Explosives (abbreviated as explosives) are special chemical compounds, as well as their mixtures, that can explode under the influence of external conditions or ongoing internal processes, while extremely hot gases are formed and heat is released. There are three groups of explosives with different susceptibility to external influences and different types of explosion. These include: initiating, propelling, as well as blasting substances. This article provides information about high explosives and their applications.
General concepts
An explosion is a rapid transformation of an explosive into a significant amount of extremely compressed and heated gases, which, expanding, do the following work: they move, crush, destroy, eject.
Explosive means a mechanical mixture or compounds of chemical elements that can quickly turn into gases. An explosion is similar to the burning of coal or firewood, but differs in the high speed of this process, which is often ten thousandths of a second. ATdepending on the speed of transformation, explosions are divided as follows:
- Combustion. The transfer of energy from one layer of matter to another is due to heat conduction. The process of combustion and the formation of gases proceeds at a low speed. Such an explosion is characteristic of gunpowder, in which the bullet is ejected, but the sleeve is not destroyed.
- Detonation. Energy is transferred from layer to layer almost instantly. Gases are formed at supersonic speeds, the pressure increases rapidly, and severe destruction occurs. Such an explosion is inherent in RDX, ammonite, TNT.
In order for the explosion process to start, an external impact on the explosive is required, which can be of the following types:
- detonation - an explosion next to another explosive;
- thermal - heating, spark, flame;
- chemical - chemical reaction;
- mechanical - friction, prick, impact.
Explosive-type substances react differently to external influences:
- some are able to explode quickly;
- others are only sensitive to certain effects;
- thirds can explode even without any effect on them.
Basic properties of BB
Their main properties are:
- susceptibility to external influences;
- brisance;
- characteristic aggregate state;
- amount of energy released by the explosion;
- chemical resistance;
- quick detonation;
- density;
- explosiveness;
- duration and circumstanceshe althy condition.
Each explosive can be described in detail using all its characteristics, but in most cases two of them are used:
- Brisance (break, crush, smash). That is, it is the ability of an explosive to produce destructive actions. The higher the brisance, the faster the gases are formed during the explosion and the explosion occurs with greater force. As a result, the body of the projectile will be well crushed, the fragments will scatter at high speed, and a strong shock wave will occur.
- Explosiveness is a measure of the efficiency of an explosive that performs destructive, throwing and other actions. The main influence on it is the volume of gas released during the explosion. A huge amount of gas can do a lot of work, for example, throw concrete, soil, bricks out of the explosion area.
High-explosive high-explosives are suitable for blasting in mines, during the elimination of ice jams, and the construction of various pits. In the manufacture of shells, first they pay attention to brisance, and explosiveness recedes into the background.
Classification
Explosives have several classifications. Based on their properties, they are classified as follows:
- Initiating - are used to undermine other explosives. They have a high sensitivity to initiation factors and have a higher detonation velocity. And also they are also called primary explosives, which are capable of exploding from a weak mechanical impact. To the groupincludes: diazodinitrophenol, mercury fulminate.
- High explosives - characterized by high brisance and are used as the main charge for most ammunition. These are secondary explosives that are less sensitive to external influences in relation to primary explosives. In their chemical composition, they contain nitrates and their compounds, have a powerful explosive effect. A small amount of initiating substances are used to explode them.
- Throwing - serve as a source of energy for throwing bullets, shells, grenades. These include various types of rocket fuels and gunpowder.
- Pyrotechnic compositions - used for special ammunition. Burning, they give a characteristic effect - signal, lighting.
In addition, according to their physical condition, they are:
- hard;
- liquid;
- gaseous;
- emulsion;
- suspensions;
- plastic;
- gelatinous;
- elastic.
Brazing BB
The brisant substances got their name from the French word briser, which in translation into Russian means to break, crush. Such explosives can be either separate chemical compounds - PETN, TNT, nitroglycerin, or mixtures - dynamites, dynamons, ammonites. They do not detonate from simple impulses: a beam of flame or a spark, which is enough to explode the initiating substances. The low susceptibility of blasting explosives to heat, friction and impact ensures safety whenworking with them. They are used for the manufacture of fragmentation and aviation bombs, sea and engineering mines, where a powerful explosion is needed with fragmentation of the projectile shell.
Power classification
High and initiating substances are used together. Detonation in secondary explosives is excited by the explosion of the primary explosive. Brisant explosives have increased, normal and reduced power.
Substances with increased power are most sensitive to external influences, so they are often used in mixtures with those that reduce sensitivity or have normal power. And they can also be used for intermediate detonators.
High power blasting materials
Explosives with increased power have a high detonation velocity and release a significant amount of heat during the explosion. They are very sensitive to external impulses.
Explosion occurs from any detonator, including the impact of a rifle bullet. When exposed to an open flame, they burn strongly, without emitting soot and smoke, with a bright flame, an explosion is possible. To this group of substances belongs:
- Teng is a white powder consisting of crystals. This blasting substance does not react with metals and water, is diluted in acetone and is considered the most vulnerable to external influences. It is used for detonation cords, auxiliary detonators and detonator caps.
