Like explosives. Explosives: principle of operation and main types. Start in liquid form
EXPLOSIVES (a. explosives, blasting agents; n. Sprengstoffe; f. explosifs; and. explosivos) are chemical compounds or mixtures of substances capable, under certain conditions, of an extremely fast (explosive) self-propagating chemical transformation with the release of heat and the formation of gaseous products.
Explosives can be substances or mixtures of any state of aggregation. Widespread use in the so-called condensed explosives, which are characterized by a high volumetric concentration of thermal energy. Unlike conventional fuels, which require an external gaseous supply for their combustion, such explosives release heat as a result of intramolecular decomposition processes or interaction reactions between constituent parts mixtures, products of their decomposition or gasification. The specific nature of the release of thermal energy and its transformation into kinetic energy explosion products and shock wave energy determines the main area of application of explosives as a means of crushing and destroying solid media (mainly) and structures and moving the crushed mass (see).
Depending on the nature of the external influence, chemical transformations of explosives occur: when heated below the self-ignition (flash) temperature - a relatively slow thermal decomposition; when ignited - combustion with the movement of the reaction zone (flame) through the substance with constant speed about 0.1-10 cm/s; with shock-wave action - detonation of explosives.
Classification of explosives. There are several signs of the classification of explosives: according to the main forms of transformation, purpose and chemical composition. Depending on the nature of the transformation under operating conditions, explosives are divided into propellant (or) and. The former are used in the combustion mode, for example, in firearms and rocket engines, the latter in the mode, for example, in ammunition and on. High explosives used in industry are called. Usually, only high explosives are classified as proper explosives. In chemical terms, the listed classes can be completed with the same compounds and substances, but processed differently or taken when mixed in different proportions.
By susceptibility to external influences, high explosives are divided into primary and secondary. Primary explosives include explosives that can explode in a small mass when ignited (rapid transition from combustion to detonation). They are also much more sensitive to mechanical stress than secondary ones. The detonation of secondary explosives is easiest to cause (initiate) by shock-wave action, and the pressure in the initiating shock wave should be of the order of several thousand or tens of thousands of MPa. In practice, this is carried out with the help of small masses of primary explosives placed in, the detonation in which is excited by a beam of fire and is transmitted by contact to a secondary explosive. Therefore, primary explosives are also called. Other types of external action (ignition, spark, impact, friction) lead to the detonation of secondary explosives only under special and difficult-to-regulate conditions. For this reason, the widespread and purposeful use of high explosives in the detonation mode in civil and military explosive technology began only after the invention of the blasting cap as a means of initiating detonation in secondary explosives.
According to the chemical composition, explosives are divided into individual compounds and explosive mixtures. In the first, chemical transformations during an explosion occur in the form of a monomolecular decomposition reaction. The end products are stable gaseous compounds, such as oxide and dioxide, water vapor.
In explosive mixtures, the transformation process consists of two stages: the decomposition or gasification of the components of the mixture and the interaction of the decomposition products (gasification) with each other or with particles of non-decomposing substances (for example, metals). The most common secondary individual explosives are nitrogen-containing aromatic, aliphatic heterocyclic organic compounds, including nitro compounds ( , ), nitroamines ( , ), nitroesters ( , ). Of the inorganic compounds, for example, ammonium nitrate has weak explosive properties.
The variety of explosive mixtures can be reduced to two main types: those consisting of oxidizers and combustibles, and mixtures in which the combination of components determines the operational or technological qualities of the mixture. Oxidizer-fuel mixtures are designed for the fact that a significant part of the thermal energy is released during the explosion as a result of secondary oxidation reactions. The components of these mixtures can be both explosive and non-explosive compounds. Oxidizing agents, as a rule, release free oxygen during decomposition, which is necessary for the oxidation (with heat release) of combustible substances or their decomposition products (gasification). In some mixtures (for example, metal powders contained as fuel), substances that emit not oxygen, but oxygen-containing compounds (water vapor, carbon dioxide) can also be used as oxidizing agents. These gases react with metals to release heat. An example of such a mixture is .
