Commercial applications nylon

Wallace Carothers and coworkers at DuPont synthesized aliphatic polyesters in the 1930s [Furukawa, 1998 Hounshell and Smith, 1988]. These had melting points below 100°C, which made them unsuitable for firber use. Carothers then turned successfully to polyamides, based on the theoretical consideration that amides melt higher than esters. Polyamides were the first synthetic fibers to be produced commercially. The polyester and polyamide research at DuPont had a major impact on all of polymer science. Carothers laid the foundation for much of our understanding of how to synthesize polymeric materials. Out of that work came other discoveries in the late 1930s, including neoprene, an elastomer produced from chloro-prene, and Teflon, produced from tetrafluoroethylene. The initial commercial application for nylon 6/6 was women s hosiery, but this was short-lived with the intrusion of World War II. The entire nylon 6/6 production was allocated to the war effort in applications for parachutes, tire cord, sewing thread, and rope. The civilian applications for nylon products burst forth and expanded rapidly after the war. 

Because of the capacity to tailor select polymer properties by varying the ratio of two or more components, copolymers have found significant commercial application in several product areas. In fiber-spinning, ie, with copolymers such as nylon-6 in nylon-6,6 or the reverse, where the second component is present in low (<10%) concentration, as well as in other comonomers with nylon-6,6 or nylon-6, the copolymers are often used to control the effect of spherulites by decreasing their number and probably their size and the rate of crystallization (190). At higher ratios, the semicrystalline polyamides become optically clear, amorphous polymers which find applications in packaging and barrier resins markets (191). 

As more complex multicomponent blends are being developed for commercial applications, new approaches are needed for morphology characterization. Often, the use of Ru04 staining is effective, as it is sensitive to small variations in the chemical composition of the component polymers. For instance PS, PC, and styrene—ethylene/butylene—styrene block copolymers (SEBS) are readily stained, SAN is stained to a lesser degree, and PBT and nylons are not stained (158,225—228). 

Condensation polymers based on an amide linkage have also found considerable commercial applications. For example, when the salt of adipic acid and hexamethyl-enediamine is heated to 270°C, a polyamide known as nylon 6,6 is formed. (The first number in the name of the nylon designates the number of carbons in the diamine, six in this case, and the second designates number of carbons in the diacid, also six in this case, that are used to form the nylon.)... 

Organic matrices are divided into thermosets and thermoplastics. The main thermoset matrices are polyesters, epoxies, phenolics, and polyimides, polyesters being the most widely used in commercial applications (3,4). Epoxy and polyimide resins are applied in advanced composites for structural aerospace applications (1,5). Thermoplastics Uke polyolefins, nylons, and polyesters are reinforced with short fibers (3). They are known as traditional polymeric matrices. Advanced thermoplastic polymeric matrices like poly(ether ketones) and polysulfones have a higher service temperature than the traditional ones (1,6). They have service properties similar to those of thermoset matrices and are reinforced with continuous fibers. Of course, composites reinforced with discontinuous fibers have weaker mechanical properties than those with continuous fibers. Elastomers are generally reinforced by the addition of carbon black or silica. Although they are reinforced polymers, traditionally they are studied separately due to their singular properties (see Chap. 3). 

Polyamides are obtained either by the condensation of a dicarboxylic acid and an alkylene diamine or by the head-to-tail condensation between an amino carboxylic acid or the corresponding lactam. Polyamides may have aliphatic or aromatic chain backbones. Aliphatic polyamides (nylon) have the most important commercial applications, mainly in the manufacture of fibres. Nylon-6 and nylon-6,6 account for around 85% of all nylon currently used. Nylon-6 is derived from the polymerization of e-caprolactam, whereas nylon-6,6 is obtained by the condensation of hexamethylene diamine and adipic acid. 

Nylons are used in applications requiring durability, toughness, chemical inertness, electrical insulating properties, abrasion and low frictional resistance, and self-lubricating properties. Table 15.13 lists markets and typical applications of nylons. In many of these applications, nylons are used as small parts or elements in subassemblies of the finished commercial article. 

Since 1930, the growth in the number of polymers and their applications has been immense. During the 1930s, industrial chemical companies initiated fundamental research programs that had a tremendous impact on our society. For example, Wallace Carothers, working at DuPont de Nemours and Co., deveioped diverse polymeric materials of defined structures and investigated how the properties of these materials depend on their structure. In 1939 this program resuited in the commercialization of nylon. 

Except for fiber production, commercial polyamides are produced in the form of chips for use in molding, composite, resin compounding, and numerous industrial applications. Nylon-... 

Polyipropylene terephthalate), more often referred to as poly(trimethylene terephthalate) (PTT), was identified from research into aromatic polyesters, but was not commercialised at the time due to difficulty in obtaining pure, low-cost, 1,3-propanediol. Finally introduced into large-scale production in the late 1990s, there are great hopes for commercial application of this polymer, especially as a fibre. In general, it has properties between those of PET and PBT, but has certain unique properties of its own, including superior resilience and wear properties, giving carpets tufted with such fibres physical properties akin to the nylons, and stain resistance similar to PET. 

Substituted nylon 1 types (—NR—CO—) are obtained by polymerization of isocyanates, RNCO, with, for example, KCN as initiator in solvents such as dimethyl formamide. The products have no commercial application. 

Commercial applications have been proposed that use high average power free-electron lasers to heat the surface of polymers for enhancements to the surface morphology. This uses infrared at 5.8 to 6.2-/rm wavelengths where high absorption results from carbonyl-related molecular absorption bands. By enhancing surface roughness in polyester and nylon fibers, the fabrics can be made softer, hydrophilic, and the material more readily accepts dyes. 

Wallace Hume Carothers (Figure 25.5), the discoverer of nylon, was 31 years old in 1928 when he left Harvard University for the DuPont Company. (He had obtained his Ph.D. four years earlier in organic chemistry at the University of Illinois.) DuPont had decided to establish a group devoted to fundamental research, an idea that was rather novel at the time. The plan was that Carothers would work in an area that, while potentially useful to the company, did not have to have immediate commercial application. 

Though the nylons originally were developed for their fiber-forming characteristics, their first commercial application was for toothbrush bristles, and shortly thereafter they were used for women s stockings. Not only are they drawn into monofilament and spun into fiber they are extruded into film and tubing, blow-molded into bottles, injection-molded... 

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