Bullet-proof vests is a man-of protective equipment, and it is used protective shells or shrapnel injuries on the human body.

Used in ancient wars mainly knives, spears, arrows and other cold-steel weapons, the soldiers clad in armor to be effective in the protection of the body, reducing cold-steel weapons harm. Since the emergence of guns, artillery and other firearms, this situation has changed. For the fire, and the need to re-play 30-40 kilograms of armor, which will allow soldiers very difficult to accomplish a variety of combat missions. Thus, access to firearms dynasty, the armor will be gradually eliminated. However, it did not give up the pursuit of the body protective equipment. World War I, it was found that most of the casualties of soldiers from artillery shells, grenades. Bombs and mines caused by the shrapnel. During this period the birth of the helmets in the battle proved to be effective in protection of the soldiers head and shrapnel injuries. In the first and the Second World War, there have been a number of countries to develop and use steel or alloy steel system to do the carapace and a bullet-proof vest. However, due to too heavy after wearing mobility, infantry actual unavailable. Until this century, 40 years ago, people considered a bullet-proof vest material has not been out of the circle of metal materials.

The prototype of the modern bullet-proof vests in the 50's during the Korean War. U.S. military first used to test the soft nylon synthetic fiber materials such system to do a bullet-proof vest. They found that 12-storey special nylon fiber cloth can be received by a certain bullet-proof effect. When the bullet hit a bullet-proof vest, the vertical and horizontal multi-layer woven nylon fiber muffle the same network as the projectile, projectile continues to campaign, then we must stretch nylon fiber, nylon fiber tension to reduce the velocity of the projectile, consumption and absorption of the projectile kinetic energy. Kinetic energy as a result of shrapnel and projectile velocity is much lower than general, so bullet-proof vests nylon protective role of shrapnel more obvious.

60 U.S. Army Vietnam era M69 nylon will be bullet-proof vests as standard equipment. However, due to nylon fibers in the limited tensile strength, nylon bullet-proof vests to receive a good protective effect, the weight to be 4.5 kilograms or more. According to the expert testing and analysis, interspersed on such a heavy bullet-proof vests, the soldiers of the combat capability will be reduced more than 30%. In hot and humid Vietnam battlefield, U.S. soldiers are bulletproof nylon unbearable burden and sultry feeling, and not wearing a bullet-proof vest in modern warfare is very dangerous. A large number of statistical analysis showed that the shrapnel of modern war is the main threat to soldiers, it accounts for the reasons leading to injuries and deaths of the 3 / 4 of the remaining 1 / 4 is the shock wave, bullets, such as caused by burning. Therefore, after the Vietnam War, people are always looking for suitable material bullet-proof vests. Until the 70's, there finally appeared the better bullet-proof vest material - "Kevlar."

"Kevlar" is the DuPont Corporation in the United States in the mid-60 developed a synthetic fiber, and in 1972, realize the industrial production. Its wholly-called "poly p-phenylene terephthalamide fiber p-phenylenediamine", "Kevlar" is one of its trade names. "Kevlar" very high tensile strength, nylon fiber is 2 times more than it appears to make bullet-proof vests protective performance markedly improved. Tests indicate that the "Kevlar" kinetic energy absorption capacity of shrapnel is nylon 1.6 times to 2 times that of steel. Multi-storey 'Kevlar "fabric of the bullet can be received with satisfaction the protective effect. As a result of the" Kevlar "production of bullet-proof vests than nylon lightweight bullet-proof vests, bullet-proof performance, it has been in many national army and the police favor. At present, apart from the United States, Germany, France, Britain, Israel, Italy and equipment are developed "Kevlar" bullet-proof vests.