- Tetryl is a yellowish crystalline powder with a s alty taste. It is well diluted with acetone and gasoline, badly with alcohol, it does not dissolve with metals.reacts, well gives in to pressing. Used to make detonators.
- RDX is one of the most brilliant substances, which consists of small white crystals, odorless and tasteless. It does not react with water and metals, it is poorly pressed. An explosion occurs from external influence, it burns with a hiss, a flame of bright white color. Used for some samples of blasting caps, making mixtures for industrial explosions, naval mines.
High explosives with normal power
These substances have a long shelf life (with the exception of dynamites), they are not significantly affected by external factors, in practical use they are safe.
High explosives include:
- TNT is a substance in the form of crystals, having a yellowish or brownish color, bitter in taste. The melting point is 81 °C, and the flash point is 310 °C. In the open air, the burning of TNT is accompanied by a yellowish flame with strong soot without explosion, and detonation can occur indoors. A substance with metals does not exhibit chemical activity, it is practically insensitive to shock, friction and thermal effects. It interacts with hydrochloric and sulfuric acid, gasoline, alcohol, and acetone. For example, when shot through, cast and pressed with a rifle bullet, TNT does not ignite, and no explosion occurs. For ammunition, it is used in various alloys and in its pure form. The substance is used in the form of pressed checkers of various sizes.when performing demolition work.
- Picric acid is a brisant substance in the form of crystals that have a yellow color and a bitter taste. It is more susceptible to heat, impact and friction than TNT, and can explode when shot through a rifle bullet. The flame smokes a lot when burning. With a large accumulation of matter, detonation occurs. Compared to TNT, picric acid is a more powerful explosive.
- Dynamites - have different formulations and contain nitroglycerin, nitroesters, s altpeter, wood flour and stabilizers. The main application is the national economy. The main property of dynamites is water resistance and significant power. Their disadvantage is considered to be increased susceptibility to thermal and mechanical influences. This requires exercise of caution during transportation and blasting. After six months, dynamites lose their ability to detonate. In addition, they freeze at a negative temperature of about 20 ° C and become dangerous during operation.
Reduced BB power
Low power brisant materials have reduced performance due to low detonation velocity and little heat. They are inferior in terms of brisance properties to those substances that have normal power, but have the same explosiveness. The most commonly used explosives from this group are made on the basis of ammonium nitrate. These include:
- Ammonium nitrate is a white or yellowish crystalline substance, which is a mineral fertilizer, perfectly soluble in water. She belongs to the insensitivelow explosives. It does not ignite from fire and sparks, the combustion process begins only in a strong focus of flame. The low cost of ammonium nitrate makes it possible to produce inexpensive explosives from it by adding explosives or combustible substances to it.
- Dynamons are a mixture of ammonium nitrate with combustible, but non-explosive substances, such as charcoal, peat or sawdust.
- Ammonals are mixtures for explosions containing s altpeter, with the addition of combustible and explosive additives and aluminum powder to increase the heat of explosion.
All types of high explosives based on ammonium nitrate are safe to use. They do not fly into the air when rubbed, hit, shot with a bullet from a rifle. Lit in air, they burn quietly, without exploding, with a yellow flame with soot. For storage, they are stored in well-ventilated areas. Sometimes fatty acids and iron sulfide are added to s altpeter, which contributes to the long-term residence of explosives in water without loss of properties.
Using high explosives
High explosives are secondary explosives, for which detonation is the main type of explosive transformation, excited due to a small charge of the initial explosive. They are endowed with the ability to crush and split. They are used for filling mines, various means for undermining, torpedoes and shells. Substances with explosive properties are a concentrated and economical source of mechanical energy. They are widely used in the national economy. Most of the non-ferrous ore, as well as almost the entire volume of ferrous metals, is mined using explosions.
High explosives have found their application in the following areas:
- to develop coal seams and mineral deposits;
- embankments for railways and roads;
- dam construction;
- digging water channels;
- laying gas and oil pipelines;
- development of mine shafts.
Where else are blasting substances used? In addition to the above, they are used:
- when compacting the soil;
- carrying out irrigation systems;
- fighting forest fires;
- leveling and clearing the area.
Research and development is also underway to expand the use of this powerful explosive energy - accelerating chemical processes using high pressures, artificial rainfall and blast drilling.
Chemistry and technology of high explosives
Molecules of chemical compounds or their mixtures, containing a certain amount of chemical energy, are called energy-saturated substances. Energy, as a result of the transformation that occurs under the influence of external factors, turns into light, mechanical or thermal.
Pyrotechnic compositions, gunpowder and other explosives are among the most famous types of energy-saturated substances. Chemical energy in them is converted due to the rapid flow of the explosion into other forms. Significant amountthe heat emitted due to the explosion is the main criterion for its performance. Being compact and powerful sources of mechanical energy, high explosives are widely used in various industries.
