Nylon

Nylon is a generic designation for a family of synthetic polymers known generically as aliphatic polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station. Nylon is one of the most common polymers used as a fiber. Nylon is used to make clothing all the time, but also in other places, in the form of a thermoplastic. Nylon's first real success came with it's use in women's stockings, in about 1940. They were a big hit, but they became hard to get, because the next year the United States entered World War II, and nylon was needed to make war materials, like parachutes and ropes. But before stockings or parachutes, the very first nylon product was a toothbrush with nylon bristles.  

        Nylons are also called polyamides, because of the characteristic amide groups in the backbone chain. Proteins, such as the silk nylon was made to replace, are also polyamides. These amide groups are very polar, and hydrogen can bond with each other. Because of this, and because the nylon backbone is so regular and symmetrical, nylons are often crystalline, and produce very good fibers. Nylons are condensation copolymers formed by reacting equal parts of a diamine and a dicarboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Chemical elements included are carbon, hydrogen, nitrogen, and oxygen. The numerical suffix specifies the numbers of carbons donated by the monomers; the diamine first and the diacid second. The most common variant is nylon 6-6 which refers to the fact that the diamine (hexamethylene diamine, IUPAC name: hexane-1,6-diamine) and the diacid (adipic acid, IUPAC name: hexanedioic acid) each donate 6 carbons to the polymer chain. As the "repeating unit" consists of one of each monomer, copolymers alternate in the chain. Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins which have overall directionality: C terminal → N terminal.

      In the laboratory, nylon 6-6 can also be made using adipoyl chloride instead of adipic acid. It is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an exact 1:1 ratio of the acid and the base to neutralize each other. Heated to 285 °C (545 °F), the salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the chains into yarn, so to combat this, some acetic acid is added to react with a free amine end group during polymer elongation to limit the molecular weight. In practice, and especially for 6,6, the monomers are often combined in a water solution. The water used to make the solution is evaporated under controlled conditions, and the increasing concentration of "salt" is polymerized to the final molecular weight.

      There are some characteristics for nylon. Nylon has the ability to be very lustrous, semilustrous or dull. Nylon's high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses. Besides that, nylon is high elongation and excellent in abrasion resistance. It is highly resilient. Paved the way for easy-care garments. High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals are the characteristics of nylons too. It is used in carpets, nylon stockings and in many military applications. Nylon has good specific strength and is transparent to infrared light (−12dB).

      These are some of the photo of nylon structure and nylon product:

All the above are the products that made by nylon.

     

      Above are the chemical structure of nylon.