Electrostatic discharge reduction in energetic compositions

• US 5,547,525 A
• Filed: 09/29/1993
• Issued: 08/20/1996
• Est. Priority Date: 09/29/1993
• Status: Expired due to Term

• Current Assignee: Alliant Techsystems Incorporated (Northrop Grumman Corporation)
• Original Assignee: Thiokol Corporation (Howmet Aerospace, Inc.)
• Inventors: Bennett, S. John, Hamilton, R. Scott
• Primary Examiner(s): Walsh, Donald P.
• Assistant Examiner(s): HARDEE, JOHN R
• Application Number:
  US08/128,793
• Time in Patent Office: 1,056 Days
• Field of Search: 149/19.1, 149/19.9, 149/19.91, 149/108.2, 149/109.6, 149/19.92, 428/367
• US Class Current: 149/19.1
• CPC Class Codes: C06B 23/001 Fillers, gelling and thickening agents (e.g. fibres) , absorbents for nitroglycerine binders, plasticisers for propellants C06B45/10; crosslinking or curing agents C06B45/10
• CPC Class Codes: C06B 45/10 the organic component containing a resin

Abstract

Conductive carbon fibrils are incorporated into energetic compositions to reduce electrostatic discharge susceptibility. The carbon fibrils are grown catalytically from carbon precursors and are substantially free of pyrolytically deposited thermal carbon. The fibrils generally have a length in the range from about 1μ to about 10μ and a diameter in the range from about 3.5 nanometers to about 75 nanometers. Length to diameter aspect ratios are greater than 5, and typically in the range from about 100:1 to about 1000:1. An effective amount of fibrils is included in the energetic compositions to decrease the resistivity to a level below or on the order of about 10¹⁰ ohm-cm. In most cases, fibril concentration will be in the range from about 0.005 to about 0.1 weight percent.

Claims

1. A propellant composition containing at least 75 weight percent solids in a nonpolar polymeric binder comprising an effective quantity of conductive carbon fibrils sufficient to provide a volume resistivity to a level below or on the order of about 10¹⁰ ohm-cm, wherein said carbon fibrils are present in the propellant composition in the range from about 0.005 to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.

2. A propellant composition as defined in claim 1, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

3. A propellant composition as defined in claim 1, wherein the carbon fibrils have a diameter in the range from about 3.5 nanometers to about 75 nanometers.

4. A propellant composition as defined in claim 1, wherein the carbon fibrils have an aspect ratio in the range from about 100:

1 to about 1000;

1.

5. A propellant composition as defined in claim 1, wherein the carbon fibrils include an inner core region.

6. A propellant composition as defined in claim 5, wherein the inner core region is hollow.

7. A propellant composition as defined in claim 5, wherein the inner core region contains amorphous carbon atoms.

8. A propellant composition as defined in claim 5, wherein the carbon fibrils possess concentric layers of graphitic carbon disposed substantially concentrically about the inner core region.

9. A propellant composition as defined in claim 1, wherein the solid propellant composition contains more than 85 weight percent solids.

10. A propellant composition as defined in claim 9, wherein the carbon fibrils are present in the range from about 0.01 to about 0.04 weight percent.

11. A propellant composition as defined in claim 10, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ and

a diameter in the range from about 3.5 nanometers to about 75 nanometers.

12. A propellant composition comprising conductive carbon fibrils present in the propellant composition in the range from about 0.005 weight percent to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.

13. An energetic composition as defined in claim 12, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

14. An energetic composition as defined in claim 12, wherein the carbon fibrils have a diameter in the range from about 3.5 nanometers to about 75 nanometers.

15. An energetic composition as defined in claim 12, wherein the carbon fibrils include an inner core region.

16. An energetic composition as defined in claim 15, wherein the inner core region is hollow.

17. An energetic composition as defined in claim 15, wherein the inner core region contains amorphous carbon atoms.

18. An energetic composition as defined in claim 15, wherein the carbon fibrils possess concentric layers of graphitic carbon disposed substantially concentrically about the cylindrical axis of the fibril.

