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
2002-11-26
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, C149S022000, C149S108200
Reexamination Certificate
active
06485586
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 paraffin wax as a binder to improve ESD sensitivity of titanium/boron/polytetrafluoroethylene compositions. Most particularly, the paraffin wax is present in amounts of from about 5% to about 20%.
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, i.e., MTV, high 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 having a reduced burning rate, low ESD sensitivity and high flame temperature. The present invention addresses this need.
SUMMARY OF THE INVENTION
The present invention includes a high temperature incendiary composition 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 binder of paraffin wax in an amount of from about 5 weight percent to about 20 weight percent, wherein the ratio of titanium to boron ranges from about 81/19 to about 69/31.
Additionally, the present invention includes a high flame temperature product from the process comprising the steps of providing a composition of titanium, boron, polytetrafluoroethylene in an amount of from about 20 weight percent or greater of the composition and paraffin wax in an amount of from about 5 weight percent to about 20 weight percent, wherein the ratio of titanium to boron ranges from about 81/19 to about 69/31 and igniting the composition.
The present invention provides an incendiary composition having a slow burn rate 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 paraffin wax binder to improve ESD sensitivity of titanium, boron and polytetrafluoroethylene composition mixtures. The incendiary compositions are safe to handle, ignite readily, burn at a low and controlled rate and produce a very high flame temperature.
Safe ESD for manufacture and handling of the present invention is in a range greater than 0.023 joules. The human body is capable of producing up to 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 binder of paraffin wax that increases the ESD resistance for the titanium/boron/polytetrafluoroethylene combination to a value of more than 0.023 joules and a burning rate of from about 1.0 inch per minute or less.
The composition preferably comprises fine or integrated mixtures of the titanium and boron metals, rather than mere individual aggregates, granules or pellets of the separate metals. The metals are preferably pure form, containing no oxides or other chemical forms. On ignition, the titanium and boron react exothermically together to result in intermetallic compound with a heat energy release of from about 1000 calories per gram. As the purity of the two metals increase, the energy release from the exothermic reaction also increases. Impurities promote side reactions, create stoichiometric imbalances, and dissipate released energy.
Calculations show the mixture of the two reactive metals or titanium and boron forms 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 paraffin wax with titanium.
The titanium preferably comprises a particle size of from about 44 microns to about 150 microns, with ESD sensitivity increasing to unsafe levels below from about 44 microns and burn rates increasing beyond a slow burn rate above a particle size of from about 150 microns. Particle sizes from 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 determined 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 approximately 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 particle size of approximately 0.6 microns.
The weight ratio amount of titanium to boron needed for a high flame temperatures ranges 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 intemetallic compound. As the ratio of titanium to boron decreases, the combination metal becomes increasingly more difficult to ignite, with the proper ratio of titanium to boron for a given incendiary composition determinable by those skilled in the art in light of the disclosure herein.
The incendiary composition includes an oxidizer of polytetrafluoroethylene, also known as Teflon®, in an amount of from about 20 weight percent or greater of the composition. Preferred amounts of polytetrafluoroethylene range from about 20 weight percent to about 30 weight percent, with more preferred amounts of polytetrafluoroethylene ranging from about 20 weight percent to about 25 weight percent. The particles of the polytetrafluoroethylene may be any suitable size, such as from about 20 microns to about 450 micron, with little affect on the burning rate or slag percentage. For example, a polytetrafluoroethylene particle size between 20 microns and 450 microns in a given composition may vary in burning rates between from about 163 grams per minute to about 161 grams per minute with a slag percentage varying between from about 36% to about 40%. As the amount of polytetrafluoroethylene increases, the reaction energy of the titanium/boron ignition decreases, with the proper amount of polytetrafluoroethylene for a given incendiary composition determinable by those skilled in the art in light of the disclosure herein. Polytetrafluoroethylene is available from E. I. duPont de Nemours & Company of Wilmington, Del. under the tradename—Teflon® 7C.
The paraffin wax binder is included within the incendiary composition in an amount of from about 5 weight percent to about 20 weight
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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