Commercial polyesters

Aromatic polyesters, commercially important molding resin materials, show a low degree of flammability and produce high percentages of char on exposure to a flame or on heating to pyrolysis conditions (9). 

Table II gives the crystallinity values for various kinds of polyamide yarns. In one case, the occurence of a relatively amorphous skin can be detected. There is also an example of the effect of an azimutal correction. Absolute crystallinity values do not agree well with X-ray based crystallinity values. Nevertheless, there is a general qualitative agreement in the difference between polyamide and polyester yarns (it is well known that crystallinity is generally higher for polyamide than for polyester commercial filaments).

In 1972, Cottis and coworkers at Carborundum patented wholly aromatic polyesters based on p-hydroxybenzoic acid (HBA), A,A -dihydrox-ybiphenyl (DHB), and terephthalic acid (TPA), one of which was later commercialized as EKKCEL 1-2000 [1]. In 1974, Kuhfuss and coworkers at Eastman Kodak reported a new polyester based on HBA and polyfethylene terephthalate) (PET), which was later marketed under the code of X-7G. X-7G is the first thermotropic liquid crystalline polymer to be fabricated by injection molding or melt spinning [2]. However, then Eastman Kodak withdrew its plan of marketing of X-7G and changed the target with a wholly aromatic polyester commercialized as TITAN (THERMX ) in 1996. As described later, it was acquired by DuPont in 2003. 

Unsaturated Polyester. Commercially available unsaturated polyester (39) has found a large number of applications in many areas, eg, auto industries and coating materials. A water-soluble imsaturated polymer with the molecular weights of 11,000-13,000 g/mol was cross-linked with the RAMEB-complexed styrene at 25°C using 4 mol% of the water-soluble redox initiator. A comparative experiment with uncomplexed comonomer stsu ene showed that higher yield and a higher content of polyst5Tene in the copolymer was achieved in the presence of RAMEB (40). 

This is a more reactive form of unsaturation than vinyl, and is used extensively in free radical curing formulations, where the extra reactivity is of benefit, e.g., acrylics, some polyesters. Commercial products usually contain y-methacryloxy propyl groups, and hence the double bond is further away from the silicon than is the case with the vinyl silane. As mentioned previously, Jang and co-workers have studied the effect of the length of the spacer group [69]. 

Aliphatic Polyester Commercial Name as Biodegradable Plastic Degradability"... 

The purpose of this section is to compare the properties of PHA polymers with those of polyesters commercially available. In fact, the thermal properties of materials are important for processing and also during the use of the products derived from these materials as well as the physical and mechanical properties of these polymers in order to design novel eco-friendly films. The properties of some biodegradable polymers are gathered in Table 1 and data available for two most common polymers (LDPE, PP) are added for comparison. 

The first synthetic biodegradable aliphatic polyester commercially available was poly(e-caprolactone) (PCL), produced under the trade name Tone by the Union Carbide Corporation in the USA. The product was the subject of a number of biodegradability studies [7] and was originally employed for medical sutures, and then as a component in biodegradable polyester/starch blends (e.g., Mater-Bi Z-grade, Novamont, Novara, Italy) [13]. 

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. 

More recentiy, melt-spun biconstituent sheath—core elastic fibers have been commercialized. They normally consist of a hard fiber sheath (polyamide or polyester) along with a segmented polyurethane core polymer (11,12). Kanebo Ltd. in Japan currentiy produces a biconstituent fiber for hosiery end uses called Sideria. 

Commercially, elastomeric fibers are almost always used in combination with hard fibers such as nylon, polyester, or cotton. Use levels vary from a low of about 3% in some filling stretch cotton fabrics to a high of about 40% in some warp-knit tricot fabrics. Raschel fabrics used in foundation garments normally contain 10—20% spandex fiber. 

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). 

Poly(ethylene terephthalate), the predominant commercial polyester, has been sold under trademark names including Dacron (Du Pont), Terylene (ICI), Eortrel (Wellman), Trevira (Hoechst-Celanese), and others (17). Other commercially produced homopolyester textile fiber compositions iaclude p oly (1,4-cyc1 oh exa n e- dim ethyl en e terephthalate) [24936-69-4] (Kodel II, Eastman), poly(butylene terephthalate) [26062-94-2] (PBT) (Trevira, Hoechst-Celanese), and poly(ethylene 4-oxyben2oate) [25248-22-0] (A-Tell, Unitika). Other polyester homopolymer fibers available for specialty uses iaclude polyglycoHde [26124-68-5] polypivalolactone [24937-51-7] and polylactide [26100-51-6],... 

Bromine as a Reactive Flame Retardant. Bromine and chlorine are the starting materials for all of the commercial compounds described. Bromine is also used in a somewhat different way to impart flame retardancy. That is, it is used to brominate the resin in interest directly. This is practiced commercially in the case of unsaturated polyesters (59). 