As combustibles, various kinds of natural and synthetic organic substances are used, which, during an explosion, emit products of incomplete oxidation (carbon monoxide) or combustible gases (, ) and solids(soot). The most common type of blasting explosive mixtures of the first type are explosives containing ammonium nitrate as an oxidizing agent. Depending on the type of fuel, they, in turn, are divided into, ammotols and ammonals. Less common are chlorate and perchlorate explosives, which include potassium chlorate and ammonium perchlorate as oxidizers, oxyliquites - mixtures of liquid oxygen with a porous organic absorber, mixtures based on other liquid oxidizers. Explosive mixtures of the second type include mixtures of individual explosives, such as dynamites; mixtures of TNT with RDX or PETN (pentolite), most suitable for manufacturing.
In mixtures of both types, in addition to the indicated components, depending on the purpose of the explosives, other substances can also be introduced to give the explosive some operational properties, for example, increasing the susceptibility to the means of initiation, or, conversely, reducing the sensitivity to external influences; hydrophobic additives - to make the explosive water resistant; plasticizers, flame retardant salts - to impart safety properties (see Safety explosives). The main operational characteristics of explosives (detonation and energy characteristics and physical and chemical properties of explosives) depend on the recipe composition of explosives and manufacturing technology.
The detonation characteristic of explosives includes detonation capability and susceptibility to detonation impulse. Reliability and reliability of blasting depend on them. For each explosive at a given density, there is a critical charge diameter at which the detonation propagates steadily along the entire length of the charge. A measure of the susceptibility of explosives to a detonation pulse is the critical pressure of the initiating wave and its duration, i.e. the value of the minimum initiating impulse. It is often expressed in terms of the mass of some primary explosive or secondary explosive with known detonation parameters. Detonation is excited not only by contact detonation of the initiating charge. It can also be transmitted through inert media. It has great importance for, consisting of several cartridges, between which there are jumpers made of inert materials. Therefore, for cartridge explosives, the rate of detonation transmission over a distance through various media (usually through air) is checked.
Energy characteristics of explosives. The ability of explosives to perform mechanical work during an explosion is determined by the amount of energy released in the form of heat during explosive transformation. Numerically, this value is equal to the difference between the heat of formation of the explosion products and the heat of formation (enthalpy) of the explosive itself. Therefore, the coefficient of conversion of thermal energy into work for metal-containing and safety explosives that form solid products (metal oxides, flame retardant salts) with high heat capacity during an explosion is lower than for explosives that form only gaseous products. On the ability of explosives to local crushing or blasting action of the explosion, see Art. .
Changes in the properties of explosives can occur as a result of physical and chemical processes, the influence of temperature, humidity, under the influence of unstable impurities in the composition of explosives, etc. Depending on the type of closure, a guaranteed period of storage or use of explosives is established, during which the normalized indicators either should not change, or their change occurs within the established tolerance.
The main indicator of safety in the handling of explosives is their sensitivity to mechanical and thermal influences. It is usually estimated experimentally in the laboratory using special methods. In connection with mass introduction mechanized methods of moving large masses of bulk explosives, they are subject to the requirements of minimal electrification and low sensitivity to the discharge of static electricity.
Historical reference. Black (smoky) gunpowder, invented in China (seventh century), was the first of the explosives. It has been known in Europe since the 13th century. From the 14th century gunpowder was used as a propellant in firearms. In the 17th century (for the first time in one of the mines in Slovakia) gunpowder was used in blasting in mining, as well as for equipping artillery grenades (explosive cores). The explosive transformation of black powder was excited by ignition in the explosive combustion mode. In 1884, French engineer P. Viel proposed smokeless powder. In the 18-19 centuries. a number of chemical compounds with explosive properties were synthesized, including picric acid, pyroxylin, nitroglycerin, TNT, etc., however, their use as blasting detonating explosives became possible only after the discovery by the Russian engineer D. I. Andrievsky (1865) and Swedish inventor A. Nobel (1867) explosive fuse (detonator cap). Prior to this, in Russia, at the suggestion of N. N. Zinin and V. F. Petrushevsky (1854), nitroglycerin was used in explosions instead of black powder in the explosive combustion mode. The explosive mercury itself was obtained as early as the end of the 17th century. and again by the English chemist E. Howard in 1799, but its ability to detonate was not known at that time. After the discovery of the phenomenon of detonation, high explosives were widely used in mining and military affairs. Among industrial explosives, initially according to the patents of A. Nobel, gurdynamites were most widely used, then plastic dynamites, powdered nitroglycerin mixed explosives. Ammonium nitrate explosives were patented as early as 1867 by I. Norbin and I. Olsen (Sweden), but their practical use as industrial explosives and for filling ammunition did not begin until World War I (1914–18). Safer and more economical than dynamites, they began to be used on an increasing scale in industry in the 30s of the 20th century.
