Nylons monomers

Monomer Nylon type Monomer Formula Approximate M.P. °C ... 

Table 2.2 shows two common polymers that are formed by condensation. Notice that DacronT", a polyester, contains ester linkages between monomers. Nylon-6, a polyamide, contains amide linkages between monomers. 

Condensation fibers such as nylon and polyethylene terephthalate are formed when two or more different monomers react, releasing small molecules such as water, and forming amide or ester bonds between the monomers. Nylon, first produced by DuPont in 1938, became a mainstay of the hosiery industry and is now the most widely used fiber in carpet manufacture. Polyethylene terephthalate, produced by formation of an ester bond between terephthalic acid and ethylene glycol, is by far the most widely used synthetic fiber. 

Why might one monomer nylon and one monomer polyester polymers be easier to reprocess to the original monomer than those condensation polymers which contain two or more monomers ... 

These DEF systems are generally mounted on the side of the frame of the vehicle. The fill point is generally under hood. The actual diesel emissions fluid is a 35% urea-water mixture. Because this mixture freezes at -11°C, a heated EPDM (ethylene-propylene diene monomer)/nylon 6,6 line is used to deliver the urea from the tank to the exhaust stream. A sensor controls the flow of the urea to obtain the NOx reduction. This system can reduce NOx emissions by up to 40%. The urea refill rate is about once every 3 months based on typical driving schedules. 

Polyester is created through ester linkages between monomers, which involve the functional groups like carboxyl and hydroxyl (an organic acid and an alcohol monomer). Nylon is another common condensation polymer, which can be prepared by reacting diamines with carboxyl derivatives. In this example, the derivative is a dicarboxylic... 

Polyamide is a polymer formed from condensation of dicarbonic acids and diamines or from condensation of amino acids and lactames. In publications, in English, polyamids are called nylon. To distingmsh them from one another a number is added that represents the number of C-atoms of the monomer or monomers. Nylon type 6.6 (polyamide 6.6) is the most common commercial grade of nylon. It consists of hexamethylene diamine and adipinic acid. 

The product that forms between the reaction of two monomers is called a dimer. The pol5mier (nylon 6,6) shown here forms as the dimer continues to add more monomers. Nylon 6,6 and other similar nylons can be drawn into fibers and used to make consumer products such as pantyhose, carpet fibers, and fishing line. Table 18.8 shows otiier condensation polymers. 

It is, of course, not necessary to use a derivative of ethylene as a monomer. Nylon (polyamide) consists of monomers containing an amino group (NCHO) in polydimethylsiloxane the chain itself consists of alternating silicon and oxygen atoms, with two methyl groups being linked to the silicon atoms. 

Copolymer A polymer made of different monomers nylon is a copolymer. 

Polyamides are formed by condensation polymerisation between an amine group and a carboxylic acid group. These groups may be in the same monomer or on different monomers. Nylon 6,6... 

Nylon 6, 11, and 12. This class of polymers is polymerized by addition reactions of ring compounds that contain both acid and amine groups on the monomer. 

Other nylons are made this way from direct combinations of monomers to produce types 6/9, 6/10, and 6/12. 

As with polyesters, the amidation reaction of acid chlorides may be carried out in solution because of the enhanced reactivity of acid chlorides compared with carboxylic acids. A technique known as interfacial polymerization has been employed for the formation of polyamides and other step-growth polymers, including polyesters, polyurethanes, and polycarbonates. In this method the polymerization is carried out at the interface between two immiscible solutions, one of which contains one of the dissolved reactants, while the second monomer is dissolved in the other. Figure 5.7 shows a polyamide film forming at the interface between an aqueous solution of a diamine layered on a solution of a diacid chloride in an organic solvent. In this form interfacial polymerization is part of the standard repertoire of chemical demonstrations. It is sometimes called the nylon rope trick because of the filament of nylon produced by withdrawing the collapsed film. 

Since adipic acid has been produced in commercial quantities for almost 50 years, it is not surprising that many variations and improvements have been made to the basic cyclohexane process. In general, however, the commercially important processes stiU employ two major reaction stages. The first reaction stage is the production of the intermediates cyclohexanone [108-94-1] and cyclohexanol [108-93-0], usuaHy abbreviated as KA, KA oil, ol-one, or anone-anol. The KA (ketone, alcohol), after separation from unreacted cyclohexane (which is recycled) and reaction by-products, is then converted to adipic acid by oxidation with nitric acid. An important alternative to this use of KA is its use as an intermediate in the manufacture of caprolactam, the monomer for production of nylon-6 [25038-54-4]. The latter use of KA predominates by a substantial margin on a worldwide basis, but not in the United States. 

Caprolactam Extraction. A high degree of purification is necessary for fiber-grade caprolactam, the monomer for nylon-6 (see Polyamides). Cmde aqueous caprolactam is purified by solvent extractions using aromatic hydrocarbons such as toluene as the solvent (233). Many of the well-known types of column contactors have been used a detailed description of the process is available (234). 

Rayon is unique among the mass produced man-made fibers because it is the only one to use a natural polymer (cellulose) directly. Polyesters, nylons, polyolefins, and acryflcs all come indirectly from vegetation they come from the polymerization of monomers obtained from reserves of fossil fuels, which in turn were formed by the incomplete biodegradation of vegetation that grew millions of years ago. The extraction of these nonrenewable reserves and the resulting return to the atmosphere of the carbon dioxide from which they were made is one of the most important environmental issues of current times. CeUulosic fibers therefore have much to recommend them provided that the processes used to make them have minimal environmental impact. 

Without other alternatives, the carboxyalkyl radicals couple to form dibasic acids HOOC(CH)2 COOH. In addition, the carboxyalkyl radical can be used for other desired radical reactions, eg, hydrogen abstraction, vinyl monomer polymerization, addition of carbon monoxide, etc. The reactions of this radical with chloride and cyanide ions are used to produce amino acids and lactams employed in the manufacture of polyamides, eg, nylon. 

The resulting hexarnethylenediarnine can then be reused to produce new nylon-6,6. Impurities or contaminants from monomers of other types of polyamides can be readily removed by distillation from either the nitriles or diamine. 

Nylon-12. Laurolactam [947-04-6] is the usual commercial monomer for nylon-12 [24937-16-4] manufacture. Its production begins with the mixture of cyclododecanol and cyclododecanone which is formed in the production of dodecanedioic acid starting from butadiene. The mixture is then converted quantitatively to cyclododecanone via dehydrogenation of the alcohol at 230—245°C and atmospheric pressure. The conversion to the lactam by the rearrangement of the oxime is similar to that for caprolactam manufacture. There are several other, less widely used commercial routes to laurolactam (171). 

Nylon-6 is the polyamide formed by the ring-opening polymerization of S-caprolactam. The polymerization of S-caprolactam can be initiated by acids, bases, or water. Hydrolytic polymerization initiated by water is often used in industry. The polymerization is carried out commercially in both batch and continuous processes by heating the monomer in the presence of 5—10% water to temperatures of 250—280°C for periods of 12 to more than 24 h. The chemistry of the polymerization is shown by the following reaction sequence. 

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