Aromatic copolyester

In the late 1980s, new fully aromatic polyester fibers were iatroduced for use ia composites and stmctural materials (18,19). In general, these materials are thermotropic Hquid crystal polymers that are melt-processible to give fibers with tensile properties and temperature resistance considerably higher than conventional polyester textile fibers. Vectran (Hoechst-Celanese and Kuraray) is a thermotropic Hquid crystal aromatic copolyester fiber composed of -hydroxyben2oic acid [99-96-7] and 6-hydroxy-2-naphthoic acid. Other fully aromatic polyester fiber composites have been iatroduced under various tradenames (19). 

Also in 1972 (6), Carbomdum researchers described a family of aromatic copolyesters which were recognized later to form Hquid crystalline melts. The polymers are based on a bisphenol monomer. In 1976, in a patent assigned to Carbomndum, a hydroxybenzoic acid—terephthaHc acid—bisphenol system, modified and softened with isophthaHc acid, was reported to be melt spinnable to produce fiber. 

Hie ester linkage of aliphatic and aliphatic-aromatic copolyesters can easily be cleaved by hydrolysis under alkaline, acid, or enzymatic catalysis. This feature makes polyesters very attractive for two related, but quite different, applications (i) bioresorbable, bioabsorbable, or bioerodible polymers and (ii) environmentally degradable and recyclable polymers. 

The carboxy-ester interchange melt polyesterification used for the preparation of this wholly aromatic copolyester is followed by a solid-state postpolyesterification (Scheme 2.65). (Reprinted from ref. 439. Copyright 1990 John Wiley Sons, Inc., by permission of the copyright owner.)... 

Aromatic block copolymers, 282-284 Aromatic copolyesters, 18 Aromatic coupling, catalysts for, 289 Aromatic diamines, 180... 

Aromatic copolyesters, 13 372 Aromatic diacyl peroxides, 14 283 Aromatic diisocyanates, urethanes obtained from, 25 462—463 Aromatic epoxies, 10 347-348 Aromatic ethers, 10 574 Aromatic fluorocarbon production, global, 11 871-872... 

Ecoflex F, the original Ecoflex grade, is a completely fossil-based ahphatic-aromatic copolyester produced by BASF (see Sect. 4). It is synthesized from 1,4-butanediol, adipic acid and terephthalic acid, and is a poly(butylene adipate-co-butylene terephthalate) (PBAT). 

Turning to the low temperature transition of the homopolymer of PHBA at 350 °C, it is generally accepted that the phase below this temperature is orthorhombic and converts to an approximate pseudohexagonal phase with a packing closely related to the orthorhombic phase (see Fig. 6) [27-29]. The fact that a number of the diffraction maxima retain the sharp definition at room temperature pattern combined with the streaking of the 006 line suggests both vertical and horizontal displacements of the chains [29]. As mentioned earlier, Yoon et al. has opted to describe the new phase as a smectic E whereas we prefer to interpret this new phase as a one dimensional plastic crystal where rotational freedom is permitted around the chain axis. This particular question is really a matter of semantics since both interpretations are correct. Perhaps the more important issue is which of these terminologies provides a more descriptive picture as to the nature of the molecular motions of the polymer above the 350 °C transition. As will be seen shortly in the case of the aromatic copolyesters, similar motions can be identified well below the crystal-nematic transition. 

Fig. 18. Randomizing processes in the aromatic copolyesters transesterification of PHBA/PHNA mixture during compression molding at 450°C...

M.D. Shelby, A.J. Matosky, C.M. Tanner, and M.E. Donelson, Blends of aliphatic-aromatic copolyesters with ethylene-vinyl acetate copolymers, US Patent 7 241838, assigned to Eastman Chemical Company (Kingsport, TN), July 10,2007. 

Starch-based materials represent the largest class of biodegradable polymer with 44,800 tonnes (including loose-fill foam packaging) consumed in 2005. Excluding loose-fill, starch-based materials amounted to 21,700 tonnes in 2005. Polylactic acid (PLA) is the second largest material class with 35,800 tonnes in 2005, followed by synthetic aliphatic-aromatic copolyesters with 14,000 tonnes. The embryonic PHA category amounts to around 250 tonnes. 

Adipic acid aromatic copolyesters Biodegradable polyester used in degradable plastic... 

Positron annihilation lifetime measurements of free volume in wholly aromatic copolyesters and blends . Marcromolecules. 28, 6100. 

The first thermotropic LCPs were reported in the mid-1970 s by Roviello and Sirigu (15) and Jackson and Kuhfuss (16). Since then, a large number of LCPs have been reported an excellent, though now dated, review of main-chain (i.e., the mesogen is in the polymer backbone) thermotropic LCPs was published by Ober et al. (17). In the 1980 s, several thermotropic aromatic copolyester LCPs were commercialized. 

Main Chain LC Polymers. New thermotropic copolyesters with either random or ordered mesogenic sequences have been reported with a wide range of mesophase behaviors. Recent developments in this field have included the use of naphthalene, stilbene and related structures in addition to the traditional phenylene groups to produce the required rigid main chain, and these are described in chapters by Jin, Jackson and Morris, and Skovby et al. Efforts have been undertaken to control transition temperatures and solubility through the use of either substituents or changes in the monomer sequence distribution. Successful application of these efforts have led to the commercialization of several thermotropic aromatic copolyesters (23.24). 

Thermotropic Aromatic Copolyesters Having Ordered Comonomer Sequences Syntheses and Properties... 

However, interchange reactions appear to be rather slow at temperatures below Tm(15). We(50) observed that thermal treatment of some of liquid crystalline, aromatic copolyesters at the temperatures substantially lower than Tm did not lead to any changes in the comonomer sequence even after a prolonged period of time. A copolyester especially of 4-hydroxybenzoic acid, however, can undergo a special type of sequence changes below Tm, which is called the crystallization induced reaction(51). 

A comprehensive interpretation of the microstructure of the liquid crystalline aromatic copolyesters is presented. The role of the synthetic route and of high temperature processing on the microstructure are clearly defined. As a result of this study a predictive model now exists which permits interpretation of the very subtle chemical processes which can occur at elevated temperatures leading to either randomization or ordering of the microstructure. 

ECONOMY ETAL. Synthesis and Microstructure of Aromatic Copolyesters 135... 

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