After the Great Patriotic War 1941-45 ammonium nitrate explosives, initially predominantly in the form of finely dispersed ammonites, became the dominant type of commercial explosives in the CCCP. In other countries, the process of mass replacement of dynamites with ammonium nitrate explosives began somewhat later, approximately from the mid-1950s. From the 70s. the main types of industrial explosives are granular and water-containing ammonium nitrate explosives of the simplest composition, not containing nitro compounds or other individual explosives, as well as mixtures containing nitro compounds. Finely dispersed ammonium nitrate explosives have retained their importance mainly for the manufacture of militant cartridges, as well as for some special types of blasting. Individual explosives, especially TNT, are widely used for the manufacture of detonators, as well as for long-term loading of flooded wells, in pure form () and in highly water-resistant explosive mixtures, granular and suspension (water-containing). For deep apply and.
Each new generation is trying to outdo the previous generations in what is called stuffing for infernal machines and others, in other words - in search of a powerful explosive. It would seem that the era of explosives in the form of gunpowder is gradually leaving, but the search for new explosives does not stop. The smaller the mass of the explosive, and the greater its destructive power, the better it seems to military specialists. Robotics, as well as the use of small missiles and bombs of large lethal force on UAVs, dictates the intensification of the search for such an explosive.
Naturally, a substance that is ideal from a military point of view is unlikely to ever be discovered at all, but recent developments suggest that something close to such a concept can still be obtained. Close to perfect here means stable storage, high lethality, small volume, and easy transportation. We must not forget that the price of such an explosive must also be acceptable, otherwise the creation of weapons based on it can simply devastate the military budget of a particular country.
Developments already for a long time go around use chemical formulas substances such as trinitrotoluene, penthrite, hexogen and a number of others. However, "explosive" science can offer the full extent of novelties extremely rarely.
That is why the appearance of such a substance as hexantyrohexaazaisowurtzitane (the name - you will break your tongue) can be considered a real breakthrough in its field. In order not to break the language, scientists decided to give this substance a more digestible name - CL-20.
This substance was first obtained about 26 years ago - back in 1986 in the US state of California. Its peculiarity lies in the fact that the energy density in this substance is still the maximum in comparison with other substances. The high energy density of CL-20 and little competition in its production lead to the fact that the cost of such explosives today is simply astronomical. One kilogram of CL-20 costs about $1,300. Naturally, such a price does not allow the use of an explosive agent on an industrial scale. However, soon, experts believe, the price of this explosive may fall significantly, as there are options for an alternative synthesis of hexan- rohexaazaisowurtzitane.
If we compare hexantyrohexaazaisowurtzitane with the most effective explosive currently used for military purposes (octogen), then the cost of the latter is about one hundred dollars per kg. However, it is hexantyrohexaazaisowurtzitane that is more effective. The detonation velocity of CL-20 is 9660 m/s, which is 560 m/s more than that of HMX. The density of CL-20 is also higher than that of the same octogen, which means that everything should be in order with the prospects for hexanitrohexaazaisowurtzitane.
Drones are considered one of the possible directions in the application of the CL-20 today. However, there is a problem here, because the CL-20 is very sensitive to mechanical stress. Even the usual shaking, which may well occur with a UAV in the air, can cause a detonation of a substance. To avoid the explosion of the drone itself, the experts suggested using the CL-20 in integration with a plastic component that would reduce the level of mechanical impact. But as soon as such experiments were carried out, it turned out that hexane hexaaazaisowurtzitane (formula C6H6N12O12) greatly loses its “lethal” properties.
It turns out that the prospects for this substance are huge, but for two and a half decades no one has managed to dispose of it wisely. But the experiments continue today. American Adam Matzger is working on improving the CL-20, trying to change the shape of this matter.
Matzger decided to use crystallization from a common solution to obtain molecular crystals of a substance. As a result, they came up with a variant when 2 molecules of CL-20 account for 1 molecule of HMX. The detonation speed of this mixture is between the speeds of the two specified substances separately, but at the same time the new substance is much more stable than CL-20 itself and more efficient than HMX.
What is the most effective explosive in the world? ..
