Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Reexamination Certificate
2000-10-27
2002-06-11
Miller, Edward A. (Department: 3641)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S019300, C149S019920, C149S022000, C149S108200, C149S108600
Reexamination Certificate
active
06402864
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to incendiary compositions. More particularly, the incendiary composition of the present invention contains a CTBN binder to improve ESD sensitivity of titanium/boron/polytetrafluoroethylene compositions. Most particularly, the CTBN binder is present in amounts of from about 10% or less combined with polytetrafluoroethylene in amounts of from about 20% or more.
2. Brief Description of the Related Art
Reducing the electrostatic discharge sensitivity (ESD) for dry metals is particularly important in the manufacture of incendiary devices. Highly reactive metals provide an excellent source for high burn temperatures, however, the more reactive the metal powders are, the more ESD sensitive they become. ESD sensitive metal powders are likely to ignite during handling or mixing, increasing hazards to personnel and manufacturing equipment. Combinations of titanium and boron potentially possess extremely high ESD sensitivity, with ignition of approximately 0.0084 joules possible. Other types of metallic mixtures that are less ESD sensitive, such as iron oxide and aluminum, i.e., Thermite, burn too quickly and with relatively low flame temperatures. Some combinations of magnesium, teflon and Viton A, e.g., MTV, have a high flame temperature, but they don't have the slow burning rate.
In view of the foregoing, there is a need for improved incendiary compositions for having a low slag, low ESD sensitivity and high flame temperature. The present invention addresses this need.
SUMMARY OF THE INVENTION
The present invention includes a low slag, high temperature incendiary composition 15 comprising a reactive material of titanium, a second reactive material of boron, an oxidizer of polytetrafluoroethylene in an amount of from about 20 weight percent or greater of the composition and a CTBN binder in an amount of from about 10 weight percent or less, wherein the ratio of titanium to boron ranges from about 81/19 to about 69/31.
The present invention also includes a method of producing a low slag, high temperature incendiary composition comprising the steps of mixing a first combination of a reactive material of titanium with a second reactive material of boron and an oxidizer of polytetrafluoroethylene, wherein the polytetrafluoroethylene comprises an amount of from about 20 weight percent or greater of the composition and the ratio of titanium to boron ranges from about 81/19 to about 69/31 and adding a CTBN binder in an amount of from about 10 weight percent or less to the first combination.
Additionally, the present invention includes a high flame temperature product from the process comprising the steps of providing an incendiary composition of titanium, boron, polytetrafluoroethylene in an amount of from about 20 weight percent or greater of the composition, with the ratio of titanium to boron ranges from about 81/19 to about 69/31, and adding a CTBN binder in an amount of from about 10 weight percent or less, and igniting the composition.
Furthermore, the present invention includes a low slag, high temperature incendiary composition product from the process comprising the steps of mixing a first combination of a reactive material of titanium with a second reactive material of boron and an oxidizer of polytetrafluoroethylene, wherein the polytetrafluoroethylene comprises an amount of from about 20 weight percent or greater of the composition and the ratio of titanium to boron ranges from about 81/19 to about 69/31 and adding a CTBN binder in an amount of from about 10 weight percent or less to the first combination.
The present invention provides an incendiary composition having a low slag and high flame temperature that is safer to handle and mix because of a reduced sensitivity to ESD.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention relates to incendiary compositions with improved electrostatic discharge (ESD) sensitivity. The incendiary compositions contain a carboxyl-terminated butadiene/acrylonitrile copolymer (CTBN) binder to improve ESD sensitivity of titanium, boron and polytetrafluoroethylene composition mixtures. The incendiary compositions are safe to handle, ignite readily, provide low slag and produce a very high flame temperature.
Safe ESD sensitivity for manufacture and handling of the present invention is in the range greater than 0.023 joules. The human body is capable of producing approximately 0.0084 joules. The high temperature incendiary composition of the present invention contains a reactive material of titanium, a second reactive material of boron, an oxidizer of polytetrafluoroethylene, which further includes a CTBN binder that increases the ESD resistance for the titanium/boron/polytetrafluoroethylene combination to a value of more than 0.023 joules.
Low slag for the present invention includes a slag percentage of less than 30% at a compaction of approximately 50% of the theoretical maximum density (TMD) of the composition. The slag is defined as the amount of solids that remain as a solid mass, at or near the location where the material is burned. A primary use for the present invention is to heat the air and surroundings to a high temperature. Therefore the hot particles produced from the burning need to transfer their heat to the air as quickly and efficiently as possible. The less solid slag produced, the more fine particles are ejected into the air and the more efficient is the transfer process.
Calculations show that mixture of the two reactive metals, titanium and boron, form an intermetallic compound together upon ignition. Solid titanium and boron react to form a liquid, i.e., molten, intermetallic compound, indicated by the formula:
Ti+2B→TiB
2
Other by-products occur, most significantly with the reaction of boron with polytetrafluoroethylene, and the reaction of the CTBN binder ingredients with titanium.
The titanium preferably comprises a particle size of from greater than 44 microns to about 150 microns, with ESD sensitivity increasing to unsafe levels below 44 microns and burn rates increasing beyond a slow burn rate above a particle size of from about 150 microns. Particle sizes of about 200 microns provide a burning rate of approximately 4.7 inches per minute or 321 grams per minute. Appropriate particle sizes for the titanium within the particle size range of from about 44 microns to about 150 microns may be used as determine by those skilled in the art for a given purpose in light of the disclosure herein. Boron particles may include any acceptable size, such as from about 0.5 microns to about 1 micron in size, as determined by one of ordinary skill in the art. The chemicals are commercially available in finely divided powders. Titanium powder metal is available from Atlantic Equipment Engineers of Bergenfield, N.J. under the catalog number TI-109, having a purity of 99.7%. Boron is available from Callery Chemical Company of Pittsburgh, Pa. under the tradename SB 95 having from about 95% to about 97% boron and from about 5% to about 3% magnesium oxide (MgO) or SB 90 having from about 90% to about 92% boron and from about 10% to about 8% magnesium oxide (MgO), with both products having an amorphous state with an average particles size of approximately 0.6 microns. Titanium amounts preferably include from about 41 weight percent to about 61 weight percent, and more preferably from about 51 weight percent to about 61 weight percent, with boron in amounts of from about 11 weight percent to about 24 weight percent, more preferably from about 14 weight percent to about 24 weight percent. For example, titanium may comprise approximately 60.75 weight percent and boron approximately 14.25 weight percent of the total composition.
The weight ratio amount of titanium to boron needed for a high flame temperatures range from about 81/19 to about 69/31. Preferably within this range, the titanium and boron are present in the composition in substantially stoichiometric proportions for forming the intermetallic compound. As the ratio of titan
Carpenter Pamela
Gill Robert C.
Gotzmer Carl
Schlegel Eric
Homer Mark
Miller Edward A.
The United States of America as represented by the Secretary of
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