Kevlar is a synthetic fiber that has a high strength-to-weight ratio. It is made from poly-paraphenylene terephthalamide (PPTA) and is a member of the aramid family of synthetic polymers. The density of Kevlar is 1.44 grams per cubic centimeter. This is higher than the density of water, which is 1 gram per cubic centimeter. The high density of Kevlar is due to the tightly packed molecular structure of PPTA.