The nuclear age did not take away the palms from chemical explosives in terms of frequency of use, breadth of application - from the army to oil production, as well as ease of storage and transportation. They can be transported in plastic bags, hidden in ordinary computers, and even simply buried in the ground without any packaging with a guarantee that detonation will still occur. Unfortunately, until now, most of the armies on Earth use explosives against a person, and terrorist organizations - to strike against the state. Nevertheless, the ministries of defense remain the source and customer of chemical developments.
RDX
RDX is a high explosive based on nitramine. Its normal state of aggregation- fine-crystalline substance of white color without taste and smell. It is insoluble in water, non-hygroscopic and non-aggressive. Hexogen does not enter into a chemical reaction with metals and is poorly compressed. For the explosion of RDX, one strong blow or a bullet shot is enough, in which case it begins to burn with a bright white flame with a characteristic hiss. Combustion turns into detonation. The second name of hexogen is RDX, Research Department eXplosive - explosives of the research department.
High explosives- these are substances in which the rate of explosive decomposition is quite high and reaches several thousand meters per second (up to 9 thousand m / s), as a result of which they have a crushing and splitting ability. Their predominant type of explosive transformations is detonation. They are widely used for loading shells, mines, torpedoes and various explosives.
Hexogen is obtained by nitrolysis of hexamine with nitric acid. During the production of hexogen by the Bachmann method, hexamine reacts with nitric acid, ammonium nitrate, glacial acetic acid, and acetic anhydride. The raw material consists of hexamine and 98-99% nitric acid. However, this complex exothermic reaction is not completely controllable, so the end result is not always predictable.
RDX production peaked in the 1960s, when it was the third largest explosives production in the US. The average volume of RDX production from 1969 to 1971 was about 7 tons per month.
Current U.S. RDX production is limited to military use at the Holston Ammunition Plant in Kingsport, Tennessee. In 2006, the Army Ordnance Plant in Holston produced over 3 tons of RDX.
RDX molecule
RDX has both military and civilian applications. As a military explosive, RDX can be used alone as the main charge for detonators, or mixed with another explosive such as TNT to form cyclothols, which create an explosive charge for air bombs, mines, and torpedoes. RDX is one and a half times more powerful than TNT, and it is easy to activate it with mercury fulminate. A common military use of RDX is as an ingredient in plastid-bonded explosives that have been used to fill almost all types of ammunition.
In the past, by-products of military explosives such as RDX were openly burned in many of the Army's munitions factories. There is written evidence that up to 80% of ammunition and rocket fuel waste over the past 50 years has been disposed of in this way. The main disadvantage of this method is that explosive contaminants often end up in air, water and soil. Ammunition from RDX has also previously been disposed of by dumping into deep sea waters.
Octogen
Octogen- also a high explosive, but it already belongs to the group of high-power explosives. According to American nomenclature, it is designated as HMX. There is much conjecture as to what the acronym stands for: High Melting eXplosive, or High-Speed Military eXplosive, high-speed military explosive. But there are no records confirming these conjectures. It could just be a code word.
Initially, in 1941, HMX was simply a by-product in the production of RDX by the Bachmann method. The HMX content in such hexogen reaches 10%. Minor amounts of HMX are also present in RDX produced by the oxidative process.
In 1961, Canadian chemist Jean-Paul Picard method of obtaining HMX directly from hexamethylenetetramine. The new method made it possible to obtain an explosive with a concentration of 85% with a purity of more than 90%. The disadvantage of the Picard method is that it is a multi-stage process - it takes quite a long time.
In 1964, Indian chemists developed a one-step process, thereby greatly reducing the cost of HMX.
HMX, in turn, is more stable than RDX. It ignites at a higher temperature - 335°C instead of 260°C - and has the chemical stability of TNT or picric acid, plus it has a faster detonation velocity.
HMX is used where its high power exceeds the cost of its acquisition - about $ 100 per kilogram. For example, in missile warheads, a smaller charge of a more powerful explosive allows the missile to move faster or have a longer range. It is also used in shaped charges to penetrate armor and overcome defensive barriers where a less powerful explosive might not be able to cope. HMX as a blasting charge is most widely used in blasting in particularly deep oil wells, where there are high temperatures and pressures.
HMX is used as an explosive when drilling very deep oil wells.
In Russia, HMX is used for perforating and blasting operations in deep wells. It is used in the manufacture of heat-resistant gunpowder and in heat-resistant electric detonators TED-200. HMX is also used to equip the DSHT-200 detonating cord.
