Polymers Polyamides and Polyesters

II fibers are polymers of one kind or another. Cotton, for example, is cellulose, and cellulose is a naturally occurring polymer of glucose. 

Silk and wool are naturally occurring polymers of amino acids. An early goal of inventors and entrepreneurs was to produce fibers from other naturally occurring polymers. Their earliest efforts consisted of chemically modifying the short cellulose fibers obtained from wood so that they could be processed into longer fibers more like cotton and silk. These efforts were successful, and the resulting fibers of modified cellulose, known generically as rayon, have been produced by a variety of techniques since the late nineteenth century. 

A second approach involved direct chemical synthesis of polymers by connecting appropriately 

The leader of Du Font s effort was Wallace H. Carothers, who reasoned that he could reproduce the properties of silk by constructing a polymer chain held together, as is silk, by amide bonds. The necessary amide bonds were formed by heating a dicarboxylic acid with a diamine. Hexanedioic acid (adipic acid) and 1,6-hexanediamine (hexamethylenediamine) react to give a salt that, when heated, gives a polyamide called nyion 66. The amide bonds form by a condensation reaction, and nylon 66 is an example of a condensation polymer. 

The first 6 in nylon 66 stands for the number of carbons in the diamine, the second for the number of carbons in the dicarboxylic acid. Nylon 66 was an immediate success and fostered the development of a large number of related polyamides, many of which have also found their niche in the marketplace. 

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ETHYLENE We discussed ethylene production in an earlier boxed essay (Section 5 1) where it was pointed out that the output of the U S petrochemi cal industry exceeds 5 x 10 ° Ib/year Approximately 90% of this material is used for the preparation of four compounds (polyethylene ethylene oxide vinyl chloride and styrene) with polymerization to poly ethylene accounting for half the total Both vinyl chloride and styrene are polymerized to give poly(vinyl chloride) and polystyrene respectively (see Table 6 5) Ethylene oxide is a starting material for the preparation of ethylene glycol for use as an an tifreeze in automobile radiators and in the produc tion of polyester fibers (see the boxed essay Condensation Polymers Polyamides and Polyesters in Chapter 20)... 

In another development, the use of diketenes as polymer intermediates that are similar in reactivity to the aromatic diisocyanates has been described. A particularly interesting diketene is anthracene-9,10-diketene, shown in Equation 4. Polymers, polyamides and polyesters, especially those from polyetherglycols and polyesterglycols, have been prepared. These diketenes, as reactive polymer intermediates, are also of potential interest for chain extension reactions on hydroxyl-terminated polyesters. 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

Substituted amides (not of the alkanolamide variety) are sold to diverse low volume markets. They have some utility ki polymers such as polyethylene, ethylene-vinyl acetate copolymers, acryUc polymers, PVC, polyamides, and polyesters. They have been found effective as pharmaceutical processkig aids, defoamers (qv), antimicrobials, pesticides, kisect repellents, dispersion stabilizers, and corrosion inhibitors. 

Over 250,000 metric tons of microcrystaUine cellulose have been sold siace its commercialisation ia 1962 and demand continues to iacrease. Its utihty has led to development of other coUoidal polymer microcrystals (see Colloids). For example, polyamides and polyesters from recycled materials can be biodegraded to give microcrystals having a size of 30 nm (37). 

Phenothiophosphine ring-containing polyamides and polyesters were also prepared by the polycondensation of 2,8-bischloroformyl-lO-phenylphenothiophos-phine 5,5, 10-trioxide with aromatic diamines such as 4,4 -diaminodiphenyl ether and 4,4 -diaminodiphenyl-methane, and bisphenols such as 4,4 -dihydroxybiphe-nyl and 4,4 -dihydroxydiphenylmethane, respectively [159]. These polymers are soluble in polar aprotic solvents and also exhibit good heat and fire resistance. Phosphorus containing high performance polymers are shown in Table 6. 

The alkene and diene polymers discussed in Sections 7.10 and 14.6 are called chain-growth polymers because they are produced by chain reactions. An initiator adds to a C=C bond to give a reactive intermediate, which adds to a second alkene molecule to produce a new1 intermediate, which adds to a third molecule, and so on. By contrast, polyamides and polyesters are called step-growth polymers because each bond in the polymer is formed independently of the others. A large number of different step-growth polymers have been made some of the more important ones are shown in Table 21.2. 

Step-growth polymers, such as polyamides and polyesters, are prepared by reactions between difunctional molecules. Polyamides (nylons) are formed by reaction between a diacid and a diamine polyesters are formed from a diacid and a diol. 

Polyamides and Polyesters Step-Growth Polymers 818 21.10 Spectroscopy of Carboxylic Acid Derivatives 822... 

