Copolyester advantages

Many evaluations have led to the commercial utilization of PEN, its copolyesters and blends in some commercial applications. The cost effectiveness is especially apparent in retumable-refillable applications, which take advantage of PEN s chemical resistance in commercial washing operations, so ensuring an increased number of re-fill trips [26], Other applications benefit from PEN s increased gaseous barrier, UV absorption, thinner and lower weight potential. Considerable effort is underway to enable utilization of PEN, its copolyesters and blends for beer, higher hot-fill and heat-pasteurizable containers [27],... 

By the mid 1970s, Tennessee Eastman also announced development of a copolyester consisting of 60/40 PHBA/polyethylene terephthalate (PET) by direction reaction of acetoxybenozic acid with PET in the melt [2], This system had the advantage of lower costs, but its use temperature was limited to 90 °C which is just above its Tg. In the early 1980s, researchers at Celanese reported... 

An equally important observation for the above copolyester LCPs is that the ordered arrangement of polymeric mesophases in the melt is retained upon cooling, which is manifested in greatly improved mechanical properties (see Figure 5.5b). The liquid crystalline behavior is therefore advantageous from the standpoint of both processing and properties. Thermotropic liquid crystal copolyesters of structures similar to (I) are now available commercially. 

Zachmann et al. [124] have taken advantage of these suggestions, describing not a polymer blend but binary and ternary copolyesters prepared from poly(ethylene-terephthalate), poly (ethylene-naphthalene-2,6-dicarbonoxylate), and poly(p-hydroxy-benzoate). This example is very instructive and clearly shows the practical value of phase diagrams in general and especially of the procedure suggested above. 

Thermoplastic elastomers (TPEs) continue to grow in commercial importance. These materials combine the functional properties of comparable thermoset elastomers with the fabrication advantages of thermoplastics. As a class, TPEs comprise several types of materials such as elastomeric alloys (EAs), styrenic block copolymers, copolyesters, and thermoplastic polyurethanes. 

Instead of the conventional binder pol5miers described above, biodegradable polymers may be used advantageously, such as aliphatic-aromatic copolyesters. A preferred aliphatic dicarboxylic acid is adipic acid and as aromatic dicarboxylic acid terephthalic acid can be used. As a glycol component 1,4-butanediol has been suggested. The natural cellulose fibers are selected from hemp, sisal, flax, kenaf, cotton, jute, or coconut (32). Commercial natural cellulose containing fibers are summarized in Table 5.10. 

Considerable literature exists on the structural organisation of thermotropic liquid crystalline aromatic copolyesters. Majority of these copolyesters are synthesised via the copolymerisation route, which helps in tailoring the characteristic properties to the predecided values. Another major advantage of copolymerisation is that it helps in conferring specific chemical properties to the major component present in the system. 

B) Polymer-cement concrete is a modified concrete in which a part of the cement binder is replaced by organic polymer. It is produced by incorporating a monomer, prepolymer, or dispersed polymer latex into a cement-concrete mixture. The process technology used is similar to that of conventional concrete and has the advantage that it can be cast in place for field applications. Most of the polymer-cement-concrete composites are based on different kinds of lattices obtained especially by emulsion polymerization. The lattices are aqueous emulsions containing polymer particles such as SBR, NBR, PVAc, copolyesters of AA-MAA, and PAA-PMAA-SBR. The compatibility of SBR, PVAc, and acrylic lattices with Portland cement produces particular characteristics that led to wide use of this component as polymer-concrete composites. 

Thermotropic aromatic copolyesters have a major advantage over the lyotropes as the thermo-... 

Fatty alcohol ethoxylates were spotted and characterized by Spriestersbach, Rode, and Pasch [128]. Other applications of semi-on-line LC—MALDl coupling via a spraying interface for synthetic polymers involve copolyesters [129], silsesquioxanes [130], and hydroxyl-terminated polydimethylsiloxane [131,132]. Reference [103] summarizes different applications, comparing their advantages and drawbacks. 

Furthermore, novel polyfpropylene terephthalate-co-adipate) random copolymers showed that they can be degraded via hydrolysis, especially in the presence of enzymes (Rhizopus delemar and Pseudomonas cepacia lipases), even for a terephthalate content as high as 66 mol% [38]. In contrast to hydrolysis rates, mechanical properties increased upon increasing the terephthalate content. The main advantage of aliphatic-aromatic copolyesters over pure terephthalates is their biodegradability. 

DuPont has patented aliphatic/aromatic copolyesters that contain sulfo groups [56-59]. Polyesters that are copolymerised with 5-sulfoisophthalic acid hydrolyse readily. The polyesters are reported to be biodegradable and can be processed at higher temperatures than other biodegradable polymers. These polyesters also offer the cost advantages mentioned earlier for aliphatic/aromatic copolyesters. 

Thermotropic aromatic copolyesters have a major advantage over the lyotropes, as the former can be melt processed. Temperature affects the orientation and the mechanical properties, and the copolyesters have been shown to be biphasic by SEM [694-696], optical, and TEM [697-699] techniques. The biphasic structure of X7G has been reported [699] for extruded fibers by optical and EM imaging and microdiffraction. Transmission electron microscopy micrographs of ultrathin longitudinal sections reveal a dense dispersed phase elongated along the fiber axis (Fig. 5.147). Microdiffraction from regions 20-100 nm across show the... 

Whereas, Kricheldorf et al. [7] synthesized a first hb copolyesters to mimic the architecture of amylopectin or glycogen, the same authors and other research groups focused later their studies ob homopolycondensations of 3,5-bistrimeth-ylsiloxy benzoyl chloride [5, 8-10]. In this connection Hawker and Frechet [7] defined for the first time, the DB as an important characteristic for the description of hb polymers (see Chap. 10). Furthermore, Mws up to 80 kDa were determined by light scattering. This silyl method has two advantages. The siloxy end groups allow for an almost quantitative in situ modification by acylation with acyl... 

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