HMX is transported in waterproof bags (rubber, rubberized or plastic) in the form of a pasty mixture or in briquettes containing at least 10% liquid, consisting of 40% (weight) isopropyl alcohol and 60% water.
A mixture of HMX with TNT (30 to 70% or 25 to 75%) is called octol. Another mixture called okfol, which is a uniform loose pink to crimson powder, is 95% HMX desensitized with 5% plasticizer, which causes the detonation velocity to drop to 8,670 m/s.
Solid desensitized explosives wetted with water or alcohols or diluted with other substances to suppress their explosive properties.
Liquid desensitized explosives are dissolved or suspended in water or other liquid substances to form a homogeneous liquid mixture in order to suppress their explosive properties.
Hydrazine and Astrolite
Hydrazine and its derivatives are extremely toxic to various types of animal and plant organisms. Hydrazine can be obtained by reacting an ammonia solution with sodium hypochlorite. Sodium hypochlorite solution is better known as whiteness. Dilute solutions of hydrazine sulfate have a detrimental effect on seeds, algae, unicellular and protozoa. In mammals, hydrazine causes convulsions. Hydrazine and its derivatives can penetrate into the animal body in any way: by inhalation of product vapors, through the skin and digestive tract. For humans, the degree of toxicity of hydrazine has not been determined. It is especially dangerous that the characteristic smell of a number of hydrazine derivatives is felt only in the first minutes of contact with them. In the future, due to the adaptation of the olfactory organs, this sensation disappears and a person, without noticing it, can be in an infected atmosphere for a long time, containing toxic concentrations of the named substance.
Invented in the 1960s by chemist Gerald Hurst at Atlas Powder, astrolite is a family of binary liquid explosives that are formed by mixing ammonium nitrate and anhydrous hydrazine (propellant). A transparent liquid explosive called Astrolite G has a very high detonation velocity of 8,600 m/s, almost twice that of TNT. In addition, it remains explosive in almost all weather conditions, as it is well absorbed into the ground. Field tests showed that Astrolite G detonated even after four days in the soil in heavy rain.
Tetranitropentaerythritol
Pentaerythritol Tetranitrate (PETN, PETN) is a pentaerythritol nitrate ester used as an energy and filler material for military and civilian applications. The substance is produced as a white powder and is often used as an ingredient in plastic explosives. It is widely used by the rebel forces and was probably chosen by them because it is very easy to activate.
Appearance heating element
PETN retains its properties during storage longer than nitroglycerin and nitrocellulose. At the same time, it easily explodes with a mechanical impact of a certain force. It was first synthesized as a commercial explosive device after World War I. It has been praised by both military and civilian experts primarily for its destructive power and effectiveness. It is placed in detonators, explosive caps and fuses to propagate a series of detonations from one explosive charge to another. A mixture of approximately equal parts of PETN and trinitrotoluene (TNT) creates a powerful military explosive called pentolite, which is used in grenades, artillery shells, and shaped charge warheads. The first pentolith charges were fired from old bazooka-type anti-tank weapons during World War II.
Pentolite explosion in Bogotá
On January 17, 2019, in the capital of Colombia, Bogota, an SUV stuffed with 80 kg of pentolite crashed into one of the buildings of the General Santander police cadet school and exploded. The explosion killed 21 people, injured, according to official figures, there were 87. The incident was qualified as a terrorist act, as the car was driven by a former bomber of the Colombian rebel army, 56-year-old José Aldemar Rojas. The Colombian authorities blamed the bombing in Bogota on a radical left organization with which they have been negotiating unsuccessfully for the past ten years.
Pentolite explosion in Bogotá
PETN is often used in terrorist attacks due to its explosive power, ability to be placed in unusual packages, and the difficulty of detecting with X-ray and other conventional equipment. An electrically activated percussion-type detonator can be detected during routine airport screening if carried on the bodies of suicide bombers, but it can be effectively hidden in an electronic device in the form of a packet bomb, as happened in the 2010 attempted bombing of a cargo plane. At that time, computer printers with cartridges filled with heating elements were intercepted by security forces only because the special services, thanks to informants, already knew about the bombs.
Plastic explosives- mixtures that are easily deformed even from minor efforts and retain their shape for an unlimited time at operating temperatures.
They are actively used in demolition for the manufacture of charges of any given shape directly at the site of blasting. Plasticizers are rubbers, mineral and vegetable oils, resins. Explosive components are hexogen, octogen, pentaerythritol tetranitrate. The plasticization of an explosive can be carried out by introducing mixtures of cellulose nitrates and substances that plasticize cellulose nitrates into its composition.
