Many have heard the name “Kevlar”. Body armor and helmets are made from it. Many people endow it with almost supernatural abilities, considering it a unique material that protects against bullets. Of course, we couldn’t ignore it and tried to figure out what it was.
What Wikipedia says about Kevlar:
Kevlar is a trademark of para-aramid (polyparaphenylene terephthalamide) fiber manufactured by DuPont. Kevlar has high strength (five times stronger than steel, tensile strength σ0 = 3620 MPa). Kevlar was first produced by Stephanie Kwolek's group in 1964, the production technology was developed in 1965, and commercial production began in the early 1970s.
Currently, aramid fibers are produced throughout the world under different brand names. But, just as copiers around the world are called by the name of their creator company Xerox, aramid materials are also called Kevlar in everyday life.
What's special about aramid fiber?
Aramid fiber is characterized by high specific tensile strength; high resistance to impact and dynamic loads. In addition, the fiber and its varieties are fire-resistant.
Initially, Kevlar was used to reinforce car tires, but due to its lightness, composite materials based on it began to be used in the aviation and space industries. In addition, heavy-duty cables are made from Kevlar.
In fact, it is its low-density impact resistance that makes it an excellent material for armor protection.
Despite all its advantages, aramid fiber still has disadvantages. These include: aging, “hydrophobia” and price. When wet, aramid fiber loses its strength by almost half. When Kevlar dries, it regains its qualities, but over time, its mechanical strength disappears irrevocably. However, this process does not go too quickly - most manufacturers provide a 5-year warranty. And special treatment solves the problem of getting wet.
In addition, aramid fiber is difficult to dye, so products made from it are almost always yellow.
In addition to aramid fibers, high-density polyethylene (HDPE) is also often used in modern body armor. In fact, it is the same material from which bags and tote bags are made. Several dozen thin sheets of PVP can stop a pistol bullet.
But Kevlar, PVP and other materials can do little to oppose powerful rifle cartridges. Therefore, they are used for light protection, or as additions to body armor with metal armor plates.
High-strength fiber fits elegantly into modern life. Few people know what exactly this chemical compound is. The material, originally synthesized for car tires, quickly spread, finding its niche in other areas. However, first things first.
Who invented Kevlar?
The synthesis was first carried out in 1965 by Stephanie Kwolek, an employee of the Dupont chemical concern. She was working on para-aramids. The next task was to obtain strong polymer threads to replace steel cords in car tires.
Kwolek decided to change the technology by using a solution of para-aramid rather than the whole substance. The appearance of the resulting substance did not meet any requirements. The engineer refused to fill the machine with a cloudy moonshine-like solution instead of dark molasses. But the woman was able to convince him to go for the experiment.
The surprise of the chemists knew no bounds: the equipment pulled out the thread without any hindrance. When the results of testing the resulting yarn arrived, Stephanie decided that the device had failed, since high numbers are not characteristic of synthetic polymers. But repeated studies confirmed that the substance is stronger than steel.
What properties does the Kevlar material have?
Goal achieved! The yarn will replace the heavy metal alloy in tires. Further research brought even more pleasant surprises.
It turned out that the quality of the threads deteriorates only under constant exposure to high temperatures. At a temperature of 160 degrees, the strength will begin to decrease by 10-20% after 20 days. For the polymer to decompose, a temperature of over 430 degrees is required. Low temperatures only increase the strength and elasticity of the fiber.
In addition, the material has the following characteristics:
- light weight and low density - a meter of Kevlar fabric weighs up to 60 g;
- resistance to solvents;
- low electrical conductivity;
- corrosion resistance;
- resistance to mechanical stress.
Along with the advantages, there are small disadvantages:
- absorption of moisture and susceptibility to its influence;
- decrease in performance properties when exposed to ultraviolet radiation.
Carbon fiber is superior to Kevlar in strength and temperature resistance. Attempts to combine these two materials have led to negative consequences. Such fabrics became heavier, became more susceptible to water, and lost strength.
Where is Kevlar used?
Fiber is used for various purposes and areas:
- production of tires and car bodies;
- strengthening cables (copper and fiber optic);
- shipbuilding;
- space and aviation industry;
- production of orthopedic products;
- Sports Equipment;
- cloth;
- musical instruments;
- protective equipment for law enforcement units, military personnel, workers (when performing official duties in extreme conditions).
