The History of Bulletproof Vests

Early bulletproof vests were mainly made from polyperifenylene terithalamide, better known as Kevlar. In 1989, a company called Allied Signal developed a competitor for Kevlar and called it SpectraShield. The material of the vests themselves is also prone to break down for various reasons. Manufacturers say that there's about a five-year lifespan on vests and caution against buying used vests unless you know the manufactured date and the materials used to make it.