Tricyclic urea
In the 80s of the last century, the substance tricyclic urea was synthesized. It is believed that the first to receive this explosive were the Chinese. Tests showed the enormous destructive power of urea - one kilogram of it replaced 22 kg of TNT.
Experts agree with such conclusions, since the "Chinese destroyer" has the highest density of all known explosives and at the same time has the highest oxygen ratio. That is, during the explosion, absolutely all the material is burned. By the way, for TNT it is 0.74.
In reality, tricyclic urea is not suitable for military operations, primarily due to poor hydrolytic stability. The very next day, with standard storage, it turns into mucus. However, the Chinese managed to get another "urea" - dinitrourea, which, although worse in explosiveness than the "destroyer", is also one of the most powerful explosives. Today it is produced by the Americans at their three pilot plants.
The ideal explosive is a balance between maximum explosive power and maximum stability during storage and transport. Yes, and the maximum density of chemical energy, low cost in production and, preferably, environmental safety. It is not easy to achieve all this, therefore, for developments in this area, they usually take already proven formulas and try to improve one of the desired characteristics without compromising the rest. Completely new compounds appear extremely rarely.
explosives (explosives) are called unstable chemical compounds or mixtures that extremely quickly pass under the influence of a certain impulse into other stable substances with the release of a significant amount of heat and a large volume of gaseous products that are under very high pressure and, expanding, perform one or another mechanical work.
Modern explosives are either chemical compounds (hexogen, trotyl, etc..), or mechanical mixtures(ammonium nitrate and nitroglycerine explosives).
Chemical compounds obtained by treatment with nitric acid (nitration) of various hydrocarbons, i.e., the introduction of substances such as nitrogen and oxygen into the hydrocarbon molecule.
Mechanical mixtures are made by mixing substances rich in oxygen with substances rich in carbon.
In both cases, oxygen is in a bound state with nitrogen or chlorine (the exception is oxyliquites where oxygen is in the free unbound state).
Depending on the quantitative content of oxygen in the explosive, the oxidation of combustible elements in the process of explosive transformation can be complete or incomplete, and sometimes oxygen may even remain in excess. In accordance with this, explosives are distinguished with excess (positive), zero and insufficient (negative) oxygen balance.
The most beneficial are explosives that have a zero oxygen balance, since carbon is completely oxidized to CO 2, and hydrogen to H 2 O, resulting in the release of the maximum possible amount of heat for a given explosive. An example of such an explosive is dinaphthalite, which is a mixture of ammonium nitrate and dinitronaphthalene:
At excess oxygen balance the remaining unused oxygen enters into combination with nitrogen, forming highly toxic nitrogen oxides, which absorb some of the heat, which reduces the amount of energy released during the explosion. An example of an explosive with excess oxygen balance is nitroglycerine:
On the other hand, when insufficient oxygen balance not all carbon goes into carbon dioxide; some of it is oxidized only to carbon monoxide. (CO) which is also poisonous, although to a lesser extent than nitrogen oxides. In addition, some of the carbon may remain in solid form. The remaining solid carbon and its incomplete oxidation only to CO lead to a decrease in the energy released during the explosion.
Indeed, during the formation of one gram-molecule of carbon monoxide, only 26 kcal / mol of heat is released, while during the formation of a gram-molecule carbon dioxide 94 kcal/mol.
An example of an explosive with a negative oxygen balance is TNT:
In real conditions, when the explosion products perform mechanical work, additional (secondary) chemical reactions and the actual composition of the explosion products is somewhat different from the calculation schemes given, and the amount of toxic gases in the explosion products changes.
Classification of explosives
Explosives may be in gaseous, liquid and solid state or in the form of mixtures of solid or liquid substances with solid or gaseous substances.
At present, when the number of different explosives is very large (thousands of items), dividing them only according to their physical state is completely insufficient. Such a division does not say anything about the performance (power) of explosives, by which it would be possible to judge the scope of one or another of them, or about the properties of explosives, by which one could judge the degree of danger of their handling and storage. . Therefore, three other classifications of explosives are currently accepted.
According to the first classification all explosives are divided according to their power and scope into:.
A) increased power (heater, hexogen, tetryl);
B) normal power (TNT, picric acid, plastites, "tetritol, rocky ammonites, ammonites containing 50-60% TNT, and gelatinous nitroglycerin explosives);
C) reduced power (ammonium nitrate explosives, except for those mentioned above, powdered nitroglycerin explosives and chloratites).
