Kevlar

Kevlar emerged from a solution that should have been thrown away. In 1964, DuPont chemists began searching for a lightweight fiber to replace steel in automobile tires, anticipating a gasoline shortage that would reward fuel efficiency. Stephanie Kwolek, one of the few women in DuPont's polymer research division, took on the task that other chemists found uninteresting.

The adjacent possible stretched back four decades. Wallace Carothers had joined DuPont in 1928 to pursue "pure science" in polymers—a radical corporate investment that produced neoprene in 1930 and nylon in 1935. Carothers died in 1937, never seeing nylon's commercial triumph, but his systematic investigation of polyamides laid the foundation for everything that followed. By 1965, DuPont understood aramid chemistry well enough for Kwolek to attempt something new: dissolving rigid-rod polymers in solvents to spin them into fibers.

Her solution looked wrong. Polymer solutions should resemble molasses—thick, clear, viscous. Kwolek's poured like water and appeared cloudy, opalescent. Standard practice was to discard such failures as contaminated. But Kwolek insisted on testing it. She was denied access to the spinneret; colleagues feared her strange liquid would clog the expensive machine. Technician Charles Smullen finally agreed to try.

The fiber that emerged would not break. Five times stronger than steel by weight, eight times stronger than titanium per unit density, it derived its power from molecular architecture Kwolek had accidentally achieved: a liquid crystalline arrangement where rigid aromatic chains aligned themselves for spinning. The para-orientation of benzene rings created mostly planar sheets held together by hydrogen bonds and aromatic stacking—a molecular geometry similar to spider silk.

DuPont patented Kevlar in 1966 and commercialized it in 1971. Racing tires came first—ironically, the original goal mostly failed because changing tire manufacturing equipment was too expensive. But the cascade found other outlets: body armor reached police departments in 1975, and on December 23 of that year, Seattle officer Ray Johnson took two shots to the chest at three feet and walked away with bruises. By 2024, over 3,100 officers credited Kevlar vests with saving their lives. The fiber that nearly went down the drain now protects bodies, bridges suspension cables, sheathes fiber optic networks, and reinforces everything from racing sails to aircraft components.