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Kevlar material is made from it. What is Kevlar? General information, properties, application

(polyparaphenylene terephthalamide) fiber available from DuPont. Kevlar has high strength (tensile strength σ 0 = 3620 MPa). For the first time, Kevlar was obtained by the Stephanie Kwolek group in 1964, the production technology was developed in 1965, and commercial production began in the early 1970s.

Application

Initially, the material was developed for the reinforcement of automobile tires, for which it is still used. In addition, Kevlar is used as a reinforcing fiber in composite materials that are strong and lightweight.

Kevlar is used to reinforce copper and fiber optic cables (a thread along the entire length of the cable to prevent cable stretching and breakage), in speaker cones and in the prosthetic and orthopedic industry to increase the wear resistance of parts of carbon fiber feet.

Kevlar fiber is also used as a reinforcing component in blended fabrics, imparting abrasion and cutting resistance to products made from them, in particular, protective gloves and protective inserts in sportswear (for motorsport, snowboarding, etc.) .). It is also used in the shoe industry for the manufacture of puncture-resistant insoles.

Personal body armor

The mechanical properties of the material make it suitable for the manufacture of personal body armor (NIB) - body armor and armored helmets. Studies of the second half of the 1970s showed that Kevlar-29 fiber and its subsequent modifications, when used in the form of multilayer tissue and plastic (tissue-polymer) barriers, show the best combination of the rate of energy absorption and the duration of interaction with the striker, thereby providing relatively high given the weight of the obstacle, indicators of bulletproof and splinterproof resistance. This is one of the most famous uses of Kevlar.

In the 1970s, one of the most significant advances in body armor was the use of Kevlar fiber reinforcement. The development of Kevlar body armor by the US National Institute of Justice (eng. National Institute of Justice) took place over several years in four stages. In the first stage, the fiber was tested to determine if it was capable of stopping a bullet. The second step was to determine the number of layers of material needed to prevent bullets of different calibers and flying at different speeds from penetrating, and to develop a prototype vest that could protect employees from the most common threats: bullets in caliber .38 Special and .22 Long Rifle. By 1973, a seven-layer Kevlar fiber vest was developed for field testing. It was found that when wet, the protective properties of Kevlar deteriorated. Bullet protection also diminished after exposure to ultraviolet light, including sunlight. Dry cleaning and bleaching also negatively affected the protective properties of the fabric, as did repeated washing. To circumvent these problems, a waterproof vest has been developed that has a fabric cover to prevent exposure to sunlight and other negative factors.

