Explosives (explosive in abbreviated form) are special chemical compounds, as well as their mixtures, which are capable of exploding under the influence of external conditions or internal processes taking place, and extremely heated gases are formed and heat is generated. There are three groups of explosives that have different susceptibilities to external influences and different types of explosions. These include: initiating, propellant, and also brisant substances. This article provides information on blasting explosives and their fields of application.
General concepts
An explosion is the rapid transformation of an explosive into a significant amount of extremely compressed and heated gases, which, expanding, perform the following work: they move, crush, destroy, throw them away.
Explosive means a mechanical mixture or compounds of chemical elements that can quickly be converted to gases. An explosion is similar to the burning of coal or firewood, but it is distinguished by a high speed of this process, which often amounts to ten thousandths of a second. Explosions are divided as follows depending on the rate of conversion:
- Combustion. The transfer of energy from one layer of a substance to another takes place due to thermal conductivity. With a small speed, the process of combustion and the occurrence of gases proceeds. Such an explosion is characteristic of gunpowder, in which a bullet is ejected, but the sleeve does not collapse.
- Detonation. Energy is transferred from layer to layer almost instantly. Gases form at a supersonic speed, pressure increases rapidly, and severe destruction occurs. Such an explosion is inherent in RDX, ammonite, and TNT.
In order for the explosion process to begin, an external effect 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, pricking, impact.
Explosive-type substances react differently to external influences:
- some are capable of exploding quickly;
- others are sensitive only to a certain effect;
- still others may explode without any influence on them.
The main properties of explosives
Their main properties are:
- susceptibility to external influences;
- brisance;
- characteristic state of aggregation;
- the amount of energy released during the explosion;
- chemical resistance;
- detonation swiftness;
- density;
- high explosiveness;
- duration and circumstances of a healthy state.
Each explosive can be described in detail using all its characteristics, but in most cases two of them are used:
- Brisance (breaking, crushing, breaking). 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 shell of the shell will be well fragmented, the fragments will fly apart at high speed, and a strong shock wave will occur.
- High explosiveness is a measure of the working capacity of an explosive that performs destructive, propellant and other actions. The main influence on it is exerted by the volume of gas released during the explosion. A huge amount of gas is capable of carrying out a lot of work, for example, throwing concrete, soil, brick from the explosion area.
High explosive blasting explosives are suitable for blasting in mines, in the elimination of ice jams, the construction of various pits. In the manufacture of shells, they first pay attention to brisance, and the explosiveness recedes into the background.
Classification
Explosives have several classifications. Based on their properties, they are divided as follows:
- Initiators - are used to undermine other explosives. They are highly sensitive to initiation factors and have a greater detonation velocity. And they are also called primary explosives, which are capable of exploding from weak mechanical impact. The group includes: diazodinitrophenol, explosive mercury.
- High explosives are characterized by great high explosiveness and are used as the main charge for most of the ammunition. These are secondary explosives that are less sensitive to external influences with respect to primary explosives. In their chemical composition they contain nitrates and their compounds, have a powerful explosive effect. For their explosion using a small amount of initiating substances.
- 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, in physical condition they are:
- solid;
- liquid;
- gaseous;
- emulsion;
- suspensions;
- plastic;
- gel-like;
- elastic.
Blasting explosives
Brisant substances got their name from the French word briser, which in Russian means breaking, crushing. Such explosives can be either separate chemical compounds - ten, trotyl, nitroglycerin, or mixtures - dynamites, dynamons, ammonites. They do not detonate from simple impulses: a ray of flame or a spark, which is enough for an explosion of initiating substances. The low susceptibility of blasting explosives to the effects of heat, friction and shock ensures safety when working with them. They are used for the manufacture of fragmentation and aircraft bombs, sea and engineering mines, where a powerful explosion with crushing of the shell of the shell is needed.
Power Classification
The brisant and initiating substances are used together. Detonation in secondary explosives is excited by the explosion of a primary explosive. Blasting explosives have increased, normal and reduced power.
Substances with high power are most sensitive to external influences, so they are often used in mixtures with reducing sensitivity or having normal power. They can also be used for intermediate detonators.
High power brisant substances
Explosives with increased power have a high detonation speed and emit a significant amount of heat during an explosion. They are very sensitive to external impulse.
