US3919012A

US3919012A - Propellant composition

Info

Publication number: US3919012A
Application number: US097467A
Authority: US
Inventors: William R Mcbride; William G Finnegan; Arnold Adicoff
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1970-11-24
Filing date: 1970-11-24
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A solid composite propellant composition consisting essentially of a conventional binder containing modified ammonium perchlorate which consists of whisker-like single crystals without inclusions and ranging in diameter from about 1 to 40 microns.

Description

United States Patent McBride et al.

1451 Nov. 11, 1975 PROPELLANT COMPOSITION 3.203.842 8/1965 066116 149.131 1.301.712 1/1967 Mnhuup! e! 211 149,-1 [75] [memory Y' McBr'dei 3.359.3511 12/1967 06am; 264/3 R Flnflegani Adicofi, Of 3.383.180 4/1968 Krulik e! 111. 149/76 x m Lake. lf- 3.454.437 7/1969 Yumazaki et 61 149121 1731 AS99139 The Wed S919 America 85 3123213 1/133? 35323511.?ijiiijjjiii'"Jji'ij 113132;? "eprmmed P 3.673.013 6/1972 Lane 61211 14911 1.1 x Navy, Washington. DC.

[22] Filed: Nov. 24, 1970 Primary E.\r1mi:1er\ 'erlin R. Pendegrass Assistant Examiner-P. A. Nelson 7 1 [*1] App! 97'467 Attorney, Agent. or Firm-R S. Sciascia; R0 Miller;

Lloyd E. K. Pohl [52] US. Cl. 149/195; 149/2; 149/199; 149/76; 149/113 [51] Int. Cl. C06P 45/10 [57] ABSTRACT [58] Fi f Search 149 p 17 113 21 7 A solid composlte pronellant comp0sm0n cons1stmg 149 19 19 4 essential] of a conventional b1nder containing modi- 5, 9. 26 /3 R 1 I fied ammonium perchlorate which cons1sts of whisker- [56] R fe cu d like single crystals without inclusions and ranging in UNITED STATES PATENTS diameter from about 1 to 40 microns.

2.991.168 7/1961 19.11161 149/2 4 Claims, 1 Drawing Figure O z 1.0 O a 0.8 U] E 0 0.6 E

Z 0.4 ,i 1 [I PRESSURE 1N 1 s1A US. Patent Nov. 11,1975 3,919,012

RATE IN INCH/SECOND 0 O b (D O r n u l r 1 1 'I O0 ZOO 400 600 1 OOO ZOOO 4000 PRESSURE IN PSIA INVENTORS.

WILLIAM R. MCBRIDE WILLIAM G. F'QNNEGAN ARNOLD ADICOFF BY ROY MILLER ATTORNEY.

PROPELLANT COMPOSITION STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The invention relates to improved solid propellants, and more particularly to a composite propellant formulation containing modified ammonium perchlorate crystals.

As a result of the need in modern rocket technology greater refinement in the development of solid propellants has become necessary. More powerful rocket ingredients are constantly being sought to provide improved environmental resistant qualities, improved physical properties, better and unique burning rate characteristics, and to yield improved thrust-time characteristics. The present invention utilizes a modified form of ammonium perchlorate crystals which provides improved physical and chemical properties over compositions using regular grind ammonium perchlorate crystals.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a graph which summarizes and compares the burning rates for the propellant strands of propellant formulations containing commercially ground ammonium perchlorate, nominal 40-;1. whisker ammonium perchlorate and nominal 3- whisker ammonium perchlorate.

BRIEF DESCRIPTION OF THE INVENTION Broadly speaking, the present invention resides in a composite propellant composition comprising a conventional propellant binder and modified ammonium perchlorate cystals in the form of whiskers having a length to diameter ratio of about 5:1 to about 100:]. Other conventional constituents have been incorporated, such as ballistic modifiers.

The conventional composite propellant binders include functional polybutadienes such as hydroxy or carboxyterminated polybutadiene polymers, butadiene acrylic acid copolymers, butadiene acrylic acid acrylonitrile terpolymer, polyesters, polysulfides, polyurethanes, plastisols, etc. Other conventional constituents include metals such as aluminum and magnesium, metal organic compounds, metallic hydrides, and various ballistic modifiers, such as iron oxide, potassium perchlorate, and potassium dichromate.

Ammonium perchlorate whiskers used in the examples herein were nominal 40- diameter and nominal 3-p. diameter size. The larger diameter whiskers were prepared by feeding ammonium perchlorate solution below saturation through commercially available porous glass tubes. The nominal 3-p. diameter whiskers were formed by the process described in copending patent application Ser. No. 79,680 filed Oct. 9, 1970, which comprises feeding ammonium perchlorate solution through porous glass tubing which is carefully and thinly coated on the outside with silicone adhesive. Whiskers of varying size prepared by other means may be used.

The following examples illustrate the present invention:

EXAMPLE I Ingredients by weight Carboxyterminated polybutadiene prepolymers 24 (CTPB) Ammonium perchlorate (nominal 40p) 76 The ammonium perchlorate crystals used herein are characterized as being whisker-like orthorhombic single crystals without inclusions and having a length to diameter ratio of from about 5:] to about lOO1l. They were blended into the carboxyterrninated polybutadiene prepolymer in a conventional mixer to form a homogenous mixture which was cast and cured into predetermined shapes and tested. Samples of this formulation were also cast into burning rate strands, sections of which were cut parallel and perpendicular to the direction of extrusion to determine the whisker oxidizer orientation. At right angles to the direction of extrusion many of the crystals showed triangular cross-section, and a cut parallel to the direction of extrusion showed a columnar structure of the whiskers in the propellant.