What kind of clothing is made from Kevlar?
Various workwear and sports uniforms are reinforced with separate threads.
Tactical gloves made of Kevlar are a descendant of brass knuckles. They will provide a crushing blow and protect the hand from damage. The products are popular among soldiers and civilians. They are effective when working in high temperature conditions, with metals and sharp objects.
Knee pads and elbow pads are being reinforced. Airsoft players use T-shirts with inserts, motorcyclists wear fiber helmets. A Kevlar jacket will be an indispensable assistant for lumberjacks. Any garment can be given extra strength, but these options are the most common.
The development of means of protection against firearms was carried out in four stages. First, they determined the fiber's ability to accomplish this mission. Then, the number of layers needed to protect against bullets of various calibers fired from various distances was calculated. The first model appeared in 1973. All the shortcomings of the fiber surfaced. The final stage was the development of a body armor made of Kevlar, resistant to moisture and ultraviolet radiation.
Shipbuilding
Aviation industry
Temperature properties
Tags: Kevlar, Kevlar manufacturer, Kevlar production, Kevlar, Kevlar manufacturer, military type Kevlar, ballistic Kevlar, bullet resistance of Kevlar, protective properties of Kevlar, Aramid fabric, aramid fabrics, hybrid fabrics, aramids Kevlar goes to conveyor belts aramid fabrics for firefighting clothing
Kevlar for body armor
Today, Kevlar is used in the production of products that require high performance wear resistance materials: climbing ropes, quickdraws, helmets, shoe uppers, backpacks, skis, gloves, as well as for the manufacture of workwear. Kevlar fiber is lightweight and highly resistant to various types of impacts. It has properties such as non-flammability and heat resistance. According to the developers, Kevlar fibers of equal weight are five times stronger than steel.
In the photograph, the bullet was unable to penetrate aramid fabrics (Kevlar).
Kevlar is widely used:
Children's sportswear, hockey uniform.
Inserts in clothing in areas of high wear.
Inserts for places of possible injury (knees, elbows),
probable places of injury with a knife (female, stomach).
Good protection against traumatism (traumatic weapons)
in case of conflicts on the roads.
The best protection against cuts.
Gloves, motorcycle, biker clothing.
It goes well even with powerful music speakers and firefighting uniforms as it does not burn.
Initially, the material was developed for reinforcing car tires, and is still used in this capacity today. In addition, Kevlar is used as a reinforcing fiber in composite materials, which are strong and lightweight.
Kevlar is used to reinforce copper and fiber optic cables (a thread along the entire length of the cable that prevents stretching and breaking of the cable), 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 mixed fabrics, giving products made from them resistance to abrasive and cutting influences; in particular, protective gloves and protective inserts in sportswear (for motorsports, snowboarding, etc.) are made from such fabrics .).
In workwear, fabric with Kevlar fiber is used mainly for reinforcing pads in the knee area (knee pads) and elbow area. Because Kevlar fabric has high abrasion resistance, so it is used in clothing in those places where the greatest stress is on abrasion, cuts and punctures.
Kevlar structure. The high degree of order of the polymer and its strength are provided by intermolecular hydrogen bonds.
The mechanical properties of the material make it suitable for the manufacture of bulletproof vests. This is one of the most famous uses of Kevlar.
In the 1970s, one of the most significant advances in the development of body armor was the use of Kevlar fiber reinforcement. The development of 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 whether it could stop a bullet. The second step was to determine the number of layers of material needed to prevent penetration by bullets of different calibers traveling at different speeds, and to develop a prototype vest that could protect 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 difficulties and price of Kevlar, it is used selectively. For example, only in the keel part or at the seams. Many manufacturers (such as the shipyards BAIA Yachts, Blue water, Danish yacht, Zeelander Yachts), making not a very large 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 the design of a number of unmanned aerial vehicles (such as the RQ-11) to improve protection.
Temperature properties
Kevlar retains strength and elasticity at low temperatures, down to cryogenic temperatures (−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
Tags: Kevlar, Kevlar manufacturer, Kevlar production, Kevlar, Kevlar manufacturer, military type Kevlar, ballistic Kevlar, bullet resistance of Kevlar, protective properties of Kevlar, Aramid fabric, aramid fabrics, hybrid fabrics, aramids Kevlar goes to conveyor belts aramid fabrics for firefighting clothing Kevlar for body armor
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, the scope of their application is constantly expanding, and the production technology is being improved. This material was received half a century ago, and many will find it strange that its author was a woman.
