Kwolek accepted a position as a chemist at DuPont's Buffalo, New York, research facility. This decision would alter her career aspirations significantly, leading her to abandon her plans for medical school.

Kwolek was transferred to DuPont's Pioneering Research Laboratory in Wilmington, Delaware. This laboratory was specifically designed to support research into new fibers and polymers.

While searching for a new lightweight tire cord material, Kwolek discovered an unusual polymer solution that was opaque and shimmering, unlike the clear, syrupy solutions she was used to. Her colleagues initially dismissed it, but Kwolek convinced them to test it.

The unusual solution spun into fibers that were significantly stronger than nylon, which was the leading synthetic fiber at the time. This discovery revolutionized the field of materials science.

After further development and refinement, Kevlar was commercially introduced in 1971. It quickly found widespread applications, most notably in bulletproof vests, but also in tires, brake pads, and countless other products.

Kwolek officially retired from DuPont after 40 years of service, leaving behind a legacy of innovation and scientific achievement. Even after retirement, she continued to consult for DuPont and remained active in the scientific community.