Shipbuilding

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Literature and sources

O. Lisov. "Kevlar - a promising military material" // "Foreign Military Review", No. 2, 1986. pp. 89-90.

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Excerpt from Kevlar

“Take, take the child,” said Pierre, handing the girl and addressing the woman imperiously and hastily. - Give it back to them, give it back! - he shouted almost at the woman, putting the screaming girl on the ground, and again looked back at the French and the Armenian family. The old man was already sitting barefoot. The little Frenchman took off his last boot and patted his boots against one another. The old man, sobbing, said something, but Pierre only caught a glimpse of it; all his attention was drawn to the Frenchman in the bonnet, who at that time, swaying slowly, moved towards the young woman and, taking his hands out of his pockets, took hold of her neck.
The beautiful Armenian woman continued to sit in the same motionless position, with her long eyelashes lowered, and as if she did not see or feel what the soldier was doing to her.
While Pierre ran the few steps that separated him from the French, the long marauder in the bonnet was already tearing the necklace she was wearing from the Armenian woman's neck, and the young woman, clutching her neck with her hands, screamed in a piercing voice.
- Laissez cette femme! [Leave this woman!] - Pierre croaked in a furious voice, grabbing the long, hunched soldier by the shoulders and throwing him away. The soldier fell, got up and ran away. But his comrade, throwing his boots, took out a cleaver and menacingly advanced on Pierre.
- Voyons, pas de betises! [Oh well! Don't be silly!] He shouted.
Pierre was in that rapture of rage in which he remembered nothing and in which his strength increased tenfold. He threw himself at the barefoot Frenchman, and before he could take out his cleaver, he had already knocked him down and thrashed him with his fists. An approving cry from the surrounding crowd was heard, at the same time a horse-drawn patrol of French lancers appeared from around the corner. Lancers trotted up to Pierre and the Frenchman and surrounded them. Pierre remembered nothing of what happened next. He remembered that he was beating someone, he was beaten and that in the end he felt that his hands were tied, that a crowd of French soldiers were standing around him and searching his dress.
- Il a un poignard, lieutenant, [The lieutenant, he has a dagger,] - were the first words that Pierre understood.
- Ah, une arme! [Ah, weapons!] - said the officer and turned to the barefoot soldier who had been taken with Pierre.
- C "est bon, vous direz tout cela au conseil de guerre, [Okay, okay, you will tell everything at the trial,] - said the officer. And then he turned to Pierre: - Parlez vous francais vous? [Do you speak French? ]
Pierre looked around him with bloodshot eyes and did not answer. Probably, his face seemed very scary, because the officer said something in a whisper, and four more lancers separated from the team and stood on both sides of Pierre.
- Parlez vous francais? The officer repeated the question to him, keeping away from him. - Faites venir l "interprete. [Call for an interpreter.] - A little man in a civilian Russian dress drove out from behind the rows. By his dress and speech, Pierre immediately recognized him as a Frenchman in one of the Moscow shops.
- Il n "a pas l" air d "un homme du peuple, [He does not look like a commoner,] - said the translator, looking around Pierre.
- Oh, oh! ca m "a bien l" air d "un des incendiaires, - the officer oiled. - Demandez lui ce qu" il est? [Oh oh! he looks a lot like an arsonist. Ask him who he is?] He added.
- Who are you? The translator asked. “The bosses should be responsible for it,” he said.
- Je ne vous dirai pas qui je suis. Je suis votre prisonnier. Emmenez moi, [I won't tell you who I am. I am your prisoner. Take me away,] - Pierre suddenly said in French.
- Ah, Ah! - said the officer, frowning. - Marchons!
A crowd gathered around the lancers. Closest to Pierre was a pockmarked woman with a girl; when the detour started, she moved forward.
- Where does this lead you, my dear boy? - she said. - Girl then, girl then where will I put, if she is not theirs! - said the woman.
- Qu "est ce qu" elle veut cette femme? [What does she want?] Asked the officer.
Pierre was drunk. His enthusiasm was further intensified at the sight of the girl he had saved.
"Ce qu" elle dit? "He said." Elle m "apporte ma fille que je viens de sauver des flammes," he said. - Adieu! [What does she want? She carries my daughter, whom I have saved from the fire. Farewell!] - and he, not knowing how this aimless lie had escaped from him, walked with a decisive, solemn step between the French.
The departure of the French was one of those who were sent by order of Duronel through various streets of Moscow to suppress looting and, in particular, to catch arsonists, who, according to the general opinion, which appeared on that day among the French high-ranking officials, were the cause of the fires. Having traveled several streets, the patrol picked up five more suspicious Russians, one shopkeeper, two seminarians, a peasant and a courtyard, and several looters. But of all the suspicious people, Pierre seemed the most suspicious of all. When they were all brought to a lodging for the night in a large house on Zubovsky Val, in which a guardhouse was established, Pierre was placed separately under strict guard.

In St. Petersburg at that time in the highest circles, with greater fervor than ever before, there was a complex struggle between the parties of Rumyantsev, the French, Maria Feodorovna, the Tsarevich and others, drowned out, as always, by the trumpeting of court drones. But calm, luxurious, preoccupied only with ghosts, reflections of life, Petersburg life went on as before; and because of the course of this life, great efforts had to be made to realize the danger and the difficult situation in which the Russian people found themselves. There were the same exits, balls, the same French theater, the same interests of the courtyards, the same interests of service and intrigue. Only in the highest circles have efforts been made to resemble the difficulty of the present situation. It was told in a whisper about how both Empresses acted opposite to each other, in such difficult circumstances. Empress Maria Feodorovna, concerned about the welfare of the charitable and educational institutions under her jurisdiction, made an order to send all the institutions to Kazan, and the things of these institutions had already been packed. The Empress Elizaveta Alekseevna, when asked what orders she would like to make, with her characteristic Russian patriotism, deigned to answer that she could not make orders about state institutions, since this concerns the sovereign; about the same thing that personally depends on her, she deigned to say that she would be the last to leave Petersburg.

Shipbuilding

Aviation industry

Temperature properties

Tags: Kevlar, kevlar manufacturer, kevlar manufacturing, kevlar, kevlar manufacturer, military type kevlar, ballistic kevlar, kevlar bullet resistance, kevlar protective properties, aramid fabric, aramid fabrics, hybrid fabrics, aramids Kevlar goes to conveyor belts aramid clothing fabrics
Kevlar on body armor

Today Kevlar is used in the manufacture of products that require high performance wear resistance materials: climbing ropes, braces, helmets, shoe tops, backpacks, skis, gloves, as well as for the manufacture of workwear. Kevlar fiber has a low weight and high resistance to various kinds of influences. Possesses properties such as incombustibility and heat resistance. According to the developers, Kevlar fibers with equal weight are five times stronger than steel.

