Polyurethanes elastoplastic

Fig. 10. Internal energy changes as a function of deformation for oriented LDPE (I) and stress softened thermo-elastoplastic polyurethanes with 50% (2) and 42 % (3) hard phase content and polyether-polyester block copolymer with 48% hard phase content (4). The dotted curves 1 and 2 represent intramolecular energy changes for the corresponding polymers119 ...

This TPE has been described as an aromatic elastoplastic polyurethane alloy. It possesses a low coefficient of friction, low extractables, and dimensional stability. Hardness ranges from 65 to 75 Shore D. The material is classified for short-term (29 days or less) implantation. Clear and radiopaque formulations are available. Tubing should be annealed at 80°C for four hours to reduce crystallinity (Tables 4.3, 4.4, 4.12, and 4.14). 

IonomerM Polyurethane[Pg.44]

Block copolymers were developed rapidly in the 1960s when living anionic polymerization was first utilized to synthesize triblock thermoplastic elastomers or elastoplastics. At the same time, step or condensation polymerization to produce thermoplastic polyurethanes, urea-urethane spandex fibers, and later more specialized materials, such as the semicrystalline polyester-polyether copolymers were developed [10]. Imide block or segmented copolymers utilizing... 

Going up somewhat in hard segment content to the 50-60% range affords ( at least in polyurethane or urea-urethane RIM) the elastomers and elastoplastics, or perhaps a better word than elastoplastics would be toughened plastics. 

Thermoplastic polyurethanes (TPU) are a versatile family of elastoplastic materials characterized by outstanding toughness and abrasion resistance. These materials are prepared from three principal reactants, a difunctional polyol, a difunctional chain extender and a diisocyanate in accordance with the following reaction ... 

Telechelic polyTHF oligodiols (DuPont, BASF, Quacker Chem.) have found important applications, mostly as soft segments in multiblock elastoplastic materials such as polyurethanes (e.g. Spandex ) and polyesters (Hytrel ). 

Hence, the results obtained above have shown that behaviour at deformation for the considered polyurethanes and nanocomposites on its basis is described within the frameworks of entropic high-elasticity fractal theory or, equivalently, within the frameworks of the classical theory approximation for long polymer chains. The considered polymer networks obey Ganssian statistics due to their preparation method. The inaccuracy of the application of the entropic high-elasticity classical theory (Equation 7.13) is defined by non-fnlfilment in the given case of a postulate about elastoplastics incompressibility [49]. 

---