Elastomers poly ether-based

Thermoplastic polyurethane elastomers have now been available for many years (and were described in the first edition of this book). The adipate polyester-based materials have outstanding abrasion and tear resistance as well as very good resistance to oils and oxidative degradation. The poly ether-based materials are more noted for their resistance to hydrolysis and fungal attack. Rather specialised polymers based on polycaprolactone (Section 25.11) may be considered as premium grade materials with good all round properties. 

Uses. Approximately 70% of the U.S. production is used to make poly(tetramethylene ether glycol) [25190-06-1] (PTMEG), also known as poly-THE, which is used in the production of urethane elastomers, polyurethane fibers (ether-based spandex), and copolyester—ether elastomers. PTMEG is also the fastest growing use (see PoLYETPiERS, TETRAHYDROFURAn). The remaining production is used as a solvent for the manufacture of poly(vinyl chloride) cements and coating, precision magnetic tape, a reaction solvent in the production of pharmaceuticals, and other miscellaneous uses. 

Kricheldorf H.R., Wollheim T., Koning C.E., Werumeus B.H.G., and Altstadt V. Thermoplastic elastomers 1. Poly(ether-ester-imide)s based on 1,4-diaminobutane, trimeUitic anhydride, 1,4-dihydroxybutane and poly(tetramethylene oxide) diols, Polymer, 42, 6699, 2001. 

Guan JJ et al (2004) Biodegradable poly(ether ester urethane)urea elastomers based on poly(ether ester) triblock copolymers and putrescine synthesis, characterization and cytocompatibility. Biomaterials 25(l) 85-96... 

Polyfester urethanes) based on HER chain extenders behaved in the same way as poly(ether nrethanes). When the high MW diol content of the extender is increased, the storage modulus is decreased due to the reduction of the hard segment content. As was seen from thermal analysis, the thermal stability of the HER-HP extended elastomer is slightly higher than the technical grade materials. 

Figure 5.1.1. Dependence for equilibrium swelling of crosslinked elastomer on the base of poly ether urethane. [Adapted, by permission, from V.Yu. Senichev in Synthesis and properties of cross-linked polymers and compositions on their basis. Russian Academy of Sciences Publishing, Sverdlovsk,1990, p.l6]...

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... 

Polyester soft segments impart better thermal and oxidative stability, oil and solvent resistance, higher abrasion resistance and strength to elastomers, expecially if they crystallize under stress, but they have lower hydrolytic, acid/base and fungus resistance than poly ether urethanes. Polyether urethanes have generally lower Tg and are better suited for low temperatures than the polyester urethanes. Polypropylene oxide-based soft segments are the least expensive, do not crystallize under any conditions and have excellent flexibility. PTMO-based polyurethanes have superior characteristics and an excellent balance of properties. 

A particularly useful method of formulating polyurethane elastomers based on poly(propylene oxide) diols uses a prepolymer of a diisocyanate and the diol. The prepolymer poly ether, usually a poly(propylene oxide) diisocyanate, has a molecular weight of about 1000 to 2000. 

Figure 1. (a) Scheme of a poly(ether ester) thermoplastic elastomer based on PBT (hajd block) and P04 (soft block) (b) scheme of a poly(ester ether carbonate) terpolymer based on PBT, P04, and aliphatic polycarbonate... 

Detailed information on the synthesis of PEBA is presented in Chapters 2 and 10 and also in [13-16]. However, it is worth mentioning here that commercially available poly (ether- -amide) PEBAX copolymers are synthesized by melt polycondensation of carboxylic acid-terminated amide blocks with poly-(oxyalkylene glycol)s. The polymerization is catalyzed by a metal alkoxide Ti(OR)4 and is carried out at elevated temperatures of ca. 230°C under vacuum. These copolymers are marketed for use in many areas, a few of which include sports equipment, automotive components, applications that require polymers with antistatic properties, and also in biomedical applications, such as tubing and catheter balloons [17]. There is also a growing body of literature on the use of PEBAX in the manufacture of membranes for gas separations. Vestamid E-Series elastomers marketed by Degussa-Htils are another commercial example of PTMO-PA12 based PEBA copolymers. 

