The expression “bulletproof» arose in the 16th century and was used to designate armor resistant to the penetration of projectiles, so that the only effect produced after the impact was its dent.
To attend the birth of the first bulletproof vest we had to wait until well into the 19th century. The event took place in Korea, where vests began to be made to prevent injuries from French firearms.
Over there Kim Gi-Doo y Gnag Yoon they discovered that cotton, if it was dense enough, could protect the human body from injuries caused by projectiles. This is how the first vests were designed, made up of almost thirty layers of cotton.
One of those vests was captured by the United States Navy in its attack on the island of Ganghwa (1871) and taken to Washington for analysis. Until 2007 it was kept in the Smithsonian Museum, at which time it was returned to Korea.
From silk to steel
In 1880 the American physician George E Goodfellow He carried out research with silk vests similar to medieval gambesones (quilted doublets), which were made of twenty layers of fabric. Through experimentation he was able to show that the silk fabric lessened the impact of the bullets.
When the 19th century was about to say goodbye to a Polish merchant –Casimir Zeglen– developed bulletproof vests with silk fabric, inspired by Goodfellow’s, capable of stopping bullets fired from pistols that used black powder cartridges.
These vests were sent to oblivion after the assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, as he died while wearing one of these vests.
During the First World War, vests made of carbon steel became especially famous. chromium-nickel, composed of a breastplate and a helmet. The main problem with these “bulletproof” equipment is that they weighed about 18 kilos, which made movement extremely difficult.
In World War II, both enormously heavy armor and jackets made of nylon fabric that had steel plates inside, capable of stopping the splinters of anti-aircraft projectiles, were used.
Better with Kevlar
In 1965 the definitive solution arrived. This year Stephanie Kwoleka researcher from the French company Dupont, obtained a revolutionary material through the precipitation and coagulation of crystalline solutions, which she named Kevlar.
It was a synthetic polyamide polymer with a series of singularities that made it especially attractive: Kevlar 29 and Kevlar 40 have a resistance up to eight times greater than steel wire, it is capable of withstanding high temperatures and does not degrade until descending to -196ºC.
The mechanism by which this polymer prevents bullet damage to the body is based on capturing the energy of the bullet and stopping it, layer after layer, to prevent it from completely perforating the vest. To disperse the kinetic energy, the fibers must be intertwined and coated with a resin. In other words, you could say that Kevlar body armor is not bulletproof, it’s bulletproof.
Its effectiveness depends to a large extent on the speed of the bullet, if it is low it is easier to stop it, but if they are shot at high speed or have a pointed shape it is much more difficult to prevent them from piercing the vest.
From its discovery other materials arose –twaon y zylon– which have been relegated to the background because they have higher costs and a much more complex manufacturing than Kevlar.