Nylon, formation

MAJOR USES Manufacture of chemicals including acrylic fiber, plastics, rubber elastomers, plasticizers, solvents, polymeric materials, dyes, pharmaceuticals, insecticides and nylon formation of high impact resins such as styrene acrylonitrile and acrylonitrile butadiene styrene. 

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. 

Another example of a cycHc product is the formation of cyclopentanone [120-92-3] as a thermal decomposition product in nylon-6,6 (81,82). The following mechanism (eqs. 8 and 9) accounts not only for the formation of the cycloketone but also for the increase in amine ends, the decrease in acid ends, and the evolution of CO2 that is observed in the thermal decomposition of nylon-6,6 (82). 

The second difficulty, degradation, required the development of a two-step polyamidation process following salt formation (157). During salt formation, tetramethylenediammonium adipate salt is formed in water solution at approximately 50% concentration or at a higher concentration in a suspension. As in nylon-6,6 manufacture, this salt solution, when diluted, permits easy adjustment of the stoichiometry of the reactants by means of pH measurement. 

Its manufacture begins with the formation of dodecanedioic acid produced from the trimeri2ation of butadiene in a process identical to that used in the manufacture of nylon-6,12. The other starting material, 1,12-dodecanediamine, is prepared in a two-step process that first converts the dodecanedioic acid to a diamide, and then continues to dehydrate the diamide to the dinitrile. In the second step, the dinitrile is then hydrogenated to the diamine with hydrogen in the presence of a suitable catalyst. 

Oxidation. AH polyamides are susceptible to oxidation. This involves the initial formation of a free radical on the carbon alpha to the NH group, which reacts to form a peroxy radical with subsequent chain reactions leading to chain scission and yellowing. As soon as molten nylon is exposed to air it starts to discolor and continues to oxidize until it is cooled to below 60°C. It is important, therefore, to minimize the exposure of hot nylon to air to avoid discoloration or loss of molecular weight. Similarly, nylon parts exposed to high temperature in air lose their properties with time as a result of oxidation. This process can be minimized by using material containing stabilizer additives. 

The properties of elastomeric materials are also greatly iafluenced by the presence of strong interchain, ie, iatermolecular, forces which can result ia the formation of crystalline domains. Thus the elastomeric properties are those of an amorphous material having weak interchain iateractions and hence no crystallisation. At the other extreme of polymer properties are fiber-forming polymers, such as nylon, which when properly oriented lead to the formation of permanent, crystalline fibers. In between these two extremes is a whole range of polymers, from purely amorphous elastomers to partially crystalline plastics, such as polyethylene, polypropylene, polycarbonates, etc. 

In the first case a dibasic acid is reacted with diamine to give a polyamide. A specific example is the formation of nylon 66 by the reaction of adipic acid and hexamethy lenediamine. 

Treatment of a nylon with formaldehyde leads to the formation of A-methylol groups but the polymers are unstable. If, however, the nylon is dissolved in the solvent such as 90% formic acid and then treated with formaldehyde and an alcohol in the presence of an acidic catalyst such as phosphoric acid a process of alkoxymethylation occurs Figure 18.19). 

Blends based on polyolefins have been compatibilized by reactive extrusion where functionalized polyolefins are used to form copolymers that bridge the phases. Maleic anhydride modified polyolefins and acrylic acid modified polyolefins are the commonly used modified polymers used as the compatibilizer in polyolefin-polyamide systems. The chemical reaction involved in the formation of block copolymers by the reaction of the amine end group on nylon and anhydride groups or carboxylic groups on modified polyolefins is shown in Scheme 1. 

One of the earliest references on compatibilizing a nylon-6-polypropylene blend using maleic anhydride grafted PP (PP-g-MAH) was the work of Ide and Hase-gawa published in 1974 [35]. In their study, the formation of a graft copolymer was confirmed by DSC after solvent extraction of the PP component. Blends with PP-g-MAH... 

Fibers in which the basic chemical units have been formed by chemical synthesis, followed by fiber formation, are called synthetic fibers. Examples include nylon, carbon, boron fibers, organic fibers, ceramic fibers, and metallic fibers. Among all commercially available fibers, Kevlar fibers exhibit high strength and modulus. (Kevlar is a DuPont trademark for poly [p-phenylene diamine terephthalamide].) It is an aromatic polyamide (aramid) in which at least 85% of the... 

KA oil is used to produce caprolactam, the monomer for nylon 6. Caprolactam is also produced from toluene through the intermediate formation of cyclohexane carboxylic acid. 

Numbers that follow the word nylon denote the number of carbons present within a repeating unit and whether one or two monomers are being used in polymer formation. For nylons using a single monomer such as nylon 6 or nylon 12, the numbers 6 and 12 denote the number of carbons in caprolactam and laurolactam, respectively. For nylons using two monomers such as nylon 610, the first number, 6, indicates the number of carbons in the hexamethylene diamine and the other number, 10, is for the second monomer sebacic acid. 

The temperature is then increased to 270-300°C and the pressure to approximately 16 atmospheres, which favors the formation of the polymer. The pressure is finally reduced to atmospheric to permit further water removal. After a total of three hours, nylon 66 is extruded under nitrogen pressure. 

DNA microarrays, or DNA chips consist of thousands of individual DNA sequences arrayed at a high density on a single matrix, usually glass slides or quartz wafers, but sometimes on nylon substrates. Probes with known identity are used to determine complementary binding, thus allowing the analysis of gene expression, DNA sequence variation or protein levels in a highly parallel format. 

Amine salts of a-sulfonated fatty acids and esters are also used as antistatic agents. Mixtures of alkyl a-sulfo fatty acid ester diethanolamine salts and hexa-decyl stearate or butyl stearate are coated onto nylon yarn after fiber formation and before stretching [97]. Polypropylene can be made antistatic with an amine salt of a-sulfolauric acid [C10H21CH(SO3Na)COO +NH(CH2CH(OH) CH3)3] [98]. 

Mond process The purification of nickel by the formation and decomposition of nickel carbonyl, monomer A small molecule from which a polymer is formed. Examples CH2=CH2 for polyethylene NH2(CH2)6NH2 for nylon, monoprotic acid A Bronsted acid with one acidic hydrogen atom. Example CH COOI I. monosaccharide An individual unit from which carbohydrates are considered to be composed. Example C6H(206, glucose, multiple bond A double or triple bond between two atoms. 

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