Example 2. Two-Shot Cast Elastomer (Prepolymer Method). Synthesis of polyurethane elastomers via the prepolymer method is challenging and requires especial attention to details and techniques. This example is a relatively easy one, using a low-viscosity, 9.6% NCO MDI-based poly(tetramethylene ether) glycol prepolymer. It is adapted from the Bayer Product Information Bulletin for Baytec ME-090 prepolymer. 

Harris, R.F., M.D. Joseph, C. Davidson, C.D. Deporter, and V.A. Dais. Polyurethane Elastomers Based on Molecular Weight Advanced Poly(Ethylene Ether Carbonate) Diols. Comparison to Commercial Diols. Journal of Applied Polymer Science 41 (1990) 487-507. 

The segmented block copoly(ether ester)s, based on poly(butylene terephthalate) (PBT) and on polyoxytetramethylene (POTM) are typical examples for this class of thermoplastic elastomers . They can be described as random copolyesters of tereph-thalic acid with 1,4-butanediol and a-hydro-hard phase whereas the remaining ester segments mix with the ether segments and build up the soft matrix. 

More recently, iodonium salts have been widely used as photoinitiators in the polymerization studies of various monomeric precursors, such as copolymerization of butyl vinyl ether and methyl methacrylate by combination of radical and radical promoted cationic mechanisms [22], thermal and photopolymerization of divinyl ethers [23], photopolymerization of vinyl ether networks using an iodonium initiator [24,25], dual photo- and thermally-initiated cationic polymerization of epoxy monomers [26], preparation and properties of elastomers based on a cycloaliphatic diepoxide and poly(tetrahydrofuran) [27], photoinduced crosslinking of divinyl ethers [28], cationic photopolymerization of l,2-epoxy-6-(9-carbazolyl)-4-oxahexane [29], preparation of interpenetrating polymer network hydrogels based on 2-hydroxyethyl methacrylate and N-vinyl-2-pyrrolidone [30], photopolymerization of unsaturated cyclic ethers [31] and many other works. 

We have prepared novel polyurethane elastomers with modified soft segment chemistry that has been designed to enhance stability. The new tliermoplastic polyurethanes are based on conventional diisocyanates and chain extenders, but contain macrodiols with a reduced number of ether linkages when compared with PTMO. As part of the development process, improved synthetic procedures involving condensation polymerization were devised (8,9) to prepare the macrodiols, poly(hexamethylene oxide) 1, poly(octamethylene oxide) 2, and poly(decamethylene oxide) 3. 

Other polymers which have been the subject of thermal degradation studies include ethylene-vinyl acetate [29, 66, 67], ethylene-vinyl alcohol [68], poly(aryl-ether ketone) [69], poly-2-vinyl-naphthalene-co-methyl maleate [34], polyphenylenes based on diethyl-benzophenone [70], polyglycollide [71-73], poly(a-methylstyrene tricarbonyl chromium [74], polytetrahydrofuran [75], polylactide [76-78], poly(vinyl) cyclohexane [79], styrene-vinyl cyclohexane [80], isopropenylacetate-maleic dianhydride [80], polyethylene glycol containing a 1,3-disubstituted phenolic group [81], poly-2-vinyl naphthalene-co-methacrylate [34], collagen biopolymers [82], chitin graft poly (2-methyl-oxazoline - polyvinyl chloride blends [83], cellulose [32, 83-88] and side-chain cholestric elastomers [89, 90]. 

Applications.—Reviews on the applications of polyesters in diverse fields have appeared with weathering performance of reinforced polyesters in building, water-soluble polyester resins with a polyfunctional aromatic acid base, poly(ester-ether) block copolymers - a new type of thermoplastic elastomer, improved polyester radial tyre yam with potential material, pollution, and energy saving,and a thermoplastic polyester review. ... 

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