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 majored in chemistry at Carnegie University, but dreamed of medicine. In order to earn money for studying at the university, in 1946 the girl began working at the famous DuPont concern, and soon realized that her calling was, after all, chemistry. In 1964, Kwolek's group worked to improve the production of polyaramids, 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 spinnerets, turned into aramid threads.
When the resulting fiber began to be tested for strength, the researchers decided that the equipment had broken down - the strength indicators of the new material were five times greater than those of steel.
The new material, called Kevlar, came into commercial use in the seventies. It began to be used for the production of tires, cord tapes, and composite materials. At the same time, military and law enforcement agencies drew attention to the high strength of polyaramid fibers, whose goal was to develop personal protective equipment. The idea of a bulletproof vest appeared during the First World War (its author was the writer Conan Doyle), but traditional metal plates were heavy and hampered movement.
Specialists from the American National Institute of Justice conducted thorough research for several years, during which they proved that resistance to bullet shots for the most common 38 caliber is provided by seven layers of Kevlar fabric. The last stage of field testing showed that the strength of such body armor decreases when it gets wet and when exposed to UV rays. It was also found that Kevlar fabric products deteriorate in their protective properties after several washes, and that they do not tolerate bleaching or dry cleaning.
The result of the developments was a Kevlar body armor coated with water-resistant fabric, which provides protection for 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 high strength, Kevlar has many other unique properties, namely:
- when in 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 armid fibers begins to gradually decrease when heated to more than 150 degrees;
- when frozen, Kevlar only becomes stronger, it is able to withstand cryogenic temperatures (up to -200 degrees);
- this material is an electrical insulator.
In addition, Kevlar fabric is soft, hygroscopic and air-exchangeable, and is quite comfortable to use. True, this does not apply to clothing designed to work in conditions of open fire and high temperatures. To increase heat resistance, Kevlar is coated with aluminum. Material made from such fiber reliably protects from 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 sports clothing, gloves, and also as wear-resistant insoles. Caring for products made from them is extremely simple. They should not:
- wash often;
- clean with chemical reagents;
- expose to sunlight.
Where is Kevlar used?
This high-strength fiber finds a wide variety of applications - from the aviation and space industries to sports and travel clothing. Kevlar comes to the market in the form of threads, cord, fabric, and also as a component of composite and mixed materials. The main ways of its application are:
(polyparaphenylene terephthalamide) fiber manufactured by DuPont. Kevlar has high strength (tensile strength σ 0 = 3620 MPa). Kevlar was first produced by Stephanie Kwolek's 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 reinforcing car tires, for which it is still used today. In addition, Kevlar is used as a reinforcing fiber in composite materials, which are strong and lightweight.
Kevlar is used to reinforce copper and fiber optic cables (a thread along the entire length of the cable that prevents stretching and breaking of the cable), 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 mixed fabrics, giving products made from them resistance to abrasive and cutting influences; in particular, protective gloves and protective inserts in sportswear (for motorsports, snowboarding, etc.) are made from such fabrics .). It is also used in the shoe industry to make anti-puncture insoles.
Personal armor protection
The mechanical properties of the material make it suitable for the manufacture of personal armor protection (PIB) - body armor and body armor. Research in the second half of the 1970s showed that Kevlar-29 fiber and its subsequent modifications, when used in the form of multilayer fabric and plastic (fabric-polymer) barriers, show the best combination of energy absorption rate and duration of interaction with the striker, thereby providing relatively high, given the mass of the obstacle, indicators of bulletproof and anti-fragmentation resistance. This is one of the most famous uses of Kevlar.
In the 1970s, one of the most significant advances in the development of body armor was the use of Kevlar fiber reinforcement. Development of a Kevlar body armor by the US National Institute of Justice. National Institute of Justice) occurred over several years in four stages. In the first stage, the fiber was tested to determine whether it could stop a bullet. The second phase was to determine the number of layers of material needed to prevent penetration by bullets of different calibers and traveling at different speeds, and to develop a prototype vest capable of protecting employees from the most common threats: .38 Special and .22 Long Rifle caliber bullets. 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. The ability to protect against bullets also decreased after exposure to ultraviolet light, including sunlight. Dry cleaning and bleaches also negatively affected the protective properties of the fabric, as did repeated washing. To overcome these problems, a waterproof vest has been developed that has a fabric coating to prevent exposure to sunlight and other harmful factors.
