Liquid Explosives

Nitroglycerine is a colorless to pale-yellow, viscous liquid or solid (below 56F). It is an explosive ingredient in dynamite (20-40%) with ethylene glycol dinitrate (80-60%). It has a high nitrogen content( 18.5%) and contains more than enough oxigen atoms to oxidize the carbon and hydrogen atoms while nitrogen is beeing liberated, so it is one of the most powerful explosives known. Its detonation generates gases that would occupy more than 1,200 times the original volume at room temperature.

Astrolite explosives, frequently and not too precisely called the world's most powerful non-nuclear explosive, were discovered in the 1960's. Astrolite explosives are formed when ammonium nitrate is mixed with anhydrous hydrazine. This produces a clear liquid explosive called Astrolite G. When aluminum powder (100 mesh or finer) is added to the Hydrazinium Nitrate slurry, it forms Astrolite A-1-5. Astrolite G is a clear liquid explosive that produces a very high detonation velocity, almost twice as powerful as TNT.

Explosive compositions comprising nitromethane and a sensitizer for the nitromethane are well known in the art. These compositions are formed by combining nitromethane with a sensitizing chemical compound. Various chemical compounds serve as effective sensitizers for nitromethane. For example, liquid explosive compositions containing nitromethane sensitized with amines or polyamines such as diethylamine, triethylamine, ethanolamine, ethylenediamine and morpholine. Likewise, non-chemical, air entrapping structures, such as resin micro balloons and polymeric foam, are effective nitromethane sensitizers.

Nitromethane was first synthesized by Kolbe in 1872. It is so insensitive that it was not until 1938 that its detonation property was revealed by McKittrick. Once this detonation property was discovered, research was initiated to find sensitizers to increase its ease of detonation. World War II research produced sensitizers, primarily amines, which made nitromethane detonatable with a blasting cap. In 1945, Ericksen and Rowen listed over one dozen nitromethane - amine mixtures along with their explosive ability.

Normally, liquid nitromethane based explosive compositions are converted into a semi-solid or gelled state by the addition of a gelling agent. This conversion increases the density and, therefore, the detonation pressure of the semi-solid or gelled compositions. Although the semi-solid or gelled compositions have a higher detonation pressure than liquid compositions, they are not as effective in situations requiring a fluid material capable of conforming to any shape or structure. As a result, one must choose between the higher detonation pressure found in a semi-solid or gelled composition and the versatility of a liquid composition.

Nitromethane known to reduce the sensitivity of nitroglycerine. Nitromethane may be added to compositions containing nitroglycerine. The reference further teaches that trinitrotoluene may be added to said compositions. Pyridine is known to be a highly effective solvent for trinitrotoluene. It is also a well-known sensitizer for nitromethane; however, it is seldom used for its sensitizer properties because more effective sensitizers are known and available. Trinitrotoluene was found to be soluble in nitromethane. The US Army Ballistic Research Laboratory was not aware of this property until 1987.

In the field of explosives and explosives manufacturing, there are many types of explosives made for various applications. A few of these applications are for mining, construction, demolition, law enforcement and military uses. There are a multitude of explosive products available to satisfy the requirements in these fields. For example, for blasting rock in mining and construction work, the user can choose from cartridged explosives such as dynamite, water-gels and emulsions which are used for small diameter bore holes (up to 3 inches). For larger boreholes, blasting agents are used in the form of Ammonium Nitrate/Fuel Oil mixtures (ANFO), which are poured or pumped into position. Unlike the smaller, "cap-sensitive" cartridged explosives, these blasting agents (by definition) require a small, high explosive booster to initiate the detonation thereof.

For commercial demolition applications, cartridged explosives are placed in small boreholes within concrete columns and beams in the case of buildings, bridges and other similar structures. Where steel needs to be cut, small but powerful high explosive shaped charges are used to sever critical points in order to complete the demolition.

