Currently, Kevlar has become the usual component of the clothing and equipment of people whose life is constantly at risk: military and silovikov, astronauts and researchers, athletes and firefighters. Kevlar fibers are used everywhere, where high strength is required, ranging from automotive tires and ending with the yacht cases, their scope is constantly expanding, and the production technology is enhanced. . This material was obtained half a century ago, and many will seem strange that the woman became his author.
How did Kevlar appear?
It is symbolic that the inventive of this unique fiber Stephanie Kolk in childhood loved to sew clothes for dolls. After school, she received a specialty chemist at Carnegie University, but dreamed of medicine. To earn money for learning at the university, in 1946 the girl began to work in the famous Dupont concern, and soon realized that her vocation was still chemistry. In 1964, the Kollyk group worked on the improvement of the production of polyariamides - polymeric substances with a rod-shaped structure that could replace steel cord in tires. Refusing to the melt method, Stephanie was able to obtain an unusual type of solution, which when passing through the filters turned into aramid threads.
When the resulting fiber began to test for strength, the researchers decided that the equipment broke down - the strength of the new material was five times more than that of steel.
The new material called Kevlar, received commercial use in the seventies. It began to use for the production of tires, cord ribbons, composite materials. At the same time, military and power structures were paid to the high strength of polyaramid fibers, the purpose of which was the development of individual means of protection. The idea of the body armor appeared during the First World War (its author was the writer Conan Doyle), but the traditional metal plates were severe and skipped movements.
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Specialists of the American National Institute of Justice for several years spent thorough research, during which they proved that the resistance to the pulver shot for the most common 38 caliber provides kevlar tissue in seven layers. The last stage of field tests showed that the strength of such a body armor decreases with its wetting and when exposed to UV rays. It was also found that Kevlar tissue products worsen their protective properties after several styrics, and that they do not tolerate whitening and dry cleaning.
The result of the developed developments was the kevlar armor with a coating of waterproof tissue, providing protection for the reinforced layer from the water and the Sun . In addition, kevlar helmets, gloves, shoe insoles, etc. began to use as a means of individual protection.
Properties of aramid fibers
In addition to high strength, Kevlar has many other unique properties, namely:
- When contacting with fire and high temperatures, this fiber does not burn, do not smoke and does not melt;
- Kevlar is not toxic and not explosive;
- The temperature of its thermoaming is 430-450 degrees;
- The strength of the arid fiber begins to gradually decrease when heated more than 150 degrees;
- When freezing, Kevlar becomes only stronger, it is able to withstand cryogenic temperatures (up to -200 degrees);
- This material is an electrical insulator.
In addition, the Kevlar fabric is characterized by soft, hygroscopicity and the ability to air exchange, and is quite comfortable when used. True, this does not apply to clothing designed to work in operating conditions and high temperatures. To increase the heat resistance, Kevlar is covered with aluminum. Material from such a fiber reliably protects against powerful heat radiation, contact with hots hot to 500 degrees, as well as on splashes of hot metal.
It should also be added that this material is quite easy - one meter of fabric weighs 30-60 g, and although it is not affordable (from $ 30 per square meter), its excellent protective properties fully justify such expenses. Some cheaper are protective materials reinforced by kevlar threads, which gives them resistance to rupture and abrasive abrasion. Such fabrics are used for protective inserts in working and sportswear, gloves, as well as wear-resistant stelks. Caring for products from them is extremely simple. They should not:
- often wash;
- clean chemical reagents;
- exposure to sunlight.
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Where is Kevlar applied?
This high-strength fiber finds the most diverse use - from the aviation and space industry to sports and tourist clothes. Kevlar comes to the market in the form of threads, cord, fabric, as well as component of composite and blended materials . The main methods of its use are:
- Production of reinforced tires;
- Making copper and fiber optic cables;
- hydrotechnical and gas-industrial systems of high pressure;
- Aviation and Space Technology;
- shipbuilding;
- prosthetics and orthopedic products;
- means of individual protection for the army, power structures, persons working in extreme conditions;
- Sportswear and equipment.
Without a doubt, in the near future we can expect both the improvement of this wonderful material and the new possibilities of its use.