In 1929 Carothers proposed a generally useful differentiation between two broad classes of polymers condensation polymers in which the molecular formula of the structural unit (or units) lacks certain atoms present in the monomer from which it is formed, or to which it may be degraded by chemical means, and addition polymers, in which the molecular formula of the structural unit (or units) is identical with that of the monomer from which the polymer is derived. Condensation polymers may be formed from monomers bearing two or more reactive groups of such a character that they may condense intermolecu-larly with the elimination of a by-product, often water. The polyamides and polyesters referred to above afford prime examples of condensation polymers. The formation of a polyester from a suitable hydroxy acid takes place as follows ... 

One previous synthesis of ferrocene-containing condensation polymers via interfacial methods at room temperature has been reported by Knobloch and Rauscher, who formed low molecular weight polyamides and polyesters by reacting l,l -bis(chloro-formyl)ferrocene with various diamines and diols. Further, Carraher and co-workers have utilized interfacial techniques in the formation of other types of organometallic polymers. 

Thus the Endgroup analysis method is quite useful for the determination of the Molecular weight of the polymers that possesses endgroups which can be determined precisely by some analytical reaction. In addition to Polyamides and polyesters, where the Endgroup analysis method is commonly used, the method can also be used for polysaccharides. 

Condensation polymers synthesized from single reactants are named in a similar manner. Examples are the polyamides and polyesters produced from amino acids and hydroxy acids, respectively. Thus, the polymer from 6-aminocaproic acid is named poly(6-aminocaproic acid)... 

Nature has long used reactions such as these to produce interesting solids such as cotton (seed pod), hemp (grass), and silk (cocoons for worms while they develop into moths) as fibers that we can strand into rope or weave into cloth. Chemists discovered in the early twentieth century that cellulose could be hydrolyzed with acetic acid to form cellulose acetate and then repolymerized into Rayon, which has properties similar to cotton. They then searched for manmade monomers with which to tailor properties as replacements for rope and sdk. In the 1930s chemists at DuPont and at ICl found that polyamides and polyesters had properties that could replace each of these. [Linear polyolefins do not seem to form in nature as do condensation polymers. This is probably because the organometaUic catalysts are extremely sensitive to traces of H2O, CO, and other contaminants. This is an example where we can create materials in the laboratory that are not found in nature.]... 

Fibres are, as a result of the spinning process, molecularly oriented, and they have, therefore, a 2 to 3 times higher stiffness than the non-oriented polymer (e.g. polyamide and polyester textile fibres). With the highest attainable orientation, such as in aromatic polyamides (Twaron and Kevlar), and in the PE-fibre (Dyneema) the stiffness can be a hundred times higher than the one in the unoriented condition ... 

The polymers can be categorised as formaldehyde containing and formaldehyde free and as thermoset or thermoplastic resins. Typical formaldehyde containing resins are melamine formaldehyde sulfonamide resins, where the sulfonamide is ortho and para toluenesulfonamide. The sulfonamide, which is a solvent for the dye, undergoes a condensation polymerisation with formaldehyde and melamine, the latter acting as a cross-linking agent. Non-formaldehyde, thermoplastic resins are usually polyamides and polyesters. 

Polar crystalline polymers (e.g., polyamides and polyesters) m-Cresol (hot) or hexafluoroisopropanol (cold) PL gel Polymer Labs... 

To understand these reactions, the so-called Bolland and Gee reaction scheme17-18 and its subsequent developments has been applied to explain the chain reaction characteristics of both thermal and photooxidation of polyolefins. The scheme (Scheme 2.1) has been found to be a useful model for many other polymers comprising significant aliphatic character, such as aliphatic polyamides and polyesters and certain polyvinyls including poly(vinyl chloride) (PVC). 

In the case of polyamides and polyesters the most important photolytic reactions are the Norrish I and II reactions (see Scheme 1). The Norrish I reaction leads to chain cleavage and radicals that might initiate oxidation, the Norrish II reaction only leads to chain cleavage. The main question for these polymers is What is the relative importance of photolysis and photo-oxidation ... 

Although the initial calibration is actually in terms of the relation between [rjl and Mw or M , as described, Eq. (3-44) can only be used to estimate My, for unknown polymers. It cannot be employed to estimate M , (or as the case may be) for such samples unle.ss the unknown is also a fraction with a molecular weight distribution very similar to those of the calibration samples. An important class of polymers which constitutes an exception to this restriction consists of linear polyamides and polyesters polymerized under equilibrium conditions (Chapter 5). In these cases the molecular weight distributions are always random (Section 5.4.3) and the relation... 

Aromatic polyamides and polyesters are examples of stiff chain polymers. Poly(p-phenylene terephthalamide) (Kevlar , 1-23) can be made by reaction (4-50) in a mixture of hexamethylphosphoramide and /V-methylpyrrolidone ... 

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