The explosion comes from any detonator, including from the impact of a rifle bullet. When exposed to open fire, they burn strongly, without emitting soot and smoke, with a bright flame, an explosion is possible. This group of substances includes:
- Ten is a white powder composed of crystals. This brisant substance does not react with metals and water, is diluted in acetone and is considered the most vulnerable to external factors. It is used for detonation cords, auxiliary detonators and detonator capsules.
- Tetrile - a crystalline powder of a yellowish type, salty to the taste. It is well diluted with acetone and gasoline, poorly with alcohol, does not react with metals, and can be easily pressed. Used for the manufacture of detonators.
- RDX is one of the most brisant substances, which consists of small crystals of white, odorless and tasteless. It does not react with water and metals, it is poorly pressed. From external influences, an explosion occurs, burns with hissing, a flame of bright white color. They are used for some samples of detonator capsules, the manufacture of mixtures for industrial explosions, sea mines.
High explosive blasting with normal power
These substances have a long storage period (with the exception of dynamites), they are not significantly affected by external factors, and in practical use they are safe.
High explosives include:
- TNT is a substance in the form of crystals, which has 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. The substance with metals does not show chemical activity, is practically insensitive to shocks, friction and thermal effects. It interconnects with hydrochloric and sulfuric acid, gasoline, alcohol, as well as acetone. For example, with a shot through and molded by a rifle bullet, trotyl does not light up, and an explosion does not occur. For ammunition it is used in various alloys and in pure form. The substance is used in the form of extruded drafts of various sizes when performing demolition work.
- Picric acid is a brisant substance in the form of crystals having a yellow color and a bitter taste. It has a greater susceptibility to the effects of heat, shock and friction than TNT, can explode from a gunshot chamber. Flames during burning are very smoky. With a large accumulation of matter, detonation occurs. Compared to TNT, picric acid is a more powerful explosive.
- Dynamites - have different recipes and contain nitroglycerin, nitroesters, nitrate, wood flour and stabilizers. The main application is the national economy. The main property of dynamites is water resistance and considerable power. Their disadvantage is an increased susceptibility to thermal and mechanical influences. This requires caution when transporting and blasting. Six months later, dynamites lose their knocking ability. In addition, they freeze at a negative temperature of about 20 ° C and become dangerous during operation.
Reduced explosive power
Low power brisant substances have reduced working capacity due to the low detonation speed and low heat generation. They are inferior in properties of brisance 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 - a white or yellowish crystalline substance, which is a mineral fertilizer, is highly soluble in water. It refers to insensitive, slightly explosive substances. It does not light up 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 when explosives or combustible substances are added to it.
- Dynamons are a mixture of ammonium nitrate with combustible but non-explosive substances, such as charcoal, peat or sawdust.
- Ammonals - explosive mixtures containing nitrate, with the addition of combustible and explosive additives and aluminum powder to increase the heat of the explosion.
All types of blasting explosives based on ammonium nitrate are safe to use. They do not fly up into the air with friction, impact, or a bullet from a rifle. Lit in the 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 sulphurous iron are added to nitrate, which contributes to the prolonged stay of explosives in water without loss of properties.
Use of blasting explosives
High explosives are secondary explosives, for which detonation is the main type of explosive transformation, excited due to the 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 detonating, torpedoes and shells. Explosive substances 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 by explosions.
Blasting explosives have found their application in the following areas:
- for the development of coal seams and deposits of useful resources;
- embankments for railways and roads;
- dam construction;
- digging water channels;
- gas and oil pipelines;
- mine shaft development.
Where do they use blasting agents yet? In addition to the above, they are used:
- when compaction of the soil;
- conducting irrigation systems;
- extinguishing forest fires;
- leveling and cleaning the area.
And also research and development is underway to expand the use of this powerful explosion energy - to accelerate chemical processes using high pressures, artificial sprinkling and blasting.
Chemistry and technology of blasting explosives
Molecules of chemical compounds or mixtures thereof, containing a certain reserve of chemical energy, are called energy-saturated substances. Energy, as a result of a transformation that occurs under the influence of external factors, is converted into light, mechanical or thermal.
Pyrotechnic compositions, gunpowder and other explosives are among the most famous types of energy-saturated substances. The chemical energy in them is converted due to the rapid flow of the explosion into other types. A significant amount of heat released due to the explosion is the main criterion for its performance. Being compact and powerful sources of mechanical energy, blasting explosives are widely used in various industries.