Chlorendic Acid. Chlorendic acid [115-28-6] and its anhydride [115-27-5] are widely used flame retardants. Chlorendic acid is synthesized by a Diels-Alder reaction of maleic anhydride and hexachlorocyclopentadiene (see CyclopentadlENE and dicyclopentadiente) in toluene followed by hydrolysis of the anhydride using aqueous base (60). The anhydride can be isolated directly from the reaction mixture or can be prepared in a very pure form by dehydration of the acid. The principal use of chlorendic anhydride and chlorendic acid has been in the manufacture of unsaturated polyester resins. Because the esterification rate of chlorendic anhydride is similar to that of phthalic anhydride, it can be used in place of phthalic anhydride in commercial polyester... 

Several commercial polyester fabrics are flame retarded using low levels of phosphoms additives that cause them to melt and drip more readily than fabrics without the flame retardant. This mechanism can be completely defeated by the presence of nonthermoplastic component such as infusible fibers, pigments, or by siUcone oils which can form pyrolysis products capable of impeding melt flow (27,28). 

TrialkylPhosphates. Triethyl phosphate [78-40-0] C H O P, is a colorless Hquid boiling at 209—218°C containing 17 wt % phosphoms. It may be manufactured from diethyl ether and phosphoms pentoxide via a metaphosphate intermediate (63,64). Triethyl phosphate has been used commercially as an additive for polyester laminates and in ceHulosics. In polyester resins, it functions as a viscosity depressant as weH as a flame retardant. The viscosity depressant effect of triethyl phosphate in polyester resins permits high loadings of alumina trihydrate, a fire-retardant smoke-suppressant filler (65,66). 

Polyester Fibers Containing Phosphorus. Numerous patents describe poly(ethylene terephthalate) (PET) flame-retarded with phosphoms-containing diftmctional reactants. At least two of these appear to be commercial. 

The THPOH—NH process was used extensively for children s sleepwear in the early 1970s. However, the advent of the Tris problem on polyester led to a sharp decline in commercial production of chemically finished children s flame-resistant cotton sleepwear. 

THPC—Amide—PoIy(vinyI bromide) Finish. A flame retardant based on THPC—amide plus poly(vinyl bromide) [25951-54-6] (143) has been reported suitable for use on 35/65, and perhaps on 50/50, polyester—cotton blends. It is appUed by the pad-dry-cure process, with curing at 150°C for about 3 min. A typical formulation contains 20% THPC, 3% disodium hydrogen phosphate, 6% urea, 3% trimethylolglycouril [496-46-8] and 12% poly(vinyl bromide) soUds. Approximately 20% add-on is required to impart flame retardancy to a 168 g/m 35/65 polyester—cotton fabric. Treated fabrics passed the FF 3-71 test. However, as far as can be determined, poly(vinyl bromide) is no longer commercially available. 

Syntactic Cellular Polymers. Syntactic cellular polymer is produced by dispersing rigid, foamed, microscopic particles in a fluid polymer and then stabilizing the system. The particles are generally spheres or microhalloons of phenoHc resin, urea—formaldehyde resin, glass, or siUca, ranging 30—120 lm dia. Commercial microhalloons have densities of approximately 144 kg/m (9 lbs/fT). The fluid polymers used are the usual coating resins, eg, epoxy resin, polyesters, and urea—formaldehyde resin. 

Foams prepared from phenol—formaldehyde and urea—formaldehyde resins are the only commercial foams that are significantly affected by water (22). Polyurethane foams exhibit a deterioration of properties when subjected to a combination of light, moisture, and heat aging polyester-based foam shows much less hydrolytic stabUity than polyether-based foam (50,199). 

The largest commercial use of ethylene glycol is its reaction with dicarboxyUc acids to form linear polyesters. Poly(ethylene terephthalate)... 

The primary and secondary alcohol functionahties have different reactivities, as exemplified by the slower reaction rate for secondary hydroxyls in the formation of esters from acids and alcohols (8). 1,2-Propylene glycol undergoes most of the typical alcohol reactions, such as reaction with a free acid, acyl hahde, or acid anhydride to form an ester reaction with alkaU metal hydroxide to form metal salts and reaction with aldehydes or ketones to form acetals and ketals (9,10). The most important commercial appHcation of propylene glycol is in the manufacture of polyesters by reaction with a dibasic or polybasic acid. 

Cydohexanedimethanol, 1,4- dim ethyl o1 cycl oh exa n e, or 1,4-bis (hydroxymethyl) cyclohexane (8), is a white, waxy soHd. The commercial product consists of a mixture of cis and trans isomers (6). This diol is used in the manufacture of polyester fibers (qv) (64), high performance coatings, and unsaturated polyester molding and laminating resins (5). 

Much more important is the hydrogenation product of butynediol, 1,4-butanediol [110-63-4]. The intermediate 2-butene-l,4-diol is also commercially available but has found few uses. 1,4-Butanediol, however, is used widely in polyurethanes and is of increasing interest for the preparation of thermoplastic polyesters, especially the terephthalate. Butanediol is also used as the starting material for a further series of chemicals including tetrahydrofuran, y-butyrolactone, 2-pyrrohdinone, A/-methylpyrrohdinone, and A/-vinylpyrrohdinone (see Acetylene-DERIVED chemicals). The 1,4-butanediol market essentially represents the only growing demand for acetylene as a feedstock. This demand is reported (34) as growing from 54,000 metric tons of acetylene in 1989 to a projected level of 88,000 metric tons in 1994. 

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