Linear nylon

Caprolactam is an amide and, therefore, undergoes the reactions of this class of compounds. It can be hydrolyzed, Ai-alkylated, O-alkylated, nitrosated, halogenated, and subjected to many other reactions (3). Caprolactam is readily converted to high molecular weight, linear nylon-6 polymers. Through a complex series of reactions, caprolactam can be converted to the biologically and nutritionally essential amino acid L-lysine (10) (see Amino acids). 

The thin films of the nylon samples that were melt-pressed for FTIR examination gave similar results. Linear samples pressed out easily to make thin films that were excellent for IR evaluation. Star branched materials would not press thin enough to give good spectra even at maximum press pressure. It was originally hoped that star and linear nylons would have different crystal structure forms (JL4) unfortunately, FTIR has shown little differences other than those that occur from differences in sample preparation (Figure 5). 

The star-branched and two-armed systems appear to have enhanced entanglements or crosslinked networks that allow them to maintain their forms at temperatures above the linear nylon 6 melt temperature. Both the star-branched and two-armed species have melt temperatures slightly below that of single-armed nylon 6. The di-armed nylon appears to have properties similar to both the singlearmed and the star species. 

In step-growth polymerizations of commercial linear polymers the degrees of conversion are clo.se to unity. Thus, for linear nylons and polyesters, Mv//M is close to 2 as indicated by Eq. (5-36) with p =. ... 

The molecular weights of nylon-6 are generally in the same range as nylon-6,6. Its molecular weight distribution as prepared under the above conditions is also the same as linear nylon-6,6 and other linear condensation polymers with M /M = +p,or about two. However, nylon-6 and AB polyamides are unique in that a narrower molecular weight distribution can be attained by adding a bifunctional stabilizer such as the Bb-type dicarboxylic add [37]. An AB polymer chain can only pick up one BB unit and becomes terminated with B end groups at both ends. For example, if 40 equiv. 10 g. of BB units are added and the concentration of A ends [NH2] is reduced to 10 equiv. 10 g, M jM = 1.6. It would be possible to increase by 25% in that case. 

The following conditions are required in order to obtain high-molecular-weight linear Nylon 6-6 ... 

The abihty of a fiber to absorb energy during straining is measured by the area under the stress—strain curve. Within the proportional limit, ie, the linear region, this property is defined as toughness or work of mpture. For acetate and triacetate the work of mpture is essentially the same at 0.022 N/tex (0.25 gf/den). This is higher than for cotton (0.010 N/tex = 0.113 gf/den), similar to rayon and wool, but less than for nylon (0.076 N/tex = 0.86 gf/den) and silk (0.072 N/tex = 0.81 gf/den) (3). 

However, because of the low melting poiats and poor hydrolytic stabiUty of polyesters from available iatermediates, Carothers shifted his attention to linear ahphatic polyamides and created nylon as the first commercial synthetic fiber. It was nearly 10 years before. R. Whinfield and J. T. Dickson were to discover the merits of poly(ethylene terephthalate) [25038-59-9] (PET) made from aromatic terephthaUc acid [100-21-0] (TA) and ethylene glycol [107-21-1] (2G). 

The majority of spunbonded fabrics are based on isotactic polypropylene and polyester (Table 1). Small quantities are made from nylon-6,6 and a growing percentage from high density polyethylene. Table 3 illustrates the basic characteristics of fibers made from different base polymers. Although some interest has been seen in the use of linear low density polyethylene (LLDPE) as a base polymer, largely because of potential increases in the softness of the final fabric (9), economic factors continue to favor polypropylene (see OlefinPOLYMERS, POLYPROPYLENE). 

Ingredients. Nylon-6,6 is made from the reaction of adipic acid [124-04-9] and hexamethylenediamine [124-09-4]. The manufacture of intermediates for polyamides is extremely important not only is the quaUty of the polymer, such as color, degree of polymerization, and linearity, strongly dependent on the ingredient quaUty, but also the economic success of the producer is often determined by the yields and cost of manufacture of the ingredients. 

One of the butadiene dimeri2ation products, COD, is commercially manufactured and used as an intermediate in a process called FEAST to produce linear a,C0-dienes (153). COD or cyclooctene [931-87-3], obtained from partial hydrogenation, is metathesi2ed with ethylene to produce 1,5-hexadiene [592-42-7] or 1,9-decadiene [1647-16-1], respectively. Many variations to make other diolefins have been demonstrated. Huls AG also metathesi2ed cyclooctene with itself to produce an elastomer useful in mbber blending (154). The cycHc cis,trans,trans-tn.en.e described above can be hydrogenated and oxidi2ed to manufacture dodecanedioic acid [693-23-2]. The product was used in the past for the production of the specialty nylon-6,12, Qiana (155,156). 

Rhodium catalyst is used to convert linear alpha-olefins to heptanoic and pelargonic acids (see Carboxylic acids, manufacture). These acids can also be made from the ozonolysis of oleic acid, as done by the Henkel Corp. Emery Group, or by steam cracking methyl ricinoleate, a by-product of the manufacture of nylon-11, an Atochem process in France (4). Neoacids are derived from isobutylene and nonene (4) (see Carboxylic acids, trialkylacetic acids). 

Reaction-Injection Molding and Reactive Casting. Reaction-iajection molding (RIM) (22) and reactive casting (23) have been demonstrated on nylon-6, which is polymerized by catalytic ring opening and linear recondensation of S-caprolactam (qv) (24). 

Nylon, also a linear polymer, is made by a condensation reaction. Two different kinds of molecule react to give a larger molecule, and a by-product (usually HjO) the ends of large molecules are active, and react further, building a polymer chain. Note how molecules of one type condense with those of the other in this reaction of two symmetrical molecules... 

Carothers also produced a number of aliphatic linear polyesters but these did not fulfil his requirements for a fibre-forming polymer which were eventually met by the polyamide, nylon 66. As a consequence the polyesters were discarded by Carothers. However, in 1941 Whinfield and Dickson working at the Calico Printers Association in England announced the discovery of a fibre from poly(ethylene terephthalate). Prompted by the success of such a polymer, Farbenfabriken Bayer initiated a programme in search of other useful polymers containing aromatic rings in the main chain. Carbonic acid derivatives were reacted with many dihydroxy compounds and one of these, bis-phenol A, produced a polymer of immediate promise. 

Linear polyesters were studied by Carothers during his classieal researches into the development of the nylons but it was left to Whinfield and Dickson to discover polyfethylene terephthalate) (BP 578079), now of great importance in the manufacture of fibres (e.g. Terylene, Dacron) and films (e.g. Melinex, Mylar). The fibres were first announced in 1941. 

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