DuPont's Kevlar came from a cloudy fluid that spun into ultra-strong fiber.

By the 1960s DuPont's Pioneering Research Laboratory in Wilmington, Delaware was searching for a high-strength, heat-resistant fiber. One line of research involved aromatic polyamides, rigid chain molecules that would, in theory, make a very strong fiber.

The problem was the reaction was brutally sensitive to moisture and heat, so intermediates tended to hydrolyze or self-polymerize. Chemist Stephanie Kwolek found an acceptable solvent and set up low-temperature polymerization conditions. When she went to spin her batch, the cop was fluid and cloudy rather than viscous and clear.

Most researchers would have thrown that dope away. Kwolek, acting on instinct, insisted on spinning it anyway. The result was a fiber far stiffer and stronger than anything made before, because the cloudy appearance came from the rod-like molecules aligning in solution into a liquid-crystal state.

DuPont's lab commercialized it as Kevlar, first marketed in 1971, sold in bulletproof vests and radial tires. The patent for the fiber-with-low-orientation-angle covered the aligned internal structure and method, and was assigned to DuPont.

Cloudy liquid-crystal fluid spins into the strongest fiber

Rigid-rod molecules self-align in a liquid-crystal solution before spinning

Starting from an aligned dope removed the need to stretch molecules into line after the fact

The odd cloudy batch was the sign something new was happening, not a failure

Believing one's own data in the face of convention is where the unique result hides

A cloudy, runny batch can be the sign molecules are behaving differently than expected; checking the odd batch rather than discarding it is what finds the exceptional one.

Kevlar became DuPont's flagship high-performance fiber, used in bulletproof vests, tires, brake pads, sailcloth and aerospace composites. It generated hundreds of millions of dollars a year in sales; Kwolek earned 17 U.S. patents and dozens of honors.