which are necessary to formulate a solid propellant grain.

Parts by weight Ammonium perchlorate-resorcinol 2 .40

Mixing and casting of the above constituents may be carried out in conventional manners applicable to the processing of double base propellants. It should be noted that the method of stabilization described is applicable to any double base propellant including AP in its formulation.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. The process of stabilizing the decomposition of nitrate esters in a double-base propellant containing ammonium perchlorate comprising cocrystallizing the ammonium perchlorate with resorcinol before incorporation into the propellant matrix.

2. The process of claim 1 wherein the cocrystallization is accomplished by dissolving ammonium perchlorate and resorcinol in a liquid ammonia solution; allowing the liquid ammonia to evaporate, and drying the cocrystals.

3. An oxidizer for use in a double base solid propellant grain, said oxidizer comprising, cocrystals of ammonium perchlorate and resorcinol.

4. A method of producing an oxidizer for use in a double-base solid propellant grain comprising the steps of:

combining ammonium perchlorate and resorcinol in liquid ammonia;

allowing the liquid ammonia to evaporate; and

drying the cocrystals of ammonium perchlorate and resorcinol.

5. The process of claim 2 wherein the ammonium perchlorate is added to the liquid ammonia to achieve substantially a 1.5 ml/g (NI-MAP) volume-to-weight ratio.

6. The process of claim 5 wherein the resorcinol by weight is l to percent of the ammonium perchlorate and resorcinol added to the liquid ammonia.

7. The process of claim 6 wherein the resorcinol by weight is 3 percent of the ammonium perchlorate and resorcinol added to the liquid ammonia.

8. The method of claim 4 wherein the resorcinol by weight is l to 10 percent of the ammonium perchlorate and resorcinol combined in the liquid ammonia.

9. The method of claim 8 wherein the resorcinol by weight is 3 percent of the ammonium perchlorate and resorcinol combined in the liquid ammonia.

10. The method of claim 8 wherein enough ammonium perchlorate (AP) is added to the liquid ammonia (NI-l to produce substantially a 1.5 ml/g (NH /AP) volume-to-weight ratio.

ll 1. A double base solid propellant comprising a compound from the group consisting of nitrocellulose or nitroglycerine combined with cocrystals of ammonium perchlorate and resorcinol.

12. In combination with a double base propellant an oxidizer comprising:

cocrystals of ammonium perchlorate and resorcinol.

13. A method of producing a double base propellant which comprises:

cocrystallizing ammonium perchlorate with resorcinol to produce cocrystals of ammonium perchlorate and resorcinol; and

incorporating the cocrystals into a double base solid propellant.

Claims

2. The process of claim 1 wherein the cocrystallization is accomplished by dissolving ammonium perchlorate and resorcinol in a liquid ammonia solution; allowing the liquid ammonia to evaporate, and drying the cocrystals.
3. An oxidizer for use in a double base solid propellant grain, said oxidizer comprising, cocrystals of ammonium perchlorate and resorcinol.
4. A method of producing an oxidizer for use in a double-base solid propellant grain comprising the steps of: combining ammonium perchlorate and resorcinol in liquid ammonia; allowing the liquid ammonia to evaporate; and drying the cocrystals of ammonium perchlorate and resorcinol.
5. The process of claim 2 wherein the ammonium perchlorate is added to the liquid ammonia to achieve substantially a 1.5 ml/g (NH3/AP) volume-to-weight ratio.
6. The process of claim 5 wherein the resorcinol by weight is 1 to 10 percent of the ammonium perchlorate and resorcinol added to the liquid ammonia.
7. The process of claim 6 wherein the resorcinol by weight is 3 percent of the ammonium perchlorate and resorcinol added to the liquid ammonia.
8. The method of claim 4 wherein the resorcinol by weight is 1 to 10 percent of the ammonium perchlorate and resorcinol combined in the liquid ammonia.
9. The method of claim 8 wherein the resorcinol by weight is 3 percent of the ammonium perchlorate and resorcinol combined in the liquid ammonia.
10. The method of claim 8 wherein enough ammonium perchlorate (AP) is added to the liquid ammonia (NH3) to produce substantially a 1.5 ml/g (NH3/AP) volume-to-weight ratio.
11. A double base solid propellant comprising a compound from the group consisting of nitrocellulose or nitroglycerine combined with cocrystals of ammonium perchlorate and resorcinol.
12. In combination with a double base propellant an oxidizer comprising: cocrystals of ammonium perchlorate and resorcinol.
13. A method of producing a double base propellant which comprises: cocrystallizing ammonium perchlorate with resorcinol to produce cocrystals of ammonium perchlorate and resorcinol; and incorporating the cocrystals into a double base solid propellant.