Commercially important polyamides

Polymers that contain amide linkage groups are called polyamides. Proteins, which are biological polyamides, are described in Section 13-1. Here we focus on two commercially important polyamides Nylon 66 and Kevlar. 

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. 

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). 

A commercially important polyamide based on an alicyclic diamine is Qiana (Structure IV), which was introduced by Du Pont in 1968. 

Polyesters and polyamides are two of the most studied step-growth polymers, as well as being substances of great commercial importance. We shall consider polyesters in the next section, and polyamides in Sec. 5.6. 

Of the many possible methods for preparing linear polyamides five are of commercial importance ... 

The commercial importance of aromatic polyamides has, however, grown considerably in recent years. These may be classified into three groups ... 

Many of the commercially important plastics such as polystyrene, polyamide, polyester, polycarbonate, polysulfone, polyphenylene oxide alloys, epoxy, and phenolics lack good impact... 

Pyrazolines are a class of FBAs for use on cellulose acetate and more importantly commercially on polyamide fibres. For polyamide, anionic derivatives such as (3.62) are used, applied by pad-thermosol and related methods. 

Adiponitrile. Adiponitrile is an important intermediate in polyamide manufacture. 1,6-Hexamethylenediamine formed by the hydrogenation of adiponitrile is used in the production of nylon-6,6, one of the most important polyamides in commercial production. 

Although blending with other coating resins provides a variety of ways to improve the performance of alkyds, or of the other resins, chemically combining the desired modifier into the alkyd structure eliminates compatibility problems and gives a more uniform product. Several such chemical modifications of the alkyd resins have gained commercial importance. They include vinylated alkyds, silicone alkyds, urethane alkyds, phenolic alkyds, and polyamide alkyds. 

The synthesis of aza-2-cycloheptanone (e-caprolactam) by the Beckmann rearrangement of the oxime of cyclohexanone is of commercial importance because the lactam is an intermediate in the synthesis of a type of nylon (a polyamide called nylon-6 2) ... 

The commercial importance of spin finishes can be realized from the sheer volume of synthetic fibers produced. For the year 2000, the production figures of the three major synthetic fibers, e.g., polyester, polyamide (nylon), and poly(acrylonitrile) were approximately 18, 4, and 3 million tons, respectively (51). If spin finishes are applied at 0.25-0.5% level, the annual requirement of these finishes will be in the range of 70-140 thousand tons. This has given rise to industries that supply spin-finish components and completely formulated spin finishes for specific applications (52). An experimental nonproprietory spin finish formulation supplied to TRI/Princeton by Henkel Corp. follows ... 

A number of polymers with structures related to those of polyamides have been developed, some of which have achieved commercial importance, such as... 

The commercial importance of hydroxylamine is coupled to its use (up to 97%) in the manufacture of caprolactam, a precursor in the manufacture of polyamide 6 (however, not all caprolactam is manufactured using it) ... 

In addition to step and chain polymerizations, another mode of polymerization is of importance. This is the ring-opening polymerization of cyclic monomers such as cyclic ethers, esters (lactones), amides (lactams), and siloxanes. Examples of commercially important types are given in Table 10.1. Of those listed, only the polyalkenes are composed solely of carbon chains. Those that have enjoyed the longest history of commercial exploitation are polyethers prepared from three-membered ring cyclic ethers (epoxides), polyamides from cyclic amides (lactams), and polysiloxanes from cyclic siloxanes. 

Phenol is a material of major commercial importance. One of its earliest uses was as a disinfectant (carbolic acid). Earlier in the twentieth century, it became important as a feedstock for resins such as Bakelite , and in the latter part of the century it also became very important as a precursor for caprolactone and caprolactam and hence polyester and polyamide manufacture. The two major methods for phenol production nowadays are by the catalytic oxidation of benzoic acid and catalytic decomposition of cumene hydroperoxide (Scheme 4.55). 

A summary of the properties of some of these materials is presented in Tables 8 and 9. Diffusion coefficients and NaCl partition coefficients are presented in Table 8 for cellulose triacetate and for Nomex polyamide. In most cases, however, intrinsic transport properties are not known, and what is reported in the literature is the water flux and salt rejection of RO membranes under given test conditions. Under comparable test conditions (0.5-1% NaCl, 27—68 atm) the water fluxes of these newer membranes are comparable (0.4-0.8 m3/m2-day). Salt rejection data are presented in Table 9. To put these data in perspective, the salt rejection of cellulose 2.5-acetate membranes is typically <99%. However, for various reasons none of these new membranes has yet become commercially important. 

Other polyamides of commercial importance are nylons that are higher analogs of the more common types nylons 11 12 6,10 and 6,12. The numerals in the trivial names refer to the number of carbon atoms in the monomer(s). In designating A-A/B-B nylons, the first number refers to the number of carbon atoms in the diamine while the second number refers to the total number of carbon atoms in the acid. For example, nylon 6,10 is poly(hexamethylene sebacamide) (Equation 2.35). 

Interfacial and solution polycondensations are commercially important. For example, an unstirred interfacial poly condensation reaction is utilized in the production of polyamide fibers. Another important application of interfacial polycondensation is the enhancement of shrink resistance of wool. The wool is immersed first in a solution containing one of the reactants and subsequently in another solution containing the other reactant. The polymer resulting from the interfacial reaction coats the wool and improves its surface properties. 

The additional chain orientation in the direction of the fiber long axis, obtained from the nematic self-ordering in the system, leads to a dramatic enhancement of the mechanical properties of the polymer. A number of aromatic polyamides have thus achieved commercial importance because of the very high tensile strengths and moduli of the fibers that can be spun from the nematic solutions. These have consequently become attractive alternatives to metal or carbon fiber for use in composites as reinforcing material. The most significant of these aramid fibers are ... 

---