Lateral polyesters

Pol30irethane chemistry began with the utilization of polyester polyols, principally prepared from diacids such as adipic acid and various diols. Later, polyester polyols were replaced by polyether polyols due to improvements in mechanical properties and moisture resistance. Polyether polyols now constitute the greater part of the volume in pol3airethane polymers [1]. 

The polyester-type thermoset polyurethanes were commercialized in 1942, and the linear thermoplastic ones (TPU) ten years later. Polyester-type TPU, Texin resins for extrusion and injection molding, were introduced in 1961, whereas polyether-type, Roylar , in 1971. Owing to great diversity of the ingredients, the TPU performance can be readily modihed. Por this reason, as well as because of the cost, TPU s are seldom blended. Their use can be divided into three groups (i) blends with POM, (ii) blends in which TPU is used as a com-patibilizer and impact modifier, and (iii) others. 

By 1941, as the first synthetic polymers were being converted into fibers (nylon and later polyester), regenerated cellulosic fiber production had risen to 1,250,000 ton. It continued to expand into the 1970s recording its highest ever annual output at 3,856,000 ton in 1973. Since then a steady decline has occurred as more and more end uses switch to the cheaper S5mthetic fibers based on oil valued at little more than the costs of extraction. 

In 1941-42, the world witnessed the infancy of polyethylene terephthal-ate, better known as the polyester. A decade later for the first time polyester/ cotton blends were introduced. In those days Terylene and Dacron (commercial names for polyester fibers) were miracle fibers but were still overshadowed by nylon. Not many would have predicted that decades later, polyester would have become the world s inexpensive, general purpose fiber as well as becoming a premium fiber for special functions in engineering textiles, fashion, and many other technical end uses. From the time nylon and polyester were first used, there have been amazing technological advances which have made them so cheap to manufacture and widely available. 

Mason, RW. Decades later, polyester forges new image. Textile World. 1999, 149(l) 57-60. 

According to Section 7.4, the activation of the polymerization of lactams by e-caprolactone 36 (CLO) is efficient, but at higher concentration of the later polyester-amide copolymers are produced. In fact, this is a rare example of the copolymerization of cycles that have different mechanisms of the formation of the homopolymers and give rise to a copolymer. The initiation step is the acylation of lactone by the lactam anion [38, 77]. 

Mutagenic and later carciaogenic properties were found for tris(2,3-dibromopropyl) phosphate (148—150), a flame retardant used on polyester fabric ia the 1970s. This product is no longer on the market. The chemically somewhat-related tris(dichloroisopropyl) phosphate has been intensively studied and found not to display mutagenic activity (148,149,151). Tris(2-chloroethyl) phosphate appears to be a weak tumor-iaducer ia a susceptible rodent strain (150). 

The second largest use at 21% is for unsaturated polyester resins, which are the products of polycondensation reactions between molar equivalents of certain dicarboxyhc acids or thek anhydrides and glycols. One component, usually the diacid or anhydride, must be unsaturated. A vinyl monomer, usually styrene, is a diluent which later serves to fully cross-link the unsaturated portion of the polycondensate when a catalyst, usually a peroxide, is added. The diacids or anhydrides are usually phthahc anhydride, isophthahc acid, and maleic anhydride. Maleic anhydride provides the unsaturated bonds. The exact composition is adjusted to obtain the requked performance. Resins based on phthahc anhydride are used in boat hulls, tubs and spas, constmction, and synthetic marble surfaces. In most cases, the resins contain mineral or glass fibers that provide the requked stmctural strength. The market for the resins tends to be cychcal because products made from them sell far better in good economic times (see Polyesters,unsaturated). 

Qiana, introduced by Du Pont in 1968 but later withdrawn from the market, was made from bis(4-aminocyclohexyl)methane and dodecanedioic acid. This diamine exists in several cis—trans and trans—trans isomeric forms that influence fiber properties such as shrinkage. The product offered silk-like hand and luster, dimensional stabiUty, and wrinkle resistance similar to polyester. The yam melted at 280°C, had a high wet glass-transition temperature of - 85° C and a density of 1.03 g/cm, the last was lower than that of nylon-6 and nylon-6,6. Qiana requited a carrier for effective dyeing (see Dye carriers). 

Some time earlier, Eastman-Kodak has been working on a novel polyester as an entry into the important polyester fiber market and had devised a new ahcychc diol, 1,4-cydohexanedimethanol [105-08-5] effectively made by exhaustive hydrogenation of dimethyl terephthalate. Reaction of the new diol with dimethyl terephthalate gave a crystalline polyester with a higher melting point than PET and it was introduced in the United States in 1954 as a new polyester fiber under the trade name Kodel (5). Much later the same polyester, now called PCT, and a cyclohexanedimethanol—terephthalate/isophthalate copolymer were introduced as mol ding resins and thermoforming materials (6). More recentiy stiU, copolymers of PET with CHDM units have been introduced for blow molded bottie resins (7). 