3. Throwable explosives(smoky powders and smokeless pyroxylin and nitroglycerin powders).
In this classification, of course, not all the names of explosives are given, but only those that are mainly used in blasting. In particular, under the general name of ammonium nitrate explosives there are dozens of different compositions, each with its own separate name.
Second classification divides explosives according to their chemical composition:
1. Nitro compounds; substances of this type contain two to four nitro groups (NO 2); these include tetryl, trotyl, hexogen, tetritol, picric acid and dinitronaphthalene, which is part of some ammonium nitrate explosives.
2. Nitroesters; substances of this type contain several nitrate groups (ONO 2). These include heating elements, nitroglycerin explosives and smokeless powders.
3. Salts of nitric acid- substances containing the NO 3 group, the main representative of which is ammonium (ammonium) nitrate NH 4 NO 3, which is part of all ammonium nitrate explosives. This group also includes potassium nitrate KNO 3 - the basis of black powder, and sodium nitrate NaNO 3, which is part of nitroglycerin explosives.
4. Salts of hydronitrous acid(HN 3), of which only lead azide is used.
5. Salts of fulminic acid(HONC), of which only mercury fulminate is used.
6. Salts of chloric acid, the so-called chloratites and perchloratites, - explosives, in which the main component - the carrier of oxygen is potassium chlorate or perchlorate (KClO 3 and KClO 4); now they are used very rarely. Apart from this classification is an explosive called oxyliquit.
According to the chemical structure of the explosive, one can also judge its main properties:
Sensitivity, resistance, composition of the explosion products, therefore, the power of the substance, its interaction with other substances (for example, with the shell material) and a number of other properties.
The nature of the bond between nitro groups and carbon (in nitro compounds and nitro esters) determines the sensitivity of the explosive to external influences and their stability (retention of explosive properties) under storage conditions. For example, nitro compounds, in which the nitrogen of the NO 2 group is bonded directly to carbon (C-NO 2), are less sensitive and more stable than nitro esters, in which nitrogen is bonded to carbon through one of the oxygens of the ONO 2 group (C-O-NO 2 ); such a bond is less strong and makes the explosive more sensitive and less resistant.
The number of nitro groups contained in the explosive characterizes the power of the latter, as well as the degree of its sensitivity to external influences. The more nitro groups in the explosive molecule, the more powerful and sensitive it is. For example, mononitrotoluene(having only one nitro group) is an oily liquid that does not have explosive properties; dinitrotoluene, containing two nitro groups, is already an explosive, but with weak explosive characteristics; and finally trinitrotoluene (TNT), having three nitro groups, is an explosive that is quite satisfactory in terms of power.
Dinitro compounds are of limited use; Most modern explosives contain three or four nitro groups.
The presence of some other groups in the composition of the explosive also affects its properties. For example, additional nitrogen (N 3) in hexogen increases the sensitivity of the latter. The methyl group (CH 3) in TNT and tetryl contributes to the fact that these explosives do not interact with metals, while the hydroxyl group (OH) in picric acid is the reason for the easy interaction of the substance with metals (except tin) and the appearance of so-called picrates of one or more other metal, which are explosives that are very sensitive to impact and friction.
Explosives obtained by replacing hydrogen with a metal in hydrazoic or fulminic acid cause the extreme fragility of intramolecular bonds and, consequently, the special sensitivity of these substances to mechanical and thermal external influences.
At blasting in everyday life, a third classification of explosives is adopted: - according to the admissibility of their use in certain conditions.
According to this classification, the following three main groups are distinguished:
1. Explosives approved for open work.
2. Explosives approved for underground work in conditions that are safe, if possible, from an explosion of firedamp and coal dust.
3. Explosives approved only for conditions that are dangerous for the possibility of a gas or dust explosion (safety explosives).
The criterion for assigning an explosive to one or another group is the amount of poisonous (harmful) gases released during the explosion and the temperature of the explosion products. So, TNT, due to the large amount of poisonous gases formed during its explosion, can only be used in open works ( construction and quarry mining), while ammonium nitrate explosives are allowed both in open and underground works in conditions that are not hazardous in terms of gas and dust. For underground work, where the presence of exploding gas and dust-air mixtures is possible, only explosives with a lower temperature of the explosion products are allowed.
