Explosive compositions based on TNT (trinotrotoluene) having incorporated therein as desensitizer an ozokerite wax.
TNT-based explosive compositions have a tendency to exude low melting impurities such as dinitrotoluene and mononitrotoluene, as well as unsymmetrical isomers of trinitrotoluene. It is known that high molecular weight nitrocellulose has the propensity to accept these low melting impurities of the composition. As a result of substantially high uptake in this regard, relatively small amounts of the nitrocellulose are necessary to prevent exudation of the cast. Thus, the viscosity of the melt is not appreciably altered by the addition of such cellulosic additive and the pourability of the composition is maintained. It has also been found that by such addition of cellulosic material, an explosive cast is obtained having greater mechanical strength and enhanced heat resistance.
In addition to exudation, TNT-based explosive compositions tend to crack upon temperature cycling, decompose autocatalytically upon exposure to fire and explode or detonate when in a bomb or warhead configuration, and further tend to detonate on sudden impact. These drawbacks have been partially corrected in the past by using wax type coatings as desensitizers and process aids. Beeswax was used initially at a level of about 1 wt. percent to desensitize Composition B. Shortages of beeswax led to a search for substitutes which concentrated on paraffin wax, microcrystalline waxes and synthetic waxes. Such wax coatings are deposited irregularly as agglomerates onto the explosive composition. As such, wax coatings tend to separate from the explosive composition surface upon exposure to heat and create potential cook-off conditions.
The waxes employed heretofore are generally not soluble in TNT. In order to form an emulsion of the explosive and wax, emulsifying aids are often added, as for example, lecithin as an emulsifier. Dispersions of 5% or greater of paraffin wax in TNT-based explosives are not truly stable emulsions.
Accordingly, it is an object of the present invention to provide stable TNT/wax emulsions.
Other objects, aspects, and advantages of the invention will be apparent to those skilled in the art.
DESCRIPTION OF THE INVENTION
In accordance with the present invention there is provided an improved explosive composition comprising TNT and an ozokerite wax.
The explosive compositions of the present invention are based upon TNT and, as such, contain about 30 to 99.5 weight percent TNT, and about 0.5 to 25 weight percent of an ozokerite wax, preferably about 4 to 20 weight percent of wax, based upon the total composition weight. These compositions may also contain about 10 to 70 wt. percent of one or more solid, powdered components such as PETN, cyclic nitramines such as HMX and RDX, oxidizers such as ammonium nitrate, potassium nitrate, barium nitrate, lead nitrate, potassium perchlorate and ammonium perchlorate, aluminum powder, and the like. Additionally, these compositions comprise about 0.025 to 0.20 weight percent of an emulsifier, such as lecithin, and about 0.5 to 2.5 weight percent of a stabilizer, such as nitrocellulose or other thermoplastic resin of the cellulosic variety.
Ozokerite is a mineral wax having a specific gravity of about 0.89, which fuses at about 60.degree. to 80.degree. C. and is over 99% soluble in carbon disulfide.
The ozokerite wax, as well as the other components, can be incorporated in the explosive composition in any suitable manner, e.g., by addition to molten TNT directly or by premixing and/or precoating the various components and then mixing these components with the molten TNT.
It is presently preferred to premix the ozokerite wax, emulsifier and cellulosic stabilizer by adding the emulsifier and stabilizer to melted wax, with stirring, to form a homogeneous mixture, cast the mixture into sheets, and then break up the sheet into small chips. Such chips can conveniently be bagged and stored.
The following examples illustrate the invention:
EXAMPLE I
Preparation of wax composition
A wax composition containing 85 wt % ozokerite wax, 14 wt percent Class A nitrocellulose and 1 wt percent dry purified lecithin was prepared as follows:
1. Melt 85 g. of ozokerite 1410 at about 90.degree. C.
2. Add 1 g. dry lecithin to the melted wax.
3. Increase temperature to 110.degree. C.
4. Mix vigorously at 110.degree. C. for 45 minutes.
5. Cool the mixture to 90.degree. C.
6. Slowly add 14 g. (net wt) of alcohol-wet NC to the wax/lecithin mixture.
7. Mix for 20 minutes at 90.degree. C.
8. Increase temperature to 110.degree. C. and mix for 20 minutes.
9. Cast the mixture into sheets and when cooled, break into small chips.
EXAMPLE II
Preparation of Explosive Composition
An explosive composition containing 66 wt % TNT, 16 wt % of the wax composition of Example I and 18 wt % of powdered aluminum was prepared as follows:
1. Melt 66 parts of TNT at about 84.degree. C.
2. Add 16 parts of the wax composition chips of Example I to the melted TNT, with mixing, stirring until an emulsion forms between the TNT and the wax.
3. Slowly add 18 parts of Al powder (preheated to about 80.degree. C.).
4. Thoroughly mix the Al into the TNT/wax mixture, then cast into a suitable mold.
The Theoretical Maximum Density (TMD) of this composition was calculated to be 1.59 g/cc. This explosive composition when cast into an unconfined mold had a density of 1.53 g/cc (96% TMD).
The sensitivity characteristics of the above explosive composition is given along with the characteristics of other compositions in Table I, below.
TABLE I
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Impact Deto-
Formulation
P-50% Initiation
nation Critical
Test (TNT/ (cm) Pressure
Velocity
Dia
No. wax*/Al) 5 Kg wt (Kbar) (Km/sec)
(inch)
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1 100/0/0 55 14 6.9 0.6***
2 80/0/20 50 14 6.5 --
3 91/9**/0 170 25 6.6 <1.0
4 82/18**/0 >200 42 6.2 --
5 74/8/18 >200 30 6.3 0.50
6 70/12/18 >200 42 6.1 0.67
7 66/16/18 >200 50 6.0 0.88
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*85 parts wax, 14 parts NC, 1 part lecithin
**Type 1026 ozokerite wax; all others use Type 1410.
***Literature value
Ozokerite wax forms truly stable emulsions with TNT which solidify upon cooling. The viscosity of the emulsions increases with increasing concentrations of wax. The impact sensitivity height of the compositions also increases with increasing concentrations of wax. Below about 16 wt percent wax the emulsion appears to be a wax-in-TNT emulsion; above 16 wt percent wax the emulsion appears to be a TNT-in-wax emulsion.
Various modifications may be made to the present invention without departing from the spirit and scope of the invention.
