Polyurethane stretchable

Several different kinds of polyurethanes are produced, depending on the nature of the polymeric alcohol used. One major use of polyurethane is in the stretchable spandex fibers used for bathing suits and leotards. These polyurethanes have a fairly low degree of cross-linking so that the resultant polymer is soft and elastic. A second major use of polyurethanes is in the foams used for insulation. Foaming occurs when a small amount of water is added during polymerization, giving a carbamic acid intermediate that spontaneously loses bubbles of COj. 

Li, M., Li, H., Zhong, W., Zhao, Q., Wang, D., 2014. Stretchable conductive polypyrrole/polyurethane (PPy/ PU) strain sensor with netlike microcracks for human breath detection. ACS Appl. Mater. Interfaces 6,... 

Leather must resist tearing, be stretchable, porous to moisture and air, and be capable of taking a surface texture and forming according to the requirements of fashion. Raw material scarcities and the work-intensive nature of natural leather preparation has led to a search for a synthetic leather over the last few decades. The well-known synthetic leathers consisting of fabrics covered with polyamides, polyurethanes, or poly(vinyl chloride) have been available for a long time. But these synthetic leathers cannot replace natural leather in all its applications, since the permeability and the feel of these materials are inferior. 

Polyurethanes have a wide range of applications. Polymers with relatively little cross-linking produce stretchable fibers (Spandex and Lycra) used for bathing suits. Polyurethane foams are used in furniture, mattresses, and car seats and as insulation in portable ice chests. Cross-linked polyurethanes form very tough surface coatings in paints and varnishes. The major component of the Jarvik-7 artificial heart is also a polyurethane. 

Hansen, T.S., et al. Highly stretchable and conductive polymer material made ftom poly(3,4-ethyl-enedioxythiophene) and polyurethane elastomers. Adv. Funct. Mater. 17(16), 3069-3073 (2007)... 

Figure 3 (A) Illustration of the fabrication of a highly compressible and stretchable superhydrophobic coating on polyurethane sponge through layer-by-layer deposition. (B) SEM images of the superhydrophobic coating after compression for (a) 1000 cycles, (b) 2000 cycles, (c) 3000 cycles, and (d) 4000 cycles. Reproduced from Liu etal. (2014) by permission of The Royal Society of Chemistry.

Polyurethanes are extremely versatile polymeric materials due to their elasticity, responsive nature toward impact, stretchability, and other possible physical manipulations. They have been utilized in various fields to make optical devices, adhesives, coatings, and also in many biomedical applications. Thiol-isocyanate click reactions have been used to generate polythiourethanes, a sulfur analog of polyurethane, in a very efficient way and in high yields [50]. 

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