Man-Made Fibers: Nylon The first man-made fibers were regenerated cellulose from plants, which were

3.2.2 Man-Made Fibers: Nylon The first man-made fibers were regenerated cellulose from plants, which were

called semisynthetic fiber. In 1878, Count Hilaire de Chardonnet worked on devel- oping an artificial fiber and obtained a patent for making this fiber. He treated cellu- lose from cotton or wood fibers in a solution of nitric acid and then extruded the solution of partially nitrated cellulose through a small hole, which created a filament that is somewhat flammable. In 1891, he opened a factory in Besancon to produce the world’s first man-made fiber that he called rayon. The following year in England, Charles Cross invented viscose rayon by digesting cellulose from cotton lint or wood pulp by sodium hydroxide, and further treating it with carbon disulfide to create a viscous fluid called cellulose xanthate. This viscous fluid is forced under high pressure through numerous holes in a spinneret to form fibers and spun in a bath of sulfuric acid to remove the alkali. The same viscous solution could be used to make transparent films that were called cellophane. Viscose rayon did not have the strength or glamour of silk and is used today mainly as the smooth and slippery linings for coats and sleeves.

Nylon was the first fully synthetic fiber, where the starting materials were air, water, coal tar, and petroleum. The invention of nylon involved an intellectual dis- covery provided by Wallace Carothers and his associates and required a sustained development effort by a large team of scientists and engineers at the DuPont Corporation. It was one of the most impressive inventions that ushered in an age of man-made materials through chemistry.

Wallace Hume Carothers was born in Iowa in 1896, and attended Capital City Commercial College in Des Moines, Iowa, in a program of accountancy and secre- tarial administration. He struggled to find the funds for his education, but went on to the 4-year Tarkio College in Missouri to complete a bachelor’s degree in chemistry and then taught chemistry for a year at the University of South Dakota. His thyroid gland malfunctioned and he suffered spells of melancholy and pessimism. He was also interested in music and poetry, and was a person of culture and charm.

101 His prospects greatly improved when he received encouragement from a teacher at

3.2 CLOTHES

Tarkio, and thus proceeded to the University of Illinois for graduate school where he earned his doctorate in 1924. Thereafter, he joined Harvard University as an instruc- tor pursuing research in polymers. At that time, the nature of substances such as silk and rubber was still in doubt. Herman Staudinger proposed the polymer theory that they were long chains of small units called “monomers” held together by ordinary chemical bonds, but this idea had many skeptics.

The DuPont Company of Delaware made and sold gunpowder for the United States and its allies in several wars, which was very profitable. In peacetime, it began seeking diversification into many other chemical technologies, including rayon for inexpensive clothing, nitrocellulose for colorful automobile lacquer, and tetraethyl lead for automobile gasoline. In 1926, Charles Stine of DuPont proposed the new concept of a corporate research unit to discover or establish new scientific facts, as a supplement to the traditional pursuit of applying known scientific facts to practical problems. He was encouraged by several university consultants, as well as by the research directors of the older research programs at Bell Telephone and Gen- eral Electric. Stine recruited Carothers from Harvard in 1928, despite Carothers’ interest in pure research and lack of interest in financial profit. But Stine assured him that he could choose his own research problems at DuPont.

Carothers began several programs to study complex molecules, and one of them produced practical results rather quickly. Julius Nieuwland of Notre Dame University produced divinyl acetylene, which forms an elastic jelly. Carothers assigned an assistant Collins the task to purify divinyl acetylene by distillation. In 1930, Collins left the distillation results over the weekend and by Monday he found that it had solidified into a cauliflower-shaped mass. He fished out a few cubic centi- meters of the substance, which felt strong and elastic. Collins threw the mass against his laboratory bench, and it bounced like a golf ball. In a remarkably short time, Carothers’ research led to the development of neoprene in 1930, which became the first mass-produced synthetic rubber. Neoprene is chemically inert and fire resistant, and is used for industrial applications such as hoses and coatings. Carothers is shown in his laboratory pulling on a piece of material in Figure 3.3.

Wallace Carothers believed in the Herman Staudinger theory that polymers are made of long chains of monomer units, and he tried to make an experiment to demonstrate the theory. He proposed building long-chain molecules one step at a time, by carrying out well-understood chemical reactions. His first scheme was to react dihydric alcohol with OH groups on both ends, together with diacid mole- cules with acid groups COOH