In the photo, the bullet could not penetrate the aramid fabrics (Kevlar).

Widespread use of Kevlar finds:

Children's sportswear, hockey uniforms.
Liners for clothing in places of increased wear.
Liners in places of probable trams (knees, elbows),
probable places of injury with a knife (feed, stomach).
Good protection against injury (traumatic weapons)
in case of conflicts on the roads.

Best cut protection.
Gloves, motorcycle, biker clothing.
It goes well even with powerful musical speakers and a fire uniform since it does not burn.

Initially, the material was developed for the reinforcement of automobile tires, in this capacity it is still used. In addition, Kevlar is used as a reinforcing fiber in composite materials that are strong and lightweight.

Kevlar fiber is also used as a reinforcing component in blended fabrics, imparting abrasion and cutting resistance to products made of them; in particular, protective gloves and protective inserts in sportswear (for motorsport, snowboarding, etc.) are made from such fabrics. .).

In workwear, Kevlar fiber is used mainly for reinforcing knee pads (knee pads) and elbows. Because Kevlar fabric has high indicators of abrasion, then it is used in clothing in those places where the load on abrasion, cuts and punctures is the highest.

Kevlar structure. A high degree of polymer ordering and strength are provided by intermolecular hydrogen bonds.

The mechanical properties of the material make it suitable for making bulletproof vests. This is one of the most famous uses of Kevlar.

In the 1970s, one of the most significant advances in body armor was the use of Kevlar fiber reinforcement. The development of the Kevlar body armor by the National Institute of Justice took place over several years in four stages. In the first stage, the fiber was tested to determine if it was capable of stopping a bullet. The second stage was to determine the number of layers of material required to prevent bullets of various calibers and flying at different speeds from penetrating, and to develop a prototype vest capable of protecting employees from the most common threats: 38 Special and 22 Long Rifle bullets. By 1973, a seven-layer Kevlar fiber vest was developed for field testing.

Shipbuilding

In the last decade, Kevlar has become widespread in shipbuilding. Due to the technological complexity and price of Kevlar, it is used selectively. For example, only in the keel or at the seams. Many manufacturers (such as BAIA Yachts, Blue water, Danish yacht, Zeelander Yachts), making a small number of yachts per year, are systematically switching to using Kevlar. The leader in the production of kevlar yachts is the Italian shipyard Cranchi, which produces kevlar yachts ranging in size from 11 to 21 meters.

Aviation industry

Kevlar is used in a number of unmanned aerial vehicles (such as the RQ-11) to enhance protection.

Temperature properties

Kevlar retains its strength and elasticity at low temperatures, up to cryogenic (-196 ° C), moreover, at low temperatures it even becomes slightly stronger.

When heated, Kevlar does not melt, but decomposes at relatively high temperatures (430-480 ° C). The decomposition temperature depends on the heating rate and the duration of exposure to temperature

Currently, Kevlar has become a common component of clothing and equipment for people whose lives are constantly in danger: military and security officials, astronauts and researchers, athletes and firefighters. Kevlar fibers are used wherever increased strength is required, from car tires to yacht hulls, their field of application is constantly expanding, and the production technology is being improved. This material was obtained half a century ago, and it will seem strange to many that a woman became its author.

How did Kevlar come about?

It is symbolic that the inventor of this unique fiber, Stephanie Kwolek, loved to sew clothes for dolls as a child. After school, she graduated as a chemist at Carnegie University, but dreamed of medicine. To earn money to study at the university, in 1946 the girl began to work for the famous DuPont concern, and soon realized that her vocation was still chemistry. In 1964, the Kwolek group worked to improve the production of polyaramides - polymer substances with a rod-like structure that could replace steel cord in tires. By abandoning the melt method, Stephanie was able to create an unusual-looking solution that, when passed through the spinnerets, turned into aramid filaments.

When the resulting fiber was tested for strength, the researchers decided that the equipment had broken - the strength of the new material was five times that of steel.

The new material, called Kevlar, came into commercial use in the 1970s. It began to be used for the production of tires, cord strips, composite materials. At the same time, the military and security forces drew attention to the high strength of polyaramide fibers, the purpose of which was to develop personal protective equipment. The idea of a body armor appeared during the First World War (its author was the writer Conan Doyle), but traditional metal plates were heavy and hampered movement.

For several years, specialists from the American National Institute of Justice have carried out thorough research, during which they proved that seven layers of Kevlar fabric provide resistance to a bullet shot for the most common 38 caliber. The last stage of field tests showed that the strength of such a bulletproof vest decreases when it gets wet and when exposed to UV rays. It has also been found that products made from Kevlar fabric deteriorate their protective properties after several washes, and that they do not tolerate bleaching and dry cleaning.

