Polymerization. Unit Processes Review

Wallace Hume Carothers and nylon, the first completely synthetic fiber

“…In less than two years he achieved a significant advance by the use of a molecular still (Fig, 3), which allowed polymerization to proceed more nearly to completion by elimination of the water formed in the condensation reactions, resulting in molecular weights of 10,000-20,000. According to Elmer Keiser Bolton (1886-1968), who replaced Stine as Director of the Fundamental Research Program in June 1930, "without this technique Carothers might have failed in his search for superpolymers" (14). Carother's work proved that polymers could be formed by using known organic reactions with reactants containing more than one reactive group per molecule and that the forces binding the individual monomers together are covalent bonds (7).…”

“…Instead, he favored the polyamide prepared from hexamethylenediamine and adipic acid, viz., poly(hexamethylene adipamide) (66) (Fig. 4), insoluble in common solvents and having a melting point of 263 °C, first synthesized by Carothers on February 28,1935, because it possessed the "best balance of properties and manufacturing cost of the polyamides then known" (14).…”

“…In the production of nylon, hexamethylenediamine and adipic acid are reacted to form a salt, which, after purification via crystallization, is polymerized to long-chain polymers of molecular weight above 10,000 in an autoclave with stabilizers and monofunctional reactants added to control molecular weight and viscosity (14). The molten nylon is then extruded as a ribbon, which is cut into small chips that are convenient for storing, handling, and subsequent blending with other batches.…”

“…Properties and Uses of Nylon Before the advent of nylon, the United States and much of the world was dependent on Japan for silk, and this first truly synthetic fiber arrived on the scene just in time to replace the supply of natural silk that was cut off during World War II, More than any other fiber, natural or artificial, nylon is closer in both constitution and properties to silk. Possessing silk's appearance and luster, it has the advantage of greater uniformity and can be spun into filaments of any desired size (14). It also possesses the outstanding combination of great strength, elasticity, toughness, and resistance to abrasion (14,18,20,22,23) because of the great length, great flexibility, and relatively high polymethylene content of the polymer chain, the strength of the forces between the amide groups as well as steric factors favorable to the efficient operation of these forces.…”

“…Possessing silk's appearance and luster, it has the advantage of greater uniformity and can be spun into filaments of any desired size (14). It also possesses the outstanding combination of great strength, elasticity, toughness, and resistance to abrasion (14,18,20,22,23) because of the great length, great flexibility, and relatively high polymethylene content of the polymer chain, the strength of the forces between the amide groups as well as steric factors favorable to the efficient operation of these forces. Because of nylon's lower water absorption than cotton, nylon garments dry more rapidly than cotton ones.…”