Polyester Elastomers TPE

Table 11.8. Effect of electron irradiation of Hytrel polyester elastomers, TPE ...

Du Font s thermoplastic polyester elastomer (TPE) Hytrel has been used in an underwater fiber optic cable produced by Shiplex Wire and Cable Corporation. The elastomer is used to position the fiber optics and is chosen because of its modulus properties that help prevent microbends in the fiber optics. The thermoplastic polyester elastomer is extruded over a central steel wire that imparts strength to the cable. Six fiber optic strands with a diameter of 5 mils each are then positioned and covered by a second Hytrel layer, which is added as part of a coextrusion with nylon to obtain greater abrasion resistance. Additional steel layers and a longitudinally formed copper tape are added, and the whole structure is then enclosed in a polyethylene jacket. 

Polymer structure and formulation. As an example, Woo et al. [7] measured OIT values for series of commercial PVC resins and polyester thermoplastic elastomers (TPEs). The researchers used the ASTM D3895-80 procedure, but substituted air as the oxidising gas instead of pure oxygen. A dependency on thermal processing history of the TPE film samples appeared to influence the measured OIT in the PVC study, chemically different chain ends affected polymer stability and hence OIT values. 

Thermoplastic elastomers (TPE s) are characterized by the exceptional property that, without vulcanization, they behave as cross-linked rubbers. They are block-copolymers, in which blocks of the same nature assemble in hard domains, acting as cross-links between the rubbery parts of the chain. These hard domains lose their function when they reach their softening temperature, so that the material can then be processed as a thermoplast. One of the oldest member of the family of TPE s is SBS (styrene-butadiene-styrene block copolymer), but several other TPE s have been developed, i.a. on the basis of polyesters, polyurethanes and polyolefins. In their properties these polymers cover a broad range between conventional rubbers and soft thermoplastics. 

The first commercial thermoplastic elastomers (TPE) were the thermoplastic urethanes (TPU). Their general structure is A-B-A-B, where A represents a hard crystalline block derived by chain extension of a diisocyanate with a glycol. The soft block is represented by B and can be derived from either a polyester or a polyether. Figure 5.1 shows typical TPU structures, both polyester and polyether types. 

Apec KU 1-9320 f[Bayer AG http //WWW. bayer-ag. de, http //www. bayer. com] Polyester elastomer, thermoplastic Synonyms COPE Copolyester elastomer thermoplastic Copolyester, thermoplastic elastomer TPE-E... 

TPCP. See Tri-p-tolyl phosphate TPE-E. See Polyester elastomer, thermoplastic TPG. See Triphenylguanidine Tripropylene glycol... 

In these polyester TPEs, the hard polyester segments can crystallize, giving the polymer some of the attributes of semicrystalhne thermoplastics, most particularly better solvent resistance than ordinary rubbers, and also better heat resistance. Above the melting temperature of the crystalhne regions, these TPEs can have low viscosity and can be molded easily in thin sections and complex stmctures. Properties of thermoplastic polyester elastomers can be fine-tuned over a range by altering the ratio of hard to soft segments. 

Figure 8.56 Typical stress vs. strain curves for DSM Arnitel EM400 and Arnitel EM550 TPE thermoplastic polyester elastomer resins [8].

Thermoplastic elastomers TPEs Styrene-Butadiene, Ethylene Polymers, Polyesters Urethanes, Olefinic Elastomers Various parts not to be operated at temperatures over 120-140°F (except polyester, 3(X)°F) Thermoplastics, injection moldable at production rates. Used for high production of light-colored or transparent parts. Polyesters for high-strength harder parts, urethanes for abrasion resistance... 

The great majority of thermoplastic elastomers (TPE) are copolymers associating soft and hard blocks, such as polyamide- -polyethers, poly urethane-6-polyethers, or polyether-6-polyesters. However, polymers with less classical structures, such as liquid crystalline copolymers or block copolymers based on supramolecular segments, are the subject of extensive research and will probably be commercialized in the near future. 

Dimerized fatty acids (DFA) can be used as an alternative to polyether segments in TPE. The polyester elastomers based on DFA were first prepared by Hoeschele [42]. The properties affecting the degradation stability were improved, but the properties at lower temperatures were unsatisfactory, because the higher glass transition temperature was influenced by the lengths of the amorphous segments. DFA can be coupled with diols and diamines to synthesize telechelic polyesters (Scheme 14) and polyamides, respectively. 

The world demands for thermoplastic elastomers are forecast to expand by 7.5% per year to 2.6 million metric tons in 2006. TPEs will continue to find the majority of their applications as replacements for natural and synthetic rubbers, as well as rigid thermoplastics and metals. The global TPE industry will remain heavily concentrated in the USA, Western Europe and Japan, particularly for specialty materials, such as polyester elastomers. Prom the two trends of application of polyester elastomers as engineering plastics and functional materials, the second one is prioritized. In terms of engineering applications, the PEE production will remain closely related to the motor vehicle industry, sporting goods, hoses, and small household goods. 

Plastics, such as PE, PP, polystyrene (PS), polyester, and nylon, etc., and elastomers such as natural rubber, EPDM, butyl rubber, NR, and styrene butadiene rubber (SBR), etc., are usually used as blend components in making thermoplastic elastomers. Such blends have certain advantages over the other type of TPEs. The desired properties are achieved by suitable elasto-mers/plastic selection and their proportion in the blend. 

Ester TPEs. See Polyester thermoplastic elastomers (ester TPEs)... 

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