Some commercial durable antistatic finishes have been Hsted in Table 3 (98). Early patents suggest that amino resins (qv) can impart both antisHp and antistatic properties to nylon, acryUc, and polyester fabrics. CycHc polyurethanes, water-soluble amine salts cross-linked with styrene, and water-soluble amine salts of sulfonated polystyrene have been claimed to confer durable antistatic protection. Later patents included dibydroxyethyl sulfone [2580-77-0] hydroxyalkylated cellulose or starch, poly(vinyl alcohol) [9002-86-2] cross-linked with dimethylolethylene urea, chlorotria2ine derivatives, and epoxy-based products. Other patents claim the use of various acryUc polymers and copolymers. Essentially, durable antistats are polyelectrolytes, and the majority of usehil products involve variations of cross-linked polyamines containing polyethoxy segments (92,99—101). 

The reduction of pH within the film unit is effected by a polymeric acid layer, as in the Polacolor process. The onset of neutralization is controlled by a contiguous timing layer. In the original SX-70 film unit these layers were on the inner surface of the transparent polyester sheet (Fig. 12) in Time-Zero SX-70 and later Polaroid integral films these layers are on the inner surface of the opaque negative support, as shown in Figure 13. 

Other polyamides produced experimentally include polymers with active lateral groups (hydroxy, keto groups etc.), polymers with heteroatoms (sulphur and oxygen) in the polyamide-forming intermediates, polymers with tertiary amino groups in the main chain and polymers with unsaturation in the main chain. There does not, however, appear to have been any serious attempt to develop unsaturated polyamide analogues to the polyester laminating resins. 

Cross-linkable rubbery polyesters have been produced but are now no longer produced. Rubbery polyester-amides were introduced by ICI under the trade name Vulcaprene as a leathercloth material but later were used primarily as leather adhesives and as flexible coatings for rubber goods. A typical polymer may be made by condensing ethylene glycol, adipic acid and ethanolamine to a wax with a molecular weight of about 5000. 

As will be discussed later, flexible polyester foams are not altogether satisfactory for upholstery applications and in the 1950s the attention of American chemists turned to the use of polyethers. These materials could be obtained more cheaply than the polyesters but the products were less reactive and with the catalyst... 

Thermoplastic polyester elastomers such as the Du Pont product Hytrel were developed later than the polyurethane materials, being first introduced in 1972. They have similar characteristics to the polyurethanes but there is an upward shift in the hardness range (i.e. the softest grades are not so soft, but the hardest grades are harder than the corresponding extreme grades in the polyurethanes). 

Aromatic polyesters constitute an important class of main-chain liquid-crystalline polymers, but present the inconvenience of their reduced solubility and very high transition temperatures (sometimes not detected before the degradation of the sample). Their processability can be improved in several ways [2,3], e.g., reduction of the rigidity of the mesogen, lengthening of the spacer, or introduction of lateral substituents. 

For this case, which is the fairly common situation of a biaxially oriented film, it is therefore necessary to obtain a total of thirteen second and fourth order coefficients. Later, results for polyester films will be discussed, where seven of these thirteen coefficients have been determined experimentally. 

The disruption of chain regularity by the introduction of lateral substituents or kinks on repeating units is a supplementary means to decrease the melting temperature of aromatic polyesters.72 This is illustrated in Table 2.9, where the melting temperatures of unsubstituted and methyl-substituted aromatic-aliphatic and aliphatic acids are reported. Regularity disruptions often cause significant... 

Trinitrochlorobenzene (piciyl chloride) in pyridine-A -mcthylpyrrolidi-none (NMP) solutions were later used for the preparation of polyesters from dicarboxylic acids and diphenols or aliphatic diols,309 but better results have been obtained with sulfonyl chlorides and phosphorus compounds. 

Certain commercially important crosslinking reactions are carried out with unsaturated polymers. For example, as will be described later in this chapter, polyesters can be made using bifunctional acids which contain a double bond. The resulting polymers have such double bonds at regular intervals along the backbone. These sites of unsaturation are then crosslinked by reaction with styrene monomer in a free-radical chain (addition) process to give a material consisting of polymer backbones and poly(styrene) copolymer crosslinks. 

That fall, Carothers assistant Edgar W. Spanagel discovered polyethylene terephthalate, the polyester that Du Pont later manufactured under license as Dacron fiber and Mylar film. Carothers had made most of the polyesters, but he and others in his group assumed that Spanagel s polyester, like their earlier ones, melted at too low a temperature to be practical. As a result, Carothers did not have this one tested for spinnability. British scientists later used it to make Terylene. When Du Pont executives had to buy a license from the British to make Spanagel s fiber, their faces were bright red with embarrassment. 

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