Shipbuilding
see also
Write a review about the article "Kevlar"
Notes
Literature and sources
- O. Lisov. “Kevlar is a promising material for military purposes” // Foreign Military Review, No. 2, 1986. pp. 89-90.
|
||||||||||||||||||||||||||||||
Excerpt describing Kevlar
“Take, take the child,” said Pierre, handing over the girl and addressing the woman imperiously and hastily. - Give it to them, give it to them! - 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 clapped the boots one against the other. The old man, sobbing, said something, but Pierre only caught a glimpse of it; all his attention was turned to the Frenchman in the hood, who at that time, slowly swaying, moved towards the young woman and, taking his hands out of his pockets, grabbed 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, a long marauder in a hood 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 shrill voice.
– Laissez cette femme! [Leave this woman!] - Pierre croaked in a frantic 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 away his boots, took out a cleaver and menacingly advanced on Pierre.
- Voyons, pas de betises! [Oh well! Don’t be stupid!] – he shouted.
Pierre was in that rapture of rage in which he remembered nothing and in which his strength increased tenfold. He rushed at the barefoot Frenchman and, before he could take out his cleaver, he had already knocked him down and was hammering at him with his fists. An approving cry from the surrounding crowd was heard, and at the same time a mounted patrol of French lancers appeared around the corner. The lancers trotted up to Pierre and the Frenchman and surrounded them. Pierre did not remember anything of what happened next. He remembered that he had beaten someone, he had been beaten, and that in the end he felt that his hands were tied, that a crowd of French soldiers was standing around him and searching his dress.
“Il a un poignard, lieutenant, [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 was taken with Pierre.
“C"est bon, vous direz tout cela au conseil de guerre, [Okay, okay, you’ll tell everything at the trial," said the officer. And after that he turned to Pierre: “Parlez vous francais vous?” [Do you speak French? ]
Pierre looked around him with bloodshot eyes and did not answer. His face probably 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, staying away from him. - Faites venir l "interprete. [Call an interpreter.] - A small man in a Russian civilian dress came out from behind the rows. Pierre, by his attire and speech, immediately recognized him as a Frenchman from one of the Moscow shops.
“Il n"a pas l"air d"un homme du peuple, [He doesn’t look like a commoner," said the translator, looking at Pierre.
– Oh, oh! ca m"a bien l"air d"un des incendiaires," the officer blurred. "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? – asked the translator. “The authorities must answer,” 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! – the officer said, frowning. - Marchons!
A crowd gathered around the lancers. Closest to Pierre stood a pockmarked woman with a girl; When the detour started moving, she moved forward.
-Where are they taking you, my darling? - she said. - This girl, what am I going to do with this girl, if she’s not theirs! - the woman said.
– Qu"est ce qu"elle veut cette femme? [What does she want?] - asked the officer.
Pierre looked like he was drunk. His ecstatic state intensified even more 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 is carrying my daughter, whom I saved from the fire. Farewell!] - and he, not knowing how this aimless lie escaped him, walked with a decisive, solemn step among the French.
The French patrol was one of those that were sent by order of Duronel to various streets of Moscow to suppress looting and especially to capture the arsonists, who, according to the general opinion that emerged that day among the French of the highest ranks, were the cause of the fires. Having traveled around several streets, the patrol picked up five more suspicious Russians, one shopkeeper, two seminarians, a peasant and a servant, and several looters. But of all the suspicious people, Pierre seemed the most suspicious of all. When they were all brought to spend 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 this time, in the highest circles, with greater fervor than ever, 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 the court drones. But calm, luxurious, concerned only with ghosts, reflections of life, St. Petersburg life went on as before; and because of the course of this life, it was necessary to make great efforts to recognize 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 courts, the same interests of service and intrigue. Only in the highest circles were efforts made to recall the difficulty of the present situation. It was told in whispers how the two 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 institutions to Kazan, and the things of these institutions were already packed. Empress Elizaveta Alekseevna, when asked what orders she wanted to make, with her characteristic Russian patriotism, deigned to answer that she could not make orders about state institutions, since this concerned the sovereign; about the same thing that personally depends on her, she deigned to say that she will be the last to leave St. Petersburg.