Hytrel Poly elastomer

Hytrel thermoplastic elastomer (/) is composed of m poly(butylene terephthalate) hard segments and n poly(tetramethyleneoxy) terephthalate soft segments. The hard and soft segments are assumed to be random in distribution. The ratio of m/n controls the mectonical properties of the copolymer (2). 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

In Chapters 3 and 11 reference was made to thermoplastic elastomers of the triblock type. The most well known consist of a block of butadiene units joined at each end to a block of styrene units. At room temperature the styrene blocks congregate into glassy domains which act effectively to link the butadiene segments into a rubbery network. Above the Tg of the polystyrene these domains disappear and the polymer begins to flow like a thermoplastic. Because of the relatively low Tg of the short polystyrene blocks such rubbers have very limited heat resistance. Whilst in principle it may be possible to use end-blocks with a higher Tg an alternative approach is to use a block copolymer in which one of the blocks is capable of crystallisation and with a well above room temperature. Using what may be considered to be an extension of the chemical technology of poly(ethylene terephthalate) this approach has led to the availability of thermoplastic polyester elastomers (Hytrel—Du Pont Amitel—Akzo). 

Poly(pivalolactone) 739 Table 25.12 Propenies of Hytrel-type thermoplastic elastomers... 

The Material of the Example. Poly(ether ester) (PEE) materials are thermoplastic elastomers. Fibers made from this class of multiblock copolymers are commercially available as Sympatex . Axle sleeves for automotive applications or gaskets are traded as Arnitel or Hytrel . Polyether blocks form the soft phase (matrix). The polyester forms the hard domains which provide physical cross-linking of the chains. This nanostructure is the reason for the rubbery nature of the material. 

Commercial copoly(ether-ester) elastomers (e.g., Hytrel , DuPont Lomod , GEC) are segmented block copolymers containing a polyether soft segment such as poly(tetramethylene oxide) and a hard segment that is chemically identical to polybutylene terephthalate. When the soft segment is > 50%, these block copolymers exhibit... 

T. Nishi, T. K. Kwei, and T. T. Wang, Physical Properties of Poly (vinyl chloride)-Copolyester Thermoplastic Elastomer Mixtures, /. Appl. Phys. 46, 4157 (1975). PVC/copolyester thermoplastic elastomer thermoplastic IPN. Modified Hytrel materials. 

A newer type of (AB) block copolymer, known as the poly(ether-ester) elastomers and sold as Hytrel , contains alternating blocks of poly(butylene oxide) and butylene terephthalate as the soft and hard blocks, respectively (144-147) ... 

Telechelic macromers have often been used for making block copolymers. Thus the elastomic fibre, spandex (e.g. Lycra), is made from poly-THF, H(0(CH2)4) 0H, with a diisocyanate (to form a urethane), and the thermoplastic elastomer, Hytrel, is composed of blocks of poly-THF and terephthalic esters. Non-ionic surfactants are often block copolymers of polyethylene oxide/polypropylene oxide (prepared by anionic polymerization). 

Because of its rapid crystallization, PBT is very suitable for use as crystallizable segment in multiblock copolymers, which belong to the class of thermoplastic polyester elastomers (TPEEs). PBT-based block copolymers have been synthesized and studied in detail in the last thirty years. The commercial PBT block copolymers mostly possess a polyether, e.g. poly(tetramethylene oxide) (PTMO), or aliphatic polyester amorphous phase. Thermoplastic poly(ester-ether) elastomers, based on PBT and PTMO were developed by DuPont, and commercially introduced on the market in 1972, under the trade name Hytrel . Extensive investigations on the synthesis of block copolymers based on PBT rigid (hard) segments and various new... 

Poly(ether-ester) (PEE) copolymers obtained by modification of poly(ethyl-ene terephthalate) with up to 20 wt% of poly(ethylene ether) glycol was first described by Coleman [8]. Subsequently, the DuPont Co. developed poly(ether-ester) elastomers, which were commercially introduced in 1972 under the trade name Hytrel [4,9]. The polyester thermoplastic elastomers are nowadays produced by several companies. Apart from DuPont, these are DSM, The Netherlands (Arnitel ), General Electric, USA (homed ), Hoechst Celanese, USA (Retiflex ), Toyobo, Japan (Pelprene ), Elana, Poland (Elitel ) [2,10]. The synthesis, chemical structure, physical properties, and some new applications of polyester TPE are discussed in this chapter (about the development of TPE, see also Chapter 1, while details on some commercial TPE products can be found in Chapter 17). 

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