19. A propellant composition containing at least 75% solids comprising conductive carbon fibrils having a diameter in the range from about 3.5 nanometers to about 75 nanometers, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon, wherein the carbon fibrils are present in the propellant composition in the range from about 0.01 to about 0.1 weight percent.

20. A propellant composition as defined in claim 19, wherein the carbon fibrils include an inner core region and possess concentric layers of graphitic carbon disposed substantially concentrically about said inner core region.

21. A propellant composition as defined in claim 19, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

22. A propellant composition containing at least 65 weight percent solids in a polar polymeric binder comprising conductive carbon fibrils having a diameter in the range from about 3.5 nanometers to about 75 nanometers, wherein said carbon fibrils are present in the propellant composition in the range from about 0.01 to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.

23. A propellant composition as defined in claim 22, wherein the carbon fibrils include an inner core region and possess concentric layers of graphitic carbon disposed substantially concentrically about said inner core region.

24. A propellant composition as defined in claim 22, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

25. A method for reducing electrostatic discharge susceptibility in a propellant composition containing at least 75 weight percent solids in a nonpolar polymeric binder comprising incorporating into said propellant composition an effective quantity of conductive carbon fibrils sufficient to provide a volume resistivity to a level below or on the order of about 10¹⁰ ohm-cm, wherein said carbon fibrils are incorporated into the propellant composition in the range from about 0.005 to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.

26. A method for reducing electrostatic discharge susceptibility as defined in claim 25, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

27. A method for reducing electrostatic discharge susceptibility as defined in claim 25, wherein the carbon fibrils have a diameter in the range from about 3.5 nanometers to about 75 nanometers.

28. A method for reducing electrostatic discharge susceptibility as defined in claim 25, wherein the solid propellant composition contains more than 85 weight percent solids.

29. A method for reducing electrostatic discharge susceptibility as defined in claim 28, wherein the carbon fibrils are present in the range from about 0.01 to about 0.04 weight percent.

30. A method for reducing electrostatic discharge susceptibility in an energetic composition comprising incorporating into said energetic composition conductive carbon fibrils in the range from about 0.005 weight percent to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.

31. A method for reducing electrostatic discharge susceptibility as defined in claim 30, wherein the carbon fibrils include an inner core region and possess concentric layers of graphitic carbon disposed substantially concentrically about said inner core region.

32. A method for reducing electrostatic discharge susceptibility as defined in claim 30, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

33. A method for reducing electrostatic discharge susceptibility as defined in claim 30, wherein the carbon fibrils have a diameter in the range from about 3.5 nanometers to about 75 nanometers.

34. A method for reducing electrostatic discharge susceptibility as defined in claim 30, wherein the energetic composition is a pyrotechnic composition.

35. A method for reducing electrostatic discharge susceptibility as defined in claim 30, wherein the energetic composition is a propellant composition.

36. A method for reducing electrostatic discharge susceptibility in propellant composition containing at least 75 weight percent solids comprising incorporating into said propellant composition conductive carbon fibrils having a diameter in the range from about 3.5 nanometers to about 75 nanometers, wherein said carbon fibrils are incorporated into the propellant composition in the range from about 0.01 to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.

37. A method for reducing electrostatic discharge susceptibility as defined in claim 36, wherein the carbon fibrils include an inner core region and possess concentric layers of graphitic carbon disposed substantially concentrically about said inner core region.

38. A method for reducing electrostatic discharge susceptibility as defined in claim 36, wherein the carbon fibrils have a length in the range from about 1μ

to about 10μ

.

39. A method for reducing electrostatic discharge susceptibility in a propellant composition containing at least 65 weight percent solids in a polar polymeric binder comprising incorporating into said energetic composition conductive carbon fibrils having a diameter in the range from about 3.5 nanometers to about 75 nanometers, wherein said carbon fibrils are incorporated into the propellant composition in the range from about 0.005 to about 0.1 weight percent, said carbon fibrils being catalytically grown and substantially free of pyrolytically deposited thermal carbon.