The result of the development was a Kevlar body armor coated with a waterproof fabric that protects the reinforced layer from water and sun. In addition, Kevlar helmets, gloves, shoe insoles, etc. began to be used as personal protective equipment.

Properties of aramid fibers

In addition to its high strength, Kevlar has many other unique properties, namely:

upon contact with fire and high temperatures, this fiber does not burn, does not smoke or melt;
Kevlar is non-toxic and non-explosive;
its thermal decomposition temperature is 430-450 degrees;
the strength of the armide fibers begins to gradually decrease when heated to more than 150 degrees;
when freezing, Kevlar only becomes stronger, it is able to withstand cryogenic temperatures (up to -200 degrees);
this material is an electrical insulator.

In addition, the Kevlar fabric is soft, hygroscopic and breathable, and is quite comfortable to use. True, this does not apply to clothing designed to work in open fire and high temperatures. To increase the heat resistance, Kevlar is coated with aluminum. The material made of such fiber reliably protects against powerful thermal radiation, contact with surfaces heated to 500 degrees, as well as from splashes of hot metal.

It should also be added that this material is quite light - one meter of fabric weighs 30-60 g, and although it is not cheap (from $ 30 per square meter), its excellent protective properties fully justify such costs. Protective materials reinforced with Kevlar threads are somewhat cheaper, which makes them resistant to tearing and abrasion. Such fabrics are used for protective inserts in work and sportswear, gloves, as well as wear-resistant insoles. Caring for products made from them is extremely simple. They should not be:

wash frequently;
clean with chemicals;
expose to sunlight.

Where is Kevlar applied?

This high-strength fiber is used in a wide variety of applications, from the aeronautical and aerospace industries to sports and outdoor wear. Kevlar enters the market in the form of threads, cord, fabric, as well as a component of composite and mixed materials. The main ways to use it are.

Increasingly, modern high-tech materials are being used in a wide variety of industries. One of them is Kevlar fabric. This element is distinguished from other products by its excellent resistance to both friction and point impact. So in composite materials, it is most often combined with various, in turn, in the textile industry, Kevlar fabric has found the broadest application. Such high-tech material as Kevlar is used for sewing jackets, jeans, gloves, for the production of cables and much more.

Characteristics of Kevlar fabric

Kevlavr fabric is actively used as a reinforcing agent for a variety of composite materials. Kevlar fabric has high strength with very low weight. Such a tool not only does not lose its properties under the influence of low temperatures (the temperature limit is -190 degrees), but also gains additional strength.

Exposure to high temperatures will also not bring much harm to Kevlar fabric, because the temperature of its destruction ranges from +430 to +480 degrees. Moreover, the temperature of destruction depends entirely on the time and intensity of heating. In order to reduce the cost of finished products, the production of combined fabrics has been established, where fiberglass or coal fibers are added. For human health, Kevlar fabric does not pose any threat at all.

The high heat resistance and strength of Kevlar fabric allows it to be used for the manufacture of uniforms for firefighters. Due to the fact that Kevlar is 5 times stronger than steel (with the same weight), it became possible to use it for the manufacture of body armor. It was the special devices for protection, their rather successful production, that contributed to the popularity of Kevlar fabric in many respects. Now this material is used in a wide variety of industries, including aerospace.

Operation of Kevlar fabric

In household terms, Kevlar is also widely used. Most often it is used exactly where high resistance to low and high temperatures is required, and, accordingly, its highest strength. Usually, various equipment for athletes (helmets, cables, gloves, etc.) is produced from Kevlar fabric. In addition, as mentioned earlier, Kevlar fabric is actively used in the production of composite materials.

However, in terms of temperature and strength indicators, Kevlar is slightly inferior to carbon fiber, but at the same time, it tolerates bending loads much better. In an attempt to combine the qualities of these two materials, Kevlar composite fabrics have been created, with approximately equal amounts of both materials. Such fabrics perfectly tolerate elastic deformation. But carbon-Kevlar fabric loses in strength, has a slightly higher weight and does not tolerate contact with water very well.

However, the combination of epoxy resins with Kevlar fabric is not ideal. Such resins tend to "pick up" moisture, and accumulate it in themselves. Upon contact with water, Kevlar significantly loses its properties, which are so high in its dry state. In addition, ultraviolet light is a catalyst that shortens the life of the Kevlar component.

That is why it is advisable to operate Kevlar only under certain conditions (using one hundred percent of all the positive characteristics of the material), which actually does not reduce its demand at the present time. Kevlar fabric is used for sewing special construction work clothing (assembly gloves, welding overalls, etc.).