A leader of that effort was Wallace Carothers, a young chemist at E. I. du Pont de Nemours & Company. In 1930 he and his research team created neoprene, a synthetic rubber that was more resistant to corrosive chemicals than vulcanized natural rubber. The team then began trying to develop a synthetic fiber from organic building blocks that would bond in the same way amino acids join up to form the protein molecules in silk. The payoff came in 1934 when one of the researchers dipped a rod into a beaker full of syrupy melt. When he pulled the rod out, a thread of the viscous substance came with it, and the stretching and subsequent curing of the strand transformed it into a substance of remarkable strength and elasticity. This was nylon, soon produced in quantity for stockings, toothbrush bristles, and such wartime uses as parachute cloth, ropes, and reinforcement for tires. Because of its low friction and high resistance to wear, nylon also proved valuable for gears, rollers, fasteners, and zippers. The menu of valuable polymers continued to grow steadily. Polyethylenes, suitable for making bottles, appeared in 1939. Polyester fibers, destined to be a staple of the apparel industry, arrived in 1941. A vinyl-based transparent film called Saran, useful for wrapping food, was developed in 1943. Dacron, whose applications ranged from upholstery to grafts to repair blood vessels, hit the market in 1953. Lycra spandex fiber that could stretch as much as five times its length without permanent deformation was introduced in 1958. Kevlar, a fiber five times stronger than steel on a density-adjusted basis, was launched in 1973. By 1979 the annual production volume of polymers surpassed that of all metals combined. A famously pithy bit of career advice in The Graduate, a late 1960s film, summed up the situation well: when the hero asks someone about promising fields for employment, he is told simply, "plastics."
Ceramics, which include all inorganic nonmetallic materials, constitute another high performance category. Some of them are commonplace. The cement and concrete used for highways and other construction purposes are manufactured in greater volume than any other product. At the opposite extreme are synthetic diamonds, first made by General Electric in 1955 by subjecting graphite to temperatures above 3,000°F and pressures of more than a million pounds per square inch. Diamond is a paragon among materials in many ways—the hardest of all substances, the most transparent, the best electric insulator, with the highest thermal conductivity and highest melting point. As grit or small crystals, synthetic diamonds give an ultrahard coating to such industrial equipment as grinding wheels or mining drills. In addition, diamond films for optical or electronic applications can be grown by heating a carbon-containing gas such as methane to very high temperatures at low pressures. Other ceramics include oxides, carbides, nitrides, and borides, all of them very hard, brittle and resistant to corrosion, high temperatures, and electric current. Some ceramics are so strong that they have replaced steel as the armor for military vehicles. Ceramics, which include all inorganic nonmetallic materials, constitute another high performance category. Some of them are commonplace. The cement and concrete used for highways and other construction purposes are manufactured in greater volume than any other product. At the opposite extreme are synthetic diamonds, first made by General Electric in 1955 by subjecting graphite to temperatures above 3,000°F and pressures of more than a million pounds per square inch. Diamond is a paragon among materials in many ways—the hardest of all substances, the most transparent, the best electric insulator, with the highest thermal conductivity and highest melting point. As grit or small crystals, synthetic diamonds give an ultrahard coating to such industrial equipment as grinding wheels or mining drills. In addition, diamond films for optical or electronic applications can be grown by heating a carbon-containing gas such as methane to very high temperatures at low pressures. Other ceramics include oxides, carbides, nitrides, and borides, all of them very hard, brittle and resistant to corrosion, high temperatures, and electric current. Some ceramics are so strong that they have replaced steel as the armor for military vehicles. Perhaps nowhere has the promise of ceramics been more tantalizing than in the quest for materials called superconductors, which can carry electric current with zero resistance—that is, without giving up any of the energy as heat. The phenomenon of superconductivity was discovered back in 1911 by Dutch physicist Kamerlingh Onnes. He cooled mercury to 4.2 K (-452°F), just 4 degrees above absolute zero, and observed that all electrical resistance disappeared. (Scientists commonly use the Kelvin scale for studies in the realm of the supercold, with temperatures measured in Kelvin (K). On this scale, water boils at 373 K and freezes at 273 K; absolute zero is the temperature at which molecular motion theoretically ceases.) Because such low temperatures are difficult to reach, there was much excitement in the mid-1980s when IBM researchers in Switzerland found that the ceramic lanthanum-barium-copper oxide becomes a superconductor at 35 K (-406°F). The discovery of this new class of superconductors stirred hopes of identifying substances that superconduct with no chilling at all. A decade later the threshold was up to 135 K (-217°F), but prospects for reaching still higher levels remain unclear. If they can be attained and the materials can be reliably and inexpensively fashioned into wires (not easy with brittle ceramics), the technological consequences would be immense.
Big performance gains are already well in hand for the class of materials called composites in which one type of material is reinforced by particles, fibers, or plates of another type. Among the first engineered composites was fiberglass, developed in the 1930s. Made by embedding glass fibers in a polymer matrix, it found use in building panels, bathtubs, boat hulls, and other marine products. Since then, many metals, polymers, and ceramics have been exploited as both matrix and reinforcement. In the 1960s, for instance, the U.S. Air Force began seeking a material that would be superior to aluminum for some aircraft parts. Boron had the desired qualities of lightness and strength, but it wasn't easily formed. The solution was to turn it into a fiber that was run through strips of epoxy tape; when laid in a mold and subjected to heat and pressure, the strips yielded strong, lightweight solids—a tail section for the F-14 fighter jet, for one. While an elegant solution, boron fibers were too expensive to find wide use, highlighting the critical interplay between cost and performance that drives materials applications.
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