Segment polyurethane

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

More recentiy, melt-spun biconstituent sheath—core elastic fibers have been commercialized. They normally consist of a hard fiber sheath (polyamide or polyester) along with a segmented polyurethane core polymer (11,12). Kanebo Ltd. in Japan currentiy produces a biconstituent fiber for hosiery end uses called Sideria. 

In the second step, a papermaking method is also used for the fine fibers, less than 0.1 tex (1 den). This process is usually followed by a high pressure water jet process instead of the third step. In the fourth step, to obtain the required properties in specific appHcations, a polyurethane is selected out of the segmented polyurethanes, which comprises a polymer diol, a diisocyanate, and a chain extender (see Urethane polymers). A DMF—water bath for coagulation is also controlled to create the adequate pore stmcture in combination with fibers. 

One partieular form of thermoplastic polyurethane elastomers is the elastic fibre known as spandex fibre. Like the usual thermoplastic rubbers these materials consist of hard and soft segments but to qualify for the term spandex by the US Federal Trade Commission the polymer used should contain at least 85% of segmented polyurethane. The first commercial material of this type was introduced by Du Pont in 1958 (Lycra). Several other similar materials have since been introduced including Dorlastan (Bayer), Spanzelle (Courtaulds) and Vyrene (US Rubber). 

Figure 3, Reactants used and schematic of segmented polyurethane...

Komfield J.A., Spiess H.W., Nefzger H., Hayen H., and Eisenbach C.D. Deuteron NMR measurement of order and mobility in the hard segments of a model polyurethane, Macromolecules, 24, 4787, 1991. Meltzer A.D., Spiess H.W., Eisenbach C.D., and Hayen H. Motional behaviour within the hard domain of segmented polyurethane A NMR study of a triblock model system. Macromolecules, 25, 993, 1992. 

Ishihara K, Hanyuda H, and Nakabayashi N. Synthesis of phospholipids polymers having a urethane bond in the side chain as coating material on segmented polyurethane and their platelet adhesion resistant properties. Biomaterials, 1995, 16(11), 873-879. 

Ishihara K, Tanaka S, Furukawa N, Kurita K, and Nakabayashi N. Improved blood compatibility of segmented polyurethanes by polymeric additives having phospholipid polar groups. I. Molecular design of polymeric additives and their functions. J Biomed Mater Res, 1996, 32(3), 391-399. 

Petrovic, Z.S. et al. Effect of silica nanoparticles on morphology of segmented polyurethanes. Polymer, 45, 4285, 2004. 

MJ. Berrocal, I.H.A. Badr, D. Gao, and L.G. Bachas, Reducing the thrombogenicity of ion-selective electrode membranes through die use of a silicone-modified segmented polyurethane. Anal. Chem. 73, 5328-5333 (2001). 

These structures are well defined by conducting the polymerization in the presence of appropriate mono- and difunctional reagents. They are of considerable interest for the preparation of segmented block copolymers.24,25 For instance, the fluorinated macrodiols 21 have already been used to prepare an interesting new series of partially fluorinated segmented polyurethanes,26 and we are investigating other novel polymers that can be prepared from these intermediates. 

Segmented orifice plates, 77 657-658 Segmented polyurethanes, as biomaterials, 23 722... 

A segmented polyurethane eonsisting of poly(oxybutane-l,4-diyl) bloeks joined through junetion units derived from 1,3- and 1,4-phenylene diisocyanate and arranged alternately ... 

Spandex Segmented polyurethane, 85% or more Light, soft, smooth, resistant to body oils, can be stretched often, retain original form, abrasion-resistant Girdles, bras, slacks bathing suits, pillows Lycra... 

Poly(oxytetramethylene), poly(tetrahydrofuran), may assume the state of a viscous oil, a wax, or a crystalline solid (melting range around 55 °C), depending on the molecular weight. Poly(tetrahydrofuran) telechelics prepared with two OH end groups and in molar masses of 500-4000 g/mol are used widely as soft block in segmented polyurethanes and polyesters (see Sect. 3.4.2.1). 

Stepwise addition polymerization is used in the preparation of segmented polyurethanes (compare Sect. 4.2.1), e.g., poly(ester ether) urethanes which also find application in thermoplastic elastomers. Here, both blocks are preformed separately and are linked together by reaction with isocyanates ... 

In segmented polyurethanes as well as in many other block copolymers incompatible polymer segments are combined. This incompatibility of different CRUs means that block copolymers often form multiphase systems (see TEM-... 

Lee and Matsuda modified a segmented polyurethane film with a dithio-carbamate moiety and then initiated the polymerization of (ethylene glycol) methacrylate and N,N-dimethylacrylamide [35]. The resulting films were hy-drophihc and were shown to inhibit adhesion of platelets. Such films could be useful as anti-coagulant substrates for devices implanted in vivo. 

There are several other commercial products containing segmented polyurethane (SPU) such as pellethane or cardiothane. These SPUs are widely recognized to possess notable biomedical properties as materials for artificial heart and intra-aortic balloon pumping (IABP), and also as coating materials for pacemaker-lead insulators (See Sect. 4.1). 

As for the effect of anionic group, there are a number of reports dealing with the antithrombogenic behavior of sulfonate-modified surfaces of segmented polyurethane (SPU). An interesting feature of the adsorptive behavior of fibrinogen on these material surfaces will be discussed in Sect. 4.1. 

As stated in Chapter 1, microdomain-structured surfaces are believed to play an important role in their interactions with cells, proteins, and other biological elements. In this Chapter, the author will discuss biomedical behavior of three types of microdomain-structured materials segmented polyurethanes, A-B-A block copolymers, and polyamine-graft copolymers. 

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