Military applications for explosives are many. However, they tend to fall into two main groups. The first is for bombs, artillery shells, mortars, mines, etc. For these uses, the explosives are generally placed into the devices by means of a melt-pour operation. The second group are explosives used for demolition and breaching by Special Forces and engineering groups. Although some of the explosive charges are pre-made devices incorporating shaped charge or Explosively Formed Projectile (EFP) technology, most are simply bulk explosives in the form of blocks (C-4, and TNT) or sheets (Deta-Sheet).

Another military related use of explosives is demining operations and unexploded ordnance (UXO) clearing operations where explosive charges are used to sympathetically detonate and destroy landmines as well as "dud" bombs and artillery shells. Similar type work conducted by civilian contractors after a conflict has been termed "Humanitarian Demining". Clearing of old military firing ranges by these contractors is called remediation.

Although the previously mentioned applications consume the bulk of the explosives used in the world, smaller quantities are also used for agricultural blasting such as tree stump removal, irrigation and drainage ditch blasting and beaver dam control; Avalanche control; Metal hardening; Forest fire fighting; Submarine (underwater) blasting; Seismic work; Secondary blasting such as boulder breaking; Law enforcement applications such as tactical breaching and bomb squad work.

Due to threats of terrorism and increased attention to accident prevention, regulations concerning the transportation, storage, use and transfer relating to explosives have steadily increased over the last few years. Along with this has come an increase in the cost of using explosives, particularly, in the area of transportation.

Where explosives are used in volume, such as mines and quarries, the cost of transporting a truckload of explosives is not much more than a truckload of any other material. However, where small amounts of explosives are required, the transportation costs can far exceed the cost of the product. For example, it costs just as much to transport one stick of dynamite by commercial truck as it does two thousand pounds of dynamite. In order to accommodate the user who needs smaller quantities to do a job, "binary" or "two-part" explosives are available. One popular brand is called Kinepak. As embodied in the commercially available product Kinepak, two individual, nonexplosive components are combined by the user to form a cap sensitive explosive. The first component, referred to as "the liquid" is predominantly nitromethane (NM). The other component, referred to as "the solid" is primarily finely divided ammonium nitrate (AN). The commercial product Kinepak is packaged in several different sizes and shapes of plastic bottles as well as foil pouches (bags) which are intended for various applications. In each case, the solid component container is supplied with an appropriate amount of premeasured liquid in another individual container.

The liquid component of the Kinepak is classified as a "Flammable Liquid" for transportation purposes. The solid component is classified as an "Oxidizer". Although both are considered hazardous materials, neither is defined as an explosive for transportation (U.S. Department of Transportation, DOT regulations) or storage (U.S. Bureau of Alcohol, Tobacco and Firearms, ATF regulations).

In order to use Kinepak, the liquid component is simply poured into the solid component. Within about five to fifteen minutes, the liquid (which is usually colored red) will soak down to the bottom of the container, as evidenced by the pink color. At this point, it has the consistency of moist powder and is a cap sensitive, high explosive. It can be used in most situations where it would be suitable to use cartridged explosives such as dynamite, water gels and small diameter emulsions.

Kinepak is used as an example here because it is, at the time of this writing, one of the only two commercially available two-component explosives. The only other known commercial product is marketed under the name Binex. Binex uses a two component system of an aqueous solution of sodium perchlorate and aluminum powder. When these two components are combined, a liquid explosive is formed that is cap sensitive. It is believed that this composition would not be a viable product as a replacement for cartridged explosives because of the high cost and the environmental concerns with the sodium perchlorate solution. However, there is a current military application where this product is used to blast fox holes in conjunction with an entrenchment kit for soldiers. It is known that this explosive has detonation velocity that is much lower than Kinepak and other commercial cartridged explosives. In the case of the military application, this is an advantage as lower velocity explosives are generally better for cratering in soil.

There are many other possible candidates for use as binary explosives. However, most of these others would not be viable for consideration as commercial products for the following reasons: toxicity of the components and/or detonation products; stability of the components before and after mixing; shelf life; cost; ease/difficulty of mixing; no advantages when compared to ammonium nitrate/nitromethane systems (Kinepak).