EXAMPLE ll by weight Ingredients Carboxyterminated polybutadiene prepolymer Ammonium perchlorate (nominal 3p) Aluminum (nominal IS The above ingredients were processed as in Example I, and the mixture cast into preforms, cured and tested. A sample was thinned after mixing and prior to cure and dispersed sufficiently for optical examination under the microscope. It was noted that although the whiskers were broken during mixing, a length to diameter ratio ranging from 5:1 and l0:l was maintained.

EXAMPLE Ill Ingredients by weight Carboxyterminated polybutadiene prepolymer 24 Ammonium perchlorate (nominal 3p.) 76

EXAMPLE IV Ingredients 1: by Weight Carboxyterrninated polybutadiene prepolymer I 24 Ammonium perchlorate (15p. grind) 76 The ingredients were blended together in a conventional mixer and the homogeneous paste resulting therefrom was cast into burning rate strands. The strands were burned in the manner described hereinabove and burning times and temperatures were re- 3 corded and the burning rates were calculated and plotted.

1n the single FIGURE in the form of a graph there is shown comparative burning rates for propellant strands comprising the formulation (Example IV) containing commercial grind ammonium perchlorate designated curve A; the formulation (Example 1) containing nominal 40-;1. whisker ammonium perchlorate, designated curve B; and formulation (Example [11) containing nominal 3-11. whisker ammonium perchlorate, designated curve C. A sigmoid curve for the ground ammonium perchlorate formulation (Example 1V) is observed. All data acquired with the whisker formulations conform to the simple expression r aP (absence of sigmoid shape) where r is the burning rate, a is a constant, P is the pressure and n is the pressure exponent. The pressure exponents for curves B and C are 0.584 and 0.567, respectively. The difference in burning rates for curves B and C is attributed to the difference in effective particle size of the whisker ammonium perchlorate of the two formulations.

The comparison illustrates that the whisker ammonium perchlorate incorporated into a propellant fonnulation provides burning rates which conform to the sim plified linear rate equation and its resultant linear regression as plotted and shown in the single FIGURE. (Ground ammonium perchlorate gives a sigmoid buming rate pressure curve). The pressure exponent for the log rate vs. log pressure plot is constant, approximately 0.58. The burning rate of the propellant is apparently controlled by the diameter of the whiskers in that the rate increases with a decrease from 401.; to 3-1.. nominal whisker diameter. Although mixing the propellant formulation reduces the length-to-diameter ratio of the whiskers, the material is still capable of being oriented with an extrusion process.

Catalyzed ammonium perchlorate whiskers prepared by the process described in copending patent application Ser. No. 79,680 filed Oct. 9, 1970 referenced hereinbefore were also incorporated into conventional composite propellant binders. Predetermined amounts of catalytic materials incorporated into the ammonium perchlorate whiskers included such burning rate modifiers as potassium perchlorate, ammonium permanagnate, ammonium dichromate and iron oxide. Any burning rate modifier having ions which can be incorporated into the ammonium perchlorate crystals can be used. Several batches of propellant formulation comprising about 25 percent by weight carboxyterminated polybutadiene prepolymer and about percent catalyzed ammonium perchlorate whiskers were prepared, cast and cured. Some was extruded into burning rate strands and routinely tested. They showed unusual combustion properties such as higher burning rate exponent, were difficult to ignite and sustain burning at low pressure.

Both the ammonium perchlorate whiskers and the catalyzed ammonium perchlorate whiskers of micron and submicron diameter can be used in conjunction with a large variety of binders and fuels to produce an improved solid composite propellant grain.

What is claimed is:

l. A solid propellant formulation comprised of an oxidizer phase consisting of whisker-like crystals of ammonium perchlorate in combination with at least one solid propellant binder selected from the group consisting of hydroxy terminated polybutadiene, carboxy terminated polybutadiene butadiene acrylic acid copolymers, butadiene acrylic acid acrylonitrile terpolymer, polyesters, containing constituents selected from the group consisting of metals, metal organic compounds, metallic hyclrides, ballistic modifiers and combinations thereof.

2. The formulation in accordance with claim 1 wherein said whisker-like crystals are of varying dimensions ranging in a length to diameter ratio of from about 5:1 to about :1.

3. The formulation in accordance with claim 1 wherein said oxidizer phase consists of catalyzed ammonium perchlorate whiskers which consist essentially of ammonium perchlorate and a predetermined amount of a burning rate modifier.

4. The formulation in accordance with claim 3 wherein said burning rate modifier is a member selected from the group consisting of potassium perchlorate, ammonium permanganate, ammonium dichromate and iron oxide.

Claims

1. A SOLID PROPELLANT FORMULATION COMPRISED OF AN OXIDIZER PHASE CONSISTING OF WHISKERS-LIKE CRYSTAL OF AMMONIUM PERCHLORATE IN COMBUSTION WITH AT LEAST ONE SOLID PROPELLANT BINDER SELECTED FROM THE GROUP CONSISTING OF HYDROXY TERMINATED POLYBUTADINE, CARBOXY TERMINATED POLYBUTADINE BUTADIENE ACRYLIC ACID COPOLYMERS, BUTADIENE ACRYLIC ACID ACRYLONITRITE TEPOLYMER, POLYESTERS, CONTAINING CONSTITUENTS SELECTED FROM THE GROUP CONSISTING OF METALS, METAL ORGANIC COMPOUNDS, METALLIC HYCLRIDES, BALLISTIC MODIFERS AND COMBINATIONS THEREOF.

2. The formulation in accordance with claim 1 wherein said whisker-like crystals are of varying dimensions ranging in a length to diameter ratio of from about 5:1 to about 100:1.