Kevlar was introduced by DuPont in the 1970s. It was the first organic fibre with sufficient tensile strength and modulus to be used in advanced composites.
Kevlar is an aramid, a term invented as an abbreviation for aromatic polyamide. The chemical composition of Kevlar is poly para-phenyleneterephthalamide, and it is more properly known as a para-aramid. Aramids belong to the family of nylons. Common nylons, such as nylon 6,6, do not have very good structural properties, so the para-aramid distinction is important. The aramid ring gives Kevlar thermal stability, while the para structure gives it high strength and modulus.
Kevlar was the fore-runner to PBO and shares many of the same properties but cannot compete with PBO in terms of strength and stretch.