In most binary systems, one of the components is an oxidizer (ammonium nitrate, sodium perchlorate) and the other is a fuel (nitromethane, aluminum). As with all explosives, the potential uses and effects are determined by several properties such as detonation velocity, density, gas production, etc. Effects on a specific target can be influenced by container size, shape and confinement. For example, configuring the explosive in a shaped charge container will cause more of the available energy to be focused toward a given target than would be possible otherwise. The type of initiation system required and utilized will also have an effect, especially with blasting agents such as ANFO.

Ammonium nitrate and nitromethane (AN-NM) binary systems such as Kinepak work very well for their intended purpose. They have the following advantages over conventional explosives: The components are not explosives before mixing; The components do not have to be transported as explosives; The components do not have to be stored as explosives (in most places) therefore do not require expensive storage "magazines".

These advantages are due to the fact that they are mixed on site just before using. However, there are a few disadvantages: Mixing can be time consuming; Shelf life of the ammonium nitrate powder can be short depending on conditions, particularly temperature; Can cost 2 to 3 times more than conventional explosives .

Although other systems besides AN-NM exist, there has not been a commercially viable product available as a substitute for conventional small diameter cartridge explosives. There are other binary systems based on nitroparaffins such as nitromethane, nitroethane, nitropropanes, etc. These nitroparaffins are very interesting materials. Under the right circumstances, they can act as a fuel (as when combined with ammonium nitrate) an oxidizer or a stand alone explosive, especially nitromethane. However, they are too insensitive to be used as explosives as is.

There are ways to utilize nitroparaffins as the basis of a binary system. A stable explosive composition can be made by adding a sensitizer, in the form of resin balloons, to nitromethane. It is well known that amines (particularly ethylenediamine) will sensitize nitromethane so that it will detonate with a blasting cap. These mixtures become unstable and decompose after a few days. Most of these sensitizing agents are very toxic and difficult to work with safely. The basis of this patent is that by entrapping air into the nitromethane liquid, by means of micro balloons (resin, glass, etc.), it can be made cap-sensitive. However since the balloons will float to the surface of pure nitromethane, a thickening (gelling) agent must be added to prevent this.

A foamable nitromethane composition can be made by the addition of stabilizers, thickeners, sensitizing and foaming agents. It also teaches the addition of metals, including aluminum, to enhance the total energy of the system. The idea is that the foam would be applied to a mine field and then detonated. Two problems with this method is the very low density of the foam, thus low velocity. Another problem is the useable life of the foam after its application. This would greatly vary depending on conditions such as temperature, wind, sunlight, etc.

It is commonly known that the addition of aluminum to many explosive compositions (usually water gels) not only adds energy, but also increases its sensitivity. The addition of aluminum to typical water gel mixtures uses aluminum coated with stearic acid which give it a hydrophobic property. This causes air bubbles to cling to the surface of the aluminum particles. The incorporation of air bubbles into explosive mixtures increases the sensitivity.

Mixtures of nitromethane and nitroethane are used as an oxidizing liquid and aluminum fuel granules having an average particle size within the range of 1/64 to 1/4 inch and an average bulk density within the range of 0.2 to 1.0 grams/cc. The resultant explosive is a blasting agent requiring a one pound booster for initiation, not a cap sensitive, small diameter mixture.

Pure nitromethane is actually a very powerful explosive. However, without the addition of some additives or modifiers, it is so insensitive that it is classified as a "Flammable Liquid" for transportation purposes. Pure nitromethane will not usually detonate unless it is subjected to extreme shock and/or confinement at elevated temperatures. Most of the efforts to make a usable nitromethane based explosive have centered on adding dangerous amine compounds and/or incorporating entrapped air bubbles by some means. These air bubbles, while having the desired result of sensitization, have the undesired result of decreasing the density, and thereby lowering the velocity. Further, since these air bubble means are non-energetic, the per unit volume energy is also decreased.

Although ammonium nitrate and nitromethane systems provide a good product, a binary explosive with a higher velocity and total energy would be able to perform tasks that are currently not possible. There are many commercial and military applications where such an explosive would be very useful. If this new binary explosive was in liquid form after mixing, it would be particularly attractive because of its ability to be poured into and fill any container.

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