Other Commercial Nylons

Other commercially important polyamides include nylon 11, nylon 12, nylon 46, nylon 610 ( nylon six ten ) and nylon 612 ( nylon six twelve ), the chemical structures of which are shown in Fig. 23.5. 

There are three methods by which we commercially manufecture nylons. We make nylons of the AB type by hydrolytic ring opening reactions of lactams and the self condensation of co-amino acids. Nylons of the AABB type are made from diamines and diacids via an intermediate knotvn as a nylon salt. 

---

As may be expected from its structure, nylon 46 has a higher level of water absorption (about 14% in water at 23 °C) than any of the other commercial nylons... 

Some of the monomers commonly used to prepare the nylon resins are shown in Ihe accompanying table. Both petrochemical and vegetable products provide the source materials that are transformed into the reactive intermediates. Tile table correctly suggests that there is a wider choice in diacids than in diamines. The most important commercial polyamide resins are nylons-66 and -6. Other commercial nylons include 610, 612, 11, and 12. 

Nylon-6,6 [32131 -17-2J is a tough, translucent white, semiciystalline, high melting (T , = 265 C) material. The common physical properties ate shown in Table 9, and principal producers woddwide in Table 10, for nylon-6,6 and other commercial polyamides. 

Nylon. Nylons comprise a large family of polyamides with a variety of chemical compositions (234,286,287). They have excellent mechanical properties, as well as abrasion and chemical resistance. However, because of the need for improved performance, many commercial nylon resins are modified by additives so as to improve toughness, heat fabrication, stabiUty, flame retardancy, and other properties. 

Commercial engineering thermoplastic nylons are mainly crystalline resins. Nylon-6,6 [32131 -17-2] is the largest volume resin, followed by nylon-6 (48). Other commercially available but much lower volume crystalline nylons are -6,9, -6,10, -6,12, -11, and -12. The crystallinity of the molded part decreases with chain size (49). A few truly amorphous commercial nylon resins contain both aromatic and ahphatic monomer constituents (50). For example, Trogamid T resin is made from a mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamines and terephthahc acid (51). 

Self-lubricating grades are of particular value in some gear and bearing applications. One commercial nylon compound incorporates 0.20% molybdenum disulphide and 1 % of graphite whilst many other commercial compounds contain only one of these two lubricants. 

As mentioned a moment ago, nylons are condensation or step polymers and, because of this, they are different from all of the other commercially important polymers described so far. The nylons are distinguished from each other by a numbering system based on the number of carbon atoms in the starting materials. Thus, nylon 6,6, which was first prepared in 1935 and is still the major... 

Other commercial thermoplastics include acrylonitrile butadiene styrene (ABS), cellulose acetate butyrate (CAB), polycarbonate (PC), nylon (PA), and acetals. These resins are frequently used in consumer applications. 

Other commercially radiochromic films are poly(methyl methacrylate) (PMMA), cellulose triacetate (CTA),i polyamide (nylon) films, poly(vinyl butyrate) with pararosaniline and p-nitrobenzoic acid, and alanine films. The CTA films are undyed PMMA films are available undyed and dyed (red and amber). ... 

Nylon-6,6, discovered by Carothers in 1929, is by far the most important polyamide prepared by condensation polymerization. Nylon 6, prepared by the ring-opening (non-condensation) polymerization of e-caprolactam, will not be discussed in this chapter. Other commercially important polyamides prepared by condensation techniques include nylon-6,10, from hexamethylene diamine and sebacic acid, poly(/n-... 

The three other commercially important polyamides are nylon 6,10, nylon 11, and nylon 12. Nylon 6,10 is prepared from the purified 1 1 salt, hexamethy-lenediammonium sebacate, in a manner parallel to that described for nylon 6,6 (Eq. 21.13). 

Among the nylons, nylon 6,6 and nylon 6 are of the greatest commercial importance and most widely used. Other commercially useful materials are the higher analogs such as nylon 6,9 6,10 6,12 11 and 12. Nylon 6,6 and nylon 6 are widely used because they offer a good balance of properties at an economic price. Other nylons command relatively higher prices. 

Other factors complicating the direct SEC analysis of nylons in fluorinated solvents are the selection of calibration standards and the polyelectrolyte effect (7) in fluorinated solvents. Another consideration is column durability under high-temperature conditions and in fluorinated solvents. Regarding commercial nylon standards, broad molecular weight nylon standards have only become available from American Polymer Standard Corporation (Mentor, Ohio) in the 1980s. A series of nylon 6,6 standards with molecular weight ranging from 27,000 to 110,000 is now obtainable from commercial suppliers. 

The two main commercial polyamides are nylon 6,6, produced by condensation polymerization of HMD and adipic acid (see Table 7.1), and nylon 6, an AB-type polymer, which is produced from caprolactam. Other commercial polyamides include nylons 4,6, nylon 6,12 (which are AA- and BB-type polymers) and nylon 11 and nylon 12 (which are AB polymers made from linear aliphatic amino acids containing 11 and 12 carbons, respectively) [1]. Polyamides are also produced using monomers with aromatic, rather than aliphatic segments. Polyamides that contain 85% or more of the amide bonds attached to aromatic rings are called aramids. Commercial examples include poly(p-phenyleneterephthalamide) or Kevlar and poly(m-phenyleneisoterephthalamide) or Nomex [23]. 

Nylons are also widely used in the manufacture of fibres. However, there is a variety of commercial nylons available, each with slightly different structures, but all containing an amide group and methylene chains. Suppose that two textile fibres are examined by using infrared microscopy, where one is known to be nylon 6 and the other nylon 6,6. Given that nylon 6 has the structure -[-NH-(CH2)5-CO-] - and that nylon 6,6 has the structure -[-NH-(CH2)6-NH-CO-(CH2)4-CO-] -, how could the infrared spectra obtained for each of the fibres be used to identify which fibre is nylon 6 and which is nylon 6,6 ... 

A variety of commercial nylons are available, including nylon 6, nylon 11, nylon 12, nylon 6,6, nylon 6,10, and nylon 6,12. The most widely used nylons are nylon 6,6 and nylon 6. Specialty grades with improved impact resistance, improved wear, or other properties are also available. Polyamides are used most often in the form of fibers, primarily nylon 6,6 and nylon 6, although engineering applications are also of importance. 

Nylon-4 (polypyrroKdinone) n. A polymer of 2-pyrrolidinone. Early attempts to commercialize nylon-4 failed because much of the material was of low molecular weight and decomposed at a relatively low temperature, making it unusable for melt spinning. Improved catalyst systems resulted in a polymer with a molecular weight (M ) of about 400,000 and a melting point of 256°C. Today s nylon-4 has better heat stabUity than other nylons. Its moisture absorption is higher than that of nylon-6 and 6/6. It can be molded and extruded. Artificial leathers have been made from slurries of nylon-4 fibers. 

Another early example was DuPont s nylon intermediates processes developed in the late 1930s. DuPont chose to commercialize nylon-66 because of the availability of benzene from coal as a feedstock. The benzene had to be hydrogenated to cyclohexane, which was oxidized in two steps to adipic acid. Originally, adipic acid was the precursor for the other intermediate, hexamethylene diamine. Production of nylon and other polymer intermediates would be an important field in homogeneous catalyst innovation in the post-war era (71). 

Nylon is the common designation for aliphatic polyamide thermoplastic resins. They were first prepared by Wallace Hume Carothers in the 1930 s at DuPont, which story is elsewhere recorded. The word "Nylon" started out as a trademark of DuPont, but as have the names of other commercial successes it has evolved into a generic term. 

---